Effect of Mutations in the V3 Loop of HIV-1 gp120 on Infectivity and Susceptibility to Proteolytic Cleavage

Authors:
  • JRJacqueline D. Reeves
    Jacqueline D. Reeves
  • JHJulian G. Hoad
    Julian G. Hoad
  • CTChetankumar Tailor
    Chetankumar Tailor
  • PSPaul Stephens
    Paul Stephens
  • GCGary Clements
    Gary Clements
  • SOSue Ortlepp
    Sue Ortlepp
  • KPKathleen A. Page
    Kathleen A. Page
  • JMJohn P. Moore
    John P. Moore
  • RWRobin A. Weiss
    Robin A. Weiss

Abstract
It has been suggested that the V3 domain of human immunodeficiency virus type 1 (HIV-1) isolates has to interact with a cell-surface-associated or endosomal proteinase during virus entry into susceptible cells. To investigate this hypothesis, we examined the effect of several mutations in the V3 loop on its susceptibility to proteolytic cleavage by thrombin and cathepsin E and compared it with the effect of these mutations on viral infectivity. The data obtained indicate that, if an interaction between the V3 loop and a proteinase is indeed crucial for viral entry, the substrate requirements for such a proteinase(s) would have to be very complex. In particular, it seems unlikely that a single enzyme with a unique specificity would be able to interact with all of the different HIV-1 and HIV-2/SIV strains isolated so far. Therefore, one would have to postulate the involvement of several cellular proteinases, or proteases with multiple specificities, in V3-based viral tropism.

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