Development testing of nucleic acid-based vaccine for HIV other indications

Division Of Basic Sciences - Nci

Investigators

Linked publications, trials & patents

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: 150-159, 1992; Schwartz, J. Virol. 66: 7176-7182, 1992; Nasioulas, J. Virol. 68: 2986-2993, 1994; Schneider, J. Virol. 71: 4892-4903, 1997). Attractive features of the nucleic acid (DNA, mRNA) 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 is 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 NHP model (Patel, PNAS 110: 2975, 2013; Jalah, PLoS One 9: e91550, 2014, Felber, Cell Reports, 31:107624, 2020). The vaccine platform combines the delivery of both vaccine components into the same anatomical site targeting the same draining lymph node. We recently reported that 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 (Felber, Cell Reports, 31:107624, 2020). 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 hypothesize that optimization of immunogens to better target the rare B cell precursor, combined with the co-administration of vaccine vector and protein in same draining lymph nodes could provide an immunological advantage over current protocols, resulting in significantly improved protection and we are exploring this mechanism in the macaque model. Our aim has been to design and test a vaccine regimen focusing the immune response to targets associated with infection prevention, i.e. the V2 domain of the HIV gp120 Env. In the VR144 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 applied our experience in developing HIV vaccines towards SARS-CoV-2 (Rosati, PLoS Pathog, 17:e1009701; 2021). The different Spike DNA-based vaccine regimens induced robust antibody and T cell responses able to effectively mediate protection and to control SARS-CoV-2 infection in macaques. All vaccine regimens led to control of SARS-CoV-2 intranasal/intratracheal challenge and absence of virus dissemination to the lower respiratory tract. Vaccine-induced binding and neutralizing antibody titers and antibody-dependent cellular phagocytosis inversely correlated with transient virus levels in the nasal mucosa. Importantly, a vaccine regimen comprising simultaneous co-immunization of DNA and protein at the same anatomical site showed was more effective than DNA alone in inducing protective immune responses and controlling SARS-CoV-2 infection. We are now exploring novel nucleic acid-based vaccines and delivery methods to achieve better immunity of DNA-only vaccine to simplify the vaccine platform.