Clonal analysis of a human antibody response. III. Nucleotide sequences of monoclonal IgM, IgG, and IgA to rabies virus reveal restricted Vκ gene utilization, junctional VκJκ and VλJλ diversity, and somatic hypermutation

In previous work, we generated four IgM, five IgG1, and one IgA1 mAbs to rabies virus using B cells from four subjects vaccinated with inactivated rabies virus, a thymus-dependent (TD) mosaic Ag, and sequenced the mAb V(H)DJ(H) genes. Here, we have cloned the VκJκ and VλJλ genes to complete the primary structure of the Ag-binding site of these mAbs. While the anti- rabies virus mAb selection of Vλ genes (2e.2.2 twice, DPL11, and DPL23) reflected the representation of the VA genes in the human haploid genome (stochastic utilization), that of Vκ genes (O2/O12 twice, O8/O18, A3/A19, A27, and L2) did not (p = 0.0018) (nonstochastic utilization). Furthermore, the selection of both Vκ and Vλ genes by the anti-rabies virus mAbs vastly overlapped with that of 557 assorted VκJκ rearrangements, that of 253 VλJλ rearrangements in λ-type gammopathies, and that of other Abs to thymus-dependent Ags, including 23 anti-HIV mAbs and 51 rheumatoid factors, but differed from that of 43 Abs to Haemophilus influenzae type b polysaccharide, a prototypic thymus-independent (TI) Ag. The anti-rabies virus mAb VκJκ and VλJλ segments displayed variable numbers of somatic mutations, which, in mAb58 and the virus-neutralizing mAb57, entailed a significant concentration of amino acid replacements in the complementarity- determining regions (p = 0.0028 and p = 0.0023, respectively), suggesting a selection by Ag. This Ag-dependent somatic selection process was superimposed on a somatic diversification process that occurred at the stage of B cell receptor for Ag rearrangement, and that entailed V gene 3' truncation and N nucleotide additions to yield heterogeneous CDR3s.