Prophylactic efficacy of TcVac2 against Trypanosoma cruzi in mice.
BACKGROUND
Chagas disease is a major health problem in Latin America, and an emerging infectious disease in the US. Previously, we have screened the Trypanosoma cruzi sequence database by a computational/bioinformatics approach, and identified antigens that exhibited the characteristics of vaccine candidates.


METHODS
We investigated the protective efficacy of a multi-component DNA-prime/protein-boost vaccine (TcVac2) constituted of the selected candidates and cytokine (IL-12 and GM-CSF) expression plasmids in a murine model. C57BL/6 mice were immunized with antigen-encoding plasmids plus cytokine adjuvants, followed by recombinant proteins; and two-weeks later, challenged with T. cruzi trypomastigotes. ELISA and flow cytometry were employed to measure humoral (antibody isotypes) and cellular (lymphocyte proliferation, CD4(+) and CD8(+) T cell phenotype and cytokines) responses. Myocardial pathology was evaluated by H&E and Masson's trichrome staining.


RESULTS
TcVac2 induced a strong antigen-specific antibody response (IgG2b>IgG1) and a moderate level of lymphocyte proliferation in mice. Upon challenge infection, TcVac2-vaccinated mice expanded the IgG2b/IgG1 antibodies and elicited a substantial CD8(+) T cell response associated with type 1 cytokines (IFN-gamma and TNF-alpha) that resulted in control of acute parasite burden. During chronic phase, antibody response persisted, splenic activation of CD8(+) T cells and IFN-gamma/TNF-alpha cytokines subsided, and IL-4/IL-10 cytokines became dominant in vaccinated mice. The tissue parasitism, inflammation, and fibrosis in heart and skeletal muscle of TcVac2-vaccinated chronic mice were undetectable by histological techniques. In comparison, mice injected with vector or cytokines only responded to T. cruzi by elicitation of a mixed (type 1/type 2) antibody, T cell and cytokine response, and exhibited persistent parasite burden and immunopathology in the myocardium.


CONCLUSIONS
TcVac2-induced activation of type 1 antibody and lymphocyte responses provided resistance to acute T. cruzi infection, and consequently, prevented the evolution of chronic immunopathology associated with parasite persistence in chagasic hearts.
Gupta
Shivali
S
Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America.
Garg
Nisha Jain
NJ
D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D000953:Antigens, Protozoan / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D049109:Cell Proliferation; D014355:Chagas Disease / Q000276:immunology / Q000517:prevention & control*; D016207:Cytokines / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics / Q000276:immunology; D007117:Immunization, Secondary / Q000379:methods; D018664:Interleukin-12 / Q000235:genetics / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D009206:Myocardium / Q000473:pathology; D010957:Plasmids; D016052:Protozoan Vaccines / Q000008:administration & dosage / Q000276:immunology*; D014349:Trypanosoma cruzi / Q000276:immunology*; D014611:Vaccination / Q000379:methods; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000276:immunology*; D022223:Vaccines, Subunit / Q000008:administration & dosage / Q000276:immunology
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D016207:Cytokines; D016052:Protozoan Vaccines; D019444:Vaccines, DNA; D022223:Vaccines, Subunit; D018664:Interleukin-12; D016178:Granulocyte-Macrophage Colony-Stimulating Factor