Inhibition of HIV-1 Replication by Isoxazolidine and Isoxazole Sulfonamides

Targeting host factors is a complementary strategy for the development of new antiviral drugs. We screened a library of isoxazolidine and isoxazole sulfonamides and found four compounds that inhibited HIV-1 infection in human CD4+ lymphocytic T cells with no toxicity at IC90 concentrations. Structure-activity relationship showed that benzyl sulfonamides and a halo-substituted aromatic ring on the heterocycle scaffold were critical for antiretroviral activity. The size and position of the incorporated halogen had a marked effect on the antiretroviral activity. The sulfonamide derivatives had no significant effect on HIV-1 entry, reverse transcription and integration but impaired a step necessary for activation of viral gene expression. This step was Tat-independent, strongly suggesting that the target is a cell factor. A virus partially resistant to the least potent compounds could be selected but could not be propagated in the long term, consistent with the possibility that HIV-1 may be less likely to develop resistance against drugs targeting some host factors. Here, we provide evidence that novel synthetic methods can be applied to develop small molecules with antiretroviral activity that target host factors important for HIV-1 replication

Digoxin reveals a functional connection between HIV-1 integration preference and T-cell activation

HIV-1 integrates more frequently into transcribed genes, however the biological significance of HIV-1 integration targeting has remained elusive. Using a selective high-throughput chemical screen, we discovered that the cardiac glycoside digoxin inhibits wild-type HIV-1 infection more potently than HIV-1 bearing a single point mutation (N74D) in the capsid protein. We confirmed that digoxin repressed viral gene expression by targeting the cellular Na+/K+ ATPase, but this did not explain its selectivity. Parallel RNAseq and integration mapping in infected cells demonstrated that digoxin inhibited expression of genes involved in T-cell activation and cell metabolism. Analysis of >400,000 unique integration sites showed that WT virus integrated more frequently than N74D mutant within or near genes susceptible to repression by digoxin and involved in T-cell activation and cell metabolism. Two main gene networks down-regulated by the drug were CD40L and CD38. Blocking CD40L by neutralizing antibodies selectively inhibited WT virus infection, phenocopying digoxin. Thus the selectivity of digoxin depends on a combination of integration targeting and repression of specific gene networks. The drug unmasked a functional connection between HIV-1 integration and T-cell activation. Our results suggest that HIV-1 evolved integration site selection to couple its early gene expression with the status of target CD4+ T-cells, which may affect latency and viral reactivation

Identification of cellular factors important for HIV-1 replication by forward chemical genetics

The AIDS epidemic is a major global health problem with an estimated 33.2 million infected with HIV, mainly in Sub-Saharan Africa. Effective drugs have been developed that are targeted against selected viral proteins but HIV mutates very rapidly and invariably becomes resistant to available drugs, even when they are used in combination. A complementary, yet little explored possibility is to develop new drugs that target and block cellular factors necessary for virus replication. Host factors mutate less rapidly and hence HIV-1 drug resistance may be less likely to emerge. During my Ph.D. project I have performed a small chemical screen of inhibitors of ATP-dependent DNA motors to test their ability to inhibit HIV infection. The approach called “chemical genetics” consists in screening a library of small compounds for their ability to inhibit HIV infection, the identification of the step of the viral cycle inhibited, the identification and validation of the target and the improvement of the compound potency by chemical modification and, where possible, rational drug design. The screen revealed that Coumermycin A1 (C-AI), a gyrase B inhibitor coumarin antibiotic, potently suppressed HIV-1 infection. CA1 impaired HIV-l integration and early gene expression in a Tat-independent way by targeting two host factors. A search for conserved ATPase domains capable of binding coumarin antibiotics revealed several potential targets, including DNA Topoisomerase II and Hsp9O. Topoisomerase II played no significant role in HIV-1 infection, however Hsp9O was required for early gene expression. Docking studies revealed two C-A1 binding pockets in the C-terminus of Hsp9O. The sensitivity to C-Al-mediated inhibition of viral gene expression mapped to p24 CA protein, suggesting that CA may affect Hsp90 function to prime cells for infection. Coumermycin Al, developed by Roche in the early 1970s shows a good pharmacological profile but is not efficiently adsorbed by the gastrointestinal tract needing therefore structural improvement to be considered as anti-HIV drug. Hsp90 inhibitors might be used as antiretrovirals in selected AIDS patients