Sustaining Interferon Induction by a High-Passage Atypical Porcine Reproductive and Respiratory Syndrome Virus Strain.
Porcine reproductive and respiratory syndrome virus (PRRSV) strain A2MC2 induces type I interferons in cultured cells. The objective of this study was to attenuate this strain by serial passaging in MARC-145 cells and assess its virulence and immunogenicity in pigs. The A2MC2 serially passaged 90 times (A2MC2-P90) retains the feature of interferon induction. The A2MC2-P90 replicates faster with a higher virus yield than wild type A2MC2 virus. Infection of primary pulmonary alveolar macrophages (PAMs) also induces interferons. Sequence analysis showed that the A2MC2-P90 has genomic nucleic acid identity of 99.8% to the wild type but has a deletion of 543 nucleotides in nsp2. The deletion occurred in passage 60. The A2MC2-P90 genome has a total of 35 nucleotide variations from the wild type, leading to 26 amino acid differences. Inoculation of three-week-old piglets showed that A2MC2-P90 is avirulent and elicits immune response. Compared with Ingelvac PRRS®MLV strain, A2MC2-P90 elicits higher virus neutralizing antibodies. The attenuated IFN-inducing A2MC2-P90 should be useful for development of an improved PRRSV vaccine.
Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA.
Zexu
Z
Ma
Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA.
Ying
Y
Yu
Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA.
Yueqiang
Y
Xiao
The Roslin Institute and The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Roslin, Midlothian, UK.|Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA.
Tanja
T
Opriessnig
Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA.
Rong
R
Wang
Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA.
Liping
L
Yang
Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA.
Yuchen
Y
Nan
Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA.
Siba K
SK
Samal
Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA.
Patrick G
PG
Halbur
Molecular Virology Laboratory, VA-MD College of Veterinary Medicine, University of Maryland, College Park, MD, USA.
Yan-Jin
YJ
Zhang
D000818:Animals; D057134:Antibodies, Neutralizing / Q000378:metabolism; D000914:Antibodies, Viral / Q000378:metabolism; D002460:Cell Line; D002522:Chlorocebus aethiops; D014644:Genetic Variation; D005838:Genotype; D007370:Interferon Type I / Q000378:metabolism*; D016676:Macrophages, Alveolar / Q000166:cytology / Q000821:virology; D019316:Porcine respiratory and reproductive syndrome virus / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity*; D017384:Sequence Deletion; D013552:Swine; D014709:Vero Cells; D014764:Viral Proteins / Q000235:genetics*; D014774:Virulence; D014776:Virus Cultivation / Q000379:methods*; D014779:Virus Replication
D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D007370:Interferon Type I; D014764:Viral Proteins