Influenza A viruses and Honeysuckle

Influenza A viruses have the annoying habit of frequently mutating and thus succesfully evading vaccination. These virusses are constantly changing via antigenic drift, antigenic shift or even reassortment. That's the reason why we need to vaccinate ourselves every year to be protected during the winter season.

Honeysuckle-based teas have long been utilized in Chinese culture to combat cold and Influenza-like symptoms. The plant (not the actress Honeysuckle Weeks) is known for its heady, intoxicating scent. Several reports have indicated that a decoction of honeysuckle (Lonicera japonica) can suppress the replication of Influenza A viruses in the human body. However, the active compound or compounds in this decoction and the mechanism by which they block viral replication have long remained unclear.

If we accept the idea that the honeysuckle has some antiviral properties, it must be possible to identify the exact compound.

Scientists have tried to do just that. They identified a plant microRNA called miR2911[1]. MicroRNAs are small molecules found in plants and animals that play an important role in influencing the pathways responsible for many diseases. These miRNAs resemble the small interfering RNAs (siRNAs) of the RNA interference (RNAi) pathway.

In clinical trials, this molecule was able to suppress Influenza A(H1N1) Virus, Influenza A(H7N9) and Influenza A(H5N1) Virus. This suggests that it has a broad-spectrum antiviral activity.

The scientists delivered boiled honeysuckle to the plasma and lung tissue of mice infected with an Influenza A(H1N1) virus. Results showed that miR2911 quickly bound itself to the messenger RNA - the molecule containing the genetic information - of the two genes responsible for viral replication. This binding mechanism blocked the replication process, and eventually the virus was destroyed. Other plants, such as chamomille, were found to also contain high levels of miR2911[2].

It was previously thought that boiling honeysuckle would destroy the beneficial molecules, but miR2911 proved resilient and to retain its properties even after boiling. This suggests that honeysuckle tea might be an effective way to prevent or  treat an Influenza infection.

[1] Zhen et al: Honeysuckle-encoded atypical microRNA2911 directly targets influenza A viruses in Cell Research - 2015. See here.
[2] Yang et al: Detection of an Abundant Plant-Based Small RNA in Healthy Consumers in PLoS One - 2015