B Cell Receptor Signaling Sets Boundaries for Selection of Broadly Neutralizing Antibody Functional Mutations

Singh, A.; Anasti, K.; Itallie, E. V.; Newman, A.; Kane, A. P.; Barr, M.; Parks, R.; Venkatayogi, S.; Tian, M.; Saunders, K.; Henderson, R.; Cain, D. W.; Alt, F. W.; Haynes, B. F.; Verkoczy, L.; Wiehe, K.; Alam, S. M.

doi:10.64898/2026.08.13.744461

bioRxiv · 10.64898/2026.08.13.744461

B Cell Receptor Signaling Sets Boundaries for Selection of Broadly Neutralizing Antibody Functional Mutations

Singh, A.·Anasti, K.·Itallie, E. V.·Newman, A.·Kane, A. P.·Barr, M.·Parks, R.·Venkatayogi, S.·Tian, M.·Saunders, K.·Henderson, R.·Cain, D. W.·Alt, F. W.·Haynes, B. F.·Verkoczy, L.·Wiehe, K.·Alam, S. M.

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Abstract

B cell signaling is required for germinal center (GC) selection and synergizes with T cell-help leading to differentiation into effector cells and a protective antibody response. Here, we studied the relationship between B cell signaling and the selection of functional mutations in a humanized mouse model of a CD4 binding-site specific HIV-1 broadly neutralizing antibody precursor. While BCR signaling increased with antigen affinity, immunization-induced frequency of a functional mutation was inversely related to affinity and favored a gain in association rate. Antigen-specific GC B cells and key mutation frequency were higher in the mid-affinity (0.5 - 5M) than in either the higher or lower affinity group, and were consistent with the significantly higher serum neutralization titers in the mid-range group. Our studies show that BCR signaling imposes boundaries (upper/lower) for selection of antibody functional mutations and support a "Goldilocks Zone" model that defines the favored BCR signaling strength for GC selection.

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Singh, A., Anasti, K., Itallie, E. V., Newman, A., Kane, A. P., Barr, M., Parks, R., Venkatayogi, S., Tian, M., Saunders, K., Henderson, R., Cain, D. W., Alt, F. W., Haynes, B. F., Verkoczy, L., Wiehe, K., Alam, S. M.. 2026-08-19. B Cell Receptor Signaling Sets Boundaries for Selection of Broadly Neutralizing Antibody Functional Mutations. https://doi.org/10.64898/2026.08.13.744461

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