@article {14125, title = {CXCL13 is a plasma biomarker of germinal center activity.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, year = {2016}, month = {2016 Feb 23}, abstract = {Significantly higher levels of plasma CXCL13 [chemokine (C-X-C motif) ligand 13] were associated with the generation of broadly neutralizing antibodies (bnAbs) against HIV in a large longitudinal cohort of HIV-infected individuals. Germinal centers (GCs) perform the remarkable task of optimizing B-cell Ab responses. GCs are required for almost all B-cell receptor affinity maturation and will be a critical parameter to monitor if HIV bnAbs are to be induced by vaccination. However, lymphoid tissue is rarely available from immunized humans, making the monitoring of GC activity by direct assessment of GC B cells and germinal center CD4(+) T follicular helper (GC Tfh) cells problematic. The CXCL13-CXCR5 [chemokine (C-X-C motif) receptor 5] chemokine axis plays a central role in organizing both B-cell follicles and GCs. Because GC Tfh cells can produce CXCL13, we explored the potential use of CXCL13 as a blood biomarker to indicate GC activity. In a series of studies, we found that plasma CXCL13 levels correlated with GC activity in draining lymph nodes of immunized mice, immunized macaques, and HIV-infected humans. Furthermore, plasma CXCL13 levels in immunized humans correlated with the magnitude of Ab responses and the frequency of ICOS(+) (inducible T-cell costimulator) Tfh-like cells in blood. Together, these findings support the potential use of CXCL13 as a plasma biomarker of GC activity in human vaccine trials and other clinical settings.}, issn = {1091-6490}, doi = {10.1038/nbt.3461}, author = {Havenar-Daughton, Colin and Lindqvist, Madelene and Heit, Antje and Wu, Jennifer E and Reiss, Samantha M and Kendric, Kayla and B{\'e}langer, Simon and Kasturi, Sudhir Pai and Landais, Elise and Akondy, Rama S and McGuire, Helen M and Bothwell, Marcella and Vagefi, Parsia A and Scully, Eileen and Tomaras, Georgia D and Davis, Mark M and Poignard, Pascal and Ahmed, Rafi and Walker, Bruce D and Pulendran, Bali and McElrath, M Juliana and Kaufmann, Daniel E and Crotty, Shane} }