Production of polyclonal phages harbouring antibody fragment genes against Xanthomonas citri subsp. citri using phage display technology

Citrus bacterial canker, caused by Xanthomonas citri subsp. citri (Xcc),is amongst the important diseases of lime orchards in southern parts of Iran. Phage display has been used to produce specific antibodies for detection of pathogen-infected plants as well as development of resistant varieties. An effector, namely pthA and a pilus protein, HrpE, the major critical components of type III secretion (T3S) system with roles in pathogenesis, were chosen as antigens. Recombinant forms of the proteins (pthA and HrpE) were expressed in a bacterial host and purified via affinity chromatography. Tomlinson phage display libraries including single chain variable fragments were used for isolation of the specific antibodies. Biopanning, 3 rounds against pthA and HrpE proteins, allowed enriching antigen-specific phages. The specificity of phages was tested using ELISA. Moreover, the phages were able to detect the plants infected with citrus bacterial canker.