Evaluation of the Immunogenicity of Novel HIV-1 gp160 Env mRNA Vaccines in Pre-clinical Mouse and Guinea Pig Models

Abstract

Human immunodeficiency virus (HIV) is one of the biggest healthcare challenges that humans have ever faced, with millions of people living with HIV and new cases of infections each year. Despite advances in HIV treatments, an example being antiretroviral therapies (ART), there is still no cure. Individuals with HIV are required to take lifelong treatment for virologic control. As a result, developing a safe and effective HIV vaccine is needed to reduce new infections and protect the public. In this study, we explored the immunogenicity of structure-based, epitope-targeted HIV-1 nanoparticle enclosed messenger RNA (mRNA) vaccines targeting V2 apex of HIV Envelope (Env) glycoprotein. The vaccine encodes three engineered Env glycoproteins as immunogens: Wildtype (WT), Optimized (OPT), and Alternative (ALT). All immunogens build on HIV clade C serotype 459C backbone and are informed with broadly neutralizing antibody (bNAb) signatures. Key modifications such as stabilizing mutations, glycan hole mutations, antigenic diversity set mutations, and cleavage site linkers were introduced to improve trimer stability, immunogenicity, and the breadth of antibody responses. mRNA encoding these immunogens was formulated into lipid nanoparticles (LNPs) for delivery. Mice and Guinea pigs were immunized, and sera were collected at regular intervals. Binding antibody responses were monitored by endpoint ELISA, demonstrating that SOSIP-stabilized gp160 constructs induce significantly higher IgG titers than non-SOSIP gp160 or SOSIP gp140 constructs. Moreover, incorporating fusion peptide (FP) bNAb signatures into V2-SET designs might further improve immunogenicity in both models. These findings highlight that stabilizing full-length Env in a native-like conformation and targeting multiple vulnerable epitopes enhances vaccine-induced antibody responses. For future studies, serum collected a month after the third boosting immunization would be tested with neutralizing antibody (NAb) assays against heterologous panels of select tier 2 V2-sensitive and/or FP-sensitive HIV-Env pseudoviruses. Additional boosts and longer-term follow-ups will be performed to evaluate durability and breadth of the antibody responses. After completion of these studies in mice and guinea pigs, select candidate vaccines would finally be tested in non-human primates in the future. This study highlights the potential of mRNA-LNP vaccine platforms to elicit broad and robust immune responses against HIV. Our findings provide valuable insights into epitope-targeted immunogen design and could further inform the development of next-generation HIV vaccines capable of inducing broadly neutralizing antibodies.