Itching, swelling, many people’s summer memories, mosquitoes are a nasty existence. In addition, mosquitoes bring people a variety of terrible mosquito-borne diseases. In 2018, Zika fever and Rift Valley fever, two severe mosquito-borne viral infectious diseases, were included among the eight infectious diseases of urgent concern announced by the World Health Organization.

In the vast crowd, what kind of person attracts mosquitoes the most?

The reporter learned from Tsinghua University that in a study just published in “Cell”, the team of Professor Cheng Gong of the School of Medicine of the school revealed the cunning of mosquito-borne viruses: mosquitoes do not randomly bite their hosts, and human odor is the regulation of mosquito behavior. key factor.

“The olfactory nervous system of mosquitoes senses a characteristic odor molecule derived from an infected person, locates the infected person with high efficiency, and then bites and eats the blood with the virus, resulting in the efficient transmission of the virus between ‘host-mosquito’. Cheng Gong said that the main source of human body odor is skin microorganisms. By regulating skin microorganisms and remodeling the smell of infected people, it can affect the olfactory perception of mosquitoes. Relevant evaluations believe that this discovery provides a new strategy for blocking the rapid spread of mosquito-borne viruses in nature.

Why are these people more favored by mosquitoes?

Relevant data show that there are hundreds of mosquito-borne viruses in nature, which can be carried by mosquitoes and transmitted to human and animal hosts, causing serious diseases such as viral encephalitis, meningitis and hemorrhagic fever. In the past 20 years, emerging and re-emerging mosquito-borne viruses, represented by dengue virus, Zika virus, chikungunya virus, and West Nile virus, have been circulating around the world, infecting billions of people and causing dozens of infections every year. Thousands died.

But unfortunately, so far, there are no effective vaccines and targeted therapeutic drugs for most of the virulent mosquito-borne viruses. The scientific community urgently needs to deeply study the basic principles of the prevalence and transmission of mosquito-borne viruses in nature, and develop new prevention and control strategies to block them. The massive spread of the virus around the world.

“Mosquito-borne viruses circulate in a cycle between host and mosquito. In the virus transmission cycle, mosquitoes need to find, locate and bite an infected person or animal, and eat the blood with the virus. Then, the mosquito can carry and quickly spread the virus. If the mosquito bites a non-infected person, it will not effectively acquire the virus infection, and the transmission cycle of the virus will be interrupted.” Cheng Gong said.

How do mosquitoes target virus-infected people? Why are these people more “tasty” in the eyes of mosquitoes? For a long time, scientists have been working to unravel this mystery and find simple and effective ways to curb the rapid spread of the virus.

In this study by Cheng Gong’s team, the researchers established two sets of classical behavioral devices (three-cage olfactometry device, two-arm olfactometry device), and found that dengue virus and Zika virus-infected mice were significantly more attractive Aedes aegypti and Aedes albopictus. Subsequently, the researchers analyzed the body temperature, carbon dioxide release and volatile odor of the virus-infected mice, and found that changes in the host’s odor are the decisive factors that cause the infected host to attract mosquitoes. Further research results show that mice can release a large amount of a volatile small molecule-acetophenone after mosquito-borne virus infection. Acetophenone can effectively activate the olfactory nervous system of mosquitoes and enhance the behavioral tendency of mosquitoes to infected mice. .

The researchers further collected the odor of dengue patients and healthy volunteers and found that the odor of dengue patients showed a stronger attraction to Aedes aegypti. In addition, the odor of patients with dengue fever also contained significantly higher levels of acetophenone than healthy volunteers. The researchers applied different concentrations of acetophenone to human arms for mosquito behavioral verification, and found that increasing the content of acetophenone in human odor can significantly attract mosquitoes.

The above test shows that dengue patients release a large amount of acetophenone to change their own odor, which greatly improves the attraction to mosquitoes, attracts mosquitoes to bite, and accelerates the spread of the virus.

How is the “scent” that attracts mosquitoes produced?

Since acetophenone is the “culprit” that attracts mosquito bites, how does this “scent” that attracts mosquitoes come about?

The researchers found that acetophenone released by humans or animals mainly comes from skin symbiotic microorganisms on the body surface, which is a typical bacterial metabolite. After the skin commensal microbes were removed, the infected mice lost their stronger attraction to mosquitoes.

Further studies have shown that dengue virus and Zika virus infection can lead to a significant increase in the abundance of Bacillus bacteria on the host skin surface, and Bacillus dermatophytes has the ability to metabolize and produce a large amount of acetophenone.

So far, the researchers have revealed the reason why mosquito-borne virus infected people attract mosquito bites: virus infection increases the proportion of specific bacteria in human skin, significantly increases the ability of infected people to release acetophenone, and thus significantly improves the mosquito’s ability to infect the host. behavioral trends.

The researchers then performed transcriptome sequencing analysis of skin tissue from virus-infected and non-infected mice. The results show that dengue virus and Zika virus infection can inhibit the expression of resistin-like molecules or resistin and other specific immune molecules in the host skin, so that the originally inhibited Bacillus dermatitis excessively proliferate, resulting in the release of acetophenone in the infected host. volume increased.

Subsequently, the researchers fed a vitamin A derivative, isotretinoin, a widely used clinical drug for skin diseases, into mice infected with dengue virus and Zika virus. The results show that the above operations can effectively restore the expression of specific immune molecules in the skin of infected mice, and inhibit the release of acetophenone by the infected host by inhibiting the proliferation of Bacillus in the skin of the infected host. Therefore, after infecting the host with oral isotretinoin, mosquitoes cannot locate and find the infected host through the host’s acetophenone, thereby blocking the transmission cycle of the virus.

How to stop the rapid spread of mosquito-borne viruses?

Based on the above findings, the researchers proposed a new idea for the prevention and control of mosquito-borne viruses: the rapid spread of mosquito-borne viruses can be blocked by regulating human odor.

Since in the early stage of the epidemic of mosquito-borne virus infectious diseases, the proportion of infected people in the population was only one thousandth or even lower, so the research team speculated that after the infected people took vitamin A drugs, mosquitoes could not pass the smell of acetophenone. To distinguish infected and non-infected, this can greatly reduce the probability of mosquitoes feeding on the blood of infected people and infecting them, so that mosquito-borne viruses cannot efficiently establish a “host-mosquito” transmission cycle in nature.

Based on this, the research team proposed a new strategy to prevent and control mosquito-borne virus infectious diseases: in epidemic areas where mosquito-borne virus infectious diseases such as dengue fever and Zika fever are prevalent, vitamin A or related drugs can be widely supplemented to infected people to reshape the infection. It can greatly reduce the circulation efficiency of mosquito-borne virus transmission and effectively prevent mosquitoes from carrying and spreading the virus. Based on the above findings, vitamin A or related drugs can be supplemented to specific infected groups to avoid the large-scale spread of mosquito-borne virus infections.

It is reported that at present, Cheng Gong’s team has completed the research on the skin microbial changes of infected and non-infected patients in Malaysia, and the clinical trial of isotretinoin will be carried out soon. It is expected that the research results will be popularized and applied in the future.

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