PMID- 9918159
OWN - NLM
STAT- MEDLINE
DCOM- 19990413
LR  - 20061115
IS  - 0002-9645 (Print)
IS  - 0002-9645 (Linking)
VI  - 60
IP  - 1
DP  - 1999 Jan
TI  - Diagnostic implications of concurrent inoculation with attenuated and virulent 
      strains of porcine reproductive and respiratory syndrome virus.
PG  - 119-22
AB  - OBJECTIVE: To determine the predominant strain of progeny virus in samples 
      obtained from cell cultures and pigs exposed simultaneously to attenuated and 
      virulent strains of porcine reproductive and respiratory syndrome virus (PRRSV). 
      SAMPLE POPULATION: Cell cultures and twenty 4-week-old pigs. PROCEDURE: Cell 
      cultures and pigs were simultaneously exposed to various relative concentrations 
      of an attenuated, cell-culture-adapted vaccine strain and a virulent field strain 
      of PRRSV. Progeny virus obtained at selected intervals thereafter was tested to 
      determine strain identity by use of restriction fragment length polymorphism 
      (RFLP) analysis. RESULTS: Progeny virus from infected cell cultures comprised the 
      attenuated strain, alone or in combination with the virulent strain, except when 
      cultures had been exposed to a large excess (> 100,000-fold) of the virulent 
      strain. Progeny virus from infected pigs comprised only the virulent strain 
      regardless of the relative concentrations of the 2 strains to which the pigs had 
      been exposed. CONCLUSIONS: During concurrent replication in cell cultures, the 
      attenuated strain quickly predominated. Conversely, during concurrent replication 
      in pigs, the virulent strain quickly predominated. CLINICAL RELEVANCE: It is 
      unlikely that only an attenuated strain of PRRSV would be identified by RFLP 
      testing of samples obtained from pigs concurrently infected with a virulent 
      strain of PRRSV. Nevertheless, the ability of a cell-culture-adapted attenuated 
      strain of PRRSV to predominate during cell culture passage (the first step in the 
      current RFLP testing procedure) indicated that, if possible, samples should be 
      obtained from pigs that do not have a history of direct or indirect exposure to 
      attenuated-virus vaccine.
FAU - Mengeling, W L
AU  - Mengeling WL
AD  - Virology Swine Research Unit, National Animal Disease Center, USDA, Agricultural 
      Research Unit, Ames, IA 50010, USA.
FAU - Lager, K M
AU  - Lager KM
FAU - Wesley, R D
AU  - Wesley RD
FAU - Clouser, D F
AU  - Clouser DF
FAU - Vorwald, A C
AU  - Vorwald AC
FAU - Roof, M B
AU  - Roof MB
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - Am J Vet Res
JT  - American journal of veterinary research
JID - 0375011
RN  - 0 (Vaccines, Attenuated)
RN  - 0 (Viral Vaccines)
SB  - IM
MH  - Animals
MH  - Cells, Cultured
MH  - Cytopathogenic Effect, Viral/immunology
MH  - Polymorphism, Restriction Fragment Length
MH  - Porcine Reproductive and Respiratory Syndrome/*diagnosis/immunology
MH  - Porcine respiratory and reproductive syndrome 
      virus/genetics/immunology/*pathogenicity
MH  - Reverse Transcriptase Polymerase Chain Reaction/veterinary
MH  - Specific Pathogen-Free Organisms
MH  - *Swine
MH  - Vaccination/veterinary
MH  - Vaccines, Attenuated/*immunology
MH  - Viral Vaccines/*immunology
MH  - Virulence
EDAT- 1999/01/26 00:00
MHDA- 1999/01/26 00:01
CRDT- 1999/01/26 00:00
PHST- 1999/01/26 00:00 [pubmed]
PHST- 1999/01/26 00:01 [medline]
PHST- 1999/01/26 00:00 [entrez]
PST - ppublish
SO  - Am J Vet Res. 1999 Jan;60(1):119-22.