Engineering of the high-affinity chemokine CXCL13 to screen CXCR5 antagonists to treat cancer and autoimmune diseases.

Abstract

CXCR5 (CD185 or Burkitt lymphoma receptor 1) is a receptor activated by the chemokine CXCL13. This G-protein coupled receptor (GPCR) is expressed on T-follicular helper cells (Tfh), B cells, and CD4+ T cells in secondary lymphoid organs such as the spleen, lymph nodes, and Peyer's patches. CXCR5 is involved in Tfh cell migration to B cell follicles, where they interact with B cells to initiate the humoral immune response. Aberrant activation of the CXCR5-CXCL13 signalling axis contributes to autoimmune conditions, including multiple sclerosis, systemic lupus erythematosus, and rheumatoid arthritis. The CXCL13:CXCR5 axis is also involved in angioimmunoblastic T-cell lymphoma (AITL). Cancer and normal cells within the tumor microenvironment secrete CXCL13 to contribute to the proliferation and metastasis of these lymphomas. Antagonists of CXCR5 would be potential drug molecules to reduce the severity of cancers and autoimmune diseases. Protein engineering can make CXCL13 an effective antagonist by modifying the N-terminal sequence, known to interact with a cavity among transmembrane helices in CXCR5 and induce signaling. About 168,000 variant CXCL13 sequences were expressed by a phage display library, reduced to 98 potential CXCR5 antagonists after assays to identify inhibitors by bioinformatics, and experimentally tested for antagonism. The most potent antagonist will be further validated for its ability to prevent cell migration and cancer cell survival by fusing to IgG and using in CAR T therapy.