The use of restriction endonuclease enzymes and protein blot procedures in the comparison of several isolates of bovine herpesvirus I

Abstract

Six isolates of bovine herpesvirus 1 associated with one of the following diseases were compared by the restriction enzyme and western blot procedures: (1) pneumonia, (2) vulvovaginitis, (3) abortion, (4) conjunctivitis, (5) enteritis, and (6) encephalitis. In addition, two viruses incorporated in commercial modified-live infectious bovine rhinotracheitis vaccines were compared. Also, five respiratory isolates causing the same clinical disease were compared to identify differences in restriction endonuclease patterns or antibody binding. The enteric isolate was recovered from the intestine of a calf that had died two weeks after vaccination with a modified-live IBR vaccine. Histologic examination revealed that the calf had a severe enterocolitis. Results showed that this enteric virus could not be differentiated with a vaccine virus (vaccine B) of the same brand with which the calf had been vaccinated. There were, however, at least minor variations among the remaining isolates. Among the three restriction enzymes used for nucleic acid analysis, Pst 1 distinguished between all isolates with the exception of the enteric isolate and vaccine B. The encephalitis isolate showed the most marked variation, being readily distinguishable with all three enzymes. Variation among the remaining isolates was comparatively minor. Protein blot results again suggested that the encephalitis isolate had major differences (with regard to protein migration rates and antibody binding), with the other isolates, particularly in what were presumably glycoproteins, or envelope proteins. Among the other isolates, there was variation in a major viral protein of about 100,000 daltons molecular weight; the conjunctivitis, respiratory, and encephalitis isolates appeared to have an additional glycoprotein in this area that the other isolates lacked. This same variation was noted, however, among the respiratory isolates. Other, relatively minor, immunological differences were also found. It was concluded that there were reproducible differences among the BHV 1 isolates studied. In the case of the encephalitic isolate, these differences were major. The techniques also proved useful for epidemiological tracing--the enteric isolate was probably of vaccine origin. Finally, it was suggested that a long-term study of immunological drift could prove useful in detection of new variants.