| Influenza A viruses are negative strand RNA viruses with eight RNA segmented genomes that belong to the family of orthomyxoviridae. While the natural reservoir of these viruses is within wild living water fowl, influenza A viruses also infect humans and several animal species. In fact, influenza A viruses still pose a major burden to human health and cannot be eradicated due to their large natural reservoir. Although vaccination is the best option to protect from influenza virus infections, this approach is difficult with regard to pathogenic avian strains or human reassortants with avian glycoprotein genes. To date only two classes of anti-influenza drugs have been approved: inhibitors of the M2 ion channel or neuraminidase inhibitors. Use of the drugs rapidly results in the emergence of resistant variants and is not recommended for a general and uncontrolled use. It is never stopped to search for a broad spectrum antivirus drug against its rapid variation.Arbidol hydrochloride, ethyl-6-bromo-4-[(dimethylamino)-meth -yl]-5-hydroxy-1-met-hyl-2-[(phenylthio)methyl]-indole-3-carboxylate hydrochloride monohydrate, was exploited by Chemistry Research Center of Soviet Russia for virus inhibition. It was on sale in Russia in 1993 as an antivirus drug and immuno-stimulation reagent against flu and acute infection by other respiratory tract virus. Significantly, the activity of FLU A and B was inhibited, especially in the early stage of virus infection. Simultaneously, it stimulated the expression of IFN, and activated the ability of macrophages.To study the inhibition of influenza A virus by arbidol, models infected by H1N1 subtype virus in vivo and in vitro were performed. Intracellularly, methods of cytopathic effect (CPE) and MTT were used to test TD0 and TD50 of three kinds of drugs, arbidol hydrochloride, guanidine HCl and ribavirin. TD0 of arbidol hydrochloride was 1500mg/L, and the high, mid and low dosages were respectively set at 1000, 500, 250 mg/L. TD0 and TD50 of ribavirin were respectively 800, 1500 mg/L, and the dose of 800mg/L was used in experiments. TD0 of guanidine HCl was 250mg/L. Virus titration was performed by the limit dilution method. The virus titer was estimated from cytopathogenicity of cells induced by viral infection and expressed as 50% tissue culture infectious dose at 0.1mL of 10-2.41 dilution. Accordingly, guanidine HCl and ribavirin are used as drug controls to test the antivirus activity of arbidol hydrochloride, when it was added to MDCK cells before, during and after viral infection. Results showed that groups of three doses abolished the activity of FLU A virus. And they were of great difference respectively and significantly vs VK group (p<0.05). Finally, the results of inhibition on viral multiplication indicated that differences between drug groups and control were bigger than 1 vs VK group (p<0.05).In vivo, LD50 of FLU virus was tested by using Reed-Muench method, with the death rate of infecious BALB/C mice with dilutions ranged from 10-1 to 10-5 recorded. By observation, most mice were down with weight decreased, especially in high dose group. Results suggested that its LD50 was at dilution of 10-2.5. The infectious models were constructed accordingly, and drugs were given (ig) 3 days before infection with high, mid and low three doses 0.1ml/d for 3 days. The protection was estimated by the reduction of the rate of mortality and prolongation of mean day to death. In the lung virus yield study, the mice were sacrificed by cervical dislocation on the 7thday after viral exposure. The body weights of the mice were recorded daily until the animals were killed. The lungs were harvested, weighed, and subsequently homogenized to test the inhibition on which was similar in vitro. It was indicated by results that the drug significantly abolished the activity of FLU-A virus, and viral multiplication in lungs was reduced, for differences between drug groups and control were bigger than 1 vs VK group (p<0.05).Conclusion: In view of the in vitro and in vivo data, we conclude that arbidol hydrochloride has the ability to inhibit the activity of FLU A H1N1 subtype virus as an antivirus drug.
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