Functional impairment of PRRSV-specific peripheral CD3+CD8 cellsSarah Costers1, David J. Lefebvre1, Bruno Goddeeris2, Peter L. Delputte1 and Hans J. Nauwynck1
1 Laboratory of Virology, Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
2 Department of Biosystems, Division of Gene Technology, Faculty of Bioscience Engineering, Catholic University Leuven, Kasteelpark Arenberg 30, 3001 Leuven, Belgium
Received 15 October 2008; accepted 14 May 2009; published online 16 May 2009
Abstract - The replication of porcine reproductive and respiratory syndrome virus (PRRSV) in lungs and lymphoid tissues of PRRSV-infected pigs is already strongly reduced before the appearance of neutralizing antibodies, indicating that other immune mechanisms are involved in eliminating PRRSVat those sites. This study aimed to determine whether PRRSV Lelystad virus (LV)-specific cytotoxic T-lymphocytes (CTL) can efficiently eliminate PRRSV-infected alveolar macrophages. Therefore, CTL assays were performed with PRRSV-infected alveolar macrophages as target cells and autologous peripheral blood mononuclear cells (PBMC) from PRRSV-infected pigs as a source of PRRSV-specific CTL. PBMC of 3 PRRSV-infected pigs were used either directly in CTL assays, or following restimulation in vitro. CTL assays with pseudorabies virus (PRV) Begonia-infected alveolar macrophages and autologous PBMC, from 2 PRV Begoniainoculated pigs, were performed for validation of the assays. In freshly isolated PBMC, derived from PRRSV-infected pigs, CTL activity towards PRRSV-infected macrophages was not detected until the end of the experiment (56 days post infection – dpi). Restimulating the PBMC with PRRSV in vitro resulted in proliferation of CD3+CD8 cells starting from 14 dpi. Although CD+CD8 cells are generally considered to be CTL, CTL activity was not detected in PRRSV-restimulated PBMC of the 3 pigs until 49 dpi. Aweak PRRSV-specific CTL activity was observed only at 56 dpi in PRRSV-restimulated PBMC of one pig. In contrast, a clear CTL activity was observed in PRV Begonia-restimulated PBMC, derived from PRV Begonia-infected pigs, starting from 21 dpi. This study indicates that PBMC of PRRSV-infected pigs contain proliferating CD3+CD8 cells upon restimulation in vitro, but thesePBMCfail to exert CTL activity towards PRRSV-infected alveolar macrophages.
Key words: PRRSV / cell-mediated immune response / cytotoxic T-lymphocyte / alveolar macrophage
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© INRA, EDP Sciences 2009