The
supernatants were then inoculated into the allantois sac of five
fertile 10-day-old specific-pathogen-free (SPF) chicken eggs. The
eggs were incubated at 37 C for 5 days. Eggs containing dead or
dying embryos and all eggs remaining at the end of the incubation
period were first chilled to 4 C and then the allantois fluids were
harvested.