AN ADENOVIRUS RECOMBINANT EXPRESSING THE SPIKE GLYCOPROTEIN OF PORCINE RESPIRATORY CORONAVIRUS IS IMMUNOGENIC IN SWINE

The full-length spike (S) gene of porcine respiratory coronavirus (PRC V) was inserted into the genome of human adenovirus type 5 downstream of the early transcription region 3 promoter. The recombinant virus re plicated in cultures of the swine testicle ST cell line and directed t he synthesis of S antigen with a maximum yield of approximately 26 mu g per 10(6) cells. The antigen was cell-associated except in the late phase of the infection, when a small amount(3.5 mu g per 10(6) cells) was released. The cell-associated antigen consisted of polypeptides of molecular mass 160kDa and 175kDa, comigrating with the authentic prec ursor S' and the mature S protein of PRCV, respectively. The extracell ular recombinant antigen corresponded to the 175kDa mature protein. So me recombinant S protein was exposed on the cell surface and was recog nized by neutralization-mediating anti-S monoclonal antibodies. Piglet s, inoculated oronasally with the recombinant adenovirus vector develo ped PRCV-neutralizing serum antibodies and were partially protected ag ainst PRCV challenge, demonstrating the potential of live adenovirus a s vaccine vector.