06-21-07

ISU entomologist on international team that identified mosquito's immune system genes

AMES, Iowa -- Understanding how the immune system evolved in insects can help scientists gain new insight into human response to infection, says an Iowa State University entomologist.

Lyric Bartholomay.

Lyric Bartholomay is part of the international team that identified 350 genes in the immune system of a tropical disease-transmitting mosquito and looked at their evolution as compared to two other species. Their paper was published in the June 21 edition of the journal Science.

Bartholomay was invited to the team of 35 scientists because of her expertise in a component of the immune response in certain disease-transmitting mosquitoes. For several years, she has researched antimicrobial peptides, small proteins that are activated when an adult mosquito is infected with bacteria and other pathogens.

"Understanding how the mosquito responds when it is infected with a particular pathogen will help us understand how a human responds to infection," Bartholomay said. "And it can potentially help us come up with some new ways to control infection and the transmission of disease agents from the perspective of the mosquito."

The scientists looked at three organisms-Drosophila melanogaster, the much-studied fruit fly; Anopheles gambiae, the African malaria mosquito; and the newly genome-sequenced Aedes aegypti, the mosquito that transmits Dengue virus to more than 50 million people worldwide each year.

The fruit fly doesn't transmit any pathogens,Anopheles gambiae transmits malaria parasites, but rarely any viruses, and Aedes aegypti transmits some very important viruses that have a tremendous impact on public health.

"Each organism responds to infection differently. By comparing the genomes of the three, we can see where one fly has evolved to have more or slightly different genes involved in immunity," she said.

"This is a starting point for figuring out not just control strategies, but also very fundamentally how the immune system evolved in different species separated by millions of years in their evolution," Bartholomay said. "There's a tremendous amount that can be learned by doing this comparative analysis."

For example, scientists found that some of the same genes that flies turn on in response to fungi and bacteria are also turned on in people when they're infected.

"We're developing some fantastic scientific resources to study innate immune responses," she said.

Bartholomay will continue studying the mosquito's immune system using functional genomics analyses.

"That's asking the genome sequence, when do you actually turn these genes on?" she said. "What triggers the mosquito to make a protein that's involved in immunity and when does it happen? Is it in the larvae stage or the adult stage? In response to a viral infection or a bacterial infection? That's the kind of research I do."

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