Distribution and infection of Langerhans cells in the skin of HIV-infected healthy subjects and AIDS patients

CD11c+CD123Low dendritic cell subset and the triad TNF-α/IL-17A/IFN-γ integrate mucosal and peripheral cellular responses in HIV patients with high-grade anal intraepithelial neoplasia: a systems biology approach

BACKGROUND

The incidence of anal cancer has increased over the past 25 years, and HIV/HPV coinfection is the most important risk factor for anal squamous cell carcinoma. In this study, we demonstrated that the evaluation of systemic and compartmentalized anal mucosa immune response is relevant to differentiating HIV(+) patients at risk of anal intraepithelial neoplasia (AIN).

METHODS

A systems biology approach was used to integrate different immunological parameters from anal mucosal tissue and peripheral blood assessed by phenotypic and intracytoplasmic analysis of lymphocytes and dendritic cell subsets.

RESULTS

Our data demonstrated that anal mucosal mononuclear cells from AIN(+)HIV(+) patients showed a robust capacity in producing proinflammatory/regulatory cytokines, mainly mTNF-α > IL-4 > IL-10 > IL-6 = IL-17A. Mucosal TNF-α/IFN-γ/IL-17A are selective high-grade squamous intraepithelial lesion (HSIL)-related biomarkers. Higher levels of circulating CD11cCD123cells and CD1a cells along with elevated levels of IFN-γCD4 T cells are major features associated with HSIL in AIN(+)HIV(+) patients. Regardless of the presence of AIN, HIV(+) patients presented a complex biomarker network, rich in negative connections. Among those patients, however, HSIL+ patients displayed stronger positive links between peripheral blood and anal mucosa environments, exemplified by the subnet of IL-17A/TNF-α/CD4IFN-γ/CD11cCD123 cells.

CONCLUSIONS

The significant association between HSIL and the levels of TNF-α/IL-17A/IFN-γ along with the different subsets of DCs present in the anal mucosa milieu should be studied in more detail as a way to identify and categorize HIV(+) patients vis à vis the high risk of anal cancer outcome.

Chinese human immunodeficiency virus-1 patients with different routes of transmission exhibit altered expression levels of blood dendritic cell subpopulations

Dendritic cells (DCs) play a pivotal role in the pathogenesis of human immunodeficiency virus-1 (HIV-1). Reduced numbers of blood DCs have been observed in individuals with chronic HIV-1 infection. In the present study, we analyzed the expression levels of monocytes, myeloid dendritic cell (mDC) precursors, mDCs, and plasmacytoid dendritic cells (pDCs), in HIV-1-infected patients in China who were infected via different routes of transmission, including heterosexual and homosexual sexual contact, and blood transmission through importation of blood or blood products, to further elucidate their role in HIV. Compared with HIV-negative individuals (n = 40), relative levels of CD11c+CD14⁻mDCs, CD11c++CD123(low) mDCs, and CD11c⁻CD123+ pDCs in total peripheral blood mononuclear cells (PBMCs) were significantly lower in all HIV patients (n = 93), and in those with blood transmission (n = 26) and heterosexual transmission (n = 43), while relative levels of CD11c+CD14⁻mDCs were significantly lower in HIV patients infected via homosexual transmission (n = 24). The results of correlation analysis demonstrated a significant negative correlation between CD4+ T-cell counts and the relative levels of CD11c++CD123(low) mDCs in HIV-I patients infected via blood transmission. There was no significant correlation between CD4+ T-cell counts and the expression level of other DC subpopulations in PBMCs from HIV patients. The results of this study suggest that HIV-1 patients with different routes of transmission exhibit altered expression levels of blood DC subpopulations, which contributes to dysregulated immune responses and pathogenesis of HIV-1.

Multiphoton high-resolution 3D imaging of Langerhans cells and keratinocytes in the mouse skin model adopted for epidermal powdered immunization

Langerhans cells (LCs) can be targeted with DNA-coated gold micro-projectiles ("Gene Gun") to induce potent cellular and humoral immune responses. It is likely that the relative volumetric distribution of LCs and keratinocytes within the epidermis impacts on the efficacy of Gene Gun immunization protocols. This study quantified the three-dimensional (3D) distribution of LCs and keratinocytes in the mouse skin model with a near-infrared multiphoton laser-scanning microscope (NIR-MPLSM). Stratum corneum (SC) and viable epidermal thickness measured with MPLSM was found in close agreement with conventional histology. LCs were located in the vertical plane at a mean depth of 14.9 microm, less than 3 mum above the dermo-epidermal boundary and with a normal histogram distribution. This likely corresponds to the fact that LCs reside in the suprabasal layer (stratum germinativum). The nuclear volume of keratinocytes was found to be approximately 1.4 times larger than that of resident LCs (88.6 microm3). Importantly, the ratio of LCs to keratinocytes in mouse ear skin (1:15) is more than three times higher than that reported for human breast skin (1:53). Accordingly, cross-presentation may be more significant in clinical Gene Gun applications than in pre-clinical mouse studies. These interspecies differences should be considered in pre-clinical trials using mouse models.

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.

Immunopathogenesis of oropharyngeal candidiasis in human immunodeficiency virus infection

Oropharyngeal and esophageal candidiases remain significant causes of morbidity in human immunodeficiency virus (HIV)-infected patients, despite the dramatic ability of antiretroviral therapy to reconstitute immunity. Notable advances have been achieved in understanding, at the molecular level, the relationships between the progression of HIV infection, the acquisition, maintenance, and clonality of oral candidal populations, and the emergence of antifungal resistance. However, the critical immunological defects which are responsible for the onset and maintenance of mucosal candidiasis in patients with HIV infection have not been elucidated. The devastating impact of HIV infection on mucosal Langerhans' cell and CD4(+) cell populations is most probably central to the pathogenesis of mucosal candidiasis in HIV-infected patients. However, these defects may be partly compensated by preserved host defense mechanisms (calprotectin, keratinocytes, CD8(+) T cells, and phagocytes) which, individually or together, may limit Candida albicans proliferation to the superficial mucosa. The availability of CD4C/HIV transgenic mice expressing HIV-1 in immune cells has provided the opportunity to devise a novel model of mucosal candidiasis that closely mimics the clinical and pathological features of candidal infection in human HIV infection. These transgenic mice allow, for the first time, a precise cause-and-effect analysis of the immunopathogenesis of mucosal candidiasis in HIV infection under controlled conditions in a small laboratory animal.

The AIDS-like disease of CD4C/human immunodeficiency virus transgenic mice is associated with accumulation of immature CD11bHi dendritic cells

CD4C/human immunodeficiency virus (HIV) transgenic mice develop an AIDS-like disease. We used this model to study the effects of HIV-1 on dendritic cells (DC). We found a progressive decrease in total DC numbers in the lymph nodes, with a significant accumulation of CD11b(Hi) DC. In the thymus, the recovery of transgenic CD8alpha(+) DC had a tendency to be lower. Spleen DC were augmented in the marginal zone. Transgenic DC showed a decreased capacity to present antigen in vitro, consistent with their reduced major histocompatibility complex class II expression and impaired maturation profile. The accumulation of immature DC may contribute to disease and may reflect an adaptive advantage for the virus by favoring its replication and preventing the generation of fully functional antiviral responses.

Tissue specific HPV expression and downregulation of local immune responses in condylomas from HIV seropositive individuals

OBJECTIVE

To study the effect of tissue specific human papillomavirus (HPV) expression and its effect on local immunity in condylomas from HIV positive individuals.

METHODS

Biopsy specimens of eight penile and eight perianal condylomas from HIV seropositive individuals were analysed. Expression of viral genes (HIV-tat and HPV E7 and L1) was determined by RT-PCR. The status of local immunity also was determined by RT-PCR by measuring CD4, CD8, CD16, CD1a, HLA-DR, and HLA-B7 mRNA levels in the tissues. Differentiation was determined by measuring involucrin, keratinocyte transglutaminase, as well as cytokeratins 10, 16, and 17. Proliferation markers such as PCNA and c-myc were also determined.

RESULTS

The transcription pattern of HPV in perianal condylomas, which preferentially expressed the early (E7) gene, was different from that of penile condylomas, which primarily expressed the late (L1) gene. This transcription pattern is in good correlation with the keratinisation and differentiation patterns of the two epithelia: perianal biopsies preferentially expressed K16 and K17 while penile warts mainly expressed K10, markers of parakeratotic and orthokeratotic epithelia, respectively. Perianal biopsies also showed a higher degree of proliferation (PCNA and c-myc). Interestingly, transcription of HIV-tat was also higher in perianal than in penile biopsies. A high degree of local immunodeficiency was observed in perianal biopsies--that is, levels of CD4, CD16, and CD1a mRNAs were significantly lower. A negative correlation between CD1a (Langerhans cells) levels and HPV E7 levels was established. HPV E7 levels positively correlated with HIV-tat levels. Perianal tissues demonstrated more CD1a depression and tat associated HPV upregulation.

CONCLUSION

HIV influences the expression of HPV genes resulting in local immunosuppression that might lead to an inappropriate immune surveillance of viral infection. Also, tissue type is an important factor in controlling viral transcription in a differentiation dependent manner. These findings may explain the higher rate of dysplasia and neoplasia in the perianal area.

Role of dendritic cells in immunopathogenesis of human immunodeficiency virus infection

The role of dendritic cells (DC) in the pathogenesis of human immunodeficiency virus (HIV) disease has been a subject of considerable interest for several years. Initial studies focused on the infection, dysfunction, and depletion of DC in HIV-infected individuals. More recent studies have begun to identify the functional role of DC in the initiation and propagation of viral replication in T cells in HIV-infected individuals. This review discusses recent data regarding the role of DC in HIV disease with the aim of delineating basic immunopathogenic principles of infection and the development of therapeutic strategies.

HIV-infected Langerhans cells constitute a significant proportion of the epidermal Langerhans cell population throughout the course of HIV disease

Human immunodeficiency virus (HIV) is known to infect Langerhans cells, but controversy still exists about the occurrence of HIV-infected Langerhans cells in the skin of HIV-infected individuals and about the density of epidermal Langerhans cells during the course of HIV disease. In this study, epidermal Langerhans cell population densities were analyzed quantitatively in serial biopsies from two burn patients acquired over an 11-y period following infection with HIV from transfusions received during their acute treatment. At each biopsy time point, the density of epidermal Langerhans cells and the proportion that were infected with HIV were analyzed by immunostaining. In both patients, skin grafts were slow to repopulate with Langerhans cells and did not attain normal Langerhans cell densities until about 2 y after grafting. Thereafter, Langerhans cell densities remained within normal limits with the exception of six biopsies at random times that showed a supernormal number of epidermal Langerhans cells. HIV-infected Langerhans cells were first detected at about 2 y post-infection and comprised about one-third of the Langerhans cell population. At subsequent times, HIV p24-stained Langerhans cells were identified in most biopsies and typically constituted about one third to one half of the total Langerhans cell population. The findings show that HIV-bearing Langerhans cells constitute a significant proportion of the epidermal Langerhans cell population over long periods of asymptomatic disease but are unevenly distributed throughout the skin. Normal population densities of epidermal Langerhans cells are maintained for years, although transient increases may occur randomly.

Replication of HIV-1 in dendritic cell-derived syncytia at the mucosal surface of the adenoid

Human immunodeficiency virus-type 1 (HIV-1) replicates actively in infected individuals, yet cells with intracellular depots of viral protein are observed only infrequently. Many cells expressing the HIV-1 Gag protein were detected at the surface of the nasopharyngeal tonsil or adenoid. This infected mucosal surface contained T cells and dendritic cells, two cell types that together support HIV-1 replication in culture. The infected cells were multinucleated syncytia and expressed the S100 and p55 dendritic cell markers. Eleven of the 13 specimens analyzed were from donors who did not have symptoms of acquired immunodeficiency syndrome (AIDS). The interaction of dendritic cells and T cells in mucosa may support HIV-1 replication, even in subclinical stages of infection.

Skin-associated lymphoid tissue in human immunodeficiency virus-1, human papillomavirus, and herpes simplex virus infections

The skin-associated lymphoid tissue is composed of keratinocytes, Langerhans cells, skin trophic T cells, and lymphatic endothelial cells of the skin. The epidermis, which is involved in many viral infections, contains all of the components needed for an effective immune response: antigen-presenting Langerhans cells, T cells, and cytokines from leukocytes and keratinocytes. There have been some recent advances in the study of the cutaneous immunology involved in infections with the human immunodeficiency virus (HIV), human papillomavirus (HPV), and herpes simplex virus (HSV). In general, viral diseases with cutaneous manifestations lead to a decline in epidermal Langerhans cell numbers, which probably reflects Langerhans cell emigration out of the epidermis and entry into regional lymph nodes, leading to Langerhans cell activation and antigen presentation to T cells. In HSV, there is a subsequent T-cell infiltration of the epidermis, composed of CD4+ cells that have both immune modulatory action and direct cytotoxic action. In HIV, where there is a systemic depletion of CD4+ cells, the epidermis is left with reduced numbers of T cells. Intradermal injection of interleukin-2, however, leads to an epidermal cellular infiltration in HIV+ individuals. In HPV-induced condyloma, intralesional interferon increases Langerhans cells and CD4+ and CD8+ cells in the skin, as well as transforming growth factor beta 1, tumor necrosis factor-alpha, pRB, and p53. Therefore, viral infections involving the epidermal immune system have certain similar characteristics, whereas other factors are unique to the infecting virus.

In vitro analysis of HIV- and non-HIV-infected monocytes/macrophages from healthy subjects and patients with malignant tumours

Phenotype and release of IL1 alpha, IL6 and TNF alpha were examined in monocytes derived from 14 healthy donors and 24 tumour patients in a long-term culture using immunohistochemical, RNA in situ hybridization and ELISA techniques. After stimulation with LPS and IFN-gamma, blood monocytes and resulting macrophages showed an overall decrease in cytokine release from the 6th to the 48th day of culture, both with and without HIV infection. HIV infection provided a strong stimulus for IL6 production and a weak stimulus for IL1 alpha production, whereas TNF alpha release decreased after HIV infection. Non-HIV-infected monocytes/macrophages from patients with malignancies showed significantly reduced cytokine production after stimulation, in comparison with monocytes/macrophages from healthy subjects. In vitro HIV infection of monocytes from tumour patients caused severe depression of cytokine production during the whole time of observation. In all experiments a parallel was observed between the extent of cytokine release and the presence of young/early inflammatory macrophages as identified by the antibody MAC387/27E10 in situ. In contrast, cytokine expression assessed semiquantitatively by immunohistochemical staining in situ showed discordant development, since it increased during long-term culture, while supernatant concentrations of cytokines declined. Simultaneously, significant cytokine RNA levels could be found in macrophages from the 6th to the 24th day of culture, as detected by in situ hybridization. After 48 days of culture, no more cytokine RNA was detectable, while macrophages continued to exhibit distinct immunohistochemical positivity for cytokine antibodies. From these results, it is concluded that macrophages kept in culture for a long period become inhibited in their secretion. HIV has an ambivalent effect on cytokine production in Mo/Mac, resulting in an increase in IL6 and IL1 as well as a decrease in TNF alpha production. Mo/Mac of non-HIV-infected tumour patients show significantly reduced cytokine production in comparison with Mo/Mac from healthy subjects. The sum of the HIV infection in vitro and the tumour burden results in a dramatic reduction in cytokine release in Mo/Mac. This finding may provide a possible explanation for the specific aggressive behaviour of non-Hodgkin's lymphoma and Hodgkin's disease in AIDS.