Summary auto-generated
This 1998 study evaluated a modified vaccinia virus Ankara (MVA)-based vaccine expressing multiple cytotoxic T lymphocyte (CTL) epitopes from HIV-1 as a potential AIDS vaccine. Researchers constructed two recombinant MVA vectors: MVA.H expressing 20 human, one murine, and three macaque HIV epitopes, and MVA.HM additionally expressing malaria epitopes. BALB/c mice were immunized with a single dose of recombinant virus via intravenous (i.v.) or intramuscular (i.m.) routes. The i.v. route proved more immunogenic than i.m., generating significant CTL responses against the epitopes. Using chromium-release assays and ELISPOT assays measuring interferon-gamma production, the researchers confirmed these were CD8+ T cell-mediated responses with appropriate frequencies. Additionally, they demonstrated that human cells infected with MVA.H or MVA.HM properly processed and presented HLA-restricted HIV epitopes to human CTL clones and lines. The vaccine appeared safe, with no adverse effects observed in vaccinated mice. This work supported MVA as a promising vector for multi-epitope HIV vaccine development and demonstrated the feasibility of combining epitopes from multiple pathogens in a single immunogen.
Key findings
- MVA-vectored multi-CTL epitope vaccine induced significant CD8+ T cell responses against HIV and malaria epitopes in mice, with the i.v. route more immunogenic than i.m. route
- CTL responses correlated well with interferon-gamma-producing cell frequencies measured by ELISPOT assay, confirming CD8+ T cell-mediated immunity
- HLA-restricted HIV epitopes were correctly processed and presented by human cells infected with MVA vectors, as validated by CTL recognition assays
- MVA proved safe with no adverse effects observed during the 55-day observation period
- The study demonstrated the feasibility of constructing multi-epitope vaccines against multiple pathogens (HIV and malaria) in a single MVA vector
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Abstract
A vaccine against human immunodeficiency virus (HIV) is still awaited. Although the correlates of protection remain elusive, it is likely that CD8+ T cells play an important role in the control of this infection. To firmly establish the importance of these cells in protective immunity, a means of efficient elicitation of CD8+ T cell responses in the absence of antibody is needed and, when available, might represent a crucial step towards a protective vaccine. Here, a novel vaccine candidate was constructed as a multi-cytotoxic T lymphocyte (CTL) epitope gene delivered and expressed using modified vaccinia virus Ankara (MVA). The immunogen consists of 20 human, one murine and three rhesus macaque epitopes. The non-human epitopes were included so that the vaccine can be tested for immunogenicity and optimal vaccination doses, routes and regimes in experimental animals. Mice were immunized intravenously (i.v.) or intramuscularly (i.m.) using a single dose of 10(6) p.f.u. of the recombinant MVA and the induction of CTL was assessed. It was demonstrated that both administration routes induced specific CTL responses and that the i.v. route was moderately more immunogenic than the i.m. route. The frequencies of ex vivo splenocytes producing interferon-y upon MHC class I-restricted peptide stimulation were determined using an ELISPOT assay. Also, the correct processing and presentation of some HLA-restricted epitopes in human cells was confirmed.