Wolbachia Can Block Zika Virus Transmission

During a session on new approaches to control mosquito populations at the First International Conference on Zika Virus, Matthew Aliota, PhD, research scientist at the University of Wisconsin discussed how the Eliminate Dengue Program uses Wolbachia to impede viral transmission.

During his presentation, Dr. Aliota explained that Wolbachia are “ubiquitous intracellular bacteria,” that are naturally found in 40-60% of insect species worldwide, including many mosquito species, but not Aedes aegypti. Wolbachia can be used as a “biological control agent” to block the transmission of not just arboviruses, but all mosquito-borne pathogens. There are several Wolbachia strains, and the one currently being used by the Program, the wMel strain, has a “pathogen-blocking phenotype.” Nevertheless, Wolbachia-infected mosquitoes are “completely safe,” since Wolbachia cannot be “transmitted from mosquitoes to vertebrate hosts.”

According to Dr. Aliota, Scott O’Neill, PhD, FAA, FAAAS, the Lead of the Eliminate Dengue Program, first considered controlling Dengue vectors using Wolbachia bacteria, which are able to block the transmission of all four Dengue serotypes, in 1993. The exact mechanism by which Wolbachia block viruses is still unknown to this day; however, Dr. Aliota speculates that it may be due to a “competition for resources.” For example, in an exclusive interview with Contagion®, he stated, “Wolbachia [are] really good at sucking up all of the cholesterol in a cell, and Chikungunya virus requires lots of cholesterol to package its viral particle.”

In his interview with Contagion^®, Dr. Aliota explained how researchers came to discover that Wolbachia block viral transmission.

The Eliminate Dengue Program started with lab experiments where Wolbachia-infected mosquitoes were released in cages filled with uninfected mosquitoes and grew to include field pilot studies, of which there are now six: Australia, Indonesia, Vietnam, Brazil, Colombia, and most recently, India.

Dr. Aliota is collaborating with the Eliminate Dengue Program in Colombia. The program first released Wolbachia-infected Aedes aegypti mosquitoes in the Colombia site, a city in the northwest region of the country, in May 2015. Dr. Aliota stated that Wolbachia-infected mosquitoes were released for a short period and then the bacteria were able to spread throughout the mosquito population. In October 2016, the Program announced that more than 90% of mosquitoes in the Colombia site.

In his presentation he stated that his research team, in cooperation with the Eliminate Dengue Program in Colombia, set out to discover if the wMel strain of Wolbachia would be successful in reducing the transmission of Dengue-related viruses by Aedes aegypti mosquitoes. They found that, in fact, this strain can successfully block viral transmission of Chikungunya and the Puerto Rican [PR] strain of the Zika virus.

The team infected mouse models with the PR strain and allowed the mosquitoes to bite them at peak viremia. Following this, the team collected mosquito tissues and tested them for Zika infection. In wild-type Aedes aegypti, which were not infected with Wolbachia, it was observed that “almost 100% of mosquitoes [were] infected at 4 days post-feeding but [there was] no dissemination or transmission.” The team found infection transmission in some mosquitoes at 7 days post-feeding, with the percentage of transmission steadily increasing after 7 days. On the other hand, in mosquitoes infected with the bacteria, there was “no infection dissemination or transmission” at 4 days post-feeding; at 7 and 10 days post-feeding, the virus was not detectable in mosquito saliva, meaning that there was no potential to transmit infection to the host.

Complementary results were observed in Wolbachia-infected Aedes aegypti with the Brazilian strain of the Zika virus. Dr. Aliota stated that “using the same experimental system” the team was able to test Wolbachia against Chikungunya, and found similar results.

DISCLOSURES

None

SOURCE

First International Conference on Zika Virus

Exclusive interview with Contagion^®

PRESENTATION

Session 5A: In The Pipeline

Wolbachia as a Novel Approach for the Control of Arboviruses Transmitted by Aedes aegypti