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J. Virol., Dec 1997, 9753-9763, Vol 71, No. 12
V Kolesnitchenko, L King, A Riva, Y Tani, SJ Korsmeyer and DI Cohen
We have investigated the relative contribution of apoptosis or programmed
cell death (PCD) to cell killing during acute infection with T-cell-tropic,
cytopathic human immunodeficiency virus type 1 (HIV-1), by employing
diverse strategies to inhibit PCD or to detect its common end-stage
sequelae. When Bcl-2-transfected cell lines were infected with HIV-1, their
viability was only slightly higher than that of control infections.
Although the adenovirus E1B 19-kDa protein has been reported to be a
stronger competitor of apoptosis than Bcl-2, it did not inhibit
HIV-mediated cell death better than Bcl-2 protein. Competition for Fas
ligand or inactivation of the Fas pathway secondary to intracellular
mutation (MOLT-4 T cells) also had modest effects on overall cell death
during acute HIV infection. In contrast to these observations with HIV
infection or with HIV envelope-initiated cell death, Tat-expressing cell
lines were much more susceptible (200% enhancement) to Fas-induced
apoptosis than controls and Bcl-2 overexpression strongly (75%) inhibited
this apoptotic T-cell death. PCD associated with FasR ligation resulted in
the cleavage of common interleukin-1beta-converting enzyme (ICE)-protease
targets, poly(ADP- ribose) polymerase (PARP) and pro-ICE, whereas cleaved
products were not readily detected during HIV infection of peripheral blood
mononuclear cells or T-cell lines even during periods of extensive cell
death. These results indicate that one important form of HIV-mediated cell
killing proceeds by a pathway that lacks the characteristics of T- cell
apoptosis. Our observations support the conclusion that at least two HIV
genes (env and tat) can kill T cells by distinct pathways and that an
envelope-initiated process of T-cell death can be discriminated from
apoptosis by many of the properties most closely associated with apoptotic
cell death.
Copyright © 1997, American Society for Microbiology
A major human immunodeficiency virus type 1-initiated killing pathway distinct from apoptosis
Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-4255, USA.
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