Identification of a novel linear B-cell epitope in the UL26 and UL26.5 proteins of Duck Enteritis Virus

Background: The Unique Long 26 (UL26) and UL26.5 proteins of herpes simplex virus are known to function during the assembly of the viruses. However, for duck enteritis virus (DEV), which is an unassigned member of the family Herpesviridae, little information is available about the function of the two proteins. In this study, the C-terminus of DEV UL26 protein (designated UL26c), which contains the whole of UL26.5, was expressed, and the recombinant UL26c protein was used to immunize BALB/c mice to generate monoclonal antibodies (mAb). The mAb 1C8 was generated against DEV UL26 and UL26.5 proteins and used subsequently to map the epitope in this region. Both the mAb and its defined epitope will provide potential tools for further study of DEV. Results: A mAb (designated 1C8) was generated against the DEV UL26c protein, and a series of 17 partially overlapping fragments that spanned the DEV UL26c were expressed with GST tags. These peptides were subjected to enzyme-linked immunosorbent assay (ELISA) and western blotting analysis using mAb 1C8 to identify the epitope. A linear motif, (520)IYYPGE(525), which was located at the C-terminus of the DEV UL26 and UL26.5 proteins, was identified by mAb 1C8. The result of the ELISA showed that this epitope could be recognized by DEV-positive serum from mice. The (520)IYYPGE(525) motif was the minimal requirement for reactivity, as demonstrated by analysis of the reactivity of 1C8 with several truncated peptides derived from the motif. Alignment and comparison of the 1C8-defined epitope sequence with those of other alphaherpesviruses indicated that the motif (521)YYPGE(525) in the epitope sequence was conserved among the alphaherpesviruses. Conclusion: A mAb, 1C8, was generated against DEV UL26c and the epitope-defined minimal sequence obtained using mAb 1C8 was (520)IYYPGE(525). The mAb and the identified epitope may be useful for further study of the design of diagnostic reagents for DEV.