Identification of two novel linear B-cell epitopes in p27 of feline leukemia virus using monoclonal antibodies

Feline leukemia virus (FeLV) is a gammaretrovirus that is prevalent among a wide range of felids worldwide and causes various hematopoietic disorders in domestic cats. The core protein p27 is the group-specific antigen of FeLV. It is soluble and abundantly produced, making it an ideal target for detection by immunoassays. In this study, the FeLV p27 gene, with a size of 744 bp, was expressed through prokaryotic expression systems, and the purified products were injected into BALB/c mice. Two new hybridoma cells (named mAb 1A6 and 3A7) were screened by Enzyme-Linked Immunosorbent Assay (ELISA), western blot analysis (WB), and indirect immunofluorescence assay (IFA). The antigenic epitope of these monoclonal antibodies was examined by WB or ELISA using a series of truncated GST-fused or artificially synthesized peptides. Further identification of monoclonal antibody target sequences revealed ⁴²SILVTHQ⁴⁸ (aa42-48) and ¹¹⁰AGREHL¹¹⁵ (aa110-115) as B-cell linear epitopes. An accurate identification of the epitope can provide important antigenic information, a prerequisite for effective detection. These results provided insights into the structure, function, and antigenicity of the p27 protein, thereby establishing the foundation for the development of diagnostic technologies and vaccine design for FeLV.