Antiviral activity of recombinant interferon-alpha on hepatitis A virus replication in human liver cells.

Human recombinant interferon-alpha (IFN-alpha) was assayed for its antiviral effect on hepatitis A virus (HAV) replication in the human hepatoma cell line PLC/PRF/5. IFN-alpha resulted in concentration-dependent reduction of HAV antigen expression and HAV replication. IFN-alpha had a prophylactic effect, but was still effective when it was added after the infection, even at the end of the first replication cycle. An important increase in 2',5'-oligoadenylate synthetase activity in the IFN-treated human liver cells was observed. The antiviral effect of IFN-alpha could be attributed to the induction of this enzyme. Moreover we have shown that IFN-alpha and glycyrrhizin were synergistic in their antiviral actions against HAV. IFN-alpha emerged, from the present study, as a promising candidate for chemotherapy of severe forms of hepatitis A.

Studies on mechanism of action of glycyrrhizin against hepatitis A virus replication in vitro.

Glycyrrhizin (GL) achieved a concentration-dependent inhibition of the replication of hepatitis A virus (HAV) in PLC/PRF/5 cells. GL has been shown to inhibit an early stage of the HAV replication. GL was not virucidal and had no measurable effect on the adsorption of [3H]uridine-labelled virions to cells. GL inhibited HAV penetration of the plasma membrane as measured by the amount of infective virus no longer neutralizable by specific antibody over time.

Short report: polymerase chain reaction detection of hepatitis E virus in north African fecal samples.

Epidemics of enterically-transmitted non-A, non-B hepatitis were described in 1983-1984 involving French soldiers in Chad and in 1979-1980 in residents of Algeria. Hepatitis E virus (HEV) was subsequently implicated by serology. In this study, the presence of HEV in patient stool specimens from both outbreaks and from sporadic cases in residents of Chad (1994) was documented. This virus was detected in fecal suspensions by antibody capture of the virus and reverse transcriptase-polymerase chain reaction amplification of the viral RNA in the 3' end of open reading frame 2. Two of five epidemic cases from Chad (1983-1984) were positive, as well as one of five sporadic cases from Chad (1994), and two of three epidemic cases from Algeria (1979-1980). Of these 13 patients, 12 had detectable anti-HEV IgG in their serum. These results confirmed that HEV was the cause of hepatitis in at least five of these 13 patients.

Continuous production of hepatitis A virus in PLC/PRF/5 cell cultures: use of antigen for serology.

The strain CF53 of hepatitis A virus (HAV) previously adapted to growth in PLC/PRF/5 cells was grown in 175 cm2 flasks, at different passages. After infection, cells were incubated at 32 degrees C in RPMI 1640 medium supplemented with 2.5% foetal calf serum (FCS) for 6-12 months. HAV which was released continuously in the culture medium was harvested weekly. Hepatitis A virus antigen (HAAg) and infectious virus production was stable during each passage. The antigen titre, determined by radioimmunoassay, was about 50 for each passage whereas the infectious virus titre increased from 10(3.7) (passage 7) to 10(6.0) TCID50/ml (passage 13). Virus production was not influenced by the FCS concentration (0-2.5%) in the maintenance medium. The cell culture produced HAAg was used for detection of total anti-HAV antibodies, anti-HAV titration and IgM antibody capture assay and the results were identical to those obtained with commercial kits. HAAg produced by this practical and cheap method could easily replace primate derived antigen for the detection of anti-HAV antibodies.

Effect of glutaraldehyde on the antigenicity and infectivity of hepatitis A virus.

The effect of glutaraldehyde on the antigenicity and infectivity of hepatitis A virus (HAV) was examined. The CF 53 strain, adapted to human hepatoma PLC/PRF/5 cells, was treated with glutaraldehyde using three different concentrations, 0.02, 0.10, and 0.50%, for various periods of time, 3, 10, and 30 min, respectively. After the virucidal assays, glutaraldehyde and HAV were separated by gel filtration, then the antigen (radioimmunoassay) titer and the infectivity titer were determined. The greatest antigen titer reduction was about 80% after 30 min using 0.10% glutaraldehyde and within only 3 min using 0.50% glutaraldehyde. Glutaraldehyde is an effective disinfectant against HAV: the infectious virus titer decreased by more than 3 log10 after 30 min using 0.10% glutaraldehyde and within only 3 min using 0.50% glutaraldehyde. Statistical studies showed that the decrease of antigen or infectious virus titer was affected by both glutaraldehyde concentration and exposure time.

Changes in ecto-5'-nucleotidase activity during early stages of vesicular stomatitis virus infection. Effects of concanavalin A.

Study of ecto-5'-nucleotidase was performed in cultured epithelial cells, infected with vesicular stomatitis virus (VSV). Changes in the enzymatic activity were measured in terms of TCID50 and exposure time. The effects of an enzyme inhibitor, Con A, were also investigated during the interaction between virus and cells.

[Water and viral hepatitis]. / L'eau et les hépatites virales.

The main agents responsible for acute viral hepatitis throughout the world are the hepatitis A virus (HAV) and the hepatitis E virus (HEV). Both are transmitted by fecal-oral route and can provoke large epidemics, HAV in developed countries and HEV in developing countries. Water is a major vehicle of spread. However, two different epidemiological patterns have to be distinguished: level of HAV excretion is short but high. Because of its resistance to physical and chemical agents, HAV remains infectious for a long time under environmental conditions. Progress in hygiene have nearly stopped the circulation of HAV in industrialized countries, making populations more susceptible to the infection and increasing the epidemic risk. Conventional measures sometimes fail to prevent HAV infections. Vaccine is currently the best way for hepatitis A prophylaxis; HEV is excreted briefly and at low concentrations. Viral particles are fragile in vitro and their viability in environment is not yet understood. Epidemics mainly occur in countries with poor sanitary conditions, resulting from heavy water pollutions. High case-fatality rates are observed, especially among pregnant women. The control of enterically transmitted viral hepatitis remains a major public health challenge. Virological surveillance of waste water could improve strategies based on hygiene, sanitation and supply of drinking water.

[Purification of hepatitis A virus from human feces]. / Purification du virus de l'hépatite A à partir de fèces d'origine humaine.

Hepatitis A virus was purified from on early acute phase human stool by a procedure using 10% polyethylene glycol precipitation, sepharose 2B gel filtration, isopycnic banding in cesium chloride, rate zonal separation in sucrose - 99,5% of the 280 nm absorbing fecal impurities were removed.

Effect of antiviral substances on hepatitis A virus replication in vitro.

The effect of protamine, atropine, selenocystamine, taxifolin, and catechin on the infectivity and antigenicity of the cell culture-adapted hepatitis A virus (HAV) strain CF 53 was studied. The toxicity on uninfected PLC/PRF/5 cells was examined for each antiviral compound by morphological and biochemical methods, in order to determine concentrations without cytotoxic effect. At these concentrations, protamine and taxifolin, added to infected cells for a 15-day period, caused concentration-dependent reductions in the infectivity and antigenicity of HAV. Atropine also caused a concentration-dependent reduction of HAV infectivity but did not affect the antigenicity of the virus. At the highest concentration used, 50 micrograms/ml of protamine, 59 micrograms/ml of taxifolin, and 50 micrograms/ml of atropine, the infectious viral titer reduction was 1.56, 0.77, and 0.68 log10, respectively. Selenocystamine and catechin had no effect on HAV replication.

Long-term survival of hepatitis A virus and poliovirus type 1 in mineral water.

The survival in mineral water of hepatitis A virus (HAV) and poliovirus type 1 was compared, under controlled experimental conditions, at 4 degrees C and room temperature. Viral infectivity titers were determined by cell culture titration, while HAV antigenicity was monitored by radioimmunoassay-endpoint titration. Both viruses persisted longest at 4 degrees C. At this temperature, after 1 year of exposure, the inactivation of either HAV or poliovirus type 1 was not important. At room temperature, poliovirus type 1 was not detected after 300 days, whereas HAV was still infectious. For both temperatures, the computed regression coefficients of best-fit lines for inactivation rates for the two viruses were significantly different. The survival of HAV was also studied at 4 degrees C and room temperature in mineral water with 5- and 50-micrograms/ml protein concentrations (i.e., purity of the virus suspension) for 120 days. As shown by a comparison of the regression coefficients for the inactivation rates, the stability of HAV in mineral water depends on protein concentration and temperature. Radioimmunoassay-endpoint titration results showed inactivation patterns similar to those of cell culture titration, with the most significant reduction in HAV antigenicity at room temperature. At the two temperatures, the infectivity of HAV declined at a faster rate than the antigenicity.

[Early effect of poliomyelitis virus on 5'-nucleotidase activity in HeLa cells]. / Action précoce du virus poliomyélitique sur l'activité 5'-nucléotidase des cellules HeLa.

One of the earlier effects of poliovirus was the maintaining of a high level of Hela cells 5'-nucleotidase activity (maximal efficiency for a virus/cell ratio = 500 ID 50/cell) (ID50:50% Infections Dose). The activity decreased when cells were suspended in the presence of EDTA(EDTA:Ethylene Diamine Tetracetic Acid) and was partially restored by adding 10 mM Mg++ interactions are discussed.

Inhibitory effects of atropine, protamine, and their combination on hepatitis A virus replication in PLC/PRF/5 cells.

Atropine, protamine, and the combination of these drugs were tested for their effects on hepatitis A virus (HAV) replication in cell culture. PLC/PRF/5 hepatoma cells were treated simultaneously with nontoxic concentrations of these drugs and inoculated with HAV strain CF 53 at several multiplicities of infection. The yields of infectious HAV after 4 and 15 days were markedly reduced by each drug, especially at the lowest multiplicity of infection. The activities of each drug were irreversible. Atropine was active when it was added as late as 2 h after inoculation with HAV. An anti-HAV effect was also induced by treating cells with atropine prior to inoculation. Protamine was active as late as 6 h postinoculation. The combination of atropine and protamine resulted in an enhanced anti-HAV effect. We concluded that these drugs affect undetermined, but separate, steps in the HAV replication cycle.

[Antiviral effect of recombinant interferon-alpha on hepatitis A virus replication in human liver cells]. / Effet antiviral de l'interféron-alpha recombinant sur la multiplication du virus de l'hépatite A dans des cellules hépatiques humaines.

Two recombinant interferons-alpha (IFNs-alpha) were assayed for their antiviral effect on hepatitis A virus (HAV) replication in the human hepatoma cell line PLC/PRF/5. IFN alpha-2a and IFN alpha-2b resulted in concentration-dependent inhibition of HAV antigen expression and HAV infectivity at non toxic concentrations. Their selectivity indices, calculated as the ratio of the dose that reduced the number of viable cells to 50% (CD50) to the effective dose that inhibited 50% of viral antigen expression (ED50) were > 1000. Recombinant IFN-alpha emerged, from the present study, as a promising candidate for chemotherapy of hepatitis A.

Evolution of hepatitis A antibodies prevalence in young French military recruits.

Hepatitis A antibodies (anti-HAV) were surveyed in 1000 French recruits during 1990. The prevalence of anti-HAV in this group was 21.35%. Compared to a 1985 survey a 9% fall in the anti-HAV prevalence rate was observed. Living in a coastal area, low educational level, stay overseas were the main risk factors, as already noted in 1985.

[Ciguatera: neurophysiologic and histoenzymologic studies of several fractions of ciguatoxic extracts]. / Ciguatera: études neurophysiologique et histoenzymologique de diverses fractions d'extraits ciguatoxiques

Two fractions of ciguatoxic extracts were isolated by chromatography. The first showed anticholinesterasic properties, while the other acted directly on the muscular fibre. These findings were histoenzymologically confirmed. Controls with non-toxic extracts of fishes from the coral benthos reinforce the theory of the ecological origins of ciguatoxins.

[Release of hepatitis A virus into the culture medium, during its replication in PLC/PRF/5 cells]. / Libération du virus de l'hépatite A dans le milieu de culture, lors de sa réplication dans des cellules PLC/PRF/5.

Hepatitis A virus (HAV), obtained from human feces collected 3 days after the onset of jaundice, was propagated in human hepatocarcinoma cells (PLC/PRF/5). In the course of 5 passages, it was released into the supernatant without cytopathic effect. Released HAV was propagated after inoculation into PLC/PRF/5 cells. Its biophysical properties (buoyant density in CsCl: 1, 33 g/cm3; sedimentation coefficient: 155 S) were similar to those of the infectious particle present in the cells or in the stools of patients.

[Kinetic study of membrane 5'-nucleotidase activity in cultured diploid cells]. / Etude cinétique de l'activité 5'-nucléotidase membranaire de cellules diploïdes en culture.

5'-nucleotidase activity of cultured diploïd cells was measured using intact suspended cells. This depended on the substrate amount, but did not vary with Mg ++ concentration-Kinetic data were determined using Con. A,a specific inhibitor.

Research of enterovirus, hepatitis A virus in a bathing area over a six month period and their salubrity impact.

Cell-culturable enterovirus and HAV levels in the effluent of a treatment plant were compared with those near the effluent outfall and in a neighbouring bathing area over a period of six months. Enteroviruses were found in all effluent samples, whereas only three contained HAV. No viruses were detected near the outfall nor in the bathing area. Despite the low impact of this scenario on human health, the view is expressed that the potential risk posed by the discharge of viruses from treatment plants must not be underestimated, since there is ample evidence that HAV can be epidemiologically transmitted via the consumption of shellfish.

[The effect of a mixture of bacterial ribosomes and membrane fractions of Klebsiella pneumoniae on the development of a transplanted epithelial cancer in rats]. / Effet d'un mélange de ribosomes bactériens et d'une fraction membranaire de Klebsiella pneumoniae sur le développement d'un cancer épithélial greffé chez le rat.

An association of bacterial ribosomes and cell-wall of Klebsiella pneumoniae was shown to reduce the incidence of an epidermoid carcinoma in Sprague-Dawley rats when administered subcutaneously prior the tumoral graft. Mononuclear cells accumulate around the tumor. This association was considered as a non specific adjuvant stimulating the host's intrinsic immunity to tumor antigens.