Presence of glutamine at position 74 of pocket 4 in the BoLA-DR antigen binding groove is associated with occurrence of clinical mastitis caused by Staphylococcus species

Potential relationships between amino acid motifs in the antigen binding groove of various alleles of the bovine major histocompatibility complex DR (BoLA-DR) molecule and occurrence of clinical mastitis caused by Staphylococcus species (non-Staphylococcus aureus) were investigated in a case-control study. A significant association (P≤0.05) was detected between the presence of glutamic acid at position β74 and occurrence of mastitis caused by Staphylococcus spp. with a relative risk of 11. This motif is present in BoLA-DRB3.2∗22, ∗23 and ∗24 alleles. Presence of a positively charged residue (arginine or lysine) at position 13 also showed a tendency (P≤0.1) towards an association with a higher risk of clinical mastitis caused by the same bacteria. This motif is present in BoLA-DRB3.2∗23 and ∗8 alleles. Similarly, presence of arginine at position β71 (present in alleles ∗23 and ∗22) was associated with occurrence of this disease. These positions (β13, β71 and β74) form pocket 4 of the antigen binding groove, which plays an instrumental role in antigen binding and recognition by T-lymphocytes. Thus, it can be concluded that pocket 4 of the BoLA-DR molecule is involved in conferring susceptibility to clinical mastitis caused by Staphylococcus spp.