Effects of corticosteroids on mouse hepatitis virus infection.

Corticosteroid administration has been shown to have a deleterious effect in various viral infections in experimental animals. High mortality rates have occurred in animals but in most studies pharmacological doses of corticosteroids were used and were given before the viral infections (Shwartzman, 1950; Kilbourne and Horsfall, 1951). Starr and Pollard (1958) and Bang and Warwick (1960) found that mice which were normally resistant to mouse virus hepatitis became more susceptible if they were treated with corticosteroids before virus inoculation. Manso, Friend, and Wroblewski (1959), Vella and Starr (1965), and Hirano and Ruebner (1966) showed that the severity of infection with mouse hepatitis virus was increased in susceptible animals when corticosteroid therapy preceded or accompanied virus inoculation. In contrast to these animal studies, Katz, Velasco, Klinger, and Alessandri (1962) claimed that massive doses of corticosteroids were of benefit in the management of patients with fulminant viral hepatitis. The administration of murine hepatitis strains of virus (MHVS) to mice produces a disease which evolves slowly, is associated with abundant inflammation, and leads to a spectrumofmorphological lesions which closely simulate human viral hepatitis (Jones and Cohen, 1962). In view of these effects of MHVS infection we considered it of interest to determine the results of corticosteroid administration on the course of infection with this virus. The disease process was followed by changes in plasma enzymes, liver histology, and mortality. These studies have shown that corticosteroids have an adverse effect on mouse hepatitis virus infection and that this response is associated with an increase of virus particles in the liver. Of significance was the finding that the steroid effect was dependent on the time at which the hormone was administered.