Novel phage display-derived recombinant antibodies recognizing both MPT64 native and mutant (63-bp deletion) are promising tools for tuberculosis diagnosis

Tuberculosis (TB) is one of the top 10 causes of death in humans worldwide. The most important causative agents of TB are bacteria from the Mycobacterium tuberculosis complex (MTC), although nontuberculous mycobacteria (NTM) can also cause similar infections. The ability to identify and differentiate MTC isolates from NTM is important for the selection of the correct antimicrobial therapy. Immunochromatographic assays with antibodies anti-MPT64 allow differentiation between MTC and NTM since the MPT64 protein is specific from MTC. However, studies reported false-negative results mainly due to mpt64 63-bp deletion. Considering this drawback, we selected seven human antibody fragments against MPT64 by phage display and produced them as scFv-Fc. Three antibodies reacted with rMPT64 mutant (63-bp deletion) protein and native MPT64 from M. tuberculosis H37Rv in ELISA and Western blot. These antibodies are new biological tools with the potential for the development of TB diagnosis helping to overcome limitations of the MPT64-based immunochromatographic tests currently available.