Background:  Previous studies from our laboratory have shown that the subtype B Vpu contributes to the pathogenesis of simian-human immunodeficiency virus (SHIV_KU-1bMC33) in macaques, thus making the Vpu protein a potential target for anti-viral therapy. Biotron Limited has a library of more than 300 small molecule compounds that were designed to be active against HIV-1 Vpu. Recently, a novel compound, BIT225, was found to inhibit the replication of HIV-1 and SHIV in monocyte-derieved macrophages. In this study, we have assessed the ability of BIT225 to inhibit SHIV in the lymphoid T cell line C8166. BIT225 has successfully completed a single-dose, dose-escalating phase I study in healthy volunteers.

Methods: C8166 cells were infected with SHIV with intact and deleted vpu genes. We also assessed the ability of BIT225 to inhibit the replication of a SHIV expressing the subtype C vpu (SHIV_SCVpu). At various times of infection, the levels of p27 released into the cell culture medium were assessed using commercial p27 kits, and viral protein processing assessed using pulse-chase analysis.

Results: We found that BIT225 was not toxic to cells used at 10 μM or less. Our results indicate that 10 μM BIT225 reduces the amount of p27 released from SHIV_KU-1bMC33-inoculated cultures to 0.4% of the untreated control cultures. In contrast, treatment of cultures inoculated with a SHIV expressing truncated vpu gene (at amino acid position 22; SHIV_PND2) reduces the amount of p27 released to approximately 72% of the untreated cultures, suggesting specificity of this compound for virus with an intact Vpu protein. Similar to SHIV_KU-1bMC33, BIT225 was found to inhibit the replication of SHIV_SCVpu. We also determined whether BIT225 could reduce virus release if treated at different times post-inoculation. Our results indicate that virus release can be suppressed if given as long as 5 days post-inoculation.

Conclusions:  These results indicate that BIT225 can be used to inhibit SHIV replication in T lymphoid cell lines, thus allowing testing of BIT225 efficacy in the SHIV/macaque model system.