CDC / Dr. Paul howell
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British researchers have discovered a new mechanism for protecting malaria mosquitoes from insecticides. This is a protein from the senses, which begins to be actively produced in the legs and antennae under the action of the poison and binds its molecule, rendering it harmless. Blocking this protein is enough for the insecticide to regain its strength, they write scientists in the journal Nature.
For many years of struggle with plasmodium falciparum, the most effective weapon was not even against the parasite itself, but against its carrier – the malaria mosquito Anopheles gambiae. Insecticide-soaked nets reduce the number of infected insects, as they reduce the risk that a mosquito will survive to see plasmodium.
However, in recent years there has been no noticeable progress in the battle against malaria: in 2017 alone, 219 million infections were recorded among the African population. Apparently, mosquitoes gradually become insecticide resistant, which reduces the effectiveness of the nets. Therefore, in different regions of Africa, ordinary nets are gradually being replaced with nets with a double insecticide: standard pyrethroid and a substance that blocks the main mechanism of resistance to it.
However, not all mosquito populations succumb to even a double insecticide, which led scientists to think that other mechanisms of resistance are possible. A team led by Hillary Ranson of the Liverpool School of Tropical Medicine has checked which genes are expressed in malaria mosquito cells from Burkina Faso and Ivory Coast – areas with particular insecticide resistance.
Scientists drew attention to the fact that in these insects, in comparison with insecticide-resistant relatives, the expression of the CSP protein group is increased. These are small proteins that are found only in arthropods and serve to transport hydrophobic substances within the senses. Researchers measured the expression of these proteins in different parts of the mosquito’s body and found that there are especially many of them in the areas in which animals come in contact with the network — in the legs, head, and antennas (antennae) —up to 10 times more than in other parts of the body.
Then the researchers acted on a mosquito with a common insecticide and noticed that after that the expression of two proteins – CSP6 and SAP2 – increased 10-15 times. Moreover, the SAP2 protein began to form strongly in the legs and antennas – places of direct contact with the insecticide.
To verify that it is the SAP2 protein that confers resistance to mosquitoes, scientists blocked its work in insect cells using RNA interference. As a result, mosquitoes remained viable and prolific – but only until they met an insecticide. The blockade of SAP2 immediately turned insects, which were initially insensitive to poison, into sensitive ones, increasing their mortality in the presence of an insecticide by 6-7 times.
Researchers have introduced the gene SAP2 into the cells of E. coli in order to produce it quite a lot, and then checked with which substances it interacts. It turned out that if the bacteria were treated with an insecticide, then SAP2 reliably connects it. Apparently, the same mechanism prevents the poison from acting on mosquitoes.
The authors of the work suggested improving insecticidal nets: depending on which population is widespread in a particular region, nets can be impregnated not only with different poison, but also with various additives that block the resistance of insects to these poisons.
We already wrote that scientists are trying to defeat malaria in a variety of ways, including using botox, transgenic mushrooms and even homemade broths. We also talked about how researchers are trying to improve insecticidal nets, becoming point of view tse-tse fly.
Polina Loseva
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