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Experimental infection of piglets with a fecal pool containing hepatitis E virus (HEV) strains Osh-25 and Osh-228 confirmed previous results obtained with HEV strain Osh-205 on susceptibility of these animals to hepatitis E. A biphasic increase of transaminase activities, histopathologic changes in the liver, virus excretion with feces were observed in the animals. The genome of viral particles in piglet feces conformed, at least partially, to human HEV RNA. Ultrastructural abnormalities of piglet hepatocytes resembled those in primates with experimental hepatitis E. The number of positive results (during follow-up of the particles and HEV RNA in various organs of experimental animals) was the highest on day 10 after infection. Both the particles and HEV RNA were present in the lymphoid tissue over the entire follow-up period, from day 5 to day 15 postinfection.

Lambs were experimentally infected with a pool of 10% hepatitis E (HE) patient fecal suspension containing HE virus (HEV) isolates Osh-225 and Osh-228 which caused an infection closely resembling experimental HE in primates. Clinical manifestations consisted of acute biochemical and histological hepatitis, virus shedding in feces, the presence of virus-like particles in the peripharyngeal lymph nodes and the contents of small intestine, of HEV RNA in the parenchymal organs of lambs. Susceptibility of lambs to HEV derived from the infected piglets and the possibility of passaging the piglets' HEV in lambs was demonstrated. This passaging led to shortening of the incubation period.

Bound chlorine in doses 0.8-1.2 mg/l does not inactivate viruses in water. Chlorine can be active against hepatitis A viruses in concentration not less than 4.2 mg/l with the virion content in water 10(5)/ml and at least 20 min exposure.

A trial of inactivated hepatitis A viral vaccine of heteroploid cell culture origin is described. The vaccine preparation was tested in guinea pigs and tamarins. The animals were immunized intramuscularly four or three times, respectively. The efficacy was judged by induction of anti-HAV antibody persisting for at least 12 months in guinea pigs, and development of immunity to subsequent virus challenge (monkeys only). The challenge dose of HAV was unable to produce any signs of HAV infection in the vaccinated tamarins, although the booster effect was observed in some animals. The study demonstrated that the tested batches of the vaccine were highly immunogenic.

A modified enzyme immunoassay based on adsorption of antihepatitis A virus (HAV) IgG-HRPO conjugate and monoclonal antibodies to HAV were used to investigate antigenic differences between mature HAV virions and subviral particles with different buoyant densities in CsCl produced in HAV-infected cells. The mature virions (1.34 g/cm3) appeared to have common antigenic determinants with subviral particles (1.20, 1.27, and 1.30 g/cm3) and possess some additional determinants. Nevertheless, both subviral particles and mature virions induced antibodies capable of neutralizing HAV infectivity in tissue culture.

Peptide (P6) representing amino acids 62-75 of HAV capsid protein VP3 was synthesized. Pure P6, octamer form of P6, and P6 conjugated to KLH were injected into rabbits. The sera against these preparations reacted with denaturized VP3 in immunoblotting tests; however, only anti-P6-KLH serum was capable of binding the native HAV.

The Western blot procedure with highly specific antipeptide antibody was applied to identify the electrophoretic mobility of hepatitis A virus capsid proteins. Polypeptides with molecular weights of 33, 29 and 27 kDa proved to be VP1, VP2, and VP3 proteins as they reacted with sera generated to VP1 recombinant protein and to synthetic oligopeptides 42-62 VP2 and 62-75 VP3, respectively.

A modified technique of protein staining with silver nitrate was employed in electrophoretic analysis of hepatitis A virus structural proteins. The modifications of the original technique, i.e. thorough washing of the gel, increased formaldehyde concentration and a more intensive lighting of the gel, have elevated the method sensitivity 10-fold permitting the detection of up to 0.1 ng protein. The modification has allowed detection of VP1, VP2, and VP3 structural proteins with molecular masses 33, 29, and 27 kD, respectively, in virus preparations of low concentrations.

Hepatitis A virus (HAV) was propagated in continuous rhesus monkey embryo kidney cells (FRhK-4 line). HAV RNA extracted with phenol from purified HAV pretreated with proteinase K was used for molecular cloning experiments. Two radioactive plasmids, pHAV-23 and pHAV-5p, containing HAV cDNA fragments complementary to structural and nonstructural parts of HAV genome, respectively, were found to be useful for discrimination between mature virions and subviral structures. HAV cDNA-RNA hybridization seems to be 10 times more sensitive than the enzyme immunoassay (ELISA).

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.

In an analysis of sporadic cases of gastroenteritis in children, rotaviruses were detected in 61 out of 363 specimens examined. Studies of rotavirus isolates by polyacrylamide gel electrophoresis (EP) of RNA revealed 9 different EP types. In one region, during the entire epidemic season one "long" EP type was prevalent. In one patient, a mixture of a "short" and "long" EP types was detected. In another region, "atypical" rotaviruses were found not belonging to the antigenic group A of rotaviruses.

The interaction between labelled polynucleotides and the mitochondrial membrane was studied. It was shown that DNA and mRNA form a complex with the mitochondria and mitoplasts (i. e. mitochondria devoid of the outer membrane); this process does not depend on the energy state of mitochondria. Within the complex polynucleotides are accessible to the effects of nucleases. The complex formation strongly depends on the concentration of Mg2+ and is inhibited by Na+. It was found that polynucleotides are effectively bound to protein-free artificial membranes isolated from the total mitochondrial lipids. The data obtained suggest that in the presence of Mg2+ polynucleotides form a complex with the lipid components of the mitochondrial membrane.

"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 propagation time-course of hepatitis A virus (HAV, strain HAS-15) in continuous culture of the foetal rhesus monkey kidney cells (FRhK-4) was investigated. The HAV infectivity and viral RNA content in the infected cells reached the maximal level 5-8 days after infection, while accumulation of hepatitis A antigen (HAAg) continued for 2-3 weeks more. Viral particles with the densities 1.27-1.28 g/cm3 and 1.18-1.22 g/cm3 were isolated from the infected cells as well as the mature virions with the buoyant density 1.33-1.34 g/cm3 in CsCl. The concurrent accumulation of mature virus and "light" particles (1.18-1.22 g/cm3) was registered during infection. Viral particles with the density 1.27-1.28 g/cm3 accumulated predominantly from the 14th to the 21st-24th days after infection. The mature virions (1.34 g/cm3) as well as the particles with the density 1.24-1.25 g/cm3 were isolated from supernatant precipitated by ammonium sulphate. The HAAg activity of both fractions increased progressively in equal proportion in course of infection.

Four types of virus-specific particles with different sedimentation coefficients and buoyant densities in CsCl were shown to be accumulated in hepatitis A virus (strain HAS-15) infected fetal rhesus monkey kidney cells (FRhK-4 line). Unlike the mature virions (155S, 1.34 g/cm3), cell-associated isosedimenting 92 S-particles (buoyant densities of 1.30 and 1.20 g/cm3) proved to be sensitive to lipase action. Particles of all four types were shown to contain similar sets of polypeptides, and, with the exception of "empty" 1.30 g/cm3-particles, appeared to be "full" under the immune electron microscopic examination. The viral RNA was unequivocally identified by the molecular hydridization test only in the mature virions.

Circulation of a virus similar to human hepatitis A virus by antigenic and some other properties was observed among African green monkeys imported from their natural habitats. In some of the monkeys this virus caused a disease similar to hepatitis A in many features.