Study On Immune Response Of Swine After Immunized With Toxoplasma Gondii Excretory/secretory Antigen

Toxoplasma gondii is an obligate intracellular protozoan parasite and widespread in the world. Toxoplasmsis caused by T.gondii is a serious parasitic zoonosis and threats human health and the farming industry. So development of Toxoplasma gondii vaccine is an urgent task for toxoplasmsis control.To elucidate the immune mechanism of Toxoplasma gondii excreted/secreted antigens in swine,piglets were randomly divided into 6 groups of 5 each, named E/SA group, E/SA~+CpG group, E/SA~+CpG(unemulsification)group, E/SA~+IL-2 group, E/SA~+IL-2~+CpG group and control group. The animals were immunized for 2 times at 2 weeks interval and challenged with T. gondii GJS 2 weeks after the second vaccination. Blood samples were collected pre-immunization,week 2 and week 4 post- immunization, week 1 and week 2 post-challenge , respectively. The antibodies were tested by IHA ,and the IL-2, IL-4, IFN-γand TNF-αwere detected by ELISA.The dynamic changes of the CD4 ~+ and CD8 ~+ T lymphocyte subpopulations in peripheral blood were analyzed by the flow cytometry. The results showed that the levels of specific antibody in most piglets of immmunized group increased to 1:1024. The level of IL-2, IL-4 and IFN-γin serum of immunized groups increased , with the E/SA group increased significantly from 105.05, 105.33,67.50 pg/mL to 194.03,342.50,296.50 pg/mL,respectively.These were significantly different from the control group (P<0.05). The level of TNF-αdid not change significantly at all points time. The level of peripheral blood CD4 ~+, CD8 ~+ T lymphocyte in immuned group significantly increased compared with the control group,and the E/SA group increased significantly, from 21.51%,23.9% to 35.72%,32.8%, respectively. After challeng with T.gondii GJS strain, the immuned group and the control group had significant difference temperature, the piglets of immuned group had transient low-grade fever and normal appetite,the piglets of the control group had higher fever, loss of appetite and symptoms associated with diarrhea.These data indicated that T.gondii E/SA vaccine can promote the secretion of specific antibody and IL-2,IL-4,IFN-γin pigs , improve the percentage of peripheral CD4 ~+ and CD8~+ T lymphocytes , elevate the cellular immunity and the humoral immunity of swine,elicit the anti-T gondii immune response.