Bestatin-mediated inhibition of leucine aminopeptidase may hinder HIV infection.

Bestatin, an inhibitor of leucine aminopeptidase (LAPase), significantly decreased HIV infection as reflected by a reduced number of positive immunofluorescent cells, p24 levels, reverse transcriptase activity and the number of proviral copies found in Bestatin-treated cells. Cellular and extracellular LAPase activity in infected cells was higher than the LAPase activity found in uninfected cells. However, cellular and extracellular LAPase activity as well as total protein kinase C activity was lower in Bestatin-treated cells. Conversely, the incubation of human lymphocytic HUT78 cells with LAPase promotes HIV infectivity. The possible role of LAPase in the pathophysiology of HIV was assessed by determining LAPase serum levels in HIV infected patients. LAPase activity levels were three orders of magnitude greater in sera obtained from HIV patients than those detected in sera of uninfected individuals. Although Bestatin reduced HIV infection, a moderate decrease in the reverse transcriptase activity of chronically-infected H9 human T-lymphocytic cells was observed. Based on the higher levels of LAPase present in the serum of HIV patients and on the combined inhibitory effect of Bestatin on LAPase and on protein kinase C activities, we suggest that LAPase may play an important role in the early events of HIV infection such as viral entry.