Modifications of the Human Immunodeficiency Virus Envelope Glycoprotein Enhance Immunogenicity for Genetic Immunization

Abstract

In this study, we have investigated the effect of specific mutations in human immunodeficiency virus type 1 (HIV-1) envelope (Env) on antibody production in an effort to improve humoral immune responses to this glycoprotein by DNA vaccination. Mice were injected with plasmid expression vectors encoding HIV Env with modifications in regions that might affect this response. Elimination of conserved glycosylation sites did not substantially enhance humoral or cytotoxic-T-lymphocyte (CTL) immunity. In contrast, a modified gp140 with different COOH-terminal mutations intended to mimic a fusion intermediate and stabilize trimer formation enhanced humoral immunity without reducing the efficacy of the CTL response. This mutant, with deletions in the cleavage site, fusogenic domain, and spacing of heptad repeats 1 and 2, retained native antigenic conformational determinants as defined by binding to known monoclonal antibodies or CD4, oligomer formation, and virus neutralization in vitro. Importantly, this modified Env, gp140⌬CFI, stimulated the antibody response to native gp160 while it retained its ability to induce a CTL response, a desirable feature for an AIDS vaccine.Plasmid DNA vaccination has been a useful technology for the development and analysis of immunogens. This method of vaccination allows relevant posttranslational modifications, appropriate intracellular trafficking, and antigen presentation. Direct injection of naked DNA either intramuscularly or intradermally readily induces protective immune responses in animal models. Though DNA vaccines readily elicit cell-mediated immune responses, their ability to induce high-titer antibody responses has been limited, particularly to human immunodeficiency virus type 1 (HIV-1) envelope (Env). However, plasmid expression vectors can be readily modified to express different forms of HIV envelope proteins, enabling rapid and systematic testing of alternative vaccine immunogens.To improve the immune response to native gp160 and to expose the core protein for optimal antigen presentation and recognition, we have analyzed the immune response to modified forms of the protein. The conserved N-linked glycosylation sites previously suggested to limit the antibody response (39) were comprehensively analyzed. In addition, the important coiled-coil hairpin region involved with formation of fusion intermediates has been studied. Expression vectors with deletions in the cleavage site (C), the fusion peptide (F), and the interspace (I) between the two heptad repeats, termed ⌬CFI deletions, were prepared. In this report, the immune response to Env candidates expressed in plasmids with codons modified to improve gene expression has been analyzed. Both antibody and cytotoxic-T-lymphocyte (CTL) responses were evaluated after injection of plasmid DNA into muscle. A modified gp140 DNA has been identified that better elicits antibody responses at the same time that it retains its capacity to induce CTL responses to HIV Env. This prototype may facilitate the identification of immunogens ...

Single-cell gene-expression profiling reveals qualitatively distinct CD8 T cells elicited by different gene-based vaccines

“…Plasmid DNA, recombinant replication-defective adenovirus and lymphocytic choriomeningitis virus (rAd5 and rLCMV, respectively), encompassing the same insert derived from a recombinant HIV-1 Env gene (17), were used to immunize BALB/c mice in different prime-boost combinations. The three different primeboost immunization regimens (DNA-rAd5, rAd5-rAd5, and rAd5-rLCMV) elicited T-cell responses with mean frequencies ranging from 20.1to 32.6% (Fig.…”

Long-Term Maintenance of gp120-Specific Immune Responses by Genetic Vaccination with the HIV-1 Envelope Genes Linked to the Gene Encoding Flt-3 Ligand

“…Despite limited expression of Ag in situ, impressive results have recently been obtained for DNA vaccines that are capable of priming the immune system more efficiently, resulting in highly boostable HIV-specific CD8 ϩ T cell responses in mice and rhesus macaques (7)(8)(9)(10)(11)(12)(13). As sentinels of the immune system, DC are at the crossroads of innate and adaptive immunity and therefore perform crucial roles in linking them functionally for immune augmentation.…”

HIV-1 Diversity in Tanzania and its Implication toward Development of Effective Vaccines: A Review Article

“…The ability of Glycoprotein 120 to induce production of Cytotoxic T lymphocytes against other conserved HIV-1 proteins will be able to cross react and offer a new hope for vaccines [18]. T lymphocytes (CTLs) against gag gene products and other relatively conserved HIV-1 proteins are usually assumed to be more cross-reactive, offering a hope for the development of broadly protective vaccines [18]. The new challenges arriving from HIV-1 strains capable of using both chemokine receptor (CCR5) and Chemokine receptor (CXCR4), therefore there will be a need to develop antibodies capable of neutralizing both X5 and X4 strains [19].…”

“…Glycoprotein 120 is responsible for inducing neutralizing antibodies which will cut across the subtypes. The ability of Glycoprotein 120 to induce production of Cytotoxic T lymphocytes against other conserved HIV-1 proteins will be able to cross react and offer a new hope for vaccines [18]. T lymphocytes (CTLs) against gag gene products and other relatively conserved HIV-1 proteins are usually assumed to be more cross-reactive, offering a hope for the development of broadly protective vaccines [18].…”