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  • Title: Aspects of antigen mimicry revealed by immunization with a peptide mimetic of Cryptococcus neoformans polysaccharide.
    Author: Valadon P, Nussbaum G, Oh J, Scharff MD.
    Journal: J Immunol; 1998 Aug 15; 161(4):1829-36. PubMed ID: 9712050.
    Abstract:
    We have recently identified peptide mimetics of the Cryptococcus neoformans capsular polysaccharide by screening phage display peptide libraries. 2H1, one of a large family of mAbs against the glucuronoxylomannan fraction (GXM), is highly protective and binds several peptide motifs. This study analyzes the immunologic properties of P601E (SYSWMYE), a peptide from the low affinity motif (W/YXWM/LYE) that has an extended cross-reactivity among anti-GXM mAbs and whose binding correlates with the protective potential of mAbs in experimental infection. P601E is a mimetic, since it competes for GXM binding to 2H1, but not a mimotope, since it does not elicit an anti-GXM response. Sequence analysis of 14 anti-P601E mAbs indicates that anti-P601E mAbs elicited in BALB/c mice have an order of homology with 2H1 of V kappa > J kappa >> V(H) > J(H) > D. Further screening of a peptide library with anti-P601E mAbs isolated peptides having a motif almost identical to the peptide motif selected by 2H1. When these results are compared to the crystal structure of a related peptide in complex with 2H1, there is a clear correlation between the ability to elicit V region components of 2H1 Ab and peptide association with the V region, suggesting that the completeness of the fit in the binding site is an important driving force for mimicry. As a consequence, improving affinity of a mimetic for the Ab binding site seems to be the most logical way to insure that all of the appropriate V region segments are elicited and that useful mimotopes are created.
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