ESTABLISHMENT OF SERIAL PERSISTENT INFECTIONS WITH BOVINE VIRAL DIARRHEA VIRUS IN CATTLE AND SHEEP AND CHANGES IN EPITOPE EXPRESSION RELATED TO HOST SPECIES

A pestivirus was transmitted by contact from a persistently infected ( P.I.) bullock to pregnant sheep. This resulted in the birth of P.I. la mbs, one of which in turn was able to transmit virus by contact to pre gnant cattle. Two of these animals gave birth to P.I. calves, from one of which the virus was again transmitted by contact with pregnant she ep, leading to another generation of P.I. lambs. The expression of one or more epitopes on the E2 glycoprotein of the viruses isolated from this series of alternate cattle-sheep transmissions appeared to depend on the host species. Thus, several monoclonal antibodies which bound strongly to, and neutralised, viruses isolated from the bovine hosts, failed to bind or neutralise in the case of sheep isolates. The viral consensus sequences of the E2 gene as well as parts of the 5' untransl ated region and of the N-pro and capsid genes were compared between th e different isolates. This revealed a high degree of genetic stability . However, a single codon change at amino acid position 9 of the E2 ge ne correlated with and was able to cause the loss of particular epitop es.