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ABSTRACTCryptococcus neoformansvar. grubiiis the most frequent cause of AIDS-associated cryptococcosis worldwide, while Cryptococcus gattiiusually infects immunocompetent people. To understand the mechanisms which cause differential susceptibility to these cryptococcal species in HIV infection, we established and characterized a model of cryptococcosis in CD4C/HIVMutAtransgenic (Tg) mice expressing gene products of HIV-1 and developing an AIDS-like disease. Tg mice infected intranasally with C. neoformansvar. grubiistrain H99 or C23 consistently displayed reduced survival compared to non-Tg mice at three graded inocula, while shortened survival of Tg mice infected with C. gattiistrain R265 or R272 was restricted to a single high inoculum. HIV-1 transgene expression selectively augmented systemic dissemination to the liver and spleen for strains H99 and C23 but not strains R265 and R272. Histopathologic examination of lungs of Tg mice revealed large numbers of widely scattered H99 cells, with a minimal inflammatory cell response, while in the non-Tg mice H99 was almost completely embedded within extensive mixed inflammatory cell infiltrates. In contrast to H99, R265 was dispersed throughout the lung parenchyma and failed to induce a strong inflammatory response in both Tg and non-Tg mice. HIV-1 transgene expression reduced pulmonary production of CCL2 and CCL5 after infection with H99 or R265, and production of these two chemokines was lower after infection with R265. These results indicate that an altered immune response in these Tg mice markedly enhances C. neoformansbut not C. gattiiinfection. This model therefore provides a powerful new tool to further investigate the immunopathogenesis of cryptococcosis.

ABSTRACTThe critical impairments of innate and adaptive immunity that cause susceptibility to mucosal candidiasis in human immunodeficiency virus (HIV) infection have not been fully determined. We therefore conducted an analysis of macrophage-mediated responses to Candida albicansin transgenic (Tg) mice expressing Nef, Env, and Rev of HIV type 1 (HIV-1) in CD4+T cells, dendritic cells, and macrophages and developing an AIDS-like disease (CD4C/HIVMutATg mice). Macrophages were successfully recruited to the oral and gastric mucosae of these Tg mice in response to chronic carriage of C. albicansand displayed polarization toward an alternatively activated phenotype. Functionally, peritoneal macrophages from uninfected Tg mice exhibited increased phagocytosis of C. albicansand enhanced production of interleukin 6 and monocyte chemoattractant protein 1, demonstrating that the HIV-1 transgene independently activates selected macrophage functions. Production of H2O2by macrophages from Tg mice primed with gamma interferon and treated with phorbol 12-myristate 13-acetate or C. albicanswas moderately reduced, but expression of the HIV-1 transgene did not alter production of nitric oxide or reduce killing of C. albicans. A knockout of the inducible nitric oxide synthase (NOS2) gene in these Tg mice did not augment oral or gastrointestinal burdens during chronic carriage of C. albicansor cause systemic dissemination, likely due to a redundancy provided by partially preserved production of H2O2and oxygen-independent candidacidal mechanisms. Thus, the macrophage response to C. albicansis largely preserved in these Tg mice, and no functional macrophage defect appears to primarily determine the susceptibility to mucosal candidiasis.

Candida albicans causes oropharyngeal candidiasis (OPC) but rarely disseminates to deep organs in human immunodeficiency virus (HIV) infection. Here, we used a model of OPC in CD4C/HIVMut transgenic (Tg) mice to investigate the role of polymorphonuclear leukocytes (PMNs) and CD8+ T cells in limiting candidiasis to the mucosa. Numbers of circulating PMNs and their oxidative burst were both augmented in CD4C/HIVMutA Tg mice expressing rev, env, and nef of HIV type 1 (HIV-1), while phagocytosis and killing of C. albicans were largely unimpaired compared to those in non-Tg mice. Depletion of PMNs in these Tg mice did not alter oral or gastrointestinal burdens of C. albicans or cause systemic dissemination. However, oral burdens of C. albicans were increased in CD4C/HIVMutG Tg mice expressing only the nef gene of HIV-1 and bred on a CD8 gene-deficient background (CD8–/–), compared to control or heterozygous CD8+/– CD4C/HIVMutG Tg mice. Thus, CD8+ T cells contribute to the host defense against oral candidiasis in vivo, specifically in the context of nef expression in a subset of immune cells.

ABSTRACTCandida albicanscauses oropharyngeal candidiasis (OPC) but rarely disseminates to deep organs in human immunodeficiency virus (HIV) infection. Here, we used a model of OPC in CD4C/HIVMuttransgenic (Tg) mice to investigate the role of polymorphonuclear leukocytes (PMNs) and CD8+T cells in limiting candidiasis to the mucosa. Numbers of circulating PMNs and their oxidative burst were both augmented in CD4C/HIVMutATg mice expressing rev, env, and nefof HIV type 1 (HIV-1), while phagocytosis and killing of C. albicanswere largely unimpaired compared to those in non-Tg mice. Depletion of PMNs in these Tg mice did not alter oral or gastrointestinal burdens of C. albicansor cause systemic dissemination. However, oral burdens of C. albicanswere increased in CD4C/HIVMutGTg mice expressing only the nefgene of HIV-1 and bred on a CD8 gene-deficient background (CD8−/−), compared to control or heterozygous CD8+/−CD4C/HIVMutGTg mice. Thus, CD8+T cells contribute to the host defense against oral candidiasis in vivo, specifically in the context of nefexpression in a subset of immune cells.

ABSTRACTIn order to approximate and adhere to mucosal epithelial cells,Candidamust traverse the overlying mucus layer. Interactions of Candidaspecies with mucin and human buccal epithelial cells (BECs) were thus investigated in vitro. Binding of the Candidaspecies to purified small intestinal mucin showed a close correlation with their hierarchy of virulence. Significant differences (P< 0.05) were found among three categories of Candidaspecies adhering highly (C. dubliniensis, C. tropicalis, and C. albicans), moderately (C. parapsilosisand C. lusitaniae) or weakly (C. kruseiand C. glabrata) to mucin. Adherence of C. albicansto BECs was quantitatively inhibited by graded concentrations of mucin. However, inhibition of adherence was reversed by pretreatment of mucin with pronase or C. albicanssecretory aspartyl proteinase Sap2p but not with sodium periodate. Saturable concentration- and time-dependent binding of mucin to C. albicanswas abrogated by pronase or Sap2p treatment of mucin but was unaffected by β-mercaptoethanol, sodium periodate, neuraminidase, lectins, or potentially inhibitory sugars. Probing of membrane blots of the mucin with C. albicansrevealed binding of the yeast to the 66-kDa cleavage product of the 118-kDa C-terminal glycopeptide of mucin. Although no evidence was found for the participation of C. albicanscell surface mannoproteins in specific receptor-ligand binding to mucin, inhibition of binding by p-nitrophenol (1 mM) and tetramethylurea (0.36 M) revealed that hydrophobic interactions are involved in adherence of C. albicansto mucin. These results suggest that C. albicansmay both adhere to and enzymatically degrade mucins by the action of Saps, and that both properties may act to modulate Candidapopulations in the oral cavity and gastrointestinal tract.