Post on 25-Jan-2023
Comparative evaluationoftherapeuticDNAvaccines againstTrypanosoma cruzi inmiceGilma Sanchez-Burgos1, R. Gabino Mezquita-Vega1, Javier Escobedo-Ortegon1, Maria JesusRamirez-Sierra1, Arletty Arjona-Torres1, Ali Ouaissi2, Mauricio M. Rodrigues3 & Eric Dumonteil1
1Laboratorio de Parasitologıa, Centro de Investigaciones Regionales ‘Dr Hideyo Noguchi’, Universidad Autonoma de Yucatan, Merida, Yucatan,
Mexico; 2INSERM, IRD, Unite de Recherche no. 008 ‘Pathogenie des Trypanosomatides’, Centre IRD de Montpellier; Montpellier, France; and3CINTERGEN- Centro Interdisciplinar de Terapia Genica, Departamento de Microbiologia, Inmunologia e Parasitologia, Universidade Federal de Sao
Paulo, Sao Paulo, SP, Brazil
Correspondence: Eric Dumonteil,
Laboratorio de Parasitologıa, Centro de
Investigaciones Regionales ‘Dr Hideyo
Noguchi’, Universidad Autonoma de Yucatan,
Av. Itzaes 490 x 59, Centro, 97000, Merida,
Yucatan, Mexico. Tel.: 151 999 924 5910,
Ext. 118; fax: 152 999 923 6120; e-mail:
oliver@uady.mx
Received 19 January 2006; revised 6 March
2007; accepted 14 March 2007.
DOI:10.1111/j.1574-695X.2007.00251.x
Editor: Willem van Eden
Keywords
protozoa; chagas disease; therapeutic vaccine;
immunotherapy.
Abstract
Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, is a major
public health problem in most of Latin America. A key priority is the development
of new treatments, due to the poor efficacy of current ones. We report here the
comparative evaluation of therapeutic DNA vaccines encoding various T. cruzi
antigens. ICR mice infected with 500 parasites intraperitoneally were treated at
5 and 12 days postinfection with 20mg of plasmid DNA encoding T. cruzi antigens
TSA-1, TS, ASP-2-like, Tc52 or Tc24. Treatment with plasmid encoding TS and/or
ASP-2-like antigens had no significant effect on parasitemia or survival. Treatment
with Tc52 DNA significantly reduced parasitemia, as well as cardiac parasite
burden, and improved survival, although myocarditis was not significantly
affected. Finally, treatment with plasmids encoding Tc24 and TSA-1 induced the
most complete control of disease as evidenced by significant reductions in
parasitemia, mortality, myocarditis and heart parasite burden. These data demon-
strate that therapeutic vaccine efficacy is dependent on the antigen and suggest that
DNA vaccines encoding Tc24, TSA-1, and Tc52 represent the best candidates for
further studies of a therapeutic vaccine against Chagas disease.
Introduction
Chagas disease, or American trypanosomiasis, is caused by the
protozoan parasite Trypanosoma cruzi, and it affects an esti-
mated 16–18 million persons, with close to 100 million people
at risk of infection in the Americas. About 30–40% of infected
patients develop chronic chagasic cardiomyopathy, which
represents a dramatic burden in public health (WHO, 2002).
There has been extensive debate on the mechanisms
involved in this pathology (Kierszenbaum, 1999; Tarleton,
2001; Girones & Fresno, 2003). Part of the susceptibility of
patients to develop chronic chagasic cardiomyopathy has been
associated with specific major histocompatibility complex
(MHC) haplotypes (Colorado et al., 2000; Cruz-Robles et al.,
2004). In addition, some studies suggested that tissue damage
was associated with the presence and replication of intracel-
lular amastigotes, and others proposed that autoimmunity
induced by parasite antigens mimicking host proteins was
responsible for tissue damage (Kierszenbaum, 1999; Tarleton,
2001; Girones & Fresno, 2003). It is now accepted that the
presence of parasites in cardiac tissue is necessary to initiate
and maintain the inflammatory response, and that therapeutic
treatments or vaccines aimed at eliminating T. cruzi would
limit or prevent the progression towards chronic chagasic
cardiomyopathy (Bhatia & Garg, 2005).
Current chemotherapy relies on nitrofurans (Nifurtimox),
or nitroimidazoles (Benznidazole). However, the usefulness
of these drugs is limited by their reduced efficacy (mostly
during early stages of the infection), serious side effects, and
the emergence of drug-resistant strains of parasites (Castro
et al., 2006). Efforts are thus urgently needed to identify new
drug candidates. A number of compounds have been eval-
uated in preclinical models for the chemotherapy of T. cruzi
infection and are providing some variable but encouraging
results (Buckner et al., 2003; Urbina & Docampo, 2003;
Steverding & Tyler, 2005). Nonetheless, a major limitation of
chemotherapy is that most treatments require very long
administration regimens to be effective.
Therapeutic vaccines, aimed at reinforcing the immune
response of an infected host, represent a novel and attractive
FEMS Immunol Med Microbiol ]] (2007) 1–9 c� 2007 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved
alternative to chemotherapy against chronic diseases
(Autran et al., 2004). The major advantages of this strategy
are that it relies on short treatment regimens (Lai et al.,
1996; Boyer et al., 1997; Lowrie et al., 1999; Lodmell &
Ewalt, 2001; Bahloul et al., 2003), and the induction of
multiple effector mechanisms against the pathogen may
have high efficacy and lower the possibilities of resistance.
In particular, we provided proof-of-concept data demon-
strating that two doses of therapeutic DNA vaccines encod-
ing parasite antigens TSA-1 or Tc24 could reduce disease
severity in mice infected with an otherwise lethal dose of
T. cruzi (Dumonteil et al., 2004). Importantly, this treatment
is effective at reducing disease development when adminis-
tered at various times during both the acute and the chronic
phase of the infection, although efficacy decreases when
treatment is delayed (Dumonteil et al., 2004). The efficacy of
such therapeutic DNA vaccines seems to rely, at least in part,
on the induction of parasite-specific interferon gamma
(IFN-g)-producing CD41 and CD81 T cells (Zapata-Estrel-
la et al., 2006), confirming that stimulation of the immune
response by the vaccine limits disease progression rather
than exacerbates tissue inflammation and damage. This is
also in agreement with several studies showing that a T
helper (Th) 1 type immune response is required for clearing
the parasite from infected mice (Silva et al., 1995; Miller
et al., 1996; Santori et al., 1996; Paiva et al., 1999; Hoft &
Eickhoff, 2002) and that less severe disease is observed in
patients with higher frequency of IFN-g-producing T cells
(Laucella et al., 2004). Various vaccine studies have further
established that to be protective against T. cruzi, antigens
need to contain both MHC I- and II epitopes, and lead to a
full activation of the immune response, including helper
CD41 and cytotoxic CD81 cells, as well as lytic antibodies
(Bhatia & Garg, 2005).
Nonetheless, most of these studies have focused on antigens
from the blood-form trypomastigote stage of the parasite, and
antigens from intracellular amastigotes have been much less
explored (Low et al., 1998; Garg & Tarleton, 2002; Boscardin
et al., 2003). There is indeed a good rationale for designing
vaccines aimed at either stages of the parasite, and it would be
expected that vaccines targeting the circulating or the intra-
cellular stages would be equally effective at controlling disease
progression. Thus, it remains unclear how the nature of the
antigens may affect vaccine efficacy and which may be the
most promising for the detailed study of the immune
mechanisms underlying their therapeutic efficacy.
To address this issue and identify new therapeutic vaccine
candidates, we report here the comparative evaluation of the
efficacy of vaccines encoding several T. cruzi antigens, using
a convenient acute phase model. We selected ASP-2-like
clone 9, an antigen whose mRNA is observed in all develop-
mental stages of the parasite, but the full length protein is
only detected in amastigotes (Boscardin et al., 2003).
Similarly, T. cruzi 52 kDa antigen (Tc52) is mostly expressed
in amastigotes and epimastigotes, and downregulated in
trypomastigotes, and it is considered a virulence factor
(Ouaissi et al., 1995). We also investigated two trypomasti-
gote-specific antigens from the trans-sialidase family, the
trans-sialidase (TS) (Abuin et al., 1999) and the trypomasti-
gote-surface antigen 1 (TSA-1) (Fouts et al., 1991), although
some members of this family are also expressed in amasti-
gotes, and may provide some cross-reactions. Finally, we
included T. cruzi 24 kDa antigen (Tc24), which is present in
all developmental stages of the parasite (Ouaissi et al., 1992;
Taibi et al., 1993). Well-defined MHC I and II epitopes have
been identified in most of these antigens and they are able to
induce a strong and complete immune response in mice
(Taibi et al., 1993; Wrightsman et al., 1994; Wizel et al., 1998;
Rodrigues et al., 1999). These antigens can also provide
significant protection as prophylactic DNA or recombinant
protein vaccines (Costa et al., 1998; Wizel et al., 1998;
Fujimura et al., 2001; Ouaissi et al., 2002; Boscardin et al.,
2003), and TSA-1 and Tc24 have been shown to be effective
as therapeutic DNA vaccines (Dumonteil et al., 2004).
Materials and methods
Experimental infection of mice
To avoid potential genetic restriction of vaccine efficacy in
inbred mice, we used outbred ICR mice, which show MHC
polymorphism. Six-week-old female mice were infected by
intraperitoneal injection of a lethal dose of 500 blood
trypomastigotes of the H1 strain, previously isolated from a
human case in Yucatan, Mexico, as before (Dumonteil et al.,
2004; Zapata-Estrella et al., 2006). Infection was monitored
by counting peripheral blood parasites every 3 days with a
Neubauer cell, and mortality was recorded daily. For statis-
tical comparisons, the area under the curve of parasitemia
was calculated for 42 days of infection. Mice were sacrificed
at the end of the acute phase, after 50 days of infection. The
hearts were removed and processed for histopathologic
analysis of tissue damage, and quantification of T. cruzi
parasite burden as indicators of disease progression.
Plasmids construction and immunization
Plasmids based on the pcDNA3.1 plasmid vector (Invitro-
gen, USA) and encoding T. cruzi antigens TSA-1 (GenBank
accession no. M58466) and Tc24 (U70035) have been
described previously (Dumonteil et al., 2004). Plasmids
pIgSPclone9 (Boscardin et al., 2003) and p154/13 (Costa
et al., 1998) encode T. cruzi antigens ASP-2-like clone 9
(SPclone9, AY186572) and trans-sialidase (TS, D50685),
respectively, and are also based on the same plasmid vector.
Tc52 cDNA (AF117240) was digested with BamHI and
EcoRI to generate a 1900-bp fragment containing the full
FEMS Immunol Med Microbiol ]] (2007) 1–9c� 2007 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved
2 G. Sanchez-Burgos et al.
length gene and subcloned into pcDNA3.1 by standard
molecular biology protocols. We also included in our study
a plasmid encoding Leishmania donovani NH36 (Aguilar-Be
et al., 2005) as an additional control for the specificity of the
therapy. All plasmid DNAs were prepared using BIO-RAD
Maxi-Prep kit (BIO-RAD, USA) and stored at � 20 1C until
use.
Infected mice were treated with two doses of plasmid
DNA during the acute phase, at days 5 and 12 postinfection
(Dumonteil et al., 2004). Although these times may be
of limited practical usefulness, they represent an appro-
priate model for the rapid evaluation of vaccine candidates.
Mice were anesthetized with pentobarbital and injected in
the tibialis anterioris with 20 mg DNA and 45 mg of alumi-
num phosphate as adjuvant (Ulmer et al., 1999; Rosado-
Vallado et al., 2005). Control groups of mice received
20 mg of empty pcDNA3.1 plasmid with adjuvant or saline
solution.
Histopathologic analysis
Surviving mice were sacrificed after 50 days of infection and
hearts were removed for histopathologic analysis. Samples
were fixed in 10% formaldehyde and included in paraffin.
Five-micrometer sections were then stained with hematox-
ylin and eosin, and examined for the presence of inflamma-
tion and parasites with a Nikon Eclipse E600 optical
microscope at � 10 magnification. Inflammation was
quantified by image analysis from four to 10 digital
micrographs per animal using Multispec 3.0 (Purdue Uni-
versity, IN). Pixels corresponding to inflammatory cell
nuclei were quantified to estimate the number of inflamma-
tory cells per area of muscle fiber (Zapata-Estrella et al.,
2006).
Trypanosoma cruzi detection andsemiquantitation
Semiquantitation of parasite DNA was performed by com-
petitive PCR (Roberts et al., 2000; Zapata-Estrella et al.,
2006). Briefly, a parasite-specific 90-bp sequence of the
b-tubulin gene was amplified from 100 ng DNA from
dissected cardiac tissue using the following primers: forward
50-ACGTTCGGTGACCTGAACCA-30 and reverse: 50-CAG
GTCAGAGTTCAGCTGGC-30. PCR amplification was per-
formed in the presence of serial dilutions of a competing
70-bp synthetic oligonucleotide: 50-ACGTTCGGTGACCT
GAACCAGCGTCCAGCCGTTCGTGGCTGTCCAGTCCG
GCCAGCTGAACTCTGACCTGC. The amount of T. cruzi
DNA was estimated by comparing band intensities of
T. cruzi and competitor amplicons (Roberts et al., 2000;
Zapata-Estrella et al., 2006).
Statistical analysis
Comparisons between treatment groups was performed
using ANOVA, and followed, when significant, by Tukey’s post
hoc test to identify the significantly different groups. The
Log rank test of Kaplan–Meier survival curves was per-
formed to assess differences in survival between groups.
Correlation analysis was performed to evaluate the relation-
ship of some variables between the different vaccine groups.
All tests were performed using JMP 5.0 software (SAS
Institute, Cary, NC).
Results
To initially evaluate the efficacy of therapeutic vaccination
encoding various T. cruzi antigens to reduce pathology,
outbred ICR mice were infected with a sublethal dose of
500 blood trypomastigotes, and treated with two doses of
20 mg of DNA vaccines encoding the selected antigens, at
days 5 and 12 postinfection. The time course of the
parasitemia of infected and treated mice was monitored
during the acute phase of the infection (Fig. 1a and b) and
the area under the curve was calculated for statistical
comparisons (Fig. 1c). As expected, mice treated with saline
solution or empty plasmid DNA developed very high
parasitemia (Fig. 1a and c). Similarly, the parasitemia was
unaffected in mice treated with plasmid DNA encoding the
heterologous antigen NH36 from Leishmania donovani (not
shown). On the other hand, mice treated with the T. cruzi
DNA vaccines presented various profiles of parasitemia,
depending on the encoded antigen. Mice treated with
pIgSPclone9, TS (p154/13) or a combination of both
plasmids presented parasitemia not significantly different
for that of control mice (Fig. 1b and c), whereas mice treated
with TSA-1, Tc52 or Tc24 DNA presented significant
reductions in their parasitemia compared with controls
(Fig. 1a and c,ANOVA F = 5.04, Po 0.001, Tukey: Po 0.05).
The survival of mice during the acute phase was also
significantly different depending on the treatment. As
shown in Fig. 2, mice treated with plasmids encoding
L. donovani NH36, TS or ASP-2-like clone 9 presented low
survival rates at 50 days postinfection, similar to that of
control mice treated with saline or empty vector (Kaplan–
Meier survival analysis, P4 0.05). Similarly, the survival of
mice treated with a combination of both pIgSPclone9 and
p154/13 plasmids was not significantly different from the
survival of control mice (P = 0.22). On the other hand,
therapeutic vaccination with plasmid DNA encoding Tc24,
TSA-1 and Tc52, respectively, resulted in significant in-
creases in the survival of treated mice (Po 0.05). There
was an overall significant inverse correlation between para-
sitemia (taken as the average area under the curve for each
group) and survival rate at 50 days postinfection (r2 = 0.78,
FEMS Immunol Med Microbiol ]] (2007) 1–9 c� 2007 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved
3Trypanosoma cruzi therapeutic DNA vaccine
P = 0.003), with the higher survival rate being found in the
groups of mice presenting lower parasitemia.
To evaluate in more detail the extent of the control of
Chagas disease progression by the therapeutic vaccines, we
investigated tissue inflammation and parasite burden in the
hearts of treated mice. We used digital image analysis to
quantify inflammatory cell density in micrographs of
cardiac tissue sections. Significant differences were observed
between treatments (ANOVA F = 12.03, Po 0.001). At 50 days
postinfection, the hearts of control mice presented an
intense diffuse inflammatory reaction (Fig. 3a and b),
characterized by a high density of inflammatory cells (Fig.
4). Treatment with a combination of pIgSPclone 9 and
p154/13 plasmids did not prevent tissue inflammation (Figs
3c and 4). Similarly, treatment with pcDNA3-Tc52 did not
significantly affect the overall inflammatory cell density
(Figs 3d and 4). Only treatments with TSA-1 and Tc24
DNA vaccines were able to significantly reduce cardiac tissue
inflammation (Fig. 4, Tukey: Po 0.05), and this was mostly
focal (Fig. 3e and f).
Examination of parasite burden in the heart by semi-
quantitative PCR further showed that treatment with a
combination of pIgSPclone9 and p154/13 plasmids had no
significant effect on parasite burden, although it was slightly
decreased. On the other hand, treatment with plasmid
encoding the antigens TSA-1, Tc52 and Tc24 significantly
reduced T. cruzi parasite burden by about 2–3 log (ANOVA
F = 6.02, P = 0.001, Tukey: Po 0.05). Overall, there was a
significant positive correlation between parasite burden and
the density of inflammatory cells (r2 = 0.62, P = 0.03). An
increased survival was also correlated with a lower parasite
burden (r2 = 0.84, P = 0.009) but not with tissue inflamma-
tion (P = 0.13). Taken together, these results demonstrate
that DNA vaccines encoding antigens Tc24, TSA-1 and Tc52
can clearly reduce Chagas disease development at 50 days
postinfection.
Discussion
The present comparative evaluation of therapeutic DNA
vaccines against T. cruzi infection demonstrates that efficacy
is critically dependent on the antigen encoded. Our data first
show that parasite-specific antigens are required as a vaccine
encoding a Leishmania donovani antigen, otherwise very
effective against Leishmania ssp. (Aguilar-Be et al., 2005),
was completely ineffective for T. cruzi therapy. This observa-
tion and the fact that the vector alone had negligible efficacy
indicate that a nonspecific adjuvant-like effect of the DNA
vaccine can be ruled out. Strain-specific polymorphism of
the antigens may have also influenced the efficacy of the
Fig. 1. Effect of therapeutic vaccination on
T. cruzi parasitemia. Mice were infected with
500 blood trypomastigotes and the time course
of their parasitemia was monitored by counting
peripheral blood parasites every 3 days with a
Neubauer cell, for up to 50 days postinfection
(a and b). Error bars have been omitted for
clarity, and the saline group is repeated for easier
comparison. Overall parasitemia was calculated
as the area under the curve (c). Groups of
mice were treated at days 5 and 12 with the
indicated DNA vaccines. Data are presented as
mean� SEM of 12–18 mice per group from
three separate experiments. �A significant
difference with the saline group. # A significant
difference with the pcDNA3 control group.
FEMS Immunol Med Microbiol ]] (2007) 1–9c� 2007 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved
4 G. Sanchez-Burgos et al.
DNA vaccines tested here and this is a growing concern in
vaccine development (Urwin et al., 2004; Kumkhaek et al.,
2005), as some polymorphisms of T-cell restricted epitopes
have been described, in particular for TS antigens (Martin
et al., 2006), and we did not use antigen sequences derived
from the same strain used for experimental infection.
However, it is of key importance to identify antigens
sufficiently conserved to allow for the induction of a
protective/therapeutic immunity against most if not all
T. cruzi strains, and further studies would be required to
assess vaccine efficacy against different parasite strains.
Alternatively, differences in the level of protein expression
from the different plasmids may have affected their efficacy.
This is, however, unlikely because all the vaccines were based
on the same plasmid backbone and very similar levels of
expression can thus be expected.
The lack of therapeutic efficacy of DNA vaccines encoding
ASP-2-like and TS antigens was unexpected given the high
protective efficacy of these antigens when used as prophy-
lactic vaccines (Costa et al., 1998; Boscardin et al., 2003).
Even treatment with a combination of plasmids encoding
these two antigens, which could have been expected to
provide an improved efficacy compared with the respective
antigens alone, was unable to control disease progression.
Rather, this combination of vaccines mimicked the treat-
ment with ASP-2-like DNA alone, suggesting that this
antigen may be immunodominant over TS. The contrast
between the prophylactic and therapeutic efficacy of these
vaccines may be due to differences in immunogenicity
towards different strains of parasites as mentioned above,
but may also be due to differences in plasmid doses and
immunization protocols. Indeed, previous prophylactic stu-
dies used a higher plasmid dose and cardiotoxin pretreat-
ment (Costa et al., 1998; Boscardin et al., 2003), which is
known to increase vaccine efficacy.
On the other hand, Tc24, TSA-1 and Tc52 DNA vaccines
provided a significant control of disease progression, as
evidenced by a reduction in parasitemia, mortality and
cardiac tissue inflammation. We also show for the first time
that treatment with these vaccines significantly reduced
parasite burden in cardiac tissue. The contrasting therapeu-
tic efficacy of trypomastigote-specific antigens TSA-1 and
TS, which both belong to the trans-sialidase family of
proteins, may be related to their rather low sequence
similarity (27% amino acid identity and 55% similarity),
resulting in distinct T-cell epitopes (Taibi et al., 1993;
Wrightsman et al., 1994; Wizel et al., 1998; Rodrigues et al.,
1999). Also, some epitopes may be shared or not within this
extremely large family of proteins of over 1400 members
(El-Sayed et al., 2005), and thus cause potential cross-
reaction with other trans-sialidases in the case of TSA-1.
Tc24 DNA seemed to induce the best therapeutic effect as
it was able to induce strong reductions in all the parameters
measured to evaluate disease progression. As this antigen is
present in all developmental stages of T. cruzi (Ouaissi et al.,
1992; Taibi et al., 1993), it may target both circulating and
intracellular parasites, which may explain this higher effi-
cacy in controlling disease progression. In this respect, the
efficacy of Tc52 DNA vaccine may thus be related to the low
but significant expression of this antigen in trypomastigotes
in addition to its elevated expression in amastigotes. Taken
together, these results suggest that efficacy of T. cruzi
therapeutic vaccines may be related, in part, to their devel-
opmental stage-specificity, and constitutive antigens such as
Tc24 that make it possible to target both circulating and
intracellular parasites may represent better candidates. Test-
ing of additional antigens should help clarify this point.
Alternatively, the efficacy of Tc52 may be related to the fact
that it is an excreted/secreted protein that is released from
the parasite (Fernandez-Gomez et al., 1998), and has a
potent immunomodulatory activity (Ouaissi et al., 2002).
Indeed, this antigen has been proposed as a virulence factor
as the targeted deletion of this gene reduced the pathogeni-
city of the mutant parasites (Garzon et al., 2003).
Finally, the observation of a significant correlation be-
tween parasite burden and inflammatory cell density in
cardiac tissue agrees with the growing amount of evidence
indicating that parasite presence and persistence results in
Fig. 2. Effect of therapeutic vaccination on survival. Mice were infected
with 500 blood trypomastigotes and treated on days 5 and 12 with the
indicated DNA vaccines. The time course of their survival rate is shown
and the saline group is repeated for easier comparison. Data are
presented for 12–18 mice per group from three separate experiments.�A significant difference with the saline group. #A significant difference
with the pcDNA3 control group (Log rank test).
FEMS Immunol Med Microbiol ]] (2007) 1–9 c� 2007 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved
5Trypanosoma cruzi therapeutic DNA vaccine
chronic inflammatory reactivity (Zhang & Tarleton, 1999;
Monteon-Padilla et al., 2001). This strengthens the relevance
of targeting the parasite for the control of Chagas disease, as
decreased parasite burden may imply a better prognosis
during chronic infection (Bhatia & Garg, 2005), and provide
additional support for the concept of therapeutic
Fig. 3. Effect of therapeutic vaccination on cardiac tissue damage. After 50 days of infection, treated mice were sacrificed and their hearts were
removed, fixed, and included in paraffin. Sections were stained with hematoxylin and eosin and observed at �10 magnification. Representative
micrographs of tissue sections from infected mice treated with saline solution (a); empty plasmid vector (b); a combination of pIgSPClone9 and p154/13
DNA vaccines (c); Tc52 (d); TSA-1 (e); and Tc24 (f) DNA vaccines are shown.
FEMS Immunol Med Microbiol ]] (2007) 1–9c� 2007 Federation of European Microbiological SocietiesPublished by Blackwell Publishing Ltd. All rights reserved
6 G. Sanchez-Burgos et al.
vaccination aimed at reducing cardiac tissue damage. Also,
the present study was limited to an acute phase model, and it
would be important to confirm the present results when
treatment is given during the chronic phase, when novel
treatments are most needed. We previously showed that
therapeutic administration of DNA encoding TSA-1
remains effective during the chronic phase (Dumonteil
et al., 2004; Zapata-Estrella et al., 2006), but the therapeutic
potential of other antigens at this stage remains to be
optimized.
In conclusion, we show here that treatment with DNA
vaccines encoding Tc52, Tc24 and TSA-1 antigens is able to
reduce parasitemia, mortality, cardiac tissue inflammation
and parasite burden during acute T. cruzi infection in mice,
indicating a significant control of disease progression. These
results warrant further studies of these therapeutic DNA
vaccines and of the immune mechanisms that underly their
efficacy, and confirm the potential of this strategy as a
promising alternative or complement to conventional che-
motherapy for the control of Chagas disease.
Acknowledgements
This work was funded by a Albert Sezary research prize from
the Academie Nationale de Medecine, Paris, France, and
grant #SEP-2004-C01-47122 from CONACYT to ED, and by
grants from Fundacao de Amparo a Pesquisa do Estado de
Sao Paulo, The Millennium Institute for Vaccine Develop-
ment and Technology (CNPq – 420067/2005-1) and The
Millennium Institute for Gene Therapy to MMR.
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9Trypanosoma cruzi therapeutic DNA vaccine