Evaluation of the Small Heat Shock Protein-20 as a new vaccine candidate in an experimental murine model of toxoplasmosis

PICCHIO M, SÁNCHEZ V, FENOY I, ARCÓN N, SOTO A., GOLDMAN A, MARTIN V

Buenos Aires

Congreso; XXVII Reunión Annual de la Sociedad Argentina de Protozoología.; 2015

SAP

The development of vaccines against T. gondii infection is a high priority, given the high rate ofinfection close to30% of the world population. Currently,the only available commercialvaccine is Toxovax®, basedon live attenuated tachyzoites, used in the United Kingdom, New Zealand, France and Ireland. The parasite surface chaperone Hsp20appears as a possible candidate to be included in the development of a preventive vaccine against toxoplasmosis, since it was recognized for almost 80% of serafrom seropositive individuals andalso, anti-Hsp20antibodies are able to block in vitro parasite motility and hostcell invasion. In the presentwork we have studied the immuno-protectiveeffect of a recombinant form of Hsp20 (rHsp20) in a mouse model of chronic T. gondii infection.CF1 mice wereimmunized 4 times every 15days with rHsp20 (20 ug/dose) combinedwith Alum (0.5 mg/dose) and the formulation was administeredintradermally (ID) or intramuscularly (IM).Both ID andIM vaccinations induced strong humoral responses characterized by high levels of IgG antibodies,showing a mixed TH1 / TH2 profile inboth experimental groups. In order to assess the inmunoprotective value of this vaccine, two weeks after the vaccination schedule was completed, theimmunized mice were challenged intragastrically with a non-lethal dose of tissue cysts of the ME49 T. gondii strain. One month after the challenge, rHsp20 ID immunized mice showeda significant reduction of 70% inthe brain parasite bruden compared to the controlgroup, while the groupimmunized via IM route showed atendency to decrease the parasite load (20 % reduction). Theseresults demonstrate that Hsp20 wouldbe a very good candidate to beincluded in a vaccine againsttoxoplasmosis given the high degree of protection observed in this mouse model.