Construction and evaluation of a novel triple cell epitopebased polypeptide vaccine against cow mastitis induced by Staphylococcus aureus, Escherichia coli and Streptococcus

Purpose: To construct a novel triple cell epitope-based polypeptide vaccine against cow mastitis induced by Staphylococcus aureus, Escherichia coli and Streptococcus and to reduce the use of antibiotics.Methods: Based on bioinformatics approach, a novel triple epitope-based polypeptide (CM-TEP) was designed and subjected to Ni-NTA flow resin purification. Purified CM-TEP was immunized into mice to prepare a polyclonal antibody. Pull-down assays and enzyme-linked immunosorbent assay (ELISA) were used to detect the interaction between CM-TEP antibodies and S. aureus, E. coli and Streptococcus. Active immunity mice and challenge of bacterial pathogens were used to detect immune protection of CM-TEP. Additionally, the optimal expressing conditions of CM-TEP strain were analyzed using orthogonal test design.Results: A novel cow mastitis triple cell epitope-based polypeptide (CM-TEP) with a MW of 36 kDa was designed, purified and used to immunize mice to prepare a polyclonal antibody. Pull-down assays and ELISA data showed that CM-TEP antibodies directly interacted with S. aureus, E. coli and Streptococcus. CM-TEP displayed a significant immune protective effect against infection by S. aureus (50 %, p < 0.05) and E. coli (54.54 %, p < 0.05) and provided some immune protective effect (30.78 %, p > 0.05) against Streptococcus. The optimum expressing conditions of CM-TEP were as follows: IPTG concentration of 0.3 mmol/L, strain OD600 value of 1, inducing temperature of 37 oC, and inducing time of 8 h.Conclusion: The findings suggest that epitope-based vaccine of CM-TEP may be a useful strategy for treating cow mastitis induced by S. aureus, E. coli and Streptococcus.Keywords: Cow mastitis, Epitope vaccine, Immunogenicity, Immune protective