Role Of Monocytes In AIDS And As Targets For Antiviral Therapy

Dental & Craniofacial Research

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Abstract

Host Cell Factors as Targets to Disrupt the HIV Life Cycle:[unreadable] The complex life cycle of HIV involves critical functional interactions with host cell components, and these host cell factors may represent targets for therapeutic intervention. Furthermore, HIV drugs designed to interfere with requisite utilization of host cell factors by the virus are considered less likely to foster development of resistant strains than drugs directed against viral components prone to mutation. Cellular genes required for binding/entry and also productive infection by HIV have been identified as potential targets for anti-HIV drug development. Consequently, identification of cellular genes that are involved in early events, whether at the level of virion entry, viral DNA synthesis or proviral integration or production of viral transcripts remain a high priority as pivotal targets for blocking the viral life cycle. One host cell molecule(s) which is involved in the HIV life cycle is apolipoprotein B mRNA-editing catalytic polypeptide-like 3G (APOBEC3G), which is an innate intracellular protein with lethal activity against HIV. Originally thought to be constitutively expressed and depleted by the virus, our studies demonstrate that the levels of this host defense molecule can be augmented by interferon, concomitant with resistance to HIV. [unreadable] [unreadable] Among the additional genes identified which are obligatory to the successful life cycle of HIV in macrophages is p21, a cyclin-dependent kinase inhibitor 1A (CDKN1A). The HIV viral protein R (Vpr), which facilitates virus replication in non-dividing cells and is required for efficient HIV-1 production in late stages of replication in tissue macrophages, was found to represent a pathway by which HIV-1 drives p21 transcription. Importantly, inhibition of p21 by siRNA, antisense, or a synthetic triterpenoid, 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO), known to influence p21 expression, suppressed viral replication. These data implicate p21 as a requisite macrophage facilitator of viral replication. Moreover, regulators of this molecule, such as CDDO, may provide an interventional approach to modulate HIV-1 replication. [unreadable] [unreadable] Mucosal targeting and resistance factors in HIV infection:[unreadable] The human tonsil represents a target and potential reservoir for HIV replication. Oral HIV-1 transmission, although rare, does not preclude this secondary lymphoid organ from becoming heavily infected either initially or secondarily as the disease progresses. In order to identify what unique factors favor the massive infection seen in tonsil lymphoid tissues, tonsil susceptibility to HIV infection was compared with that of peripheral blood mononuclear cells (PBMC) and resting T lymphocytes. In these studies, we identified several unique aspects of the micromilieu of the tonsil that may support the permissive nature of the tonsil to HIV infection. In culture, as occurs in situ, tonsil cells are more permissive for HIV, independent of additional exogenous stimulation. By a battery of analyses, including transcriptional, signal transduction, and proteomic, we identified multiple contributory elements to the retroviral permissive nature of the tonsil. Such a profile of immune regulation is necessary to control immune activation, yet maintain a state of readiness in an environment constantly bombarded with antigens and pathogens, but which unfortunately represents a favorable condition for HIV replication. In ongoing studies, the contribution of tonsil Treg, macrophages and dendritic cells as potential regulators and targets for the virus in HIV pathogenesis is also being dissected. Further understanding of these immunoregulatory pathways and their contribution to HIV pathogenesis will promote strategies for manipulating vulnerable mucosal compartments.[unreadable] [unreadable] Although tonsils may serve as reservoirs for the replication of HIV, whether the tonsils serve as a conduit for person to person HIV transmission remains unclear. We isolated epithelial cells from the tonsil and compared the genetic profile of the tonsil epithelium with that of gingival epithelial cells. Among the variations in the two tissues was significantly higher expression in the tonsil epithelium of the CXCR4 gene, which encodes a surface protein that HIV can use to anchor itself to cells before entry. Increased gene expression in the tonsil epithelium of potential HIV-binding molecules (FcRgamma, complement receptor 2, and complement components), together with lower levels of innate immune molecules with potential anti-HIV activity (SLPI, beta-defensins, and thrombospondin), suggest that increased expression of molecules associated with HIV binding and entry coupled with decreased innate antiviral factors may render the tonsil a potential site for transmission. These and other unique tonsillar microenvironmental cues favor a milieu that renders tonsil cells susceptible to HIV infection and underscore the role of local immune regulatory mechanisms which may account for the selectivity of HIV infection within mucosal compartments.