itching and swelling. In many people’s memories of summer, mosquitoes are a nasty presence. In addition, mosquitoes also bring a variety of terrible mosquito-borne infectious diseases to people. In 2018, the World Health Organization announced eight infectious diseases that urgently require attention, including Zika fever and Rift Valley fever and Rift Valley fever are two severe mosquito-borne viral diseases.
In the vast sea of people, what kind of people are most attracted to mosquitoes?
The reporter learned from Tsinghua University that in a study just published in "Cell", the team of Professor Cheng Gong from the School of Medicine of the school revealed the cunningness of mosquito-borne viruses: mosquitoes do not bite their hosts randomly, and human body odor is regulated by mosquitoes. key factors in behavior.
"The olfactory nervous system of mosquitoes can sense a characteristic odor molecule originating from an infected person, locate the infected person with high efficiency, and then bite and feed on the blood containing the virus, causing the virus to be efficiently transmitted between the 'host and the mosquito' "Cheng Gong said that the main source of human body odor is skin microorganisms. By regulating skin microorganisms and reshaping the odor 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, new and re-emerging mosquito-borne viruses, represented by dengue virus , Zika virus , chikungunya virus, and West Nile virus, have become prevalent around the world, killing billions of people every year. Infections and hundreds of thousands of deaths.
Unfortunately, so far, there are no effective vaccines and targeted treatments for most potent mosquito-borne viruses. The scientific community urgently needs to conduct in-depth research on the basic principles of the spread of mosquito-borne viruses in nature and develop new prevention and control strategies to prevent them. prevent the spread of the virus around the world.
"Mosquito-borne viruses are transmitted in cycles between hosts and mosquitoes. In the virus transmission cycle, mosquitoes need to find, locate and bite infected people or animals and feed on the virus-laden blood. Mosquitoes then have the ability to carry and spread quickly The ability of the virus. If an mosquito bites a non-infected person with , the virus infection will not be effectively acquired, and the virus transmission cycle will be interrupted," Cheng Gong said.
How do mosquitoes target virus-infected people? Why are these people more "delicious" to mosquitoes? For a long time, scientists have been working to uncover 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 classic behavioral devices (three-cage olfactometry device, two-arm olfactometry device) and found that mice infected with dengue virus and Zika virus Significantly more attractive to Aedes aegypti and Aedes albopictus . Subsequently, the researchers analyzed the body temperature, carbon dioxide and release and volatile odor of virus-infected mice, and found that the change in host odor is the decisive factor that causes the infected host to attract mosquitoes. Further research results show that after mice are infected with mosquito-borne viruses, they can release a large amount of volatile small molecules - acetophenone . Acetophenone can effectively activate the olfactory nervous system of mosquitoes and enhance the behavior of mosquitoes towards infected mice. tend.
Three-cage olfactory measurement device (provided by the research team)
The researchers further collected the odors of dengue fever patients and healthy volunteers, and found that the odor of dengue fever patients showed stronger attraction to Aedes aegypti mosquitoes. Moreover, the acetophenone content in the odor of dengue patients was significantly higher than that of healthy volunteers. Researchers applied different concentrations of acetophenone to human arms to conduct mosquito behavioral verification and found that increasing the acetophenone content in human odor can significantly attract mosquitoes.
The above experiments show that dengue fever patients release a large amount of acetophenone to change their own smell, which greatly increases their attraction to mosquitoes, attracts mosquito bites, and accelerates the spread of the virus.
The research team is assessing mosquito behavior using an olfactometry device. From left to right are Dr. Zhang Hong, the co-first author of the paper, Assistant Researcher Zhu Yibin, and Professor Cheng Gong of , the corresponding author of . (Photo courtesy of the research team)
How is the "fragrance" that attracts mosquitoes produced?
Since acetophenone is the "culprit" that attracts mosquito bites, how is this "fragrance" that attracts mosquitoes produced?
Researchers found that acetophenone released by humans or animals mainly comes from skin commensal microorganisms on the body surface, and it is a typical bacterial metabolite. After removing commensal microorganisms from their skin, infected mice lost their greater 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 skin Bacillus has the ability to metabolize and produce large amounts of acetophenone.
So far, researchers have revealed the reason why people infected with mosquito-borne viruses attract mosquito bites: viral infection increases the proportion of specific bacteria in human skin and significantly increases the infected person's ability to release acetophenone, thereby significantly increasing the mosquito's ability to infect the infected host. behavioral trends.
Subsequently, the researchers conducted transcriptome sequencing analysis on the skin tissues of virus-infected mice and non-infected mice. The results show that dengue virus and Zika virus infection can inhibit the expression of resistin-like molecules or specific immune molecules such as resistin in the host skin, causing the originally suppressed skin Bacillus to overproliferate, resulting in the release of acetophenone in the infected host. The amount increases.
The researchers then fed a vitamin A derivative, isotretinoin, which is a widely used clinical drug for treating skin diseases, into mice infected with dengue virus and Zika virus. The results show that the above operation can effectively restore the expression of specific immune molecules in the skin of infected mice, inhibit the proliferation of Bacillus and in the skin of the infected host, and inhibit the release of acetophenone by the infected host. Therefore, after the infected host takes isotretinoin orally, the mosquito cannot locate and detect the infected host through the host's acetophenone, thereby blocking the virus transmission cycle.
By supplementing vitamin A drugs, it can reshape the release of acetophenone by infected individual skin microorganisms and reduce the cycle efficiency of mosquito-borne virus transmission (photo courtesy of the research team)
How to block the rapid spread of mosquito-borne viruses
Based on the above findings, researchers A new idea for the prevention and control of mosquito-borne viruses is proposed: the rapid spread of mosquito-borne viruses can be blocked by regulating human body odor.
Since in the early stages 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 orally, the mosquitoes could not pass the acetophenone. Using odor to distinguish infected people from non-infected people can greatly reduce the chance of mosquitoes feeding on the blood of infected people and becoming infected, making it impossible for mosquito-borne viruses to efficiently establish a "host-mosquito" transmission cycle in nature.
Based on this, the research team proposed a new strategy to prevent and treat mosquito-borne viral infectious diseases: in epidemic areas where mosquito-borne viral infectious diseases such as dengue fever and Zika fever are prevalent, infected people can be extensively supplemented with vitamin A or related drugs to reshape The volatile odor of microorganisms on the infected person's skin greatly reduces the efficiency of the mosquito-borne virus transmission cycle and effectively prevents mosquitoes from carrying and spreading the virus. Based on the above findings, vitamin A or related drugs can be supplemented for specific infected groups to avoid the large-scale spread of mosquito-borne viral infectious diseases.
It is reported that Cheng Gong’s team has completed research on changes in skin microorganisms of infected and non-infected persons in Malaysia and is about to conduct clinical trials of isotretinoin. It is expected that its research results will be promoted and applied in the future.
(Guangming Daily all-media reporter Deng Hui and correspondent Zhang Hong)
Source: Guangming Daily all-media reporter Deng Hui and correspondent Zhang Hong
