The RD1 and RD9 genomic regions are present in all virulent and clinical strains of M. tuberculosis but deleted in all M. bovis BCG vaccine strains . The importance of proteins encoded
by RD1, both for diagnosis and vaccine development, is highly suggestive because three genes of this region have been conclusively shown to be expressed in M. tuberculosis and are major antigens recognized by antibodies (ORF14) and T cells (EsxA and EsxB) of patients with TB and/or healthy but exposed individuals [30, 31]. In particular, EsxA and EsxB proteins are recognized by T cells with protective phenotype, i.e. memory and effector IFN-γ secreting T cells in mice and human T cells producing large quantities of IFN-γ [32–35]. To prepare DNA vaccine constructs using the plasmids, DNA fragments corresponding to PE35, PPE68, EsxA, EsxB and EsxV genes were PCR amplified by using gene-specific primers, and Palbociclib manufacturer the amplified DNA were first cloned into pGEM-T Easy vector, before subcloning into
pUMVC6 and pUMVC7. This was performed to facilitate the cloning of appropriate DNA into the eukaryotic expression vectors, as has been performed previously for prokaryotic expression vectors [14, 15]. A total of 10 recombinant DNA plasmids (five for each vector) were constructed. All the aforementioned recombinant DNA plasmids were studied for expression and immunogenicity of the cloned fragments by immunizing mice. The results show that both the vectors induced antigen-specific cellular proliferation to PE35, EsxA, EsxB, and EsxV proteins. However, recombinant pUMCV6 induced relatively better responses Kinase Inhibitor Library solubility dmso than recombinant pUMCV7.
The improved responses with recombinant pUMCV6 suggest that hIL2 secretory protein acted as a better Sodium butyrate adjuvant and enhanced cellular immune responses, assessed by antigen-induced proliferation of splenocytes, to the fused mycobacterial proteins more effectively than the tPA signal peptide. The relevance of antigen-specific cellular proliferation induced by DNA vaccine constructs with protection against M. tuberculosis challenge has been demonstrated in the mouse model of TB . Although the results of this study, showing induction of antigen-specific immune responses to the antigens encoded by genes present in DNA vaccine constructs, are interesting, the work should be extended to demonstrate their protective efficacy in challenge experiments with M. tuberculosis using various animal models of TB, e.g. mice, guinea pigs, rabbits and monkeys. If found effective in animals, such vaccines may be useful in both prophylactic and therapeutic applications in humans. Furthermore, DNA-based vaccines expressing M. tuberculosis-specific antigens may even be useful in BCG-vaccinated subjects as preventive vaccines, because revaccination with BCG has not shown beneficial effects [4, 37, 38] and may even be combined with BCG to improve its protective efficacy .