Abstract
Influenza virus causes high morbidity among the infected population annually and occasionally the spread of pandemics. Melaleuca alternifolia Concentrate (MAC) is an essential oil derived from a native Australian tea tree. Our aim was to investigate whether MAC has any in vitro inhibitory effect on influenza virus infection and what mechanism does the MAC use to fight the virus infection. In this study, the antiviral activity of MAC was examined by its inhibition of cytopathic effects. In silico prediction was performed to evaluate the interaction between MAC and the viral haemagglutinin. We found that when the influenza virus was incubated with 0.010% MAC for one hour, no cytopathic effect on MDCK cells was found after the virus infection and no immunofluorescence signal was detected in the host cells. Electron microscopy showed that the virus treated with MAC retained its structural integrity. By computational simulations, we found that terpinen-4-ol, which is the major bioactive component of MAC, could combine with the membrane fusion site of haemagglutinin. Thus, we proved that MAC could prevent influenza virus from entering the host cells by disturbing the normal viral membrane fusion procedure.
Highlights
Influenza is an infectious disease caused by the influenza virus which is a RNA virus of the familyOrthomyxoviridae
Madin-Darby Canine Kidney (MDCK) cells were co-cultured with Melaleuca alternifolia Concentrate (MAC) at various concentrations for about 72 h
MAC at concentration higher than 0.050% could induce significant cellular death, it did not have any cytotoxic effect on MDCK cells when the concentration was lower than 0.025%
Summary
The haemagglutinin (HA) on the surface of influenza virus particles is a major viral membrane glycoprotein molecule, which is synthesized in the infected cell as a single polypeptide chain precursor (HA0) with a length of approximately 560 amino acid residues and subsequently cleaved by an endoprotease into two subunits called HA1 and HA2 and be covalently attached by the disulfide bond [15,16]. A pore is opened up by this structural change of more than one haemagglutinin molecule and the contents of the virion are released into the cytoplasm of the cell This completes the uncoating process [25]. Because of the conformational change of viral HA protein is indispensable for the membrane fusion process between influenza virus and the endosome of the host cell, this makes it a new target for anti-influenza virus drug development. Terpinen-4-ol was the main component of MAC, so here we assessed the feasibility and sensitivity of interaction of terpinen-4-ol with the viral haemagglutinin protein through in silico prediction to confirm the drug target and the characterization of the protein changes after treatment with MAC
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