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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.

ABSTRACTThe Ahi-1locus was initially identified as a common helper provirus integration site in Abelson pre-B-cell lymphomas and shown to be closely linked to the c-mybproto-oncogene. Since no significant alteration of c-mybexpression was found in Abelson murine leukemia virus-induced pre-B-lymphomas harboring a provirus inserted within the Ahi-1locus, this suggested that it harbors another gene whose dysregulation is involved in tumor formation. Here we report the identification of a novel gene (Ahi-1) targeted by these provirus insertional mutations and the cloning of its cDNA. The Ahi-1 proviral insertions were found at the 3' end of the gene, in an inverse transcriptional orientation, with most of them located around and downstream of the last exon, whereas another insertion was within intron 22. In addition, another previously identified provirus insertion site, Mis-2, was found to map within the 16th intron of the Ahi-1gene. The Ahi-1cDNA encodes a 1,047-amino-acid protein. The predicted Ahi-1 protein is a modular protein that contains one SH3 motif and seven WD40 repeats. The Ahi-1gene is conserved in mammals and encodes two major RNA species of 5 and 4.2 kb and several other shorter splicing variants. The Ahi-1gene is expressed in mouse embryos and in several organs of the mouse and rat, notably at high levels in the brain and testes. In tumor cells harboring insertional mutations in Ahi-1, truncated Ahi-1/viral fused transcripts were identified, including some splicing variants with deletion of the SH3 domain. Therefore, Ahi-1is a novel gene targeted by provirus insertion and encoding a protein that exhibits several features of a signaling molecule. Thus, Ahi-1may play an important role in signal transduction in normal cells and may be involved in tumor development, possibly in cooperation with other oncogenes (such as v-abland c-myc) or with a tumor suppressor gene (Nf1), since Ahi-1 insertion sites were identified in tumors harboring v-abldefective retroviruses or a c-myctransgene or in tumors exhibiting deletion of Nf1.

ABSTRACTIn order to study the functions of simian immunodeficiency virus (SIV) Nef in vivo in a small-animal model, we constructed transgenic (Tg) mice expressing the SIVmac239 nefgene in the natural target cells of the virus under the control of the human CD4 gene promoter (CD4C). These CD4C/SHIV-nefSIVTg mice develop a severe AIDS-like disease, with manifestations including premature death, failure to thrive or weight loss, wasting, thymic atrophy, an especially low number of peripheral CD8+T cells as well as a low number of peripheral CD4+T cells, diarrhea, splenomegaly, and kidney (interstitial nephritis, segmental glomerulosclerosis), lung (lymphocytic interstitial pneumonitis), and heart disease. In addition, these Tg mice fail to mount a class-switched antibody response after immunization with ovalbumin, they produce anti-DNA autoantibodies, and some of them develop Pneumocystis cariniilung infections. All these results suggest a generalized Nef-induced immunodeficiency. The low numbers of peripheral CD8+and CD4+T cells are likely to reflect a thymic defect and may be similar to the DiGeorge-like “thymic defect” immunophenotype described for a subgroup of human immunodeficiency virus type 1-infected children. Therefore, it appears that SIV Nef alone expressed in mice, in appropriate cell types and at sufficient levels, can elicit many of the phenotypes of simian and human AIDS. These Tg mice should be instrumental in studying the pathogenesis of SIV Nef-induced phenotypes.