Novel approaches toward the development of an oral post-exposure DNA vaccine for latent tuberculosis using Salmonella typhimurium ∆aroA vector

Abstract

Tuberculosis remains one of the major causes of global public health problems. There is no effective vaccine for the disease until now. Many reports show that DNA vaccines are promising to induce protection against Mycobacterium tuberculosis (M. tb); however, the efficiency of DNA vaccine is limited due to inadequate delivery systems. Among others, live attenuated bacterial vectors such as Salmonella enterica typhimurium ( S. typhimurium ) have significant promise as efficient mucosal delivery vehicles for DNA vaccines. In this study, we constructed recombinant attenuated S. typhimurium DNA vaccines carrying genes encoding resuscitation promoting factor (Rpf)-like proteins of M. tb on eukaryotic expression plasmid agianst latent tuberculosis and evaluated the plasmid stability and growth curve assays of the recombinant Salmonella vaccine constructs in vitro. Four Rpf gene fragments (RpfB, RpfC, RpfD, RpfE) associated with latency were amplified from genomic DNA of the H37Rv strain of M. tb, cloned into eukaryotic expression plasmid (pVR1020) and verified by sequencing. In later studies, we will demonstrate the potential use of the Salmonella -mediated DNA constructs as candidate post-exposure vaccines against tuberculosis through testing their immunogenicity and effectiveness for oral delivery in eukaryotic systems. Key words : Latent tuberculosis, resuscitation promoting factor (Rpf), DNA vaccine, recombinant Salmonella typhimurium.