Inhibition of ehrlichial infection using effective proteins from tick, Ixodes ovatus

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1.Two SPF beagle dogs were inoculated with HF565, Ehrlichia which was isolated from Japanese tick (Ixodes ovatus). They had no clinical signs and results of PCR using DNA from white blood cells were all negative. These results suggested that dogs are not infected with Ehrlichia HF565.2.Ten rats were inoculated with HF565. They had no clinical signs and survived 4 weeks after inoculation. Histopathological changes such as necrosis of liver cells and infiltration of lymphoid cells were observed in the rats 1 week after inoculation of HF565. Many ehrlichial morulae were also observed mainly in endothelial cells. PCR using DNA from liver, spleen, kidney and lung showed positive results. The lesion of lever turned to be light during experiment. PCR using DNA from peripheral blood were all negative. These results suggest that HF565 could infect to rats but they were eliminated during 3 to 4 weeks after infection.3.Expression of dog cytokine mRNA in Ehrlichia canis-infected dogs were investigated. Interferon-γ (IFN-γ) and tumor necrosis factor-αmRNA were detected in peripheral blood mononuclear cells on 3 to 8 days after infection. The expression continued for more than 2 months after infection. Production of IFN-γ after infection of E.canis to dog peripheral blood mononuclear cells in vitro was confirmed. It was also confirmed that addition of peripheral blood mononuclear cells from E.canis-infected dog inhibited the growth of E.canis in vitro. These results suggested that IFN-γ has a very important role in immunity of ehrlichial infection.