• Vaccine Name: M. tuberculosis DNA vaccine pAK4-sod
• Target Pathogen: Mycobacterium tuberculosis
• Target Disease: Tuberculosis
• Vaccine Ontology ID: VO_0004123
• Type: DNA vaccine
• Antigen: mycobacterial antigen superoxide dismutase A (Rv3846).
• SodA gene engineering:
  • Type: DNA vaccine preparation
  • Description: The gene sodA was subcloned into the expression vectors pAK3 and pAK4 (Khera et al., 2005).
  • Detailed Gene Information: Click Here.
• DNA vaccine plasmid:
  • DNA vaccine plasmid name:
  • DNA vaccine plasmid VO ID: VO_0005040
• Preparation: PCR amplified using gene specific primers containing Bgl II overhangs and M. tuberculosis genomic DNA as template. The blunt end PCR amplicon was cloned into EcoR V digested pLitmus-38, and then subcloned into plasmids pAK3 and pAK4 resulting in pAK3-sod and pAK4-sod. While both pAK3 and pAK4 are the eukaryotic expression vectors, pAK4 contains more CpG motifs. pAK4 also carries the ampicillin resistance gene carrying two immunostimulatory sequences. pAK3 is devoid of this ampicillin gene (Khera et al., 2005).
• Virulence: None
• Description: A study compared DNA vaccines expressing mycobacterial antigens ESAT-6 (Rv3875), α-crystallin (Rv2031c) and superoxide dismutase A (Rv3846) in Balb/c mice and guinea pigs. The DNA vaccine expression sodA was found to offer maximum protection (Khera et al., 2005).

Mouse Response

• Host Strain: Balb/c mice
• Vaccination Protocol: Mice (in groups of six each) were immunized with either the pAK3 or pAK4 vector controls or DNA vaccine candidates. Three doses of 100 μg of plasmid DNA were administered intramuscularly at 3-week intervals. Following a rest period of 3 weeks after the last dose, mice were euthanized, and antigen specific cell mediated and humoral immune responses were evaluated (Khera et al., 2005).
• Immune Response: Immunization of mice with the DNA vaccines expressing superoxide dismutase A resulted in markedly higher levels of IFN-γ as compared to the levels of IL-10. The levels of IFN-γ in supernatants from pAK3-sod and pAK4-sod immunized mice increased 2.9 and 9.1 folds compared to the levels of IFN-γ in culture supernatant of mice immunized with pAK-3 and pAK-4, respectively. Approximately 3-fold increase in IFN-γ levels in pAK4-sod immunized mice in comparison to pAK3-sod immunized mice showed that the extra CpG motif activated Th1 subtype of host immunity. Though expression of SOD antigen increases IL-10 levels, the extra CpG motifs in the vector backbone decreases the concentration of IL-10 in pAK4-sod immunized mice in comparison to pAK3-sod immunized mice (Khera et al., 2005).
  
• Challenge Protocol: No challenge experiment was performed in mice. Guinea pigs were used for protection assay for this vaccine.
• Host Ifng (Interferon gamma) response
  • Description: The levels of IFN-γ in supernatants from pAK3-sod and pAK4-sod immunized mice significantly increased compared to the plasmid vector control groups (Khera et al., 2005).
  • Detailed Gene Information: Click Here.
• Host Il10 (interleukin 10) response
  • Description: Compared to the plasmid pAK3 and pAK4 controls, expression of the SODA antigen increased IL-10 levels in DNA vaccine pAK3-sod and pAK4-sod immunized mice. The extra CpG motifs in the pAK4 plasmid decreases the IL-10 level in pAK4-sod immunized mice compared to pAK3-sod immunized mice (Khera et al., 2005).
  • Detailed Gene Information: Click Here.
• Information about this animal model: Mouse Model for TB research

Guinea pig Response

• Host Strain: Outbred guinea pigs of the Duncan Hartley strain
• Challenge Protocol: Guinea pigs (in groups of six) were immunized intramuscularly with three doses (of 100 μg each) of pAK4, pAK4-E6 expressing ESAT-6, pAK4-αcry expressing α-crystallin, or pAK4-sod at 3 weeks intervals. Four weeks after the last booster, guinea pigs were subcutaneously challenged with 1 × 10^5 CFU of M. tuberculosis H37Rv. Guinea pigs were euthanised 4 weeks after challenge (Khera et al., 2005).
• Efficacy: DNA vaccine expressing superoxide dismutase imparted the maximum protection as observed by a 50 and 10 folds reduction in bacillary load in spleens and lungs, respectively, in comparison to immunization with vector control. Among the animals vaccinated with various DNA vaccines, pAK4-sod immunized guinea pigs exhibited the minimal granuloma (Khera et al., 2005).