Expression of Interferon-gamma and Tumour Necrosis Factor-alpha in Pigs Experimentally Infected with Porcine Reproductive and Respiratory Syndrome Virus (PRRSV)

Abstract

The expression of mRNA encoding interferon-γ (IFN-γ) and tumour necrosis factor-α (TNF-α) was studied, by reverse transcription–polymerase chain reaction and by in-situ hybridization with a non-radioactive digoxigenin-labelled probe, in formalin-fixed, paraffin wax-embedded lung tissue from pigs experimentally infected with a Korean isolate (North American genotype) of PRRSV. Both IFN-γ and TNF-α mRNA were detected in the lung as early as 1 day post-inoculation (dpi) and up to 10 dpi. Hybridization signals for IFN-γ and TNF-α were usually associated with inflammation, in particular with macrophages within alveolar septa. Expression of these cytokines was minimal in non-lesional lung of PRRSV-infected pigs and in normal lung from control pigs. The results suggest that IFN-γ and TNF-α play a role in pulmonary defence against PRRSV.