but induces protective immunity

Highlights
•  The reverse genetic operating systems of IBV H120 and IBYZ strains were created.
•  We constructed rH120-S1/YZ strain, based on the backbone of the H120 vaccine strain, with the S1 gene replaced with that of the QX-like nephropathogenic strain, ck/CH/IBYZ/2011.
•  We demonstrated that rH120-