How mosquito spit may help create the ‘Holy Grail’ of vaccines

Reuters June 11 | Updated on June 12, 2020 Published on June 12, 2020

The Lancet trial on humans showed that an Anopheles mosquito-based vaccine triggered antibody and cellular responses

Five years ago, in an office complex with a giant sculpture of a mosquito just north-west of Phnom Penh, Jessica Manning struck on a novel idea. Rather than spend more years in what felt like a futile search for a malaria vaccine, she would take on all mosquito-borne pathogens at once.

Her idea revolved around mosquito spit. Building on the work of colleagues and other scientists, Manning, a clinical researcher for the US National Institute of Allergy and Infectious Diseases, believed she could use pieces of mosquito saliva protein to build a universal vaccine.

The vaccine, if it pans out, would protect against all of the pathogens the insects inject into humans — malaria, dengue, chikungunya, Zika, yellow fever, West Nile, Mayaro viruses and anything else that may emerge.

“We need more innovative tools,” said Manning. A vaccine like this would be “the Holy Grail.” On Thursday, The Lancet published the initial results of this work with her colleagues: the first-ever clinical trial of a mosquito spit vaccine in humans. The trial showed that an Anopheles mosquito-based vaccine was safe and that it triggered antibody and cellular responses.

The global disruption of the Covid-19 pandemic has brought a sharp focus on infectious diseases and vaccine research. One of the key areas of concern are pathogens transmitted by mosquitoes. The novel coronavirus, believed to have originated in bats, has so far infected more than 7.4 million people and killed nearly 420,000 worldwide.

Targeting the carrier

Manning’s research is specific to mosquitoes, but is an example of how scientists are broadening their thinking about how to tackle infectious diseases, and the new types of tools they are developing.

What Manning is looking for is called a vector-based vaccine. A vector is the living organism — like a mosquito — that transmits a pathogen such as malaria between humans, or from animals to humans. All existing vaccines for humans target a pathogen. Manning’s goes after the vector.

The idea is to train the body’s immune system to recognise the saliva proteins and mount a response that would weaken or prevent an infection.

Published on June 12, 2020
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