Identification of fimbrial subunits in the genome of Trueperella pyogenes and association between serum antibodies against fimbrial proteins and uterine conditions in dairy cows.

Understanding the role of fimbrial subunits during bacterial adherence and the host's immunological response against anchorage proteins is critical for the development of strategies to prevent pathogens from thriving. The objectives of the present study were to locate fimbria-related proteins in the genome of Trueperella pyogenes (CP007519), define their importance for bacterial adherence, and evaluate the association between serum antibodies against fimbrial subunits and uterine health in dairy cows. Using a BLASTp search through the GenBank database, 4 putative clusters for fimbrial assembly were identified in the genome of T. pyogenes, namely FimA, FimC, FimE, and the novel major fimbriae FimJ. The fimbrial proteins FimA, FimC, FimE, and surface-anchored protein (SAP) were cloned into the pET 26b (+) vector, expressed in Escherichia coli BL21, and purified using affinity chromatography. Serum antibodies against FimA, FimC, FimE, and SAP were determined by ELISA on d 260±3 of gestation and at 2±1 and 35±3 d in milk (DIM) to assess the relationship between antigenicity against fimbrial proteins and parameters of uterine health. Antibodies against FimC and FimE were greater both pre- and postpartum in cows from which T. pyogenes was recovered by uterine flushing at 35±3 DIM, whereas T. pyogenes infection was not associated with differences in serum concentrations of FimA and SAP antibodies. Likewise, concentrations of FimC antibodies were consistently greater in cows diagnosed with clinical endometritis at 35±3 DIM compared with healthy counterparts. These results suggest that fimbrial proteins evaluated in the present study, particularly FimC and FimE, are important for maintenance of T. pyogenes in the uterus postpartum and development of uterine diseases in dairy cattle. Additional research is warranted to elucidate the mechanisms by which each fimbrial subunit contributes to the establishment of uterine diseases, evaluate its effect on fertility responses, and assess its relevance as a target for vaccine development.