Nucleic acid-based vaccine for HIV and other indications

Division Of Basic Sciences - Nci

Investigators

Linked publications & trials

Abstract

The development of a safe and effective vaccine and to improve treatment strategies aiming to reduce/eliminate the virus reservoir are currently at the forefront of our research. Based on our recognition of the fundamental mechanisms of mRNA expression, exemplified by the regulated expression of HIV, we developed the key methodology to express HIV antigens at high level from RNA/codon-optimized genes, which allows efficient antigen production when expressed from simple DNA plasmids or as part of recombinant viral vectors (Schwartz, J. Virol. 66: 150, 1992;, J. Virol. 66: 7176, 1992; Nasioulas, J. Virol. 68: 2986, 1994; Schneider, J. Virol. 71: 4892, 1997). Attractive features of the nucleic acid platform lie in its simplicity, versatility, stability, with repeated administration without vector immunity, being a non-replicating vaccine and not association with adverse effects. Immunogenicity can be augmented in the presence of cytokines, i.e., IL-12 DNA co-administration. We optimized DNA delivery with the result of achieving systemic and mucosal immune responses. Importantly, we reported the dissemination of the DNA vaccine induced T cell responses to mucosal sites including rectal and vaginal mucosa, the portal of entry of HIV. We also found that DNA induced immune responses show extraordinary longevity in vaccinated macaques detectable for several years after the last vaccination. Using DNA+Protein combination vaccines, the magnitude, breadth and longevity of the immune responses increased resulting in significant improved protection from infection in the SIV/SHIV macaque model (Patel, PNAS 110: 2975, 2013; Jalah, PLoS One 9: e91550, 2014, Felber, Cell Reports, 31:107624, 2020). This vaccine platform combines the delivery of both vaccine components into the same anatomical site targeting the same draining lymph node. Co-administration in the same site showed a 67% reduction in per exposure acquisition risk relative to the controls, whereas neither animals vaccinated with DNA and protein in separate sites, nor the controls were protected from an intravaginal SHIV CH505 virus challenge. Non-neutralizing Env antibodies, antibodies mediating cellular cytotoxicity (ADCC) and antibodies with high binding to Fc-gamma RIIIa were associated with decreased transmission risk. These data suggest that simultaneous recognition, processing and presentation of DNA + Env protein in the same draining lymph nodes play a critical role in the development of protective immunity. These data have important implications for other vaccine modalities because combination vaccines are typically administered in separate anatomical sites. We hypothesized that optimization of immunogens to better target the rare B cell precursor, combined with improved administration of vaccine vector affecting the draining lymph nodes could provide an immunological advantage over current protocols. Towards optimization of the immunogen, we reported that a vaccine regimen focusing the immune response to targets associated with infection prevention, i.e. the V2 domain of HIV gp120 Env, as we did for the CE in Gag. In the R144 trial, non-neutralizing antibodies targeting V2 were found to correlate with reduced risk of HIV infection, suggesting this region as a target for vaccine development. To favor induction of V2-specific Ab, we developed novel molecules to direct and focus humoral immune responses to V2 domain of the HIV gp120 Env. We showed that V1V2 scaffold DNA priming immunization provides a method to focus immune responses to the desired target region, in the absence of immune interference by other epitopes. We reported that priming with this DNA altered the hierarchy of humoral immune responses to V2 region epitopes, providing a method for more efficient induction and maintenance of V2-specific Env Abs associated with reduced risk of HIV infection (Devasundaram, J Virol 95:e01193, 2020). We are testing the hypothesis whether these responses translate to better protection in the macaque model. We are exploring novel nucleic acid-based vaccines and delivery methods using DNA complexed with nanoparticles to achieve better immunity of DNA-only vaccine to simplify the vaccine platform. We found that the DNA/nanoparticle vaccine induced strong and long-lasting (>2 yrs) antigen-specific humoral and cellular immunity (Karaliota, Moussa, iScience, 28:112232. 2025). Interestingly, vaccine-induced T cell responses were predominantly CD8+ cells, in contrast to other DNA vaccination regimens. Immunophenotyping showed increased proliferation and dynamic changes between blood and lymph nodes of myeloid-derived cells, dendritic cells, B and T cell subsets. Early responses to vaccination are important for shaping protective immunity. We also found significant changes in biomarkers associated with lymph nodes and germinal center cell activation including CXCL13, FLT3L, IL-7, and IL-6, associated with CD4 Tfh, GC-Tfh, CD8 Tfh cell changes, and CXCL12 with B cell changes. Dissecting innate vaccine signatures has provided biomarkers predicting immunogenicity and assists in our optimization of vaccine strategies. We have previously reported a proteomic signature after BNT162b2 mRNA vaccination (NCT04743388; PMID: 34352226). These results were compared with the proteomic analysis of different nucleic acid vaccines in macaques, which allowed frequent blood and lymph nodes measurements and in-depth Flow analysis and comparing different vaccine formulations. Our studies show a rapid innate response within 4-24 hrs with liposome or nanoparticle delivery and a delay in response (day 6) after electroporation. We identified a systemic transient signature upon BNT162b2 mRNA vaccination including IL-15, IFN-gamma, IP-10/CXCL10, TNF-alpha and IL-6 in humans. Importantly, we found correlations of IL-15 and IFN-gamma responses and binding and neutralizing Spike antibody (detectable 0.5-3 months after booster vaccination). Using different vaccine platforms in the macaque model, a unifying finding has been the transient increase of IL-15, IFN-gamma, IP-10. Platforms including LNP and nanoparticles also induced CXCL13, FLT3L, IL-7, and IL-6, representing biomarkers for Germinal Center activation. These data indicated coordinated and transient cytokine/chemokine responses to the DNA vaccine that associated with expansion and migration of different myeloid and lymphocyte cell subsets. We are expanding our vaccine platform to include different HIV immunogens and found inductions of long-lasting cellular and humoral immune responses and most importantly the induction of the difficult to induce tier2 neutralizing antibodies in macaques. This was achieved by simple DNA nanoparticle vaccine, delivered by the intramuscular route. These data corroborate our hypothesis of the significant role played by innate responses to vaccination by shaping the cellular and humoral adaptive immunity. Importantly, this delivery method with its ability to induce robust T cell responses with cytotoxic potential, in addition to high neutralizing Ab has also the potential to be used in other vaccine efforts, including cancer immunotherapy.