Virology. 2011 Jan 19. [Epub ahead of print]

Chimeric porcine reproductive and respiratory syndrome viruses reveal full function of genotype 1 envelope proteins in the backbone of genotype 2.

Tian D, Zheng H, Zhang R, Zhuang J, Yuan S.

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) is classified into two genotypes, type 1 and type 2, which share only about 60% genetic identity. Here, we report viable chimeric viruses in which the envelope protein genes from ORF2a to ORF5 of vSHE (type 1) were swapped into the genetic backbone of vAPRRS (type 2). We found that the envelope proteins of genotype 1 were fully functional in genotype 2 PRRSV, and the rescued chimeric progeny viruses showed robust genetic stability and similar replication properties to the parental strains in vitro. To our knowledge, this is the first study to report the substitution of complete ORFs between different genotypes of porcine arterivirus. These findings pave the way to further elucidate the structure-function relationship of PRRSV envelope proteins, and may enable the development of novel marker vaccines that can be used to differentiate vaccinated from infected animals.

Although not a "field" paper, I posted this study because it documents an important step in PRRSv vaccine development knowledge.

Tian D, Zheng H, Zhang R, Zhuang J, Yuan S. 2011. Chimeric porcine reproductive and respiratory syndrome viruses reveal full function of genotype 1 envelope proteins in the backbone of genotype 2. Virology [0042-6822] Tian yr:2011 (electronically available, ahead of print).

Further assessment of air filtration for preventing PRRSV infection in large breeding pig herds

Dee S, Spronk G, Reicks D, Ruen P, Deen J. 2010. Further assessment of air filtration for preventing PRRSV infection in large breeding pig herds. Veterinary record 167(25):976-977.

Short communication that documents the possibility of drastically reducing the likelihood of a breeding herd to become PRRSv infected over a two years period (p=0.0001) by applying negative pressure ventilation system + air filtration + high biosecurity standard procedure.

Terminology for classifying swine herds by porcine reproductive and respiratory syndrome virus status

Holtkamp DJ, Polson DD, Torremorell M, et al. Terminology for classifying swine herds by porcine reproductive and respiratory syndrome virus status. J Swine Health Prod. 2011;19(1):44–56.

Abstract. Standardized terminology for the porcine reproductive and respiratory syndrome virus (PRRSV) status of swine herds is necessary to facilitate communication between veterinarians, swine producers, genetic companies, and other industry participants. It is also required for implementation of regional and national efforts towards PRRSV control and elimination. The purpose of this paper is to provide a herd classification system for describing the PRRSV status of herds, based upon a set of definitions reflecting the biology and ecology of PRRSV. The herd classification system was developed by a definitions committee formed jointly by the American Association of Swine Veterinarians (AASV) and the United States Department of Agriculture PRRS-Coordinated Agricultural Project, and was approved by the AASV Board of Directors on March 9, 2010. The committee included veterinarians from private practice and industry, researchers, and representatives from AASV and the National Pork Board.

Breeding herds, with or without growing pigs on the same premises, are categorized as Positive Unstable (Category I), Positive Stable (Category II), Provisional Negative (Category III), or Negative (Category IV) on the basis of herd shedding and exposure status. Growing-pig herds are categorized as Positive or Negative. Recommended testing procedures and decision rules for herd classification are detailed.