Study using mosquitoes to deliver vaccines has Chinese researchers buzzing

Researchers harness mosquitoes to deliver re-engineered vaccines for animals
Study may pave the way to reduce viral infections like Zika and could help save endangered wildlife

Science

Zhang Tongin Beijing

Published: 8:00pm, 4 Jan, 2023

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A team of Chinese scientists has provided new evidence that one of humankind’s most annoying, or even deadly, pests could be a key ally in the fight against viral diseases.

In an article published in the peer-reviewed journal Nature Communications on December 16, researchers said they had developed new technology that can turn a mosquito into a flying vaccine carrier to immunise animals in the wild.

“Our study provides a future avenue for developing a mosquito-delivered vaccine to eliminate zoonotic viruses,” said Professor Zheng Aihau, with the Institute of Zoology’s State Key Laboratory of Integrated Management of Pest Insects and Rodents at the Chinese Academy of Sciences, who led the research.

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The finding could not only lead to a reduced spread of viruses within populations of hard-to-access wildlife hosts, but also protect endangered species from viral diseases, the researchers said in the paper.

The researchers found that bites in wildlife from genetically modified mosquitoes triggered a strong, long-lasting immune response. Once immunised, the animals resisted infections, thus helping to prevent the early spread of many viruses, including the once widespread Zika virus (ZIKV).

Zika belongs to the flavivirus genus and is transmitted primarily by Aedes mosquitoes. People infected by the virus can have symptoms ranging from rashes and fever to muscle and joint pain.

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But Zika virus infections during pregnancy can cause infants to be born with microcephaly (an abnormally small head or cranial capacity) and other congenital malformations. The infection can also lead to premature birth or miscarriage.

At its peak in 2015, Brazil reported around 1.3 million Zika cases. Although infection rates declined globally after 2017, Zika persists in many tropical African and Asian countries. Experts have said the best way to curb the virus is to stop its circulation among its animal reservoirs.

Zheng and his team were inspired by a previous study of another virus in the flavivirus genus – the Chaoyang virus (CYV) – which was first discovered in 2009 in Chaoyang City, in China’s Liaoning province. That study found the virus could replicate in mosquitoes, but not in vertebrates.

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In their study, the researchers used CYV as a vaccine vector to construct a chimeric vaccine, which contains proteins from a different virus. They took several proteins from CYV and inserted them into ZIKV cells to create the CYV-ZIKV virus, which was not infectious. CYV-ZIKV could replicate efficiently in mosquitoes and be secreted in saliva, they said.

By feeding mosquitoes blood that contained the CYV-ZIKV virus, the insects were transformed into a vaccine carrier. Zheng’s team then tested the effectiveness of their new vaccine on mice.

Using Aedes mosquitoes infected with the new CYV-ZIKV virus, each mouse was bitten up to three times by 30 different mosquitoes, to simulate natural conditions.

The researchers found that the mice developed a protective immune response after being bitten by the mosquitoes carrying CYV-ZIKV, with resulting antibodies that lasted more than five months. After being injected with ordinarily lethal doses of Zika virus, the newly “immunised” mice all survived.

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Additionally, the researchers found that immunisation in the mice also prevented Zika transmission from the mice to mosquitoes, thus blocking its cycle in nature.

To rule out the chance that the lab-made CYV-ZIKV virus could spread to wild mosquito populations, all mosquitoes used in the experiment were X-ray irradiated, rendering them infertile.

“Targeted immunisation of wild animal reservoirs is a promising approach, not only for control of zoonotic diseases infecting domestic animals and humans, but also for protection of endangered wildlife, such as ruffed grouse decreased by West Nile virus,” Zheng wrote in the article.

“Our study provides a future avenue for developing a mosquito-delivered vaccine for wildlife immunisation.”