Anti-tubercular peptides: A quest of future therapeutic weapon to combat tuberculosis

Tuberculosis (TB) is a symbolic menace to mankind, infecting almost one third of the world's populace and causing over a million mortalities annually. Mycobacterium tuberculosis (Mtb) is the key pathogen of TB that invades and replicates inside the host's macrophage. With the emerging dilemma of multi-drug resistant tuberculosis (MDR-TB) and extensively-drug resistant tuberculosis (XDR-TB), the exigency for developing new TB drugs is an obligation now for worldwide researchers. Among the propitious antimycobacterial agents examined in last few decades, anti-tubercular peptides have been substantiated to be persuasive with multiple advantages such as low immunogenicity, selective affinity to bacterial negatively charged cell envelopes and most importantly divergent mechanisms of action. In this review, we epitomized the current advances in the anti-tubercular peptides, focusing the sources and highlighting the mycobactericidal mechanisms of promising peptides. The review investigates the current anti-tubercular peptides exploited not only from human immune cells, human non-immune cells, bacteria and fungi but also from venoms, cyanobacteria, bacteriophages and several other unplumbed sources. The anti-tubercular peptides of those origins are also known to have unique second non-membrane targets within Mtb. The present context also describes the several cases that manifested the severe side effects of extant anti-TB drugs. The downfall, failure to reach clinical trial phases, inept to MDR- or XDR-TB and severe complications of the currently available anti-tubercular drugs accentuate the imperative necessity to develop efficacious drugs from adequate anti-tubercular peptides. Keeping in view of the emerging trends of drug resistant Mtb globally and unexampled mycobactericidal characteristics of peptides, the anti-tubercular peptides of varied origins can be used as a potential weapon to eradicate TB in future by developing new therapeutic drugs.