Cellular immune response to Mycobacterium leprae infection in human immunodeficiency virus-infected individuals

Abstract

The immune responses to Mycobacterium leprae and other mycobacterial antigens were studied in 11 leprosy patients with concurrent human immunodeficiency virus type 1 (HIV-1) infection. Three patients manifested borderline lepromatous leprosy, and eight patients had borderline tuberculoid (BT) leprosy. Despite the low CD4 ؉ T-cell count in the peripheral blood, no histologic or phenotypic change in the cellular infiltrate in either the lepromatous or tuberculoid lesions was observed when compared with HIV-1-negative patients. Lepromatous lesions contained heavily parasitized macrophages and few CD8 ؉ T cells. Lesions from the patients with BT leprosy showed extensive CD4 ؉ T-cell infiltration despite a significant reduction in CD4 ؉ T-cell counts in the peripheral blood. No acid-fast bacilli were detected in the tuberculoid lesions. HIV-1 infection did not alter the lack of response in lepromatous leprosy to M. leprae antigens either in vitro or in vivo. In contrast, the skin test response to M. leprae antigens as well as the in vitro lymphoproliferative responses to mycobacterial antigens that are usually seen in patients with tuberculoid leprosy were abrogated in the BT HIV-1 ؉ patients. However, production of gamma interferon in response to the same stimuli was preserved in most of the patients. Analysis of cytokine gene expression showed activation of additional cytokine genes in the unstimulated peripheral blood cells of patients with both leprosy and HIV-1 infections as compared with cells from patients with leprosy alone. These results suggest that granuloma formation in leprosy can be independent of the impaired CD4 ؉ T-cell response of the HIV-1 infection. Furthermore, in HIV-1 ؉ individuals with M. leprae infection, activation of cytokine genes is observed even when the circulating CD4 ؉ T-cell count is significantly reduced.

Immunophenotype of skin lymphocytic infiltrate in patients co-infected with Mycobacterium leprae and human immunodeficiency virus: a scenario dependent on CD8+ and/or CD20+ cells

“…The number of positive cells in the dermis of the samples was determined manually and expressed as a rough percentage in proportion to the total lymphocytic infiltrate. The discrepancy between the literature and our data may be explained if one considers that previous studies were conducted on smaller series of patients than ours, 1–11,16–20 and that the same markers were not investigated (as they became available only recently).…”

Bacterial Infections

“…A number of studies conducted in several tropical countries failed to demonstrate any relationship between the incidence of HIV infection and that of leprosy (30, 44, 57). A few case reports have stressed the appearance of borderline tuberculoid leprosy in conjunction with AIDS in Western countries (52); however, a comparative study of the immune responses to M. Zeprue in 11 leprosy patients with AIDS and low CD4 count, did not show any histologic or phenotypic change in the cellular infiltrate in either the lepromatous or the tuberculoid lesions when compared with HIV-negative patients (96).…”

Immune cellular parameters of leprosy and human immunodeficiency virus‐1 co‐infected subjects

“…10 Paradoxically, the most detailed description of leprosy immunopathology in HIV-1 co-infected patients revealed no change in immune cell infiltrates across the leprosy spectrum, despite advanced HIV-1-associated immune deficiency. 7,11 On the other hand, there has been little or no attempt to evaluate the impact of M. leprae infection on HIV-1 pathogenesis. This interaction has been studied in the macaque/simian immunodeficiency virus (SIV) model, however, where M. leprae infection was observed to exert an unexpected and unexplained ameliorating effect on SIV disease, prolonging survival of the animals, despite equal or increased viral burdens.…”