Chlamydia pneumoniae infections in mouse models

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Review

Chlamydia pneumoniae infections in mouse models:

relevance for atherosclerosis research

Martijn D. de Kruif a,b,*, Eric C.M. van Gorpa,b, Tymen T. Kellera,

Jacobus M. Ossewaardec, Hugo ten Catea,d

aLaboratory of Experimental Internal Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The NetherlandsbDepartment of Internal Medicine, Slotervaart Hospital, Amsterdam, The Netherlands

cDepartment of Medical Microbiology and Infectious Diseases, Erasmus Medical Center, Erasmus University, Rotterdam, The NetherlandsdDepartment of Internal Medicine, Academic Hospital Maastricht, University Maastricht, Maastricht, The Netherlands

Received 28 July 2004; received in revised form 20 September 2004; accepted 29 September 2004

Available online 22 October 2004

Time for primary review 26 days

ic.oup.com/cardiovascres/article/65/2/317/306499 by guest on 30

Abstract

Mouse models have been frequently used in the study of Chlamydia pneumoniae (also known as Chlamydophila pneumoniae) infections.

This gram-negative obligate intracellular bacterium causes respiratory infections, followed by dissemination of the bacterium to various

organs throughout the body, including cardiovascular tissues, supporting the current hypothesis of a relationship between C. pneumoniae and

atherosclerosis. Recently, clinical trials evaluated the effect of antichlamydial antibiotics on secondary cardiovascular events. Although small

studies showed some effect, the large WIZARD study did not confirm these results, and the role of antichlamydial antibiotics in prevention of

secondary events was questioned. To address these issues, data obtained from mouse models were systematically reviewed here. C.

pneumoniae infections showed atherogenic properties in mice that were reproducible and confirmed by different research groups. However,

antibiotic therapy was of limited value in these mouse models. Antibiotic therapy effectively cleared the acute infection, but did not influence

the atherogenic properties of C. pneumoniae unless the therapy was started early during the acute infection. The results summarized here may

help to better understand the results of the clinical antibiotic trials.

D 2004 European Society of Cardiology. Published by Elsevier B.V. All rights reserved.

Keywords: Chlamydia pneumoniae; Chlamydia psittaci strain TWAR; Chlamydophila pneumoniae; Mouse models; Mice; Cardiovascular diseases;

Atherosclerosis; Antibiotics

May 2022

1. Introduction

Atherosclerosis is considered an inflammatory disease

[1]. The precise trigger for inflammation is not known, but

several infectious organisms have been suggested to play a

role in this process [2]. The most prominent of these

organisms is the gram-negative, obligate intracellular

bacterium Chlamydia (C.) pneumoniae (officially known

0008-6363/$ - see front matter D 2004 European Society of Cardiology. Publishe

doi:10.1016/j.cardiores.2004.09.031

* Corresponding author. Laboratory of Experimental Internal Medi-

cine, G2-132, Academic Medical Center, University of Amsterdam,

Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands. Tel.: +31 20

5667906; fax: +31 20 697 7192.

E-mail address: [email protected] (M.D. de Kruif).

as Chlamydophila pneumoniae [3], but more commonly

called Chlamydia pneumoniae). C. pneumoniae enters the

body as a respiratory pathogen, and causes infections in a

wide range of severity, from asymptomatic disease to severe

pneumonia [4,5]. The acute infection is sometimes followed

by a prolonged period of malaise and coughing, suggesting

a chronic reaction to the organism [4,6]. Notably, the effects

of C. pneumoniae infection are not limited to the respiratory

tract. Cases of myocarditis and endocarditis due to C.

pneumoniae have been described [7,8]. In addition, C.

pneumoniae infection has been associated with chronic

diseases, including atherosclerosis, asthma, arthritis, hyper-

tension and multiple sclerosis in merely epidemiologic

studies [4,5,9].

65 (2005) 317–327

d by Elsevier B.V. All rights reserved.

Table 1

Methods in studies using mouse models for the study of C. pneumoniae infection

Authors Year Mouse strain Clpn strain Dose�106 IFUa Inoculation

(week)bMultiple

inoculationscInterval

(week)

Reinfection

(week postinfection)dFollow-up

(week)eMain topic

Kishimoto [30] ’90 ICR TW-183 – 6–7 – – – 3 Course of infection

Yang et al. [32] ’93 Swiss Webster, Icr, BALB/c C,

C57Bl/6, C3H/HeN, B6C3F1

AR-39 30 4–5 – – 10, 14 2/7 15 2/7 Course of infection

Kaukoranta-Tolvanen

et al. [31]

’93 NIHS, Swiss Webster, BALB/c K 6, H12, TW-183 0.2–2 6–8 – – – 6 Course of infection

Kimura [44] ’94 ICR TW-183 – 6–7 – – 5 3 Course of infection

Nakata et al. [45] ’94 MCH-ICR K 6, IOL-207 0.0001–0.1 – – – – 3 Antibiotics

Kaukoranta-Tolvanen

et al. [46]

’95 NIHS K 6 1 6–8 – – 4, 10 14 Course of infection

Yang et al. [47] ’95 Swiss Webster AR-39 30 4–5 – – – 1 4/7 Course of infection

Malinverni et al. [48] ’95 Swiss Webster AR 388, AR-39 1.5–13 4 – – – 14 4/7 Antibiotics

Masson et al. [49] ’95 MF1, NIHS, BALB/c, C3H/He TW-183 0.0017–0.045 4–6 – – – 4 1/7 Antibiotics

Malinverni et al. [50] ’95 Swiss Webster AR-39 1.5 4 – – – 5 4/7 Course of infection

Laitinen et al. [51] ’96 NIHS K 6 1 6 – – – 6 2/7 Course of infection

Peterson et al. [37] ’96 BALB/c, C57Bl/6 TW-183 10 6 – – – 9 4/7 Immunology

Moazed et al. [42] ’96 Apo E, C57Bl/6 AR-39 30 8 3� 2 – 4 Course of infection

Moazed et al. [38] ’98 C57Bl/6 AR-39 30 6–8 – – – 1 Course of infection

Penttila et al. [52] ’98 BALB/c K 6 1 6–8 – – 4–8 16 6/7 Course of infection

Penttila et al. [53] ’98 BALB/c, NIHS, C57Bl/6 K 6 1–1.5 6–7 – – 6 12 Immunology

Penttila et al. [54] ’98 BALB/c, nude K 6 1–10 6–8 – – 5–8 10 5/7 Immunology

Peterson et al. [55] ’98 Swiss Webster AR-39 0.002–20 4–6 – – – 5/7 Immunology

Rottenberg et al. [56] ’99 Multiple KO mice K 6 1 6–10 – – – 8 4/7 Immunology

Wolf and

Malinverni [57]

’99 NMRI AR-39 50 3–4 – – – 2 6/7 Antibiotics

Hu et al. [16] ’99 LDL R�/� AR-39 5–10 4–5 9� 4 – 43 4/7 Atherosclerosis

Moazed et al. [17] ’99 Apo E �/� AR-39 30 8 3� 1 – 10 Atherosclerosis

Blessing et al. [43] ’00 C57Bl/6 AR-39 30 8 3� 1 – 20 Atherosclerosis

Liu et al. [18] ’00 LDL R�/� AR-39 5–10 4–5 12� 2 – 23 4/7 Atherosclerosis

Liuba et al. [58] ’00 Apo E �/�, C57Bl/6 IOL-207 0.4 8 4� 2 – 10 Atherosclerosis

Vuola et al. [59] ’00 C57Bl/6, BALB/c K 6 1 6–8 – – 4 5/7, 9 10 5/7 Immunology

Geng et al. [60] ’00 BALB/c, 129sv, IFN-y R�/� TW-183 0.03 6–8 – – – 2 2/7 Immunology

Rottenberg et al. [61] ’00 Multiple KO micef K 6 1 6–10 – – – 8 4/7 Immunology

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Pal et al. [62] ’00 129 sv, Nramp1�/� TW-183 0.1 7–9 – – – 1 3/7 Immunology

Erkkila et al. [41] ’00 NIHS, C57Bl/6 K 6, K 7 1.2 –1.8 6–8 – – – 3 Techniques

Meijer et al. [63] ’00 C57Bl/6 AR-39 1–430 4–6 – – – 3 Techniques

Svanholm et al. [64] ’00 Multiple KO micef K 6 1 10–14 – – – 1 Immunology

Murdin et al. [65] ’00 BALB/c AR-39 0.05–0.5 – – – – 3 1/7 Immunology

Bin et al. [66] ’00 NMRI AR-39 50 4 – – – 9 Antibiotics

Rothstein et al. [21] ’01 Apo E �/� A-03 5 10 2� 2 – 14 Antibiotics

Penttil7 et al. [67] ’01 BALB/c K 6 1 11–13 – – – 1 3/7 Immunology


Aalto-Set7l7 et al. [68] ’01 Apo E �/� K 7 0.1–3 8 4� 3–4 – 18 Atherosclerosis

Caligiuri et al. [69] ’01 Apo E �/�, C57Bl/6 K 6 1 6–8 – – 18 22 Atherosclerosis

Burian et al. [70] ’01 BALB/c – 0.02–0.04 6–8 3� – – 7 Atherosclerosis

Burnett et al. [20] ’01 Apo E �/� – – 6 2� 2 – 10 Atherosclerosis


Ezzahiri et al. [39] ’02 Apo E3-Leiden �/� TWAR 2043 60 9 2� 2 9, 32 36 Atherosclerosis

Erkkila et al. [72] ’02 NIHS K 6 1 6–8 – – 4 2/7 8 4/7 Techniques

Tiirola et al. [73] ’02 NIHS K 7 0.5 8–9 – – – 2 6/7 Lipids

Bandholtz et al. [74] ’02 Multiple KO micef K 6 1 6–10 – – – 3 Immunology

Airaksinen et al. [75] ’03 BALB/c K 6 1 6–8 – – 8 9 3/7 Immunology

Burian et al. [76] ’03 BALB/c, HDC �/�, CD1 TW-183 1 6–8 – – – 4 3/7 Immunology

Shi et al. [77] ’03 ICR CWL-029 7–9.7 8 – – – 8 4/7 Course of infection

Ezzahiri et al. [40] ’03 Apo E �/� and LDL R �/� TWAR 2043 5–50 16 6� 4 – 24 Atherosclerosis

Liuba et al. [78] ’03 Apo E �/� IOL-207 0.2 7 3x 2 – 10 Atherosclerosis

Chesebro et al. [22] ’03 C57BL/6, iNOS�/�, eNOS�/� AR-39 24 8 3� 2 – 18 Atherosclerosis

Rothfuchs et al. [79] ’04 Multiple KO micef K 6 1 6–10 – – – 3 4/7 Immunology

Mygind et al. [80] ’04 C57BL/6 VR 1310 0.25–2 – – – – 12 Immunology

Little et al. [81] ’04 C57BL/6 96-41 0.02–0.04 12 – – – 12 Amyloid depositions

Tfrm7kangas et al. [82] ’04 C57BL/6 K 7 0.6 8 – – – 3 Antibiotics

a IFUs: inclusion forming units.b Inoculation: age of mice during first inoculation.c Multiple inoculations: subsequent infections aimed at increasing the chance of establishing a chronic infection; number of inoculations and intervals in weeks.d Reinfection: occasional extra inoculation.e Follow-up: total duration of main experiment in weeks after first infection.f Multiple KO mice: multiple gene knockout mouse strains (C57BL/6 background).

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A serologic relationship of C. pneumoniae infection with

atherosclerosis was first demonstrated in 1988 [10]. Saikku

et al. showed that patients with coronary artery disease had

elevated antibody titers against C. pneumoniae. Although

this serologic relationship has been disputed [11], it

stimulated further research. In atheromatous tissues from

human vessels, C. pneumoniae was detected by several in

situ methods [12,13]. In vitro data suggested a role for

chlamydial heat shock protein 60 (cHSP60) in oxidation of

low-density lipoproteins and a role for chlamydial lip-

opolysaccharide (LPS) in foam cell formation [14,15]. In

mice, atherosclerotic lesion development was accelerated by

C. pneumoniae infection, and reactive infiltration of inflam-

matory cells in intimal plaques was demonstrated [16–22]. In

rabbits, acceleration of lesion development by C. pneumo-

niae could be inhibited by antibiotics after infection [23].

This accumulating evidence for a relationship between C.

pneumoniae and atherosclerosis led to the hypothesis that

antibiotic therapy might influence the course of cardiovas-

cular disease [24]. Initially, a number of small studies

showed some beneficial effects of antichlamydial antibiotics

in the outcomes of various cardiovascular complications,

including myocardial infarction and angina pectoris [25].

However, the WIZARD study, a recently published large

randomized trial that included 7747 patients with previous

myocardial infarction and elevated C. pneumoniae titers,

showed no beneficial effects of a 3-month course of

azithromycin on secondary cardiac events after a median

follow-up of 14 months [26]. Two other large trials, ACES

and PROVE IT [27,28], were recently preliminary presented

at the European society of cardiologists congress 2004,

which was held in Munich, Germany, from August 28 to

September 1st, 2004, and showed similar negative results.

The negative results of these studies prompted a lot of

questions, related to the pathogenetic involvement of C.

pneumoniae in cardiovascular disease, on the one hand, and

its susceptibility to antibiotic treatment on the other hand

[29]. Many of these questions can be discussed on the basis

of studies that have been performed in mouse models, which

have been the predominant models for studying athero-

genesis during the past several years. Here, we present a

systematic overview of C. pneumoniae research in mice,

emphasizing its relationship with atherosclerosis.

2. Methods

Citations were retrieved from Pub Med and MEDLINE

databases. Using the single terms bChlamydophila pneumo-

niaeQ, bChlamydia pneumoniaeQ and bChlamydia psittaci

strain TWARQ, and combinations of these terms with

bmouseQ or bmiceQ, or batherosclerosisQ, or bantibioticsQ,titles, abstracts and references were scanned for the use of

mouse models in C. pneumoniae research. A total of 56

articles using mouse models was retrieved, from 1990 to

2004.

3. Mouse models: general aspects

The first mouse models for C. pneumoniae infection

were developed in the beginning of the 1990s, when

evidence became clear that C. pneumoniae was a major

respiratory pathogen [30–32]. The models used several

mouse strains that differed in susceptibility to infection.

Swiss Webster mice and NIH/S mice were highly suscep-

tible, followed by C57BL/6 mice, whereas BALB/c mice

were least susceptible [31,32]. In addition, C. pneumoniae

strains differed in virulence, although they are known to

show very little genetic diversity [33]. For each strain, a

specific dose was established (Table 1). The most widely

used C. pneumoniae strain was AR-39, a strain originally

isolated from a patient’s throat swab in 1983 and known to

be host to a bacteriophage with possible pathogenic

properties [34,35]. Other commonly used strains were

TW-183, which was the first C. pneumoniae isolate and

was isolated from a trachoma patient in Taiwan in 1965 and

was propagated afterwards for a long time in a yolk sac [5],

and Kajaani 6, which was isolated from pharyngeal swabs in

an epidemic of C. pneumoniae infections in military

conscripts in 1987 [36].

The mice were inoculated intranasally by droplets of

0.5 ml administered onto the nostrils, or sometimes

intraperitoneally, when the respiratory tract infection was

not the main focus of attention [22,37–40]. Anesthetics

used during inoculation differed greatly. One study showed

methoxyflurane anesthesia to be superior to CO2 anes-

thesia, resulting in more homogeneously infected animals

[41]. In some models, multiple inoculations were intro-

duced in order to mimic chronic infection; generally 2–4

intranasal inoculations were given at 1- to 2-week intervals

[42].

Under normal conditions, mice do not develop athero-

sclerosis. However, wild-type C57BL/6 mice can develop

early atherosclerotic lesions in the aortic root when they are

being fed an atherogenic diet [43]. Several genetically

modified mouse strains, mostly with a C57BL/6 back-

ground, were used, such as LDL receptor knockout mice

and Apo E3 Leiden transgenic mice [16,39]. These mice are

more prone to develop atherosclerosis than wild-type mice

but still need to be fed an atherogenic diet. Apo E knockout

mice do not need a special diet. They are characterized by

disturbed LDL uptake by the liver and develop atheroscle-

rosis spontaneously from the first stage of macrophage

adhesions at the age of 10 weeks to the development of

mature atheromas at 24 weeks [42].

4. Course of infection

Infection of mice with C. pneumoniae resulted in a self-

limiting pneumonia [30–32,77]. Depending on the dose

given, mice displayed symptoms, like dyspnea, weakness

and weight loss. The symptoms reached a maximum within

Fig. 1. Immunological reaction to C. pneumoniae infection. The innate

immunity, represented by polymorphonuclear cells and macrophages, plays

an important role in the first days of infection. Subsequently, CD8+T

lymphocytes are predominant, mainly by stimulating the powerful

antichlamydial cytokine IFN-g. Antibody production by B lymphocytes

plays a minor role (see also text). Abbreviations: PMN=polymorphonuclear

cell, MB=macrophage, CP-IB=C. pneumoniae inclusion body (intracellu-

lar), CP-EB=C. pneumoniae elementary body (extracellular).

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2 to 4 days and rarely lasted longer than 1 week.

Histological examination revealed peribronchial and peri-

vascular inflammation, with exudates in bronchi and alveoli

in severe cases [32,59,77]. Proliferation of lymphoid tissue

and peribronchial fibrosis was observed after 1–2 weeks

[31,32,46,63]. The infiltrates consisted of polymorphonu-

clear cells in the first days, which were gradually replaced

by mononuclear cells within two weeks. At 3–6 weeks, no

lesions were left in the lungs [31,32,42,49,77].

Isolation of viable C. pneumoniae organisms from the

lungs was generally possible up to 4 weeks after infection and

occasionally up to 6 weeks [31,32,42,47,49,52,54,66,72].

However, C. pneumoniae antigens and DNA were detected

in the lungs for a much longer period, up to 20 weeks after

infection [42]. The presence of C. pneumoniae antigens in

the lungs was limited to macrophages in alveoli and

bronchus-associated lymphoid tissue [63]. These findings

suggested a latent persistence of the organisms, which was

confirmed by reactivation of pulmonary infection using

cortisone-induced immunosuppression experiments [50,51].

When mice were administered multiple inoculations, the

histopathological changes lasted much longer, up to 16

weeks [42]. In reinfection experiments, a partial immunity

developed, since less organisms were isolated [32,44,46,52].

Despite this clinical improvement, histopathological

changes were similar to those in primary infection, except

for a more pronounced lymphoid reaction indicative of

induced immunological memory [46,52].

C. pneumoniae infection was not limited to the respira-

tory tract only. Following local infection, spreading of C.

pneumoniae to multiple organs throughout the body was

detected by PCR and immunohistochemical staining up to

20 weeks [42]. The dissemination was probably mediated

by peripheral blood monocytes as they were positive both

by PCR and isolation in some studies, whereas blood

plasma was negative [38,47]. Transiently raised levels of

triglycerides were found in three studies [21,68,73], but

three other studies reported to have found no differences in

lipid levels [16,18,19].

30 May 2022

5. Immunological reaction

Like other chlamydiae, C. pneumoniae challenges the

host defense mechanisms in a complicated manner [83]. The

intracellular location of the bacterium provides relative

protection against the immune system. The bacterium

probably hides from detection by down-regulating process-

ing and presentation of its own antigens [84,85] and the

bacterium is able to prevent spontaneous apoptosis of its

host cell [86,87].

The immunological reaction to C. pneumoniae infection

in mice proceeded in two stages, a nonspecific reaction of

the innate immune system followed by a specific reaction a

few days later. In the specific reaction, CD8+ T lympho-

cytes played a major role [54,56] (see Fig. 1). The function

of these cells was essential for resolution of the infection,

although in C. pneumoniae infection, they did not act as

perforin mediated cytolytic cells, since mice lacking

perforin did not show more severe infection [56]. Probably,

the function of CD8+ cells was mediated by their ability to

release cytokines, thus stimulating a Th1 response and

inhibiting a Th2 response. In addition, the CD8+ cells were

important for C. pneumoniae specific memory [54]. In

contrast to the CD8+ cells, CD4+ cells contributed to

protection only in the later stages of infection. In the first

weeks, CD4+ cells even played a potentially harmful role

[54,56].

The cytokine release was characterized by a Th1-type

response with elevated levels of IFN- g, TNFa, IL-12 and

IL-10 and unaltered IL4 levels [60]. The most important

cytokine was IFN-g, both in specific and in nonspecific

immunity [59]. IFN-g stimulated several antibacterial

mechanisms, including stimulation of inducible nitric oxide


oxidase, and stimulated IL-12, which in turn stimulated

IFN-g [56,61].

Antibody production played only a minor role in the

neutralization of C. pneumoniae infection [56]. C. pneumo-

niae specific IgG titers started to rise from 10 to 12 days

after infection, reaching a maximum at 4 weeks and

gradually disappearing by 16 weeks [31,32,42,72]. IgM

production started from 1 week after infection, reaching a

maximum in 2–3 weeks, and gradually subsided until 6

weeks [30,31,43].

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6. Antichlamydial strategies

A few short-termed antibiotic trials were conducted in

mouse models. There were no apparent differences found

among doxycycline, azithromycin, erythromycin, amoxicil-

lin-clavunalate, telithromycin and ciprofloxacin treatments,

as they were all efficacious in clearing the active infection

within 2 weeks [48,49,82]. Sparfloxacin was superior to

clarithromycin, tosufloxacin, ofloxacin and minocycline in a

model of leukopenic mice [45]. A combination of azithro-

mycin and rifampin treated the infection better than

amoxyciline or azithromycin treatment alone [57,66]. After

therapy, C. pneumoniae DNA could still be detected by

PCR, but viable bacteria could not be isolated from the

tissues, which suggested the persistence of nonviable or

nonreplicating bacteria [48,82].

A vaccine should theoretically circumvent the problem of

persisting bacteria [83]. Partially effective immunizations

were reported in C. pneumoniae infection using DNA

vaccines encoding for several C. pneumoniae proteins,

including MOMP, Omp2, Hsp60 and an ADP/ATP translo-

case [37,64,65,67,74,75]. Current research focuses on

Table 2

Effect of C. pneumoniae infection upon atherosclerotic lesions in mice; overview

Author Year Micea Gender Atheroge

diet

Hu et al. [16] ’99 LDL R �/� F +

Moazed et al. [17] ’99 Apo E �/� M �Blessing et al. [43] ’00 C57BL6 M �Liu et al. [18] ’00 LDL R �/� F +

Liuba et al. [58] ’00 Apo E �/�, C57BL6 M/F �Blessing et al. [19] ’01 C57BL6 M +

Aalto-Set7l7 et al. [68] ’01 Apo E �/� M/F FCaligiuri et al. [69] ’01 Apo E �/�, C57BL6 F �Burian et al. [70] ’01 BALBC M �Burnett et al. [20] ’01 Apo E �/� M/F �Rothstein et al. [21] ’01 Apo E �/� F �Blessing et al. [71] ’02 C57BL6 M +

Ezzahiri et al. [39] ’02 Apo E3-Leiden M/F +

Chesebro et al. [22] ’03 iNOS �/�, eNOS �/� M +

Ezzahiri et al. [40] ’03 Apo E �/� LDL R �/� M �Liuba et al. [78] ’03 Apo E �/� M/F �

a Time postinfection: time after first inoculation (weeks). More details aboutb Lesion size acceleration: lesion size of plaques from C. pneumoniae-infectec Plaque composition acceleration: atherosclerotic lesions in a more advan

uninfected mice.

enhancing the power of these proteins as a vaccine by

adding adjuvantia or combining proteins to multisubunit

vaccines, and on several strategies to find new immuno-

reactive proteins.

7. Atherosclerosis

An accelerating effect of C. pneumoniae infection on

atherogenesis was demonstrated in a considerable number of

hyperlipidemic mouse models (Table 2). In wild-type

C57BL/6 mice fed an atherogenic diet, the atherosclerotic

lesions were significantly larger in infected animals [19,22].

Similar findings were found for genetically modified,

hyperlipidemic mice with C57BL/6 backgrounds, such as

Apo E knockout mice, LDL receptor knockout mice and

Apo E3 Leiden transgenic mice [16–18,20,21]. Further-

more, lesions from infected mice represented more

advanced stages of atherosclerosis, showed more unstable

plaque phenotypes and attracted T cell infiltration

[16,39,40]. Antibiotics did not influence lesion acceleration

when administered to mice 2 weeks after the last infection

[21]. In two studies, C. pneumoniae did not influence

atherogenesis [68,69] (see Fig. 2).

The atherogenic properties of C. pneumoniae required

multiple inoculations in all cases, and hyperlipidemia was

essential. When the atherogenic diet was administered to

wild-type mice 2 weeks after infection, no lesion accel-

eration was seen [71]. Infection at times when advanced

atherosclerotic plaques had already formed did not influence

lesion size but resulted in more unstable plaque phenotypes

[40]. Wild-type mice on a normal diet developed temporary

inflammatory lesions in several organs, including the aorta,

heart, spleen and liver [42,43,47,70], but none of the aorta

of studies

nic Time post

infection (week)

Lesion size

accelerationbOther findings

43 4/7 Yes. 1.5� Plaque composition accelerationc

10 Yes. 1.6�20 (No) Inflammatory changes aorta

23 4/7 Yes. 1.3�6 (No) Endothelial dysfunction

16 Yes. 3.3�18 No

22 No

7 (No) Inflammatory changes aorta

10 Yes. 1.7�14 Yes. 1.5� No effect of azithromycine

18 (No) Diet started after infection

36 (No) Plaque composition acceleration

18 Yes. 2.6�24 (No) Reduced fibrous cap area

10 (No) Endothelial dysfunction

the inoculation schedules are given in Table 1.

d mice compared to lesion size from uninfected mice.

ced stage at a certain age in C. pneumoniae-infected mice compared to

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Fig. 2. Scheme summarizing the limitations of antibiotic therapy of C. pneumoniae infection in mice. Antibiotic therapy is effective in clearing the acute active

infection in lungs, but a number of organisms are able to survive in the lungs in a persistent state. Furthermore, inhibition of the pro-atherogenic effects of C.

pneumoniae is only possible when the antibiotics are given early during the infection. It is not clear what the precisemechanism is of the pro-atherogenic properties

of C. pneumoniae in mice, and it is not clear whether antibiotics can affect the presence of C. pneumoniae antigens in atherosclerotic plaques (see also text).


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inflammatory lesions progressed to atherosclerotic lesions

[43,70]. Murine cytomegalovirus infection produced similar

inflammatory lesions, and superinfection with C. pneumo-

niae had an impressive additional effect upon the size of

these lesions [70]. However, no such additional effects were

found in Apo E knockout mice, although each pathogen on

itself accelerated lesion development [20]. Infection with C.

pneumoniae resulted in increased endothelial dysfunction

and enhanced VCAM-1 expression in Apo E knockout

mice, and coinfection with Helicobacter pylori stimulated

these effects [78]. In one study, lesion acceleration was

found in male mice only, which suggested a gender-

dependent effect [20].

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8. Discussion

Mouse models provided detailed information about C.

pneumoniae infections. Many of these details were rather

uncommon to a respiratory tract infection. The histopatho-

logical changes in the lungs were considerable, although the

clinical disease was rather mild [31,32]. The host defense,

characterized by a Th1 response requiring IFN-g for clearing

the bacteria, was only partly successful in controlling the

infection [56]. Afterwards, the C. pneumoniae organisms

persisted in the lungs in a latent phase that could be

reactivated by the administration of cortisone [50,51]. This

phenomenon could be related to the capability of IFN-g to

induce persistence of the bacteria. The addition of IFN-g toC.

pneumoniae-infected monocytic cell lines induced a similar

kind of persistence of nonreplicating, viable bacteria [88].

Another uncommon finding of a respiratory tract

infection is that C. pneumoniae disseminated throughout

the body and caused inflammatory lesions in several organs,

including the heart and the vessel walls [47]. The dissem-

ination was generally mediated by leukocytes, in which C.

pneumoniae has found a way of surviving [38]. Notably,

only during a short period following infection, viable

organisms were isolated from the organ tissues [42]. Also

in human atherosclerotic tissue specimens, isolation of

viable organisms generally was a rare event. In these tissue

specimens, membrane components of C. pneumoniae were

detected by in situ methods, but no inclusions were found

that resembled viable organisms [89]. Probably, viable

organisms were capable of reaching the atheroma, but did

not survive there for long, and left nonviable, potentially

pathogenic remnants behind. It is also possible that C.

pneumoniae persisted in the atheroma in a latent state as had

been found in lung tissue, but no such inclusions were

detected in mice. In either case, antibiotic treatment is of

limited value, because it aims at viable, replicating bacteria.

The presence of C. pneumoniae in the atheroma seems to

be pathogenic. Atherogenesis was accelerated in a number

of mouse models, and the results were reproducible and

confirmed by different research groups (Table 2). At first,

acceleration of atherogenesis was demonstrated in genet-

ically modified mice only [16,17]. These results were

difficult to interpret because the genetic modification in

itself could have influenced the inflammatory process [90].

Additional evidence came from normal C57BL/6 mice fed

an atherogenic diet [19,71]. It became clear that multiple

inoculations and a hyperlipidemic environment were essen-

tial, and some evidence suggested a gender-dependent effect

[43,71]. In two studies, the conclusion was drawn that C.

pneumoniae did not accelerate atherogenesis. In one of

these studies [69], no reinfection after the first inoculation

had been given until 18 weeks after infection, which could

explain the lack of association with atherogenesis, arguing


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that a model of chronic infection is necessary. Furthermore,

these investigators used a lower dose of C. pneumoniae

[91]. In the other study by Aalto-Set7l7 et al. [68], Apo E

knockout mice on an FVB background were used. These

mice are known to develop atherosclerosis more slowly than

Apo E knockout mice on C57BL/6 background, which may

have influenced the findings [92]. The investigators used C.

pneumoniae strain Kajaani 7, which is known to be cleared

quickly [41], so it may not have been able to induce chronic

infection. On the other hand, this strain was very virulent in

acute disease, and many mice died, up to 80% in a group,

leaving 1 to 5 mice in a group. The conclusions drawn from

this study are therefore difficult to interpret.

The atherogenic properties of C. pneumoniae in mice

have also been demonstrated in a few studies in rats, rabbits

and pigs, suggesting that the results of these animal models

can be extrapolated to human beings [93–95]. The

mechanism is not known, but several pathways were

proposed for C. pneumoniae-enhanced atherosclerosis

[96]. These mechanisms include (1) direct stimulation of

monocyte migration to the atheromas [97]; (2) direct

interference with intracellular metabolism within the plaque,

as C. pneumoniae was able to infect all cell types present in

a plaque in vitro, thereby inducing atherogenic processes

such as foam cell formation and LDL oxidation [14,15]; (3)

the lesions could be complicated by an immunopathogenic

role of C. pneumoniae, attracting inflammatory cells

causing tissue damage. T cell infiltration which was

demonstrated both in murine and human atherosclerotic

plaques [39,98]; (4) triggering of an autoimmune reaction to

human Hsp60 by antigenic mimicry could be interfering

with atherogenesis [14,99]; and (5) apart from the athero-

genic properties, C. pneumoniae could complicate athero-

sclerotic disease further by destabilizing plaques by

reducing the fibrous cap area and stimulating matrix

degrading metalloproteinases [40], or by enhancing throm-

bogenicity by stimulating coagulation factors and tissue

factor expression [100,101].

Antibiotics were successful for the treatment of the acute

pulmonary infection, but had no effect on the atherogenic

properties of C. pneumoniae when they were administered 2

weeks after infection [21]. In addition, in rabbits, antibiotics

inhibited atherogenesis only slightly when they were

administered 2 weeks after infection, but they were much

more effective when they were administered within 5 days

after infection [23,102]. Furthermore, antibiotics failed to

completely eradicate C. pneumoniae from the organ tissues

[48,103]. These findings may help to understand the

negative results of the human WIZARD study, because

the antibiotics in animals were apparently only effective

when they were given during the actual infection itself. The

acute C. pneumoniae infection in humans frequently passes

clinically unnoticed.

C. pneumoniae was one of the first and therefore most

frequently studied infectious organisms that showed athero-

genic properties in mice. The effect seemed to be specific to

C. pneumoniae because C. trachomatis did not influence

atherogenesis [104]. However, other organisms that were

not clearly related did show atherogenic properties in similar

mouse models. These organisms included various bacteria,

viruses and protozoa, such as Porphyromonas gingivalis,

murine cytomegalovirus, murine g-herpesvirus-68, Toxo-

plasma gondii and Trypanosoma cruzi [105–110]. The

contribution of these single pathogens is still being

researched. Additional atherogenic properties to C. pneumo-

niae infection were found in two out of three coinfection

studies with H. pylori and murine cytomegalovirus [70].

After all, the impact of the pathogen burden as a whole may

still be more important than the impact of single pathogens

alone.

In conclusion, the evidence for a pathogenic role of C.

pneumoniae in atherosclerosis in mouse models seems

convincing, because the results were reproducible and

confirmed by different research groups. However, the precise

mechanisms of this relationship remain unclear, although

many theories exist. Temptations to eradicate C. pneumoniae

from the body, both by the immune system and by antibiotic

treatment, generally encountered many difficulties which

could be related to the unusual gram-negative, obligate

intracellular characteristics of the bacterium. The value of the

currently available antibiotics should not be overestimated,

because they were only effective in preventing the long-term

atherogenic effects of C. pneumoniae infection when they

were given during the acute infection, which is often

asymptomatic or aspecific in humans. Therefore, the focus

of future research should merely shift back to basic research.

The precise mechanisms by which C. pneumoniae is

interfering with atherogenesis should be further elucidated

to enable more specific strategies to interfere with this

process, e.g. by immunosuppressive agents. In addition, the

role of other infectious pathogens should be further exam-

ined, and especially the impact of the pathogen burden as a

whole. The development of an effective vaccine would be the

final strategy to prevent chlamydial disease and its compli-

cations, but not to prevent the impact of the pathogen burden.

References

[1] Ross R. Atherosclerosis—an inflammatory disease. N Engl J Med

1999;340:115–26.

[2] Espinola-Klein C, Rupprecht HJ, Blankenberg S, Bickel C, Kopp H,

Rippin G. Impact of infectious burden on extent and long-term

prognosis of atherosclerosis. Circulation 2002;105:15–21.

[3] Everett KD, Andersen AA. Identification of nine species of the

Chlamydiaceae using PCR-RFLP. Int J Syst Bacteriol 1999;49(Pt 2):

803–13.

[4] Kuo CC, Jackson LA, Campbell LA, Grayston JT. Chlamydia

pneumoniae (TWAR). Clin Microbiol Rev 1995;8:451–61.

[5] Grayston JT. Background and current knowledge of Chlamydia

pneumoniae and atherosclerosis. J Infect Dis 2000;181(Suppl. 3):

S402–10.

[6] Wright SW, Edwards KM, Decker MD, Grayston JT, Wang S.

Prevalence of positive serology for acute Chlamydia pneumoniae


Dow



ay 2022

infection in emergency department patients with persistent cough.

Acad Emerg Med 1997;4:179–83.

[7] Odeh M, Oliven A. Chlamydial infections of the heart. Eur J Clin

Microbiol Infect Dis 1992;11:885–93.

[8] Gnarpe H, Gnarpe J, Gastrin B, Hallander H. Chlamydia

pneumoniae and myocarditis. Scand J Infect Dis, Suppl 1997;

104:50–2.

[9] Swanborg RH, Whittum-Hudson JA, Hudson AP. Human herpesvi-

rus 6 and Chlamydia pneumoniae as etiologic agents in multiple

sclerosis—a critical review. Microbes Infect 2002;4:1327–33.

[10] Saikku P, Leinonen M, Mattila K, Ekman MR, Nieminen MS,

Makela PH, et al. Serological evidence of an association of a novel

Chlamydia, TWAR, with chronic coronary heart disease and acute

myocardial infarction. Lancet 1988;2:983–6.

[11] Danesh J, Whincup P, Walker M, Lennon L, Thomson A, Appleby P,

et al. Chlamydia pneumoniae IgG titres and coronary heart disease:

prospective study and meta-analysis. BMJ 2000;321:208–13.

[12] Kuo CC, Shor A, Campbell LA, Fukushi H, Patton DL, Grayston JT.

Demonstration of Chlamydia pneumoniae in atherosclerotic lesions

of coronary arteries. J Infect Dis 1993;167:841–9.

[13] Taylor-Robinson D, Thomas BJ. Chlamydia pneumoniae in athero-

sclerotic tissue. J Infect Dis 2000;181(Suppl. 3):S437–40.

[14] Kol A, Sukhova GK, Lichtman AH, Libby P. Chlamydial heat shock

protein 60 localizes in human atheroma and regulates macrophage

tumor necrosis factor-alpha and matrix metalloproteinase expression.

Circulation 1998;98:300–7.

[15] Kalayoglu MV, Indrawati, Morrison RP, Morrison SG, Yuan,

Byrne GI. Chlamydial virulence determinants in atherogenesis: the

role of chlamydial lipopolysaccharide and heat shock protein 60 in

macrophage–lipoprotein interactions. J Infect Dis 2000;181(Suppl.

3):S483–9.

[16] Hu H, Pierce GN, Zhong G. The atherogenic effects of chlamydia are

dependent on serum cholesterol and specific to Chlamydia pneumo-

niae. J Clin Invest 1999;103:747–53.

[17] Moazed TC, Campbell LA, Rosenfeld ME, Grayston JT, Kuo CC.

Chlamydia pneumoniae infection accelerates the progression of

atherosclerosis in apolipoprotein E-deficient mice. J Infect Dis

1999;180:238–41.

[18] Liu L, Hu H, Ji H, Murdin AD, Pierce GN, Zhong G. Chlamydia

pneumoniae infection significantly exacerbates aortic atherosclerosis

in an LDLR�/� mouse model within six months. Mol Cell Biochem

2000;215:123–8.

[19] Blessing E, Campbell LA, Rosenfeld ME, Chough N, Kuo CC.

Chlamydia pneumoniae infection accelerates hyperlipidemia induced

atherosclerotic lesion development in C57BL/6J mice. Atheroscle-

rosis 2001;158:13–7.

[20] Burnett MS, Gaydos CA, Madico GE, Glad SM, Paigen B, Quinn

TC, et al. Atherosclerosis in apoE knockout mice infected with

multiple pathogens. J Infect Dis 2001;183:226–31.

[21] Rothstein NM, Quinn TC, Madico G, Gaydos CA, Lowenstein CJ.

Effect of azithromycin on murine arteriosclerosis exacerbated by

Chlamydia pneumoniae. J Infect Dis 2001;183:232–8.

[22] Chesebro BB, Blessing E, Kuo CC, Rosenfeld ME, Puolakkainen

LA, Campbell LA. Nitric oxide synthase plays a role in Chlamydia

pneumoniae-induced atherosclerosis. Cardiovasc Res 2003;

60:170–4.

[23] Muhlestein JB, Anderson JL, Hammond EH, Zhao L, Trehan S,

Schwobe EP, et al. Infection with Chlamydia pneumoniae accelerates

the development of atherosclerosis and treatment with azithromycin

prevents it in a rabbit model. Circulation 1998;97:633–6.

[24] Dunne MW. Rationale and design of a secondary prevention trial of

antibiotic use in patients after myocardial infarction: the WIZARD

(weekly intervention with zithromax [azithromycin] for atheroscle-

rosis and its related disorders) trial. J Infect Dis 2000;181(Suppl 3):

S572–8.

[25] Grayston JT. Antibiotic treatment of atherosclerotic cardiovascular

disease. Circulation 2003;107:1228–30.

[26] O’Connor CM, Dunne MW, Pfeffer MA, Muhlestein JB, Yao L,

Gupta S, et al. Azithromycin for the secondary prevention of

coronary heart disease events: the WIZARD study: a randomized

controlled trial. JAMA 2003;290:1459–66.

[27] Jackson LA. Description and status of the azithromycin and coronary

events study (ACES). J Infect Dis 2000;181(Suppl. 3):S579–81.

[28] Cannon CP, McCabe CH, Belder R, Breen J, Braunwald E. Design

of the pravastatin or atorvastatin evaluation and infection therapy

(PROVE IT)-TIMI 22 trial. Am J Cardiol 2002;89:860–1.

[29] Pislaru SV, Van de Werf F. Antibiotic therapy for coronary artery

disease: can a WIZARD change it all? JAMA 2003;290:1515–6.

[30] Kishimoto T. Studies on Chlamydia pneumoniae, strain TWAR,

infection: I. Experimental infection of C. pneumoniae in mice and

serum antibodies against TWAR by MFA. Kansenshogaku Zasshi

1990;64:124–31.

[31] Kaukoranta-Tolvanen SS, Laurila AL, Saikku P, Leinonen M,

Liesirova L, Laitinen K. Experimental infection of Chlamydia

pneumoniae in mice. Microb Pathog 1993;15:293–302.

[32] Yang ZP, Kuo CC, Grayston JT. A mouse model of Chlamydia

pneumoniae strain TWAR pneumonitis. Infect Immun 1993;61:

2037–40.

[33] Meijer A, Morre SA, van den Brule AJ, Savelkoul PH, Ossewaarde

JM. Genomic relatedness of Chlamydia isolates determined by

amplified fragment length polymorphism analysis. J Bacteriol

1999;181:4469–75.

[34] Read TD, Brunham RC, Shen C, Gill SR, Heidelberg JF, White

O, et al. Genome sequences of Chlamydia trachomatis MoPn

and Chlamydia pneumoniae AR39. Nucleic Acids Res 2000;

28:1397–406.

[35] Karunakaran KP, Blanchard JF, Raudonikiene A, Shen C, Murdin

RC, Brunham RC. Molecular detection and seroepidemiology of the

Chlamydia pneumoniae bacteriophage (PhiCpn1). J Clin Microbiol

2002;40:4010–4.

[36] Ekman MR, Grayston JT, Visakorpi R, Kleemola M, Kuo CC,

Saikku P. An epidemic of infections due to Chlamydia pneumoniae

in military conscripts. Clin Infect Dis 1993;17:420–5.

[37] Peterson EM, Cheng X, Qu Z, de La Maza LM. Characterization of

the murine antibody response to peptides representing the variable

domains of the major outer membrane protein of Chlamydia

pneumoniae. Infect Immun 1996;64:3354–9.

[38] Moazed TC, Kuo CC, Grayston JT, Campbell LA. Evidence of

systemic dissemination of Chlamydia pneumoniae via macrophages

in the mouse. J Infect Dis 1998;177:1322–5.

[39] Ezzahiri R, Nelissen-Vrancken HJ, Kurvers HA, Stassen FR, Vliegen

GE, Grauls GE, et al. Chlamydophila pneumoniae (Chlamydia

pneumoniae) accelerates the formation of complex atherosclerotic

lesions in Apo E3-Leiden mice. Cardiovasc Res 2002;56:269–76.

[40] Ezzahiri R, Stassen FR, Kurvers HA, van Pul MM, Kitslaar

PJ, Bruggeman PJ. Chlamydia pneumoniae infection induces an

unstable atherosclerotic plaque phenotype in LDL-receptor,

ApoE double knockout mice. Eur J Vasc Endovasc Surg

2003;26:88–95.

[41] Erkkila L, Rottenberg ME, Laitinen K. Comparison of anesthetics for

inoculation of mice with Chlamydia pneumoniae. Comp Med

2000;50:46–8.

[42] Moazed TC, Kuo C, Grayston JT, Campbell LA. Murine models of

Chlamydia pneumoniae infection and atherosclerosis. J Infect Dis

1997;175:883–90.

[43] Blessing E, Lin TM, Campbell LA, Rosenfeld ME, Lloyd D, Kuo C.

Chlamydia pneumoniae induces inflammatory changes in the heart

and aorta of normocholesterolemic C57BL/6J mice. Infect Immun

2000;68:4765–8.

[44] Kimura M. Experimental study on the mechanisms of Chlamydia

pneumoniae respiratory infection in mice with former chlamydial

exposure. Kansenshogaku Zasshi 1994;68:50–8.

[45] Nakata K, Okazaki Y, Hattori H, Nakamura S. Protective effects of

sparfloxacin in experimental pneumonia caused by Chlamydia


Dow



ay 2022

pneumoniae in leukopenic mice. Antimicrob Agents Chemother

1994;38:1757–62.

[46] Kaukoranta-Tolvanen SE, Laurila AL, Saikku P, Leinonen M,

Laitinen K. Experimental Chlamydia pneumoniae infection in mice:

effect of reinfection and passive immunization. Microb Pathog

1995;18:279–88.

[47] Yang ZP, Kuo CC, Grayston JT. Systemic dissemination of

Chlamydia pneumoniae following intranasal inoculation in mice. J

Infect Dis 1995;171:736–8.

[48] Malinverni R, Kuo CC, Campbell LA, Lee A, Grayston JT. Effects

of two antibiotic regimens on course and persistence of experimental

Chlamydia pneumoniae TWAR pneumonitis. Antimicrob Agents

Chemother 1995;39:45–9.

[49] Masson ND, Toseland CD, Beale AS. Relevance of Chlamydia

pneumoniae murine pneumonitis model to evaluation of antimicro-

bial agents. Antimicrob Agents Chemother 1995;39:1959–64.

[50] Malinverni R, Kuo CC, Campbell LA, Grayston JT. Reactivation of

Chlamydia pneumoniae lung infection in mice by cortisone. J Infect

Dis 1995;172:593–4.

[51] Laitinen K, Laurila AL, Leinonen M, Saikku P. Reactivation of

Chlamydia pneumoniae infection in mice by cortisone treatment.

Infect Immun 1996;64:1488–90.

[52] Penttila JM, Anttila M, Puolakkainen M, Laurila A, Varkila K,

Sarvas M, et al. Local immune responses to Chlamydia pneumoniae

in the lungs of BALB/c mice during primary infection and

reinfection. Infect Immun 1998;66:5113–8.

[53] Penttila JM, Pyhala R, Sarvas M, Rautonen N. Expansion of a

novel pulmonary CD3(�) CD4(+) CD8(+) cell population in mice

during Chlamydia pneumoniae infection. Infect Immun 1998;66:

3290–4.

[54] Penttila JM, Anttila M, Varkila K, Puolakkainen M, Sarvas M,

Makela PH, et al. Depletion of CD8+ cells abolishes memory in

acquired immunity against Chlamydia pneumoniae in BALB/c mice.

Immunology 1999;97:490–6.

[55] Peterson EM, de la Maza LM, Brade L, Brade H. Characterization

of a neutralizing monoclonal antibody directed at the lipopoly-

saccharide of Chlamydia pneumoniae. Infect Immun 1998;66:

3848–55.

[56] Rottenberg ME, Gigliotti Rothfuchs AC, Gigliotti D, Svanholm C,

Bandholtz L, Wigzell H. Role of innate and adaptive immunity in

the outcome of primary infection with Chlamydia pneumoniae, as

analyzed in genetically modified mice. J Immunol 1999;162:

2829–36.

[57] Wolf K, Malinverni R. Effect of azithromycin plus rifampin versus

that of azithromycin alone on the eradication of Chlamydia

pneumoniae from lung tissue in experimental pneumonitis. Anti-

microb Agents Chemother 1999;43:1491–3.

[58] Liuba P, Karnani P, Pesonen E, Paakkari I, Forslid A, Johansson L,

et al. Endothelial dysfunction after repeated Chlamydia pneumoniae

infection in apolipoprotein E-knockout mice. Circulation 2000;102:

1039–44.

[59] Vuola JM, Puurula V, Anttila M, Makela PH, Rautonen N. Acquired

immunity to Chlamydia pneumoniae is dependent on gamma

interferon in two mouse strains that initially differ in this respect

after primary challenge. Infect Immun 2000;68:960–4.

[60] Geng Y, Berencsi K, Gyulai Z, Valyi-Nagy T, Gonczol E, Trinchieri

G. Roles of interleukin-12 and gamma interferon in murine

Chlamydia pneumoniae infection. Infect Immun 2000;68:2245–53.

[61] Rottenberg ME, Gigliotti Rothfuchs A, Gigliotti D, Ceausu M, Une

C, Levitsky V, et al. Regulation and role of IFN-gamma in the innate

resistance to infection with Chlamydia pneumoniae. J Immunol

2000;164:4812–8.

[62] Pal S, Peterson EM, de La Maza LM. Role of Nramp1 deletion in

Chlamydia infection in mice. Infect Immun 2000;68:4831–3.

[63] Meijer A, Roholl PJ, Gielis-Proper SK, Meulenberg YF, Ossewaarde

JM. Chlamydia pneumoniae in vitro and in vivo: a critical evaluation

of in situ detection methods. J Clin Pathol 2000;53:904–10.

[64] Svanholm C, Bandholtz L, Castanos-Velez E, Wigzell H, Rottenberg

ME. Protective DNA immunization against Chlamydia pneumoniae.

Scand J Immunol 2000;51:345–53.

[65] Murdin AD, Dunn P, Sodoyer R, Wang J, Caterini J, Brunham RC,

et al. Use of a mouse lung challenge model to identify antigens

protective against Chlamydia pneumoniae lung infection. J Infect

Dis 2000;181(Suppl 3):S544–51.

[66] Bin XX, Wolf K, Schaffner T, Malinverni R. Effect of azithromycin

plus rifampin versus amoxicillin alone on eradication and inflam-

mation in the chronic course of Chlamydia pneumoniae pneumonitis

in mice. Antimicrob Agents Chemother 2000;44:1761–4.

[67] Penttila T, Vuola JM, Puurula V, Anttila M, Sarvas M, Rautonen N,

et al. Immunity to Chlamydia pneumoniae induced by vaccination

with DNA vectors expressing a cytoplasmic protein (Hsp60) or outer

membrane proteins (MOMP and Omp2). Vaccine 2000;19:1256–65.

[68] Aalto-Setala K, Laitinen K, Erkkila L, Leinonen M, Jauhiainen M,

Ehnholm C, et al. Chlamydia pneumoniae does not increase

atherosclerosis in the aortic root of apolipoprotein E-deficient mice.

Arterioscler Thromb Vasc Biol 2001;21:578–84.

[69] Caligiuri G, Rottenberg M, Nicoletti A, Wigzell H, Hansson GK.

Chlamydia pneumoniae infection does not induce or modify

atherosclerosis in mice. Circulation 2001;103:2834–8.

[70] Burian K, Berencsi K, Endresz V, Gyulai Z, Valyi-Nagy T, Valyi-

Nagy I, et al. Chlamydia pneumoniae exacerbates aortic inflamma-

tory foci caused by murine cytomegalovirus infection in normocho-

lesterolemic mice. Clin Diagn Lab Immunol 2001;8:1263–6.

[71] Blessing E, Campbell LA, Rosenfeld ME, Kuo CC. Chlamydia

pneumoniae and hyperlipidemia are co-risk factors for atheroscle-

rosis: infection prior to induction of hyperlipidemia does not

accelerate development of atherosclerotic lesions in C57BL/6J mice.

Infect Immun 2002;70:5332–4.

[72] Erkkila L, Laitinen K, Laurila A, Saikku P, Leinonen M.

Experimental Chlamydia pneumoniae infection in NIH/S mice:

effect of reinoculation with chlamydial or cell preparation on culture,

PCR and histological findings of lung tissue. Vaccine 2002;

20:2318–24.

[73] Tiirola T, Erkkila L, Laitinen K, Leinonen M, Saikku P, Bloigu A,

et al. Effect of acute Chlamydia pneumoniae infection on

lipoprotein metabolism in NIH/S mice. Scand J Clin Lab Invest

2002;62:477–84.

[74] Bandholtz L, Kreuger MR, Svanholm C, Wigzell H, Rottengerg ME.

Adjuvant modulation of the immune responses and the outcome of

infection with Chlamydia pneumoniae. Clin Exp Immunol 2002;

130:393–403.

[75] Airaksinen U, Penttila T, Wahlstrom E, Vuola JM, Puolakkainen M,

Sarvas M. Production of Chlamydia pneumoniae proteins in Bacillus

subtilis and their use in characterizing immune responses in the

experimental infection model. Clin Diagn Lab Immunol 2003;10:

367–75.

[76] Burian K, Hegyesi H, Buzas E, Endresz V, Kis Z, Falus A, et al.

Chlamydophila (Chlamydia) pneumoniae induces histidine decar-

boxylase production in the mouse lung. Immunol Lett 2003;

89:229–36.

[77] Shi Y, Yin J, Zhan H, Feng G, Zhang X, Su X, et al. The

pathogenesis of Chlamydia pneumoniae-type pneumonitis in mice.

Chin Med J (Engl) 2003;116:328–32.

[78] Liuba P, Pesonen E, Paakkari I, Batra S, Andersen L, Forslid A, et al.

Co-infection with Chlamydia pneumoniae and Helicobacter pylori

results in vascular endothelial dysfunction and enhanced VCAM-1

expression in apoE-knockout mice. J Vasc Res 2003;40:115–22.

[79] Rothfuchs AG, Kreuger MR, Wigzell H, Rottenberg ME. Macro-

phages, CD4+ or CD8+ cells are each sufficient for protection

against Chlamydia pneumoniae infection through their ability to

secrete IFN-gamma. J Immunol 2004;172:2407–15.

[80] Mygind T, Vandahl B, Pedersen AS, Christiansen G, Hollsberg P,

Birkelund S. Identification of an in vivo CD4+ T cell-mediated

response to polymorphic membrane proteins of Chlamydia pneumo-


Dow



ay 2022

niae during experimental infection. FEMS Immunol Med Microbiol

2004;40:129–37.

[81] Little CS, Hammond CJ, MacIntyre A, Balin BJ, Appelt DM.

Chlamydia pneumoniae induces Alzheimer-like amyloid plaques in

brains of BALB/c mice. Neurobiol Aging 2004;25:419–29.

[82] Tormakangas L, Saario E, Bem David D, Bryskier A, Leinonen M,

Saikku P. Treatment of acute Chlamydia pneumoniae infection with

telithromycin in C57BL/6J mice. J Antimicrob Chemother 2004;

53:1101–4.

[83] Igietseme JU, Black CM, Caldwell HD. Chlamydia vaccines:

strategies and status. BioDrugs 2002;16:19–35.

[84] Caspar-Bauguil S, Puissant B, Nazzal D, Lefevre JC, Thomsen N,

Salvayre R, et al. Chlamydia pneumoniae induces interleukin-10

production that down-regulates major histocompatibility complex

class I expression. J Infect Dis 2000;182:1394–401.

[85] Fan P, Dong F, Huang Y, Zhong G. Chlamydia pneumoniae secretion

of a protease-like activity factor for degrading host cell transcription

factors required for [correction of factors is required for] major

histocompatibility complex antigen expression. Infect Immun 2002;

70:345–9.

[86] Fischer SF, Hacker G. Characterization of antiapoptotic activities of

Chlamydia pneumoniae in infected cells. Ann NY Acad Sci

2003;1010:565–7.

[87] van Zandbergen G, Gieffers J, Kothe H, Rupp J, Bollinger A, Aga E,

et al. Chlamydia pneumoniae multiply in neutrophil granulocytes and

delay their spontaneous apoptosis. J Immunol 2004;172:1768–76.

[88] Hammerschlag MR. The intracellular life of chlamydiae. Semin

Pediatr Infect Dis 2002;13:239–48.

[89] Meijer A, Roholl PJ, Gielis-Proper SK, Ossewaarde JM. Chlamydia

pneumoniae antigens, rather than viable bacteria, persist in athero-

sclerotic lesions. J Clin Pathol 2000;53:911–6.

[90] de Bont N, Netea MG, Demacker PN, Kullberg BJ, van der Meer

AF, Stalenhoef AF. Apolipoprotein E-deficient mice have an

impaired immune response to Klebsiella pneumoniae. Eur J Clin

Investig 2000;30:818–22.

[91] Kuo CC, Campbell LA, Rosenfeld ME. Chlamydia pneumoniae

infection and atherosclerosis: methodological considerations. Circu-

lation 2002;105:E34.

[92] Dansky HM, Shu P, Donavan M, Montagno J, Nagle DL, Smutko JS,

et al. A phenotype-sensitizing Apoe-deficient genetic background

reveals novel atherosclerosis predisposition loci in the mouse.

Genetics 2002;160:1599–608.

[93] Fong IW, Chiu B, Viira E, Jang D, Mahony JB. De novo induction of

atherosclerosis by Chlamydia pneumoniae in a rabbit model. Infect

Immun 1999;67:6048–55.

[94] Pislaru SV, Van Ranst M, Pislaru C, Szelid Z, Theilmeier G,

Ossewaarde JM, et al. Chlamydia pneumoniae induces neointima

formation in coronary arteries of normal pigs. Cardiovasc Res

2003;57:834–42.

[95] Herrera VL, Shen L, Lopez LV, Didishvili T, Zhang YX, Ruiz-Opazo

N. Chlamydia pneumoniae accelerates coronary artery disease

progression in transgenic hyperlipidemia-genetic hypertension rat

model. Mol Med 2003;9:135–42.

[96] Kalayoglu MV, Libby P, Byrne GI. Chlamydia pneumoniae as an

emerging risk factor in cardiovascular disease. JAMA 2002;

288:2724–31.

[97] May AE, Redecke V, Gruner S, Schmidt R, Massberg S, Miethke T,

et al. Recruitment of Chlamydia pneumoniae-infected macrophages

to the carotid artery wall in noninfected, nonatherosclerotic mice.

Arterioscler Thromb Vasc Biol 2003;23:789–94.

[98] van der Wal AC. Chlamydia pneumoniae inside the atherosclerotic

plaque—does it affect plaque inflammation and plaque progression?

Cardiovasc Res 2002;56:178–80.

[99] Bachmaier K, Neu N, de la Maza LM, Pal S, Hessel A, Penninger

JM. Chlamydia infections and heart disease linked through antigenic

mimicry. Science 1999;283:1335–9.

[100] Dechend R, Maass M, Gieffers J, Dietz R, Scheidereit C, Leutz A,

et al. Chlamydia pneumoniae infection of vascular smooth muscle

and endothelial cells activates NF-kappaB and induces tissue factor

and PAI-1 expression: a potential link to accelerated arteriosclerosis.

Circulation 1999;100:1369–73.

[101] Virok D, Loboda A, Kari L, Nebozhyn M, Chang C, Nichols C, et al.

Infection of U937 monocytic cells with Chlamydia pneumoniae

induces extensive changes in host cell gene expression. J Infect Dis

2003;188:1310–21.

[102] Fong IW. Antibiotics effects in a rabbit model of Chlamydia

pneumoniae-induced atherosclerosis. J Infect Dis 2000;181

(Suppl. 3):S514–8.

[103] Gieffers J, Fullgraf H, Jahn J, Klinger M, Dalhoff K, Katus HA, et al.

Chlamydia pneumoniae infection in circulating human monocytes is

refractory to antibiotic treatment. Circulation 2001;103:351–6.

[104] Blessing E, Nagano S, Campbell LA, Rosenfeld ME, Kuo CC. Effect

of Chlamydia trachomatis infection on atherosclerosis in apolipo-

protein E-deficient mice. Infect Immun 2000;68:7195–7.

[105] Sunnemark D, Harris RA, Frostegard J, Orn A. Induction of early

atherosclerosis in CBA/J mice by combination of Trypanosoma

cruzi infection and a high cholesterol diet. Atherosclerosis 2000;

153:273–82.

[106] Alber DG, Vallance P, Powell KL. Enhanced atherogenesis is not an

obligatory response to systemic herpesvirus infection in the apoE-

deficient mouse: comparison of murine gamma-herpesvirus-68 and

herpes simplex virus-1. Arterioscler Thromb Vasc Biol 2002;

22:793–8.

[107] Lalla E, Lamster IB, Hofmann MA, Bucciarelli L, Jerud AP, Tucker

S, et al. Oral infection with a periodontal pathogen accelerates early

atherosclerosis in apolipoprotein E-null mice. Arterioscler Thromb

Vasc Biol 2003;23:1405–11.

[108] Naghavi M, Wyde P, Litovsky S, Madjid M, Akhtar A, Naguib S,

et al. Influenza infection exerts prominent inflammatory and

thrombotic effects on the atherosclerotic plaques of apolipoprotein

E-deficient mice. Circulation 2003;107:762–8.

[109] Portugal LR, Fernandes LR, Cesar GC, Santiago HC, Oliveira DR,

Silva NM, et al. Infection with Toxoplasma gondii increases

atherosclerotic lesion in ApoE-deficient mice. Infect Immun 2004;

72:3571–6.

[110] Vliegen I, Duijvestijn A, Grauls G, Herngreen S, Bruggeman C,

Stassen F. Cytomegalovirus infection aggravates atherogenesis in

apoE knockout mice by both local and systemic immune activation.

Microbes Infect 2004;6:17–24.

Chlamydia pneumoniae infections in mouse models

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