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Mastitis, an inflammation of the mammary gland, costs the dairy industry billions of dollars in lost revenues annually. The prevalence and costs associated with mastitis has made genetic selection methods a target for research. Previous research has identified amino acid changes at positions 122, 207, 245, 327, and 332 in the IL8 receptor, CXCR1, that result in three dominant amino acid haplotypes: VWHKH, VWHRR, and AWQRR. We hypothesize different haplotype combinations influence a cow's resistance, strength, and duration of response to mastitis. To test this, Holstein dairy cows (n=40) were intramammarily challenged with Streptococcus uberis within 3 d post-calving. All cows developed mastitis based on isolation of S. uberis from the challenged quarter at least twice. All cows with the VWHRR x VWHRR (n=5) and AWQRR x VWHRR (n=6) haplotype combinations required antibiotic therapy due to clinical signs of mastitis and tended (P=0.08) to be different from cows with a VWHRR x VWHKH (n=6) haplotype combination where only 33.3% required antibiotic therapy. Cows with a VWHRR homozygous haplotype combination displayed significantly higher responses to challenge indicated by elevated S. uberis counts (4340±5,521.9CFU/mL; P=0.01), mammary scores (1.1±0.18; P=0.03), milk scores (0.9±0.17; P=0.002), and SCC (1,010,832±489,993cells/mL; P=0.03). Contrastingly, AWQRR x VWHRR cows had significantly lower S. uberis counts (15.3±16.46CFU/mL; P=0.01), mammary scores (0.3±0.16; P=0.03), milk scores (0±0.15; P=0.002), and SCC (239,261±92,264.3cells/mL; P=0.03). Cows of the VWHKH x VWHRR haplotype combination displayed responses to challenge statistically comparable to other haplotype combinations, but appeared to have an earlier peak in SCC in comparison to all other haplotype combinations. Haplotype combination did not influence milk yield (P=0.6). Our results suggest using combinations of the SNPs within the CXCR1 gene gives a better indication of a cow's ability to combat S. uberis mastitis and could resolve prior studies' conflicting results focusing on individual SNP., (Copyright © 2017 Elsevier B.V. All rights reserved.)

One of the most economically important diseases that affect the dairy industry is bovine mastitis caused by strains of S. aureus. The development of an effective vaccine has been hampered by the antigenic diversity of the bacterium. Immunization with plasmid DNAs, encoding S. aureus antigens either as single molecule or as chimeric products containing at least two antigens, has been proposed as a novel strategy to prevent this costly disease. We continued our studies on a chimeric protein composed of the surface-located GapB and GapC proteins of S. aureus and in this work we tested the effects of DNA vaccination with plasmids encoding the individual antigens as well as the GapC/B protein with or without a boost with the recombinant proteins. The results showed that DNA vaccination alone was unable to elicit a significant humoral response and barely able to elicit a detectable cell-mediated response to the recombinant antigens. These effects were overcome by boosting with the proteins indicating that these DNA vaccines alone were not sufficient to mount an immune response against the S. aureus GapB and GapC proteins.

Bovine mastitis caused by strains of S. aureus is the most economically important disease affecting the dairy industry worldwide. Commercially available vaccines show various degrees of success and work in research laboratories with experimental vaccines suggests that in part, the failure of these vaccines lies in the limited antigenic repertoire contained in the vaccine formulations. Since it seems impractical to produce a vaccine containing antigens from all major S. aureus mastitis isolates, we took the approach of using two surface antigens GapB and GapC that appear to be conserved and constructed a GapC/B chimera as the basis for a vaccine. The humoral and cellular immune responses to GapC/B were compared to the responses to the individual proteins, alone or in combination. The GapC/B protein elicited strong humoral and cellular responses in mice as judged by the levels of total IgG, IgG1, IgG2a, and number of IL-4- and IFN-gamma-secreting cells. These results suggest that this chimeric protein could be an attractive target for further vaccine efficacy studies.