Fusion-independent virus-like particles enable rapid detection of antibody-mediated inhibition of ligand-receptor interactions

Studying antibody-mediated inhibition of ligand-receptor interactions is critical for understanding fundamental biological processes and developing therapeutic interventions. However, for high-consequence viruses with entry machinery involving multiple viral proteins, it is often difficult to develop pseudotyped viruses that can infect susceptible host cells. Here, we report a rapid platform for detecting antibody-mediated inhibition of ligand-receptor interactions by decoupling viral attachment from post-entry membrane fusion and gene expression. Our platform leverages HIV Gag-based self-assembling virus-like particles (VLPs) where Gag is fused with GFP and further pseudotyped with selected ligands for easy readout of VLP binding to susceptible cells. We first validated the platform’s stringent cell-type specificity using broadly tropic VSV-G and CD19-specific single chain fragment variable (scFv) pseudotypes. Next, we applied this technology to African swine fever virus (ASFV) - a high-consequence agricultural pathogen lacking surrogate neutralization assays due to its multi-protein entry machinery. By screening VLPs pseudotyped with different viral proteins against diverse mammalian cell lines, we found that VLP pseudotyped with ASFV CD2v binds specifically to Vero cells. Leveraging this interaction, we developed a rapid test for detecting antibodies that inhibit CD2v-pseudotyped VLP binding to Vero cells. Longitudinal analysis of sera from mRNA-LNP vaccinated pigs showed that the degrees of VLP-based binding-inhibition strongly correlated with the levels of anti-CD2v IgG, validating the assay’s utility. Overall, the pseudotyped VLP platform provides an enabling tool for ligand-receptor discovery, vaccine evaluation, and disease surveillance for select agents.