Distribution of a Korean strain of porcine reproductive and respiratory syndrome virus in experimentally infected pigs, as demonstrated immunohistochemically and by in-situ hybridization

In an experiment with 40 specific pathogen-free pigs aged 3 days, the distr ibution of a Korean isolate of porcine reproductive and respiratory syndrom e virus (PRRSV) was assessed immunohistochemically and by in-situ hybridiza tion for a period of 28 days after intranasal inoculation. The most consist ent and intense labelling for PRRSV was in the lung, the virus persisting i n pulmonary macrophages for at least 28 days. The middle lobe of the lung w as the optimum site for the detection of PRRSV antigens and nucleic acids, and the interstitial macrophage was the main cell type in which PRRSV was i dentified. Other tissues and cells in which the virus was detected included macrophages and dendritic cells in the tonsil, lymph nodes, spleen and Pey er's patches, and macrophages in the hepatic sinusoids and adrenal gland. T he experiment suggested that the pathogenesis of PRRSV infection may be sum marized thus: initial entry of virus through tonsillar and pulmonary macrop hages, followed within 3 days by viraemia and subsequent interstitial pneum onia. (C) 1999 W.B. Saunders Company Limited.