High-resolution analysis of the B cell repertoire before and after polyethylene glycol fusion. Rattus norvegicus breed:OmniRat

The generation of therapeutic monoclonal antibodies (mAbs) largely relies on the fusion efficiency of antigen-specific B cells producing human immunoglobulin (Ig) with myeloma cells. We performed a high-resolution analysis of the B cell repertoire before and after polyethylene glycol (PEG)-fusion using high-throughput sequencing of the Ig heavy chain (IgH) repertoire. Transgenic rats carrying human Ig heavy and light loci (OmniRat) were immunized with measles virus (MV) to generate human mAbs. We compared the IgH repertoire of the lymph nodes and of the hybridoma library using the sequences of the MV-specific hybridoma clones as a reference set with known specificity. We showed that the efficient generation of mAbs is due to a fusion process that is highly selective for rare antigen-specific B cells in the regional lymph nodes and not for in vivo expanded B cell populations. Antibodies of particular relevance in vivo may therefore be missed during classical hybridoma production.