Characterization of a single-chain variable fragment specific to Cronobacter spp. from hybridoma based on Outer membrane protein A.

Monoclonal antibody and polyclonal antibody specific to Cronobacter spp. had been reported in previous studies. However, the preparation of single-chain variable fragment (scFv) was faster and convenient. Hence, the aim of this study was to construct a scFv using outer membrane protein A (OmpA) of C. sakazakii as antigen. The protein sequences of OmpA of Cronobacter spp. were analyzed first. The results showed protein OmpA with length of 347 amino acids was conserved in Cronobacter genus (94.83%-100% of protein identity) and was greater than that observed for the other genera tested (8.28-91.64% of protein identity). Then, purified protein OmpA expressed in E. coli was used to prepare hybridoma and to construct scFv further. The scFv was named scFvH81 and analyzed by bioinformatics. The model of scFvH81 built by homologous modeling had a good quality (residues in disallowed regions: 3%) and showed that scFvH81 had a standard pocket-like site. Purified scFvH81 was prepared by denaturation and renaturation of inclusion body and it showed a good specificity and its affinity of Ka=2.39×10(6)M(-1). Therefore, it could be used in the detection and the pathogenesis study of Cronobacter spp.