The Research Of Immune Response Induced By Human Inactivated Rotavirus Vaccine In Experimental Animals

Rotavirus (RV) is one of the most important pathogens of severe diarrhea in infants and children. In developed and developing countries, rotavirus infection rates are similar. There are about600,000children die from rotavirus infection each year around the world, and80%of them are in developing countries. Because of the lack of the effective therapeutic drugs, vaccines would be a powerful tool to prevent rotavirus infection and reduce the severe mortality. Currently, all approved rotavirus vaccines are oral live attenuated vaccines in the domestic and foreign markets. Though some positive immune efficacy could be acquired by these live attenuated vaccines, the risks of virulence atavism and exogenous residue contaminating are potential problems. The development of inactivated rotavirus vaccine (IRV) could be an important strategy and supplement to fight against rotavirus. Furthermore, multiple rotavirus serotypes in different countries and regions enhanced the difficulty of vaccine prevention. So we have chosen a circulating regional virus strain as an available candidate vaccine strain to research, which will increase the specificity and efficacy of vaccines.[Objective] To evaluate biological characteristics and immunogenicity of a rotavirus strain from a epidemic area.[Methods] A wild rotavirus strain ’ZTR-68’was isolated by adapted culture in MA104cell and Vero cell, determined the serotype by gene sequencing, purified by Q-FF and G-25, inactivated by heat with chemical, then determined for antigenicity by immunocolled gold method, for proliferation by IFA, for genomic stability by PAGE, for morphology of virus by electron microscope.After virus was inactivated, different amounts of antigens (ELISA unit:EU) mixed with Al(OH)3to be made into the experimental vaccines.The mice were divided into test group and control group (injected buffer). Six test groups were immunized with different dose (4EU.8EU,16EU,32EU,64EU,128EU). Each group had six mice which were immunized by intramuscular injection. Three immunizations which contain one basic immunization and two booster immunizations were conducted every two weeks. The titers of RV specific antibody and neutralizing antibody were detected by ELISA and immunofluorescent respectively two weeks after each immunization. Meanwhile, using western blot studied the special structure protein of RV.[Results] After continuous subcultures in Vero cells, the CPE of ZTR-68strain appeared earlier, while the antigenicity increased gradually. The proliferation of ZTR-68strain of passage7reached the maximum, with a titer of7.51gCCID50/mL The nucleic acid band pattern of viral genome showed no change during subculture. After inactivation, The virus is not contagious, the antigen content attained12800EU/mL; the serum antibody titers of mice immunized with the adapted strain reached1:3319. neutralizing antibody titers got1:510, the specific antibody could bind to VP6protein.[Conclusion] Rotavirus ZTR-68strain was stably proliferated in Vero cells, which maintained the basic biological characteristics and showed good immunogenicity.