318 Journal of Leukocyte Biology Volume 56, September 1994 HIV infection of monocyte-derived macrophages in vitro reduces phagocytosis of Candida albicans Suzanne M. Crowe Nicholas J. Vardaxis,t Stephen J. Kent Anne L. Maerz7 Marilyn J. Hewish Michael S. McGrath,t and John Mills* *National Centre for HIV Virology Research/AIDS Pathogenesis Research Unit, Macfarlane Burnet Centrefor Medical Research, Fairfield, Melbourne, Australia, Department of Medical Laboratory Science, Royal Melbourne Institute of Technology, Bundoora Campus, Melbourne, Australia, and AIDS Immunobiology Unit, San Francisco General Hospital, University of California, San Francisco Abstract: HIV-1 infection of peripheral blood monocyte- derived macrophages (MDMs) is unrelated to the level of CD4 expression on the surface of the cell, is associated with considerable donor variability, causes minimal cytopathology, and results in peak viral antigen produc- tion after 2 weeks of infection. Phagocytosis of opsonized Candida albicans by MDMs infected in vitro with several strains of HIV was compared with that of uninfected cells from the same donors; the proportion of MDMs contain- ing the fluorescein isothiocyanate - labeled yeast was de- termined by flow cytometry and phase contrast microscopy. The intracellular localization of C. albicans was confirmed by confocal microscopy. Using paired MDMs from nine donors, 81% ofuninfected and 53% of HIV-infected MDMs phagocytosed C. albicans. In addi- tion, the number of yeast per cell was significantly higher in uninfected MDMs than in HIV-infected cells (mean 6.1 versus 2.5). These findings may partially explain the high incidence of mucocutaneous candidiasis in HIV- infected patients with advanced disease. J. Leukoc. Biol. 56: 318-327; 1994. Key Words: macrophage function . opsonization complement receptor . flow cytometry . lipopolysaccharide INTRODUCTION Macrophages provide numerous critical functions within the immune system, including chemotaxis, phagocytosis, anti- gen presentation, cytokine production, and tumor surveil- lance [1]. Productive infection of these cells with the human immunodeficiency virus (HIV) can be induced in vitro, and HIV has been identified within tissue macrophages and peripheral blood monocytes from HIV-infected individuals [2-16]. As monocytotropic HIV isolates are present through- out HIV infection, cells of the macrophage lineage are im- portant contributors to the viral reservoir in vivo [17]. Fur- thermore, alterations in macrophage function during the course of HIV infection have been reported and undoubt- edly contribute to the characteristic immune deficiency as- sociated with HIV infection. The proportion of monocyte-derived macrophages (MDMs) that can be infected in an in vitro culture system differs between reported studies, varying with multiplicity of infection, HIV strain, culture technique (adherence to glass or plastic or suspension), age of cultured cells at the time of infection, addition of cytokines or growth factors, and method of detection 12, 5, 9, 12, 15]. Quantification of in- fected MDMs by immunofluorescence may be complicated by innate properties of this cell population such as autofluorescence [18-20] and stickiness due to presence of Fe receptors [21-24]. More important, the proportion of mono- cytes and macrophages infected in vivo and the characteris- tics of that infection (latent versus productive, cytopathic versus noncytopathic) remain uncertain. It is likely that the level of infection varies depending on the tissue compart- ment studied (e.g., brain and lung are reported to harbor a higher proportion of infected macrophages than that found in peripheral blood monocytes [8, 14, 25-27]), as well as stage of disease and predominant HIV strain within the quasispecies [28]. The opportunistic infections associated with advanced HIV infection are generally controlled by host defenses that are complex and involve both humoral and cellular immune responses. Although the exact contribution of these mechan- isms varies from pathogen to pathogen, the importance of in- gestion and killing by macrophages in controlling many of these organisms is supported by both clinical and experimen- tal data. Some of these pathogens that reactivate and cause opportunistic infection in the course of HIV infection, in- eluding cryptococcal meningitis, cerebral toxoplasmosis, and disseminated infections due to Mycobacterium tuberculosis and disseminated Mycobacterium avium complex infection [29-32], strongly suggest underlying macrophage dysfunction. Mucocutaneous candidiasis, due to infection with the di- morphic yeast Candida albicans, is common in HIV-infected persons with waning immune function [33, 34] and is representative of most HIV-related opportunistic infections in terms of its complex host defense and involvement of mac- rophage function. Neutrophils, macrophages, and CD4 T lymphocytes as well as antibody and complement are re- quired for optimal control of this yeast (reviewed in refs. 35-39). This study identifies a defect in the phagocytic function of MDMs that were infected with HIV in vitro. By flow cyto- metric analysis, confocal microscopy, and phase contrast fluorescence microscopy we have found that HIV-infected macrophages are less efficient in ingesting C. albicans than uninfected cells from the same donors. These data may pro- vide a partial explanation for the high prevalence of mucocutaneous candidiasis in persons with advanced HIV infection. Abbreviations: BAM , bronchoalveolar issacrophage; FITC, fluorescein isothiocyanate; HIV, human immunodeficiency virus; LPS, lipopolysaccha- ride; MDM, monocyte-derived macrophage; PBMC, peripheral blood mononuclear cell; PBS, phosphate-buffered saline. Reprint requests: Suzanne Crowe, AIDS Pathogenesis Research Unit, Macfarlane Burnet Centre, Yarra Bend Rd., Fairfield 3078, Victoria, Aus- tralia. Received April 1, 1994; accepted May 11, 1994.