Role of Gag in HIV Resistance to Protease Inhibitors

Cleavage of Gag and Gag-Pol precursors by the viral protease is an essential step in the replication cycle of HIV. Protease inhibitors, which compete with natural cleavage sites, strongly impair viral infectivity and have proven to be highly valuable in the treatment of HIV-infected subjects. However, as with all other antiretroviral drugs, the clinical benefit of protease inhibitors can be compromised by resistance. One key feature of HIV resistance to protease inhibitors is that the mutations that promote resistance are not only located in the protease itself, but also in some of its natural substrates. The best documented resistance-associated substrate mutations are located in, or near, the cleavage sites in the NC/SP2/p6 region of Gag. These mutations improve interactions between the substrate and the mutated enzyme and correspondingly increase cleavage. Initially described as compensatory mutations able to partially correct the loss of viral fitness that results from protease mutations, changes in Gag are now recognized as being directly involved in resistance. Besides NC/SP2/p6 mutations, polymorphisms in other regions of Gag have been found to exert various effects on viral fitness and or resistance, but their importance deserves further evaluation

Discordant Increases in CD4+ T Cells in Human Immunodeficiency Virus-Infected Patients Experiencing Virologic Treatment Failure: Role of Changes in Thymic Output and T Cell Death

Some patients infected with human immunodeficiency virus (HIV) who are experiencing antiretroviral treatment failure have persistent improvement in CD4+ T cell counts despite high plasma viremia. To explore the mechanisms responsible for this phenomenon, 2 parameters influencing the dynamics of CD4+ T cells were evaluated: death of mature CD4+ T cells and replenishment of the CD4+ T cell pool by the thymus. The improvement in CD4+ T cells observed in patients with treatment failure was not correlated with spontaneous, Fas ligand-induced, or activation-induced T cell death. In contrast, a significant correlation between the improvement in CD4+ T cell counts and thymic output, as assessed by measurement of T cell receptor excision circles, was observed. These observations suggest that increased thymic output contributes to the dissociation between CD4+ T cell counts and viremia in patients failing antiretroviral therapy and support a model in which drug-resistant HIV strains may have reduced replication rates and pathogenicity in the thymu

Peptide P5 (residues 628–683), comprising the entire membrane proximal region of HIV-1 gp41 and its calcium-binding site, is a potent inhibitor of HIV-1 infection

The membrane proximal region (MPR) of the transmembrane subunit, gp41, of the HIV envelope glycoprotein plays a critical role in HIV-1 infection of CD4+ target cells and CD4-independent mucosal entry. It contains continuous epitopes recognized by neutralizing IgG antibodies 2F5, 4E10 and Z13, and is therefore considered to be a promising target for vaccine design. Moreover, some MPR-derived peptides, such as T20 (enfuvirtide), are in clinical use as HIV-1 inhibitors. We have shown that an extended MPR peptide, P5, harbouring the lectin-like domain of gp41 and a calcium-binding site, is implicated in the interaction of HIV with its mucosal receptor. We now investigate the potential antiviral activities of P5 and other such long MPR-derived peptides. Structural studies of gp41 MPR-derived peptides using circular dichroism showed that the peptides P5 (a.a.628–683), P1 (a.a.648–683), P5L (a.a.613–683) and P7 (a.a.613–746) displayed a well-defined α-helical structure. Peptides P5 inhibited HIV-1 envelope mediated cell-cell fusion and infection of peripheral blood mononuclear cells by both X4- and R5-tropic HIV-1 strains, whereas peptides P5 mutated in the calcium binding site or P1 lacked antiviral activity, when P5L blocked cell fusion in contrast to P7. Strikingly, P5 inhibited CD4-dependent infection by T20-resistant R5-tropic HIV-1 variants. Cell-cell fusion studies indicated that the anti-HIV-1 activity of P5, unlike T20, could not be abrogated in the presence of the N-terminal leucine zipper domain (LZ). These results suggested that P5 could serve as a potent fusion inhibitor

Functional diversity of HIV-1 envelope proteins expressed by contemporaneous plasma viruses

<p>Abstract</p> <p>Background</p> <p>Numerous studies have shown that viral quasi-species with genetically diverse envelope proteins (Env) replicate simultaneously in patients infected with the human immunodeficiency virus type 1 (HIV-1). Less information is available concerning the extent that envelope sequence diversity translates into a diversity of phenotypic properties, including infectivity and resistance to entry inhibitors.</p> <p>Methods</p> <p>To study these questions, we isolated genetically distinct contemporaneous clonal viral populations from the plasma of 5 HIV-1 infected individuals (n = 70), and evaluated the infectivity of recombinant viruses expressing Env proteins from the clonal viruses in several target cells. The sensitivity to entry inhibitors (enfuvirtide, TAK-799), soluble CD4 and monoclonal antibodies (2G12, 48d, 2F5) was also evaluated for a subset of the recombinant viruses (n = 20).</p> <p>Results</p> <p>Even when comparisons were restricted to viruses with similar tropism, the infectivity for a given target cell of viruses carrying different Env proteins from the same patient varied over an approximately 10-fold range, and differences in their relative ability to infect different target cells were also observed. Variable region haplotypes associated with high and low infectivity could be identified for one patient. In addition, clones carrying unique mutations in V3 often displayed low infectivity. No correlation was observed between viral infectivity and sensitivity to inhibition by any of the six entry inhibitors evaluated, indicating that these properties can be dissociated. Significant inter-patient differences, independent of infectivity, were observed for the sensitivity of Env proteins to several entry inhibitors and their ability to infect different target cells.</p> <p>Conclusion</p> <p>These findings demonstrate the marked functional heterogeneity of HIV-1 Env proteins expressed by contemporaneous circulating viruses, and underscore the advantage of clonal analyses in characterizing the spectrum of functional properties of the genetically diverse viral populations present in a given patient.</p

Residential exposure to solar ultraviolet radiation and incidence of childhood hematological malignancies in France

Few studies have investigated the relationship between solar ultraviolet radiation (UV) and childhood hematological malignancies (CHM). This study addresses the associations between residential UV exposure at diagnosis and the incidence of types and subtypes of CHM, by age and gender, in France, over a long period, on the fine scale of the 36,326 Communes that constitute mainland France. The 9,082 cases of acute leukemia and 3,563 cases of lymphoma diagnosed before the age of 15 years from 1990 to 2009 were provided by the French National Registry of Childhood Hematological Malignancies. The incidence of CHM was calculated by Commune, year, age and gender and expressed as the standardized incidence ratio (SIR). UV data from 1988 to 2007 were extracted from the EUROSUN database. The annual daily average UV exposure of the children ranged from 85.5 to 137.8 J/cm2. For each additional 25 J/cm2, there was a significant increase in precursor B-cell acute lymphoblastic leukemia (PBC-ALL) in children aged less than 5 years (SIR 1.18; 95 % CI 1.10–1.27). Further analysis of PBC-ALL in the young children suggested a better fit of models with a threshold, with the risk increasing above 100 J/cm2, for which the SIR was 1.24 (95 % CI 1.14–1.36) for a 25 J/cm2 increase. The results remained stable in analyses stratifying by deprivation index or degree of urbanization of the Communes. The study suggests that higher residential UV exposure may be positively associated with a higher incidence of PBC-ALL in early childhood

Enhancement of the influenza A hemagglutinin (HA)-mediated cell-cell fusion and virus entry by the viral neuraminidase (NA).

International audienceBACKGROUND: The major role of the neuraminidase (NA) protein of influenza A virus is related to its sialidase activity, which disrupts the interaction between the envelope hemagglutinin (HA) protein and the sialic acid receptors expressed at the surface of infected cells. This enzymatic activity is known to promote the release and spread of progeny viral particles following their production by infected cells, but a potential role of NA in earlier steps of the viral life cycle has never been clearly demonstrated. In this study we have examined the impact of NA expression on influenza HA-mediated viral membrane fusion and virion infectivity. METHODOLOGY/PRINCIPAL FINDINGS: The role of NA in the early stages of influenza virus replication was examined using a cell-cell fusion assay that mimics HA-mediated membrane fusion, and a virion infectivity assay using HIV-based pseudoparticles expressing influenza HA and/or NA proteins. In the cell-cell fusion assay, which bypasses the endocytocytosis step that is characteristic of influenza virus entry, we found that in proper HA maturation conditions, NA clearly enhanced fusion in a dose-dependent manner. Similarly, expression of NA at the surface of pseudoparticles significantly enhanced virion infectivity. Further experiments using exogenous soluble NA revealed that the most likely mechanism for enhancement of fusion and infectivity by NA was related to desialylation of virion-expressed HA. CONCLUSION/SIGNIFICANCE: The NA protein of influenza A virus is not only required for virion release and spread but also plays a critical role in virion infectivity and HA-mediated membrane fusion

Relationship between QT interval and outcome in low-flow low-gradient aortic stenosis with low left ventricular ejection fraction

Background QT interval has been shown to be associated with cardiovascular events. There is no data regarding the association between QT interval and left ventricular (LV) function and prognosis in patients with low LV ejection fraction (LVEF), low‐flow, low‐gradient aortic stenosis (LF‐LG AS). We aimed to examine the relationship between corrected QT interval (QT c) and LV function and outcome in these patients. Methods and Results Ninety‐three patients (73±10 years; 74% men) with LF‐LG AS (mean gradient 450 ms in men and >470 ms in women. LV global longitudinal strain was measured by speckle tracking and expressed in absolute value |%|. QT c correlated with the following: global longitudinal strain (r=−0.40, P=0.005), LVEF (r=−0.27, P=0.02), stroke volume (r=−0.35, P=0.007), and B‐type natriuretic peptide (r=0.45, P=0.0006). During a median follow‐up of 2.0 years, 49 patients died. Prolonged QT c was associated with a 2‐fold increase in all‐cause mortality (hazard ratio=2.05; P=0.01) and cardiovascular mortality (hazard ratio=1.89; P=0.04). In multivariable analysis adjusted for EuroSCORE, aortic valve replacement, previous myocardial infarction, LVEF, and ß‐blocker medication, prolonged QT c was independently associated with all‐cause mortality (hazard ratio=2.56; P=0.008) and cardiovascular mortality (hazard ratio=2.50; P=0.02). Conclusions In patients with LF‐LG AS and reduced LVEF, longer QT c interval was associated with worse LV function and increased risk of death. Assessment of QT c may provide a simple and inexpensive tool to enhance risk stratification in LF‐LG AS patients

Human papillomavirus genotype distribution in tonsil cancers.

International audienceBACKGROUND: The incidence of tonsil cancers has increased in several countries. French data on HPV prevalence in tonsil cancers are scarce. The objective of this study was thus to assess the overall and type specific HPV prevalence in tonsil histological samples. METHODS: This French retrospective multicenter study involved 12 centres located throughout the country. Were included 185 histological samples collected from year 2000 to 2009 with a validated diagnosis of tonsil invasive carcinomas. HPV prevalence was studied according to gender, age and histological type of cancer. RESULTS: Overall HPV prevalence was 57% in tonsil cancers. Mean age of diagnosis was comparable in HPV positive tonsils cases (60 ± 11.2) and HPV negative tonsil cases (59 ± 9.6). HPV prevalence was significantly higher in female than in male cases (28/35 versus 78/150 in tonsil cases, respectively, P = 0.003). About 53% of tonsil cases were infected by a single HPV type. Only eight (4%) samples were infected by more than one HPV type. Among HPV positive samples, HPV 16 was found in 89% of tonsil cases. All other HPV types had prevalence below 5%. CONCLUSIONS: Our results indicate that HPV is common in tonsil carcinomas and emphasize the predominant role of HPV 16