Maturation of the trans-Golgi network protease furin: compartmentalization of propeptide removal, substrate cleavage, and COOH-terminal truncation.

We have cloned a bovine cDNA encoding the trans-Golgi network (TGN) protease furin and expressed it via recombinant vaccinia viruses to investigate intracellular maturation. Pulse-chase labeling reveals that the 104-kD pro-furin bearing high mannose N-glycans is rapidly processed into the 98-kD protease whose N-glycans remain sensitive to endoglycosidase H for a certain period of time. Furthermore, in the presence of brefeldin A, pro-furin cleavage occurs. From these data we conclude that the ER is the compartment of propeptide removal. Studies employing the ionophore A23187 and DTT show that autocatalysis is Ca2+ dependent and that it does not occur under reducing conditions. Pro-furin produced under these conditions never gains endo H resistance indicating that it is retained in the ER. Coexpression of furin with the fowl plague virus hemagglutinin in the presence of brefeldin A and monensin reveals that furin has to enter the Golgi region to gain substrate cleaving activity. N-glycans of furin are sialylated proving its transit through the trans-Golgi network. A truncated form of furin is found in supernatants of cells. Truncation is inhibited in the absence of Ca2+ ions and in the presence of acidotropic agents indicating that it takes place in an acidic compartment of cells. Comparative analysis with furin expressed from cDNA reveals that the truncated form prevails in preparations of biologically active, endogenous furin obtained from MDBK cells. This observation supports the concept that secretion of truncated furin is a physiological event that may have important implications for the processing of extracellular substrates.

A randomized, double-blind, placebo-controlled study of benfluorex in HIV-infected patients with insulin resistance or impaired glucose tolerance.

PURPOSE: We previously reported a beneficial effect of benfluorex (BFL) on oral glucose tolerance test (OGTT) and visceral fat mass in an open-label study conducted in 60 HIV-infected patients. The objective of this study was to assess whether administration of BFL compared to placebo (PBO) improves insulin resistance (IR) in HIV+ patients with HAART- induced lipodystrophy. METHOD: 22 HIV-infected patients with IR or impaired glucose tolerance were double-blind randomly assigned to receive BFL 3 tablets/day or PBO for 24 weeks. Efficacy assessments included OGTT, abdominal computed tomography, and the measurement of fasting lipids. RESULTS: Change of median insulin AUC was -53.0 microIU/mL (IQR, -126.0 to -12.7) in the BFL group vs. +33.6 microIU/mL (IQR, 7.0 to 115.6) (p = .01) in PBO group. Weight decreased significantly in the BFL group (-2 kg +/- 2.6; IQR, -6.8 to 2.0) compared to the PBO group (0.8 kg +/- 1.7; IQR, -2.0 to 0.5) (p = .02). No significant changes in visceral or subcutaneous fat mass and plasma lipid level were observed between the two groups. CONCLUSION: Added to antiretroviral therapy, a 6-month therapy with BFL improved insulin sensitivity but is not sufficient to reduce significantly visceral fat mass.

Nelfinavir in HIV-HCV coinfected patients: a 24-month follow-up in a cohort of 82 patients.

This retrospective and longitudinal study evaluated the long-term hepatic tolerance of a nelfinavir (NFV)-antiretroviral combined regimen in 82 patients of the HCV-HIV Cohort of CISIH-Sud of Marseilles. Follow-up data (liver enzyme levels, CD4 cell count, HIV viral load, and metabolic parameters) of patients treated with NFV on inclusion or during the follow-up of the cohort were analyzed under treatment over 24 months. Comparisons were performed with X2 or Kruskal-Wallis tests. At baseline (n = 82), the median exposure to NFV was 4.1 months; 58 patients received NFV combined with NRTI and 24 with NNRTI. The median CD4 cell count was 337/mm3 [interquartile range (IR): 216-480) and 39.7% had an undetectable HIV RNA level. Qualitative HCV PCR was positive in 91% of the patients and 19/51 patients with liver biopsy were F3-F4. Median alanine and aspartate aminotransferase (ALAT, ASAT), gamma-glutamyltransferase (GT), and alkaline phosphatase (ALP) were 46 UI/liter (IR: 36-76), 55 UI/liter (IR: 32-97), 97 UI/liter (IR: 50-194), and 88 UI/liter (IR: 72-104), respectively, with 76% of the patients with ALAT/ASAT grade <2. Median follow-up was 23 months (IR: 13.8-37). No significant difference was observed in the distribution of ALAT, ASAT, GT, and ALP as well as of ALAT/ASAT grades over the 24-month study period. Patients treated with NFV + NNRTI had significantly higher GT and ALP levels at baseline with no significant increase during follow-up. Cholesterol, triglyceride, and glycemia distributions remained stable over time. In conclusion, this study showed a good hepatic and metabolic tolerance of a long-term NFV-combined regimen in HIV-HCV coinfected patients.

Hemispheric control of the writing hand: the effect of callosotomy in a left-hander.

We report a case of a left-hander with left hemispheric language. After callosotomy, he could use the left hand to write only random letters and digits, and he became right-handed for writing. Therefore, writing by left-handers with left hemispheric language dominance may be accomplished by transcallosal transmission of the linguistic content from the left hemisphere to the right.

Processing of viral glycoproteins by the subtilisin-like endoprotease furin and its inhibition by specific peptidylchloroalkylketones.

The spike glycoproteins of many enveloped viruses are proteolytically cleaved at the carboxytermini of sequences containing the basic motif R-X-K/R-R. Cleavage is often necessary for the fusion capacity of the glycoproteins and, thus, for virus infectivity. Among these viruses are pathogenic avian influenza viruses, human parainfluenza virus, human cytomegalovirus, and human immunodeficiency virus; it has been demonstrated that these viruses can be activated by furin. Indigenous furin has been identified in T-lymphocytes, which are host cells for HIV. Furin has been localized in the TGN and on the surface of cells after vectorial expression. Peptidylchloroalkylketones have been designed that inhibit with high specificity cleavage and fusion activity of viral glycoproteins, as well as virus replication.

Efficacy and tolerance of HCV treatment in HIV-HCV coinfected patients: the potential interaction of PI treatment.

PURPOSE: To evaluate tolerance and efficacy of an open-label interferon-ribavirin treatment and their determinants in 62 HCV-HIV coinfected patients in routine followup. METHOD: Patients received at least 6 and up to 12 months of combination interferon alpha-2b (peg or not) plus ribavirin. Determinants of therapeutic success were estimated by a multivariate logistic regression. RESULTS: Five patients stopped the study, 4 were lost to follow-up, and 53 participated in the entire therapeutic protocol. Among these 53, the end-of-treatment results showed complete clearance of HCV-RNA in 17 (32%). A sustained virologic response (SVR) after 6 or 9 months was observed in 9 (17%) patients, 3 relapsed, and data were not available for 5. Genotype 3a (odds ratio [OR] = 14.4; confidence interval [CI] = 1.84-110.3) favored SVR and treatment with protease inhibitor (PI) therapeutic resistance (OR = 14.4; CI = 1.01-200); as well, a higher fibrosis score tended to increase resistance (p =.11). Adverse events were reported by 24/53 patients (45.3%). CONCLUSION: HCV therapy associating interferon and ribavirin in HCV-HIV coinfected patients is well accepted even if tolerance is moderate. Treatment permitted SVR in at least 17% of the cases. This is likely when patients initiate treatment at the early fibrosis stage and are infected with genotype 3a. The potential interaction with PI therapy should be explored.

[Septicemic infection by spore forming bacteria in Crustacea, Isotopa]. / Infection septicémique a bactérie sporulée chez les Crustacés Isopodes.

A new type of disease localized to haemolymph has been discovered and studied in the oniscoid Armadillidium granulatum. The infection is due to a bacterium showing particularities of shape, and sporulating form structures, of nutritional requirements and of very slow but lethal pathogenic effect in visceral cavity of isopods.

Determinants and evolution of squamous intraepithelial lesions in HIV-infected women, 1991-2004.

This study presents a case-control nested analysis of cervical squamous intraepithelial lesions (SIL) in a cohort of 423 HIV-infected women with registered Pap smears between 1991 and 2004. Data on Pap smear results, CDC HIV classification, CD4 cell count and antiretroviral therapy were prospectively collected. Pap smears were classified using the Bethesda classification. Women had a median of three Pap smears registered in the database. The first Pap smear was registered

Purity of spiking agent affects partitioning of prions in plasma protein purification.

Prions are not detectable in the blood or plasma of persons afflicted with classical or variant Creutzfeldt-Jakob disease, and they have never been shown to be transmitted by blood or plasma products. Despite the uncertainty as to the presence and biophysical properties of prions in plasma, prion removal studies have been conducted using brain homogenate or microsomes prepared from prion-infected rodent brains as model prions. In this study, we compare the partitioning of different prion spiking agents, having different biophysical properties, in the processes used for plasma protein purification. We have found that membrane-bound prion spiking agents partition similarly, whereas purified, unbound pathogenic prion proteins can have significantly different partitioning properties depending on the conditions in the production process. We conclude that prion spiking studies for the evaluation of prion reduction in plasma protein purification should employ spiking agents with different biophysical properties to mimic partitioning of the theoretical prion contaminant. This will give greater assurance as to the prion safety margins of the life-saving plasma protein therapeutics and excipients.

Hemagglutinin activation of pathogenic avian influenza viruses of serotype H7 requires the protease recognition motif R-X-K/R-R.

The hemagglutinin of influenza virus A/FPV/Rostock/34 (H7) was altered at its multibasic cleavage site by site-directed mutagenesis and assayed for proteolytic activation after expression in CV-1 cells. The results indicated that the cellular protease responsible for activation recognizes the tetrapeptide motif R-X-K/R-R that must be presented in the correct sequence position. Studies on plaque variants of influenza virus A/fowl/Victoria/75 (H7N7) showed that alteration of the consensus sequence resulted in a loss of pathogenicity for chickens.

COOH-terminal sequence of the cellular prion protein directs subcellular trafficking and controls conversion into the scrapie isoform.

Efficient formation of scrapie isoform of prion protein (PrP(Sc)) requires targeting PrP(Sc) by glycophosphatidyl inositol (GPI) anchors to caveolae-like domains (CLDs). Redirecting the cellular isoform of prion protein (PrP(C)) to clathrin-coated pits by creating chimeric PrP molecules with four different COOH-terminal transmembrane domains prevented the formation of PrP(Sc). To determine if these COOH-terminal transmembrane segments prevented PrP(C) from refolding into PrP(Sc) by altering the structure of the polypeptide, we fused the 28-aa COOH termini from the Qa protein. Two COOH-terminal Qa segments differing by a single residue direct the transmembrane protein to clathrin-coated pits or the GPI form to CLDs; PrP(Sc) was formed from GPI-anchored PrP(C) but not from transmembrane PrP(C). Our findings argue that PrP(Sc) formation is restricted to a specific subcellular compartment and as such, it is likely to involve auxiliary macromolecules found within CLDs.

Rescue of vector-expressed fowl plague virus hemagglutinin in biologically active form by acidotropic agents and coexpressed M2 protein.

The hemagglutinin of the Rostock strain of fowl plague virus was expressed in CV-1 cells by a simian virus 40 vector, and its stability in the exocytotic transport process was examined by a fusion assay. A 50-fold increase in the fusion activity of the hemagglutinin was observed when expression occurred in the presence of ammonium chloride, Tris-HCl, or high doses of amantadine. When chloroquine, another acidotropic agent, was used, the hemagglutinin exposed at the cell surface had to be activated by trypsin, because intracellular cleavage was inhibited by this compound. Hemagglutinin mutants resistant to intracellular cleavage did not require acidotropic agents for full expression of fusion activity, when treated with trypsin after arrival at the cell surface. These results indicate that fowl plague virus hemagglutinin expressed by a simian virus 40 vector is denatured in the acidic milieu of the exocytotic pathway and that cleavage is a major factor responsible for the pH instability. Coexpression with the M2 protein also markedly enhanced the fusion activity of the hemagglutinin, and this effect was inhibited by low doses of amantadine. These results support the concept that M2, known to have ion channel function, protects the hemagglutinin from denaturation by raising the pH in the exocytotic transport system. The data also stress the importance of acidotropic agents or coexpressed M2 for the structural and functional integrity of vector-expressed hemagglutinin.

Modification of the cleavage activation of the influenza virus hemagglutinin by site-specific mutagenesis.

Factors determining cleavability of influenza virus hemagglutinin which is activated by ubiquitous cellular endoproteases were analysed by carrying out site-directed mutagenesis on the cloned hemaglutinin genes of strains A/FPV/Rostock/34 (subtype H7) and A/Port Chalmers/1/73 (subtype H3). Substitutions at the cleavage site of the H7 hemagglutinin indicate that the tetrapeptide Arg-X-Lys/Arg-Arg is the minimal consensus sequence recognized by the ubiquitous proteases. The H3 hemagglutinin also became susceptible to these enzymes, when additional arginines were inserted at the cleavage site. Three arginines were sufficient, when the carbohydrate was removed, whereas four additional arginines are needed when this carbohydrate was present, indicating that the accessibility of the cleavage motif is important for the protease. The appropriate localization of the basic cleavage motif within the amino acid sequence and the spatial structure of the hemagglutinin precursor is an additional prerequisite for cleavage.

Improved conformation-dependent immunoassay: suitability for human prion detection with enhanced sensitivity.

The presence of pathogenic prion protein (PrP(Sc)) in lymphoid tissues of variant Creutzfeldt-Jakob disease (vCJD) patients raises questions as to whether prions may be present in bodily fluids as well. Currently, transgenic mice are highly sensitive in vivo tools for the study of prions in tissues or fluids containing high levels of normal prion protein (PrP(C)). We report here an in vitro assay with virtually equivalent sensitivity incorporating a capture antibody into a sandwich conformation-dependent immunoassay (CDI), resulting in 30- to 100-fold increased sensitivity compared with the original, direct CDI. Furthermore, spiking plasma with vCJD prions in different preparations demonstrated that sandwich CDI detects prions with different biophysical properties at high sensitivity, even without proteinase K pretreatment of samples. Thus, sandwich CDI represents a powerful tool to study prions in bodily fluids of CJD/vCJD patients, with a turnaround time of less than 24 h.

Assembly of SIV virus-like particles containing envelope proteins using a baculovirus expression system.

The requirements for SIV particle assembly and envelope incorporation were investigated using a baculovirus expression system. The Pr56gag precursor protein expressed under control of the polyhedrin promoter (pPolh) produced high levels of immature retrovirus-like particles (VLP) upon expression in Sf9 insect cells. To determine the optimal conditions for envelope protein (Env) incorporation into VLP, two recombinant baculoviruses expressing the SIV envelope protein under control of a very late pPolh or a hybrid late/very late capsid/polyhedrin (Pcap/polh) promoter and a recombinant expressing a truncated form of the SIV envelope protein (Envt) under the hybrid Pcap/polh promoter were compared. We have observed that utilization of the earlier hybrid promoter resulted in higher levels of Env expression on the cell surface and its incorporation into budding virus particles. We have also found that the Envt protein is transported to the cell surface of insect cells and incorporated into VLP more efficiently than full-length Env. In addition, we examined the effect of coexpression of the protease furin, which has been implicated in the proteolytic cleavage of the Env precursor gp160 in mammalian cells. Coexpression of furin in insect cells resulted in more efficient proteolytic cleavage into gp120 and gp41, and the cleaved proteins were incorporated into VLP.

Influenza virus hemagglutinin with multibasic cleavage site is activated by furin, a subtilisin-like endoprotease.

Many viruses have membrane glycoproteins that are activated at cleavage sites containing multiple arginine and lysine residues by cellular proteases so far not identified. The proteases responsible for cleavage of the hemagglutinin of fowl plague virus, a prototype of these glycoproteins, has now been isolated from Madin-Darby bovine kidney cells. The enzyme has a mol. wt of 85,000, a pH optimum ranging from 6.5 to 7.5, is calcium dependent and recognizes the consensus sequence R-X-K/R-R at the cleavage site of the hemagglutinin. Using a specific antiserum it has been identified as furin, a subtilisin-like eukaryotic protease. The fowl plague virus hemagglutinin was also cleaved after coexpression with human furin from cDNA by vaccinia virus vectors. Peptidyl chloroalkylketones containing the R-X-K/R-R motif specifically bind to the catalytic site of furin and are therefore potent inhibitors of hemagglutinin cleavage and fusion activity.

Proteolytic processing of human cytomegalovirus glycoprotein B (gpUL55) is mediated by the human endoprotease furin.

Inhibition of endoproteolytic cleavage of glycoprotein B (gB; gpUL55) of human cytomegalovirus was achieved by treatment of infected fibroblasts with decanoyl peptidyl chloromethyl ketone (decRVKR-CMK), which inhibits the action of cellular subtilisin-like endoproteases with the amino acid recognition motif R x K/R R. Uncleaved gB precursor molecules of 160 kDa that were accumulated were endoglycosidase H resistant, suggesting that correct cellular transport occurred in the presence of the drug. The inhibitor also prevented endoproteolytic gB processing in CV-1 cells infected with a recombinant vaccinia virus-gB construct (VVgB). Evidence for direct involvement of the ubiquitous subtilisin-like endoprotease furin in gB cleavage was obtained from the observation that coinfection of CV-1 cells with WgB and a recombinant vaccinia-human furin construct reestablished endoproteolytic activity which was normally absent late after infection with WgB alone.

Subcellular colocalization of the cellular and scrapie prion proteins in caveolae-like membranous domains.

Results of transgenetic studies argue that the scrapie isoform of the prion protein (PrPSc) interacts with the substrate cellular PrP (PrPC) during conversion into nascent PrPSc. While PrPSc appears to accumulate primarily in lysosomes, caveolae-like domains (CLDs) have been suggested to be the site where PrPC is converted into PrPSc. We report herein that CLDs isolated from scrapie-infected neuroblastoma (ScN2a) cells contain PrPC and PrPSc. After lysis of ScN2a cells in ice-cold Triton X-100, both PrP isoforms and an N-terminally truncated form of PrPC (PrPC-II) were found concentrated in detergent-insoluble complexes resembling CLDs that were isolated by flotation in sucrose gradients. Similar results were obtained when CLDs were purified from plasma membranes by sonication and gradient centrifugation; with this procedure no detergents are used, which minimizes artifacts that might arise from redistribution of proteins among subcellular fractions. The caveolar markers ganglioside GM1 and H-ras were found concentrated in the CLD fractions. When plasma membrane proteins were labeled with the impermeant reagent sulfo-N-hydroxysuccinimide-biotin, both PrPC and PrPSc were found biotinylated in CLD fractions. Similar results on the colocalization of PrPC and PrPSc were obtained when CLDs were isolated from Syrian hamster brains. Our findings demonstrate that both PrPC and PrPSc are present in CLDs and, thus, support the hypothesis that the PrPSc formation occurs within this subcellular compartment.

Standards for the assay of Creutzfeldt-Jakob disease specimens.

Assays for the agent of Creutzfeldt-Jakob disease (CJD) include measurement of infectivity in different animal systems, such as wild-type or transgenic mice, and detection of PrP(Sc) by different methods and formats. The various assays could be best calibrated against each other by use of uniform readily available materials, and samples of four human brains, two from sporadic CJD patients, one from a variant CJD patient and one from a non-CJD patient, have been prepared as 10% homogenates dispensed in 2000 vials each for this purpose. Results of in vitro methods, particularly immunoblot assays, were compared in the first collaborative study described here. While dilution end-points varied, the minimum detectable volume was surprisingly uniform for most assays and differences in technical procedure, other than the sample volume tested, had no detectable systematic effect. The two specimens from sporadic CJD cases contained both type 1 and type 2 prion proteins in approximately equal proportions. The materials have been given the status of reference reagents by the World Health Organization and are available for further study and assessment of other in vitro or in vivo assay procedures.