Monday, July 4, 2016

Bacterial blockage of Zika virus transmission

According to a recent study published in Scientific Reports, researchers have confirmed that Wolbachia does indeed block transmission of the Zika virus in Aedes aegypti and could present, “a novel biological control mechanism.”

Wolbachia were previously studied by researchers in Brazil who found that mosquitoes infected with the bacteria were unable to transmit the Dengue virus. In an effort to study the effects of the bacteria on Zika transmission, the researchers infected a sample population of Aedes aegypti with the wMel strain of the bacteria. The group found that only 10% of mosquitoes infected with the wMel strain disseminated the Zika virus. At the time, Brazilian study co-author Luciano Andrade Moreira, PhD, told Contagion that “because of the bacteria’s proven role in preventing Dengue transmission, Wolbachia can be used as a relatively inexpensive approach to controlling the spread of Zika as well.”

 In the recent study, researchers from the UW-Madison School of Veterinary Medicine and Universidad de Antioquia in Medellin, Colombia performed “one of the first [studies on] Zika virus transmission using a living host.” First, the researchers infected mice with Zika virus that had been isolated from a human patient. Next, they allowed both wMel-infected and non-infected (wild-type) mosquitoes to feed on the mice, two or three days after the mice were infected. In addition, the researchers allowed infected and non-infected mosquitoes to feed on a membrane “containing sheep’s blood spiked with a high concentration of Zika virus.”

The researchers found that the mosquitoes infected with Wolbachia were less likely to become infected with the Zika virus after feeding, and that those who did become infected were unable to transmit the virus in their saliva. Lead researcher Jorge Osorio stated, "Mosquitoes with Wolbachia were less capable of harboring Zika virus, and though they do get infected with Zika, it is to a lesser extent than wild-type mosquitoes."

Interestingly, the researchers also found that the source of the mosquitoes’ blood meal impacted their infection and ability to transmit the virus. Those mosquitoes that fed on the mice were “infected at higher rates” and had higher levels of the virus than those that fed on the membrane. These findings could impact future studies.

With mosquito-borne viruses such as Zika, Dengue, Chikungunya, and Yellow Fever wreaking havoc on the global population, effective prevention measures are paramount. Research on Wolbachia is proving to be promising and could be used as a multivalent strategy against these viruses in the near future.   
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1 comment:

  1. Aliota MT, Peinado SA, Velez ID, Osorio JE. The wMel strain of Wolbachia Reduces Transmission of Zika virus by Aedes aegypti. Sci Rep. 2016 Jul 1;6:28792. doi: 10.1038/srep28792.

    Zika virus (ZIKV) is causing an explosive outbreak of febrile disease in the Americas. There are no effective antiviral therapies or licensed vaccines for this virus, and mosquito control strategies have not been adequate to contain the virus. A promising candidate for arbovirus control and prevention relies on the introduction of the intracellular bacterium Wolbachia into Aedes aegypti mosquitoes. This primarily has been proposed as a tool to control dengue virus (DENV) transmission; however, evidence suggests Wolbachia infections confer protection for Ae. aegypti against other arboviruses. At present, it is unknown whether or not ZIKV can infect, disseminate, and be transmitted by Wolbachia-infected Ae. aegypti. Using Ae. aegypti infected with the wMel strain of Wolbachia that are being released in Medellin, Colombia, we report that these mosquitoes have reduced vector competence for ZIKV. These results support the use of Wolbachia biocontrol as a multivalent strategy against Ae. aegypti-transmitted viruses.