Regulation of maedi-visna virus and cytokine gene expression in macrophages

• Main Author: Zhang, Zhidong
• Published: University of Edinburgh 2000
• Subjects: 636.089
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664231

Macrophages are proposed to play a central role in Maedi-visna virus (MVV) infection as target cells. However, the level of MVV load in alveolar macrophages (AMs) and its correction with pulmonary lesions is unknown. Also it is not yet clear whether cytokine expression is dysregulated in macrophages infected with MVV. In addition, the effects of exogenous cytokines on MVV replication in macrophages have not been documented. The aims of this study were to determine. 1. the level of MVV DNA in AMs compared with blood monocytes in natural infection and assess the correlation of viral burden and replicative status to the lung lesions related to MVV infection; 2. the differential expression of cytokine genes in macrophages infected with MVV <i>in vivo </i>and <i>in vitro; </i>3. the effect of GM-CSF, TGF-b and IFN-g on MVV replication in macrophage <i>in vitro.</i> Quantitative competitive-PCR for MVV <i>pol </i>was developed to quantify accurately the level of MVV DNA load in AMs. This first required constructing a competitive template which bears the same recognition site as target template to be quantified, but truncated by a 25 bp sequence. The quantitative evaluation of the PCR signal clearly shows that the overall levels of MVV DNA load in AMs was significantly higher than that in blood monocytes (P<0.05). Changes of viral load in AMs differed in relation to the histopathological lesions in the lungs. Relatively high viral load was found in AMs from the lung with histopathological lesions. Furthermore, MVV replication did not occur in AMs isolated from sheep without histopathological lesions in lung, but could be stimulated <i>in vitro, </i>suggesting that the levels of MVV DNA load reflects the pathological manifestation in the site of disease. In addition, MVV replication in AMs <i>n vivo </i>may require the availability of certain factors to activate viral replication and these may be important in disease progression. Such factors could be cytokines produced by macrophages present or recruited in the site of disease.