Interactions between Cryptosporidium parvum and bovine corona virus during sequential and simultaneous infection of HCT-8 cells

Neonatal diarrhoea in calves is one of the major health problems in the cattle industry. Although co-infections are often associated with greater severity of disease, there is limited information on any impact on the pathogens themselves. Herein, we studied Cryptosporidium parvum and bovine coronavirus (BCoV) in human HCT-8 cells, inoculated either sequentially or simultaneously, to investigate any influence from the co-infections. Quantitative results from (RT)-qPCR showed that prior inoculation with either of the two pathogens had no influence on the other. However, the results from simultaneous co-inoculation showed that entry of viral particles was higher when C. parvum sporozoites were present, although elevated virus copy numbers were no longer evident after 24 h. The attachment of BCoV to the sporozoites was probably due to specific binding, as investigations with bovine norovirus or equine herpes virus-1 showed no attachment between sporozoites and these viruses. Flow cytometry results at 72 h post inoculation revealed that C. parvum and BCoV infected 1-11% and 10-20% of the HCT-8 cells, respectively, with only 0.04% of individual cells showing double infections. The results from confocal microscopy corroborated those results, showing an increase in foci of infection from 24 to 72 h post inoculation for both pathogens, but with few double infected cells. (C) 2021 The Author(s). Published by Elsevier Masson SAS on behalf of Institut Pasteur.

Automated summary

Neonatal diarrhea in calves is a major health problem in the cattle industry. This study investigated the influence of co-infections of Cryptosporidium parvum and bovine coronavirus (BCoV) in human HCT-8 cells. The results showed that prior inoculation with either pathogen had no influence on the other, but simultaneous co-inoculation increased the entry of viral particles when C. parvum sporozoites were present. Flow cytometry and confocal microscopy results indicated different infection patterns for the two pathogens in HCT-8 cells.