593 SIV Protease Sequences in a RT/SHIV Background are Sensitive to HIV-1 Protease Inhibitors E. Paintsil*, L.Alexander Yale Univ, New Haven, CT
Background: The limited homology between SIV and HIV-1 RT and protease genes could lower sensitivity of SIV sequences to HIV-1 inhibitors. We investigated if HIV-1 protease sequences could functionally substitute for SIV protease sequences in a recombinant SHIV. Additionally, we investigated if SIV protease is sensitive to HIV-1 protease inhibitors when expressed in the context of RT/SHIV/TC, a recombinant in which SIV RT sequences have been replaced with HIV-1 RT sequences.
Methods: SIV protease sequences were replaced with HIV-1 protease sequences and the resulting DNA was transfected into CEMx174 cells. RT/SHIV/TC or HIV-1 (strain NL4-3) infected cells were also incubated with HIV-1 protease inhibitors Indinavir or Kaletra at concentrations of 0.2, 1.0, and 5.0 mM. The effects of these inhibitors on virus replication was determined.
Results: Transfection of CEMx174 cells with recombinant SIV containing HIV-1 protease sequences failed to produce detectable levels of viral antigen. In our drug sensitivity experiments, Indinavir and Keletra were potent inhibitors of both NL4-3 and RT/SHIV/TC, with only 0.2 and 1.0 mM concentrations, respectively, repressing replication by three logs.
Conclusions: Our experiments indicate that HIV-1sequences that encode the protease gene cannot functionally substitute for sequences that encode the SIV protease gene. These sequences also encode for Gag sequences and thus, the block in viral replication could be either Gag or protease determined. Surprisingly, we observed that SIV sequences retained a high level of sensitivity to Indinavir and Keletra. However, these levels were somewhat lower (5-fold) than was observed for NL4-3. This is likely due to the fact that SIV protease contain several amino acids that decrease sensitivity to these compounds (I: 10, 32, 36, 46). It is possible that the introduction of such amino acids could increase drug sensitivity of SIV protease to levels that are comparable to those of HIV-1 protease. In this case, we will have developed a recombinant that will be highly sensitive to all types of anti-retroviral drug and thus, would be useful for studies of these compounds in experimentally infected rhesus monkeys.
