Polymorphic Region-Specific Antibody for Evaluation of Affinity-Associated Profile of Chimeric Antigen Receptor.

Antibody applications in cancer immunotherapy involve diverse strategies, some of which redirect T cell-mediated immunity via engineered antibodies. Affinity is a trait that is crucial for these strategies, as optimal affinity reduces unwanted side effects while retaining therapeutic function. Antibody-antigen pairs possessing a broad affinity range are required to define optimal affinity and to investigate the affinity-associated functional profiles of T cell-engaging strategies such as bispecific antibodies and chimeric antigen receptor-engineered T cells. Here, we demonstrate the unique binding characteristic of the developed antibody clone MVR, which exhibits robust binding to B-lymphoid cell lines. Intriguingly, MVR specifically recognizes the highly polymorphic human leukocyte antigen (HLA)-DR complex and exhibits varying affinities that are dependent upon the allele type. Remarkably, MVR binds to the conformational epitope that consists of two hypervariable regions. As an application of MVR, we demonstrate an MVR-engineered chimeric antigen receptor (CAR) that elicits affinity-dependent function in response to a panel of target cell lines that express different alleles. This tool evaluates the effect of affinity on cytotoxic killing, polyfunctionality, and activation-induced cell death of CAR-engineered T cells. Collectively, MVR exhibits huge potential for the evaluation of the affinity-associated profile of T cells that are redirected by engineered antibodies.