Binding affinity studies of Endo H deglycosylated and different variants of PA83 antigens with anti-PA83 monoclonal antibodies

Anthrax is a disease caused by Bacillus anthracis bacteria that affects both humans and animals and results in death if left untreated. It is very important to develop a safe, low cost, long-term stable and highly immunogenic vaccine against anthrax. The recombinant protective antigen (PA) of B. anthracis is a potential vaccine candidate against Anthrax. Plants that are among the recombinant protein expression systems can be used as great biofactories with low cost and convenient safety profiles compared to other expression systems. Since plants have a eukaryotic post-translational modification mechanism, recombinant proteins can be produced using the transient gene expression method. However, the protective antigen is a bacterial protein and is not a glycoprotein in its host. In Mamedov et al. studies in 2017, biologically active deglycosylated PA was produced by the co-expression of protective antigen PA and peptide-N-glycosidase F (PNGase F) enzyme. In this study, we performed binding affinity studies of Endo H deglycosylated protective antigen PA and also other PA variants, with plant-produced anti-PA83 monoclonal antibody, produced in our lab and also commercially purchased anti-PA mAb. Plant produced Endo H deglycosylated PA83 showed strong affinity compared to other variants of PA83. In addition, anti-PA83 mAb produced against Endo H deglycosylated PA83 in Nicotiana benthamiana showed higher affinity compared to commercial anti-PA mAb.