Association of BoLA DRB3 and DQA1 alleles with susceptibility to Neospora caninum and reproductive outcome in Quebec Holstein cattle.

The BoLA DRB3 and DQA1 genes are part of the major histocompatibility complex (MHC) class II in cattle. These genes are highly polymorphic and have been associated with resistance to several diseases, such as mastitis, Bovine Leukemia Virus (BLV) and dermatophilis. Sequenced based typing of these genes has been carried out extensively from blood samples; however it is often impractical or expensive to obtain such samples. Repositories of well-characterized serum from cattle are readily available in many veterinary research facilities. This paper reports a retrospective analysis of BoLA class II genotypes of cattle obtained from stored serum samples from Holstein cattle from Québec dairy farms, which were obtained as part of a previous study on bovine neosporosis. It was possible to genotype 56 cattle with known infection status for Neospora caninum. We identified 14 different DRB3 and 10 different DQA1 alleles in this population. The allele frequency distribution was consistent with previously studied cattle populations, and alleles known to be associated with BLV and mastitis were present. No association was found between allele frequency distribution of DRB3 or DQA genes and infection with N. caninum. However, an association of allele DRB3*1001 and allele DRB3*2703 with resistance and susceptibility to pregnancy loss, irrespective of infection status, was identified.