• Vaccine Name: pSecTag-PA83
• Target Pathogen: Bacillus anthracis
• Target Disease: Anthrax
• Vaccine Ontology ID: VO_0000875
• Type: DNA vaccine
• Status: Research
• Antigen: Protective antigen
• Preparation: The vector pSecTag PA83, encoding the full-length PA protein, has a signal sequence for secretion of the expressed protein. For the pSecTag PA83 construct, DNA encoding the full-length B. anthracis PA83 was cloned into the eukaryotic expression plasmid pSecTag 2B. A gene fragment coding for the PA83 protein, without its own signal sequence, was amplified by PCR from DNA of a pXO2 strain of B. anthracis. The resulting 2204-bp PCR fragment was digested with Apa I and Kpn I and ligated into the vector pSecTag 2B (Hahn et al., 2004).
• Immunization Route: Intramuscular injection (i.m.)

Mouse Response

• Host Strain: BALB/c and A/J
• Vaccination Protocol: In the first vaccination trial, groups of 5 BALB/c mice were vaccinated on days 0, 14 and 28, with one of the three different PA-expressing plasmid constructs. A fourth group of five negative control mice received pCMV/ myc/ER vector DNA without insert. Each immunization consisted of a dose of approximately 1 mg plasmid DNA, precipitated onto 1.6 mm gold carriers per mouse. The DNA was applied to the shaved abdomen of anesthetized mice using a Helios gene gun. DNA-coated gold particles were discharged with 250 psi helium pressure. In the second vaccination trial, A/J mice were immunized according to the same vaccination protocol, except that the helium pressure for discharge of the DNA-coated gold carriers was increased to 400 psi. The treatment groups in this trial were pSecTag PA83 (13 mice), pCMV/ER PA83 (14 mice), and pCMV/myc/ER as a negative control group (10 mice). In the third vaccination trial, A/J mice were immunized with two shots per immunization using an increased DNA dose of 2.5 mg per shot, which were discharged with 400 psi. Six mice were vaccinated with pCMV/ER PA83 and eight with pSecTag PA83 (Hahn et al., 2004).
• Immune Response: 26 d after the final immunization, the mice were killed, bled, and the serum samples analyzed for PA-specific antibody titers. All three plasmids induced anti-PA Ig and IgG1 antibody titers. Sera from mice vaccinated with pCMV/ER PA83 had significantly higher anti-PA total immunoglobulin titers than sera from mice vaccinated with pSecTag PA83, or pCMV/ER PA63. The GMT for PA-specific IgG1 of mice immunized with pCMV/ER PA83 was higher but not significantly different than PA-specific IgG1 responses of mice vaccinated with pSecTag PA83 or pCMV/ER PA63. There were no statistically significant differences between the titers of A/J mice immunized with pSecTag PA83 and A/J mice that received the pCMV/ER PA83 plasmid (Hahn et al., 2004).
• Side Effects: Commercial anthrax vaccines can cause transient side effects, such as local pain and edema, which are probably due to trace amounts of LF and EF. None of these were noted in conjunction with the use of vaccine candidates studied here (Hahn et al., 2004).
• Challenge Protocol: 14 A/J mice were vaccinated with pCMV/ER PA83, and 13 A/J mice with pSecTag PA83. The negative control group (10 A/J mice) received pCMV/myc/ER plasmid DNA without insert. Ten days after the third immunization, all mice were bled and their individual anti-PA titers were determined by ELISA. The mice of each treatment group were then marked to be challenged with either 10 LD50 of B. anthracis STI spores or 100 LD50 of STI spores. A/J mice immunized with the increased amount of plasmid DNA were all challenged with 100 LD50. After injection with B. anthracis spores, mice were observed for a period of 14 days.Surviving mice were killed and bled. The post-challenge serum samples were also analyzed by anti-PA ELISA and for toxin neutralization titers (Hahn et al., 2004).
• Efficacy: Vaccination with either pSecTag PA83 or pCMV/ER PA83 showed significant protection of A/J mice against infection with B. anthracis STI spores (Hahn et al., 2004).
• Host Ifng (Interferon gamma) response
  • Description: Spleen cells collected from plasmid-vaccinated BALB/c mice 26 days after the third immunization produced PA-specific interleukin-4, interleukin-5, and interferon-gamma in vitro. All levels were significantly higher than those from negative control mice immunized with pCMV/myc/ER, a eukaryotic expression plasmid without the insert (Hahn et al., 2004).
  • Detailed Gene Information: Click Here.
• Host Ighg1 response
  • Description: pSecTag PA83 induced PA-specific humoral immune responses, predominantly IgG1 antibodies, in mice (Hahn et al., 2004).
  • Detailed Gene Information: Click Here.
• Host Il4 (interleukin 4) response
  • Description: Spleen cells collected from plasmid-vaccinated BALB/c mice 26 days after the third immunization produced PA-specific interleukin-4, interleukin-5, and interferon-gamma in vitro. All levels were significantly higher than those from negative control mice immunized with pCMV/myc/ER, a eukaryotic expression plasmid without the insert (Hahn et al., 2004).
  • Detailed Gene Information: Click Here.
• Host Il5 response
  • Description: Spleen cells collected from plasmid-vaccinated BALB/c mice 26 days after the third immunization produced PA-specific interleukin-4, interleukin-5, and interferon-gamma in vitro. All levels were significantly higher than those from negative control mice immunized with pCMV/myc/ER, a eukaryotic expression plasmid without the insert (Hahn et al., 2004).
  • Detailed Gene Information: Click Here.