Abstract
BackgroundEdible Bird’s Nest (EBN) as a popular traditional Chinese medicine is believed to have health enhancing and antiviral activities against influenza A virus (IAV); however, the molecular mechanism behind therapeutic effects of EBN is not well characterized.MethodsIn this study, EBNs that underwent different enzymatic preparation were tested against IAV infected cells. 50% cytotoxic concentration (CC50) and 50% inhibitory concentration (IC50) of the EBNs against IAV strain A/Puerto Rico/8/1934(H1N1) were determined by HA and MTT assays. Subsequently, the sialic acid content of the used EBNs were analyzed by fluorometric HPLC. Western Blotting and immunofluorescent staining were used to investigate the effects of EBNs on early endosomal trafficking and autophagy process of influenza virus.ResultsThis study showed that post inoculations of EBNs after enzymatic preparations have the highest efficacy to inhibit IAV. While CC50 of the tested EBNs ranged from 27.5–32 mg/ml, the IC50 of these compounds ranged between 2.5–4.9 mg/ml. EBNs could inhibit IAV as efficient as commercial antiviral agents, such as amantadine and oseltamivir with different mechanisms of action against IAV. The antiviral activity of these EBNs correlated with the content of N-acetyl neuraminic acid. EBNs could affect early endosomal trafficking of the virus by reducing Rab5 and RhoA GTPase proteins and also reoriented actin cytoskeleton of IAV infected cells. In addition, for the first time this study showed that EBNs can inhibit intracellular autophagy process of IAV life cycle as evidenced by reduction of LC3-II and increasing of lysosomal degradation.ConclusionsThe results procured in this study support the potential of EBNs as supplementary medication or alternative to antiviral agents to inhibit influenza infections. Evidently, EBNs can be a promising antiviral agent; however, these natural compounds should be screened for their metabolites prior to usage as therapeutic approach.
Highlights
Edible Bird’s Nest (EBN) as a popular traditional Chinese medicine is believed to have health enhancing and antiviral activities against influenza A virus (IAV); the molecular mechanism behind therapeutic effects of EBN is not well characterized
A: Absorbance of the samples B: Absorbance of the virus-infected control C: Absorbance of negative control of both virus and compound Since the results showed that post-treatment of IAV with EBNs had the highest protection, this treatment approach is further analyzed by incubating the infected cells with EBNs for 1, 8 & 24 h
The results revealed that post-inoculation of EBN from Gua Madai with no enzymatic treatment (EBN3) could protect more than 60% of the infected cells compared to other EBNs (42 to 53% of protection), amantadine (39% of protection) and oseltamivir (40% of protection) (Table 2)
Summary
Edible Bird’s Nest (EBN) as a popular traditional Chinese medicine is believed to have health enhancing and antiviral activities against influenza A virus (IAV); the molecular mechanism behind therapeutic effects of EBN is not well characterized. After entry and during the replication, influenza virus would start to exploit the host autophagy pathway by controlling of the fusion of lysosomes to the autophagosomes, which would accelerate the virus replication, reduce antigenicity of the infected cells to evade the host immune system and manipulate apoptosis process of the host cells depend on the state of the infection [6, 7]. All of these molecular pathways can be possible targets for inhibiting IAV replication and controlling of the disease
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