Lack of the detection of XMRV or polytropic MLV-related sequences in blood cells from HIV-1-infected patients in Spain.

BACKGROUND: Xenotropic murine leukemia virus-related virus (XMRV) and polytropic murine leukemia virus (MLV)-related virus are recently described human gammaretroviruses that have been associated with prostate cancer and chronic fatigue syndrome. These studies have been controversial because a number of laboratories have been unable to find evidence of XMRV in similar groups of patients or controls. Because the existence of XMRV raises many questions, we decided to study its presence in a group of patients infected with HIV-1 with a high proportion of intravenous drug use and coinfection by hepatitis C virus. METHODS: Forty HIV-1-infected patients under follow-up in our institution were screened for XMRV/MLV by nested polymerase chain reaction using primers targeting the gag and env region. Specific primers for mouse mitochondrial DNA were used to rule out contamination. RESULTS: No evidence of XMRV or polytropic MLV-related sequences was found in any sample from patients or controls. Four samples yielded polymerase chain reaction bands whose sequence corresponded to murine endogenous retroviral sequences, however, contamination with mouse cell DNA was subsequently confirmed. CONCLUSIONS: XMRV/MLV viruses do not seem to be associated with HIV-1 infection or intravenous drug use. Contamination of samples or reagents by genomic murine DNA or XMRV vectors could account for the sporadic detection of positive samples for XMRV and related agents.

Detection and quantification of the K103N mutation in HIV reverse transcriptase by pyrosequencing.

Prolonged treatment of human immunodeficiency virus (HIV)-infected patients with nonnucleoside reverse transcriptase inhibitors (NNRTIs) might result in the selection of resistant mutants, the most frequent being the K103N mutation in reverse transcriptase. Resistance mutations are routinely detected by Sanger sequencing of the whole viral population, which does not detect sequence variants with frequencies below 20%. We have developed a pyrosequencing approach for the analysis of codon 103 of the HIV reverse transcriptase gene in the circulating viral population that detects variants below the limit of conventional sequencing. The method was tested with samples from 5 controls (not exposed to NNRTIs), 6 from patients exposed to NNRTIs and having a K103N mutant virus population detected by conventional sequencing, and 9 from patients previously exposed to NNRTIs that had a wild-type virus population by conventional sequencing. In 7 of 9, samples the mutation could not be detected by either the standard assay or pyrosequencing, while in 2 samples persistence of the mutation could be detected by pyrosequencing. The method might be of practical use in detecting minority variants of HIV in the clinical setting, in epidemiological studies with large numbers of samples, or as a complement to more complex approaches.

The chemokine receptor CXCR4 and the metalloproteinase MT1-MMP are mutually required during melanoma metastasis to lungs.

Melanoma is the most aggressive skin cancer once metastasis begins; therefore, it is important to characterize the molecular players involved in melanoma dissemination. The chemokine receptor CXCR4 and the membrane-bound metalloproteinase MT1-MMP are expressed on melanoma cells and represent candidate molecules for the control of metastasis. Using human melanoma transfectants that either overexpress or silence CXCR4 or MT1-MMP, or that have a combination of overexpression and interference of these proteins, we show that CXCR4 and MT1-MMP coordinate their activities at different steps along melanoma cell metastasis into the lungs. Results from in vivo xenograft mouse models of melanoma lung colonization and mice survival and short-term, homing nested polymerase chain reaction experiments from lung samples indicated that CXCR4 is required at early phases of melanoma cell arrival in the lungs. In contrast, MT1-MMP is not needed for these initial steps but promotes subsequent invasion and dissemination of the tumor with CXCR4. Investigation of potential cross talk between CXCR4 and MT1-MMP revealed that MT1-MMP accumulates intracellularly after melanoma cell stimulation with the CXCR4 ligand CXCL12, and that this process involves the activation of the Rac-Erk1/2 pathway. Subsequent to cell contact with specific basement membrane proteins, MT1-MMP redistributes to the cell membrane in a phosphatidylinositol 3-kinase-dependent manner. These results suggest that combination therapies that target CXCR4 and MT1-MMP should improve the limitations of the current therapies for metastatic melanoma.

The DC-SIGN-related lectin LSECtin mediates antigen capture and pathogen binding by human myeloid cells.

Liver and lymph node sinusoidal endothelial cell C-type lectin (LSECtin [CLEC4G]) is a C-type lectin encoded within the liver/lymph node-specific intercellular adhesion molecule-3-grabbing nonintegrin (L-SIGN)/dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN)/CD23 gene cluster. LSECtin expression has been previously described as restricted to sinusoidal endothelial cells of the liver and lymph node. We now report LSECtin expression in human peripheral blood and thymic dendritic cells isolated ex vivo. LSECtin is also detected in monocyte-derived macrophages and dendritic cells at the RNA and protein level. In vitro, interleukin-4 (IL-4) induces the expression of 3 LSECtin alternatively spliced isoforms, including a potentially soluble form (Delta 2 isoform) and a shorter version of the prototypic molecule (Delta3/4 isoform). LSECtin functions as a pathogen receptor, because its expression confers Ebola virus-binding capacity to leukemic cells. Sugar-binding studies indicate that LSECtin specifically recognizes N-acetyl-glucosamine, whereas no LSECtin binding to Mannan- or N-acetyl-galactosamine-containing matrices are observed. Antibody or ligand-mediated engagement triggers a rapid internalization of LSECtin,which is dependent on tyrosine and diglutamic-containing motifs within the cytoplasmic tail. Therefore, LSECtin is a pathogen-associated molecular pattern receptor in human myeloid cells. In addition, our results suggest that LSECtin participates in antigen uptake and internalization, and might be a suitable target molecule in vaccination strategies.