Phenotyte of epidemic influenza B virus strains isolated in different years

The reproducing ability at elevated temperatures (non-ts phenotype) was examined for 38 influenza B virus strains isolated in different years in different countries. Out of the 7 strains isolated in 1940 to 1973, only one showed temperature-sensitivity of reproduction (a ts phenotype). In 1984 to 1988, the proportion of temperature-sensitive strains increased up to 55% (6 of 11). Since the late 1990s, the majority (90%) of the study influenza B viruses demonstrated a pronounced ts phenotype. Influenza B virus strains were also examined for their resistance to serum inhibitors. Prior to the divergence of influenza B viruses into two lines: B/Jamagata and B/Victoria, the epidemic viruses exhibited a high resistance to nonspecific inhibitors of normal equine serum. This property was also preserved in all study B/Victoria strains; however, 83% of the B/Jamagata viruses were inhibitor-sensitive. The present study has demonstrated the heterogenicity of epidemic influenza B viruses in temperature- and inhibitor-sensitivity.     

Comparative studies on influenza B virus. II. The effect of host cells on biological properties and polypeptide composition

The reproduction patterns of various influenza B virus strains isolated in 1970-1976 using roller cultures of MDCK cells and chick embryos (CE) were compared. The cultural and allantoic virus populations did not differ in their sensitivity to non-specific inhibitors from mammalian sera and in their reactivity with specific haemagglutinins (HA). The content of infectious virus and HA in the harvested allantoic fluids as compared to medium fluids were 94- and 8-fold higher, respectively, even though the fluids did not differ in the titres of complement-fixing (CF) antigen. The mol. weight (MW) of HA1 polypeptide of the B/Len/75 virus prepared in culture was higher than that Of the allantoic virus (57.5 K and 55.5 K, respectively). Under reducing conditions, the HA of the virus from culture was represented mostly by the uncleaved HA0 polypeptide, while that of the allantoic virus by the HA1 and HA2 subunits. Under non-reducing conditions, the virus from medium fluid was found to contain glycopeptide D with MW of 90 K.     

Comparative studies on sindbis virus strains isolated in Slovakia.

Two variants of Sindbis virus strains were distinguished according to the dextran sulphate (DS) marker. Large-plague strains freshly isolated from Cricetus cricetus and Rana ridibunda produced exclusively small plaques after DS treatment. The prototype Sindbis virus strain produced both large and small plaques after DS treatment. Kinetic haemagglutination-inhibition tests revealed a higher reactivity of freshly isolated strains than of the prototype strain. For differentiation of newly isolated strains of Sindbis virus, their sensitivity to sodium deoxycholate is recommended: a freshly isolated strain proved to be resistant to sodium deoxycholate.     

Comparative studies on poxvirus strains isolated from camels.

Five poxvirus strains isolated from camels in Egypt, Iran and the U.S.S.R. were investigated. The morphology and size of the negatively stained virions of the investigated strains were identical. The strains produced minute white pock lesions localized mainly on the infected area of the chorioallantoic membrane, without generalization of lesions or death of embryos. The ceiling temperature and the haemagglutinating activity of the different strains were different. All the strains were apathogenic for rabbit skin and highly pathogenic for mice inoculated intracerebrally. Serologically, all the strains were related to vaccinia virus but with different degrees. The studied strains had the characteristics of members of the genus Orthopoxvirus.     

Genome analysis of influenza B virus strains isolated during epidemics in boarding schools

Summary Genetic analysis of influenza B virus strains isolated during concurrent epidemics (February–March 1982) in three physically separated schools was carried out using the RNA:RNA hybridization technique.The data supports the hypothesis that the influenza B virus epidemics in each school were initiated by different viruses and the variability of the strains in a closed community was found to be minor though some variants were detected.With 2 Figures     

Antigenic relationships between strains of influenza B virus.

An immunological relationship between strains of influenza B virus, considerably differing from one another in haemagglutination inhibition (HI) and virus neutralization (VN) tests, was established. The relationships were also evaluated based on the ability of influenza B viruses to replicate in the lungs of mice immunized with strains possessing antigenically distinct haemagglutinin. There was no substantial difference in the protection of animals immunized with homologous or heterologous strains. Studies on the character of the immunological response of men convalescent after influenza B infection or after vaccination showed an antibody increase to both the epidemic virus and chronologically remote viruses considerably differing in antigenic properties. The data obtained suggest that influenza B viruses isolated from 1940 to 1975 belong to one antigenic subtype.     

Preparation of influenza B virus recombinant strains

The study of antigenic and biologic properties of influenza B epidemic viruses isolated in 1979 and 1983 and laboratory strain B/Lee/40 has revealed some differences in their biologic properties. The most marked changes have been found in the haemagglutinin (HA) and neuraminidase (NA) indicating that influenza B viruses underwent dramatic antigenic drifts during the period in question. The strains obtained by genetic recombination have inherited surface antigens of epidemic influenza B/Singapore/222/79 and B/USSR/100/83 viruses and preserved the HA thermolability inherent to these viruses. They have, however, acquired the marker of reproduction in chick embryos and the immunogenicity from the donor strain B/Lee/40. These recombinants can be, therefore, recommended as vaccine strain candidates.     

Biochemical studies on influenza viruses. I. Comparative analysis of equine 2 virus and virus N genes and gene products.

Ribonucleic acid (RNA) from equine 2 and virus N was analyzed by polyacrylamidegel electrophoresis and separate RNA bands isolated. Base sequence homologies with various influenza prototype strains were established and gene functions assigned to particular RNA segments. Recombinant strains obtained by double infection of chick embryo cells with the fowl plague virus (FPV) mutant ts 113, temperature-sensitive in neuraminidase, and with equine 2 virus or virus N, respectively, carry the neuraminidase gene of the rescue virus and were characterized biochemically. Evidence is presented that equine 2-specific neuraminidase consists of subunits of different molecular weights.     

Heterogeneity of influenza B virus strains isolated in a local area of the disease during an influenza outbreak

Ten strains of influenza B virus isolated in a local focus during an influenza outbreak were found to include 9 virus strain variants as demonstrated by different antigenicity of their haemagglutinin, ts-marker, sensitivity to heating at 56 degrees C/30 min, and to non-specific serum inhibitors. These strains induced antibodies in rats which interacted more actively with the virus isolated in earlier periods of this outbreak than with that isolated later. It might indicate that all strains originated from the same parent strain of virus, which induced the influenza outbreak in this area.     

Studies on some strains of tobacco mosaic virus in orchids. I. Biological, chemical, and serological studies

Seven isolates (01-07) of tobacco mosaic virus (TMV) were obtained from commercial orchids. These isolates comprise at least five distinct strains of TMV (01, 02, 04, 05, and 06). Of the five strains, four (01, 04, 05, and 06) are serologically indistinguishable from common TMV, but are distinct from each other and from other TMV strains when symptoms in various tobaccos and amino acid analyses are compared. The orchid strains of TMV differ from common TMV either by only a few amino acid exchanges, or by numerous amino acid exchanges. Strains 01 and 04 possess a pair of exchanges represented by Ile, Val --> Ala, Thr. If these strains are assumed to have arisen from type TMV by spontaneous mutational events, then the observed results suggest that the mutations arose through amination of uracil to cytosine. Strain 06 differs from common TMV by three exchanges, two of which include histidine and methionine residues; both of these amino acids are absent in common TMV. Unlike most orchid TMV strains, strain 02 (isolates 02 and 07) infects few tobaccos and differs from TMV by some 15 amino acid exchanges. It shares antigenic determinants, which are absent in common TMV, with HR and U2 strains of TMV.     

PCR restriction analysis of the genome composition of reassortant cold-adapted influenza B virus strains

A simple and sensitive method has been developed to determine the genome composition of the reassortant on the basis of B/USSR/60/69 by the restrictase analysis of DNA copies of RNA sites containing the nucleotide replacements typical of B/USSR/60/69.     

Biological properties of tick-borne encephalitis strains isolated in different parts of its geographic range

A comparative study of over 200 tick-borne encephalitis (TBE) virus strains isolated from patients and ticks in different regions varying in the proportion of severe clinical forms of TBE was carried out. The strains were tested for their pathogenicity for white mice, cytopathic and plaque-forming properties as well as for the interferon-inducing capacity in SPEV cells. All the strains were found to be highly neurovirulent for mice, to produce plaques with diameters varying form less than 1 to 10 mm, and to induce interferon production in SPEV cell. Among the TBE virus strains isolated in the Baltic republics and Vologda region there occurred strains causing complete destruction of SPEV cells at later intervals than the prototype strains. No association of the examined properties of TBE virus strains with the region of isolation or with the clinical forms of human disease was established.     

Comparative study on the properties of influenza B viruses isolated in 1959-1974]

The biological properties and antigenic structure of the following influenza B virus strains were compared: Moscow/Likh/59, Moscow/106/62, Moscow/1/66, Hong Kong/5/72, Yamagata/73 and USSR/01/4. The influenza B virus strains isolated in 1972-1974 differed by hemagglutinin from those isolated in 1959-1966. The variability of hemagglutinin correlated with that of neuraminidase. Yamagata/73 virus occupied a special position both with regard to the structure of surface antigens and to some other biological properties. Therefore, the possibility of occurrence in the USSR of virus strains similar to Yamagata/73 cannot be ruled out.