SNPs of CD14 change the mastitis morbidity of Chinese Holstein

Gram‑negative (GN) bacterial infection is a main cause of bovine mastitis. The cluster of differentiation (CD) 14 gene serves an essential role in GN bacterium‑induced innate immune response. CD14 works as a bacterial lipopolysaccharide (LPS) receptor, combines with LPS‑liposaccharide binding protein complex, and causes cellular activation. However, the effects of CD14 single nucleotide polymorphisms (SNPs) on morbidity of clinical mastitis remain unclear. In the present study, To investigate the polymorphisms of CD14 gene and its effects on cows' susceptibility to mastitis, polymerase chain reaction‑single‑strand conformation polymorphism (PCR‑SSCP) assay was used to detect SNPs of CD14 gene in 134 Chinese Holsteins. SNPs were identified in PCR products amplified with 3 sets of primers in CD14 exon 2. A total of three SNPs were located in that exon: g.528 A→C (147Ser→Arg) in allele B; g.612 A→G (175Asn→Asp) in allele D; and g.1022 A→G in allele F (synonymous mutation). The SNPs in alleles B and D affected the secondary structure of CD14. A 3‑dimensional (3D) structural analysis predicted three potential protein forms with a similar structure and indicated that the changes of the above‑mentioned alleles were on the concave surface of the protein. In more detail, 147 Ser→Arg induced a protein kinase C phosphorylation site to move forward, as assessed by the motif analysis. The morbidity rate of AB (mixed type g.528 A/C) and CD (mixed type g.612 A/G) was the highest among all genotypes presented in the current study, and via of tumor necrosis factor‑α and interleukin‑6 mRNA levels were upregulated in animals of this genotype compared with others. Taken together, the CD14 SNPs identified in the present study, may be closely associated with the morbidity of mastitis.