A VP4-Based Pseudovirus Nanoparticle Rotavirus Vaccine for Oral Immunization

About This Grant

Abstract Rotaviruses (RVs) cause severe diarrhea in young children. The current live RV vaccines show reduced efficacy in low- and middle-income countries (LMICs), ranging from 40% to 60%. Consequently, RV infections continue to claim ~130,000 lives annually and cause enormous morbidity, calling for a new generation of RV vaccines with improved effectiveness. Reasons for the diminished vaccine efficacy in LMICs include several factors that disrupt gut’s health and reduce the replication capacity, and thus the efficacy, of live RV vaccines. In response to these challenges, a non-replicating RV vaccine presents itself as a viable option for enhancing effectiveness in LMICs. To address this need, we have invented pseudovirus nanoparticles (PVNPs) named S-VP4e. They consist of a calicivirus inner shell and multiple RV spikes (VP4e) on the surface. The exposed RV spikes formed by VP4e facilitate RV attachment and entry. Antibodies elicited by natural RV infections are largely specific to VP4e and are predominantly neutralizing and protective, supporting VP4e as an ideal vaccine target. The bioengineered S-VP4e PVNP is self-assembled, easily produced, stable, highly immunogenic, and protective against diarrhea caused by RV challenge, making it an excellent RV vaccine candidate. Furthermore, the non- replicating nature of the PVNP will bypass the replication issue of live vaccines and avoid the intussusception risk associated with the replication of live RV vaccines, ensuring better efficacy and safety. Additionally, its low- cost production offers improved cost-effectiveness for LMICs. As a proof of concept, we have demonstrated that a trivalent vaccine comprising three S-VP4e PVNPs, representing the three predominant RV P types (P[8], P[4], and P[6]), elicited high and balanced neutralizing antibody titers against the three major RV types after intramuscular injection. Moreover, it effectively protected mice from diarrhea caused by challenge with RVs. In this application we will evaluate the trivalent PVNP vaccine for oral administration, using U-Omp19 as an adjuvant to enhance mucosal immunity. U-Omp19 is a protease inhibitor that protects vaccine antigens from degradation in the gastrointestinal tract while triggering vaccine specific mucosal immune responses. The safety, immunogenicity, and protective efficacy of the PVNP vaccine will be assessed using both mouse and highly relevant gnotobiotic (Gn) pig models. This non-replicating PVNP vaccine with broad protection represent an excellent candidate for the next generation of RV vaccine. The outcomes of this project will demonstrate the vaccine's utility and provide crucial data for advancing human clinical trials. Two major lines of experiments will be conducted. First, we will assess the PVNP vaccine for its cross-P type mucosal and systemic immune responses, neutralization, and protective efficacy in mice after oral administration, using U-Omp19 as an adjuvant. Second, the mucosal and systemic immune responses and protective efficacy of the vaccine will be evaluated in Gn pig human RV challenge models. With strong preliminary data and an outstanding track record of the research team, we are well-positioned to successfully achieve the goals of this application.