Further analysis of protection induced by the rTgPI-1 vaccine against Toxoplasma gondii: characterization of the vaccine-induced immune responses in C57BL/6 mice

SANCHEZ V; RODRIGUEZ FM; FENOY IM; GONZALEZ COBIELLO PL; GOLDMAN A; MARTIN V

Congreso; First French Argentine Immunology Congress; 2010

Sociedad Arg. de Inmunologia, French Society of Immunology

We previously showed that the recombinant protein rTgPI-1 (PI) used as an immunogen, resulted a potent vaccine against toxoplasmosis in two mouse strains. Vaccination of highly susceptible C57BL/6 mice induced a reduction of 49% in the parasite load after an oral infection. This protection was achieved only when a prime-boost protocol combining intradermical (ID) and intranasal (IN) immunizations were used. This strategy that included Alum (A) ID and ODN-CpG (C) IN induced the elicitation of a Th1 specific humoral response. The present study was conducted to further characterize the cellular immune response generated by the PI-based protective vaccine. B6 mice were inoculated with 2 doses of [PI+A] ID and boosted with 2 doses of [PI+C] IN (G4) and the control groups received 4 doses of [PI+C] IN (G3) or [PI+A] ID (G2) or 2 [A]id + 2 [PI+C] IN (G5) or 2 [PI+A]ID + [C]IN (G6) and a naïve control group was also included (G1). Two weeks after the last inoculation, some groups of animals were sacrificed for in vitro splenocyte culture studies (G1-4). After 5 days of in vitro PI stimulation, only G4 showed a significant lymphoproliferative response (Δcpm G4:24813±4209 vs G1:94±1,3a), and a significant increment in both CD4+ (absolute cell number G4:169667±28312 vs. G1:62550±1703a) and CD8+ lymphocytes (G4:92767±16372 vs. G1: 30300±462a) as measured by flow-cytometry. In order to test if both id and in administration of PI (G4) was necessary for protection, a challenge assay was performed including control G1, G5 and G6 groups. We observed that only G4 mice presented a significant brain parasite load reduction (G4:562±131 vs. G1:1910±153b) with an in vivo specific cellular response measured by a DTH assay (mm G4:0,089±0,016 vs. G1:0,031±0,009a) (Data: mean±SEM; ap<0.05; bp<0.01). These results indicate that this PI-based protective immunization strategy, in which PI is administrated by both the ID and IN routes, elicited a humoral and also a strong cellular immune response