Differences in Efficiency of Protective Effect Caused by High Ambient Temperature in Mice Infected with Diverse Substrains of Rabies Virus

We have shown previously that a non-fatal outcome of infection with street rabies virus occurs more often when mice are exposed to a high ambient emper-ature (HAT = 35 °C) early in the course of the infection. To determine what influence the virus strain had on this protective ffect of HAT, we have extended these observations to studies of a fixed rabies strain, CVS and several substrains of CVS virus derived from temperature-sensitive (ts) mutants. In all cases, mortality was reduced to some extent by exposure of the animals to HAT; however, dramatic strain-specific differences in the extent of the effect were noted. Although each of the virus substrains tested was revertant in the ts character (as tested in vitro using a non-permissive temperature of 4o'5 °C), several substrains (ts I, ts 4, RTal) caused disease that was sensitive (> 9 o ~ reduction in mortality) to HAT. Mortality induced by the parental CVS virus was reduced approx. 5o ~ at HAT. A single CVS virus substrain, VSWsg, caused isease that was less affected by HAT than was disease induced by the parental strain. As in previous tudies with street virus, the incubation periods for infection with CVS virus substrains were con-sistently prolonged at HAT