The goal of Biosystems International is to characterize the human plasma epitome using monoclonal antibody (mAb) libraries targeting all possible epitops of natural human plasma proteome. Due to our technology the antigen specificity of our mAb libraries are not known during the screening and selection steps.
Beside the antigen protein ID, alternative methods exist to characterize mAbs, for example one of them is to find peptide epitope/mimotope IDs. Using the phage display technique in this study we were able to determine the epitope ID for approximately 80 % of the screened (altogether more than 400) mAbs in spite the fact that the used phage library displays only a fraction of the possible peptide combinations. The obtained 12-mer peptide sequences of each screened mAbs were first ranked and then unique sequence(s) or motif(s) were determined. Unique sequence(s) of each antibody were used to determine the epitope level redundancy. We found that less than 5 % of successfully tested mAbs showed 50% or higher redundancy.
We applied Biacore technology utilizing phages and we could demonstrate the affinity of peptides to their specific mAbs, however the reproducibility of KD values was poor. Using streptavidin coated biochips to immobilize biotin labeled synthetic peptides in the Biacore experiments not only resolved reproducibility, but beside the affinity, peptide specificity could also be demonstrated. Specificity of these peptides to the corresponding mAbs was confirmed with ELISA experiments in streptavidin coated setup as well. Thus as a next step we tested 121 peptides (N terminal BioTide linker) in peptide array experiments. We found that in this setup 23 peptides recognized only one mAb out of the tested 16. The same 121 peptides (with biotin on the N terminal of BioTide linker) were tested in ELISA assays in similar setup, showing slightly different pattern of selectvity. The comparison of the selective recognition of 2 peptides indicated the importance of various and differently positioned linkers.
In conclusion we demonstrated that 12-mer peptides selected by phage display are useful tools to determine epitope level redundancy of mAb libraries or test specificity and affinity with either Biacore, or ELISA if special care is taken regarding the linker dependent flexibility of these short peptides in the experimental plan.
This work was supported by the National Office for Research and Technology of Hungary (TECH-09-A1-2009-0113; mAB-CHIC).
József Lázár1, Angéla Berki Pál1, Katalin Élesné Tóth1, Beáta Flachner2, István Hajdú2, Sándor Cseh2, László Takács1, István Kurucz1
1Biosystems International Ltd, Debrecen, Hungary
2TargetEx Ltd, Dunakeszi, Hungary
Biosystems International (BSI) a biotech- nology company focused on the development of novel monoclonal antibody-based diagnostics for cancer and metabolic diseases has established a licensing agreement with the Lohocla Research Corporation for the use of BSI’s patented monoclonal antibody proteo- mics platform for the discovery of novel alcoholism liver disease biomarkers in blood.
Biosystems International and Microbiochips sign collaboration agreement to commer- cialize PlasmaScan™ antibody microarray products.