Attenuated IBV With Extended Cell and Tissue Tropism

The patent replaces the expensive and cumbersome embryonated chicken egg system with cell culture systems that use disposable cell lines (such as DF-1, EB66, PBS-12SF, BHK, HEK 293T, Vero, MA104, and RK13 cells). This substitution eliminates the need for maintaining complex egg incubation infrastructure and allows for more economical vaccine production while achieving comparable or superior propagation efficiency.

The patent achieves extended cell line tropism not by changing the viral spike protein sequence (which would compromise protection efficacy), but by changing the propagation parameters - specifically by adapting the virus to replicate in various cell culture systems. The IBV vaccine strain is propagated in multiple cell lines (DF-1, EB66, PBS-12SF, BHK, HEK 293T, Vero, MA104, RK13) to select for variants with broad tropism while maintaining the original spike protein sequence that ensures protection against diverse genotypes.

The patent uses cell culture systems as intermediary hosts for virus propagation, serving as a safe intermediate step between the original virus isolation and the final vaccine formulation. The cell culture-adapted virus serves as an intermediary that maintains attenuation characteristics while enabling scalable production. This intermediary system allows for controlled passage numbers and includes built-in safety mechanisms through cell culture monitoring that prevent over-passage and loss of attenuation.