Selection and Identification of Single-Domain Antibodies Against Bartonella Invasion-Associated Locus B

Abstract

At least 15 species or subspecies of Bartonella are zoonotic, each species appears to be highly adapted to one or a limited number of reservoir animals in which it is asymptomatic, while it can be transmitted to humans in which a variety of clinical manifestations can be caused. It was reported that Bartonella invasion associated locus B (IalB) played an important role in Bartonella pathogenesis. Our recent study showed that IalB had high sequence homology among different Bartonella species, and anti-IalB antibodies reacted strongly with Bartonella whole-cell lysates, which suggested that anti-IalB antibodies might be a good candidate for diagnosis of Bartonella infection. In the present study, we screened for single domain antibody fragment (sdAb) candidates against Bartonella birtlesii IalB from a sdAb phage display library. Following four rounds of panning, several positive phage clones were isolated. Among them, VH2 and VH7 were shown high enrichment. Their capable of recognizing IalB was verified by binding assays, phage ELISA and soluble fragment ELISA. Their CDRs are speculated to perform IalB binding function by molecular docking. And VH2 and VH7 had high specificity for Bartonella and did not cross-react with other bacteria. The VH2 and VH7 might be good candidates for specific diagnosis of Bartonella infection.