Intracellular oligomerization of influenza virus nucleoprotein.

It has previously been shown that the purified influenza virus nucleoprotein (NP) forms the oligomers in vitro in NP preparations obtained from virions (Wiley et al., 1977, Virology, 79, 446-448; Ruigrok and Baudin, 1995, J. Gen. Virol., 76, 1009-1014) and infected cells (Becht and Weiss, 1991, Behring Inst Mitt., Justus-Liebig Universitat, Giessen, 89, 1-11). We have shown in this report that boiling-sensitive NP oligomers (di- and trimers) are formed in vivo in the course of intracellular influenza virus replication. They are detected by PAGE about 10 min after monomeric 56-kDa NP molecules are synthesized. NP oligomers are formed by different strains of influenza virus in different cell lines. Some influenza virus strains are characterized by complete conversion of NP monomers into oligomers and others by only partial conversion. In the Triton X-114 phase partitioning system NP oligomers show more hydrophobicity than NP monomers. NP oligomers are detected in the sedimentable and soluble fractions of both cell lysate and extracellular medium. The possibility is discussed that oligomeric NP is a native and functionally significant form of influenza virus NP.

[Analysis of influenza virus reproduction under conditions of chronic infection]. / Analiz reproduktsii virusa grippa v usloviiakh khronicheskoi infektsii

The results of comparative studies of influenza virus, original and produced in KM cells under conditions of chronic infection (KM WSN) are presented. The WSN KM virus was shown to band in the density range of 1.18 to 1.23 g/ml, with maximum at a.215 g/ml. The electrophoretic analysis of the standard virus RNA revealed mostly heavy fragments. The analysis of a total RNA preparation from the virus population produced by chronically infected cells revealed both heavy and light RNA fragments. The total synthesis of cellular DNA and RNA was slightly inhibited by KM WSN. A mechanism of persistence is suggested associated with continuous production of defective non-infectious particles.

[Chronic infection of diploid cells of human embryo musculocutaneous tissue]. / Khronicheskaia infektsiia diploidnykh kletok kozhno-myshechnoi tkani émbriona cheloveka

A model of chronic influenza infection of a strain of human embryo skin-muscle tissue diploid cells (KM WSN) was developed. When the cells were propagated without medium changes, they regularly produced virus in low infectious titres and hemagglutinins in titers of 1 : 2 to 1 : 4. Frequent medium changes caused more intensive infectious virus reproduction with no or very poor hemagglutinin accumulation. Superinfection of KM WSN cultures even with frequent medium changes led to a marked reduction in the amount of infectious virus production with no detectable interferon. The WSN KM virus was found to differ from the initial variant by a number of markers. The observed pattern of virus production suggests a mechanism of persistence in this system in connection with the interfering effect of the defective virus produced by the cells.

[Virus-specific syntheses in cells infected with the virions from standard and "defective" populations of the influenza virus (author's transl)]. / Virusspetsificheskie sintezy v kletkakh, infitsirovannykh virionami iz standartnoi i "defektnoi" populiatsii virusa grippa

The structure of influenza virus virions from the standard and "Magnus" populations as well as intracellular syntheses induced by them were studied. Virions of influenza virus were shown to be heterogeneous with respect to the set of fragments in them. This heterogeneity was more marked in virions of the "Magnus" population and consisted in a relatively greater deficiency of large fragments. A marked induction of light RNA fractions in the cell by defective influenza virus was demonstrated. Synthesis of protein and the polypeptide composition of virions were found to be similiar in standard and "Magnus" viruses.

[Heterogeneity of an influenza virus population in the manifestation of biological functions (author's transl)]. / Geterogennost' populiatsii virusa grippa v proiavlenii biologicheskikh funktsii

In a population of influenza virus, virions have different degree of the functional capacities to produce infectious virus, to induce neuraminidase production and to interfere with infectious virus. Fractions of virus were found which had a poor capacity for production of infectious progeny and a relatively high induction of neuraminidase synthesis as well as induction of heterogenous light fractions of RNA in cells. In the population of defective virus a fraction of particles possessing marked interfering activity in the absence of infectivity was found.