Analysis of cellular immune response in pigs recovered from porcine respiratory and reproductive syndrome infection

The cellular immune response to a European isolate of porcine reproductive and respiratory syndrome (PRRS) virus in animals recovered from the experim ental infection has been studied in vitro. Peripheral blood mononuclear cel ls (PBMC) from these pigs proliferated specifically when they were stimulat ed with PRRS virus. This response was not detectable until 4 weeks after in oculation and remained for more than 3 months. Addition of blocking monoclo nal antibodies to the cultures showed that this proliferation was mainly de pendent on CD4+ cells with the participation of SLA-class II molecules. T-c ell cultures established by stimulating responding cells with PRRS virus an d maintained in culture for lip to 3 weeks showed an increase of CD8+ CD4and CD4- CD8+ subsets within activated cells, gated according to their ligh t scatter parameters, whereas CD4+ CD8- cells declined along the time in cu lture. Within the activated cells, those expressing the TcR gamma delta rec eptor also increased, being most of them also positive for the CD8 marker. By RT-PCR, T-cells responding to the virus showed a Th1 type cytokine produ ction pattern. During the culture period the cytotoxic activity against K-5 62 cells increased from 15 to 35% of specific lysis. This cellular immune r esponse may play a relevant role in the clearance of PRRS virus and the rec overy of the infection. (C) 1999 Elsevier Science B.V. All rights reserved.