B cells expressing IgM B cell receptors of HIV-1 neutralizing antibodies discriminate antigen affinities by sensing binding association rates.
HIV-1 envelope (Env) proteins designed to induce neutralizing antibody responses allow study of the role of affinities (equilibrium dissociation constant [KD]) and kinetic rates (association/dissociation rates) on B cell antigen recognition. It is unclear whether affinity discrimination during B cell activation is based solely on Env protein binding KD and whether B cells discriminate among proteins of similar affinities that bind with different kinetic rates. Here, we use a panel of Env proteins and Ramos B cell lines expressing immunoglobulin M (IgM) B cell receptors (BCRs) with specificity for CD4-binding-site broadly neutralizing antibodies to study the role of antigen binding kinetic rates on both early (proximal/distal signaling) and late events (BCR/antigen internalization) in B cell activation. Our results support a kinetic model for B cell activation in which Env protein affinity discrimination is based not on overall KD but on sensing of association rate and a threshold antigen-BCR half-life.
Hossain, MA; Anasti, K; Watts, B; Cronin, K; Derking, R; Groschel, B; Kane, AP; Edwards, RJ; Easterhoff, D; Zhang, J; Rountree, W; Ortiz, Y; Saunders, K; Schief, WR; Sanders, RW; Verkoczy, L; Reth, M; Alam, SM
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