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.