Kaposi's sarcoma-associated herpesvirus G protein-coupled receptor signals through multiple pathways in endothelial cells.

Kaposi's sarcoma-associated herpesvirus (KSHV; human herpesvirus 8) encodes a chemokine-like G protein-coupled receptor (KSHV-GPCR) that is implicated in the pathogenesis of Kaposi's sarcoma (KS). Since endothelial cells appear to be targets for the virus, we developed an in vitro mouse lung endothelial cell model in which KSHV-GPCR is stably expressed and KSHV-GPCR signaling was studied. In mouse lung endothelial cells: 1) KSHV-GPCR does not exhibit basal signaling through the phosphoinositide-specific phospholipase C pathway but inositol phosphate production is stimulated by growth-related oncogene alpha (Gro-alpha) via a pertussis toxin (PTX)-insensitive pathway; 2) KSHV-GPCR signals basally through a PTX-sensitive pathway leading to a lowering of intracellular cAMP level that can be lowered further by Gro alpha and increased by interferon gamma-inducible protein 10; 3) KSHV-GPCR stimulates phosphatidylinositol 3-kinase via a PTX-insensitive mechanism; and 4) KSHV-GPCR activates nuclear factor-kappa B (NF-kappa B) by a PTX-sensitive G beta gamma subunit-mediated pathway. These data show that KSHV-GPCR couples to at least two G proteins and initiates signaling via at least three cascades in endothelial cells thereby increasing the complexity of regulation of endothelial cell function by KSHV-GPCR that may occur during viral infection.

Integrons: an antibiotic resistance gene capture and expression system.

Bacteria can transfer genetic information to provide themselves with protection against most antibiotics. The acquisition of resistance gene arrays involves genetic mobile elements like plasmids and transposons. Another class of genetic structures, termed integrons, have been described and contain one or more gene cassettes located at a specific site. Integrons are defined by an intl gene encoding an integrase, a recombination site attl and a strong promoter. At least six classes of integrons have been determined according to their intl gene. Classes 1, 2 and 3 are the most studied and are largely implicated in the dissemination of antibiotic resistance. A gene cassette includes an open reading frame and, at the 3'-end, a recombination site attC. Integration or excision of cassettes occur by a site-specific recombination mechanism catalyzed by the integrase. However, insertion can occur, albeit rarely, at non-specific sites leading to a stable situation for the cassette. Cassettes are transcribed from the common promoter located in the 5'-conserved segment and expression of distal genes is reduced by the presence of upstream cassettes. Most gene cassettes encode antibiotic resistant determinants but antiseptic resistant genes have also been described. Integrons seem to have a major role in the spread of multidrug resistance in gram-negative bacteria but integrons in gram-positive bacteria were described recently. Moreover, the finding of super-integrons with gene-cassettes coding for other determinants (biochemical functions, virulence factors) in Vibrio isolates dating from 1888 suggests the likely implication of this multicomponent cassette-integron system in bacterial genome evolution before the antibiotic era and to a greater extent than initially believed.

Evaluation of BC-3 and BCP-1 cell lines in immunofluorescence assay to detect HHV-8 antibodies in Kaposi's sarcoma, multiple myeloma and other groups.

BACKGROUND: We describe a comparative study of an immunofluorescence assay using inducible BC-3 and BCP-1 cell lines as sources of HHV-8 antigens. STUDY DESIGN: Detection of both antibodies to proteins expressed in lytic cycle and during latency in sera from HIV-infected patients with KS, HIV-positive patients without KS, normal blood donors, HIV-negative pregnant women and HIV-negative patients with multiple myeloma. Where possible, detection of antibody was associated with nested PCR detection of HHV-8 in peripheral mononuclear cell (PBMC) samples collected from AIDS-KS patients. RESULTS: Immunofluorescence was more intense with the BC-3 cell line than with BCP-1, thus facilitating examination under the microscope. HHV-8 antibodies were detected among 82.75% of AIDS-KS patients, in 27.3% of HIV-infected homosexual men, 2% of blood donors and in 2% of pregnant women. No HHV-8 antibodies were detected in serum samples from HIV-negative patients presenting multiple myeloma. HHV-8 DNA sequences were detected and confirmed by southern blot hybridization in five out of 17 (29.4%) PBMC samples from AIDS-KS patients. Titre of antibodies to proteins expressed in lytic cycle was much higher than the titre of antibodies to proteins expressed during latency. CONCLUSIONS: Both immunofluorescence assays were found useful and HHV-8 seroprevalence rates reported in previous studies were confirmed. In addition, results obtained using these assays tend to provide evidence for a lack of epidemiological association between HHV-8 infection and development of multiple myeloma.