17 research outputs found
Immune protection against Trypanosoma cruzi induced by TcVac4 in a canine model
Chagas disease, caused by Trypanosoma cruzi, is endemic in southern parts of the American continent. Herein, we have tested the protective efficacy of a DNA-prime/T. rangeli-boost (TcVac4) vaccine in a dog (Canis familiaris) model. Dogs were immunized with two-doses of DNA vaccine (pcDNA3.1 encoding TcG1, TcG2, and TcG4 antigens plus IL-12- and GMCSF- encoding plasmids) followed by two doses of glutaraldehyde-inactivated T. rangeli epimastigotes (TrIE); and challenged with highly pathogenic T. cruzi (SylvioX10/4) isolate. Dogs given TrIE or empty pcDNA3.1 were used as controls. We monitored post-vaccination and post-challenge infection antibody response by an ELISA, parasitemia by blood analysis and xenodiagnosis, and heart function by electrocardiography. Post-mortem anatomic and pathologic evaluation of the heart was conducted. TcVac4 induced a strong IgG response (IgG2>IgG1) that was significantly expanded post-infection, and moved to a nearly balanced IgG2/IgG1 response in chronic phase. In comparison, dogs given TrIE or empty plasmid DNA only developed high IgG titers with IgG2 predominance in response to T. cruzi infection. Blood parasitemia, tissue parasite foci, parasite transmission to triatomines, electrocardiographic abnormalities were significantly lower in TcVac4-vaccinated dogs than was observed in dogs given TrIE or empty plasmid DNA only. Macroscopic and microscopic alterations, the hallmarks of chronic Chagas disease, were significantly decreased in the myocardium of TcVac4-vaccinated dogs.We conclude that TcVac4 induced immunity was beneficial in providing resistance to T. cruzi infection, evidenced by control of chronic pathology of the heart and preservation of cardiac function in dogs. Additionally, TcVac4 vaccination decreased the transmission of parasites from vaccinated/infected animals to triatomines.CONACYT PROY No. 156701 UAEM PROY No. 2381/2006U National Institutes of Health/National Institute of Allergy and Infectious Diseases http://www.niaid.nih.gov/Pages/ default.aspx GRANT NUMBER (AI072538) NJG; American Heart Association http://www.heart.org/ HEARTORG/ GRANT NUMBER (0855059F) to NJG
Testing the Efficacy of a Multi-Component DNA-Prime/DNA-Boost Vaccine against Trypanosoma cruzi Infection in Dogs
Immunization of dogs with DNA-prime/DNA-boost vaccine (TcVac1) enhanced the
Trypanosoma cruzi-specific type 1 antibody and
CD8+ T cell responses that resulted in an early control of
acute parasitemia and a moderate decline in pathological symptoms during chronic
phase. Further improvement of vaccine-induced immunity would be required to
achieve clinical and epidemiological benefits and prevent transmission of
parasites from vaccinated/infected dogs to triatomines
Immune protection against Trypanosoma cruzi induced by TcVac4 in a canine model.
Chagas disease, caused by Trypanosoma cruzi, is endemic in southern parts of the American continent. Herein, we have tested the protective efficacy of a DNA-prime/T. rangeli-boost (TcVac4) vaccine in a dog (Canis familiaris) model. Dogs were immunized with two-doses of DNA vaccine (pcDNA3.1 encoding TcG1, TcG2, and TcG4 antigens plus IL-12- and GM-CSF-encoding plasmids) followed by two doses of glutaraldehyde-inactivated T. rangeli epimastigotes (TrIE); and challenged with highly pathogenic T. cruzi (SylvioX10/4) isolate. Dogs given TrIE or empty pcDNA3.1 were used as controls. We monitored post-vaccination and post-challenge infection antibody response by an ELISA, parasitemia by blood analysis and xenodiagnosis, and heart function by electrocardiography. Post-mortem anatomic and pathologic evaluation of the heart was conducted. TcVac4 induced a strong IgG response (IgG2>IgG1) that was significantly expanded post-infection, and moved to a nearly balanced IgG2/IgG1 response in chronic phase. In comparison, dogs given TrIE or empty plasmid DNA only developed high IgG titers with IgG2 predominance in response to T. cruzi infection. Blood parasitemia, tissue parasite foci, parasite transmission to triatomines, electrocardiographic abnormalities were significantly lower in TcVac4-vaccinated dogs than was observed in dogs given TrIE or empty plasmid DNA only. Macroscopic and microscopic alterations, the hallmarks of chronic Chagas disease, were significantly decreased in the myocardium of TcVac4-vaccinated dogs. We conclude that TcVac4 induced immunity was beneficial in providing resistance to T. cruzi infection, evidenced by control of chronic pathology of the heart and preservation of cardiac function in dogs. Additionally, TcVac4 vaccination decreased the transmission of parasites from vaccinated/infected animals to triatomines
T cell and cytokine response in vaccinated dogs.
<p>(<b>A</b>) Spleen cells were obtained from vaccinated and
non-vaccinated dogs at one year after challenge infection with <i>T.
cruzi</i>. Spleen cells were incubated for 30 min with
FITC-conjugated anti-CD8 and PE-conjugated anti-CD4 antibodies and
CD4<sup>+</sup> and CD8<sup>+</sup> T cell subsets monitored
by flow cytometry. (<b>B</b>) The circulatory IFN-γ level was
measured by an ELISA. Data are presented as mean ± SD
(*<i>p</i><0.05).</p
Morphological alterations in the heart.
<p>Dogs were vaccinated and infected with <i>T. cruzi</i> as above.
Shown are representative morphologic alterations of the heart during the
acute infection phase (60 dpi) in dogs injected with vector only
(<b>B&B1</b>) or immunized with TcVac1
(<b>C&C1</b>). Images of normal heart (<b>A&A1</b>) are
shown for comparison. Horizontal arrows show right ventricle wall thinning
characteristic of ventricle dilation. Vertical arrows show pale striated
epicardium and myocardium, characteristic of necrosis produced after
inflammatory response to infection.</p
The antibody response to <i>T. cruzi</i> infection was polarized to type 1 in vaccinated dogs.
<p>Dogs were vaccinated as above, and infected with <i>T. cruzi</i>.
An ELISA was performed to evaluate sera levels (1∶100-dilution) of
<i>T. cruzi</i>-specific IgM (<b>A</b>), IgG
(<b>B</b>), IgG1 (<b>C</b>), and IgG2 (<b>D</b>)
antibodies at 0, 15, 30, 45, and 60 days post-infection.</p
TcVac1-induced antibody response in dogs.
<p>Dogs were vaccinated with TcVac1 or injected with vector only, and sera were
collected two weeks after each immunization dose. An ELISA was performed to
monitor the sera levels (1∶50 dilution) of parasite-specific IgM
(<b>A</b>), IgG (<b>B</b>), IgG1 (<b>C</b>) and IgG2
(<b>D</b>). The vaccine-induced antigen-specific (TcG1, TcG2 and
TcG4) antibody response in sera collected 14 days after last dose of vaccine
was determined using recombinant antigens. Data are presented as mean
± SD (*<i>p</i><0.05, vaccinated versus
non-vaccinated, n = 6 per experiment).</p
Histological analysis of hearts.
<p>Dogs were vaccinated, and challenged with <i>T. cruzi</i>. Heart
tissue sections (5-ìM) from left ventricle, septum, and right
ventricle were obtained at 60 days post-infection (acute phase), and stained
with hematoxylin-eosin. Shown are representative micrographs of dogs
injected with vector only (<b>B,B1,B2</b>) or immunized with TcVac1
(<b>C,C1,C2</b>). Micrographs from normal/uninfected dogs
(<b>A,A1,A2</b>) are shown for comparison. Vertical arrows show
amastigote nests and horizontal arrows show lymphocyte infiltration, and
cardiomyocytes destruction.</p
Shown are plasma levels of myeloperoxidase activity (A) and nitrite content (B) in dogs immunized with vector only or TcVac1 vaccine during the course of 0–60 days post-infection.
<p>Data are presented as mean ± SD (*<i>p</i><0.05).</p
Figure 5
<p>(<b>A</b>) Blood parasitemia was determined by light microscopy. Data
are presented as mean ± SD (*<i>p</i><0.05).
(<b>B</b>) Percent survival from infection.</p