Abstract
Virus-like vesicles (VLV) are hybrid vectors based on an evolved Semliki Forest virus (SFV) RNA replicon and the envelope glycoprotein (G) from vesicular stomatitis virus (VSV). Previously, we showed that VLV can be used to express protein antigens and generate protective antigen-specific CD8+ T cells. This report describes VLV vectors designed for enhanced protein expression and immunogenicity. Expressing hepatitis B virus (HBV) middle S antigen (MHBs) from VLV using a dual subgenomic promoter significantly increased MHBs-specific CD8+ T cell and antibody production in mice. Furthermore, envelope glycoprotein switch from VSV Indiana to the glycoprotein of Chandipura virus enabled prime-boost immunization and further increased responses to MHBs. Therapeutic efficacy was evaluated in a mouse model of chronic HBV infection initiated by HBV delivery with adeno-associated virus. Mice with lower or intermediate HBV antigen levels demonstrated a significant and sustained reduction of HBV replication following VLV prime-boost immunization. However, mice with higher HBV antigen levels showed no changes in HBV replication, emphasizing the importance of HBV antigenemia for implementing immunotherapies. This report highlights the potential of VLV dual promoter vectors to induce effective antigen-specific immune responses and informs the further development and evaluation of hybrid viral vaccine platforms for preventative and therapeutic purposes.
Highlights
Virus-like vesicles (VLV) are a capsid-free, self-replicating virus-like vaccine platform carrying positive-strand capped and polyadenylated RNA encoding an in vitro evolved Semliki Forest virus (SFV) RNA-dependent RNA replicase and the vesicular stomatitis virus (VSV) glycoprotein [1]
We designed an alternative vector with MHBs upstream of VSV glycoprotein (VSV-G), each expressed from separate subgenomic promoters (Figure 1A)
VLV dp expressing Chandipura virus glycoprotein formed plaques in baby hamster kidney (BHK)-21 cells that are morphologically distinct from those expressing VSV Indiana glycoprotein (Figure 1E), and importantly, no weight loss was observed when mice received intranasal administration of VLV expressing Chandipura virus glycoprotein, similar to VLV expressing Indiana glycoprotein (Figure 1F). These results demonstrate that Chandipura virus glycoprotein, which is serologically distinct from VSV Indiana glycoprotein, is competent for enabling VLV replication with in vitro evolved SFV nsp1–4
Summary
VLV are a capsid-free, self-replicating virus-like vaccine platform carrying positive-strand capped and polyadenylated RNA encoding an in vitro evolved SFV RNA-dependent RNA replicase and the VSV glycoprotein [1]. The VLV platform replicates like a virus, but its only structural protein is the VSV glycoprotein (VSV-G), and unlike many other viral vectors, it lacks pathogenicity [4,5]. The newly translated SFV RNA replicase synthesizes complementary negative-strand RNA, full-length positive-strand RNA, and a smaller mRNA encoding VSV-G [2,6]. We showed immunogenicity of VLV expressing antigens from hepatitis B virus (HBV) in mice and human immunodeficiency virus (HIV) in non-human primates [4,8]
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