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Peptide epitopes recognized by a human anti-cryptococcal glucuronoxylomannan antibody
H Zhang1, Z Zhong, L A Pirofski
1Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Infection and Immunity
|April 1, 1997
Summary
Researchers identified a specific peptide sequence that mimics Cryptococcus neoformans glucuronoxylomannan (GXM) epitopes. This finding is crucial for developing new antibody therapies against cryptococcal meningitis in AIDS patients, especially when standard antifungals fail.
Area of Science:
- Immunology and Infectious Diseases
- Microbial Pathogenesis
- Vaccine Development
Background:
- Cryptococcus neoformans meningitis affects 6-8% of individuals with AIDS, often inadequately treated by existing antifungal agents due to profound immunosuppression.
- Immunotherapy, including antibody therapy, is a promising approach for cryptococcal meningitis in AIDS patients.
- Human monoclonal antibodies (MAbs), like 2E9, elicited by the glucuronoxylomannan-tetanus toxoid (GXM-TT) vaccine, show functional activity but their specific targets and protective roles are unclear.
Purpose of the Study:
- To identify specific epitopes on Cryptococcus neoformans glucuronoxylomannan (GXM) recognized by human anti-GXM antibodies.
- To investigate the potential of identified peptide epitopes as mimotopes for developing novel immunotherapeutic strategies against cryptococcosis.
Main Methods:
- Screening of a random decapeptide phage display library using the human anti-GXM MAb 2E9.
- Enzyme-linked immunosorbent assay (ELISA) to select phages that bind to MAb 2E9 and inhibit MAb-GXM binding.
- Sequence analysis of selected phages and synthesis of inhibitory peptides for further binding inhibition assays.
Main Results:
- Phage display identified peptide inserts with a high frequency of QTGLD residues, particularly QTG/TL/D motifs, which effectively inhibited MAb 2E9-GXM binding.
- Synthesized peptide 13 (GMDGT QLDRW) inhibited binding between MAb 2E9 and GXM, and also inhibited GXM binding by human anti-GXM antibodies from HIV-negative individuals.
- These results suggest that peptide 13 acts as a mimotope, mimicking GXM epitopes recognized by naturally occurring human antibodies.
Conclusions:
- The study successfully identified peptide mimotopes of Cryptococcus neoformans GXM epitopes recognized by human antibodies.
- Peptide 13 represents a potential mimotope for GXM epitopes targeted by protective human immune responses.
- These findings support the development of GXM-mimicking peptides for antibody-based immunotherapies against cryptococcal infections, particularly in immunocompromised individuals.