[Effect of cytoxan on immune response of Japanese encephalitis virus killed and live vaccines].

Mice vaccinated by Japanese encephalitis (JE) virus killed and live vaccines respectively were injected subcutaneously with cytoxan (1.5 mg/10 g weight) once every two days for 3 times, and then challenged by JE virus virulent A2 strain. The results showed that the protective rate of killed vaccine (inoculated 3 times) was decreased from 100% to 20% after cytoxan immunosuppression, while that of live vaccines 2-8 strain and 5-3 strain (inoculated 2 times) still remained 100% as in the control group without cytoxan. The results indicate that the immune response induced by the killed vaccine can be easily damaged by cytoxan, but that induced by the live vaccines not, suggesting of important advantage of JE virus live vaccine. Our results implies that the JE incidence being higher in old subjects probably is related to the declining of immune function.