An immune-boosting skin cream can protect mice from infection by several viruses that are transferred through mosquito bites. If approved for human use, this could help prevent the spread of mosquito-borne viruses, such as Zika, dengue and chikungunya, which infect hundreds of millions of people each year.
The cream, which contains the drug imiquimod, is already licensed for the treatment of genital warts and a rare skin condition called actinic keratosis, but has not yet been tested in humans for use on mosquito bites.
It works by rapidly activating local immune responses in the skin, which then prevent the virus from spreading to the rest of the body.
Clive McKimmie at the University of Leeds in the UK, and his team injected mice at mosquito bite sites with Semliki Forest virus, a mosquito-borne virus that has caused outbreaks in Africa.
In a test, seven out of 11 mice whose mosquito bites were treated with the skin cream survived infection. Another 11 mice did not receive the cream, and none of them survived the infection.
The skin cream also limited the spread of chikungunya virus and another mosquito-borne virus called Bunyamwera orthobunyavirus in mice bitten by mosquitoes, suggesting the treatment could work against many mosquito-borne viruses.
“It was a big surprise that simply applying a cream could have such a dramatic effect,” says Clive McKimmie at the University of Leeds in the UK. He and his team found that application of the skin cream up to five hours after a bite still protected the mice from getting sick.
“Those really early hours and days in the skin before the virus spreads to other parts of the body are really crucial and can have a really big impact on the course of disease and on how severe the disease ends up being,” says Kevin Maringer at the University of Surrey in the UK, who was not involved with the work.
The cream also limited the spread of Zika and chikungunya viruses in human skin tissue samples tested in the lab, hinting that this approach might also work in people.
Currently, the best way people can protect themselves against these viruses is by using insect repellent to prevent mosquito bites in the first place, says McKimmie. But this study is a first step towards a medicine that could actually stop the virus from infecting after a mosquito bite, he says.
McKimmie says safety tests on humans will need to be done, but Maringer says that because the drug is already approved for human use, the anti-viral cream could be approved relatively quickly.
Journal reference: Science Translational Medicine, DOI: 10.1126/scitranslmed.aax2421
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