|Budget Amount *help
¥3,800,000 (Direct Cost : ¥3,800,000)
Fiscal Year 1998 : ¥1,500,000 (Direct Cost : ¥1,500,000)
Fiscal Year 1997 : ¥2,300,000 (Direct Cost : ¥2,300,000)
To investigate the relationship between polymorphism of bovine lymphocyte antigen (BoLA) gene and resistance or susceptibility to BLV-induced lymphoma, exon 2 of the BoLA-DRB3 gene which is highly polymorphic was cloned from 54 BLV-infected animals with 3 independent stages such as an aleukemic healthy, persistent lymphocytosis and lymphoma, and the nucleotide sequences were determined. Sequence analysis revealed that the BoLA-DRB3 alleles encoding Val at position 78 may be associated with resistance to BLV-induced lymphoma. Alleles encoding Val at position 78 were characterized by Arg or Lys, which represent a positive charge at position 71 and by Glu, which represents a negative charge at position 74. By contrast, alleles encoding Tyr at position 78, have amino acids such as Ala, Asn or Tyr, which represent a neutral charge at position 74 and were associated with susceptibility to lymphoma.
Next, to confirm the association between polymorphism of MHC class II gene and leukemia, we infected 28 sheep with BLV.Among the 16 sheep with lymphoma, 38% carry specific alleles of the ovine leukocyte antigen (OLA)-DRB1 Arg^<70>-Lys^<71> (RK) as compared to 83% among the 12 BLV-infected sheep at the asymptomatic stage. To analyze the immunoreaction of sheep with allele of OLA-DRB1 RK, we immunized sheep carrying either a RK/X genotype or a X/X genotype with a mixture of synthetic multiple antigenic peptides of T-helper, T-cytotoxic, and B-cell epitopes of BLV envelope glycoprotein gp 51, and two weeks after the last immunization, all sheep were challenged with blood from a BLV-infected sheep. Sheep carrying resistant allele showed high immunoresponse against the mixed peptides and did not proceeded to ieukemia. Our results indicate that difference of immunoresponse resulted due to difference of MHC class II alleles and involved the risk of BLV-induced leukemogenesis.