Enhanced Immune Response to DNA Vaccine Encoding Bacillus anthracis PA-D4 Protects Mice against Anthrax Spore Challenge

Abstract

Anthrax has long been considered the most probable bioweapon-induced disease. The protective antigen (PA) of Bacillus anthracis plays a crucial role in the pathogenesis of anthrax. In the current study, we evaluated the efficiency of a genetic vaccination with the fourth domain (D4) of PA, which is responsible for initial binding of the anthrax toxin to the cellular receptor. The eukaryotic expression vector was designed with the immunoglobulin M (IgM) signal sequence encoding for PA-D4, which contains codon-optimized genes. The expression and secretion of recombinant protein was confirmed in vitro in 293T cells transfected with plasmid and detected by western blotting, confocal microscopy, and enzyme-linked immunosorbent assay (ELISA). The results revealed that PA-D4 protein can be efficiently expressed and secreted at high levels into the culture medium. When plasmid DNA was given intramuscularly to mice, a significant PA-D4-specific antibody response was induced. Importantly, high titers of antibodies were maintained for nearly 1 year. Furthermore, incorporation of the SV40 enhancer in the plasmid DNA resulted in approximately a 15-fold increase in serum antibody levels in comparison with the plasmid without enhancer. The antibodies produced were predominantly the immunoglobulin G2 (IgG2) type, indicating the predominance of the Th1 response. In addition, splenocytes collected from immunized mice produced PA-D4-specific interferon gamma (IFN-γ). The biodistribution study showed that plasmid DNA was detected in most organs and it rapidly cleared from the injection site. Finally, DNA vaccination with electroporation induced a significant increase in immunogenicity and successfully protected the mice against anthrax spore challenge. Our approach to enhancing the immune response contributes to the development of DNA vaccines against anthrax and other biothreats.

Immunogenicity and Protective Efficiency in Mice of a Smallpox DNA Vaccine Candidate

“…Besides antigen optimization, we also employed an optimized DNA vaccine vector carrying a transcriptional enhancer that was able to strengthen the antigen production and therefore immune response of DNA vaccine. Recently our studies revealed that inclusion of the tandem repeat sequence of SV 40 enhancer upstream of a promoter in the plasmid vector enhanced the antibody production as much as 10-fold [19]. Following immunization with IgM-tL1R through electroporation, we observed the induction of a prominent antibody response.…”

“…The HRPconjugated goat-anti mouse IgG was added to each well as a secondary antibody and incubated for 1 h at 37°C. The antibody titers were determined using an end-point dilution ELISA titration assay described before [19].…”

“…Therefore, we choose the truncated L1 protein (tL1) as a target antigen in the development of DNA vaccine. Previous our DNA vaccination studies indicate that efficiency of DNA vaccination can be improved by codon optimization and attachment of an IgM signal peptide sequence [19]. In addition to the use of modified antigen, the inclusion of transcriptional enhancers in the plasmid vector also has been shown to increase of DNA vaccine immunogenicity.…”

Phylogenetic affiliation and determination of bioactive compounds of bacterial population associated with organs of mud crab, Scylla olivacea

“…strain BPS_CRB 12 revealed the maximum antimicrobial activity beside S. aureus and E. coli, which was supported by Munoz-Atienza et al (2013), who stated that 20% of the bacteria have antimicrobial activity against three of the eight tested bacterial pathogens. Bacillus anthracis strain BPS_CRB14 exhibited significant antimicrobial activity (Haber and Ilan, 2013, Crawford et al, 2009, Kim et al, 2015, Addae et al, 2014, Athamna et al, 2004).…”

Novel recombinant DNA vaccine candidates for human respiratory syncytial virus: Preclinical evaluation of immunogenicity and protection efficiency

“…38 The SV40 enhancer increases nuclear uptake, particularly in non-dividing cells, 39 increases transgene expression 40 and potentiates the antibody response. 41 The F protein, a type 1 viral protein, has long been considered the most promising target for developing DNA vaccine candidates against HRSV due to its conserved nature and its ability to activate both the humoral and cellular immune responses. 42 However, the use of the non-optimized F gene in DNA vaccination has provided unsatisfactory protection in The heatmaps were generated using the MORPHEUS software tool.…”