IGH V3-23*01 and its allele V3-23*03 differ in their capacity to form the canonical human antibody combining site specific for the capsular polysaccharide of Haemophilus influenzae type b.
The IGH V3-23*01 gene is used in the formation of the canonical combining site which dominates the human antibody repertoire to the Haemophilus influenzae type b (Hib) polysaccharide (PS). An allele of the human IGH V3-23*01 gene, known as V3-23*03, differs from V3-23*01 in nine bases, eight of which are located in the second complementarity determining region. These eight differences encode five amino acid substitutions. In this study we investigated whether the V3-23*03 sequence polymorphism affected Hib PS binding. We constructed two Fab fragments that had the canonical Hib PS combining site VH-VL configuration but that had either V3-23*01 or V3-23*03. Radioantigen binding assay showed that on a concentration basis the V3-23*03 Fab was 20-fold more effective in binding Hib PS than the V3-23*01 Fab. The V3-23*03 Fab was 4-fold more effective than the V3-23*01 Fab in mediating facilitated bactericidal activity against Hib organisms. These findings identify a functional consequence of V3-23 allelism, and suggest that utilization of the V3-23*03 gene in the human Hib PS repertoire would generate canonical antibodies with higher affinity and protective efficacy than canonical antibodies utilizing V3-23*01. Thus, IGH V gene allelic variation has the potential to impact the generation of protective immunity to Hib.
Liu
Leyu
L
Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, CA 94609, USA.
Lucas
Alexander H
AH
D000595:Amino Acid Sequence; D016667:Bacterial Capsules; D001483:Base Sequence; D001665:Binding Sites; D018073:Haemophilus Vaccines / Q000276:immunology*; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D008969:Molecular Sequence Data; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D017422:Sequence Analysis, DNA
D018073:Haemophilus Vaccines; C044237:Haemophilus influenzae type b polysaccharide vaccine; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D011135:Polysaccharides, Bacterial