The Mycobacterium tuberculosis recombinant LprN protein of mce4 operon induces Th-1 type response deleterious to protection in mice

Lipoproteins are known to be effective immunogens and affect both innate and adaptive immunity. The lprN gene of Mycobacterium tuberculosis has been predicted to encode for a putative lipoprotein in silico. Here, we studied its function as an immunogen by in vivo studies in mice. The recombinant LprN protein, expressed and purified in Escherichia coli, triggered a cell-mediated immune response in BALB/c mice. This was observed by significantly higher T-cell proliferation and increased production of TNF-α and IFN-γ cytokines. However, pre-exposure to LprN protein failed to provide protection in mice after challenge with a virulent strain of M. tuberculosis. Histological examination showed an increase in tissue destruction in experimental animals, indicating an immunogenic potential for LprN protein that enhanced the virulence of bacilli. The LprN protein of Mycobacterium tuberculosis may have a pathogenic potential to play important role in long term disease maintenance in host.