Authors

S Balogun¹; N Hall³; M Van Roosmalen⁴; G Vertenten⁴; KM Tyler²;  ¹ University of East Anglia, UK;  ² Norwich Medical School at UEA, UK;  ³ Earlham Institute, UK;  ⁴ MSD Animal Health, UK

Discussion

Background & objective: Cryptosporidium spp. are among the leading causes of diarrhoeal disease worldwide, second only to rotavirus. In humans, cryptosporidiosis accounts for approximately 200,000 deaths annually, disproportionately affecting children under five years of age and immunocompromised individuals. In livestock, the disease imposes substantial economic losses estimated at billions of USD each year. Despite its major impact on global public and animal health, highly effective therapeutics and vaccines remained unavailable until recently. Recently a licensed livestock vaccine was developed, designed to confer passive immunity through bovine colostrum targeting the Cryptosporidium parvum GP40 antigen. Although this vaccine significantly reduces disease severity, it does not prevent parasite transmission or oocyst shedding. This study investigated the mechanisms underlying passive immunity mediated by bovine colostrum using an in vitro infection model alongside microbiome profiling of vaccinated and unvaccinated calves. M&M: A blocking assay was performed using Colo-680N cells infected with excysted C. parvum oocysts. The binding and inhibitory activity of hyperimmune bovine colostrum (HBC), non-immune colostrum (NC), and a monoclonal anti-GP40 antibody (4E9) were evaluated using fixed-cell immunofluorescence microscopy. Results: At a single stock concentration, both HBC and NC demonstrated significant blocking activity, indicating inherent anti-cryptosporidial properties in both preparations. However, serial dilution experiments revealed distinct concentration-dependent differences, with enhanced inhibitory activity observed in HBC at specific thresholds. These findings support antigen-specific vaccine-induced effects, while the activity observed in NC likely reflects pre-existing, non-specific anti-Cryptosporidium antibodies resulting from prior environmental exposure of dams.