CHANGES IN SWINE MACROPHAGE PHENOTYPE AFTER INFECTION WITH AFRICAN SWINE FEVER VIRUS - CYTOKINE PRODUCTION AND RESPONSIVENESS TO INTERFERON-GAMMA AND LIPOPOLYSACCHARIDE

Cytokines produced by cells of the immune system, including macrophage s, can influence inflammatory responses to viral infection. This has b een exploited by viruses, which have developed strategies to direct th e immune response towards ineffective responses. African swine fever v irus (ASFV) is a double-stranded DNA virus that infects macrophages of domestic swine. In this study, primary cells of monocyte-macrophage l ineage were obtained from the lungs, peritoneum or blood of domestic s wine and, after infection with ASFV, supernatants were tested for cyto kines using biological assays. The cytokine transforming growth factor -beta (TGF-beta) was detected after infection of macrophage preparatio ns, but tumour necrosis factor (TNF) and interleukin-1 (IL-1) were not detected. ASFV-infected and uninfected macrophage populations were al so tested to assess their ability to respond to cytokines by enhancing production of superoxide in the respiratory burst mechanism. Response s to interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS) were su ppressed in macrophage populations infected with virus, even at low mu ltiplicities of infection. Addition of TGF-beta to uninfected macropha ges resulted in a similar suppression of response, but antibody to TGF -beta did not prevent suppression induced by virus. These results are discussed in relation to the pathology of African swine fever.