Differences in Cytokine mRNA Profiles between Naïve and in Vivo‐Primed Ovine PBMC after Exposure to Heat‐Inactivated Coxiella burnetii

Abstract: During human Coxiella burnetii (C. burnetii) infections, high IL‐10 levels favor replication of C. burnetii in monocytes and development of chronic Q fever, whereas IFN‐γ promotes intracellular killing. Sheep are a common source for human C. burnetii infections, but in contrast to man become transiently infected only. In a first approach to unravel the role of cytokines during ovine C. burnetii infections, we investigated by semiquantitative RT‐PCR whether heat‐inactivated C. burnetii affects the transcription of genes coding for IL‐2, IL‐4, IL‐10, and INF‐γin vitro in PBMC from sheep seropositive or seronegative for C. burnetii. By computer‐assisted evaluation of band intensities the transcription rate of the cytokine genes was quantified in relation to transcription in Concanavalin A‐stimulated and nonstimulated controls. Transcription rates in PBMC from seropositive animals after incubation with C. burnetii for 4 hours strongly resembled those found in PBMC from seronegative sheep. However, upon prolonged incubation (24 h) C. burnetii induced an increased IL‐10 transcription in PBMC from 2 of 5 seronegative, but in PBMC from 5 of 5 seropositive animals. The data suggest that natural C. burnetii infections prime the ovine immune system towards a TH2‐like pattern and this action thereby represents the first clue for the involvement of ovine immune cells in the response to C. burnetii infections.