Repertoire of human antibodies against the polysaccharide capsule of Streptococcus pneumoniae serotype 6B

Abstract

We examined the repertoire of antibodies to Streptococcus pneumoniae 6B capsular polysaccharide induced with the conventional polysaccharide vaccine in adults at the molecular level two ways. In the first, we purified from the sera of seven vaccinees antipneumococcal antibodies and determined their amino acid sequences. Their VH regions are mainly the products of VH3 family genes (candidate genes, 3-23, 3-07, 3-66, and 3-74), but the product of a VH1 family gene (candidate gene, 1-03) is occasionally used. All seven individuals have small amounts of polyclonal kappa+ antibodies (Vkappa1 to Vkappa4 families), although kappa+ antibodies are occasionally dominated by antibodies formed with the product of the A27 Vkappa gene. In contrast, lambda+ anti-6B antibodies are dominated by the antibodies derived from one of 3 very similar Vlambda2 family genes (candidate genes, 2c, 2e, and 2a2) and Clambda1 gene product. The Vlambda2(+) antibodies express the 8.12 idiotype, which is expressed on anti-double-stranded-DNA antibodies. In one case, Vlambda is derived from a rarely expressed Vlambda gene, 10a. In the second approach, we studied a human hybridoma (Dob1) producing anti-6B antibody. Its VH region sequence is closely related to those of the 3-15 VH gene (88% nucleotide homology) and JH4 (92% homology). Its VL region is homologous to the 2a2 Vlambda2 gene (91%) and Jlambda1/Clambda1. Taken together, the V region of human anti-6B antibodies is commonly formed by a VH3 and a Vlambda2 family gene product.

FIG. 1

Relationship between the amount of anti-6B antibodies (Ab) expressing the 8.12 idiotype and the amount of anti-6B antibodies expressing λ light chain for volunteers vaccinated with a PS vaccine (B), compared with the relationship between total anti-6B and anti-6B antibodies expressing either κ or λ chain (A). Donor P26, who was found to express antibody derived from a Vλ10 family gene, is indicated with an arrow. Panel A was reproduced with permission of the publisher (J. Infect. Dis. 174:75–82, 1996).

FIG. 2

Amino acid sequences of the V region of the light chain of anti-6B antibodies expressing the λ light chain. Dayhoff amino acid notation and the residue numbering system of Kabat et al. (17) are used. X indicates no residue identified; the X at position 22 of P26λ is likely an invariant cysteine not identifiable by our sequencing method. The lowercase letter denotes the recovery of a smaller than expected amount of amino acid during the Edman degradation cycle; the solid line denotes identity to the reference sequence at the top. Tryptophan at positions 38, 148, and 186 are inferred by the cleavage method.

FIG. 3

Amino acid sequences of the V region of the light chain of anti-6B antibodies expressing the κ light chain. Symbols are as in Fig. 2.

FIG. 4

Amino acid sequences of the V region of the heavy chain of anti-6B antibodies. Symbols are as in Fig. 2.

FIG. 5

cDNA sequences of VH (A) and VL (B) regions of Dob1. The first lines denote the VH and VL domains as assigned by Kabat et al. (17). The third lines denote the reference DNA sequences for the heavy and light chains, which were based on the sequences of VH gene 3-15 (DP-38) (GenBank accession no. Z12338), JH4 gene (Z14191), IgG2 gene (J00230), VL gene 2a2 (Z73664), and Jλ1 and Cλ1 genes (X51755). The second lines denote amino acids translated from the reference sequences. The fourth and fifth lines, respectively, denote cDNA sequences of Dob1 VH and VL regions and their amino acid translations. The fifth lines show only the translated amino acids of Dob1 cDNAs that are different from those of the reference sequences.

FIG. 5

cDNA sequences of VH (A) and VL (B) regions of Dob1. The first lines denote the VH and VL domains as assigned by Kabat et al. (17). The third lines denote the reference DNA sequences for the heavy and light chains, which were based on the sequences of VH gene 3-15 (DP-38) (GenBank accession no. Z12338), JH4 gene (Z14191), IgG2 gene (J00230), VL gene 2a2 (Z73664), and Jλ1 and Cλ1 genes (X51755). The second lines denote amino acids translated from the reference sequences. The fourth and fifth lines, respectively, denote cDNA sequences of Dob1 VH and VL regions and their amino acid translations. The fifth lines show only the translated amino acids of Dob1 cDNAs that are different from those of the reference sequences.