Phenotype, growth regulation and cytokine transcription in Ovine Herpesvirus-2 (OHV-2)-infected bovine T-cell lines

The causal agent of sheep-associated malignant catarrhal fever (MCF), Ovine Herpesvirus-2 (OHV-2), can be propagated in IL-2-dependent lymphoblastoid cell lines derived from diseased cattle and deer providing a useful model for the investigation of the pathogenesis of MCF. In this study, five interleukin-2 (IL-2)-dependent cell lines were established from affected cattle to examine their growth regulation and cytokine transcription. All cell lines expressed CD2, CD5 and CD25. Three of the cell lines were CD4+ and one CD8+, whereas one cell was of mixed CD4 and CD8 phenotye. The growth of these cell lines was reduced when cultured with antibody against CD25, the IL-2 receptor α subunit. All cell lines showed a lack of response to Con A and their cell growth was inhibited by Cyclosporin A which is known to inhibit cytokine promoters. It was decided therefore, to examine the cell lines for the presence of mRNA of different cytokines. The results showed that the cell lines transcribed message for IFNγ, TNFα, IL-4 and IL-10 whereas no mRNA for IL-2 or IL-1β was detected. In conclusion, the OHV-2-immortalised cell lines resemble anergic T-cells which may be activated giving rise to the characteristic lesions of MCF.