Detection of cattle associated with resistance or susceptibility to bovine leukemia virus-induced kymphoma by analysis of polymorphism of the bovine MHC genes

牛白血病病毒(BLV)与流行性牛白血病密切相关，与人T细胞白血病病毒1型关系密切。采用聚合酶链式反应-测序分型方法，对白血病、持续性淋巴细胞增多症和淋巴瘤3个独立阶段的81只BLV感染动物的BOLA-DRB3基因外显子2进行了核苷酸序列测定。序列分析表明，编码DRβ链第71、74、77和78位残基的Arg或Lys、Glu、Arg和Val等位基因可能与肿瘤的抗药性有关。相比之下，70%的淋巴瘤牛在第74、77和78位残基上编码Ala、Thr和Tyr的等位基因纯合。接下来，为了证实MHC-II类基因的多态性与淋巴瘤的相关性，我们感染了28只绵羊，在16只患淋巴瘤的绵羊中，38%的绵羊携带编码Arglays(RK)的绵羊MHC(Ola)-DRBI基因第70和71位的特异性等位基因，而在12只无症状阶段的绵羊中，这一比例为83%。此外，我们用BLV囊膜糖蛋白gp51的T辅助、T细胞毒性和B细胞表位的合成抗原肽免疫RK/XX或XX/XX基因型的绵羊，最后一次免疫后两周，所有绵羊都被BLV感染的绵羊的血液攻击。携带抗性等位基因的绵羊对混合多肽表现出较高的免疫应答，未发展为白血病。

Bovine leukemia virus (BLV)is associated with enzootic bovine leukosis and is closely related to human T-cell leukemia virus types 1. We investigated the relationship between polymorphism of bovine MHC(BoLA)gene and resistance or susceptibility to BLV-induced lymphoma. The nucleotide sequencing of exon 2 of the BoLA-DRB3 gene, which is highly polymorphic, of 81 BLV-infected animals with 3 independent stages such as an aleukemic healthy, persistent lymphocytosis and lymphoma was determined by PCR-Sequenced-Based Typing method. Sequence analysis revealed that alleles eccoding Arg or Lys, Glu, Arg and Val at residues 71, 74, 77 and 78 of beta chain of DR might be related with resistance to tumor development. By contrast, 70% of cattle with lymphoma were homozygous for alleles encoding Ala, Thr and Tyr at residues 74, 77 and 78. Next, to confirm the association between polymorphism of MHC class II gene and lymphoma, we infected 28 sheep with BLV.Among the 16 sheep with lymphoma, 38% carried specific alleles of the ovine MHC(OLA)-DRBI gene encoding Arglays(RK)at residues 70 and 71 as compared to 83% among the 12 sheep at the asymptomatic stage. Futhermore, we immunized sheep carrying either a RK/XX genotype or a XX/XX genotype with a synthetic antigenic peptides of T-helper, T-cytotoxic, and B-cell epitopes of BLV envelope glycoprotein gp51, and two weeks after the last immunization, all sheep were challenged with blood from a BLV-inftected sheep. Sheep carrying resistant allele showed high immunoresponse against the mixed peptides and did not proceeded to leukemia.