Development of a DNA Vaccine Designed to Induce Cytotoxic T Lymphocyte Responses to Multiple Conserved Epitopes in HIV-1

Abstract

Epitope-based vaccines designed to induce CTL responses specific for HIV-1 are being developed as a means for addressing vaccine potency and viral heterogeneity. We identified a set of 21 HLA-A2, HLA-A3, and HLA-B7 restricted supertype epitopes from conserved regions of HIV-1 to develop such a vaccine. Based on peptide-binding studies and phenotypic frequencies of HLA-A2, HLA-A3, and HLA-B7 allelic variants, these epitopes are predicted to be immunogenic in greater than 85% of individuals. Immunological recognition of all but one of the vaccine candidate epitopes was demonstrated by IFN-γ ELISPOT assays in PBMC from HIV-1-infected subjects. The HLA supertypes of the subjects was a very strong predictor of epitope-specific responses, but some subjects responded to epitopes outside of the predicted HLA type. A DNA plasmid vaccine, EP HIV-1090, was designed to express the 21 CTL epitopes as a single Ag and tested for immunogenicity using HLA transgenic mice. Immunization of HLA transgenic mice with this vaccine was sufficient to induce CTL responses to multiple HIV-1 epitopes, comparable in magnitude to those induced by immunization with peptides. The CTL induced by the vaccine recognized target cells pulsed with peptide or cells transfected with HIV-1 env or gag genes. There was no indication of immunodominance, as the vaccine induced CTL responses specific for multiple epitopes in individual mice. These data indicate that the EP HIV-1090 DNA vaccine may be suitable for inducing relevant HIV-1-specific CTL responses in humans.

Recognition of Variant HIV-1 Epitopes from Diverse Viral Subtypes by Vaccine-Induced CTL

“…Fifty-one of 62 HIV-1C sequences used represented viral isolates collected from HIV-1 ϩ patients throughout the South African country of Botswana (15,42,43). Viral sequences were analyzed using motif-based search software to identify putative CTL epitopes analogous to those encoded in the EP HIV-1090 DNA vaccine (17). Synthetic peptides representing the putative epitopes were synthesized, and their binding to solubilized HLA-A*0201 and HLA-A*1101 molecules was measured (44,45).…”

“…The EP HIV-1090 DNA vaccine encodes 21 CTL epitopes, restricted to the HLA-A2, A3, and B7 supertypes (17). The synthetic gene was constructed using overlapping oligonucleotides in a PCR-based synthesis (41).…”

“…Vaccine strategies developed to address HIV-1 variation include the use of subtype-based ancestral or consensus sequences (13,15,16) and the use of highly conserved regions or epitopes (17). The logic behind this latter approach is that these regions of the HIV-1 genome are conserved because mutations would negatively impact gene function and general viral fitness.…”

Identification of CD8+ T Cell Epitopes Against Mycobacterium tuberculosis

“…One of the approaches to find effective and safe vaccines is epitope-based DNA vaccination that enables focusing of the immune response on important and highly conserved epitopes [45]. This provides the opportunity to use specific epitopes to shift the immune system toward a Th1 or a Th2-mediated immune response and eliminate the unwanted responses.…”

Recombinant and epitope-based vaccines on the road to the market and implications for vaccine design and production

“…In addition, the DNA vaccine encoded 21 HIV-derived CD8+ T-cell epitopes plus the promiscuous PADRE CD4+ T-cell epitope. 33,34 Considerations for epitope-based vaccine design…”