HSP20 PROTEIN FROM TOXOPLASMA GONDII GENERATES PROTECTION IN A MURINE MODEL OF CHRONIC TOXOPLASMOSIS

MARIANO SERGIO PICCHIO, NADIA ARCÓN, VANESA ROXANA SANCHEZ, IGNACIO MARTÍN FENOY, ARIADNA SOLEDAD SOTO, MARIA DE LOS ÁNGELES ALDIRICO, MATÍAS DAMIÁN PERRONE SIBILIA, ROSALÍA MORETTA, ALEJANDRA GOLDMAN, VALENTINA MARTIN

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

Toxoplasmagondii is anintracellular protozoan with a worldwideprevalence in human and animal populations. No vaccine is currently available, so the design ofefficient vaccine strategies is still atopical question. The T. gondiisurface chaperone Hsp20 appears asa possible candidate to beincluded in the development of a preventivevaccine, since it is recognized byalmost 80% of sera from seropositive individuals and also, anti-Hsp20antibodies are able to block in vitro parasite motility and hostcell invasion. In the present work, we studied the immune responseand protective effect of rHsp20 in C57BL/6 mice, a strain highly susceptible toToxoplasma infection. Mice wereimmunized 3 times with 15 day-intervals with rHsp20 alone (20μg/dose) by intranasal (rHsp20 IN) or intradermal route(rHsp20 ID), or combined with Alum (rHsp20 ID+Alum) or complete Freund´sadjuvant (rHsp20 ID+ACF). Naive mice were used for the control group (Control).Two weeks after last immunization, mice were orally challenged with anon-lethal dose of tissue cysts of the ME49 strain. One month later, cysts werecounted in the brain of infected mice and a significant decrease in parasiteload was observed only in the group vaccinated with rHsp20+ACF (p<0,05). Allgroups vaccinated by the intradermal route elicited an antigen-specific systemichumoral response. However, protection in the rHsp20+ACF group correlated withthe induction of both,  a strong humoralresponse with a Th1/Th2 mixed profile and also a cellular responsecharacterized by significant levels of antigen-specific proliferation of andcytokine production (IFN-γ, IL-10 and IL-4) after in vitro stimulation with the antigen.No systemic responses could be detected in the intranasal vaccinated mice. Ourfindings demonstrate that even rHsp20 is a good antigen able to elicit highlevels of specific antibodies, protection is achieved only when cellularspecific responses are also induced. So we postulate Hsp20 as a good candidateto be used in a vaccine formulation