Construction of a Nanobodies Phage Display Library From an Escherichia coli Immunized Dromedary

BACKGROUND: Diarrhea caused by Escherichia coli is a major cause of morbidity and mortality in young animals. Few treatment options are available, mainly antibiotic therapy increasingly limited by resistance to commonly used drugs. OBJECTIVES: The aim of this work was to develop immunotherapy based on the use of camel VHH antibody fragments, or nanobodies, to target pathogenic E. coli surface antigens. MATERIAL AND METHODS: We immunized a camel with a killed strain we had previously isolated from a diarrheic camel calf and identified as expressing the F17 fimbriae antigen RESULTS: The immunized animal developed an anti-E.coli immune response including heavy-chain antibodies. Lymphocytes from this animal were purified and RNA isolated to create a VHH library by phage display with a size of about 10(9) individual transformants. Panning on live E. coli cells resulted in the isolation of VHH fragments specific to the cell surface antigens. CONCLUSION: The identification of these antigens can lead to the development of new diagnostic and therapeutic tools against diarrhea.