Comparison of biological properties of A(H1N1) influenza virus strains isolated in 1947 and during the epidemic of 1977.

A comparative analysis of biological properties of A(H1N1) influenza virus strains isolated in 1977 and the prototypic strain isolated in 1947 was performed. The strains showed marked differences in the vivo and in vitro replication as well as in the sensitivity to inhibitors of normal animal sera and to interferon. Also, their neuraminidases displayed different sensitivity to detergents.

Protective effect of different mouse interferons in mice infected with encephalomyocarditis (EMC).

Antiviral activity of various preparations of mouse interferons (Mu-IFN) administered prophylactically by the intranasal route 4 h before intranasal infection of mice with EMC virus was studied. In spite of the same activity of Mu-IFN preparations in vitro, their antiviral effect in vivo displayed differences. The "alveolar" Mu-IFN induced with NDV obtained in the upper respiratory tract, appeared to be the most effective interferon preparation in the prophylaxis of viral infection in mice.

The effect of experimental infection of mice with encephalomyocarditis (EMC) virus on interferon production by alveolar and peritoneal cells in vitro.

After infection of mice with EMC virus, dose-dependent increase or decrease of the synthesis of in vitro Newcastle disease virus (NDV)-induced interferon was observed in alveolar and peritoneal cells. It was shown that peritoneal cells from mice with mild course of the infection (infecting dose 0.2-1.

Interferon and humoral immune response in experimental influenza: infection with A/PR8 virus adapted to the mouse.

Inbred 129/Ao/Boy mice were infected with various doses of AO/PR8/HONI influenza virus. Replication of virus, synthesis of endogenous interferon and antibodies were measured. The infected mice were the source of alveolar and peritoneal cells which were used for the in vitro induction of interferon with Newcastle Disease virus (NDV).

Rat interferons. VI. Heterologous interferon in the treatment of viral infections.

In previous studies in vitro we demonstrated the protection of mouse cells against viral infections by rat interferon. In continuation, the present paper reports results of a study designed to confirm this heterospecific activity of rat interferon in vivo. Experiments were carried out with mice of the inbred 129/AoBoy strain, inoculated intranasally or intraperitoneally with EMC-strain Col MM, VSV and influenza A 055/74 viruses, and treated with mouse or rat interferon administered by the same routes as infection.

Antigenic structure and biological characteristics of influenza strains isolated in the USSR during the 1974/75 epidemic.

Antigenic analysis of strains isolated in the USSR during the epidemic in 1974/1975 showed differences in the hemagglutination inhibition test and in neuramidase activity with antisera against three reference strains. Strains isolated in a later period of the epidemic were classified into subgroup A/Port Chalmers/1/73. Nearly all strains were effective inducers of interferon and were susceptible to this inhibitor of virus replication.

Heterospecific activity of rat interferon.

In the experiments performed in vitro and in vivo it has been found that the rat and rat embryo fibroblasts cultured in vitro after the induction with virus produce interferon which displays the antiviral activity not only in the homologous cells but also in the heterologous ones. When analysed by chromatography on Sephadex G-100 it was shown that the rat serum contains two interferon populations differing in the molecular weight and both active in the homologous and heterologous cells. The interferon with the heterospecific activity has been used in the experimental therapy of mice infected with Encephalomyocarditis Virus (EMC), Vesicular Stomatitis Virus (VSV) and Influenza Virus, and was found to be effective.

Rat interferons. Homologous and heterologus rat serum activity.

Serum proteins from normal rat serum and induced with Sindbis virus were separated on Sephadex G-100. Interferon activity was studied in a system of homologous REC and heterologous LG cells. Proteins of normal serum as well as induced serum emerged in two peaks separated by a deep saddle.

Rat interferons. IV. Sialoproteins in rat serum.

Introduction of virus as inductor of interferon into rats caused a decline in serum levels of sialic acid in blood taken at the time of maximum interferon activity. Differences in the acute phase proteins were dependent on the type of virus used for induction. NDV injected intravenously did not lower serum levels of seromucoid, but given together with DMSO markedly depressed the content of this protein in the serum.

The influence of immunization on the production of interferon in vivo and in vitro.

The present study was undertaken to compare the production of interferon by immunized mice in response to different viral inducers. Porton mice were immunized with NDV or A/Wr11/57 virus by injecting 6-week-old animals with virus on days 1, 7, and 14. The interferon response was investigated 3 weeks later.

Rat interferons. III. Antiviral activity and effect of "priming" on interferon production in homologous and heterologous cell lines.

Studies on interferon from rat serum sensitive to pH 2-0 showed the following: 1) Its action is stronger in cultures of heterologous L cells than in rat fibroblast cultures. 2) Resistance acquired under the influence of interferon lasts longer in a heterologous than in a homologous system. 3) Actinomycin D added to cultures after 4 hours of contact with interferon inhibits its activity in L cells, and potentiates its activity in RE cells.