Cultivation of Louping Ill Virus

Abstract

A simple method^{1, 2} for the cultivation of vaccine virus was described which consisted of minced viable chick embryo tissue suspended either in Tyrode's solution or in a mixture of Tyrode's solution and rabbit serum. Recently it has been shown that the viruses of vesicular stomatitis 3 and poliomyelitis 4 are capable of multiplication in media similar to that used for vaccine virus. For the cultivation of the former active agent, minced chick embryo tissue suspended in Tyrode's solution was used, while for the latter minced chick embryo brain tissue suspended in a mixture of monkey serum (1 part) and Tyrode's solution (9 parts) was employed. During the past year we have been investigating louping ill, a neurotropic virus disease of sheep which in some respects resembles poliomyelitis. After the appearance of Gildemeister's note 4 on the cultivation of poliomyelitic virus, it seemed of interest to determine whether another neurotropic virus, the etiological agent of louping ill, is capable of growth in vitro under similar conditions.

Two types of media were used. The first (Series A) consisted of 0.1 gm. of minced chick embryo (11 days) brain suspended in a mixture (4.5 cc.) of monkey serum (1 part) and Tyrode's solution (9 parts). The second medium (Series B) was prepared in a manner similar to that of the first with the exception that chick embryos from which the brains had been removed were used. The media, distributed in 4.5 cc. amounts in “collar flasks” were inoculated with 0.5 cc. of infectious material. The cultures were incubated 3 or 4 days at 37°C. Subcultures were made by means of the transfer of 0.5 cc. of the incubated cultures to flasks of freshly prepared medium.