Cell-Mediated Immune Mechanism(s) Of Equine Infectious Anemia Donkey Leucocyte-Attenuated Virus Vaccine

Equine infectious anemia Donkey leucocyte-attenuated virus vaccine (DLV) was the unique successful lentivirus vaccine, which has been applied extensively in China against EIA for twenty years, moreover, the morphological, genetic and serological relatedness between EIAV and HIV has increased interest in understanding the immune mechanism of DLV, which become the immune model of the HIV and other lentiviruses vaccine .We detect the kinetics of CD4+ and CD8+T lymphocyte subsets, lymphocyte proliferation and cytolytic activity of cytotoxic T lymphocyte in horse PBL with Flow cytometry (FCM) , lymphocyte proliferation assay(3[H]-TDR incorporation) and cytotoxic T lymphocyte assay (51Cr release assay) at the term of pre-and post-immunization and challenge infection with EIAV-LN in DL V-immunized horses, and research on the cellular immune mechanism of DLV at the level of lymphocyte subsets further. And that we investigate the susceptibility of horse PBL to DLV using RT assay and FCM primarily.Flow cytometric analysis showed that, in DLV-immunization group, for each horse, the absolute numbers of PBL,CD4+T cells and CD8+T cells are compared between the periods of pre- and post-inoculation with DLV and challenge infection with virulent EIAV. After inoculation with DLV, the variation of lymphocyte numbers is stable in 3/4 horses, and the reduction of lymphocyte numbers was significant (p < 0.05) in 1/4 horses. And the fluctuation of CD4+T lymphocyte numbers is even in all of the horses of this group. CD8+T lymphocyte numbers increase in 3/4 horses(p < 0.05,one horse),and CD8+T lymphocyte numbers decrease in 1/4 horses (p > 0.05) .At the term of challenge infection with virulent virus, the lymphocyte numbers and CD4+T lymphocyte numbers in DLV-inoculated horses decrease less than those in the positive control horses (in the period of febrile); and in the group of DLV-inoculated horses,CD8^T lymphocyte numbers elevate in 3/4 horses and decrease in 1/4 horses compared with pre-immunization. Compared with the period of DLV-immunization, lymphocyte numbers and CD4+T lymphocyte numbers decrease in DLV-inoculated horses at the term of challenge infection with virulent virus; and CD8+T lymphocyte numbers decrease in 3/4 immunization horses, and increase in 1/4 immunization horses. In the positive control horses, one horse was febrile three times, and CD8+T lymphocyte numbers increase in the first febrile period, and decrease in the second and third febrile period, and another horse was febrile seven times, and CD8+T lymphocyte numbers decrease during four febrile periods detected in this experiment. The above results indicated that horses immunized with DLV, whose CD8+T lymphocyte numbers increase, and protect from challenge infection with virulent virus, otherwise, the horses can't be protected completely.The level of EIAV-specific positive T lymphocyte reaction increase gradually in DLV-immunized horses. The lymphocyte proliferation reaction was detected in horses at the second month after DLV immunization, and the value of lymphocyte reactivity just before infection with the virulent EIAV was similar to the level at the first month post infection in DLV-inoculation horse, but lower than the valueat the 25'th month after challenge infection with virulent virus in DLV-inoculation horse, and all of the above results were lower than those in horses infected with EIAV naturally. The level of lymphocyte reactivity in DLV-inoculated horses was higher than that in the horses infected with virulent virus, and EIAV-specific reactive lymphocyte proliferation does not occur in the negative control horses. The above-mentioned results indicate that the lymphocyte proliferation reactivity is direct correlation with the protective immunity of horses provided by DLV.PBLs from DLV-immunized horses stimulated by EIAV in vitro could cause lysis of DLV-infected or D-gag-TW/D-env-TVV or L-gag-TVV/L-env-TVV transduced homologous lymphocyte blasts, which have difference between vaccinated horses. In the period of challenge infection with v...