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J. Virol., Feb 1995, 814-824, Vol 69, No. 2
A Steinkasserer, R Harrison, A Billich, F Hammerschmid, G Werner, B Wolff, P Peichl, G Palfi, W Schnitzel and E Mlynar
SDZ NIM 811 is a cyclosporin A analog that is completely devoid of
immunosuppressive capacity but exhibits potent and selective anti-human
immunodeficiency virus type 1 (HIV-1) activity. The mechanism of action of
SDZ NIM 811 is clearly different from those of all other anti-HIV agents
described so far. In cell-free assays, it is not an inhibitor of reverse
transcriptase, protease, integrase, and it does not interfere with Rev or
Tat function. SDZ NIM 811 does not down-regulate CD4 or inhibit fusion
between infected and uninfected, CD4-expressing cells. p24 production from
chronically HIV-infected cells is not impaired either. To elucidate the
mode of action of SDZ NIM 811, we performed DNA PCR analysis in HIV-1
IIIB-infected MT4 cells in one cycle of virus replication. The effects of
SDZ NIM 811 on the kinetics of viral DNA synthesis, appearance of two-long
terminal repeat circles (2-LTR circles), and integration of DNA were
studied. SDZ NIM 811 inhibited 2- LTR circle formation in a
concentration-dependent manner, which is indicative of nuclear localization
of preintegration complexes. Half- maximal inhibition was achieved at 0.17
microgram/ml; this concentration is close to the 50% inhibitory
concentrations (0.01 to 0.2 microgram/ml) for viral growth inhibition. As
expected, integration of proviral DNA into cellular DNA was also inhibited
by SDZ NIM 811. Analysis of the viral particles produced by SDZ NIM
811-treated, chronically infected cells revealed amounts of capsid
proteins, reverse transcriptase activity, and viral RNA comparable to those
of the untreated control. However, these particles showed a dose-dependent
reduction in infectivity (50% inhibitory concentration of 0.028
microgram/ml) which indicates that the assembly process is also impaired by
SDZ NIM 811. Gag proteins are postulated to play a role not only in
assembly but also in early steps of viral replication, e.g., nuclear
localization of the preintegration complex. Recently, it was reported that
HIV-1 Gag protein binds to cyclophilin A, the intracellular receptor for
cyclosporin A. Interference with Gag- cyclophilin interaction may be the
molecular basis for the antiviral activity of cyclosporin A and its
analogs.
Copyright © 1995, American Society for Microbiology
Mode of action of SDZ NIM 811, a nonimmunosuppressive cyclosporin A analog with activity against human immunodeficiency virus type 1 (HIV- 1): interference with early and late events in HIV-1 replication
Sandoz Forschungsinstitut GmbH, Vienna, Austria.
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