Our study also showed that the abundance of some glycolytic enzymes, including phosphoenolpyruvate carboxykinase (PCK1), mitochondrial phosphoenolpyruvate carboxykinase (PCK2), pyruvate kinase, and alpha-enolase, were increased significantly in the early stage of infection with both the highly virulent and the attenuated IBV strain. The gene discussed is PCK1; the disease is infection.