Genetic and experimental comparison of porcine circovirus type 2 (PCV2) isolates from cases with and without PCV2-associated lesions provides evidence for differences in virulence.
There are marked differences in the clinical expression of diseases associated with porcine circovirus type 2 (PCV2) in the field. The objective of this study was to compare the sequences and pathogenicity of PCV2 isolates from field cases with and without PCV2-associated lesions. Forty-two specific-pathogen-free (SPF) pigs were assigned randomly to three groups of 14 pigs each. At 7 weeks of age, group 1 pigs were mock-inoculated with saline, group 2 pigs were inoculated with PCV2-4838 (isolated from a pig with no evidence of PCV2-associated lymphoid lesions) and group 3 pigs were inoculated with PCV2-40895 (isolated from a pig with PCV2-associated lymphoid lesions and disease). The PCV2-4838 and PCV2-40895 isolates shared approximately 98.9 % nucleotide sequence identity across the entire genome. A total of nine amino acid changes in ORF2 and two amino acid changes in ORF1 were identified between the two isolates. PCV2-4838-inoculated pigs had significantly more genomic copy numbers of PCV2 in their sera at 7 days post-inoculation (p.i.) (P<0.0001) and significantly fewer genomic copy numbers at 14, 21 and 28 days p.i. (P<0.05) compared with pigs inoculated with the PCV2-40895 isolate. Microscopic lesions in lymphoid tissues were significantly less severe (P<0.05) and the amount of PCV2 antigen associated with these lesions was significantly lower (P<0.05) in pigs inoculated with PCV2-4838. The results of this study suggest that PCV2 isolates from the USA differ in virulence in an SPF pig model.
Opriessnig
T
T
Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011-1250, USA.
McKeown
N E
NE
Department of Biomedical Sciences and Pathobiology, Center for Molecular Medicine and Infectious Diseases, College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0342, USA.
Zhou
E-M
EM
Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011-1250, USA.
Meng
X-J
XJ
Department of Biomedical Sciences and Pathobiology, Center for Molecular Medicine and Infectious Diseases, College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0342, USA.
Halbur
P G
PG
Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011-1250, USA.
D000595:Amino Acid Sequence; D000818:Animals; D000914:Antibodies, Viral; D018173:Circoviridae Infections / Q000473:pathology / Q000662:veterinary* / Q000821:virology; D017925:Circovirus / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity*; D008168:Lung / Q000473:pathology / Q000821:virology; D008198:Lymph Nodes / Q000473:pathology / Q000821:virology; D008969:Molecular Sequence Data; D014066:Palatine Tonsil / Q000473:pathology / Q000821:virology; D013047:Specific Pathogen-Free Organisms; D013154:Spleen / Q000473:pathology / Q000821:virology; D013552:Swine / Q000821:virology; D013553:Swine Diseases / Q000473:pathology* / Q000821:virology*; D014764:Viral Proteins / Q000737:chemistry; D014766:Viremia; D014774:Virulence
D000914:Antibodies, Viral; D014764:Viral Proteins