Investigation of Intestinal Bacteria-binding Monoclonal Antibodies Derived from Rabbit Single B Cells

Immunoglobulins in the intestine have been reported to play a pivotal role in regulating the composition and function of intestinal microbiota. However, the relationship between monoclonal antibodies (mAbs) and intestinal bacteria remains elusive due to the lack of analytical methods. Here we report the utilization of Ecobody technology, a single B cell technique developed by our group, for obtaining and investigating intestinal bacteria-binding mAbs derived from single B cells of a non-immunized rabbit. Bacteroides cellulosilyticus isolated from the rabbit stool was used as the antigen for selecting B cells, followed by antibody gene amplification, mAb expression in cell-free protein synthesis (CFPS), and activity evaluation. For large-scale and cost-effective production of the selected mAb, we employed the secretion expression system for antigen-binding fragment (Fab) using Brevibacillus choshinensis, and successfully yielded [~]2.0 mg/L-culture of purified antibody with high affinity to the target bacterium. Purified Fab showed binding activity towards various intestinal bacteria, suggesting the broad specificity toward intestinal bacteria-associated antigens.