[Preliminary Study on Screening and Identification of Lewis a Antigen Mimic Epitope in Alpaca Phage Display Nanobody...

To establish a new method for synthesizing Lewis blood group antigens, that is, the mimotopes of Lewis blood group antigens were screened by using an alpaca phage display nanobody library.

We selected mimotopes of the Lewis a (le^a) antigen by affinity panning of an alpaca phage display nanobody library using a monoclonal anti-le^a antibody. Enzyme-linked immunosorbent assay (ELISA) was used to test the affinity of the positive clones for the monoclonal anti-le^a antibody, and the high-affinity positive clones were selected for sequencing and synthesis. Finally, the sensitivity, specificity and reactivity of the synthesized le^a mimotope in clinical samples were verified by ELISA.

A total of 96 phage clones were randomly selected, and 24 were positive. Fourteen positive clones with the highest affinity were selected for sequencing. The result showed that there were 5 different sequences, among which 3 sequences with the highest frequency, largest difference and highest affinity were selected for expression and synthesis. The sensitivity and specificity of le^a mimic antigen by ELISA showed that, the minimum detection limit of gel microcolumn assay (GMA) and ELISA method were 25 times different, and the le^a mimic antigen had no cross reacted with the other five unrelated monoclonal antibodies(P<0.001). Finally, 30 clinical plasma samples were analyzed. The mean absorbance of the 15 positive plasma samples was significantly higher than that of the 15 negative plasma samples (P=0.02). However, the positive signal values of the clinical samples were much lower than those of the monoclonal antibodies.

A new method of screening le^a mimic antigen by using alpaca phage nanoantibody library has been established, which is expected to realize the screening of le^a mimotopes, thus realizing the application of high-sensitivity detection methods such as ELISA and chemiluminescence in blood group antibody identification.