The Effect of Diet on the Susceptibility of the Mouse to Pneumonia Virus of Mice (Pvm)

Abstract

Variability in the susceptibility of different strains of mice to infection with pneumonia virus of mice (PVM) has been recognized for many years (1). Young mice appear to be more easily infected than older animals.Recently, in this laboratory, lower infectivity titers of PVM suspensions than anticipated were found repeatedly in titrations of this virus in mice. These titers were lower than those found for the same lot of virus in mice of the same strain and age in the laboratory of Dr. Frank L. Horsfall, Jr. at The Rockefeller Institute for Medical Research.Evidence has accumulated that the nutrition of the host may influence its susceptibility to infection. In general it appears that deficiency states increase host susceptibility to a variety of bacterial infections (2-4). In virus infections the reverse has been observed, and host susceptibility to a number of viruses may be decreased under conditions of dietary deficiency (5-22). Similar results were found in tissue cultures (23) and with bacteriophage (24).T h e most apparent difference in the experimental conditions for testing infectivity titers of PVM at the Rockefeller Institute and in our laboratory was dietary. At the Rockefeller Institute the mice were fed a mixture of cracked wheat, bread, powdered milk, and fresh milk; whereas the mice in our laboratory were maintained on Purina dog chow and tap water. It was decided to investigate the effects of variation in diet on the susceptibility of mice to PVM in an attempt to explain the lower infectivity titers observed in our laboratory. The present paper is concerned with short term experiments involving a 12 day period between the inoculation of PVM and the sacrifice of the mice. The results of longer term experiments in which mice were fed different diets for varying periods, before PVM inoculation as well as after, are presented in the accompanying paper (25). * These studies were conducted under contract with the Office

The Enhancing Effect of Urethane on the Severity of Infection With Pneumonia Virus of Mice (Pvm)

“…Virus Titrations.--The technique for measuring the infectivity titer of virus was similar to that employed by Horsfall and Cumen (16) and has been described in detail elsewhere (5). The methods for performing hemagglutination and hemagglutination inhibition tests were identical with those described by Curnen and Horsfall (17).…”

“…per day. Data concerning mice given a synthetic diet containing 4 per cent protein (5), such that their weight remained approximately constant, and other mice given water limited to the amount ingested by mice drinking 0.2 to 0.3 per cent urethane ad libitum, are also recorded in Table IV. It seemed possible that simple limitation of growth or fluid intake might account for the changes in susceptibility to PVM noted in mice receiving urethane.…”

“…Evidence has been presented (1) that pneumonia virus of mice (PVM) or an antigenically similar agent m a y cause latent infection in a variety of animal species. Furthermore, it has been shown that the severity of this infection in mice is influenced by the strain of mouse employed (2), the age of the mouse (3), and the diet which it is fed before (4) and during (5) the period of infection.…”