HIV insertions within and proximal to host cell genes are a common finding in tissues containing high levels of HIV DNA and macrophage-associated p24 antigen expression.

HIV integration within host cell genomic DNA is a requisite step of the viral infection cycle. Yet, characteristics of the sites of provirus integration within the host genome remain obscure. The authors present evidence that in diseased tissues showing a high level of HIV DNA and macrophage-associated HIV p24 antigen expression from end stage forms of HIV disease, HIV-1 integration sites were favored within genes and transcriptionally active host cell genomic loci. Using an inverse PCR (IPCR) technique that identified dominant integrated forms of HIV, clonal IPCR products were isolated from AIDS dementia, AIDS lymphoma, and angioimmunoblastic lymphadenopathy tissues. Thirty of 34 disease-associated HIV-1 insertions were identified within annotated and hypothetical genes, an unexpected but highly nonrandom genetic coding region association (p <.026). The 1% sensitivity thresholds used for HIV IPCR suggested some form of selective expansion of cells containing these HIV proviruses. Consistent with this interpretation were the HIV-1 insertion sites identified within introns of genes that encoded for factors associated with signal transduction, apoptosis, and transcription regulation. In addition, HIV-1 proviruses were frequently found proximal to genes that encoded for receptor-associated, signal transduction-associated, transcription-associated, and translation-associated proteins. HIV-1 integration within host cell genomic DNA potentially represents a significant insertional mutagenic event. In certain cases, provirus insertions may mediate the dysregulation of specific gene expression events, providing mechanisms contributing to the pathogenesis associated with certain AIDS-related diseases.

Coinfection of SCID-hu Thy/Liv mice with human herpesvirus 6 and human immunodeficiency virus type 1.

Human herpesvirus 6 (HHV-6) has been proposed as a potential cofactor in the progression of human immunodeficiency virus type 1 (HIV-1) disease. We used the SCID-hu Thy/Liv mouse model to evaluate the in vivo interactions between HHV-6 and HIV-1. Our results demonstrate that HHV-6 and HIV-1 can simultaneously replicate in the human thymus in vivo. In this model, however, the presence of one virus appears not to modify the replication or cytopathicity of the other.

Human immunodeficiency virus type 1 coreceptor preferences determine target T-cell depletion and cellular tropism in human lymphoid tissue.

The present study sought to determine how usage of coreceptors by human immunodeficiency virus type 1 dictates cell tropism and depletion of CD4(+) T cells in human lymphoid tissues cultured ex vivo. We found that coreceptor preferences control the marked, preferential depletion of coreceptor-expressing CD4(+) lymphocytes. In addition, there was a strong, but not absolute, preference shown by CXCR4-using strains for lymphocytes and by CCR5-using strains for macrophages.

Human herpesvirus 6 (HHV-6) causes severe thymocyte depletion in SCID-hu Thy/Liv mice.

Human herpesvirus 6 (HHV-6) is a potentially immunosuppressive agent that may act as a cofactor in the progression of AIDS. Here, we describe the first small animal model of HHV-6 infection. HHV-6 subgroup A, strain GS, efficiently infected the human thymic tissue implanted in SCID-hu Thy/Liv mice, leading to the destruction of the graft. Viral DNA was detected in Thy/Liv implants by quantitative polymerase chain reaction (PCR) as early as 4 d after inoculation and peaked at day 14. The productive nature of the infection was confirmed by electron microscopy and immunohistochemical staining. Atypical thymocytes with prominent nuclear inclusions were detected by histopathology. HHV-6 replication was associated with severe, progressive thymocyte depletion involving all major cellular subsets. However, intrathymic T progenitor cells (ITTPs) appeared to be more severely depleted than the other subpopulations, and a preferred tropism of HHV-6 for ITTPs was demonstrated by quantitative PCR on purified thymocyte subsets. These findings suggest that thymocyte depletion by HHV-6 may be due to infection and destruction of these immature T cell precursors. Similar results were obtained with strain PL-1, a primary isolate belonging to subgroup B. The severity of the lesions observed in this animal model underscores the possibility that HHV-6 may indeed be immunosuppressive in humans.

Characterization of a human Kaposi's sarcoma cell line that induces angiogenic tumors in animals.

OBJECTIVE: To characterize a Kaposi's sarcoma (KS) cell line established from a tumor biopsy from the oral mucosa of an iatrogenically immunosuppressed HIV-negative man. METHODS: Cells were placed in culture and evaluated by a variety of biologic, serologic, karyotypic, and immunologic procedures. Electron microscopic examination was performed. The ability to produce tumors in nude mice was evaluated, and the nature of the cells within the tumor determined. Assays for urokinase plasminogen activator type (uPA), plasminogen activator inhibitor-1 (PAI-1) and the urokinase receptor (uPAR) were conducted. RESULTS: The SLK cell line has an endothelial cell morphology with very little anaplasia. The karyotype indicates diploid phenotype of human origin. Immunohistochemical and electron microscopic examinations confirmed the endothelial nature of this cell line. No viruses were detected. The tumors induced in nude mice showed hypervascularization, with characteristics of KS. The cell line produces uPA and PAI-1, and also expresses uPAR. CONCLUSIONS: The SLK cell line is of endothelial cell origin and the first human cell line to induce KS-like tumors in recipient animals. The expression of urokinase and its receptor suggests a paracrine and autocrine interaction that may be important for the growth of the tumor. The SLK line should be valuable for studies of KS pathogenesis and therapeutic approaches to this malignancy.