Immunohistochemical detection of PRRS virus antigen in inoculated pigs

Abstract

Porcine Reproductive and Respiratory Syndrome (PRRS), is a viral disease of swine that has been known in the United States since the 1980s. The sickness was initially characterized by rapid propagation through pork farms, spreading through almost all the United States and later Canada and European countries. In Chile, PRRS was diagnosed at the end of 1999 and is currently part of an eradication program. 
To contribute to the diagnosis of the disease in our environment and to characterize the distribution of the viral antigen in the tissues of inoculated pigs, using an immunohistochemical (IHC) study was carried out utilizing 12 hybrid pigs originated from a PRSS free genetic pyramid. Nine were inoculated with the national isolate of the PRRS virus and three were used as controls. The inoculated pigs received an intranasal dosage of 7.0 ml of viremic serum from inoculated pigs with a cellular culture dose of 105.4 TCID50 in order to reactivate its pathogenicity; they were also inoculated intramuscularly with 0.7 ml of the same serum. The pigs of the control group were sacrificed at 0 dpi and the inoculated pigs at 7, 14 and 21 dpi, At necropsy time, tonsils, retropharyngeal and mediastinal lymphatic nodes, thymus, spleen, nasal turbinates, lung, heart and liver were dissected, fixed, dehydrated and paraffin embedded. Additionally, lung alveolar macrophages were collected via a bronchoalveolar lavage. All these samples were immunostained using the monoclonal antibody SDOW-17 and the ABC complex method. 
Viral antigen was detected in the macrophages of all the tissues studied from 7 to 21 dpi. The organs that showed greatest intensity of reaction were the lungs and spleen. The consistent finding of greater quantity viral antigen of in these organs, these tissues suggest constitute the best source of samples for diagnosing the disease whether by IHC or other methods that detect the viral antigen or its genome.