Bluetongue virus: some relationships among North American isolates and further comparisons with EHD virus

Seven isolates of bluetongue virus with different isolation histories and one isolate of the virus of epizootic hemorrhagic disease of deer were cloned by three consecutive plaquings in L-929 cells. The isolates were categorized on plaque size and margin. Antisera to the bluetongue virus isolates were produced in calves and antiserum to epizootic hemorrhagic disease virus in deer. Plaque reduction neutralization tests were done using the eight isolates and antisera to six of these. The isolates could be partially categorized on plaque type. In the plaque reduction neutralization test, all of the bluetongue viruses cross reacted and although differences were frequently observed, no obvious antigenic classification was possible. Reactions between the bluetongue viruses and epizootic hemorrhagic disease virus were all within the limits of what is presently considered to be non-specific inhibition.