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.

Disinfection of human enteric viruses on fomites.

The virucidal action of several commercially available disinfectant preparations was assayed against hepatitis A virus and human rotavirus dried on polystyrene. Overall, the level of virus disinfection achieved was very poor, usually inducing less than 3 log titre reduction. Suspension tests performed with the same disinfectants showed different virus inactivation rates, thus failing to provide a reliable indication of the actual virus disinfection on fomites. In our studies, bacteriophages of Bacteroides fragilis proved to be a simple, cheap and reliable screening tool for the evaluation of virus disinfection on non-porous surfaces. The same conclusion cannot be drawn for poliovirus.

Propagation and assay of hepatitis A virus in vitro.

Ten strains of hepatitis A virus (HAV) originating from far distant geographical locations were adapted to growth in PLC/PRF/5 (human hepatoma derived and/or MRC-5 (human embryonic lung) cells. In the course of primary adaptation some of these strains exhibited a predilection for distinct cultural conditions such as type of host cell and temperature of incubation. With progressive passage, variant viruses with quite different requirements could be selected; yet, it proved impossible to isolate a virus which replicated equally well in both types of cells and at both 32 and 37 degrees C without at least one preceding passage under the new conditions. Analysis of the virus/cell relationship of well adapted HAV strains revealed that the replication cycle of HAV extends over about 24 h. Moreover, replication evidently passes from a state of active production of infectious virus to a phase during which hepatitis A antigen (HAAg) is synthesized and terminates in the state of persistent infection with markedly reduced synthetic activity. In all three phases replication of HAV is non-cytolytic and the vast majority of both infectious virus and of HAAg remains cell associated. The observations concerning the growth characteristics of HAV were used to develop two rapid in vitro assay systems for HAV infectivity (fluorescent focus assay and in situ RIA). Finally, the conditions for large scale production of infectious HAV and of HAAg in a cell factory system were analysed.

Recovery and detection of enterovirus, hepatitis A virus and Norwalk virus in hardshell clams (Mercenaria mercenaria) by RT-PCR methods.

A method for recovery of enteric viruses from hardshell clams (Mercenaria mercenaria) has been developed and evaluated. Seeded 50-g samples of clam tissue homogenates were processed by adsorption elution precipitation, two fluorocarbon extractions and PEG precipitation. Clam concentrates were assayed by infectivity and by RT-PCR after guanidinium isothiocyanate (GIT) extraction and/or an indirect immunomagnetic capture (IC) of the virus using paramagnetic beads. GIT extraction removed PCR inhibitors and allowed a reliable RT-PCR detection of viral RNA. The detection sensitivity of GIT extraction-RT-PCR was < 1 PFU of poliovirus 1, < 10 PFU of HAV and 1-11 PCRU of Norwalk virus. IC was very effective for additional concentration and purification of enteric viruses from clam concentrates removing most RT-PCR inhibitors. The sensitivity of this method was comparable to the GIT extraction and the sample volume tolerance for PCR was increased about 10-fold. Both methods gave similar efficiency for virus detection in samples seeded with low virus levels. The procedure developed in this study is effective for enteric viruses detection in hardshell clams by RT-PCR.

Enterically transmitted hepatitis. Hepatitis A and E viruses.

Enterically-transmitted hepatitis is caused by hepatitis A virus and hepatitis E virus. The most important agent is hepatitis A virus, which is distributed worldwide and infects all age groups. Most infections in children are minimally symptomatic and immunity is long-lasting, so severe disease tends to occur in nonimmune adults. Hepatitis E virus is found in the developing world and has a greater propensity for symptomatic infection of children. Both agents are transmitted via contaminated water, often through food vehicles.

Review of infectivity studies in nonhuman primates with virus-like particles associated with MS-1 hepatitis.

Using the technique of immune electron microscopy we have conducted hepatitis A infectivity studies in marmoset monkeys and chimpanzees. Marmosets inoculated with human serum containing the MS-1 strain of hepatitis A virus have developed hepatitis and seroconverted to 27 nm virus-like particles isolated from stools of humans in the early acute stages of hepatitis. Similar results have been observed through several marmoset subpassages, and the virus-like particles have been recovered from the liver of animals in the acute phase of hepatitis. Chimpanzees inoculated with stool filtrates containing the virus-like particles develop hepatitis with concomitant excretion of the particles in early acute phase stools and subsequent development of serum antibody to the particles. These studies provide evidence that the above particles constitute the virus of hepatitis A of the MS-1 prototype.

Avoiding biohazards in medical, veterinary and research laboratories.

Personnel in medical, veterinary or research laboratories may be exposed to a wide variety of pathogens that range from deadly to debilitating. For some of these pathogens, no treatment is available, and in other cases the treatment does not fully control the disease. It is important that personnel in laboratories that process human or microbiological specimens follow universal precautions when handling tissues, cells, or microbiological specimens owing to the increasing numbers of individuals infected with hepatitis C and HIV in the US and the possibility that an individual may be asymptomatic when a specimen is obtained. Similar precautions must be followed in laboratories that use animal tissues owing to the possibility of exposure to agents that are pathogenic in humans. Personnel with conditions associated with immunosuppression should evaluate carefully whether or not specific laboratory environments put them at increased risk of disease. We offer here some general approaches to identifying biohazards and to minimizing the potential risk of exposure. The issues discussed can be used to develop a general safety program as required by regulatory or accrediting agencies, including the Occupational Safety and Health Administration.

[Viral hepatitis of enteric origin]. / Les hépatites virales d'origine entérique.

Hepatitis viruses of oral-fecal origin are responsible for a high morbidity and mortality throughout the world, even if they never result in chronic hepatitis. Two viruses, the virus of hepatitis A (VHA) and of hepatitis E (VHE) are at present the cause of severe viral hepatitis of enteric origin. Water is the principle vector in the spread of these viruses. However, the epidemiological aspects vary according to the pathogenic agent. VHA is excreted in a highly concentrated form in the feces for a relatively short period of time. Since it resists in an exterior environment, the virus remains infectious for a long time. VHE is excreted for a short period of time and in low concentrations. The viral particles are fragile in vitro and their variability in the environment is little known. The possible reservoir role of certain animals has been envisaged. Epidemics arise especially in countries suffering from poor hygiene and massive water pollution. Hepatitis A should no longer be considered a benign disease of childhood. The progress made in hygiene and economic development in industrialized countries have made contacts with this virus scarce, rendering the populations more receptive to it and epidemics more widespread. When the sickness occurs later in life, infection is more often symptomatic and can be serious, resulting sometimes long-term indisposition. Hepatitis E has a vast distribution throughout the world and manifests itself either in epidemic or endemic-sporadic form in many poor countries. In developed countries, it comes about mostly as a result of imported pathology, even if there exists a "substratum" of infection in these areas. The main clinical aspects, such as we were able to study them in 39 cases of military men from Tchad, Guyana and Somalia, are comparable to those of hepatitis A. The reasons for the particular gravity of symptoms in pregnant women are unknown. These affections have no specific treatment. In the field of prevention, vaccination is at present the best means for hepatitis A prophylaxis. Until a vaccine against hepatitis E is found, prevention depends on hygiene, sanitation measures et distribution of drinking water.

[Adaptation of hepatitis A virus strain (JaM-55) originally pathogenic for monkeys to a cell culture]. / Adaptatsiia shtamma virusa gepatita A (IaM-55), iskhodno patogennogo dlia obez'ian, k kletochnoi kul'ture.

The results of adaptation of hepatitis A viral strain JaM-55 to the culture of embryo kidney cells FRhk-4 from macaque Rhesus are presented. The viral strain was isolated from a M. fascicularis suffering from spontaneous hepatitis. Before inoculating the cell culture the virus was passaged twice in the M. arctoides capable of reproducing hepatitis. FRhk-4 cell line inoculation by the monkey liver extract, containing the strain HAV-YaM-55, resulted in isolation of single viral particles of hepatitis A in the preparations obtained at the first 3 passages by the 28-31 day of cultivation. Beginning from the fourth passage the abrupt increase in the number of viral particles and hepatitis A antigen was registered. There were no traces of cytopathogenic effect at any level of viral passages in the inoculated cell culture. The adapted virus contains hepatitis A viral RNA identified by spot hybridization with the cloned cDNA of hepatitis A virus.

Electron microscopy of buffalo green monkey kidney cells persistently infected with hepatitis A virus and immunolocalization of HAV antigens.

Studies were carried out to analyse the ultrastructural changes and the distribution of hepatitis A virus (HAV)/antigens at subcellular level in buffalo green monkey kidney (BGMK) cells persistently infected with HM-175 strain of HAV. HAV infected BGMK cells showed distinct abnormalities in the endoplasmic reticulum and cytoplasmic membrane as compared to uninfected cells. The abnormalities were characterized by wavy arrays, structures like myelin, annulate lamellae, cytoplasmic inclusion bodies and vesicles. The wavy arrays within the cytoplasm of the host cells appeared to represent degenerating membranes. A complex myelin like body was found in close association with a group of virus like particles. Annulate lamellae like structures involving single paired membrane were detected infrequently whereas the cytoplasmic vesicles were numerous in these cells. An indirect immunogold technique was utilized to localize the HAV antigenin infected cells. A high density immunogold label for HIV like particles was predominantly detected in cytoplasmic vesicles. These results suggest a strong association of membrane substructure in vesicle forms with the compartmentalized replication of HAV within persistently infected host cells.

[Preparation and characteristics of cultured strains of hepatitis A virus from humans and monkeys]. / Poluchenie i kharakteristika kul'tural'nykh shtammov virusa gepatita A ot cheloveka i obez'ian.

Cultural strains of hepatitis A virus (HAV) have been isolated from spontaneously infected Macaca mulatta (HAV-MM), Papio hamadryas (HAV-PH), African green monkeys Cercopithecus aethiops (HAV-CA), and patients (HAV-H). The strains replicate in continuous cells lines AGMK, 4647, Vero, and FRhk-4. AGMK and 4647 cells are the most permissive at 32 degrees C. Virus propagation was not associated with the cytopathic effect and could be detected by enzyme immunoassay (EIA), immune electron microscopy (IEM), and molecular hybridization method (MHM). The morphological and antigenic properties of the above monkey and human strains did not differ in EIA and IEM with polyclonal antibodies and for one most conservative genome sites in the VP1 domain. Cultural strains retained their pathogenicity for monkeys. HAV strains are proposed to be used as HAV antigen in immunological tests and for hepatitis A induction in monkeys.

[Experiment in infecting the green monkey Cercopithecus aethiops with a leukocyte virus isolated in hepatitis A]. / Opyt zarazheniia zelenykh martyshek Cercopithecus aethiops leikotsitarnym virusom, vydelennym pri gepatite A.

The virus isolated in hepatitis A had been previously shown to passage in primary phytohemagglutinin-stimulated leukocyte cultures. The virus designated as leukocyte hepatitis virus (LHV) causes chromosome aberrations in the infected cultures. Some physico-chemical properties of LHV and its capacity for reproduction in other cell systems were studied. In serological surveys of patients and in studies of cellular immunity reactions of them LHV was found in cases of hepatitis. The possibility of producing a laboratory model of hepatitis in green monkeys, morphological reaction to inoculation with LHV, as well as the presence of specific antigen in the inoculated animals by immunofluorescence test using rabbit immune serum to LHV and FITC-labelled gamma globulins from hepatitis A convalescents were investigated. LHV antigen was found in the lymph nodes, spleen and liver. Active morphological reaction of lymph nodes and spleen was observed 30 days after inoculation of monkeys. The results indicate that in green monkeys LHV possesses marked reticulotropic properties without producing clinical hepatitis, therefore African grivet monkeys (Cercopithecus aethiops), apparently, cannot be used as experimental models for LHV studies in vivo.

[Characteristics of experimental models of hepatitis A in Papio hamadryas]. / Kharakteristika éksperimental'nykh modelei gepatita A na pavianakh gamadrilakh.

Hepatitis A (HA) was induced in 14 Papio hamadryas by strain VHA-PH isolated from this species of monkeys with spontaneous infection, strain VHA-MM isolated from Macaca mulatta, and a unique strain VHA-H3 isolated from a patient; this latter strain is pathogenic for Macaca mulatta in experiment. All infected seronegative animals developed a disease with virological, serological, biochemical, and morphological signs characteristic of human HA, but the duration of these signs manifestation varied. Virus in the feces and an increased level of SGPT were detected periodically starting from days 3-26 to 24-135, and in 4 monkeys even later (up to days 163-238). Morphologic changes in the liver, typical of acute hepatitis, were observed from days 10-46 to days 16-130. Strain VHA-H3 is less pathogenic for papios. HA models on Papio hamadryas infected with strains VHA-PH and VHA-MM can help solve many research and practical problems.

[The isolation and study of the characteristics of a cytopathic strain of the hepatitis A virus]. / Vydelenie i izuchenie kharakteristik tsitopaticheskogo shtamma virusa gepatita A.

A fast-growing cytopathic isolate of human hepatitis A virus (strain MB-7) was derived from fecal samples of infected patients and adapted to growth in FRhK-4 cell culture. A positive serum standard against HAV and electron microscopy were used to demonstrate that MB-7 belonged to human hepatitis A virus. The strain MB-7 induced plaque formation in FRhK-4 under agar overlay after 10-12 days of incubation. The PCR products of gene VP1 were cloned in E. coli and its primary structure was determined. MB-7 was shown to have more homology with HAV strains isolated in the USA and China.

[Association of the hepatitis A virus with the membranes of infected cells]. / Assotsiatsiia virusa gepatita A s membranami infitsirovannykh kletok.

"Light" viral antigen (HAAg) with buoyant density 1.20 g/cm2 and sedimentation coefficient 92S are accumulated together with mature viral particles in Hepatitis A virus (HAV) infected FRhK-4 cells. This HAAg is localized predominantly in endoplasmic reticulum fraction of infected cells, while nature virions are localized in cytosol. In contrast to mature virus, "light" HAAg is sensitive to trypsin digestion and is not able to hybridize with synthetic oligodeoxinucleotide which is complementary to structural part of HAV RNA. Antigenic properties of mature virus and "light" antigen are compared.

[The modelling of hepatitis A in macaques]. / Modelirovanie gepatita A na makakakh.

Characteristics of experimental hepatitis A in Macaca fascicularis and M. mulatta produced with HAV, strain MP, isolated from M. mulatta in an outbreak of spontaneous hepatitis are presented. The HAV-MP strain induced the disease in all the animals used in the experiment. The infection was manifest, with all virological, serological, biochemical and morphological features typical of hepatitis A. In M. mulatta, the process was protracted, with virus persistence in feces for at least 4 months. Modeling of hepatitis A in Macaca monkeys using HAV-MP strain may be used for the study of the pathogenesis and trials of immune preparations.

[The sensitivity of rhesus and cynomolgus macaques to the human hepatitis A virus]. / Chuvstvitel'nost' makak rezusov i iavanskikh makak k virusu gepatita A cheloveka.

Hepatitis A infection characterized by virus excretion in feces, synthesis of specific IgM antibody, increased activity of alanine aminotransferase in the blood serum, and a complex of morphological lesions in the liver typical of acute hepatitis was reproduced in M. fascicularis (M. f.) and Macaca rhesus (M. r.) using 2 strains of hepatitis A virus (HAV) isolated from human patients. The incubation period varying from 9 to 23 (mean 16) days in M. f. and from 12 to 35 (mean 18) days in M. r. in primary infection shortened to 1-12 (mean 10) and 3-6 (mean 5) days in the process of virus passage from monkey to monkey. The disease was observed to run both manifest forms (except jaundice) typical of human HA and an inapparent form in which the level of enzymes remained within normal limits but HAV could be detected in feces, anti-HAV-IgM in the blood serum, and morphologically acute hepatitis in the liver. Immune electron microscopy of both the initial material and in monkey feces at the levels of all three passages revealed complexes consisting of spherical viral particles 27-29 nm in size coated with antibodies. The immune complexes formed upon addition to the fecal extracts under study of IgG isolated both from human convalescent sera and from sera of experimentally infected monkeys collected in the acute stage of the illness.

[Hepatitis A in Macaca fascicularis and M. arctoides infected by the Java monkey-55 strain of hepatitis A virus]. / Gepatit A u iavanskikh i burykh makak pri ikh zarazhenii shtammom virusa gepatita A IaM-55.

The results are presented dealing with experimental inoculation of M. fascicularis and M. arctoides with a strain of hepatitis A virus (HAV), YaM-55, isolated from a M. fascicularis with spontaneous hepatitis A, and parallel experiments on inoculation of these monkey species with HAV preparations (strain HAS-15) obtained as a result of the strain propagation in FRhK-4 cell culture and with specimens from human hepatitis A patients containing HAV particles. The YaM-55 strain of HAV was found to be capable of producing an infectious process quite similar to HA in the inoculated seronegative M. fascicularis and M. arctoides. Two different isolates of HAV derived from humans and the HAS-15 strain of HAV propagated for a long time in FRhK-4 cell culture failed to induce a disease in these monkey species. The classification of the YaM-55 strain with HAV was verified by specific serological studies and by molecular hybridization with cloned cDNA of HAV.

[The chronic course of spontaneous and experimental hepatitis A in rhesus monkeys with viral persistence]. / Khronicheskoe techenie spontannogo i éksperimental'nogo gepatita A u makak rezusov s persistentsiei virusa.

The prolonged (up to 2 years) complex observation of 11 rhesus macaques (Macaca mulatta) with spontaneous hepatitis A and 14 rhesus macaques with experimental hepatitis A developing after their intravenous and/or oral infection with human hepatitis A virus (HAV). Both natural and experimental infection took a chronic course (15-18 months). In 13 monkeys showing morphological changes in the liver during the whole period of the disease elevated enzyme levels in the blood and virus shedding in feces were periodically observed. Only one monkey had acute hepatitis A which lasted 1.5 months. In 11 monkeys the disease took an undulating course with 1-2 relapses when virological, biochemical and morphological signs of the disease could be detected. Seroconversion was observed in all monkeys. Anti-HAV IgM antibodies were retained for not more than 6-7 months and total anti-HAV antibodies, during the whole period of observation. Relapses were found to induce no antibody formation. Evidence on the prolonged (up to 12-16 months) persistence of HAV in primates was obtained for the first time.

[Experimental models of hepatitis A in macaques using viral strains isolated from man and monkeys]. / Eksperimental'nye modeli gepatita A na makakakh s ispol'zovaniem shtammov virusov, vydelennykh ot cheloveka i obez'ian.

Experimental hepatitis A (HA) models were obtained in macaca monkeys (15 M. fascicularis and 4 M. mulatta) by means of the strains of hepatitis A virus (HAV) isolated from the feces of a patient (HAV-H) and of spontaneously infected M. Mulatta (HAV-MM) and green monkeys Cercopithecus aethiops (HAV-CA). Irrespective of the strains used all seronegative macaca monkeys developed HA after intravenous-oral inoculation with the following patterns: elevation of the serum alanine aminotransferase level, HAV shedding in feces, seroconversion with the appearance of anti-HAV IgM and morphological changes in the liver characteristic of acute hepatitis. HAV in fecal samples and elevation of alanine aminotransferase were periodically detected. Periods of their discovery varied from 5-22 to 15-47 days and those of morphological changes in the liver from 9-24 to 40-83 days. The results of the experiments show that experimental HA models in Macaca monkeys are no less adequate than the previous ones developed in chimpanzees (Pan troglodytes), marmosets (Saguinus mystax) and owl monkeys (Aotus trivirgatus), but they are more readily available. Both strain HAV-H and strains from monkeys can be used for HA modelling. The models are expected to be used for studying yet unsolved problems of pathogenesis and immunogenesis, as well as for testing vaccines and antiviral drugs.