PA-21-259, SBIR, Phase I, Self-Amplifying RNA Replicon-Based Platform for Generating Multivalent Influenza Vaccine

PROJECT ABSTRACT Current vaccines are mainly strain-specific and have limited efficacy in preventing new, potentially pandemic influenza strains. Interest in a universal influenza vaccine (UIV) to prevent future pandemics has been greatly boosted by the success of mRNA-based coronavirus vaccines. However, developing a UIV has been particularly challenging for two reasons: (1) the failure of immunization to induce broadly neutralizing antibodies against conserved epitopes and (2) the lack of a safe and effective vaccine platform to induce broad and long-lasting immunity. Virus-like vesicles (VLVs) are infectious, self-propagating alphavirus-vesiculovirus hybrid vaccine vectors that can be engineered to express foreign antigens to elicit a protective immune response. These self-amplifying RNA replicons are safe, highly immunogenic, and scalable to produce. The goal of this proposal is to rationally design and engineer a VLV to express multiple flu antigens and thus induce broad and long-lasting immunity. As shown in our published studies, the ectodomain of M2 (M2e) and domains of the immunodominant hemagglutinin (HA) globular head can elicit robust antibody responses that mitigate disease and protect mice from lethal challenge. We have also established that VLV carrying RNA encoding one or more of the major antigens of hepatitis B virus (HBV) in a single open reading frame drives a broad multi-specific immune response that results in substantial clearance of HBV in the mouse liver. Recent improvements in the development of this VLV immunotherapy vector enhanced gene expression with a concomitant increase in both T-cell responses and antibodies. In preliminary studies, we found that signal sequences promote efficient secretion of recombinant proteins that are highly conserved among influenza strains, i.e., M2e, nucleoprotein, the long-alpha helix (LAH) of subunit 2 of HA, and fusion peptide from VLV-infected cells. Our initial single-dose screening of individual flu antigen VLV vaccines (sponsored by the Respiratory Diseases Branch of NIAID/NIH) showed promising mitigation of disease progression. A reduction in lung virus titer was apparent in HA2 VLV vaccines. Albeit low, viral neutralizing titers (VNTs) were present in all immunized groups (>1:16). In addition, our serological data show an increased induction of IgG1 and IgG2a in most flu-based VLV-immunized groups. These virus-specific IgG isotypes correlate better with vaccine efficacy than neutralization alone. We will carry out three specific aims: Aim 1. Characterize the immunogenicity of VLV-Multi-Ag constructs in mice. Aim 2. Evaluate vaccine efficacy in a lethal influenza mouse model. Aim 3. Evaluate prime-boost regimens to optimize flu-specific immune responses. The results of these studies will provide initial data on the feasibility of developing a UIV. VLV-mediated delivery of multi-antigens targeting multiple epitopes of conserved proteins may provide an effective strategy to prevent infection with influenza virus. The proposed research is highly significant because an effective vaccine is needed to prevent both influenza epidemics and to enhance our ability to respond to future pandemics.