The Asian Tiger mosquito (Aedes albopictus), originated in tropical and sub-tropical regions of Asia, but can now be found across the globe. Photo: CDC/James Gathawy.
As mosquito-borne viral
diseases like West Nile fever, dengue fever,
and chikungunya fever spread rapidly around the globe, scientists at Virginia
Tech are working to understand the mosquito’s immune system and how the viral
pathogens that cause these diseases are able to overcome it to be transmitted
to human and animal hosts.
In nearly every part of
the world, humans and animals experience high levels of morbidity and mortality
after being bitten by mosquitoes infected with viruses. More than 100 different
viruses transmitted by blood feeding arthropods like mosquitoes have been
associated with human or animal disease.
Two especially prolific
vectors are the yellow fever mosquito (Aedes aegypti) and Asian tiger
mosquito (Aedes albopictus), which is easy to spot because of its
striped patterning. Although native to Africa and Asia,
these insects can spread through the western world by hitching rides in used
tires, which trap water to create a perfect breeding site.
Virginia Tech researchers
recently identified a novel anti-viral pathway in the immune system of culicine
mosquitoes, the insect family to which both vectors belong. Kevin Myles and
Zach Adelman, both associate professors of entomology in the College of Agriculture
and Life Sciences, publish their findings in PLoS Pathogens.
“We have previously
shown that an anti-viral response directed by small interfering RNAs (siRNAs)
is present in culicine mosquito vectors. However, we show here that another
class of virus-derived small RNAS, exhibiting many similarities with
ping-pong-dependent piwi-interacting RNAs (piRNAs) is also produced in the soma
of culicine mosquitoes,” they explain. Myles, Adelman, and coworkers made
use of a technique called next-generation sequencing to aid in their discovery.
The newly discovered anti-viral
pathway appears to act redundantly to the previously described siRNA pathway,
indicating a robust immune system, said Myles. Thus, understanding how viruses
get around the mosquito’s dual antiviral responses poses an increasingly
interesting challenge to scientists.
“In the case of
mosquito-borne pathogens, our health depends as much on the mosquito’s immune
response as it does on our own immune response, yet surprisingly little is
known about the immune system of the mosquito,” Myles said.