Adherence of bovine viral diarrhea virus to bovine oocytes and embryos with a hardened zona pellucida cultured in vitro.

The purpose of this study was to investigate the adherence of bovine viral diarrhea virus (BVDV) to bovine mature, or immature, cumulus-free oocytes and to in vitro fertilized embryos, maintained in vitro in a ligated bovine oviduct to allow for the hardening of the zona pellucida. Incubation of the oocytes and embryos in the oviduct for 5 h caused hardening of the zona pellucida as measured by resistance to pronase digestion (which increased from approximately 3 min to 7 h; P > 0.001). However, there was no difference between the number of infected oocytes and embryos (n = 965 in 193 samples) following experimental exposure to BVDV regardless of whether or not they were previously incubated in the oviduct (P > 0.05). It was concluded that the modification of the proteolytic resistance properties of the zona pellucida during in vitro oviductal incubation did not influence the adherence of BVDV to zona pellucida of oocytes or in vitro fertilized embryos.