Abstract: Objective To study the expression and the role of interferon-gamma (IFN-γ)in murine systemic infection of Scedosporum apiospermum. Methods The murine models of systemic Scedosporum apiospermum infection was established by inoculation of the pathogenic fungi. ELISA and RT-PCR were applied to detect the expression level of IFN-γ protein and mRNA in spleens, respectively. Colony formingunit (cfu) of infected kidneys was determined with the plating dilution method. The mean survival time (MST) of the mice was also recorded. Results IFN-γ levels in lethal infection group were lower than those of the normal controls (P<0.05 on day 3 and P > 0.05 on day 7). IFN-γ levels of sublethal infection group were higher than those of normal controls (P<0.05 on day 3 and P<0.01 on day 7). IFN-γ levels of dexa-methasone-immunosuppressed group were lower than those of the normal group (P<0.05 on day 3 and P>0.05 on day 7). But the IFN-γ levels were significantly lower in the immunosuppressed group than those in the sublethal infection group (P<0.01 on day 3 and day 7). Fungal loads in the kidneys showed that there were a large amount of fungi in kidneys in both the lethal infection group and the immunosuppressed group, while only a few fungi in the sublethal infection group. The MST was 13.6 days and 14.2 days in the lethal infection group and the immunosuppressed group respectively, while it was more than 45 days in both the normal controls and the sublethal infection group. Conclusions The large dosage inoculation of Scedosporum apiospermum in normal mice and small amount of the fungi inoculation in the dexamethasone-immunosuppressed mice lead to the lethal infection. It suggests that IFN-γ might play a protective role in the murine systemic infection of Scedosporum apiospermum.

Key words: Scedosporium, Mycoses, Interferon type Ⅱ, Animal testing alternatives