Early Colorectal Responses to HIV-1 and Modulation by Antiretroviral Drugs.

Innate responses during acute HIV infection correlate with disease progression and pathogenesis. However, limited information is available about the events occurring during the first hours of infection in the mucosal sites of transmission. With an ex vivo HIV-1 challenge model of human colorectal tissue we assessed the mucosal responses induced by R5- and X4-tropic HIV-1 isolates in the first 24 h of exposure. Microscopy studies demonstrated virus penetration of up to 39 µm into the lamina propia within 6 h of inoculation. A rapid, 6 h post-challenge, increase in the level of secretion of inflammatory cytokines, chemokines, interferon- γ (IFN-γ), and granulocyte-macrophage colony-stimulating factor (GM-CSF) was observed following exposure to R5- or X4-tropic isolates. This profile persisted at the later time point measured of 24 h. However, exposure to the X4-tropic isolate tested induced greater changes at the proteomic and transcriptomic levels than the R5-tropic. The X4-isolate induced greater levels of CCR5 ligands (RANTES, MIP-1α and MIP-1ß) secretion than R5-HIV-1. Potential drugs candidates for colorectal microbicides, including entry, fusion or reverse transcriptase inhibitors demonstrated differential capacity to modulate these responses. Our findings indicate that in colorectal tissue, inflammatory responses and a Th1 cytokine profile are induced in the first 24 h following viral exposure.

HIV-1-Specific IgA Monoclonal Antibodies from an HIV-1 Vaccinee Mediate Galactosylceramide Blocking and Phagocytosis.

Vaccine-elicited humoral immune responses comprise an array of antibody forms and specificities, with only a fraction contributing to protective host immunity. Elucidation of antibody effector functions responsible for protective immunity against human immunodeficiency virus type 1 (HIV-1) acquisition is a major goal for the HIV-1 vaccine field. Immunoglobulin A (IgA) is an important part of the host defense against pathogens; however, little is known about the role of vaccine-elicited IgA and its capacity to mediate antiviral functions. To identify the antiviral functions of HIV-1-specific IgA elicited by vaccination, we cloned HIV-1 envelope-specific IgA monoclonal antibodies (MAbs) by memory B cell cultures from peripheral blood mononuclear cells from an RV144 vaccinee and produced two IgA clonal cell lines (HG129 and HG130) producing native, nonrecombinant IgA MAbs. The HG129 and HG130 MAbs mediated phagocytosis by monocytes, and HG129 blocked HIV-1 Env glycoprotein binding to galactosylceramide, an alternative HIV-1 receptor. These findings elucidate potential antiviral functions of vaccine-elicited HIV-1 envelope-specific IgA that may act to block HIV-1 acquisition at the portal of entry by preventing HIV-1 binding to galactosylceramide and mediating antibody Fc receptor-mediated virion phagocytosis. Furthermore, these findings highlight the complex and diverse interactions of vaccine-elicited IgA with pathogens that depend on IgA fine specificity and form (e.g., multimeric or monomeric) in the systemic circulation and mucosal compartments.IMPORTANCE Host-pathogen interactions in vivo involve numerous immune mechanisms that can lead to pathogen clearance. Understanding the nature of antiviral immune mechanisms can inform the design of efficacious HIV-1 vaccine strategies. Evidence suggests that both neutralizing and nonneutralizing antibodies can mediate some protection against HIV in animal models. Although numerous studies have characterized the functional properties of HIV-1-specific IgG, more studies are needed on the functional attributes of HIV-1-specific IgA, specifically for vaccine-elicited IgA. Characterization of the functional properties of HIV-1 Env-specific IgA monoclonal antibodies from human vaccine clinical trials are critical toward understanding the capacity of the host immune response to block HIV-1 acquisition.

Inhibition of the transport of HIV in vitro using a pH-responsive synthetic mucin-like polymer system.

In conjunction with the routine role of delivering the active ingredient, carefully designed drug delivery vehicles can also provide ancillary functions that augment the overall efficacy of the system. Inspired by the ability of the cervicovaginal mucus to impede the movement of HIV virions at acidic pH, we have engineered a pH-responsive synthetic polymer that shows improved barrier properties over the naturally occurring cervicovaginal mucus by inhibiting viral transport at both acidic and neutral pH. The pH-responsive synthetic mucin-like polymer is constructed with phenylboronic acid (PBA) and salicylhydroxamic acid (SHA), each individually copolymerized with a 2-hydroxypropyl methacrylamide (pHPMA) polymer backbone. At pH 4.8, the crosslinked polymers form a transient network with a characteristic relaxation time of 0.9 s and elastic modulus of 11 Pa. On addition of semen, the polymers form a densely crosslinked elastic network with a characteristic relaxation time greater than 60 s and elastic modulus of 1800 Pa. Interactions between the PBA-SHA crosslinked polymers and mucin at acidic pH showed a significant increase in elastic modulus and crosslink lifetime (p < 0.05). A transport assay revealed that migration of HIV and cells was significantly impeded by the polymer network at pH ≥ 4.8 with a diffusion coefficient of 1.60 x 10(-4) µm(2)/s for HIV. Additionally, these crosslinked polymers did not induce symptoms of toxicity or irritation in either human vaginal explants or a mouse model. In summary, the pH-responsive crosslinked polymer system reported here holds promise as a class of microbicide delivery vehicle that could inhibit the transport of virions from semen to the target tissue and, thereby, contribute to the overall activity of the microbicide formulation.