| The bacteria Bacillus anthracis, Yersinia pestis, and Francisella tularensis, the causative agents of anthrax, plague, and tularemia, respectively, are considered Bioterrorism Category A agents because they pose four of the greatest threats to the general population and to national security. The agents are well suited as biological weapons because they can be dispersed by aerosol delivery, are difficult to diagnose, can result in high death rates and can cause public panic. Currently, standard antibiotic treatment is effective only if administered at the early onset of symptoms, while prophylactic options are limited. The effectiveness of the licensed anthrax vaccine is constrained by production and efficacy issues, and there are no available vaccines for plague and tularemia. Recent advances in subunit peptide vaccine development offer a cost-effective and practical alternative to traditional vaccines when combined with bioinformatics analysis to identify potential peptide candidates. Thus, the aim of this study is to select peptide vaccine targets from the genomes of B. anthracis, Y. pestis, and F. tularensis, using bioinformatics approaches to screen protease candidates and other known and potential virulence factors, and to test the efficacy of KLH-conjugated peptide vaccine candidates in the presence of adjuvant in a mouse model of infection in anthrax, plague and tularemia. Bioinformatics screening of curated and putative proteases and known virulence factors resulted in the selection of proteins considered important in disease pathogenesis, and subsequently, annotated regions (peptides) of the proteins were chosen as vaccine candidates. This study demonstrated that individual administration of F. tularensis peptides elicited high protection in immunized mice, while several proteases in B. anthracis and Y. pestis were also effective. Mixing combinations of individual peptides for each organism generated significant protection, and increasing peptide concentrations also yielded strong immunogenicity. The data offers insight into putative virulence factors in tularemia and reveals additional proteins that may play a role in the disease pathogenesis of anthrax and plague. This work affirms that peptides identified by bioinformatics analysis when used as subunit vaccines can provide a feasible and effective countermeasure to the threat encountered by the three Category A pathogens. |
