[Comparison of Immune Responses Elicited by Adjuvanted Tachyzoite Lysate Vaccines Developed from Two Different Toxoplasma gondii Strains Isolated in Turkey].
[congenital toxoplasmosis]
Toxoplasma gondii the causative agent of toxoplasmosis is an obligate intracellular parasite with a wide host range including all warm-blooded animals and birds. T.gondii infection causes congenital toxoplasmosis in newborns and this may lead to fetal anomalies, retinochoroiditis leading to blindness, lethal toxoplasmic encephalitis in immune compromised patients, and organ failure in transplantation patients. The pathogenesis of toxoplasmosis change due to differences in the specific immune response elicited by diverse T.gondii strains. The protective immunity against toxoplasmosis is conferred by cellular immune responses. In the present study, two different strains isolated from Turkey named T.gondii Ankara and Ege were used to evaluate the types of humoral and cellular immune responses elicited by adjuvanted tachyzoite protein vaccines in an animal model. In the study, 6-8 weeks old female BALB/c mice were used and six study groups (each contains three mice) were composed for vaccination. The first and second groups were vaccinated with T.gondii Ankara and Ege (TAnkPE and TEgePE, respectively) tacyhzoite lysates, the third and fourth groups were vaccinated by tacyhzoite lysates adjuvanted with Freund's adjuvant (TAnkPE-Freund; TEgePE-Freund, respectively). The fifth and sixth groups were vaccinated with PBS and Freund's adjuvant as controls. Immunization of the animals was performed two times at three weeks intervals. The serum samples were collected before vaccination and after each vaccination to determine the IgG response by Western blotting, and IgG1 and IgG2a responses by ELISA. To determine the cellular immune response, CD8/CD4 cell ratio, intracellular IFN-g and IL-4 levels were determined in stimulated spleen cells grown in cell culture systems by flow cytometry. Toxoplasma IgG antibodies were only detected in TAnkPE-Freund group. IgG1 and IgG2a responses did not increase in any vaccination groups and there was not any polarization towards IgG1 or IgG2a. There was no significant increase in CD8/CD4 ratio of stimulated spleen cells. IFN-g level was increased in only TAnkPE-Freund vaccination group, however IL-4 levels were increased in TAnkPE-Freund, TEgePE-Freund and TEgePE groups. Our data showed that TAnkPE-Freund vaccine led to increase in IgG and IFN-g responses in BALB/c mice, however, tachyzoite lysate vaccines developed in this study did not induce sufficient protective immune response against toxoplasmosis. Thus, use of specific immunogenic proteins must be taken into consideration in the future vaccine development studies against toxoplasmosis.
