Electropherotypes and serotypes of human rotavirus in Estonia in 1989-1992.

The electropherotypes and serotypes of human rotaviruses circulating in Tallinn (Estonia) in 1989-1992 have been studied. Rotaviruses were found in 372 (25.8%) of 1,442 faecal specimens of pediatric patients with acute diarrhea. Polyacrylamide gel electrophoresis of RNA from 318 isolates has revealed 41 electropherotypes. Frequent genomic alterations, including a shift of predominant electropherotypes, were observed during the study period. The serotype of 158 (50.3%) of 314 tested rotavirus isolates was identified using ELISA with VP7-specific monoclonal antibodies against 4 established human rotavirus serotypes. Serotype G1 was found to be largely predominant and accounted for 70.9% of the typeable specimens, serotypes G4, G2, and G3 accounted for 12%, 9.5%, 7.6%, respectively. A major shift to serotype G4 took place in 1990-1991. Serotype G1 was represented by the largest number of electropherotypes. All G1, G3 and G4 isolates were of "long" and all G2 isolates were of "short" electropherotypes. According to our results the isolates of an identical electropherotype belong to the same serotype.

Analysis of rotaviral gastroenteritis in Tbilisi.

Electrophoretypes of 107 rotaviral isolates collected in Tbilisi for 18 months revealed seven patterns from which 4 were "long" and 3 "short". The "long" electrophoretypes represented 74.8% of total number of the isolates analysed. One of the "long" electrophoretypes dominated for the whole investigation period. Differences in the seasonal distribution of the isolates with various electrophoretypes were demonstrated and appearance of rotaviral isolates was registered with a "short" electrophoretype which had never been detected before.

Effect of UV-irradiation on rotavirus.

The effect of UV-irradiation on SAll rotavirus infectivity was followed. The time course of infectivity inactivation in general showed an one-hit pattern. Two basic effects of UV-irradiation on virus particles were investigated: the phenomenon of RNA-protein linkages and the formation of uracil dimers. To determine the number of uridine dimers, 3H-uridine labelled purified rotavirus was exposed to UV-irradiation, subsequently the RNA was extracted and analysed by ascending paper chromatography. Formation of photodimers was found to be an important mechanism of rotavirus inactivation at conventional UV-irradiation; the RNA-protein linkages were registered at high irradiation doses only.

Using different sorbents for the concentration of enteroviruses.

Comparative investigations were carried out to evaluate the efficiency of concentration (EC) of enteroviruses (poliovirus type 1 and simian rotavirus SA-11) using macroporous glass (brands MPG-1000 VGKh, USSR, and SO1, Czechoslovakia) and membrane filters (MF): (nitrocellulose PNTs 0.45, USSR, Millipore HAWP 0.45, USA, Synpor 0.45, Czechoslovakia as well as polycapromide MF Pall 0.2, FRG, and FMPA 0.55, USSR). To assess the sorption properties of filters, poliovirus preparations and rabbit serum gamma-globulin were labelled with radioactive isotopes. Nitrocellulose filters (Millipore and PNTs) proved to be superior in providing for 64-90% virus sorption and 20-24% protein sorption. Elution experiments using solutions of different chemical nature--protein solutions (triptosophosphate broth and beef extract), amino acid mixture (glycine + arginine), chaotropic salt (sodium trichloroacetate mixed with lysine)--showed that protein solutions better eluted rotavirus SA-11 from nitrocellulose filters and macroporous glass (MPG). The utilization of nitrocellulose filters and MPG as sorbents enables a 10-40-fold concentration of enteroviruses depending on the chosen eluent. Comparisons of EC values for rotavirus SA-11 obtained using porous glass MPS-1000 VGKh and SO1 indicated that MPS-1000 VGKh was superior both with respect to recovery efficiency (R) and concentration factor (CF).

Effect of N-phenyl-N'-3-hydroxyphenylthiourea (PTU-23) on the protein synthesis in Krebs-II cells infected with encephalomyocarditis virus.

PTU-23, a selective inhibitor of the reproduction of encephalomyocarditis (EMC) virus in Krebs-II ascites carcinoma cells, counteracts the virus-induced shut-off of the host-cell protein synthesis reducing it from 32% to 19%. The compound does not inhibit the synthesis of virus-specific proteins; the electrophoretic profile in SDS-PAAG shows an increase in the peaks of some viral polypeptides, mainly A, E and epsilon. It is suggested that this effect is connected to the partial inhibition by PTU-23 of the synthesis of the viral 37S RNA, without affecting its translation activity and also to the inhibition of the synthesis of 20S (RF) RNA--an inhibitor of the virus-specific protein synthesis. PTU-23 does not affect the processing of the high-molecular-weight viral precursor polypeptide preA, which is carried out by the virus-specific protease protein p22, as shown in studies with a cell-free system.

Efficiency of translation of viral and cellular mRNA's in extracts from cells infected with encephalomyocarditis virus.

The relative efficiency of translation of host cell mRNA and encephalomyocarditis (emc) virus RNA has been investigated in cell-free preparations from uninfected and EMC virus-infected Drebs-II cells. The ability of cell-free extracts from infected cells to translate exogenously-added EMC virus RNA and total Krebs-II cell mRNA was markedly diminished, but no evidence for the selective inhibition of translation of host cell mRNA in these systems was obtained.