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 0.2-1.0 LD50 per mouse) produce interferon in vitro on the same level as the control cells. Alveolar cells isolated from the same mice shortly after infection exhibited increased interferon production in vitro as compared with the analogous cells isolated from the non-infected mice. Acute, EMC-induced infection in mice (infecting dose 5.0 LD50 per mouse) caused suppression of interferon synthesis in vitro by both peritoneal and alveolar cells, which intensified together with the progression of the disease.

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. 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. Stimulation of interferon production by Sindbis virus was accompanied by a significant rise in levels of seromucoid. The same virus given together with DMSO had no effect on protein level, which remained normal, but lowered the content of sialic acid in proteins.

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. 4) In rat embryonic cells treated with interferon, interferon production following induction with ND virus is blocked. Similar blocking was observed in cultures of L cells after 24-hour priming; after 6 hours of exposure of L cells to rat interferon, on the other hand, production of interferon was enhanced.