Deep sequencing of the IgH locus in CVID reveals global alterations in central and peripheral B cell development (P3329)

Abstract

Abstract Common Variable Immunodeficiency (CVID) is the most common clinically important primary immune deficiency, affecting roughly 1:25,000 persons and characterized by hypogammaglobulinemia and loss of specific antibody (Ig) production. The causes are poorly understood, but defective B cell activation has been demonstrated. Examining the Ig repertoires of patients could help elucidate early and late B cell maturation. Rearranged Ig heavy chains were sequenced on the Roche 454 for 78 well-characterized patients, with or without non-infectious complications, and 27 healthy controls. Reads were parsed into component genes and structural segments using the iHMMune-align algorithm. Comparison of the repertoires was done in R, or with a combination of SQL and Prism. CVID subjects consistently showed altered central B cell development, with fewer in-frame sequences (85 v 86%, p<0.01), shorter in-frame CDR3 segments (48.1 v 49.6bp, p<0.0001), and VDJ recombination biased away from nontemplated and towards germline-encoded nucleotides. Peripheral somatic hypermutation was also defective in CVID, with fewer mutations both overall (0.6 v 1.5% of V bases, p<0.0001) and in mutated sequences (3.1 v 5.8%, p<0.0001), and fewer in-frame mutated sequences (83.4 v 89.2%, p<0.0001). CVID subjects with <0.55% circulating isotype switched memory B cells showed more severe defects. Defective B cell activation has been shown in CVID; here we demonstrate intrinsic differences in early B cell development.