Vertical toxoplasmosis in a murine model, protection after immunization with antigens of Toxoplasma gondii incorporated into liposomes

Distinct Toxoplasma gondii antigens were entrapped within liposomes and eva luated for their ability to protect Balb/c mice against congenital transmis sion: soluble tachyzoite antigen (L/STAg), soluble tissue cyst antigen (L/S TCAg) or purified 32kDa antigen of tachyzoite (L/pTAg). Soluble tachyzoite antigen alone in PBS (STAg) or emulsified in Freund's Complete Adjuvant (FC A/STAg) was also evaluated. Dams were inoculated subcutaneously with these antigens 6, 4 and 2 weeks prior to a challenge with four tissue cysts of th e P strain of T. gondii orally between 10 and 14 days of pregnancy. Signifi cant diminution differences were observed between the frequency of infected pups born of the dams immunized with the antigens incorporated into liposo mes and that of pups born of the dams immunized with antigen emulsified in FCA or non immunized group (P<0.05). There was a significant decrease in th e number of pups born dead in the groups L/STAg, L/SCAg and L/pTAg when com pared with pups from all other groups (p<0.05). All dams immunized with or without adjuvant showed an antibody response and a proliferation of T-cells . However, no correlation was found between immune response and protection against the challenge.