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

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

Toxoplasma gondii is an intracellular protozoan with a worldwideprevalence in human and animal populations. No vaccine iscurrently available for use in humans or food producing animals. TheT. gondii surface chaperone Hsp20 appears as a possible candidateto be included in the development of a preventive vaccine, since it isrecognized by almost 80% of sera from seropositive individuals andalso, anti-Hsp20 antibodies are able to block in vitro parasite motilityand host cell invasion. In the present work, we studied the immuneresponse and protective effect of rHsp20 in C57BL/6 mice, a strainhighly susceptible to Toxoplasma infection. Mice were immunized3 times with 15 day-intervals with rHsp20 alone (20μg/dose) by intranasal(rHsp20 IN) or intradermal route (rHsp20 ID), or combinedwith Alum (rHsp20 ID+Alum) or complete Freund´s adjuvant (rHsp20ID+ACF). Naive mice were used for the control group (Control). Twoweeks after last immunization, mice were orally challenged with anon-lethal dose of tissue cysts of the ME49 strain. One month later,cysts were counted in the brain of infected mice and a significantdecrease in parasite load was observed only in the group vaccinatedwith rHsp20+ACF. All groups vaccinated by the intradermal routeelicited an antigen-specific systemic humoral response. However,protection in the rHsp20+ACF group correlated with the inductionof both, a strong humoral response with a Th1/Th2 mixed profile and also a cellular response characterized by significant levels ofantigen-specific proliferation of and cytokine production (IFN-γ, IL-10 and IL-4) after in vitro stimulation with the antigen. No systemicresponses could be detected in the intranasal vaccinated mice. Ourfindings demonstrate that even rHsp20 is a good antigen able toelicit high levels of specific antibodies, protection is achieved onlywhen cellular specific responses are also induced. So we postulateHsp20 as a good candidate to be used in a vaccine formulation