Biological role of surface Toxoplasma gondii antigen in development of vaccine.
OBJECTIVE
To analyze the biological role of the surface antigen of Toxoplasma gondii (T gondii) in development of vaccine.


METHODS
The surface antigen of T gondii (SAG1) was expressed in vitro. The immune response of the host to the antigen was investigated by detection of specific antibody reaction to SAG1 and production of cytokines. Mice were immunized with recombinant SAG1 and challenged with lethal strain of T gondii RH. The monoclonal antibody to r-SAG1 was prepared and used to study the effects of SAG1 on T gondii tachyzoites under electromicroscope.


RESULTS
The mice immunized with recombinant SAG1 delayed death for 60 h compared to the control group. The recombinant SAG1 induced specific high titer of IgG and IgM antibodies as well as IFN-gamma, IL-2 and IL-4 cytokines in mice. In contrast, IL-12, IL-6 and TNF-alpha were undetectable. When T gondii tachyzoites were treated with the monoclonal antibody to r-SAG1, the parasites were gathered together, destroyed, deformed, swollen, and holes and gaps formed on the surface.


CONCLUSIONS
SAG1 may be an excellent vaccine candidate against T gondii. The immune protection induced by SAG1 against T gondii may be regulated by both hormone- and cell-mediated immune response.
Liu
Ke-Yi
KY
Shandong Institute of Parasitic Diseases, Jining Taibai Zhong Road #11, Jining 272033, Shandong Province, China. keyiliu2003@yahoo.com
Zhang
Dian-Bo
DB
Wei
Qing-Kuan
QK
Li
Jin
J
Li
Gui-Ping
GP
Yu
Jin-Zhi
JZ