Staphylococcus aureus β-hemolysin-neutralizing single-domain antibody isolated from phage display library of Indian desert camel

ObjectiveTo isolate and characterize Staphylococcus aureus (S. aureus) β-hemolysin-neutralizing dAbs from phage display library of Indian desert camel.MethodsPhage display library of 5×107 dAb clones of LPS-immunized Indian desert camel constructed in our laboratory was used for selection of S. aureus exotoxin-specific clones by panning technique. Enrichment of Ag-specific clones in successive rounds of panning was assessed by phage-ELISA and phage titration. Different dAb clones binding to S. aureus exotoxin Ags were expressed with C-terminal 6× His tag in E. coli and purified by Ni-chelate chromatography. The expression was verified by SDS-PAGE and western blotting. The purified clones were tested for inhibition of ‘hot-cold’ hemolytic activity in vitro. Resistance to thermal inactivation of the dAb clones was studied by observing the effect of heat treatment from 50 °C to 99 °C for 30 mins on the ‘hot-cold’ hemolytic activity in vitro.ResultsSeveral dAb clones binding to S. aureus exotoxins were isolated and enriched by three rounds of panning. The soluble dAb clones were approximately ∼16 kDa in size and reacted with 6× His tag specific murine monoclonal antibody in western blot. One of the Ni-chelate affinity purified dAb.6× His clones, inhibited S. aureus β-hemolysin activity in vitro and resisted thermal inactivation upto 99 °C.ConclusionsAn S. aureus β-hemolysin-neutralizing dAb clone of possible therapeutic potential has been isolated.