It turns out that dengue causing mosquitoes are quite health conscious themselves. After they suck blood, the mosquitoes make sure ramp up production of immune system proteins that help fight off the parasites that blood might contain.
Michael Povelones at the University of Pennsylvania, who co-authored and collaborated on new the study with Imperial College London researchers, said that the new mechanism seemed to be the one by which the mosquito anticipated a parasite infection.
He said that mosquitoes do a great job of controlling infection in their own bodies, and if they could use that information to their advantage, it might be able possible to find new avenues of preventing mosquitoes from transmitting disease.
In the current study, the researchers wanted to gain a deeper understanding of what the other identified LRIM proteins-there are at least two dozen-did for mosquito immunity.
From their tests, one protein, LRIM9, stood out. When it was blocked, parasite levels in the mosquitoes increased three-fold. And they found that adult females had the highest expression levels of LRIM9, with more than 20 times the amount of LRIM9 as adult males. LRIM9 RNA expression was also low in earlier life stages, such as in eggs and pupae.
The team fed mosquitoes blood from mice that were either infected with P. berghei or were uninfected. No matter whether the insects drank the infected or uninfected blood, LRIM9 levels surged 48 hours after their meal.
That finding still left open the possibility that there were pathogens besides P. berghei in the blood to which LRIM9 was responding.
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Since it appeared that the parasites and bacteria weren't responsible for activating LRIM9, the researchers considered whether hormones might be playing a role. They zeroed in on ecdysone, a steroid hormone secreted by the ovaries after blood feeding that regulates genes important to reproduction.
After injecting mosquitoes with 20E, the biologically active form of ecdysone, the team observed an increase in production of the LRIM9 protein, and found that LRIM9 too did not impact reproductive success.
In a final query, the researchers checked to see whether LRIM9 acted in the same pathway as LRIM1 and APL1C, but found no evidence to support its involvement.
Povelones and colleagues believe that LRIM9 may help the mosquito immune system recognize pathogens and may also recruit or interact with other immune system components. Thus beefing up its levels could quicken an immune response, before a parasite is even detected.
The study is published in the Journal of Innate Immunity.