Mouse to Human Conversion

Many new discovery projects begin with a mouse monoclonal antibody that has properties desired in a fully human therapeutic. Furthermore, having access to a mouse monoclonal can facilitate in vivo testing in animal models. For this reason, we have developed efficient strategies to quickly convert mouse antibodies to fully human while preserving specificity and function.

As outlined in the flow chart below, a typical conversion project begins with mouse heavy and light variable genes cloned directly from a hybridoma and expressed as chimeric genes with human constant regions in vaccinia virus. These chimeric chains are then used to screen for their human complement. Specifically, chimeric heavy chain is used to screen a library of fully human light chains and vice versa.

Mouse to human screening is depicted below and is accomplished through expression of antibody on the surface of a host cell followed by incubation with fluorescent labeled antigen. Cells expressing antibodies that bind to antigen are separated via FACS (fluorescence-activated cell sorting). Importantly, the recombinant vaccinia virus encoding the heavy and light chains of interest can then be harvested from the sorted cells, amplified and used in a second or even a third round of enrichment as necessary. Ultimately, individual heavy and light chain clones are picked as viral plaques and interrogated through a series of experiments designed to exclude low affinity and non-specific antibodies.

Once lead antibodies are selected, they are expressed in CHO independently of vaccinia virus and purified using standard protocols. They are then compared to the original mouse antibody, the chimeric, and the intermediates generated during screening.