B-CELL EPITOPE PREDICTION of Mycobacterium tuberculosis Ag85A ANTIGEN

Abstract

Tuberculosis (TB) infection is one of the major public health problems in developing country including Indonesia. The endemic of TB infection caused by Mycobacterium tuberculosis became worse because of the multidrug-resistant TB (MDRTB).

M. tuberculosis had special feature which is its cell wall or envelope that consists of complex lipids, lipoglycans and peptidoglycans (Forrelad, 2013). The cell wall consisted of two layers, the inner and the outer. The inner consisted of peptidoglycan sacculus veiled by mycolylarabinogalactan polysaccharide layer. The outer envelope consisted of trehalose 6,6′dimycolate

(TDM; cord factor) which was synthesized by fibronectin binding protein (fbp)/ antigen 85 (Ag85) complex (Elamin, 2011). The Ag85 complex was a 30–32 kDa protein consisting of three proteins (Ag85A, Ag85B, and Ag85C). It had several functions, including enzymatic mycolyl-transferase activity for coupling of mycolic acids to cell wall arabinogalactan, cord factor biogenesis (trehalose-dimycolate), and had capacity to bind to fibronectin and elastin of the extracellular matrix proteins (Huygen, 2014). This protein were encoded by three paralogous genes located in different regions of the bacterial genome (D’Souza, 2003). The Ag85 complex was the major secreted protein of M. tuberculosis cell culture besides of its association with bacterial surface. It had essential role in the pathogenesis of tuberculosis. The ability of this protein to bind fibronectin promoted M. tuberculosis adhesion to the mucosal surface, thus facilitating the bacteria to entry into the host cell. However, the main role of it to the virulence of M. tuberculosis was the ability to synthesis of cell wall lipids (Forrelad, 2013).