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Haemophilus ducreyi is a major cause of genital ulcer disease in many developing countries and is associated with augmented transmission of human immunodeficiency virus (HIV). However, the mechanisms through which H. ducreyi produces ulceration are poorly understood. The characteristics of the host response to H. ducreyi and the pathobiology of its potential contribution to increased HIV susceptibility are not known. Chancroid ulcer biopsies from 8 patients were analyzed histologically and immunohistochemically. All biopsies had perivascular and interstitial mononuclear cell infiltrates that extended deep into the dermis. The infiltrate, which contained macrophages and CD4 and CD8 lymphocytes, was consistent with a delayed hypersensitivity type cell-mediated immune response. The recruitment of CD4 T lymphocytes and macrophages may in part explain the facilitation of HIV transmission in patients with chancroid.

Vitamin A deficiency was not associated with an increased risk of HIV-1 infection among men with concurrent STD. A decreased risk of HIV-1 seroconversion was independently associated with lower retinol levels. The effects of vitamin A on macrophage and lymphoid cell differentiation may paradoxically increase mucosal susceptibility to HIV-1 in some vulnerable individuals, such as men with genital ulcers. Lack of circumcision and chancroid are confirmed as important co-factors for heterosexual HIV-1 transmission. The role of vitamin A in heterosexual HIV-1 transmission requires further study.

In previous studies, genital ulcers in men have been found to be associated with increased risk of HIV-1 seroconversion. To further explore this association male patients attending a sexually transmitted disease (STD) clinic in Nairobi for either urethritis (controls, n = 276) or a genital ulcer (cases, n = 607) were compared with respect to sexual behaviour, presence of HIV-1 antibody and circumcision status. Patients were followed to study risk factors for incident genital ulcers and HIV-1 seroconversion. At entry, being married was associated with higher prevalence of HIV-1 (OR = 1.76) and genital ulcers (OR = 1.42). Lack of circumcision was associated with both HIV-1 infection (OR = 4.67) and the presence of a genital ulcer (OR = 2.23). Genital ulcers were also associated with HIV-1 infection (OR = 1.87) independent of circumcision status. On follow-up, HIV-1 seropositivity was associated with incident genital ulcers. It is argued that the association between genital ulcers and HIV-1 infection may be more complex than ulcers simply being a risk factor for HIV-1 infection, and that HIV-1 infection may either increase the risk of acquiring a genital ulcer, or HIV-1 infection and genital ulcers may have some unknown risk factor in common.

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