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In this study, we used reverse transcription-quantitative competitive pol
ymerase chain reaction（RT-qcPCR）to assay porcine cytokines and porcine repro
ductive and respiratory syndrome virus（PRRSV）mRNA expression, and investigat
ed the effect of PRRSV infection on cytokine gene expression in the lung tissu
e of nursing pigs. We modified a previously described RT-qcPCR method to const
ruct a DNA fragment to measure interleukin-1beta（IL-1beta）, IL-2, IL-4, IL-8
, interferon-gamma（IFN-gamma）,tumor necrosis factor-alpha, beta-actin, and P
RRSV mRNA expression in pig. This constructed DNA fragment had identical prime
r sequences to target cDNA except differences in the size of products. After c
o-amplifying of RNA-derived cDNA with serial dilution of the DNA fragment and
calculating the ratios between them, a precise quantification data of sample w
as obtained.By using this DNA fragment, it was possible to analyze IL-1beta, I
FN-gamma and PRRSV mRNA expression in the lung between PRRSV-infected（n=4）an
d sham-inoculated（n=4）piglets. The results revealed that piglets infected by
PRRSV had a higher level of IFN-gamma mRNA expression in their lung than thos
e of sham-inoculation（P＜0.05）at 7, 14, and 21 days post-inoculation（PI）.
PRRSV-infected piglets also showed higher IL-1beta mRNA expression than sham-i
noculated ones at 21 days PI（P＜0.05）although there were no differences betw
een the groups of 7 and 21days PI. Besides, as virus load increased IFN-gamma
and IL-1beta mRNA expression would also elevated. From these results, it is co
ncluded that PRRSV infection would alter IFN-gamma and IL-1beta mRNA levels in
the lung tissue of infected piglets; however thedisturbance of immune system
in piglet by PRRSV infection required further study.
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