IFN-gamma-activated monocytes weakly produce HIV-1 but induce the recruitment of HIV-sensitive T cells and enhance the viral production by these recruited T cells

Monocyte recruitment to the dermis and differentiation to dendritic cells increases the targets for dengue virus replication

Dengue virus (DENV) causes the most prevalent arthropod-borne viral disease in humans. Although Aedes mosquitoes transmit DENV when probing for blood in the skin, no information exists on DENV infection and immune response in the dermis, where the blood vessels are found. DENV suppresses the interferon response, replicates, and causes disease in humans but not wild-type mice. Here, we used mice lacking the interferon-α/β receptor (Ifnar(-/-)), which had normal cell populations in the skin and were susceptible to intradermal DENV infection, to investigate the dynamics of early DENV infection of immune cells in the skin. CD103(+) classical dendritic cells (cDCs), Ly6C(-) CD11b(+) cDCs, and macrophages in the steady-state dermis were initial targets of DENV infection 12-24 hours post-inoculation but then decreased in frequency. We demonstrated recruitment of adoptively-transferred Ly6C(high) monocytes from wild-type and Ifnar(-/-) origin to the DENV-infected dermis and differentiation to Ly6C(+) CD11b(+) monocyte-derived DCs (moDCs), which became DENV-infected after 48 hours, and were then the major targets for virus replication. Ly6C(high) monocytes that entered the DENV-infected dermis expressed chemokine receptor CCR2, likely mediating recruitment. Further, we show that ∼ 100-fold more hematopoietic cells in the dermis were DENV-infected compared to Langerhans cells in the epidermis. Overall, these results identify the dermis as the main site of early DENV replication and show that DENV infection in the skin occurs in two waves: initial infection of resident cDCs and macrophages, followed by infection of monocytes and moDCs that are recruited to the dermis. Our study reveals a novel viral strategy of exploiting monocyte recruitment to increase the number of targets for infection at the site of invasion in the skin and highlights the skin as a potential site for therapeutic action or intradermal vaccination.

Phenotype and functionality of CD4+ and CD8+ T cells in the upper reproductive tract of healthy premenopausal women

PROBLEM

The goal of this study was to investigate the phenotype and functional responsiveness of CD4(+) and CD8(+) T-cells in the upper reproductive tract of healthy premenopausal women. The lower reproductive tract is frequently studied as a site of sexually transmitted infections; however, the upper reproductive tract may also be a portal of entry and dissemination for pathogens, including HIV-1.

METHOD OF STUDY

Endometrial biopsy, endocervical curettage, cytobrush, and blood were collected during mid-luteal phase from 23 healthy women. T-cells were isolated and analyzed by flow cytometry.

RESULTS

As compared with their counterparts in blood, endometrial and endocervical T-cells had enhanced CCR5 expression, and were enriched for activated, effector memory cells. Endometrial T-cells were more responsive to polyclonal stimuli, producing a broad range of cytokines and chemokines.

CONCLUSION

These findings underscore the responsiveness of endometrial T-cells to stimulation, and reveal their activated phenotype. These findings also suggest susceptibility of the upper reproductive tract to HIV-1 infection.

Adaptive HIV-specific B cell-derived humoral immune defenses of the intestinal mucosa in children exposed to HIV via breast-feeding

Background

We evaluated whether B cell-derived immune defenses of the gastro-intestinal tract are activated to produce HIV-specific antibodies in children continuously exposed to HIV via breast-feeding.

Methods

Couples of HIV-1-infected mothers (n = 14) and their breastfed non HIV-infected (n = 8) and HIV-infected (n = 6) babies, and healthy HIV-negative mothers and breastfed babies (n = 10) as controls, were prospectively included at the Complexe Pédiatrique of Bangui, Central African Republic. Immunoglobulins (IgA, IgG and IgM) and anti-gp160 antibodies from mother’s milk and stools of breastfed children were quantified by ELISA. Immunoaffinity purified anti-gp160 antibodies were characterized functionally regarding their capacity to reduce attachment and/or infection of R5- and X4- tropic HIV-1 strains on human colorectal epithelial HT29 cells line or monocyte-derived-macrophages (MDM).

Results

The levels of total IgA and IgG were increased in milk of HIV-infected mothers and stools of HIV-exposed children, indicating the activation of B cell-derived mucosal immunity. Breast milk samples as well as stool samples from HIV-negative and HIV-infected babies exposed to HIV by breast-feeding, contained high levels of HIV-specific antibodies, mainly IgG antibodies, less frequently IgA antibodies, and rarely IgM antibodies. Relative ratios of excretion by reference to lactoferrin calculated for HIV-specific IgA, IgG and IgM in stools of HIV-exposed children were largely superior to 1, indicating active production of HIV-specific antibodies by the intestinal mucosa. Antibodies to gp160 purified from pooled stools of HIV-exposed breastfed children inhibited the attachment of HIV-1NDK on HT29 cells by 63% and on MDM by 77%, and the attachment of HIV-1JRCSF on MDM by 40%; and the infection of MDM by HIV-1JRCSF by 93%.

Conclusions

The intestinal mucosa of children exposed to HIV by breast-feeding produces HIV-specific antibodies harbouring in vitro major functional properties against HIV. These observations lay the conceptual basis for the design of a prophylactic vaccine against HIV in exposed children.

HIV-1 Trans Infection of CD4(+) T Cells by Professional Antigen Presenting Cells

Since the 1990s we have known of the fascinating ability of a complex set of professional antigen presenting cells (APCs; dendritic cells, monocytes/macrophages, and B lymphocytes) to mediate HIV-1 trans infection of CD4(+) T cells. This results in a burst of virus replication in the T cells that is much greater than that resulting from direct, cis infection of either APC or T cells, or trans infection between T cells. Such APC-to-T cell trans infection first involves a complex set of virus subtype, attachment, entry, and replication patterns that have many similarities among APC, as well as distinct differences related to virus receptors, intracellular trafficking, and productive and nonproductive replication pathways. The end result is that HIV-1 can sequester within the APC for several days and be transmitted via membrane extensions intracellularly and extracellularly to T cells across the virologic synapse. Virus replication requires activated T cells that can develop concurrently with the events of virus transmission. Further research is essential to fill the many gaps in our understanding of these trans infection processes and their role in natural HIV-1 infection.

Understanding factors that modulate HIV infection at the female genital tract mucosae for the rationale design of microbicides

Women are now becoming the pivot of the epidemiological spread of HIV infection worldwide, especially in developing countries. Therefore, research to develop an efficient microbicide is now a priority for the prevention of HIV-1 acquisition in exposed women. However, recent disappointing failures in microbicide clinical trials revealed major gaps in basic and applied knowledge that hinder the development of effective microbicide formulations. Indeed, the inhibitory power of microbicide molecules may be affected by several physiological and immunological factors present in male and female genital tracts. Furthermore, mucosal crossing of HIV-1 to increase the ability to reach the submucosal target cells (macrophages, lymphocytes, and dendritic cells) may be modulated by supraepithelial factors such as seminal complement components (opsonized HIV-1), by epithelial factors released in the submucosal microenvironment such as antimicrobial soluble factors, cytokines, and chemokines, and by potent intraepithelial and submucosal innate immunity. The design of vaginal microbicide formulations should take into account an understanding of the intimate mechanisms involved in the crossing of HIV through the female genital mucosae, in the context of a mixture of both male and female genital fluids.

Differential activity of candidate microbicides against early steps of HIV-1 infection upon complement virus opsonization

Background

HIV-1 in genital secretions may be opsonized by several molecules including complement components. Opsonized HIV-1 by complement enhances the infection of various mucosal target cells, such as dendritic cells (DC) and epithelial cells.

Results

We herein evaluated the effect of HIV-1 complement opsonization on microbicide candidates' activity, by using three in vitro mucosal models: CCR5-tropic HIV-1_JR-CSF transcytosis through epithelial cells, HIV-1_JR-CSF attachment on immature monocyte-derived dendritic cells (iMDDC), and infectivity of iMDDC by CCR5-tropic HIV-1_BaL and CXCR4-tropic HIV-1_NDK. A panel of 10 microbicide candidates [T20, CADA, lectines HHA & GNA, PVAS, human lactoferrin, and monoclonal antibodies IgG1B12, 12G5, 2G12 and 2F5], were investigated using cell-free unopsonized or opsonized HIV-1 by complements. Only HHA and PVAS were able to inhibit HIV trancytosis. Upon opsonization, transcytosis was affected only by HHA, HIV-1 adsorption on iMDDC by four molecules (lactoferrin, IgG1B12, IgG2G5, IgG2G12), and replication in iMDDC of HIV-1_BaL by five molecules (lactoferrin, CADA, T20, IgG1B12, IgG2F5) and of HIV-1_NDK by two molecules (lactoferrin, IgG12G5).

Conclusion

These observations demonstrate that HIV-1 opsonization by complements may modulate in vitro the efficiency of candidate microbicides to inhibit HIV-1 infection of mucosal target cells, as well as its crossing through mucosa.

Apical interactions of HIV type 1 with polarized HEC-1 cell monolayer modulate R5-HIV type 1 spread by submucosal macrophages

The in vitro model of HIV-1 transcytosis through a monolayer of HEC-1 cells is thought to mimic the mucosal crossing of the virus that may occur in vivo. We evaluated whether the stimulation of HEC-1 by HIV may modulate HIV infection of macrophages. Thus, the ability to capture, produce, and transfer R5 viruses to T cells, attract T cells, and finally produce cytokines/chemokines, was compared between untreated macrophages (M0) and macrophages differentiated in the presence of medium collected at the basolateral pole of HEC-1, which were unstimulated [M(BL)] or stimulated with either R5-HIV-1Ba-L [M(BL-R5)] or X4-HIV-1NDK [M(BL-X4)]. M(BL-X4)-secreted CCR5-interacting chemokines integrated and replicated HIV less efficiently than did M(BL) and M(BL-R5). M(BL-R5) and M(BL-X4) similarly transmitted HIV to activated T cells. Interestingly, mannose-binding receptors and heparan sulfate proteoglycans were variously involved in HIV adsorption, whereas DC-SIGN mostly mediated the HIV transfer. Conversely to M(BL) and M(BL-X4), M(BL-R5) did not secrete eotaxin, GRO, ITAC, lymphotactin, MIP-1, MIP-3, and RANTES, which was associated with a weak capacity to recruit CD4(+)CXCR4(+)CCR5(+) T cells. In particular, M(BL-R5) specifically released soluble factors enhancing HIV production by recruited T cells. These submucosal-conditioned macrophages differentially captured, produced, and transferred R5-HIV-1 to T cells, according to the tropism of the virus deposited at the apical pole of HEC-1. These observations challenge the question of the in vivo involvement of HIV-1 as a supraepithelial stimulus that likely modulates the susceptibility for HIV-1 of submucosal target cells in favor of its transmission.

Early events in vaginal HIV transmission: implications in microbicide development

In vitro models for HIV crossing through mucosae include direct infection of epithelial cells, transcytosis through epithelial cells, epithelial transmigration of infected donor cells, uptake by intraepithelial dendritic cells, and circumvention of the epithelial barrier through physical breaches. Mucosal crossing of HIV for further reaching of the submucosal target cells (macrophages, lymphocytes and dendritic cells) may be modulated by supraepithelial factors, such as seminal complement components (opsonized HIV), by epithelial factors released in the submucosal microenvironment, such as antimicrobial soluble factors, cytokines and chemokines, and by the potent intraepithelial and submucosal innate immunity. Poor understanding of the subtle and complex orchestration of the numerous virus and cell factors involved in HIV mucosal crossing renders the design of effective microbicide formulations difficult. Thus, there is currently no clear relationship between the success of preclinical development of microbicide formulations, using the available assays of anti-HIV efficacy and mucosal toxicity, and its efficacy against HIV acquisition in women enrolled in a large-scale Phase III trial. In addition, the proof of concept that a microbicide formulation may be efficient outside the laboratory has not yet been clearly demonstrated. Finally, there is an urgent need to better understand and modelize the early events occurring during the first hours of HIV contact with the female genital mucosae, especially considering the enormous gaps of knowledge in the understanding of the mechanisms of HIV mucosal crossing through female genital mucosae.

Pre-clinical development as microbicide of zinc tetra-ascorbo-camphorate, a novel terpenoid derivative: potent in vitro inhibitory activity against both R5- and X4-tropic HIV-1 strains without significant in vivo mucosal toxicity

Background

Terpenoid derivatives originating from many plants species, are interesting compounds with numerous biological effects, such as anti-HIV-1 activity. The zinc tetra-ascorbo-camphorate complex (or "C14"), a new monoterpenoid derivative was evaluated in vitro for its anti-HIV-1 activity on both R5- and X4-HIV-1 infection of primary target cells (macrophages, dendritic cells and T cells) and on HIV-1 transfer from dendritic cells to T cells.

Results

The toxicity study was carried out in vitro and also with the New Zealand White rabbit vaginal irritation model. C14 was found to be no cytotoxic at high concentrations (CC50 > 10 μM) and showed to be a potential HIV-1 inhibitor of infection of all the primary cells tested (EC50 = 1 μM). No significant changes could be observed in cervicovaginal tissue of rabbit exposed during 10 consecutive days to formulations containing up to 20 μM of C14.

Conclusion

Overall, these preclinical studies suggest that zinc tetra-ascorbo-camphorate derivative is suitable for further testing as a candidate microbicide to prevent male-to-female heterosexual acquisition of HIV-1.

HIV-1 p17 binds heparan sulfate proteoglycans to activated CD4(+) T cells

We have previously shown that HIV-1 p17 binds to activated peripheral blood mononuclear cells and enhances secretion of pro-inflammatory cytokines, but we were unable to define a ligand on activated cells. In this work we evaluate the hypothesis that HIV-1 p17 may be a heparin/heparan sulfate-binding protein. HIV-1 p17 contains C- and N-terminal sequences with positively charged residues and a consensus cluster for heparin binding. We demonstrated by affinity chromatography that HIV-1 p17 binds strongly to heparin-agarose at physiological pH. Soluble heparins and heparan sulfate but not chondroitin 4-sulfate and dextran sulfate inhibit binding of HIV-1 p17 to heparin solid phase and to activated CD4(+) T cells. Furthermore the inhibition of cell sulfatation by chlorate treatment completely counteracts HIV-1 p17 binding to activated cells. These results indicate for the first time that HIV-1 p17 can be ascribed to the heparin binding protein family and suggest that this interaction might play a key role in the ability of the protein to induce an inflammatory effect on activated cells.

Differential in vitro inhibitory activity against HIV-1 of alpha-(1-3)- and alpha-(1-6)-D-mannose specific plant lectins: implication for microbicide development

BACKGROUND

Plant lectins such as Galanthus nivalis agglutinin (GNA) and Hippeastrum hybrid agglutinin (HHA) are natural proteins able to link mannose residues, and therefore inhibit HIV-target cell interactions. Plant lectins are candidate for microbicide development.

OBJECTIVE

To evaluate the activity against HIV of the mannose-specific plant lectins HHA and GNA at the cellular membrane level of epithelial cells and monocyte-derived dendritic cells (MDDC), two potential target cells of HIV at the genital mucosal level.

METHODS

The inhibitory effects of HHA and GNA were evaluated on HIV adsorption to genital epithelial HEC-1A cell line, on HIV transcytosis throughout a monolayer of polarized epithelial HEC-1A cells, on HIV adsorption to MDDC and on transfer of HIV from MDDC to autologous T lymphocytes.

RESULTS

HHA faintly inhibited attachment to HEC-1A cells of the R5-tropic HIV-1Ba-L strain, in a dose-dependent manner, whereas GNA moderately inhibited HIV adsorption in the same context, but only at high drug doses. Only HHA, but not GNA, inhibited HIV-1JR-CSF transcytosis in a dose-dependent manner. By confocal microscopy, HHA, but not GNA, was adsorbed at the epithelial cell surface, suggesting that HHA interacts specifically with receptors mediating HIV-1 transcytosis. Both plant lectins partially inhibited HIV attachment to MDDC. HHA inhibited more efficiently the transfer of HIV from MDDC to T cell, than GNA. Both HHA and GNA lacked toxicity below 200 microg/ml irrespective the cellular system used and do not disturb the monolayer integrity of epithelial cells.

CONCLUSION

These observations demonstrate higher inhibitory activities of the lectin plant HHA by comparison to GNA, on HIV adsorption to HEC-1A cell line, HIV transcytosis through HEC-1A cell line monolayer, HIV adsorption to MDDC and HIV transfer from MDDC to T cells, highlighting the potential interest of HHA as effective microbicide against HIV.