Generation of Recombinant Antibodies against the beta-(1,6)-Branched beta-(1,3)-D-Glucan Schizophyllan from Immunized Mice via Phage Display

Developing Recombinant Antibodies by Phage Display Against Infectious Diseases and Toxins for Diagnostics and Therapy

Antibodies are essential molecules for diagnosis and treatment of diseases caused by pathogens and their toxins. Antibodies were integrated in our medical repertoire against infectious diseases more than hundred years ago by using animal sera to treat tetanus and diphtheria. In these days, most developed therapeutic antibodies target cancer or autoimmune diseases. The COVID-19 pandemic was a reminder about the importance of antibodies for therapy against infectious diseases. While monoclonal antibodies could be generated by hybridoma technology since the 70ies of the former century, nowadays antibody phage display, among other display technologies, is robustly established to discover new human monoclonal antibodies. Phage display is an in vitro technology which confers the potential for generating antibodies from universal libraries against any conceivable molecule of sufficient size and omits the limitations of the immune systems. If convalescent patients or immunized/infected animals are available, it is possible to construct immune phage display libraries to select in vivo affinity-matured antibodies. A further advantage is the availability of the DNA sequence encoding the phage displayed antibody fragment, which is packaged in the phage particles. Therefore, the selected antibody fragments can be rapidly further engineered in any needed antibody format according to the requirements of the final application. In this review, we present an overview of phage display derived recombinant antibodies against bacterial, viral and eukaryotic pathogens, as well as microbial toxins, intended for diagnostic and therapeutic applications.

Dietary schizophyllan reduces mitochondrial damage by activating SIRT3 in mice

Schizophyllan (SPG), produced by Schizophyllum commune, is an exopolysaccharide with multiple academic and commercial uses, including in the food industry and for various medical functions. We previously demonstrated that SPG conjugated with c-Src peptide exerted a significant therapeutic effect on mouse models of the acute inflammatory diseases polymicrobial sepsis and ulcerative colitis. Here we extended these results by investigating whether SPG exerted a protective effect against mitochondrial damage in the liver via sirtuin 3 (SIRT3) induction, focusing on the deacetylation of succinate dehydrogenase A (SDHA) and superoxide dismutase 2 (SOD2). Liver damage models induced by alcohol or conjugated linoleic acid (CLA, which simulates lipodystrophy) in SIRT3^-/-, SOD2^-/-, and SDHA^-/- mice were used. Results showed that dietary supplementation with SPG induced SIRT3 activation; this was involved in mitochondrial metabolic resuscitation that countered the adverse effects of alcoholic liver disease and CLA-induced damage. The mitochondrial SIRT3 mediated the deacetylation and activation of SOD2 in the liver and SDHA in adipose tissues, suggesting that SPG supplementation reduced ethanol-induced liver damage and CLA-induced adverse dietary effects via SIRT3-SOD2 and SIRT3-SDHA signaling, respectively. Together, these results suggest that dietary SPG has a previously unrecognized role in SIRT3-mediated mitochondrial metabolic resuscitation during mitochondria-related diseases.

Structural insights into antigen recognition of an anti-β-(1,6)-β-(1,3)-D-glucan antibody

Schizophyllan (SCH) is a high molecular weight homopolysaccharide composed of a β-(1,3)-D-glucan main chain with branching β-(1,6)-bound D-glucose residues. It forms triple helices that are highly stable towards heat and extreme pH, which provides SCH with interesting properties for industrial and medical applications. The recombinant anti-SCH antibody JoJ48C11 recognizes SCH and related β-(1,6)-branched β-(1,3)-D-glucans, but details governing its specificity are not known. Here, we fill this gap by determining crystal structures of the antigen binding fragment (Fab) of JoJ48C11 in the apo form and in complex with the unbranched β-(1,3)-D-glucose hexamer laminarihexaose 3.0 and 2.4 Å resolution, respectively. Together with docking studies, this allowed construction of a JoJ48C11/triple-helical SCH complex, leading to the identification of eight amino acid residues of JoJ48C11 (Tyr27H, His35H, Trp47H, Trp100H, Asp105H; Asp49L, Lys52L, Trp90L) that contribute to the recognition of glucose units from all three chains of the SCH triple helix. The importance of these amino acids was confirmed by mutagenesis and ELISA-based analysis. Our work provides an explanation for the specific recognition of triple-helical β-(1,6)-branched β-(1,3)-D-glucans by JoJ48C11 and provides another structure example for anti-carbohydrate antibodies.

Designing Human Antibodies by Phage Display

With six approved products and more than 60 candidates in clinical testing, human monoclonal antibody discovery by phage display is well established as a robust and reliable source for the generation of therapeutic antibodies. While a vast diversity of library generation philosophies and selection strategies have been conceived, the power of molecular design offered by controlling the in vitro selection step is still to be recognized by a broader audience outside of the antibody engineering community. Here, we summarize some opportunities and achievements, e.g., the generation of antibodies which could not be generated otherwise, and the design of antibody properties by different panning strategies, including the adjustment of kinetic parameters.