TY - JOUR
T1 - Molecular basis for immunoglobulin M specificity to epitopes in Cryptococcus neoformans polysaccharide that elicit protective and nonprotective antibodies
AU - Nakouzi, A.
AU - Valadon, P.
AU - Nosanchuk, J.
AU - Green, N.
AU - Casadevall, A.
PY - 2001
Y1 - 2001
N2 - The protective efficacy of antibodies (Abs) to Cryptococcus neoformans glucuronoxylomannan (GXM) is dependent on Ab fine specificity. Two clonally related immunoglobulin M monoclonal Abs (MAbs) (12A1 and 13F1) differ in fine specificity and protective efficacy, presumably due to variable (V)-region sequence differences resulting from somatic mutations. MAb 12A1 is protective and produces annular immunofluorescence (IF) on serotype D C. neoformans, while MAb 13F1 is not protective and produces punctate IF. To determine the Ab molecular determinants responsible for the IF pattern, site-directed mutagenesis of the MAb 12A1 heavy-chain V region (VH) was followed by serological and functional studies of the various mutants. Changing two selected amino acids in the 12A1 VH binding cavity to the corresponding residues in the 13F1 VH altered the IF pattern from annular to punctate, reduced opsonic efficacy, and abolished recognition by an antiidiotypic Ab. Analysis of the binding of the various mutants to peptide mimetics revealed that different amino acids were responsible for GXM binding and peptide specificity. The results suggest that V-region motifs associated with annular binding and opsonic activity may be predictive of Ab efficacy against C. neoformans. This has important implications for immunotherapy and vaccine design that are reinforced by the finding that GXM and peptide reactivities are determined by different amino acid residues.
AB - The protective efficacy of antibodies (Abs) to Cryptococcus neoformans glucuronoxylomannan (GXM) is dependent on Ab fine specificity. Two clonally related immunoglobulin M monoclonal Abs (MAbs) (12A1 and 13F1) differ in fine specificity and protective efficacy, presumably due to variable (V)-region sequence differences resulting from somatic mutations. MAb 12A1 is protective and produces annular immunofluorescence (IF) on serotype D C. neoformans, while MAb 13F1 is not protective and produces punctate IF. To determine the Ab molecular determinants responsible for the IF pattern, site-directed mutagenesis of the MAb 12A1 heavy-chain V region (VH) was followed by serological and functional studies of the various mutants. Changing two selected amino acids in the 12A1 VH binding cavity to the corresponding residues in the 13F1 VH altered the IF pattern from annular to punctate, reduced opsonic efficacy, and abolished recognition by an antiidiotypic Ab. Analysis of the binding of the various mutants to peptide mimetics revealed that different amino acids were responsible for GXM binding and peptide specificity. The results suggest that V-region motifs associated with annular binding and opsonic activity may be predictive of Ab efficacy against C. neoformans. This has important implications for immunotherapy and vaccine design that are reinforced by the finding that GXM and peptide reactivities are determined by different amino acid residues.
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U2 - 10.1128/IAI.69.5.3398-3409.2001
DO - 10.1128/IAI.69.5.3398-3409.2001
M3 - Article
C2 - 11292763
AN - SCOPUS:0035055412
SN - 0019-9567
VL - 69
SP - 3398
EP - 3409
JO - Infection and immunity
JF - Infection and immunity
IS - 5
ER -