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

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

The development of vaccines against T. gondii infection is a high priority, given the high rate of infection close to 30% of the world population. Currently, the only available commercial vaccine is Toxovax®, based on live attenuated tachyzoites, used in the United Kingdom, New Zealand, France and Ireland. The parasite surface chaperone Hsp20 appears as a possible candidate to be included in the development of a preventive vaccine against toxoplasmosis, since it was recognized for almost 80% of sera from seropositive individuals and also, anti-Hsp20 antibodies are able to block in vitro parasite motility and host cell invasion. In the present work we have studied the immuno-protective effect of a recombinant form of Hsp20 (rHsp20) in a mouse model of chronic T. gondii infection. CF1 mice were immunized 4 times every 15 days with rHsp20 (20 ug/dose) combined with Alum (0.5 mg/dose) and the formulation was administered intradermally (ID) or intramuscularly (IM). Both ID and IM vaccinations induced strong humoral responses characterized by high levels of IgG antibodies, showing a mixed TH1 / TH2 profile in both experimental groups. In order to assess the inmunoprotective value of this vaccine, two weeks after the vaccination schedule was completed, the immunized 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 showed a significant reduction of 70% in the brain parasite bruden compared to the control group, while the group immunized via IM route showed a tendency to decrease the parasite load (20 % reduction). These results demonstrate that Hsp20 would be a very good candidate to be included in a vaccine against toxoplasmosis given the high degree of protection observed in this mouse model.