Abstract
The GapC of Streptococcus dysgalactiae (S. dysgalactiae) is a highly conserved surface protein that can induce protective humoral immune response in animals. However, B-cell epitopes on the S. dysgalactiae GapC have not been well identified. In this study, a monoclonal antibody (mAb5B7) against the GapC1-150 protein was prepared. After passive transfer, mAb5B7 could partially protect mice against S. dysgalactiae infection. Eleven positive phage clones recognized by mAb5B7 were identified by screening phage-displayed random 12-peptide library, most of which matched the consensus motif DTTQGRFD. The motif sequence exactly matches amino acids 48-55 of the S. dysgalactiae GapC protein. In addition, the motif 48DTTQGRFD55 shows high homology among various streptococcus species. Site-directed mutagenic analysis further confirmed that residues D48, T50, Q51, G52 and F54 formed the core motif of 48DTTQGRFD55. This motif was the minimal determinant of the B-cell epitope recognized by the mAb5B7. As expected, epitope-peptide evoked protective immune response against S. dysgalactiae infection in immunized mice. Taken together, this identified conserved B-cell epitope within S. dysgalactiae GapC could provide very valuable insights for vaccine design against S. dysgalactiae infection.
Highlights
As one of the most important pathogens causing mastitis, the Streptococcus dysgalactiae (S. dysgalactiae) is intimately associated with intramammary infection in the dairy cow [1]
The purified GapC1150 could be probed with monoclonal antibody 5B7 (mAb5B7), but not with control normal ascites, confirming that GapC1-150 containing specific epitope recognized by mAb5B7 (Fig 2C)
The results showed that the mAb5B7 could significantly react with the whole cells of S. dysgalactiae, S. agalactiae and S. uberis
Summary
As one of the most important pathogens causing mastitis, the Streptococcus dysgalactiae (S. dysgalactiae) is intimately associated with intramammary infection in the dairy cow [1]. This pathogen is ubiquitous in the dairy environment and can survive for long periods only within the mammary gland [2]. The S. dysgalactiae expresses various intracellular, extracellular or cell. Identification of a Conserved Linear B-Cell Epitope of GapC Protein
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