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J. Virol., Aug 1996, 4941-4947, Vol 70, No. 8
SJ Kent, SL Hu, L Corey, WR Morton and PD Greenberg
Vaccines for lentiviruses would ideally induce in the host complete
resistance to infection of host cells. However, such sterilizing immunity
may be neither readily achievable nor absolutely necessary to provide
protection from exposure to the immunodeficiency viruses. To examine the
nature of protective immunity to simian immunodeficiency virus (SIV), we
studied three macaques that had been immunized with a recombinant vaccinia
virus-based SIV subunit vaccine regimen and exhibited protection from a
challenge with cell-free SIV (MNE) as determined by viral cultures,
serology, and PCR for viral genomes. Peripheral blood mononuclear cells
were obtained from the protected macaques and analyzed for CD8+ cytotoxic
T-lymphocyte (CTL) responses to SIV proteins. CTL reactive to SIV proteins
not included in the subunit vaccine, and thus to which these animals had
not been exposed prior to challenge, were detected postchallenge in the
vaccine- protected animals and persisted for up to 1 year. These CTL, as
reflected by studies of cytolytic lines and derived T-cell clones, were
CD8+, did not recognize allogeneic targets, and recognized the SIV proteins
in the context of class I major histocompatibility complex molecules. The
frequency of precursor CD8+ CTL reactive to SIV proteins was determined by
limiting-dilution analysis and demonstrated that the responses elicited
following challenge of protected animals to SIV proteins not present in the
vaccine were quantitatively similar to those of animals persistently
infected with SIV. The presence of these CD8+ CTL responses to SIV proteins
present only in the challenge virus suggests that infection of some host
cells occurred postchallenge. These results suggest that the development of
a low level of SIV infection following exposure of vaccinated hosts to SIV
does not preclude protection from lethal SIV disease by vaccine-induced
immunity.
Copyright © 1996, American Society for Microbiology
Detection of simian immunodeficiency virus (SIV)-specific CD8+ T cells in macaques protected from SIV challenge by prior SIV subunit vaccination
Department of Medicine, University of Washington, Seattle 98195, USA.
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