An avirulent chimeric Pestivirus with altered cell tropism protects pigs against lethal infection with classical swine fever virus.
A chimeric Pestivirus was constructed using an infectious cDNA clone of bovine viral diarrhea virus (BVDV) [J. Virol. 70 (1996) 8606]. After deletion of the envelope protein E2-encoding region, the respective sequence of classical swine fever virus (CSFV) strain Alfort 187 was inserted in-frame resulting in plasmid pA/CP7_E2alf. After transfection of in vitro-transcribed CP7_E2alf RNA, autonomous replication of chimeric RNA in bovine and porcine cell cultures was observed. Efficient growth of chimeric CP7_E2alf virus, however, could only be demonstrated on porcine cells, and in contrast to the parental BVDV strain CP7, CP7_E2alf only inefficiently infected and propagated in bovine cells. The virulence, immunogenicity, and "marker vaccine" properties of the generated chimeric CP7_E2alf virus were determined in an animal experiment using 27 pigs. After intramuscular inoculation of 1 x 10(7) TCID(50), CP7_E2alf proved to be completely avirulent, and neither viremia nor virus transmission to contact animals was observed; however, CSFV-specific neutralizing antibodies were detected from day 11 after inoculation. In addition, sera from all animals reacted positive in an E2-specific CSFV-antibody ELISA, but were negative for CSFV-E(RNS)-specific antibodies as determined with a CSFV marker ELISA. After challenge infection with highly virulent CSFV strain Eystrup, pigs immunized with CP7_E2alf were fully protected against clinical signs of CSFV infection, viremia, and shedding of challenge virus, and almost all animals scored positive in a CSFV marker ELISA. From our results, we conclude that chimeric CP7_E2alf may not only serve as a tool for a better understanding of Pestivirus attachment, entry, and assembly, but also represents an innocuous and efficacious modified live CSFV "marker vaccine".
Reimann
Ilona
I
Federal Research Center for Virus Diseases of Animals, Institute of Infectology, D-17493 Greifswald-Insel Riems, Germany.
Depner
Klaus
K
Trapp
Sascha
S
Beer
Martin
M
D000818:Animals; D000914:Antibodies, Viral; D002417:Cattle; D002460:Cell Line; D006691:Classical Swine Fever / Q000097:blood / Q000517:prevention & control*; D006692:Classical Swine Fever Virus / Q000276:immunology; D001908:Diarrhea Viruses, Bovine Viral / Q000276:immunology / Q000502:physiology; D004195:Disease Models, Animal; D005822:Genetic Vectors / Q000276:immunology / Q000502:physiology; D007273:Injections, Intramuscular; D009500:Neutralization Tests; D010576:Pestivirus / Q000235:genetics / Q000502:physiology; D016865:Reassortant Viruses / Q000276:immunology / Q000502:physiology; D013045:Species Specificity; D013552:Swine; D018523:Tropism; D014611:Vaccination; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000276:immunology; D014759:Viral Envelope Proteins / Q000235:genetics
D000914:Antibodies, Viral; D014614:Vaccines, Synthetic; D014759:Viral Envelope Proteins; C087086:glycoprotein E2, classical swine fever virus