Isolation, characterization, and physical mapping of a pseudorabies virus mutant containing antigenically altered gp50.

A pseudorabies virus variant ( mar197 -1) containing a mutation in a viral glycoprotein with a molecular weight of 50,000 ( gp50 ) was isolated by selecting for resistance to a neurtralizing monoclonal antibody ( MCA50 -1) directed against gp50 . This mutant was completely resistant to neutralization with MCA50 -1 in the presence or absence of complement, and was therefore defined as a mar (monoclonal-antibody-resistant) mutant. The mutation did not affect neutralization with polyvalent immune serum. The mar197 -1 mutant synthesized and processed gp50 normally, but the mutation prevented the binding and immunoprecipitation of gp50 by MCA50 -1. Thus, the mutation was within the structural portion of the gp50 gene affecting the epitope of the monoclonal antibody. The mutation was mapped by marker rescue with cloned pseudorabies restriction enzyme fragments to the short region of the pseudorabies genome between 0.813 and 0.832 map units. This is equivalent to a 2.1-kilobase-pair region.