Targets of a protease inhibitor, KNI-272, in HIV-1-infected cells

Abstract

The targets of a protease inhibitor, KNI-272, in the HIV-1 life cycle were investigated in this study. Neither expression of HIV-1 Gag proteins nor production of virus particles was detected in cells infected acutely with HIV-1 cultured in the presence of KNI-272. Although HIV-1 proviral DNA was detected in the cells by PCR, the inhibitor depressed the amount of the proviral DNA in a concentration dependent manner. These results indicate that one of the targets of KNI-272 occurs in the stage before the expression of viral structural proteins. No direct inhibition of reverse transcription was found with the inhibitor. To confirm the inhibition of viral protease, persistently HIV-1-infected cells were cultured in the presence of the inhibitor and examined by electron microscopy for the morphology of HIV-1 particles. Doughnut-shaped immature particles were observed in the extracellular space of the cells, and disrupted semicircular shaped particles were also seen at the higher concentration of KNI-272. A bioassay for infectivity showed that the virus particles were not infectious, and immunofluorescent assay using anti-p17 antibody, that does not react with the precursor of Gag protein, revealed that Gag precursor p55 protein in the cells was not processed. Thus, KNI-272 blocked the maturation of viral particles. Consequently, KNI-272 has at least two inhibition targets in the stages of the HIV-1 life cycle.

In Vitro Processing of HIV-1 Nucleocapsid Protein by the Viral Proteinase: Effects of Amino Acid Substitutions at the Scissile Bond in the Proximal Zinc Finger Sequence

“…On the basis of the NC cleavage observed in the EIAV capsid, we hypothesized that the PR is active in the early phase of the virus life cycle and that the NC protein is one of the targets of PR processing ( 18 , 42 , 43 ). Several research groups, including ours, found an inhibitory effect of PR inhibitors in the early phase of viral replication ( − ), supporting this assumption, while others did not observe such an effect ( − ). When the required zinc removal and the acidic pH optimum of the PR are taken into account, the likely place of the early-phase NC processing is the endosome for viral particles entering the cells through receptor-mediated endocytosis.…”

Modulation of HIV-1-host interaction: role of the Vpu accessory protein

“…Tetherin is a protein highly expressed in plasmacytoid dendritic cells (pDCs), the major producers of type I IFN, and in some cancer cells, while lower basal levels of expression are detected in bone marrow stromal cells, terminally differentiated B cells, macrophages, and T cells [100-104]. Its expression is strongly induced by type I IFNs in virtually all cell types [99,101,105-107], indicating that it is likely part of the innate defense response to virus infections.…”