Involvement of a small GTP binding protein in HIV-1 release

BACKGROUND: There is evidence suggesting that actin binding to HIV-1 encoded proteins, or even actin dynamics themselves, might play a key role in virus budding and/or release from the infected cell. A crucial step in the reorganisation of the actin cytoskeleton is the engagement of various different GTP binding proteins. We have thus studied the involvement of GTP-binding proteins in the final steps of the HIV-1 viral replication cycle. RESULTS: Our results demonstrate that virus production is abolished when cellular GTP binding proteins involved in actin polymerisation are inhibited with specific toxins. CONCLUSION: We propose a new HIV budding working model whereby Gag interactions with pre-existing endosomal cellular tracks as well as with a yet non identified element of the actin polymerisation pathway are required in order to allow HIV-1 to be released from the infected cell

Tryptophan 95, an Amino Acid Residue of the Caprine Arthritis Encephalitis Virus Vif Protein Which Is Essential for Virus Replication

AbstractThe Caprine arthritis encephalitis virus (CAEV) vif gene was demonstrated to be essential for efficient virus replication. CAEV Vif deletion mutants demonstrated an attenuated replication phenotype in primary goat cell cultures and resulted in abortive infection when inoculated into goats. In this study, we determined the in vitro replication phenotype of five CAEV Vif point mutant infectious molecular clones and the ability of the corresponding in vitro translated Vif proteins to interact with the CAEV Pr55gag in the glutathione S–transferase (GST) binding assay. Here we show that (i) three of the mutants (S170E, S170G, S197G) behaved as the wild-type CAEV according to virus replication and Vif–Gag interactions; (ii) one mutant (Vif 6mut) was replication incompetent and bound weakly to GST–Gag fusion proteins; and (iii) one mutant (Vif RG) was impaired for replication while retaining its interaction properties. This mutant points out the critical importance of the CAEV Vif tryptophan residue at position 95 for efficient virus replication, defining for this lentivirus a functional domain unrelated to the Gag binding region

HIV-2 Protease resistance defined in yeast cells

BACKGROUND: Inhibitors of the HIV-1 Protease currently used in therapeutic protocols, have been found to inhibit, although at higher concentrations, the HIV-2 encoded enzyme homologue. Similar to observations in HIV-1 infected individuals, therapeutic failure has also been observed for some patients infected with HIV-2 as a consequence of the emergence of viral strains resistant to the anti-retroviral molecules. In order to be able to define the specific mutations in the Protease that confer loss of susceptibility to Protease Inhibitors, we set up an experimental model system based in the expression of the viral protein in yeast. RESULTS: Our results show that the HIV-2 Protease activity kills the yeast cell, and this process can be abolished by inhibiting the viral enzyme activity. Since this inhibition is dose dependent, IC(50 )values can be assessed for each anti-retroviral molecule tested. We then defined the susceptibility of HIV-2 Proteases to Protease Inhibitors by comparing the IC(50 )values of Proteases from 7 infected individuals to those of a sensitive wild type laboratory adapted strain. CONCLUSION: This functional assay allowed us to show for the first time that the L90M substitution, present in a primary HIV-2 isolate, modifies the HIV-2 Protease susceptibility to Saquinavir but not Lopinavir. Developing a strategy based on the proposed yeast expressing system will contribute to define amino acid substitutions conferring HIV-2 Protease resistance

Stabilité d'un rideau visqueux.

Nous étudions les rideaux visqueux en écoulement vertical libre, soumis seulement au champ de gravité. Un liquide visqueux s'écoule depuis une fente, ce qui forme un rideau liquide, de faible épaisseur. En s'étirant sous l'effet de la gravité, le rideau voit sa largeur diminuer. Une étude des contraintes locales montre que cet écoulement présente des directions compressives. Ceci rend possible l'apparition de modes de flambage dans la direction horizontale du rideau. Nous étudions numériquement le seuil d'apparition de tels modes en fonction du rapport d'aspect du rideau. Dans cette étude, l'effet de la gravité reste faible (petit nombre de Jeffrey), et la vitesse d'injection du fluide au niveau de la fente est grande par rapport aux vitesses horizontales qui sont à l'origine des contraintes compressives

UFMylation of MRE11 is essential for telomere length maintenance and hematopoietic stem cell survival

International audienc

HIV-2 Protease resistance defined in yeast cells

Abstract Background Inhibitors of the HIV-1 Protease currently used in therapeutic protocols, have been found to inhibit, although at higher concentrations, the HIV-2 encoded enzyme homologue. Similar to observations in HIV-1 infected individuals, therapeutic failure has also been observed for some patients infected with HIV-2 as a consequence of the emergence of viral strains resistant to the anti-retroviral molecules. In order to be able to define the specific mutations in the Protease that confer loss of susceptibility to Protease Inhibitors, we set up an experimental model system based in the expression of the viral protein in yeast. Results Our results show that the HIV-2 Protease activity kills the yeast cell, and this process can be abolished by inhibiting the viral enzyme activity. Since this inhibition is dose dependent, IC50 values can be assessed for each anti-retroviral molecule tested. We then defined the susceptibility of HIV-2 Proteases to Protease Inhibitors by comparing the IC50 values of Proteases from 7 infected individuals to those of a sensitive wild type laboratory adapted strain. Conclusion This functional assay allowed us to show for the first time that the L90M substitution, present in a primary HIV-2 isolate, modifies the HIV-2 Protease susceptibility to Saquinavir but not Lopinavir. Developing a strategy based on the proposed yeast expressing system will contribute to define amino acid substitutions conferring HIV-2 Protease resistance.</p

Deglycosylation of Tropheryma whipplei biofilm and discrepancies between diagnostic results during Whipple's disease progression

International audienceWhipple's disease is a systemic infectious disease associated with the bacterium Tropheryma whipplei. Numerous reports have presented puzzling discrepancies between diagnosis methods. We addressed this confusion using fluorescent in situ hybridization and immunofluorescence assays to evaluate 34 duodenal biopsies and 1 lymph node biopsy from Whipple's patients. We showed the presence of bacteria in both CK20(+) epithelial cells and CD68(+) macrophages. Bacteria are found embedded in a biofilm hindering the detection of T. whipplei. Only after treatment of biopsies by glycosidases, co-localization of T. whipplei RNA/DNA with bacterial proteins was restored. Moreover, using 13 bronchoalveolar lavages and 7 duodenal biopsies, we found that hydrolysis of the biofilm weakened the bacteria, facilitated bacterial DNA extraction and improved the sensitivity of qPCR detection by up to 1000x opening new perspectives for diagnostic and scientific approaches

Yeast-based assay for measuring the functional activity of an HIV-1 protease in response to an antiviral agent

US Patent 9,493,769no abstrac