Isolation and characterization of protective anti-LPS nanobody against V. cholerae O1 recognizing Inaba and Ogawa serotypes

Vibrio cholerae is considered one of the major health threats in developing countries. Lack of efficient vaccine, short incubating time of the disease, and bacterium ability to survive in aquatic environment have made cholera one of the most epidemic diseases yet known. The lipopolysaccharide is one of the bacterium key antigens used to classify V. cholerae into 206 serogroups. V. cholerae serogroup O1 is a causative agent of all cholera pandemics. Research has shown that anti-lipopolysaccharide (LPS) antibodies could provide protective immunity in cholera cases. In this research, we used N-terminal fragments of the camel's heavy-chain antibodies called VHH or nanobodies and produced a phagemid library. The obtained library was panned against V. cholerae O1 LPS, and four monoclonal nanobodies were isolated. Isolated nanobodies were tested in LPS ELISA and bacterial ELISA. The nanobody with the highest affinity toward the bacterium was used in an in vivo challenge and successfully neutralized the bacterium infection. The isolated nanobody showed high thermostability and proteolytic resistance in characterization tests.