| Summary: | <p>Abstract</p> <p>Background</p> <p>The major structural protein of coronaviruses, the membrane (M) protein, can elicit the formation of protective antibodies, but little information is available about the M protein of porcine epidemic diarrhea virus (PEDV). Identification of epitopes on the PEDV M protein will be helpful in the elucidation of the antigenic properties of this protein.</p> <p>Results</p> <p>One hybridoma cell line secreting anti-M protein monoclonal antibody (McAb) was generated and designated 4D4. To map the epitopes on the PEDV M protein, a total of 17 partially overlapping fragments covering the C-terminus of M protein were expressed as fusion proteins with a 6×His tag or a GST tag. A linear motif, <sup>193</sup>TGWAFYVR<sup>200</sup>, was identified by enzyme-linked immunosorbent assay (ELISA) and western blot (WB) analysis using McAb 4D4. The motif <sup>195</sup>WAFYVR<sup>200</sup> was the minimal requirement for reactivity, as demonstrated by removing amino acids individually from both ends of the motif <sup>193</sup>TGWAFYVR<sup>200</sup>. The result of WB analysis showed that the 4D4-defined epitope could be recognized by PEDV-positive serum, but not transmissible gastroenteritis virus (TGEV)-positive serum. Furthermore, this epitope was highly conserved among different PEDV strains, as shown by alignment and comparison of sequences.</p> <p>Conclusion</p> <p>A McAb, 4D4, directed against the M protein of PEDV, was obtained, and the 4D4-defined minimal epitope sequence was <sup>195</sup>WAFYVR<sup>200</sup>. The McAb could serve as a candidate for development of a McAb-based antigen capture ELISA for detection of PEDV. The epitope identified provides a basis for the development of epitope-based differential diagnostic techniques and may be useful in the design of epitope-based vaccines.</p>
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