The Growth of Virulent aml Attenuate(l Strains of Rinderpest Virus in Primary Calf Kidney Cells

Abstract

Large tube cultures of calf kidney cell monolayers were inoculated with RGK/1, a recent isolate of moderately high cattle pathogenicity, a virulent RBOK strain, or the RBOK strain after 90 culture passages when it was non-pathogenic. When the tubes were harvested, the fluid was centrifuged and the resultant supernatant regarded as released virus (RV), while the cells were detached from the glass by 0.02% versene. This cell-containing versene soln. was centrifuged, the supernatant being titrated for virus removed by the versene; the deposited cells were subjected to ultrasonic disruption to obtain cell-associated virus (CAV). The CAV/RV ratio was investigated daily for each strain. The attenuated RBOK strain was more easily detached from cells by versene than was either of the virulent strains. RBOK and RGK/1. The CAV in versene detached cells was further reduced by l5 min. treatment with 0.01% trypsin; the reduction was 84-97% for RGK/1, 60-90% for attenuated RBOK. Very little (0.1-2.4%) of RGK/1 infectivity was recovered in the enzyme soln., whereas the recovery rate for attenuated RBOK was over 50%. Both strains were equally highly sensitive to 0.05% trypsin, it was concluded that rinderpest virus is usually completed and accumulated at the cell surface, and that the infective particles there can be subdivided into fractions showing a different sensitivity to removal by various agents. -A.W.J.