Tert-butyl hydroquinone (TBHQ) – a common food additive – may protect people from the avian influenza A strain H7N9, according to a new study published in the journal PLoS ONE.

This image shows H7N9 virions. Image credit: Cynthia S. Goldsmith / Thomas Rowe.

“The recent H7N9 outbreak in China this past March had a mortality rate of more than 20 percent. That strain, which is new, is already showing resistance to the majority of existing drugs used to treat it. The need to develop new antiviral therapeutics now is crucial,” said senior author Dr Michael Caffrey from the University of Illinois.

Flu viruses enter host cells using a special protein called hemagglutinin, which acts as a key that opens receptors on the cell surface. If hemagglutinin is disabled, the virus is locked out and can’t infect cells.

Dr Caffrey’s team found that the FDA-approved TBHQ sticks to a specific region on the hemagglutinin molecule.

TBHQ is an effective antioxidant. It is used as a preservative for vegetable oils and edible animal fats. its E number is E319.

“The additive attaches to the Achilles’ heel of the virus – a loop-shaped portion of hemagglutinin necessary for binding to cells, making cell infection impossible. The loop on the hemagglutinin molecule represents a new therapeutic target, since existing drugs don’t go after it.”

“Any drugs that focus on the hemagglutinin loop would be totally novel to flu viruses, and so resistance, if developed, would still be a long way off.”

The team was looking at a different class of viruses when the first outbreak of the H7N9 virus was reported in China last spring.

“TBHQ was known to have virus-blocking effects for H3 viruses. So when the H7N9 outbreak occurred, we thought we’d see if it had any effect on H7 viruses,” Dr Caffrey said.

The team fused the hemagglutinin of the H7N9 virus to a less dangerous virus in order to study it safely. They found that TBHQ was able to prevent the virus from infecting human lung cells in the lab.

The researchers are now looking for ways to enhance TBHQ’s ability to prevent infection.

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Source: Antanasijevic A et al. 2013. Inhibition of Influenza H7 Hemagglutinin-Mediated Entry. PLoS ONE 8 (10): e76363; doi: 10.1371/journal.pone.0076363