J Vet Sci.  2002 Jun;3(2):75-85.

Assessment of Porcine Reproductive and Respiratory Syndrome Virus RNA Load in Sera and Tissues during Acute Infection

• Shin JH
• Molitor TW

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) RNA load in sera and tissues during acute phase of infection was evaluated using a PCR- based quantitative assay. More than 80% of infected pigs (21/25) showed the peak level of viral RNA concentrations in serum (up to 8.6 x 108 copies/ml) at day 5 postinfection (PI), and started to clear the virus from the systemic circulation thereafter. Regression analysis using the viral RNA concentrations in sera obtained from days 5 to 14 PI showed that the viral RNA was cleared at the rate of 0.37 log reduction in the number of PRRSV RNA copies per day. It was estimated to be day 27 PI when the viral RNA in the serum of infected pigs becomes undetectable. When correlation analysis was performed between the systemic clearance rate and viral RNA concentrations in tissues of 9 infected pigs obtained at day 14 PI, moderately strong negative correlation was observed in the thymus (r = - 0.62) and brain stem (r = - 0.48), suggesting the capability of host animal to clear PRRSV from the systemic circulation appears to be related to the viral activity in the thymus and brain stem.

Keyword

PRRSV; Quantitation; Serum; Tissue; Viral load

MeSH Terms

Animals
Brain Stem/virology
Eye/virology
Female
Logistic Models
Lymphoid Tissue/virology
Male
Porcine Reproductive and Respiratory Syndrome/blood/*virology
Porcine respiratory and reproductive syndrome virus/*genetics/*isolation & purification
RNA, Viral/*analysis
Reference Standards
Reverse Transcriptase Polymerase Chain Reaction
Swine/*virology
Time Factors
*Viral Load
Viremia/veterinary/virology