Related Experiment Video
Updated: Jul 16, 2025
Peptide Scanning-assisted Identification of a Monoclonal Antibody-recognized Linear B-cell Epitope
Published on: March 24, 2017
Identification of the glycopeptide epitope recognized by a protective Cryptosporidium monoclonal antibody
Seema Bhalchandra1, Koen Gevers2, Jamie Heimburg-Molinaro3
1Division of Geographic Medicine and Infectious Diseases, Tufts Medical Center , Boston, Massachusetts, USA.
Insights
A monoclonal antibody, 4E9, targeting a specific epitope on Cryptosporidium parasites, shows promise in treating cryptosporidiosis in calves. This finding could lead to new vaccines and therapies for this significant diarrheal disease.
Area of Science:
- Parasitology and Immunology
- Infectious Diseases
- Vaccine Development
Background:
- Cryptosporidium species cause severe diarrheal disease in children and immunocompromised individuals, and neonatal calves.
- Current treatments for cryptosporidiosis are inadequate, and no vaccine is available.
- Previous work identified a target epitope on Cryptosporidium parvum glycoproteins (gp40, gp900) recognized by monoclonal antibody 4E9.
Purpose of the Study:
- To evaluate the therapeutic potential of monoclonal antibody 4E9 against Cryptosporidium infection in vivo.
- To characterize the 4E9 epitope on Cryptosporidium parasites.
- To explore the implications of the 4E9 epitope for vaccine and therapy development.
Main Methods:
- A calf challenge model was used to assess the in vivo efficacy of 4E9.
- Glycan and glycopeptide microarrays were employed to define the 4E9 epitope.
- Immunohistochemistry localized the epitope on parasite stages.
Main Results:
- Monoclonal antibody 4E9 ameliorated disease in a calf model of Cryptosporidium infection.
- The 4E9 epitope is present on both Cryptosporidium parvum and Cryptosporidium hominis.
- The epitope is a glycopeptide motif (S*/T*-X-S*/T*) found on mucin-like glycoproteins, present on the parasite's plasma membrane and dense granules.
Conclusions:
- Monoclonal antibody 4E9 demonstrates therapeutic potential against cryptosporidiosis.
- The defined 4E9 epitope provides a target for developing novel vaccines and immune-based therapies.
- Understanding the epitope's structure is crucial for advancing treatments for this significant zoonotic pathogen.
Abstract:
Cryptosporidium species are a leading cause of pediatric diarrheal disease and death in low- and middle-income countries and pose a particular threat to immunocompromised individuals. As a zoonotic pathogen, Cryptosporidium can have devastating effects on the health of neonatal calves. Despite its impact on human and animal health, consistently effective drug treatments for cryptosporidiosis are lacking and no vaccine is available. We previously showed that C. parvum mucin-like glycoproteins, gp40, and gp900 express an epitope identified by a monoclonal antibody 4E9. 4E9 neutralized C. parvum infection in vitro as did glycan-binding proteins specific for the Tn antigen (GalNAc-α1-S/T). Here, we show that 4E9 ameliorates disease in vivo in a calf challenge model. The 4E9 epitope is present on C. hominis in addition to C. parvum gp40 and gp900 and localizes to the plasma membrane and dense granules of invasive and intracellular stages. To characterize the epitope recognized by 4E9, we probed a glycan array containing over 500 defined glycans together with a custom-made glycopeptide microarray containing glycopeptides from native mucins or C. parvum gp40 and gp15. 4E9 exhibited no binding to the glycan array but bound strongly to glycopeptides from native mucins or gp40 on the glycopeptide array, suggesting that the antibody epitope contains both peptide and glycan moieties. 4E9 only recognized glycopeptides with adjacent S or T residues in the motif S*/T*-X-S*/T* where X = 0 or 1. These data define the 4E9 epitope and have implications for the inclusion of the epitope in the development of vaccines or other immune-based therapies.
