As per the study researchers predicting that the stability of mosquito borne disease prevention; to reduce transmission of dengue to humans, scientists have introduced Wolbachia bacteria to A. aegypti mosquitoes. By finding ability to block virus transmission may be maintaining by natural selection; alleviating concern that this benefit could diminish over time.
The results of our study have significant implications for the continued use of Wolbachia as a biocontrol agent for this disease. The team also discovered a gene within A. aegypti that is likely involved in Wolbachia’s ability to interfere with viral replication, shedding light on a possible mechanism for the blocking trait.
Mosquito borne disease
According to McGraw, Wolbachia bacteria occur in many insects, including some mosquitoes, but they do not naturally occur in A. aegypti, the mosquito species that transmits dengue virus. The bacteria were introduced to A. aegypti in 2011 and since have been released in trials in several countries, including Australia, Brazil, Colombia, Vietnam and Indonesia, to assess the ability of the bacterium to control the spread of disease.
As a virus blocker within A. aegypti, McGraw and her colleagues using artificial selection in the laboratory to select for high; and low dengue blocking abilities in A. aegypti. Next, they sequenced the genomes of these two groups; identified areas that differed and measured the insects fitness or ability to survive and reproduce. There has been concern that dengue virus could evolve an ability to sneak past Wolbachia or that the insects themselves could evolve resistance to Wolbachia.
Exhibiting better blocking
But finding that the mosquitoes exhibiting better blocking had increased fitness; at least under idealized conditions in the laboratory; suggesting the potential for natural selection to maintain blocking. But by comparing the genomes of high and low dengue blockers; the team identified a specific gene; a cadherin protein that likely is involving in virus blocking. Study finding that much of the genetic variation determining Wolbachia’s anti-viral effect was within a mosquito gene controlling cell-to-cell adhesion.
However, according to a previous theory suggested that Wolbachia; as a foreign substance within mosquitoes, could be triggering the insects immune systems; which in turn, could suppress virus activity. Another theory suggested that Wolbachia could be competing with viruses for nutrients or physical space within mosquitoes. By this results suggesting that the cadherin gene may affect cell-to-cell signaling or movement of viruses within cells; altering the virus’s ability to enter cells, replicate within them and then exit.