An erythematous maculopapular eruption in macaques infected with an HTLV-III-like virus (STLV-III)

Investigations on four host response factors whose expression is enhanced in X4 SHIV encephalitis

HIV encephalopathy, one of the major complications of HIV infection, involves productive virus replication in macrophages in the brain in association with heightened expression of several host response factors. One or more of these factors are thought to be the cause of the degenerative changes in neurons in the brain. Macaques infected with SIV and SHIV viruses have provided excellent working models for studying mechanisms of the human disease. Although HIV encephalopathy is primarily associated with CCR5-utilizing viruses, our findings have shown that CXCR4-utilizing SHIVs were also capable of causing the syndrome in rhesus macaques. In SHIV-infected macaques, approximately 30% of the animals developed encephalitis. In order to understand the factors leading to end-stage encephalitis, we performed microarray analyses on brains of encephalitic and non-encephalitic-infected macaques, and found pronounced enhancement of expression of interleukin-4, platelet-derived growth factor-B chain, monocyte chemoattractant protein-1 and CXCL10 in the brains of the encephalitic animals. This review discusses the role of each of these factors in mediating SHIV encephalitis.

Role of interleukin-4 and monocyte chemoattractant protein-1 in the neuropathogenesis of X4 simian human immunodeficiency virus infection in macaques

Recent studies on the coreceptor usage of human immunodeficiency virus (HIV) strains associated with acquired immunodeficiency syndrome (AIDS) dementia have shown that both X4 and R5 viruses are involved in the process. The disease is associated with enhanced virus replication and monocyte chemoattractant protein (MCP)-1 production in macrophages in the brain. Using the macaque model of the disease, the authors show here that X4, macrophage-tropic simian human immunodeficiency virus (SHIV) required the enhancing effect of interleukin (IL)-4 to achieve equivalent concentrations of virus and MCP-1 that are produced in macrophages infected with R5 viruses alone. Confocal microscopy showed that macrophages in the encephalitic brains were the major producers of MCP-1. The authors surmise, therefore, that whereas R5 viruses maybe capable of causing the disease as a primary pathogen, X4 viruses may require IL-4, induced by opportunistic pathogens, for induction of the neuropathological syndrome.

Microarray analysis of cytokine and chemokine genes in the brains of macaques with SHIV-encephalitis

Human immunodeficiency virus (HIV)-encephalitis results from a cascade of viral-host interactions that lead to cytokine and chemokine imbalance, which then leads to neuropathologic manifestations of the disease. These include macrophage/microglia activation, astrocytosis and neuronal dysfunction or death. As the molecular mechanisms of this process are poorly understood, we used Atlas human cytokine or cytokine receptor microarray analysis to highlight gene expression profiles that accompanied encephalitis in Simian human immunodeficiency virus (SHIV) 89.6P-infected macaques. Of the 277 genes screened, marked upregulation of monocyte chemoattractant protein-1, interferon-inducible peptide IP-10 and interleukin-4 were observed specifically in the encephalitic brains. These genes are collectively known to promote macrophage infiltration and activation and virus replication. In contrast, genes regulating neurotrophic functions, such as brain-derived neurotrophic factor were downregulated. We also found that some of the apoptosis genes were up- or down-regulated. These data provide a comprehensive spectrum of gene expression that underscores the two major clinical manifestations of this unique syndrome: enhanced virus replication in brain macrophages and dystrophic changes in neurons.

Characterization of the cutaneous exanthem in macaques infected with a Nef gene variant of SIVmac239

The molecularly cloned viruses known as SIVmac239/R17Y and SIVmac239/YEnef cause extensive lymphocyte activation and induce an acute disease syndrome in macaque monkeys. One manifestation of this syndrome is a severe diffuse cutaneous maculopapular exanthem that is similar to the exanthem associated with HIV-1 infection. To examine the pathogenesis of this exanthem, biopsies obtained throughout the course of clinically evident rash were examined for the presence of virus by in situ hybridization and immunohistochemistry, and the cellular infiltrate was characterized with respect to cellular immunophenotype and chemokine receptor expression. The onset of rash was associated with abundant simian immunodeficiency virus nucleic acid and protein within perivascular dermal infiltrates and occasionally within intraepithelial cells. Analysis of cellular infiltrates showed that biopsies, obtained on the day of rash onset, were composed of equal numbers of CD4+ and CD8+ lymphocytes and abundant alphaEbeta7 positive cells surrounding vessels with upregulated endothelial E-selectin. Moreover, by examining virus expression in sequential skin biopsies from the same animal, the clearance of virus and the resolution of rash were associated with an increase in the percentage of cells expressing CD8, the chemokine receptor CXCR3, and GMP-17, a marker of cytotoxic granules. These results suggest that activated cytotoxic T cells are trafficking to sites of inflammation in the skin and directly or indirectly affect levels of viral replication at these sites.

[Symptomatic primary human immunodeficiency virus infection]

Symptomatic primary human immunodeficiency virus (HIV) infection was originally defined as a mononucleosis-like syndrome, with or without lymphocytic meningitis, associated with seroconversion for HIV. However, other protean clinical manifestations have been reported, and diagnosis should be considered in patients with risk factors for HIV who experience acute infectious illness, requiring search for p24 antigenemia and development of HIV antibodies. The clinical presentation of symptomatic HIV infection could predict the subsequent disease progression. In several studies, it is associated with poor prognosis. Pathogenesis relies on the host immune response and on virologic parameters. Early antiretroviral therapy on acute HIV infection could modify the course of infection.

Reduced number of Langerhans cells in oral mucosal washings from HIV-1 seropositives

In order to elucidate mucosal immunity in HIV-1 seropositive individuals, we investigated oral mucosa washings from 20 HIV-1 seropositive patients for the presence of Langerhans cells (LC) and HIV-1 antigen-positive cells, and compared the results with those obtained from 20 HIV-1 seronegative healthy individuals. Monoclonal antibodies directed against CD1a, HLA-DR, CD3, and p24 were used to identify LC, T cells and HIV-1 core-antigens, respectively. In oral mucosa washings from HIV-1 seropositive patients there was a significant reduction in the number of CD1a+ cells as compared with the healthy subjects. HIV-1 antigen-positive cells were not detected. The reduction of LC in oral mucosa washings from HIV-1 seropositive patients is probably associated with HIV-1 infection. The frequent occurrence of oral mucosal disorders in HIV-1 infected patients may in part be caused by a reduced LC-number and/or function.

Pathologic features of SIV-induced disease and the association of macrophage infection with disease evolution

Since the original isolation of simian immunodeficiency virus (SIV) from a macaque with an AIDS-like disease, numerous studies have demonstrated the close biologic and genetic relationship of the SIVs to the HIVs. Probably most important, the clinical spectrum of disease associated with SIVmac/SIVsmm infection in rhesus monkeys is strikingly similar to AIDS in HIV-1-infected human beings. Herein are summarized the pathologic features of SIVmac-induced disease in a cohort of rhesus monkeys, with special reference to the role of infected macrophages in the development of AIDS-related manifestations.

Simian immunodeficiency virus inhibits bone marrow hematopoietic progenitor cell growth

The pathogenic mechanisms underlying the depressed hematopoietic functions seen in human immunodeficiency virus-infected individuals were explored in rhesus monkeys infected with the simian immunodeficiency virus of macaques (SIVmac). Bone marrow hematopoietic progenitor cell colony formation, both granulocyte/macrophage (CFU-GM) and erythrocyte (BFU-E), was shown to be decreased in number in SIVmac-infected rhesus monkeys. SIVmac was readily isolated from bone marrow cells of infected monkeys and was shown to be harbored in macrophages rather than T lymphocytes. The in vitro infection of normal bone marrow cells by SIVmac inhibited colony formation. A striking in vivo correlation between increased SIVmac load in bone marrow cells and decreased hematopoietic progenitor cell colony growth was also shown. Finally, inhibition of SIVmac replication in bone marrow macrophages resulted in increased progenitor cell colony growth from bone marrow cells. These results suggest that the infection of bone marrow macrophages by the acquired immunodeficiency syndrome (AIDS) virus may contribute to depressed bone marrow hematopoietic progenitor cell growth. Moreover, inhibition of AIDS virus replication in these macrophages might induce significant improvement in hematopoietic function.

Necropsy findings in rhesus monkeys experimentally infected with cultured simian immunodeficiency virus (SIV)/delta

Lesions induced in rhesus monkeys by different isolates of simian immunodeficiency virus (SIV)/Delta were studied at necropsy. Four groups of monkeys were inoculated with SIV/Delta isolated from other experimentally infected rhesus monkeys, while one group was inoculated with SIV/Delta from an asymptomatic mangabey monkey. Three rhesus isolates and the mangabey isolate were virulent, killing 75-100% of infected monkeys. One rhesus isolate, which had been extensively passaged in vitro, was attenuated but was restored to virulence by single animal passage. Clinically, infected monkeys had lymphadenopathy, splenomegaly, diarrhea, and a rash. Most monkeys died of enteric disease. The following lesions were seen: weight loss, thymic atrophy, lymphoid atrophy, bone marrow hyperplasia, encephalitis, colitis, amyloidosis, hepatitis, glomerulosclerosis, and the presence of syncytial cells. One Rh Epstein-Barr virus (EBV)-related lymphoma occurred. Opportunistic agents were identified: cytomegalovirus, adenovirus, Cryptosporidia, and Pneumocystis. Shigella and Campylobacter often caused colitis.

Simian immunodeficiency virus-induced meningoencephalitis: natural history and retrospective study

Simian immunodeficiency virus (SIV) is a lentivirus with morphological and antigenic similarities to human immunodeficiency virus, the causative agent of acquired immunodeficiency syndrome (AIDS) of humans. Macaque monkeys infected with SIV show profound immunological impairment, clinically characterized by multiple opportunistic infections and neoplasms. Retrospective examination of autopsy tissue from 27 SIV-infected animals demonstrated that approximately 60% of the experimentally inoculated animals had a meningoencephalitis characterized by perivascular infiltrates of macrophages and multinucleate giant cells in the white and gray matter and leptomeninges. Ultrastructurally, these macrophages contained typical lentiviral particles within membrane-bound intracytoplasmic vacuoles. Other findings in the central nervous system included discrete randomly located neuroglial nodules, endothelial hypertrophy, and leptomeningeal thickening. The results indicate tha the meningoencephalitis induced by SIV in monkeys is similar to the lesions of the central nervous system in patients with AIDS and that SIV infection in the macaque is a useful animal model to study the pathogenesis of human immunodeficiency virus--related subacute encephalitis or AIDS encephalopathy.