PROTECCION INMUNE CONTRA Trypanosoma cruzi INDUCIDO POR LA VACUNA TCVAC1 MODELO MURINO DE USANDO EL PROTOCOL DE ELECTROPORACIÓN INTRADÉRMICA

Abstract

Trypanosoma cruzi, a parasitic protozoan, is the etiologic agent of Chagas disease. Chagas disease is the most common cause of congestive heart failure related deaths among young adults in the endemic areas of South and Central America and Mexico. It has also become an important health issue in the United States and Europe due to large scale migration of Latin Americans over the last few decades. No vaccines are currently available until now. In this study, we tested the vaccine efficacy of two antigen candidates against T. cruzi infection and disease in a mouse model. The use of TcVac1 (TcG2, TcG4, T cruzi antigen encoding plasmids, interleukin-12 [IL-12] and granulocyte-macrophage colony-stimulating factor [GMCSF] encoding plasmids as genetic adjuvants) anti T. cruzi candidate vaccine injected intramuscularly has been previously reported in mice with very encouraging results. Here we evaluated the comparative protection conferred by TcVac1 when administrated intramuscular (IM) versus an intradermal/electroporation (IDE) vaccination protocol. Twelve BALB/c mice per group were vaccinated four times fifteen days apart. Half the animals (n=6) from each treatment were sacrificed two weeks after the last immunization for pre-infection vaccine efficacy evaluation, and the second half (n=6) was sacrificed 60 days post-infection (dpi) with T.cruzi Trypomastigotes (Sylvio X10/4 strain). Immune response was assessed through anti-TcG2 and TcG4 T. cruzi antigens.TcVac1 induced a strong IgG response (IgG2b>IgG1) that was significantly expanded post-infection, and moved to a nearly balanced IgG2b/IgG1 response in chronic phase. High IgG titers with IgG2 predominance in response to T. cruzi infection specific serum antibodies with an Enzyme Linked Immunosorbent Assay (ELISA) and lymphocyte activation against the studied antigens was evaluated through a lymphocyte proliferation assay. We found that IDE induced significantly larger surges of IgG antibodies including subtypes IgG1, IgG2a and IgG2b, during the pre- and post-infection periods for the two antigens used in the experiment. The ratio of antibodies IgG2b/IgG1 was >1 for TcG2 antigen in the pre-infection period in both administration routes. However for the TcG4 antigen the ratios were opposite for animals belonging to different administration routes<1 for IDE and >1 for IM. During the post infection period for both treatments IgG2b/IgG1 ratio was always <1. Suggesting, as previously reported that a switch from Th1 to Th2 type immune response occurs in vaccinated/infected animals. During the Lymphocyte proliferation assays we observed that both antigens were able to induce lymphocyte proliferation during the pre-infection period. However, we observed that animals from the IDE group induced more proliferation than IM mice group when TcG4 was used to activate the cells, which was also observed during the post-infection phase of the experiment. No animals died due to infection, vaccinated mice appeared to have healthier status than the control animals.