In vitro anti-influenza activity of a protein-enriched fraction from larvae of the housefly (Musca domestica)

Context: Insects are a large, unexplored and unexploited source of potentially useful compounds for modern medicine. The larvae of the housefly (Musca domestica) have been used to study immune-induced molecules because they can survive in pathogenic environments. Objective: The antiviral activity of a protein-enriched fraction (PEF) from the larvae of the housefly was evaluated in vitro and the possible antiviral mechanism was studied. Materials and methods: PEF was isolated from the larvae of the housefly. The cytotoxicity of PEF was detected by the MTT assay. The in vitro antiviral activity of PEF against influenza virus was investigated. PEF was incubated with the virus and its target cells under various conditions, and its antiviral effects were examined by reduction in virus yield in cell cultures. Experiments with ribavirin were performed in parallel under the same conditions. Results: The results indicated that PEF had minimal cytotoxicity against MDCK cells and the CC50 value was calculated to be 284.45 mu g/ml. The antiviral results showed the loss of infectious capacity was more than two log (2) units in cell cultures compared with virus control. The effect of PEF was direct virucidal activity and the interference on the adsorption of cell and virus. The antiviral mechanism of PEF is different from ribavirin. Conclusion: The results indicate that PEF showed strong antiviral activity against influenza virus at a very early stage of the interaction with virus particles or their entry into the cells. PEF has a great potential as a resource of healthy products.