Antibody responses to hepatitis C envelope proteins in patients with acute or chronic hepatitis C

Antibody responses to the hepatitis C virus (HCV) envelope proteins E1 and E2 were analyzed using two original assays in sera from 86 patients in different stages of disease. A Western blot assay and an immunofluorescence assay (IFA) were developed using envelope proteins produced, respectively, in Escherichia coli and in CV1 cells infected with a recombinant SV40. As a third method, the INNO-LIA HCV Ab III assay including E2 synthetic peptides was used. Of 38 chronically infected patients positive for anti-E2 antibodies by IFA, 26 were positive in the Western blot assay (68%) and 25 in the INNO-LIA test (66%). Thus, the detection of anti-envelope antibodies is highly dependent on the antigen formulation, and a native glycosylated form of the proteins is probably needed for their efficient detection. This study shows that the antibody response to HCV envelope proteins depends on the phase of infection. A few acutely infected patients displayed a response to E1 or E2 (36% by Western blot, 7% by IFA), and these antibodies seem to develop in patients evolving toward chronicity. The high prevalence in chronically infected subjects (62% to E2 by Western blot, 90% by IFA), particularly in subjects with essential mixed cryoglobulinemia (68% and 100%), confirms that the resolution of infection involves more than these antibodies. The antienvelope response in patients treated with interferon was investigated, but no significant relationship was found between antibody level prior to treatment and the evolution of hepatitis. The detection of anti-envelope antibodies, therefore, is not predictive of the response to antiviral therapy.

Effects of P2 cleavage site mutations on poliovirus polyprotein processing

The poliovirus genome comprises a single open reading frame which is translated to give one large polyprotein. The proteolytic cascade involved in the processing of this polyprotein is not yet understood in full detail,particularly concerning the processing of P2-P3, the precursor to the viral nonstructural polypeptides, 2A, 2B, 2C, 3A, 3B, 3C, and 3D. To investigate the possibility that the cleavage events within P2 and at the 2C/3A junction occur in an ordered fashion, we used oligonucleotide-directed mutagenesis of poliovirus cDNA to modify the 3C(prn)-mediated cleavage sites. The Gin residue of the Gin-Gly sequence at the 2A/2B, 2B/2C, and 2C/3A junctions in the poliovirus polyprotein was replaced by Asn, Glu, Asp, or Lys. The effects of each of these substitutions were studied in vivo after transfection onto HeLa cells and in vitro in a cell-free translation assay, using full-length mutated RNA transcripts. Only the mutant with the Glu-Gly sequence at the 2C/3A junction was viable. Analysis of the in vitro processing profiles showed that the efficiency of the 3C protease cleavage at any of the sites in P2 was in the following order: Gin-Gly > Glu-Gly > Asn-Gly. No cleavage could be detected with the Asp-Gly or Lys-Gly sequence at any junction. Lack of 2A/2B or 2B/2C cleavage had no consequences on the cleavage efficiency at other Gin-Gly sites in the polyprotein. Abolition of cleavage at the 2C/3A junction did not prevent the generation of the 2A, 2B, and 3CD polypeptides. Thus, these polypeptides. Thus, these polypeptides could be produced independently of the generation of the P2 and P3 precursors.

Human immunodeficiency virus type 1 neutralizing antibody serotyping using serum pools and an infectivity reduction assay

Classification of human immunodeficiency virus type 1 (HIV-1) by neutralization serotype may be important for the design of active and passive immunization strategies. Neutralizing antibody serotyping is hindered by the lack of standard reagents and assay format, and by the weak activity of many individual sera. To facilitate cross-clade neutralization analysis, we used an infectivity reduction assay (IRA) and selected clade-specific serum (or plasma) pools from subjects infected with clade B and E HIV-1, respectively. Several serum pools were utilized; some were selected for strong neutralizing activity against intraclade viruses and others were derived from conveniently available samples. Against a panel of 51 clade B and E viruses, serum pools displayed strong neutralization of most intraclade viruses and significantly diminished cross-clade neutralization. Results were confirmed against a blinded panel of 20 viruses. The data indicate that the phylogenetic classification of virus subtypes B and E corresponds to two distinct neutralization serotypes. This approach to neutralizing antibody serotyping may be useful in defining the antigenic relationship among viruses from other clades.

Safety of Acyclovir in General Practice: A Review of the Literature

Published data has been reviewed with the intent to determine the safety with which topical or oral acyclovir may be prescribed to immunocompetent patients outside specialist centres. The extent of the pre- and post-marketing development programme has made it possible to assess the main adverse effects associated with the drug, including the effects of high dosage, prolonged treatment and maternal exposure during the course of pregnancy. Possible risk factors are discussed and the overall reliability of the observations are considered. In conclusion it appears that with certain precautions there is little risk attached to the wider use of these formulations of acyclovir.

Inhibition of human immunodeficiency virus type 1 production in infected peripheral blood mononuclear cells by human leukocyte antigen class I-specific antibodies: evidence for a novel antiviral mechanism

A well-characterized mechanism by which anti-HLA class I monoclonal antibodies (MAb) inhibit human immunodeficiency virus type 1 (HIV-1) propagation in in vitro cell cultures is the neutralization of the virus through interactions with HLA molecules associated with the virion envelope. Yet, the possibility that another mechanism of inhibition might affect a postbinding stage of the virus life cycle has been strongly suggested by our previous investigations. To demonstrate that the interaction of MAb B1-1G6 with the light chain of cell surface-expressed HLA class I molecules inhibits a postbinding step of the HIV-1 life cycle, peripheral blood mononuclear cells (PBMCs) were exposed to viruses grown in HLA class I-negative, CD4-positive cells (these viruses, which did not carry HLA class I molecules, cannot be neutralized by anti-HLA MAb during the first round of infection), and PCR was used at various times postexposure to search for the different forms of HIV-1 DNA and RNA in virus-exposed PBMCs cultured in either the presence or [correction of] absence of MAb B1-1G6. Although viral DNA was found in MAb B1-1G6-treated cells, spliced HIV-1 mRNA could not be detected in those cells. In contrast, HIV-1 gene expression was found in HIV-1-infected PBMCs treated with B9-12-1, another HLA class I-specific MAb which prevents infection of cells by cell-free viruses but which fails to inhibit cell-to-cell transmission of HIV-1. These results highlight a second antiviral mechanism by which anti-HLA MAb inhibit in vitro HIV-1 propagation.

Processing of the E1 glycoprotein of hepatitis C virus expressed in mammalian cells

The structural part of the hepatitis C virus (HCV) genome encodes a capsid protein, C and two envelope glycoproteins, E1 and E2, released from the virus polyprotein precursor by signalase(s) cleavage(s). The processing of E1 was investigated by infecting simian cells with recombinant vaccinia viruses expressing parts of the HCV structural proteins. When the predicted E1 sequence was expressed alone (amino acid residues 174-370 of the polyprotein) or with the capsid protein gene (residues 1-370). it showed an apparent molecular mass of 35 kDa as measured by SDS-PAGE analysis. However, when E1 was expressed as part of a truncated C-E1-truncated E2 polypeptide (residues 132-383), the processed E1 product had the expected apparent molecular mass of 31 kDa, suggesting that flanking sequences are necessary for the generation of the mature 31 kDa El form. The N-terminal sequence of the two E1 forms was found to be the same. Analysis of the glycosylation pattern showed that, in both species, only four of the five potential N-linked glycosylation sites were recognized, indicating that glycosylation was not involved in the molecular mass difference. We showed that expression of E1 with or without the hydrophobic stretch of amino acids residues 371-383, defined as the E2 signal sequence, may be responsible for the difference in electrophoretic mobility of the two E1 species. In vitro translation assays and site-directed mutagenesis experiments suggest that this sequence remains part of the 31 kDa E1 mature protein.

[Effects of different doses of edrophonium antagonism of mivacurium-induced neuromuscular block in the presence of nitrous oxide, propofol, and alfentanil anesthesia]

PURPOSE

The purpose of this study was to determine the dose-response relationships for edrophonium antagonism of mivacurium-induced neuromuscular block.

METHOD

Seventy-five ASA physical status I or II adults were given mivacurium 0.15 mg.kg-1 followed by an infusion (7 micrograms.kg-1.min-1) during alfentanil-propofol-N2O anaesthesia. Train-of-four stimulation (TOF) was applied to the ulnar nerve every 20 sec and the response of the adductor digiti minimi was recorded (Relaxograph NMT-100, DATEX, Helsinki, Finland). Mivacurium infusion was adjusted at five minutes intervals in order to keep the height of the first twitch in TOF (T1) at 5% of its control value. At the end of surgery, the mivacurium infusion was stopped and edrophonium 0.0, 0.05, 0.1, 0.5 or 1.0 mg.kg-1 combined respectively with glycopyrrolate 0.0, 0.0005, 0.001, 0.005 or 0.01 mg.kg-1 were administered by random allocation.

RESULTS

All four edrophonium doses tested were statistically different from placebo with regard to time to attain a TOF ratio (fourth twitch in TOF/T1) = 0.7 (0.05:780 +/- 179, 0.1:727 +/- 216, 0.5:547 +/- 287 and 1.0:640 +/- 236 vs 0.0 mg.kg-1:1089 +/- 323 sec P < 0.05). Does of 0.1, 0.5 and 1.0 mg.kg-1 permitted faster recovery time of T1 from 10 to 95% (T10-95) (567 +/- 236, 419 +/- 166, 555 +/- 288 vs 861 +/- 224 sec P < 0.05) and from 25 to 75% (T25-75) (253 +/- 121, 147 +/- 92, 217 +/- 175 vs 429 +/- 154 sec P < 0.05) than did placebo. However, data showed considerable variability for all neuromuscular indices, no matter the dose of edrophonium used.

CONCLUSION

Edrophonium in doses of 0.1 mg.kg-1 and higher permitted faster recovery of all indices from a mivacurium-induced block during alfentanil-propofol-N2O anaesthesia than did placebo.

Varying mercury exposure with varying food source in a James Bay Cree community

James Bay Quebec Crees are exposed to methylmercury (MM) through fish consumption. Hair mercury concentrations were measured in women of child-bearing age and men and women 40 years of age and above in a small Cree community of James Bay (with traditionally low exposure to MM) before and after fishing expeditions to inland lakes where fish were contaminated with methylmercury. Median hair mercury concentrations in persons 40 years and above increased from 4.1 mg/kg to 9.9 mg/kg and the highest value from 17.4 to 47.2 mg/kg. A similar increase was seen after a second fishing expedition where the median hair concentration increased from 3.4 mg/kg to 7.2 mg/kg and the highest value from 17.7 to 49.9 mg/kg. Populations with traditionally low exposure to MM can become highly exposed with changes in sources or quantities of fish consumed.

Protection of non-murine mammals against encephalomyocarditis virus using a genetically engineered Mengo virus

Genetically engineered Mengo viruses with artificial deletions in the 5' noncoding poly(C) tracts are highly attenuated for pathogenicity when introduced as live vaccines into the natural murine host. Inoculation produces lifelong protective immunity without disease or viral persistence. This report extends the vaccination studies to non-murine hosts, including baboons, macaques and domestic pigs, all of which are susceptible to severe cardiovirus epizootics. All animals of these species that were inoculated with vMC24, an engineered strain of Mengo, seroconverted. When the immunized animals were challenged, they were protected against lethal doses of encephalomyocarditis virus (EMCV) derived from currently circulating epizootic strains. In baboons, the neutralizing antibody titers induced by vMC24 were significantly higher than from an inactivated EMCV vaccine. Moreover, terminal histopathology on baboons (inoculated intramuscularly), macaques (inoculated intracerebrally), and pigs (inoculated intramuscularly) showed few, if any, gross lesions characteristic of EMCV-like disease, in the vMC24 vaccinates. We suggest that genetically engineered, short poly(C) Mengo viruses may be universally potent attenuated vaccines for many types of animals and can possibly provide safe, efficacious protection against all cardioviruses of the EMCV serotype.

Continuous intravenous administration of ketorolac reduces pain and morphine consumption after total hip or knee arthroplasty

The purpose of this study was to determine the analgesic efficacy, opioid-sparing effect, and tolerability of ketorolac administered as an intravenous (i.v.) bolus followed by a continuous infusion after total hip or knee arthroplasty. After general anesthesia, patients received either placebo or ketorolac 30 mg i.v. as a bolus over 15-30 s followed by a continuous i.v. infusion of ketorolac 5 mg/h for 24 h. All patients received patient-controlled i.v. morphine with no background infusion. Patients were assessed at 2, 4, 6, and 24 postoperatively with respect to analgesia, morphine consumption, side effects, and blood loss. Patients receiving ketorolac reported were less sedated and required fewer antiemetics. There was no difference in blood loss. Patients receiving ketorolac reported better analgesia and used less morphine (35% for hips and 44% for knees) than those receiving placebo.

Identification and site-directed mutagenesis of the primary (2A/2B) cleavage site of the hepatitis A virus polyprotein: functional impact on the infectivity of HAV RNA transcripts

The junction between 2A and 2B proteins of the hepatitis A virus (HAV) polyprotein is processed by the virus-encoded 3C protease to liberate the precursor for capsid proteins, but details of this cleavage remain poorly defined. We identified the location of this primary cleavage by a novel approach involving expression of HAV polypeptides in eukaryotic cells via recombinant vaccinia viruses. A substrate polyprotein spanning the putative HAV 2A/2B site was fused at its C-terminus to a poliovirus VP1 reporter sequence. This substrate was cleaved efficiently in trans by protease 3C derived from another recombinant vaccinia virus expressing a 3C precursor protein. N-terminal sequencing of the 2B-poliovirus VP1 fusion product identified the site of cleavage as the Gln836/Ala837 dipeptide, 144 residues upstream of the originally predicted site. Two mutations were introduced at the P1 position of the 2A/2B site. Gln836-->Asn, and Gln836-->Arg. Asn substitution at the P1 residue reduced the efficiency of cleavage in the vaccinia expression system and resulted in a small replication focus phenotype of virus rescued from infectious HAV RNA transcripts. Arg substitution abolished cleavage and was lethal to HAV replication. In addition to identifying the site of the primary HAV polyprotein cleavage, these results shed light on the in vivo specificities of the HAV 3C protease.

Dose-response relationships for edrophonium antagonism of mivacurium-induced neuromuscular block during N2O-enflurane-alfentanil anaesthesia

The purpose of this study was to determine the dose-response relationships for edrophonium antagonism of mivacurium-induced neuromuscular block. Seventy-five ASA I or II adults were given mivarcurium 0.15 mg x kg(-1) followed by an infusion (7 micrograms x kg(-1) x min(-1) during alfentanil-propofol-N2O-enflurane anaesthesia. Train-of-four stimulation (TOF) was applied to the ulnar nerve every 20 sec and the response of the adductor policis was recorded (Relaxograph NMT-100, Datex, Helsinki, Finland). Mivacurium infusion was modified at five-minute intervals in order to keep the height of the first twitch in TOF(T1) at 5% of its control value. At the end of surgery, edrophonium (0.0, 0.125, 0.25, 0.5, or 1.0 mg x kg(-1) combined glycopyrrolate (0.0, 0.0012, 0.0025, 0.005, or 0.01 mg x kg(-1) were administered by random allocation. Edrophonium doses of 0.25, 0.5 and 1.0 mg x kg(-1) were different from placebo with regard to time to attain a TOF ratio (fourth twitch in TOF/T1) = 0.7 (13.8 +/- 4.5, 11.1 +/- 3.5, 11.4 +/- 3.0 vs 19.7 +/- 4.7 min P< 0.05). Doses of 0.5 and 1.0 mg x kg(-1) permitted faster recovery time of T1 from 10 to 95% (T10-95) than did placebo (7.5 +/- 3.8, 8.9 +/- 3.5 vs 14.5 +/- 5.0 min P<0.05). Edrophonium 0.5 mg x kg(-1) was different from placebo with regard to recovery time of T1 from 25 to 75% (T25-75) (3.3 +/- 2.0 vs 6.7 +/- 2.0 min P<0.05). Only edrophonium 0.5 mg x kg(-1) provided faster recovery than placebo with regard to all three indices. It is concluded that edrophonium 0.5 + glycopyrrolate 0.005 mg x kg(-1) allow the fastest recovery from a mivacurium-induced block during enflurane-N2O anaesthesia.

Vaccine-induced protection of chimpanzees against infection by a heterologous human immunodeficiency virus type 1

The extraordinary genetic diversity of human immunodeficiency virus type 1 (HIV-1) is a major problem to overcome in the development of an effective vaccine. In the most reliable animal model of HIV-1 infection, chimpanzees were immunized with various combinations of HIV-1 antigens, which were derived primarily from the surface glycoprotein, gp160, of HIV-1 strains LAI and MN. The immunogens also included a live recombinant canarypox virus expressing a gp160-MN protein. In one experiment, two chimpanzees were immunized multiple times; one animal received antigens derived only from HIV-1LAI, and the second animal received antigens from both HIV-1LAI and HIV-1MN. In another experiment, four chimpanzees were immunized in parallel a total of five times over 18 months; two animals received purified gp160 and V3-MN peptides, whereas the other two animals received the recombinant canarypox virus and gp160. At 3 months after the final booster, all immunized and naive control chimpanzees were challenged by intravenous inoculation of HIV-1SF2; therefore, the study represented an intrasubtype B heterologous virus challenge. Virologic and serologic follow-up showed that the controls and the two chimpanzees immunized with the live recombinant canarypox virus became infected, whereas the other animals that were immunized with gp160 and V3-MN peptides were protected from infection. Evaluation of both cellular and humoral HIV-specific immune responses at the time of infectious HIV-1 challenge identified the following as possible correlates of protection: antibody titers to the V3 loop of MN and neutralizing antibody titers to HIV-1MN or HIV-1LAI, but not to HIV-1SF2. The results of this study indicate that vaccine-mediated protection against intravenous infection with heterologous HIV-1 strains of the same subtype is possible with some immunogens.

Picornavirus internal ribosome entry segments: comparison of translation efficiency and the requirements for optimal internal initiation of translation in vitro

On the basis of primary sequence comparisons and secondary structure predictions, picornavirus internal ribosome entry segments (IRESes) have been divided into three groups (entero- and rhinoviruses; cardio- and and aphthoviruses; and hepatitis A virus). Here, we describe a detailed comparison of the ability of IRESes from each group to direct internal initiation of translation in vitro using a single dicistronic mRNA (the only variable being the IRES inserted into the dicistronic region). We studied the influence of various parameters on the capacity of six different picornaviral IRESes, and the non-picornaviral hepatitis C virus IRES, to direct internal initiation of translation: salt concentration, the addition of HeLa cell proteins to rabbit reticulocyte lysate translation reactions, the presence of foot-and-mouth disease virus Lb or human rhinovirus 2A proteinase. On the basis of the characteristics of IRES-driven translation in vitro, the picornaviral IRESes can be classified in a similar manner to when sequence homologies are considered. IRESes from each of the three groups responded differently to all of the parameters tested, indicating that while all of these elements can direct internal ribosome entry, the functional requirements for efficient IRES activity vary dramatically. In the individual optimal conditions for translation initiation, the best IRESes were those from the cardio- and aphthoviruses, followed by those from the enteroviruses, which exhibited up to 70% of the efficiency of the EMCV element in directing internal initiation of translation.

Purification and renaturation of Japanese encephalitis virus nonstructural glycoprotein NS1 overproduced by insect cells

The nonstructural protein NS1 of Japanese encephalitis virus is a major immunogen produced during flavivirus infection. However, the function of this protein has not been identified. To analyze its biochemical properties and evaluate its potential activity in the virus life cycle, the protein was produced in Spodoptera frugiperda insect cells (Sf9), using a recombinant baculovirus, and purified. As described previously by M. Flamand, V. Deubel, and M. Girard (1992, Virology 191, 826-836), a small fraction of the synthesized recombinant protein could mature into a dimer, whereas the major part was retained in intracellular aggregates. This insolubility was used to recover the protein in a purified form using a two-step procedure. Isolated inclusion bodies, in which NS1 constituted over 60% of the protein, were solubilized in 8 M urea. NS1 was further purified by reverse-phase HPLC and recovered at over 90% purity with an overall yield of over 60%. Conditions promoting reoxidation-renaturation of the purified protein were then investigated at a concentration of 100 micrograms/ml at pH 8. The presence of 8 M urea during reoxidation of NS1 with oxidized glutathione was essential prior to renaturation by dialysis to avoid reaggregation, the main side pathway of refolding in vitro. Three major species, all monomeric, were resolved by nonreducing SDS-PAGE. The form showing the lowest apparent molecular weight comigrated with native unreduced NS1 and was recognized by a monoclonal antibody directed against a conformational epitope strictly dependent on the native structure of the protein.(ABSTRACT TRUNCATED AT 250 WORDS)

[Vaccination against the human immunodeficiency virus]

Much progress has been made in recent years in the development of anti-VIH vaccines. Nearly 20 such vaccines have reached phase 1 clinical study in seronegative volunteers. The responses invoked by these vaccines are, however, mediocre, both in quality (lack of cross over neutralisation in isolated "wild" viruses) and in their levels and length of action. New formulations of vaccines are under study, but their development is long and difficult, and researchers are still disarmed by the problem of the variability of the virus. Several years of study, both clinical and fundamental, will be necessary before an effective vaccine against HIV-1 is available.

Attenuated Mengo virus: a new vector for live recombinant vaccines

Several features make Mengo virus an excellent candidate for use as a vaccine vector. The virus has a wide host range, including rodents, pigs, monkeys, and most likely humans, and expresses its genome exclusively in the cytoplasm of the infected cell. Stable attenuated strains exist which are deleted for part of the 5' noncoding region of the genome. Here we report an attenuated Mengo virus recombinant, vLCMG4, that encodes an immunodominant cytotoxic T-lymphocyte epitope of the lymphocytic choriomeningitis virus (LCMV) nucleo-protein. vLCMG4 induced protective immunity against lethal LCMV infection after a single, low-dose immunization in BALB/c mice and elicited an LCMV-specific CD8+ cytotoxic T lymphocyte response. This demonstrates the potential of recombinant Mengo virus vaccines to confer protection against infectious diseases by the induction of cellular immune responses.