Antibody titers of PEG-PLA block copolymer nanosphere containing chimeric recombinant protein of protective antigen and lethal factor of Bacillus anthracis

Introduction: To date, many vaccines have been developed for anthrax but not yet an ideal vaccine. In this study, chimeric protein containing domain 1 lethal factor and domain 4 protective antigens of Bacillus anthracis in copolymer nanocapsules were used to solve the problems caused by existing vaccines and to increase the efficiency of the proposed vaccine. Materials and Methods: In this experimental study, dual solvent evaporation method was used to produce nanocapsules containing chimeric recombinant protein of protective antigen and lethal factor of Bacillus anthracis. Zeta potential of nanoparticles, nanoparticle loading efficiency, recombinant protein release pattern, potential effect of poly (lactic acid)- poly (ethylene glycol) nanoparticle (PLA-PEG) production on the viability of recombinant proteins were investigated. Mice were used as test and control samples for antibody production and immune response evaluation. Results: The mean antibody titer produced against chimeric proteins loading was significantly different from that of free antigens. Correspondingly, the difference in antibody titer was significant between the groups of one and two times’ injection of loading and free antigens and the most antibody titer was related to two times injections of loading antigens. In addition, there was a significant difference between one times injection of loading and the free antigens. This suggests that the loading chimeric antigen on PLA-PEG nanoparticles and one time injection (instead of four times injections) could produce more antibodies. Conclusion: The results of this study showed that the domain 4 protective antigens and the domain 1 lethal factor of Bacillus anthracis could chimeric with each other and produced the active antigen. This chimeric antigen (LFD1-PA4) is active and able to inducing the animal's immune system. In addition, nanocarriers containing controlled release antigens can induce the immune system of the animal.