POLYMORPHISM IN BOLA-DRB3 EXON-2 CORRELATES WITH RESISTANCE TO PERSISTENT LYMPHOCYTOSIS CAUSED BY BOVINE LEUKEMIA-VIRUS

The relationship between polymorphism of the bovine lymphocyte Ag (BoL A)-DRB3 gene and resistance and susceptibility to persistent lymphocyt osis (PL) caused by bovine leukemia virus (BLV) was investigated. Exon 2 of the BoLA-DRB3 gene was cloned from animals with BoLA haplotypes previously found to be associated with resistance and susceptibility t o PL. Sequence analysis revealed the presence of the amino acids Glu-A rg (ER) at putative Ag binding residues 70 and 71 only in BoLA haploty pes associated with resistance to PL. This correlation was confirmed i n a case control study (n = 26) using an allele-specific polymerase ch ain reaction for the detection of ER at residues 70-71. These results provide a molecular basis for Ir gene control of resistance and suscep tibility to PL and suggest that the cellular immune response is import ant in preventing the in vivo spread of BLV infection.