Heterosexual transmission of human immunodeficiency virus remains the major route of transmission worldwide; thus, there is an urgent need for additional prevention strategies, particularly those that could be controlled by women. Using cellular and tissue explant models, we have evaluated the potential activity of thiocarboxanilide nonnucleoside analogue reverse transcriptase inhibitor UC-781 as a vaginal microbicide. We were able to demonstrate a potent dose-dependent effect against R5 and X4 infections of T cells. In human cervical explant cultures, UC-781 was not only able to inhibit direct infection of mucosal tissue but was able to prevent dissemination of virus by migratory cells. UC-781 formulated into a carbopol gel (0.1%) retained significant activity against both direct tissue infection and transinfection mediated by migratory cells. Furthermore, UC-781 demonstrated prolonged inhibitory effects able to prevent both localized and disseminated infections up to 6 days post compound treatment. Additional studies were carried out to determine the concentration of compound that might be required to block a primary infection within draining lymph nodes. While a greater dose of compound was required to inhibit both X4 and R5 infections of lymphoid versus cervical explants, this was equivalent to a 1:3,000 dilution of the 0.1% formulation. Furthermore, a 2-h exposure to the compound prevented infection of lymphoid tissue when challenged up to 2 days later. The prolonged protection observed following pretreatment of both genital and lymphoid tissues with UC-781 suggests that this class of inhibitors may have unique advantages over other classes of potential microbicide candidates.

Cholesterol plays an important role in the HIV life cycle, and infectivity of cholesterol-depleted HIV virions is significantly impaired. Recently, we demonstrated that HIV-1, via its protein Nef, inhibits the activity of the major cellular cholesterol transporter ATP binding cassette transporter A1 (ABCA1), suggesting that the virus may use this mechanism to get access to cellular cholesterol. In this study, we investigated the effect on HIV infection of a synthetic liver X receptor (LXR) ligand,

The first line of a host's response to various pathogens is triggered by their engagement of cellular pattern recognition receptors (PRRs). Binding of microbial ligands to these receptors leads to the induction of a variety of cellular factors that alter intracellular and extracellular environment and interfere directly or indirectly with the life cycle of the triggering pathogen. Such changes may also affect any coinfecting microbe. Using ligands to Toll-like receptors (TLRs) 5 and 9, we examined their effect on human immunodeficiency virus (HIV)-1 replication in lymphoid tissue ex vivo. We found marked differences in the outcomes of such treatment. While flagellin (TLR5 agonist) treatment enhanced replication of CC chemokine receptor 5 (CCR 5)-tropic and CXC chemokine receptor 4 (CXCR4)-tropic HIV-1, treatment with oligodeoxynucleotide (ODN) M362 (TLR9 agonist) suppressed both viral variants. The differential effects of these TLR ligands on HIV-1 replication correlated with changes in production of CC chemokines CCL3, CCL4, CCL5, and of CXC chemokines CXCL10, and CXCL12 in the ligand-treated HIV-1-infected tissues. The nature and/or magnitude of these changes were dependent on the ligand as well as on the HIV-1 viral strain. Moreover, the tested ligands differed in their ability to induce cellular activation as evaluated by the expression of the cluster of differentiation markers (CD) 25, CD38, CD39, CD69, CD154, and human leukocyte antigen D related (HLA)-DR as well as of a cell proliferation marker, Ki67, and of CCR5. No significant effect of the ligand treatment was observed on apoptosis and cell death/loss in the treated lymphoid tissue ex vivo. Our results suggest that binding of microbial ligands to TLRs is one of the mechanisms that mediate interactions between coinfected microbes and HIV-1 in human tissues. Thus, the engagement of appropriate TLRs by microbial molecules or their mimetic might become a new strategy for HIV therapy or prevention.

In infected individuals, human immunodeficiency virus type 1 (HIV-1) exist as a "swarm" of quasi species compartmentalized in tissues where individual viral variants may interact locally. We have used human lymphoid tissue, where the critical events of HIV disease occur, to study local interactions in model HIV-1 binary swarms ex vivo. We infected tissue blocks with binary mixtures consisting either of CCR5-dependent and CXCR4-dependent variants or of 2 dual-tropic HIV-1 variants, of which one is skewed to utilization of CXCR4 and the other of CCR5. HIV-1 variants that use CXCR4 suppress replication of CCR5-dependent HIV-1 variants, whereas CCR5-dependent HIV-1 variants do not affect replication of CXCR4-dependent HIV-1. CC-chemokines that inhibit replication of CCR5-dependent HIV-1 variants were up-regulated by CXCR4-dependent HIV-1, thus possibly contributing to this suppression. Tissue-specific chemokine/cytokine network modulations triggered by individual HIV-1 variants may be an important mechanism of local interactions among HIV-1 quasi species in infected tissue.

CCR5-using human immunodeficiency virus type 1 (HIV-1) isolates typically gain CXCR4 use via multiple mutations in V3 and often V1/V2 regions of envelope, and patterns of mutations are distinct for each isolate. Here, we report that multiple CXCR4-using variants of a parental CCR5-using HIV-1 isolate, SF162, obtained by either target cell selection or CCR5 inhibition have a common mutation pattern characterized by the same two V3 mutations and that these mutations preexisted in some of the SF162 stocks. These results imply that SF162 has a single pathway for acquiring CXCR4 use and that prolonged culture is sufficient to select for R5X4 variants.Human immunodeficiency virus type 1 (HIV-1) isolated from infected individuals uses CCR5 and/or CXCR4 coreceptors for cell entry (27). Infection is transmitted by CCR5-using HIV-1 variants (R5) that often later evolve into variants using CXCR4 exclusively or together with CCR5 (X4 or R5X4), and this evolution is associated with accelerating progression to AIDS (5,6,12,39). R5 or X4 phenotype is determined by the amino acid sequence of HIV-1 gp120, particularly of V3 and V1/V2, and less frequently of other regions (4,7,8,10,11,17,21,23,30,(34)(35)(36). The cause and mechanisms of the evolution towards CXCR4 usage are not fully understood. Target cell selection and the abundance of natural ligands for CCR5 and CXCR4 are thought to be two important selection factors (24,25,29), which have been modeled in vitro by propagation of R5 variants in cell lines expressing CXCR4 only (13,18,30,32) or in the presence of CCR5 ligands (1,15,26,28,37). Evolution towards CXCR4 usage in vivo (38, 39) and in vitro seems to go along multiple pathways, and most R5X4 variants have diverse mutation patterns, although some common features (e.g., charged amino acids at positions 11 and 25 of the V3 loop) have been observed (20,22,32).Earlier, it was reported that CXCR4-using variants of the R5 HIV-1 SF162 isolate (9) selected by viral propagation on CXCR4-expressing T-cell lines acquired two consistent mutations in V3, I309R and A316V (13, 18). Here, we have independently selected for CXCR4-using variants by propagating SF162 in cells expressing CXCR4 but not CCR5 (see reference 32) or in peripheral blood mononuclear cells (PBMC) in the presence of escalating concentrations of RANTES. We found that the same two V3 mutations occurred in seven independently selected CXCR4-using variants of SF162 and that the I309R mutation precedes the A316V mutation under both modes of selection. Moreover, even without RANTES, serial passage of SF162 in PBMC also selected for the same two V3 mutations, albeit more slowly than in T-cell lines or in high RANTES concentrations. Interestingly, one of the SF162 stocks obtained by culture in PBMC of HIV-1 from the AIDS Research and Reference Reagent Program already contained a minor population (11%) harboring the I309R mutation and an even smaller population (Ͻ2%) with both the I309R and A316V mutations.In the first set of experiments virus was selected in the course o...

We investigated whether CD4+ T cells that do not produce HIV-1 are killed in HIV-infected human lymphoid tissue. Tissue blocks were inoculated with high amount of doxycycline-dependent HIV-rtTA. Doxycycline triggered productive infection and loss of CD4+ T cells in these tissues, whereas without doxycycline, neither productive infection nor CD4+ T cell depletion was detected in spite of the massive presence of virions in the tissue and of viral DNA in the cells. Thus, HIV-1 alone is sufficient to deplete productively infected CD4+ T cells but is not sufficient to cause the death of uninfected or latently infected CD4+ T cells.