Langerhans cell as primary target and vehicle for transmission of HIV

MiR-23a Regulates Skin Langerhans Cell Phagocytosis and Inflammation-Induced Langerhans Cell Repopulation

Langerhans cells (LCs) are skin-resident macrophage that act similarly to dendritic cells for controlling adaptive immunity and immune tolerance in the skin, and they are key players in the development of numerous skin diseases. While TGF-β and related downstream signaling pathways are known to control numerous aspects of LC biology, little is known about the epigenetic signals that coordinate cell signaling during LC ontogeny, maintenance, and function. Our previous studies in a total miRNA deletion mouse model showed that miRNAs are critically involved in embryonic LC development and postnatal LC homeostasis; however, the specific miRNA(s) that regulate LCs remain unknown. miR-23a is the first member of the miR-23a-27a-24-2 cluster, a direct downstream target of PU.1 and TGF-b, which regulate the determination of myeloid versus lymphoid fates. Therefore, we used a myeloid-specific miR-23a deletion mouse model to explore whether and how miR-23a affects LC ontogeny and function in the skin. We observed the indispensable role of miR-23a in LC antigen uptake and inflammation-induced LC epidermal repopulation; however, embryonic LC development and postnatal homeostasis were not affected by cells lacking miR23a. Our results suggest that miR-23a controls LC phagocytosis by targeting molecules that regulate efferocytosis and endocytosis, whereas miR-23a promotes homeostasis in bone marrow-derived LCs that repopulate the skin after inflammatory insult by targeting Fas and Bcl-2 family proapoptotic molecules. Collectively, the context-dependent regulatory role of miR-23a in LCs represents an extra-epigenetic layer that incorporates TGF-b- and PU.1-mediated regulation during steady-state and inflammation-induced repopulation.

Syndecan 4 Upregulation on Activated Langerhans Cells Counteracts Langerin Restriction to Facilitate Hepatitis C Virus Transmission

Sexually transmitted Hepatitis C virus (HCV) infections and high reinfections are a major concern amongst men who have sex with men (MSM) living with HIV-1 and HIV-negative MSM. Immune activation and/or HIV-1 coinfection enhance HCV susceptibility via sexual contact, suggesting that changes in immune cells or external factors are involved in increased susceptibility. Activation of anal mucosal Langerhans cells (LCs) has been implicated in increased HCV susceptibility as activated but not immature LCs efficiently retain and transmit HCV to other cells. However, the underlying molecular mechanism of transmission remains unclear. Here we identified the Heparan Sulfate Proteoglycan Syndecan 4 as the molecular switch, controlling HCV transmission by LCs. Syndecan 4 was highly upregulated upon activation of LCs and interference with Heparan Sulfate Proteoglycans or silencing of Syndecan 4 abrogated HCV transmission. These data strongly suggest that Syndecan 4 mediates HCV transmission by activated LCs. Notably, our data also identified the C-type lectin receptor langerin as a restriction factor for HCV infection and transmission. Langerin expression abrogated HCV infection in HCV permissive cells, whereas langerin expression on the Syndecan 4 expressing cell line strongly decreased HCV transmission to a target hepatoma cell line. These data suggest that the balanced interplay between langerin restriction and Syndecan 4 transmission determines HCV dissemination. Silencing of langerin enhanced HCV transmission whereas silencing Syndecan 4 on activated LCs decreased transmission. Blocking Heparan Sulfate Proteoglycans abrogated HCV transmission by LCs ex vivo identifying Heparan Sulfate Proteoglycans and Syndecan 4 as potential targets to prevent sexual transmission of HCV. Thus, our data strongly suggest that the interplay between receptors promotes or restricts transmission and further indicate that Syndecan 4 is the molecular switch controlling HCV susceptibility after sexual contact.

TIM-4 is differentially expressed in the distinct subsets of dendritic cells in skin and skin-draining lymph nodes and controls skin Langerhans cell homeostasis

T cell immunoglobulin and mucin-4 (TIM-4), mainly expressed on dendritic cells (DC) and macrophages, plays an essential role in regulating immune responses. Langerhans cells (LC), which are the sole DC subpopulation residing at the epidermis, are potent mediators of immune surveillance and tolerance. However, the significance of TIM-4 on epidermal LCs, along with other cutaneous DCs, remains totally unexplored. For the first time, we discovered that epidermal LCs expressed TIM-4 and displayed an increased level of TIM-4 expression upon migration. We also found that dermal CD207⁺ DCs and lymph node (LN) resident CD207⁻CD4⁺ DCs highly expressed TIM-4, while dermal CD207⁻ DCs and LN CD207⁻CD4⁻ DCs had limited TIM-4 expressions. Using TIM-4-deficient mice, we further demonstrated that loss of TIM-4 significantly upregulated the frequencies of epidermal LCs and LN resident CD207⁻CD4⁺ DCs. In spite of this, the epidermal LCs of TIM-4-deficient mice displayed normal phagocytic and migratory abilities, comparable maturation status upon the stimulation as well as normal repopulation under the inflamed state. Moreover, lack of TIM-4 did not affect dinitrofluorobenzene-induced contact hypersensitivity response. In conclusion, our results indicated that TIM-4 was differentially expressed in the distinct subsets of DCs in skin and skin-draining LNs, and specifically regulated epidermal LC and LN CD207⁻CD4⁺ DC homeostasis.

Immune Suppression by Myeloid Cells in HIV Infection: New Targets for Immunotherapy

Over thirty years of extensive research has not yet solved the complexity of HIV pathogenesis leading to a continued need for a successful cure. Recent immunotherapy-based approaches are aimed at controlling the infection by reverting immune dysfunction. Comparatively less appreciated than the role of T cells in the context of HIV infection, the myeloid cells including macrophages monocytes, dendritic cells (DCs) and neutrophils contribute significantly to immune dysfunction. Host restriction factors are cellular proteins expressed in these cells which are circumvented by HIV. Guided by the recent literature, the role of myeloid cells in HIV infection will be discussed highlighting potential targets for immunotherapy. HIV infection, which is mainly characterized by CD4 T cell dysfunction, also manifests in a vicious cycle of events comprising of inflammation and immune activation. Targeting the interaction of programmed death-1 (PD-1), an important regulator of T cell function; with PD-L1 expressed mainly on myeloid cells could bring promising results. Macrophage functional polarization from pro-inflammatory M1 to anti-inflammatory M2 and vice versa has significant implications in viral pathogenesis. Neutrophils, recently discovered low density granular cells, myeloid derived suppressor cells (MDSCs) and yolk sac macrophages provide new avenues of research on HIV pathogenesis and persistence. Recent evidence has also shown significant implications of neutrophil extracellular traps (NETs), antimicrobial peptides and opsonizing antibodies. Further studies aimed to understand and modify myeloid cell restriction mechanisms have the potential to contribute in the future development of more effective anti-HIV interventions that may pave the way to viral eradication.

Dendritic Cells in HIV-1 and HCV Infection: Can They Help Win the Battle?

Persistent infections with human immunodeficiency virus type 1 (HIV-1) and hepatitis C virus (HCV) are a major cause of morbidity and mortality worldwide. As sentinels of our immune system, dendritic cells (DCs) play a central role in initiating and regulating a potent antiviral immune response. Recent advances in our understanding of the role of DCs during HIV-1 and HCV infection have provided crucial insights into the mechanisms employed by these viruses to impair DC functions in order to evade an effective immune response against them. Modulation of the immunological synapse between DC and T-cell, as well as dysregulation of the crosstalk between DCs and natural killer (NK) cells, are emerging as two crucial mechanisms. This review focuses on understanding the interaction of HIV-1 and HCV with DCs not only to understand the immunopathogenesis of chronic HIV-1 and HCV infection, but also to explore the possibilities of DC-based immunotherapeutic approaches against them. Host genetic makeup is known to play major roles in infection outcome and rate of disease progression, as well as response to anti-viral therapy in both HIV-1 and HCV-infected individuals. Therefore, we highlight the genetic variations that can potentially affect DC functions, especially in the setting of chronic viral infection. Altogether, we address if DCs’ potential as critical effectors of antiviral immune response could indeed be utilized to combat chronic infection with HIV-1 and HCV.

Pathophysiology of Langerhans cells

Langerhans cells (LCs) were first described by Paul Langerhans, in 1868, as dendritically shaped cells, which were located in the squamous epithelia of epidermis. Later on, these cells were identified in all stratified squamous epithelium of mammals. Dendritic cells (DCs) play an important role in local defense mechanisms in the epithelium. LCs are situated usually in the suprabasal layer of stratified squamous epithelia of oral mucosa and epidermis of skin. They constitute 3% of the cell population in epidermis. LCs are thought to act as antigen presenting cells (APCs) during initiation of immune responses. With the help of APCs, the lymphocytes are able to recognize and respond to specific microbes. In this paper we have reviewed the origin, distribution, demonstration and mechanism of action of LCs and their role in different pathological conditions.

HIV impairment of immune responses in dendritic cells

Dendritic cells and their subsets are diverse populations of immune cells in the skin and mucous membranes that possess the ability to sense the presence of microbes and orchestrate an efficient and adapted immune response. Dendritic cells (DC) have the unique ability to act as a bridge between the innate and adaptive immune responses. These cells are composed of a number of subsets behaving with preferential and specific features depending on their location and surrounding environment. Langerhans cells (LC) or dermal DC (dDC) are readily present in mucosal areas. Other DC subsets such as plasmacytoid DC (pDC), myeloid DC (myDC), or monocyte-derived DC (MDDC) are thought to be recruited or differentiated in sites of pathogenic challenge. Upon HIV infection, DC and their subsets are likely among the very first immune cells to encounter incoming pathogens and initiate innate and adaptive immune responses. However, as evidenced during HIV infection, some pathogens have evolved subtle strategies to hijack key cellular machineries essential to generate efficient antiviral responses and subvert immune responses for spread and survival.In this chapter, we review recent research aimed at investigating the involvement of DC subtypes in HIV transmission at mucosal sites, concentrating on HIV impact on cellular signalling and trafficking pathways in DC leading to DC-mediated immune response alterations and viral immune evasion. We also address some aspects of DC functions during the chronic immune pathogenesis and conclude with an overview of the current and novel therapeutic and prophylactic strategies aimed at improving DC-mediated immune responses, thus to potentially tackle the early events of mucosal HIV infection and spread.

Dendritic-cell interactions with HIV: infection and viral dissemination

Dendritic cells (DCs) are crucial for the generation and the regulation of adaptive immunity. Because DCs have a pivotal role in marshalling immune responses, HIV has evolved ways to exploit DCs, thereby facilitating viral dissemination and allowing evasion of antiviral immunity. Defining the mechanisms that underlie cell-cell transmission of HIV and understanding the role of DCs in this process should help us in the fight against HIV infection. This Review highlights the latest advances in our understanding of the interactions between DCs and HIV, focusing on the mechanisms of DC-mediated viral dissemination.

HIV-1 and the hijacking of dendritic cells: a tug of war

Dendritic cells are critical for host immunity and are involved both in the innate and adaptive immune responses. They are among the first cells targeted by HIV-1 in vivo at mucosal sites. Dendritic cells can sequester HIV-1 in endosomal compartments for several days and transmit infectious HIV-1 to interacting T cells in the lymph node, which is the most important site for viral replication and spread. Initially, the cellular immune response developed against HIV-1 is strong, but eventually it fails to control and resolve the infection. The most dramatic effect seen on the immune system during untreated HIV-1 infection is the destruction of helper CD4(+) T cells, which leads to subsequent immune deficiency. However, the immunomodulatory effects of HIV-1 on different dendritic cell subpopulations may also play an important role in the pathogenesis of HIV-1. This review discusses the effects HIV-1 exerts on dendritic cells in vivo and in vitro, including the binding and uptake of HIV by dendritic cells, the formation of infectious synapses, infection, and the role of dendritic cells in HIV-1 pathogenesis.

The role of dendritic cells in the pathogenesis of HIV-1 infection

Dendritic cells are professional antigen-presenting cells required for generation of adaptive immunity. These cells are one of the initial target cells for HIV-1 infection or capture of virions at site of transmission in the mucosa. DCs carrying HIV-1 will migrate to the lymphoid tissue where they can contribute to the dissemination of the virus to adjacent CD4+ T cells. In addition, HIV-1-exposed DCs may have impaired antigen-presenting capacity resulting in inadequate expansion of HIV-1-specific T cell responses. Here, we review the infection of different subtypes of DCs by HIV-1 and the relevance of these cells in the transmission and establishment of HIV-1 disease. In addition, we discuss the mechanisms through which HIV-1-DC interactions could be exploited to optimise the generation and maintenance of HIV-1-specific T cell immunity.

Positive and negative aspects of the human immunodeficiency virus protease: development of inhibitors versus its role in AIDS pathogenesis

In this review we summarize multiple aspects of the human immunodeficiency virus (HIV) protease from both structural and functional viewpoints. After an introductory overview, we provide an up-to-date status report on protease inhibitors (PI). This proceeds from a discussion of PI structural design, to how PI are optimally utilized in highly active antiretroviral triple therapy (one PI along with two reverse transcriptase inhibitors), the emergence of PI resistance, and the natural role of secretory leukocyte PI. Then we switch to another focus: the interaction of HIV protease with other genes in acute and persistent infection, which in turn may have an effect on AIDS pathogenesis. We conclude with a discussion on future directions in HIV treatment, involving multiple-target anti-HIV therapy, vaccine development, and novel reactivation-inhibitory reagents.

Dendritic cells transmit human immunodeficiency virus type 1 to monocytes and monocyte-derived macrophages

Previous studies have shown that human immunodeficiency virus type 1 (HIV-1) exploits dendritic cells (DC) to replicate and spread among CD4(+) T cells. To explain the predominance of non-syncytium-inducing (NSI) over syncytium-inducing (SI) strains during the initial viremia of HIV, we investigated the ability of blood monocyte (Mo)-derived DC to transmit HIV-1 to CD4(+) cells of the monocytoid lineage. First, we demonstrate that in our system, DC are able to transmit NSI strains, but not SI strains, of HIV-1 to fresh blood Mo and to Mo-derived macrophages (MDM). To establish a productive infection, a 10-fold-lower amount of virus was necessary for DC-mediated transmission of HIV-1 to Mo than in case of cell-free infection. Second, immature CD83(-) DC (imDC) transmit virus to Mo and MDM with higher efficacy compared to mature CD83(+) DC (maDC); this finding is in contrast to data previously obtained with CD4(+) T cells. Third, maturation from imDC to maDC efficiently silenced expression of beta2-integrins CD11b, CD11c, and CD18 by maDC. Moreover, monoclonal antibody against CD18 inhibited transmission of HIV-1 from imDC to Mo. We propose that the adhesion molecules of the CD11/CD18 family, involved in cell-cell interactions of DC with the microenvironment, may play a major role in imDC-mediated HIV-1 infection of Mo and MDM.

Cellular targets of infection and route of viral dissemination after an intravaginal inoculation of simian immunodeficiency virus into rhesus macaques

We used the simian immunodeficiency virus (SIV)/rhesus macaque model to study events that underlie sexual transmission of human immunodeficiency virus type 1 (HIV-1). Four female rhesus macaques were inoculated intravaginally with SIVmac251, and then killed 2, 5, 7, and 9 d later. A technique that detected polymerase chain reaction-amplified SIV in situ showed that the first cellular targets for SIV were in the lamina propria of the cervicovaginal mucosa, immediately subjacent to the epithelium. Phenotypic and localization studies demonstrated that many of the infected cells were likely to be dendritic cells. Within 2 d of inoculation, infected cells were identified in the paracortex and subcapsular sinus of the draining internal iliac lymph nodes. Subsequently, systemic dissemination of SIV was rapid, since culturable virus was detectable in the blood by day 5. From these results, we present a model for mucosal transmission of SIV and HIV-1.

Langerhans cells and HIV infection

Epidermal Langerhans cells (LCs) isolated from individuals infected with human immunodeficiency virus (HIV-1) harbour HIV-1 proviral DNA and RNA, indicating productive infection by the virus in vivo. Furthermore, normal LCs can be infected in vitro by HIV and can present HIV antigens to helper T cells. Here, Giovanna Zambruno and colleagues discuss the possibility that LCs of genital mucosae are among the first targets of HIV infection following sexual contact, and can be involved both in the transmission of the infection to T cells and in T-cell priming to HIV antigens. In addition, epidermal LCs might acquire HIV infection from dermal T cells during transit from blood vessels through the dermis and may, in turn, represent a reservoir of the virus for continued T-cell infection.

Langerhans cells: structure, function and role in oral pathological conditions

Langerhans cells (LCs) are dendritic bone marrow derived cells situated suprabasally in most stratified squamous epithelia, such as the epidermis and the epithelium of oral mucosa, including the gingiva. Langerhans cells are thought to act as antigen-presenting cells (APC) during induction of immune responses. The exact role of Langerhans cells in the oral mucosa is not fully understood although several investigations suggest that these cells are involved in reactions to antigen challenge under both normal and pathological situations. In this paper the structure, phenotypic markers and derivation of Langerhans cells are reviewed. In view of recent findings, the immunological characteristics and the implications of Langerhans cells in pathologic oral reactions are discussed.

Role of Langerhans cells and other dendritic cells in viral diseases

Langerhans cells are part of a vast system of potent antigen-presenting cells known under the name of dendritic cells. During the last decade, much has been learned on dendritic cell involvement in the immune response to infectious diseases. This review briefly summarizes our current understanding of the role played by Langerhans cells and other dendritic cells in the pathogenesis of DNA and RNA virus infections. These data may form the basis for the development of innovative approaches in the diagnosis, prevention, and treatment of viral diseases.

In vitro HIV-1 entry and replication in Langerhans cells may clarify the HIV-1 genome detection by PCR in epidermis of seropositive patients

Being dendritic antigen-presenting cells in skin and mucous membrane, Langerhans cells (LC) occur in areas at risk for inoculation by human immunodeficiency virus (HIV), and the question whether LC act as a target, reservoir, or vector for transmission of HIV has given rise to much controversy. To address this question, we first analyzed the epidermal compartment of skin from patients seropositive for HIV DNA. Second, we tested the susceptibility of each cell type normally found in this compartment to in vitro infection by HIV-1. A non-denatured DNA was obtained from epidermal sheets after a thermochemical treatment of biopsies (0.5 M ethylenediaminetetraacetic acid (EDTA), pH 7.5 at 60 degrees C for 90 seconds). Optimization of amplification of viral genome was performed with three primer pairs derived from gag, env, and pol sequences. Polymerase chain reaction (PCR) products were analyzed by Southern blot. Viral genome was found in five of 11 HIV-seropositive patients. To control the permissivity of epidermal cell population for HIV, cells isolated from the epidermal sheet of normal skin by trypsinization were co-cultured with HIV-1-carrying promonocytic cells (U937) and observed by electron microscopy. After 3-6 h of co-culture, numerous virions were either tightly bound or apparently engaged in the process of internalization through receptor-mediated endocytosis. At day 4 of co-culture, some infected LC appeared to release mature viral particles through bud formation. The in vitro HIV-1 entry and replication in LC may confirm the presence of the HIV-1 genome by PCR in epidermis of seropositive patients. The consequences of the permissivity of LC for HIV on the antigen-presenting function remain to be determined.

Interaction of human epidermal Langerhans cells with HIV-1 viral envelope proteins (gp 120 and gp 160s) involves a receptor-mediated endocytosis independent of the CD4 T4A epitope

The CD4 molecule is known to be the preferential receptor for the HIV-1 envelope glycoprotein. Epidermal Langerhans cells are dendritic cells which express several surface antigens, among them CD4 antigens. To clarify the exact role of CD4 molecules in Langerhans cell infection induced by HIV-1, we investigated the possible involvement of the interactions between HIV-1 gp 120 or HIV-1 gp 160s (soluble gp 160) and Langerhans cell surface. We also assessed the expression of CD4 molecules on Langerhans cell membranes dissociated by means of trypsin from their neighbouring keratinocytes. The cellular phenotype was monitored using flow cytometry and quantitative immunoelectron microscopy. We reported that human Langerhans cells can bind the viral envelope proteins (gp 120 or gp 160s), and that this binding does not depend on CD4 protein expression. This binding is not blocked by anti-CD4 monoclonal antibodies. We show that a proportion of gp 120/gp 160s-receptor complexes enters Langerhans cells by a process identified as a receptor-mediated endocytosis. The amount of surface bound gp 120/gp 160s is not consistent with the amount of CD4 antigens present on Langerhans cell membranes. Gp 120/gp 160s binding sites on Langerhans cell suspensions appeared to be trypsin resistant, while CD4 antigens (at least the epitopes known to bind the HIV-1) are trypsin sensitive. A burst of gp 120 receptor expression was detected on 1-day cultured Langerhans cells while CD4 antigens disappeared. These findings lead to the most logical conclusion that binding of gp 120/gp 160s is due to the presence of a Langerhans cell surface molecule different from CD4 antigens.

1 alpha,25-dihydroxyvitamin D3 inhibits productive infection of human monocytes by HIV-1

Pretreatment of freshly isolated human peripheral blood monocytes with the steroid hormone, 1 alpha,25-dihydroxyvitamin D3 (1,25(OH)D), markedly reduced (by 95%) productive infection of human monocytes by HIV-1. Equivalent concentrations (10nM) of 25-hydroxyvitamin D3 (25(OH)D), the biologic precursor of 1,25(OH)D, were ineffective at reducing either CD4 expression or HIV-1 production. Pretreatment was required for modulation of HIV-1 infection by 1,25(OH)D. Interestingly, 1,25(OH)D-mediated decreases in p24 antigen production were observed prior to any observed reduction in CD4 expression, suggesting that 1,25(OH)D treatment may modulate HIV-1 infection of monocytes through additional factors besides decreased HIV-1 binding. These data raise the possibility that 1,25(OH)D compounds may be important in host resistance to HIV-1.

Trypsin-resistant gp120 receptors are upregulated on short-term cultured human epidermal Langerhans cells

The CD4 molecule is known to be the preferential receptor for the HIV1 envelope glycoprotein. Epidermal Langerhans cells (LC) are dendritic cells which express several surface antigens, among them the CD4 antigens. LC infection was suggested when these cells were seen to present buddings coincident with membrane thickening of roughly 100 nm in size. These buddings were similar in ultrastructural aspect to HIV buddings on in vitro infected promonocytic cells (U937). To clarify the exact role of CD4 molecules in LC infection induced by HIV1, we investigated the possible involvement of between native and recombinant HIV1 gp120 and the LC surface. We also assessed the expression of CD4 molecules on LC membranes dissociated by means of trypsin from their neighbouring keratinocytes. The cellular phenotype was monitored using flow cytometry. We show that human LC can bind the viral envelope protein and that this binding does not depend on CD4 protein expression. The amount of surface bound gp120 was not consistent with the amount of CD4 antigens present on LC membranes. The gp120-binding sites on LC in suspension appear to be typsin-resistant while the CD4 antigens (at least the epitopes known to bind HIV1) are trypsin-sensitive. A burst of gp120 receptor expression was detected on 1-day cultured LC while the CD4 antigens disappeared. These findings lead to the logical conclusion that the binding of gp120 is due to the presence of a LC surface molecule which is different from CD4 antigens.

Langerhans cells in HIV-1 infection

The skin-specific immune surveillance system protects against invading microorganisms and transformed cells expressing tumor-specific neoantigens. This system includes antigen-presenting Langerhans cells, dermal and epidermal T lymphocytes, cytokine-producing keratinocytes, and draining peripheral lymph nodes. In patients infected with human immunodeficiency virus-1 (HIV-1), this surveillance system appears to be compromised, as evidenced by a reduction in the epidermal Langerhans cell population. Because human epidermal Langerhans cell express surface-bound CD4 antigens, HLA-DR antigens, and Fc-IgG receptors, all of which are involved in HIV-1 binding to, or entry into, the target cell, the reduction in Langerhans cells in patients with acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC) may be a direct consequence of HIV-1 infection and subsequent injury to Langerhans cells. Detailed ultrastructural studies have confirmed moderate to severe morphologic damage in some Langerhans cells of such patients and the presence of HIV-1-like particles on Langerhans cell surface membranes and in the extracellular spaces. The biologic consequences of Langerhans cell infection by HIV-1 could be either impaired antigen presentation function of viable Langerhans cells or possible transmission of the retrovirus to the T-cell compartment in skin or lymph nodes, with subsequent depletion of CD4+ T cells via widespread syncytia formation between HIV-1-infected and noninfected cells. The facts that herpes simplex virus, specific cytokines, and ultraviolet B radiation can activate signals for HIV-1 expression and that epidermal cells can elaborate large amounts of cytokines, particularly with enhanced ultraviolet B exposure, may have important clinical implications for HIV-1-infected patients.

Proliferation of HIV in lymphocyte--associated macrophages with cytopathic changes in AIDS erythroderma

Latency of the Human Immunodeficiency Virus (HIV) has been demonstrated in both helper T-Lymphocytes and cells of the macrophage/monocyte series. Although mitogen-dependent amplification of HIV infection within lymphocytes and monocytes/macrophages has been demonstrated to occur in vitro, in vivo evidence of such a phenomenon has been lacking. We have performed electron microscopic and immunocytochemical evaluation of skin biopsies from a patient with the Acquired Immunodeficiency Syndrome (AIDS) with chronic erythroderma. These biopsies provided evidence of proliferation of HIV in macrophages interacting with activated lymphocytes (CD3+). These macrophages were undergoing morphologic changes characteristic of cytopathicity and contained numerous viral particles, many of which were actively budding from plasma membranes. Cutaneous macrophages which were not interacting with lymphocytes did not demonstrate cytopathicity or evidence of viral multiplication. These in vivo data substantiate the concept that activation of cells which harbour latent HIV promotes viral replication as well as subsequent cytopathicity.

Neopterin and alpha-interferon in patients affected by Kaposi's sarcoma from Africa

The presence of circulating alpha-interferon and neopterin was investigated in sera of 47 patients affected by African Kaposi's sarcoma, both HIV-seropositive (13 patients) and HIV-seronegative (34 patients). For comparison, analyses were also performed in 20 HIV-seropositive symptomatic African subjects as well as in 20 African and 20 Italian healthy individuals. Alpha-interferon and neopterin levels appeared significantly higher in comparison with healthy control groups (P less than 0.001) but not with HIV-seropositve African individuals without Kaposi's sarcoma. Moreover, alpha-interferon and neopterin levels were significantly higher in progressive Kaposi's sarcoma (27 patients) than in regressive Kaposi's sarcoma (20 patients) (P less than 0.001). A significant correlation between alpha-interferon and neopterin was observed (r = 0.57; P less than 0.01). Furthermore, alpha-interferon levels of HIV-seropositive Kaposi's sarcoma patients resulted significantly higher in comparison with the seronegative ones (P less than 0.05). It is concluded that alpha-interferon and neopterin may be reliable prognostic markers in Kaposi's sarcoma patients.

Immunohistochemical study of normal skin of HIV-1-infected patients shows no evidence of infection of epidermal Langerhans cells by HIV

Langerhans cells (LC) are dendritic epidermal antigen-presenting cells expressing the surface molecule CD4, which renders them theoretical cellular targets for direct infection by the human immunodeficiency virus (HIV). To date, somewhat conflicting results have been reported concerning the in vivo infection of LC by HIV as well as the numerical alteration of these cells in the course of HIV infection. In the present work we studied clinically normal skin of a group of 44 HIV-1-seropositive patients classified according to the Centers for Disease Control (CDC) stages II (n = 14), III (n = 9), and IV (n = 21). Monoclonal antibodies (MAb) to HIV p18, p24, and gp120 and to HLA-DR and CD1a antigens (specific for LC) were applied on frozen skin sections using an amplification biotin-streptavidin-fluorescein technique. The MAb to HIV p18 cross-reacted with a cytoplasmic antigen of epidermal basal keratinocytes also present on HIV-seronegative skin specimens. No other reactivity was observed with any of the three anti-HIV MAb. The quantitative study showed that no significant correlations could be established between the number of LC (evaluated independently by HLA-DR and CD1a antigens) and the number of peripheral blood CD4+ve lymphocytes or the CDC disease stage. These results cast some doubt on the previously reported in vivo infection and numerical decrease in LC in HIV infection. The precise involvement of LC in HIV infection awaits further investigation.

Epidermal tumour necrosis factor alpha and interleukin 6-like activities in AIDS-related Kaposi's sarcoma. An immunohistological study

Biopsies from 6 patients with AIDS and Kaposi's sarcoma (KS) in the tumour stage, and 6 healthy controls, were immunohistologically examined for the presence of tissue-bound tumour necrosis factor alpha (TNF alpha) and interleukin 6 (IL-6) in the skin. TNF alpha was demonstrated using specific polyclonal antiserum to human recombinant TNF alpha. IL-6 was visualized indirectly using a polyclonal antiserum to partially purified human crude supernatants of activated human blood monocytes, followed by absorption with recombinant human IL-6. The cytokines were found identically located in epidermal cell membranes in stratum granulosum and spinosum of the epidermis from unaffected skin in both AIDS patients and in controls. Biopsies from KS elements showed markedly increased epidermal staining for both TNF delta and IL-6. It was not possible to detect TNF alpha or IL6 in the endothelial cells of the tumour. The observation of increased amounts of epidermal-bound TNF alpha and IL-6 in AIDS-related KS elements supplements previous studies indicating that the skin plays an active immunoinflammatory role in patients with AIDS.

Trends in sexual behaviour and risk factors for HIV infection among homosexual men, 1984-7

To assess whether the spread of infection with HIV can be reduced by changes in behaviour among groups most at risk because of their sexual practices sexual behaviour was monitored among 1050 homosexual men tested for HIV infection at a genitourinary medicine clinic in west London from November 1984 to September 1987. Four cohorts, defined by date of presentation, were studied by questionnaire at their presentation, and blood samples were analysed. Between the first and last cohorts there was a considerable fall in the proportion reporting casual relationships (291/329 (88%) v 107/213 (50%] and high risk activities, such as anoreceptive intercourse with casual partners (262/291 (90%) v 74/106 (70%], with the greatest changes occurring before the government information campaign began in 1986. Nevertheless, half of the men in the last cohort studied reported having casual partners. Multiple logistic regression showed that behavioural risk factors for HIV infection most closely resembled those for hepatitis B and that previous sexually transmitted diseases (syphilis, hepatitis B, and anogenital herpes) were themselves independent risk factors. A history of syphilis ranked above anoreceptive intercourse as the strongest predictor of HIV infection. Actively bisexual men showed a much lower prevalence of HIV infection (3/57, 5%) than exclusively homosexual men (113/375, 30%). Sexual behaviour among homosexual men changed during the period studied, and the incidence of HIV infection fell, although more education programmes directed at homosexual men are needed to re-emphasise the dangers of infection.

Role of epidermal Langerhans cells in viral infections

Langerhans cells function as highly potent antigen-presenting cells in the epidermis. In the last few years, their role in viral infections has been studied in various experimental systems. They have been shown to be involved in the pathogenesis of a number of infections of viral origin. These include vaccinia virus, human papilloma virus, herpes simplex virus, foot and mouth disease virus and human retrovirus infections. Studies on the effect of various factors, that are known to modulate the activity and density of Langerhans cell in the epidermis, may lead in the future to the development of new strategies aimed at inhibiting virus infections or even eradicating latent infection.