Changes in the bovine herpesvirus 1 genome during acute infection, after reactivation from latency, and after superinfection in the host animal.

Three subtypes, as defined by HindIII restriction endonuclease (RE) analysis patterns, of bovine herpesvirus 1 (BHV 1) were used to inoculate seronegative, BHV 1-free cattle. These included: infectious bovine rhinotracheitis virus (IBRV), subtype 1.1; infectious pustular vulvovaginitis virus (IPPV) isolate K22, subtype 1.2b; and IPVV isolate FI, subtype 1.2a. Nasal, vaginal, and buffy coat samples were taken for virus isolation from each animal. RE analysis was done on virus isolates collected during acute infection, after reactivation from latency, and after reactivation followed by superinfection with a subtype of BHV 1 that differed from the primary inoculation virus. Changes occurred in the BHV 1 genome after only 1 passage in the host animal, and varied from tissue to tissue within the same animal. Viruses reactivated from latency also displayed genome variability. Only animals that received IPVV as the primary inoculation virus were successfully superinfected. After superinfection, cattle shed both superinfecting and reactivated viruses, and genome variability was observed. These data suggest that the application of RE analysis in diagnostic and epidemiologic studies of BHV 1 is limited to analysis between types and subtypes, and is not applicable for the examination of isolates from within a BHV 1 subtype.