Perforin and gamma interferon expression are required for CD4+ and CD8+ T-cell-dependent protective immunity against a human parasite, Trypanosoma cruzi, elicited by heterologous plasmid DNA prime-recombinant adenovirus 5 boost vaccination

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Millennium Institute for Vaccine Development and Technology Millennium Institute for Gene Therapy Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) A heterologous prime-boost strategy using plasmid DNA, followed by replication-defective recombinant adenovirus 5, is being proposed as a powerful way to elicit CD4(+) and CD8(+) T-cell-mediated protective immunity against intracellular pathogens. We confirmed this concept and furthered existing research by providing evidence that the heterologous prime-boost regimen using the gene encoding amastigote surface protein 2 elicited CD4(+) and CD8(+) T-cell-mediated protective immunity (reduction of acute parasitemia and prolonged survival) against experimental infection with Trypanosoma cruzi. Protective immunity correlated with the presence of in vivo antigen-specific cytotoxic activity prior to challenge. Based on this, our second goal was to determine the outcome of infection after heterologous prime-boost immunization of perforin-deficient mice. These mice were highly susceptible to infection. A detailed analysis of the cell-mediated immune responses in immunized perforin-deficient mice showed an impaired gamma interferon (IFN-gamma) secretion by immune spleen cells upon restimulation in vitro with soluble recombinant antigen. in spite of a normal numeric expansion, specific CD8(+) T cells presented several functional defects detected in vivo (cytotoxicity) and in vitro (simultaneous expression of CD107a/IFN-gamma or IFN-gamma/tumor necrosis factor alpha) paralleled by a decreased expression of CD44 and KLRG-1. Our final goal was to determine the importance of IFN-gamma in the presence of highly cytotoxic T cells. Vaccinated IFN-gamma-deficient mice developed highly cytotoxic cells but failed to develop any protective immunity. Our study thus demonstrated a role for perforin and IFN-gamma in a number of T-cell-mediated effector functions and in the antiparasitic immunity generated by a heterologous plasmid DNA prime-adenovirus boost vaccination strategy. Universidade Federal de São Paulo, Escola Paulista Med, CINTERGEN, BR-04044010 São Paulo, Brazil Universidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol Imunol & Parasitol, BR-04044010 São Paulo, Brazil Univ Fed Rio de Janeiro, Inst Biofis Carlos Chagas Filho, Ctr Ciencias Saude, BR-21941 Rio de Janeiro, Brazil Fiocruz MS, Inst Oswaldo Cruz, Lab Biol Celular & Biol Interacoes, BR-21045900 Rio de Janeiro, Brazil Univ Fed Minas Gerais, Dept Bioquim & Imunol, Inst Ciencias Biol, BR-31270901 Belo Horizonte, MG, Brazil Fiocruz MS, Ctr Pesquisas Rene Rachou, BR-30190002 Belo Horizonte, MG, Brazil Univ Massachusetts, Sch Med, Dept Med, Div Infect Dis & Immunol, Worcester, MA 01605 USA Univ Fed Minas Gerais, Inst Ciencias Biol, Dept Microbiol, BR-31270901 Belo Horizonte, MG, Brazil Universidade Federal de São Paulo, Escola Paulista Med, CINTERGEN, BR-04044010 São Paulo, Brazil Universidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol Imunol & Parasitol, BR-04044010 São Paulo, Brazil FAPESP: 2006/1983-4 Millennium Institute for Vaccine Development and Technology: CNPq-420067/2005-1 FAPEMIG: EDT 24.000 Web of Science