Veterinary session

In the case of conventional virus vaccines, pathogens are produced on monolayer cell lines, primary tissue cultures, or embryonated eggs. In all cases, the aim is to maximise virus yield.

The quality of the eggs used for vaccine production may differ, the multiplication potential of the viruses may also be diverse, and various other environmental factors may contribute to the yield of vaccine viruses, such as the stagnation of the incubation temperature of the embryo in the hatchery.

The hatching of embryonated hen eggs can require a large area in a vaccine factory, and therefore companies usually choose to supply eggs of the right age for the multiplication of a given virus instead of a zero-day-old embryo for optimal production. „Non-zero” day old embryo eggs must be transported from hatchery temperature in the shortest possible time, hence eggs are transported in temperature controlled vehicles. Unloading is carried out mechanically, and the eggs are placed in a resting area at a temperature of 37 ̊C.

The aim of our experiment is to determine how the storage of the eggs at room temperature between the transport vehicle and the resting area affect the amount of virus inoculated. Eggs placed in the transport vehicle can maintain it’s temperature for a long time due to the eggs volume, Our experiment may be useful in an industrial protocol for obtaining the best virus yield.

For this purpose, we performed 3 experiments with 200 9-day-old embryonated chicken eggs. Two trays of eggs were incubated (37 0 ̊C) immediately upon arrival, two more trays after one hour and out of the remaining eggs 2 were incubated after 4 hours and one after 6 hours at room temperature. Virus inoculation was performed after a minimum of 24 hours. After an incubation period of 72 hours, the eggs were placed in the refrigerator overnight (minimum 8 h), after which the allantois was harvested. Before each procedure, all eggs were lamped and the weight of the 6 marked eggs per tray was also determined. The first two batches of eggs contained brown-shelled eggs and the third batch contained white-shelled ones. The antigenicity of the collected viruses was confirmed by virological testing.

Based on the allantois yield, we found that waiting six hours in the first test significantly reduced the allantois yield (especially in thermostat B). In the other two cases, no significant difference in allantois yield was found (considering the function of the two different thermostats and the time that the eggs were left at room temperature). Based on these results, it was concluded that the amount of allantois that can be used will be less during the six-hour waiting period, whereas waiting four hours at room temperature does not cause such changes.