Since the body temperature of the resting bat has been shown to parallel that of its environment over a wide range, these animals were used in a study to determine the effect of temperature on a virus under in vivo conditions. A strain of Japanese B encephalitis (JBE) virus was passed serially in big brown bats (Eptesicus f. fuscus) maintained at 24°C or 37° C, and the virus lines obtained were characterized and compared with lines developed by serial passage in hamster-kidney cell (HKC) cultures kept at the same temperatures. A virus line developed by passage in HKC cultures incubated at 24°C showed significant loss in virulence for mice, whereas passage of the virus in the bat maintained at 24°C did not result in any significant reduction in mouse pathogenicity. In addition, passage in HKC cultures at 37°C either did not affect or slightly increased the ability of the virus to multiply in this in vitro system at 37°C and 40°C, whereas passage in bats kept at 37°C, with body temperatures of 37°C or higher, seemed to de-adapt the virus for growth in HKC cultures at the higher temperatures. These observations suggest that the effect of temperature on certain characteristics of this strain of JBE virus varies depending on whether serial passage is carried out in vitro or in an in vivo system. The use of the bat as a host for the study of temperature-sensitive conditional-lethal mutants of arboviruses was discussed.
Predoctoral fellow, U.S. Public Health Service, National Institute of Allergy and Infectious Diseases Training Grant 5 T1 AI 142. Present address: Department of Microbiology, The University of Texas Medical Branch, Galveston.