Mycoviruses affect the virulence of Aspergillus flavus to immunosuppressed mouse model

Abstract:

[Objective] To compare the virulence of different Aspergillus flavus strains and the effect of the mycovirus AfPV1 on A.flavus virulence to the established immunosuppressed mouse model. [Methods]Institute of Cancer Research (ICR) mice were intraperitoneally injected with different concentrations of cyclophosphamide, and the degree of immunosuppression was determined based on the number of white blood corpuscles. Different concentrations of A.flavus spores were inoculated through nasal drip and caudal vein, and the optimal inoculation amount ofA.flavus spores was determined based on the mortality rate of mice within 14 days. Fungal load and pathological changes of lung tissue were employed to determine whether the mice were infected by A.flavus. The effect of AfPV1 on the virulence of A.flavus was finally evaluated with the mouse model.[Results]The cyclophosphamide at a dose of 250 mg/kg caused the immunosuppression of ICR mice. Fungal load and histological changes demonstrated that ICR mice were successfully infected byA.flavus. In the nasal inoculation model, the inoculation with 40 μL (1×10⁶ CFU/mL spores) A.flavus was suitable for the evaluation of A.flavus virulence. In the model of caudal vein inoculation, the suitable inoculation dose ofA.flavus was 50 μL (1×10⁶ CFU/mL spores). AfPV1 weakened the virulence of A.flavus while did not affect the load of A.flavus in mice. [Conclusion] The constructed mouse infection model could evaluate the pathogenicity of A.flavus strains, and the mycovirus AfPV1 infection reduced the pathogenicity ofA.flavus.

Key words:Aspergillus flavus;mycovirus;immunosuppressed mice;infection model;caudal vein inoculation;nasal inoculation