Development of a Novel Anthrax Vaccine Comprising LF-PA Chimera

Abstract

Abstract Background Bacillus anthracis (BA), the etiological agent of anthrax, secretes protective antigen (PA), lethal factor (LF), and edema factor (EF) as major virulence factors. Among them, PA based vaccines are most indispensable for providing immunity against BA, but the low shelf life limits its reliability. Previous studies revealed that PA domain IV includes B-cell epitopes designated as ID I, ID II, and ID III; among them, ID II and ID III have been found to possess more toxin neutralization activity and produce high antibody titre. Moreover, N-terminal region of both LF and EF carries binding site of PA which are homologous to each other. Here, in this study we have developed and evaluate the vaccine efficacy of chimeric vaccine containing ID II-ID III region of PA and N-terminal region of LF and EF (ID-LFn). Materials and Methods ID-LFn was generated by overlapping PCR followed by cloning in pET28a. The recombinant protein was then expressed and purified by Ni-NTA chromatography. Reactivity of ID-LFn with anti-PA/LF/EF antibodies was checked by ELISA. Stability was assessed using Circular Dichroism Spectroscopy. The vaccine potential of ID-LFn was evaluated by toxin neutralization assay, lymphocyte proliferation assay, and cytokine analysis. The protection efficacy was analyzed by challenge studies in mice. Results ID-LFn was found to be significantly stable as compared with protective antigen. Anti-ID-LFn antibodies recognized PA, LF as well as EF. Though, the total antibody titre, toxin neutralization activity was found to be less than PA but surprisingly, the protection efficacy of ID-LFn was found similar as PA. Conclusion The ID-LFn vaccine might be second next generation vaccine showing equal protection but higher shelf life as PA with the capability of neutralizing PA, LF as well as EF at the same time. Thus, it may prove an efficient and reliable treatment strategy against anthrax. Disclosures All authors: No reported disclosures.