Characterization of novel macrophage cell lines derived from goat and sheep blood and their susceptibility to ruminant virus infections

cultures of macrophages provide a valuable tool for studying the innate immune functions of macrophages and macrophage-pathogen interactions in specific animal species. We previously demonstrated that porcine macrophages were effectively immortalized by transferring the simian virus 40 large T antigen (SV40LT) gene and porcine telomerase reverse transcriptase (pTERT) gene using lentiviral vectors. In the present study, we investigated whether this immortalization protocol may be applied to macrophages from small ruminants. Primary goat and sheep macrophages were successfully isolated from mixed cultures of heparinized whole blood with porcine kidney-derived feeder cells. Goat blood-derived macrophages (GBMs) and ovine blood-derived macrophages (OBMs) were then immortalized by introducing the SV40LT and pTERT genes, and immortalized GBM (iGBM) and OBM (iOBM) cell lines were established. iGBM and iOBM cells exhibited typical Iba1-, CD172a-, and CD204-positive macrophage-like phenotypes and the upregulated phosphorylation of nuclear factor-kB, p38, and p44/42 mitogen-activated protein kinases in response to the bacterial cell wall components, lipopolysaccharides, and muramyl dipeptides. These cells retained typical macrophage functions, such as the production of inflammatory cytokines and phagocytosis. iGBM and iOBM cells were susceptible to infection not only by caprine arthritis encephalitis and bluetongue viruses, which primarily affect goats and sheep, but also by arthropod-borne viruses that cause encephalitis primarily in cattle. Therefore, the iGBM and iOBM cell lines provide unique models for investigating the characteristics and pathogenesis of ruminant viruses.IMPORTANCEInfectious diseases in goats and sheep cause severe economic losses; therefore, the development of infection prevention and control protocols is important. Since these animals share a number of pathogens with other livestock and humans, making them potential sources of zoonotic diseases, basic research is being conducted to further characterize the pathogens and develop more effective vaccines. Against this background, the significance of the present study lies in establishing new sustainable cell lines from goat and sheep macrophages. These cells retained typical macrophage functions, such as the production of inflammatory cytokines and phagocytosis. Interestingly, they were susceptible to infection not only by caprine arthritis encephalitis and bluetongue viruses, which primarily affect goats and sheep, but also by arthropod-borne viruses that cause encephalitis primarily in cattle. Therefore, the goat and sheep macrophage cell lines established in this study provide practical and reliable models for investigating the host-pathogen interactions of ruminant viruses.