Evidence that persistent porcine reproductive and respiratory syndrome virus infection in pigs does not require significant genetic change in open reading frame 5
Chih-Cheng Chang, DVM, PhD; Kyoung-Jin Yoon, DVM, PhD; Jeffrey J. Zimmerman, DVM, PhD
PDF version is available online.
Objective: To assess genetic and antigenic changes in porcine reproductive and respiratory syndrome virus (PRRSV) over the course of infection in individual, persistently infected pigs.
Materials and methods: Three individually housed “principal pigs” were inoculated (Day 0) with a plaque-cloned virus (CC-01) derived from the North American PRRSV isolate, VR-2332. Homogenates of tissues collected on Day 120 were inoculated into individually housed PRRSV-naive bioassay pigs. Genetic changes in open reading frames (ORFs) 1b, 5, and 7 in plaque-cloned viruses isolated from the original inoculum and serum of principal and bioassay pigs collected 7 days post inoculation were assessed by sequencing. Antigenic changes (in GP 5 and N proteins) were assessed by monoclonal antibody analysis.
Results: One bioassay pig became infected with PRRSV. A total of 71 PRRSV plaque-cloned isolates were recovered from the virus inoculum, serum from the persistently infected principal pig, and serum from its corresponding bioassay pig. ORF 1b and ORF 7 amino-acid sequences from 30 plaque-cloned viruses isolated from the bioassay pig were identical with the virus inoculum (CC-01). Analysis revealed three ORF 5 amino-acid variants in the bioassay pig, with the dominant variant identical to one isolated from serum collected from the principal pig on Day 7. Monoclonal antibody analysis found no changes in the phenotypic epitopic profiles of the plaque-cloned isolates.
Implications: Persistent PRRSV infection does not depend on mutations in ORFs 1b, 5, or 7. These results have implications for PRRSV immunology and for efforts to control or eliminate the virus.
Keywords: porcine reproductive and respiratory syndrome virus, PRRSV, persistence, evolution
Cite as: Chang CC, Yoon KJ, Zimmerman JJ. Evidence that persistent porcine reproductive and respiratory syndrome virus infection in pigs does not require significant genetic change in open reading frame 5. J Swine Health Prod 2009;17(6):318-324.
Search the AASV web site for pages with similar keywords.