Abstract
Besides primary cell cultures, few cell lines support the growth of the bovine rotaviruses with development of cytopathic effect. So a calf kidney diploid cell line was developed which has predominantly fibroblastic morphology. The chromosomal number is 2n = 60 with 29 pairs of autosomes and two "X" chromosomes. The cell line supported good replication of bovine rotaviruses with development of cytopathic effect. In the absence of trypsin the cells did not support the productive replication of bovine rotaviruses present in 12 separate samples of calf diarrhoea, although development of cell-associated viral antigen was recorded up to seventh passage in 3 samples. The cells also supported the replication of bovine rhinotracheitis virus, a bovine enterovirus and poliovirus (type 1 vaccine strain). In each case there was development of cytopathic effect. A plaque assay for bovine rotaviruses was developed which worked well within narrowly defined limits. The reproducibility of the plaque test has made it possible to examine the kinetics of heat and serum inactivation. The virus was neutralised readily by homologous antirotavirus serum than heterologous serum and similar observations were also made between two bovine rotaviruses (the U. K. and the Northern Ireland strains). The two strains are being differentiated on the basis of their plaque morphology and serum neutralisation kinetics by homologous and heterologous serum. The presence of higher salt concentrations in the medium during virus adsorption, was found to shorten the replication cycle of virus. However, when the cells were grown in Earle's rather than Hank's balance salt solution in the base medium, the replicative cycle of virus was shortest (20 hours) with virtual destruction of cell monolayer in 24 hours. The role of calcium in rotavirus replication was emphasized and the isolation of rotaviruses in primary monkey kidney cells with higher concentrations of Ca[2+] in the medium is proposed.