Cloning, expression and genetic immunization studies of Mycobacterium tuberculosis gene esat6

Mirza Imran Shahzad, Imran Khan, Paul A Luciw, Muhammad Gulfraz, Azra Khanum

Research output: Contribution to journalArticle

Abstract

Early secreted antigenic target protein 6 (esat6) is one of the genes present on region of difference 1 (RD1) of Mycobacterium tuberculosis (M. tb) genome. This RD1 is a characteristic of virulent strains of M tb and Mycobacterium bovis and this is one of the major differences between the disease causing strains and Bacillus-Calmat Guerin (BCG) vaccine strains. Studies have proved the presence of large number of memory T cells in M. tb infected individuals and these memory cells are reactive towards Esat6 antigen, which highlighted the importance of this gene especially in early infections. In this study, numbers of esat6 gene constructs were made in order to get a suitable construct to be used as good DNA vaccine. First esat6 gene construct was made in pND vector without Kozak sequence upstream the gene, second construct was made in pcDNA3.1 vector with Kozak sequence upstream the gene, third construct was made again in pND vector with Kozak sequence, fourth construct was made with Kozak sequence upstream and GGG downstream the ATG as a second codon of gene first in pcDNA3.1 and later in pND vectors respectively which was designated as construct five. Sixth construct was a fusion and in pcDNA3.1 vector with Kozak upstream the gene and epitope V and poly histidine tail sequence provided by vector down stream the gene through inframe cloning of esat6 gene with sequences provided by vector by removing stop codon through PCR based primers. Seventh and final construct was prepared in pND14 vector also as a fusion construct and gene was cloned under tissue plasminogen activator sequence in an in-frame through PCR based primers. All these constructs were subjected to 293T human embryonic kidney cell lines to evaluate their level of expression. Although none of the constructs gave detectable level of expression in cultured cells when tested through Western blots (WB) but tpa-esat6-pND14 construct was selected as potential DNA vaccine candidate to inject intramuscularly and interadermally to balb/c mice along with controls to obtain detectable response in vivo. Animals were tested nine weeks post vaccination and found positive against tpa-esat6-pND14 vaccine through WB and multiplex micro bead immunoassay (MMIA).

Original languageEnglish (US)
Pages (from-to)749-757
Number of pages9
JournalPakistan Journal of Zoology
Volume45
Issue number3
StatePublished - 2013

Keywords

  • Balb/c mice
  • DNA vaccine
  • Esat
  • MMIA
  • PND vectors
  • TB vaccine

ASJC Scopus subject areas

  • Animal Science and Zoology

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