Selection of a fully human single domain antibody specific to Helicobacter pylori urease

Helicobacter pylori bacteria are involved in gastroduodenal disorders, including gastric adenocarcinoma. Since the current therapies encounter with some significant shortcomings, much attention has been paid to the development of new alternative diagnostic and treatment modalities such as immunomedicines to target H. pylori. Having used phage display technology, we isolated fully humane small antibody (Ab) fragment (V_L) against the Flap region of urease enzyme of H. pylori to suppress its enzymatic activity. Solution biopanning (SPB) and screening process against a customized biotinylated peptide corresponding to the enzyme Flap region resulted in the selection of V_L single domain Abs confirmed by the enzyme-linked immunosorbent assay (ELISA), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and Western blotting. The selected Ab fragments showed a high affinity with a K_D value of 97.8 × 10^-9 and specificity to the enzyme with high inhibitory impact. For the first time, a V_L single domain Ab was isolated by SPB process against a critical segment of H. pylori urease using a diverse semi-synthetic library. Based on our findings, the selected V_L Ab fragments can be used for the diagnosis, imaging, targeting, and/or immunotherapy of H. pylori. Further, Flap region shows great potential for vaccine therapy.