The Relative Susceptibility of Normal and X-Rayed Mice of Different Stocks to Pneumotropic Viruses

Abstract

Different inbred stocks of mice varied in susceptibility to intranasal infections with influenza-B and other pneumotropic viruses. Of the four stocks tested, the black agouti mice (lC₃H and C₃H) proved significantly more susceptible than the three albino stocks (Swiss, Ak and Rf). Both morbidity and mortality were higher among the black agouti than among the albino mice. Stock C₃H carries the “milk-factor”, a virus-like agent responsible for the high incidence of mammary carcinoma in this stock. However, a genetically identical line, namely lC₃H, which is free from this milk-factor, proved equally susceptible to the pneumotropic viruses. Total irradiation with 300 r given 24 to 48 hours before intranasal infection significantly increased the susceptibility of the mice of all the stocks to small infecting doses of pneumotropic viruses.