Single-stranded RNA adjuvant enhances the efficacy of 10-valent human papilloma virus-like particle vaccine

Following the development of various types of vaccines, the use of adjuvants to boost vaccine efficacy has become a focus of research. Aluminum hydroxide (alum), the most commonly used adjuvant, induces a certain immune response and ensures safety in human trials. However, alum mainly induces only a Th2 response; its Th1 response is weak. Thus, we previously developed a single-stranded ribose nucleic acid (ssRNA) adjuvant that induces a Th1 response through toll-like receptors. Here, we explored whether 10-valent human papilloma virus (HPV)-like particle (VLP) vaccine formulated with ssRNA adjuvant and alum helped to enhance immune response and maintained memory response. The mice were immunized intramuscularly twice at 2 week intervals and were inoculated 4 days after the second boost (after about 1 year). The antibody response and T cell activation were measured by Elispot, ELISA using harvested serum and splenocytes. The 10-valent HPV VLP vaccine formulated with ssRNA adjuvant and alum increased the antigen-specific immune response more than alum used alone. It increased each type-specific IgG1/IgG2a titer, and antigen-specific IFN-gamma cells. Furthermore, the ssRNA adjuvant with alum induced memory response. In memory response, each type-specific IgG1/IgG2c, IFN-gamma, and IL-6 cytokine, and neutralizing antibodies were increased by the ssRNA adjuvant with alum. Overall, the ssRNA adjuvant with alum induced memory responses and balanced Th1/Th2 responses. The ssRNA adjuvant and alum may help to enhance prophylactic vaccine efficacy.

Automated summary

This study investigated the effects of a 10-valent HPV VLP vaccine formulated with ssRNA adjuvant and alum on enhancing immune response and maintaining memory response. The results showed that the vaccine formulated with ssRNA adjuvant and alum increased antigen-specific immune response and induced memory response. The combination of ssRNA adjuvant and alum balanced Th1/Th2 responses and could potentially enhance prophylactic vaccine efficacy.