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Genetic modification alters mating preference of malaria mosquitoes
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A genetic modification that helps Anopheles mosquitoes combat malaria also alters their mating preferences in a way that helps them spread the genetic modification to future generations, researchers reported.
The modification involves boosting the mosquitoes’ resistance to Plasmodium falciparum, the parasite that causes malaria. According to researchers, the process also alters the microbiota of the genetically modified (GM) mosquitoes, leading to changes in mating preferences so that GM males prefer unmodified wild-type females, and WT males prefer GM females, driving up the population of modified parasite-resistant mosquitoes.
"We believe that by changing the microbiota, we're changing the scent of modified mosquitoes —which, in turn, alters mating preference," George Dimopoulos, PhD, professor in the department of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health, said in a news release. "It's the perfect change in mating preference in this case, because it maximizes the chances of producing genetically modified offspring when mosquitoes compete for mates."
Malaria is usually spread to humans through the bite of infected female Anopheles mosquitoes. Dimopoulos and colleagues altered the gene activity of several strains of Anopheles stephensi mosquitoes to make them more resistant to P. falciparum and less likely to transmit the parasite to humans. They mixed equal numbers of GM and WT mosquitoes in a caged colony in Dimopoulos’ lab and measured GM frequency over 10 generations.
The prevalence of GM mosquitoes rose to around 90% in the first generation and remained at that level for all 10 generations. Dimopoulos and colleagues said the efficiency with which GM mosquitoes spread their modifications to ensuing generations was unexpected.
They discovered that boosting the mosquitoes’ immunity to P. falciparum also increased their resistance to bacteria, reducing their normal load of bacteria and altering the normal mix of bacterial species in their intestines and reproductive organs. Moreover, the mosquitoes have maintained their high level of resistance for over 7 years in Dimopoulos’ lab without any adverse effects.
"These mosquitoes haven't changed in terms of feeding behavior or any other things that could be of concern," Dimopoulos said.
Researchers in a second study conducted at the Johns Hopkins Malaria Research Institute said they discovered a strain of malaria-killing Serratia bacteria that spreads efficiently, passing easily from males to females during mating and then from females to their offspring, allowing it to spread rapidly through mosquito populations. Other mosquito-infecting bacteria are not spread as easily, according to the news release.
“The huge burden of malaria in developing countries urgently demands the development of novel approaches to fight this deadly disease,” Marcelo Jacobs-Lorena, PhD, professor of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health, and colleagues wrote in the report.
Jacobs said discovery of the Serratia strain — which they dubbed “AS1” — happened by chance.
"We were working with a different bacterium when a researcher on the project happened to find evidence of a bacterial colony in our mosquitoes' ovaries," he said in the release. "That was unusual — normally we find bacteria only in the mosquito gut." – by Gerard Gallagher
Disclosures: The authors report no relevant financial disclosures.
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