The Immunologic Impact Of Inactivated Rotalvirus Caused By Aluminum Hydroxide

[Objective] To determine the optimum dosage ratio between aluminum hydroxide adjuvant and inactivated rotavirus vaccine.Traditionally, live attenuated vaccines and inactivated vaccines are the mostly used vaccines to prevent infectious diseases. Development of rotavirus vaccine started in the early 1990s and at present, there are three live attenuated vaccines, Rotarix, RotaTeq and LLR respectively, for the prevention of rotavirus infection. Although live attenuated vaccine can induce a comprehensive immune response, several withdraws including virulence reversion, persistent exogenous factors contamination, sensitivity to maternal antibodies and its limitation to unsuitable population such as immunocompromised children or patients who undergoing immunosuppressive therapy, may limit its application. While inactivated vaccines can circumvention these problems and is safer than live vaccines, but the effectiveness is often lower than live attenuated vaccine. Thus, to enhance the immunogenicity of the inactivated vaccine, adjuvant was wildly used to keep both high immunogenicity and safety. Aluminum hydroxide is a mostly used and effective human vaccine adjuvant. To mix aluminum hydroxide adjuvant with the vaccine optimum properly is crucial to the effectiveness and safety of inactivated vaccines and in this study, we are try to resolve this problem.[Methods] Preparation of vaccines:The vaccine were obtained through concentrating, purifying and inactivating the virus liquid that collected from cultured Vero cells harboring rotavirus ZTR-68. Same numbers of male and female ICR mice were used for immunization, which were carried out by intramuscular injection, two times every another two weeks. Blood were collected 14d after immunization for plaque reduction neutralization test to measure serum neutralization antibody titer. The experiment that examine the effect of aluminum hydroxide on vaccine immunogenicity consists of two sections:in the first section, the vaccines of same concentration (160 EU/100 ul) was combined with Al(OH)3 of different concentration for comparison, the experimental animals were injected with mixtures of different component concentrations corresponding to following combinations:0.2 mg/ml Al(OH)3+160 EU/100 ul,0.4 mg/ml Al(OH)3+160 EU/ 100 ul,0.8 mg/ml Al(OH)3+160 EU/100 ul and 1.6 mg/ml Al(OH)3+160 EU/100 ul; In the second section, the adjuvant Al(OH)3 of same concentration (0.8 mg/ml) was combined with antigen of different concentrations for comparison, experimental animals were injected with different dose of antigen (2.5 EU,10 EU,40 EU,160 EU,320 EU and 640 EU, respectively). Control groups were also included.[Results] In the first section, the results reveal that inactivated vaccine containing 0.8 mg/ml and 1.6 mg/ml aluminum hydroxide performance better with high geometric mean titers (GMT) of 1:228 and 1:256 respectively. The results of second section found that the mixture of 160 EU+0.8 mg ml Al(OH)3/100 ul is the most optimal combination with neutralizing titers GMT value of 203.18. The immunization effect of the same dose of rotavirus inactivated vaccine with adjuvant is better than vaccine group without adjuvant (P<0.05). While the first neutralizing titers GMT value of 160EU and 640EU show large difference, with 90.50 and 161.27, respectively. However, GMT values of titers were changed after adding adjuvant, with 203.18 and 181.01, respectively and no significant difference exists between two groups. After enhancing immunization, titers GMT value of 160EU and 640EU dose was significantly increased, with 161.27 and 228.07, respectively and the GMT value of group containing adjuvant increased to 287.35 and 256.[Conclusion] The aluminum hydroxide adjuvant can improve the immunogenicity of the inactivated vaccine rotavirus significantly. The optimal concentration of Al(OH)3 adjuvant is 0.8 mg/ml, with which inactivated rotavirus vaccine antigens can induce favorable humoral immune response and no significant difference between 160EU and 640EU. Thus, we conclude that 160 EU+0.8 mg/ml Al(OH)3/100μl is the optimum dosage ratio.