TOWARDS A VACCINE TO PREVENT TOXOPLASMOSIS
Animal Parasitic Diseases
2013 Annual Report
1a.Objectives (from AD-416):
Develop an integrated risk model for toxoplasma in the U.S. pork industry.
1b.Approach (from AD-416):
Will test various drug or vaccine candidates in mice experimentally-infected with Toxoplasma strains of different genotypes.
This is a multi-institutional five-year agreement funded through National Institutes of Health. The main objective is to develop a protective vaccine for Toxoplasma. Mice are generally used to test the protective efficacy of vaccines because they are susceptible, reagents are available to measure immune parameters, in mice, and they are easily managed in the laboratory. In the present study, we developed a robust oocyst challenge model to study protective immunity in transgenic HLA mice. This oocyst mouse model was used to study efficacy of adjuvants and different vaccine candidates. Entrapment of antigenic peptides in NISV adjuvant system has proven problematic, likely due to solubility and charge of many of these peptides. Consequently we are now moving to use of longer proteins which will circumvent these issues. However, a number of these peptides that we were able to entrap in NISV sufficiently well were tested in the transgenic mice which were challenged with oocysts. Very minimal, if any, protection was observed in these experiments. However what little protection noted was associated with increased KLRG expression on CD8 T cells. Experiments have demonstrated that immunization with the T. gondii protein GRA6 gene can mediate protection against challenge with a type 2 strain of T. gondii in HLA-A11 mice but not A2 mice. This protection measured as reduced parasite number is evident through an in vivo imaging system (IVIS). Flow cytometry analysis demonstrates that protection is associated with induction of TNF-alpha and IFN-gamma producing CD8+ T cells. Further work has cloned additional T. gondii genes for vaccine studies and optimized entrapment of protein into bilosomes for oral delivery studies.