A Pseudovirus Nanoparticle-Based Mpox Vaccine for Oral Immunization

ABSTRACT The two recent large mpox outbreaks, along with the WHO's declarations of two global mpox emergencies, underscore the emergence of this infectious disease as a significant public health threat. While current vaccinia virus (VACV)-based smallpox vaccines provide moderate protection via subcutaneous injections, a vaccine specifically targeting MPXV antigens with improved efficacy and safety remains lacking and is urgently needed. To address this need, we will leverage our norovirus (NoV) shell nanoparticle (SNP) platform technology to develop pseudovirus nanoparticles (PVNPs), each displaying one of the major MPXV protective antigens, as an oral vaccine. Each PVNP will consist of an icosahedral inner shell that mimics the interior layer of the NoV capsid, with multiple MPXV antigens displayed on the surface, resembling NoV protrusions. This PVNP vaccine will be administered orally using U-Omp19 as an adjuvant to enhance mucosal immunity and prevent MPXV infection and transmission. U-Omp19 is a protease inhibitor that protects vaccine antigens from degradation in the gastrointestinal tract while promoting PVNP specific mucosal immune responses. Following evaluation, PVNPs demonstrating highest protective efficacy will be selected as components of a bi- or trivalent mpox vaccine for oral immunization. We hypothesize that a PVNP-based oral mpox vaccine incorporating two to three protective MPXV antigens from both infectious virion forms will induce robust protection against mpox infection and disease compared to current VACV-based vaccines. Importantly, this vaccine is expected to provide enhanced safety and lower manufacturing costs relative to live VACV-based vaccines. As proof of concept, we have already generated two PVNPs displaying the VACV L1 and MPXV J1 antigens, respectively. We demonstrated that the PVNP with the L1 antigen provided 100% protection against mortality in mice challenged with a lethal dose of VACV. In this project, two lines of experiments will be conducted to validate our hypothesis. First, we will generate a panel of six PVNPs, each displaying a major protective MPXV antigen using a mammalian cell expression system. Each PVNP will be evaluated for protective efficacy against VACV following oral administration. Two to three PVNPs demonstrating the highest protective efficacy (>90%) will be selected and combined to formulate the final bi-/trivalent mpox vaccine. Second, the final vaccine will be evaluated for protective efficacy in a mouse model of VACV challenge, using survival rates, body weight changes, and viral loads as primary indicators of protective immunity. The commercial JynneosTM vaccine will be included as a comparator. A subset of immunized mice will be assessed one year post-vaccination to evaluate durability of protection. Additionally, the PVNP-based bi/trivalent mpox vaccine will be analyzed for mucosal, systemic, and cellular immune responses against individual MPXV antigens to elucidate mechanisms of protection. Given our strong preliminary data and the excellent track record of our research team, we are well positioned to successfully achieve the goals outlined in this application.