NEW YORK (GenomeWeb) – Molecular diagnostics developer GenArraytion has launched two assays to detect four regions of the Zika virus and discriminate it from other arboviruses and pathogens in mosquito vectors.
The Rockville, Maryland-based firm is among the first to launch such a multiplex test and is initially targeting public health labs performing vector surveillance. Meanwhile, firms such as Germany-based Genekam Biotech and Singapore-based Vela Diagnostics have launched research-use-only tests recently as well.
The GenArraytion test was launched in the context of an ongoing Zika outbreak in temperate climates that has led to travel advisories for pregnant women and new guidelines, issued today, to prevent sexual transmission of the virus after a recent confirmed case in Dallas. In a call to discuss these guidelines, US Centers for Disease Control and Prevention director Tom Frieden also described the importance of vector control measures.
In infected people, an RT-PCR can detect virus in blood out to about 10 days, while serology is used for later infections.
However, "a molecular test is the only way you're going to detect the mosquitoes that are infected, because mosquitoes don't make antibodies," GenArraytion's CEO and co-founder Paul Schaudies told GenomeWeb in an interview.
Vector control may ultimately become an important prevention method in the current Zika outbreak. "In order to stop the infection, you need to kill the mosquitoes," Schaudies said, adding that the GenArraytion test "allows the public health services to survey — collect mosquitoes, grind them up, and assay them — and determine where the infected mosquitoes are, so they can just target the infected ones."
The test comes in two varieties. There is a real-time PCR for standard thermocylers, such as the ABI 7500 or Cepheid SmartCycler, that can detect Zika as well as chikungunya and yellow fever, plus a single channel to report the presence of dengue virus types I through IV. The test is therefore a single real-time assay that "covers all of the human pathogens that are co-located, if you will, with the mosquito," Schaudies said, noting there are not any other tests that can do this currently available.
A second test, developed for the Luminex LX200 or the MagPix platforms, is a multiplex bead-based assay that can discriminate Zika as well as all four types of dengue, chikungunya, yellow fever, West Nile virus, Plasmodium falciparum, and tick-borne encephalitis virus.
For vector testing, researchers would grind up the mosquitoes in a mortar and pestle, do an RNA extraction, and then run the sample on the preferred test.
Scientists really don't know what is causing the microcephaly that has been associated with Zika infection, GenArraytion COO Doreen Robinson said.
"Since this mosquito can be a carrier of one or more of these viruses at one time, it may be that its just the Zika that's responsible for these negative consequences, or it could be some interaction between the viruses," she added.
"That's one of the reasons we feel it is so important to survey for all these pathogens at the same time."
The firm also developed the tests with high viral mutation rates in mind. The assays have one target for each quadrant of the virus' small genome. During development, an Agilent array was used to choose the strongest targets that gave the best coverage of the virus based on GenBank data. GenArraytion has also validated the RUO test on samples enriched with Zika virus from ATCC.
The firm has a background in US Department of Defense and Intelligence Department research, but has branched out into infectious disease test manufacturing more generally.
Over a period of 14 months spanning 2014 and 2015, it developed more than 80 PCR-based tests, Schaudies said. Perhaps because of this experience, or the small size of the Zika genome, test development for the Zika assay took only about one month, he said, noting the firm initially decided on the project on Jan. 9th, "did the bioinformatics over the weekend," and then ordered arrays.
GenArraytion was founded in 2007. It is a privately held, veteran-owned company and the work on the Zika virus is self-funded. The firm undertook a similar development process recently, developing an Ebola assay for five different targets, but "the field was a little more crowded and we were a little later to the game," Schaudies said.
The firm is now working closely with Luminex, and is planning to start discussions with the Association of Public Health Laboratories in the US.
It also continues to sell other tests. "We were part of the Global Biosurveillance Technology Initiative for the US Department of Defense where we developed mosquito panels as well as tick panels, so we have tests for malaria, Lyme disease, and for a lot of major vector-borne disease, both on Luminex as well as real-time PCR," Schaudies noted.
The firm is also developing molecular assays for PositiveID. "They have successfully tested many of our assays on their breadboard platform [and] GenArraytion will be shipping them a Zika assay for testing this month," he said.
Finally, GenArraytion has also arranged a meeting with the US Food and Drug Administration to begin discussing potential Emergency Use Authorization of the test, should EUA be issued for Zika virus.
"The FDA says contact us early," Schaudies said. "They are a very customer-driven organization and have been incredibly responsive. We will be working with them with the Zika and while we're there we'll talk about some of the other things that we've developed."
CDC guidelines
The CDC also addressed vector control during a call to discuss Zika guideline updates, with director Tom Frieden noting it is a challenging undertaking.
The agency updated previously issued guidelines to now recommend healthcare providers offer serological Zika testing to pregnant women who are asymptomatic but who have traveled to one of the countries where the outbreak is occurring. Testing can be offered two to 12 weeks after pregnant women return from travel, the guidelines state.
As a result of a recent case of likely sexual transmission of Zika, the agency also now recommends that men who travel to areas where Zika is spreading and who have pregnant sexual partners should use condoms or abstain from sexual intercourse until the pregnancy comes to term.
Frieden pointed out that researchers do not yet know how long Zika virus persists in semen, and the aim of the current guideline is to prevent pregnant women from becoming infected.
"The studies of viral persistence in semen will occur in many parts of the world, including in parts of the US with travelers who have come back and in Puerto Rico where we have some sites where we have been monitoring other viral diseases for some time," Frieden said.
The studies, however, are not simple and will take time. He noted that there are essentially two ways to test for virus in semen, real-time PCR and viral culture, and that the former is very sensitive but can also detect nonviable virus while the latter is specific but less sensitive.
Mosquito control is another possible preventative measure. In the US, it is often done by mosquito abatement districts, and they are quite variable, Frieden said. "Some of them do an absolutely superb job, and some of them less so, and that's why it is so important that we invest in systems to track and find mosquitoes," he said.
The agency also advises vector control professionals to use certain collection methods to enable downstream processing of mosquito samples with RT-PCR.
"This is not easy work," Frieden said. "Although mosquitoes that spread Zika are different than the ones that spread West Nile, having worked on [West Nile] for many years, the different aspects of mosquito control can be quite complex and labor intensive — when it comes to Zika ... it is not easy and it is not quick."
Control requires monitoring of larvae and adults, and that is "a labor-intensive, technically complex undertaking," he said, noting that the agency's experience with dengue suggests very high levels of mosquito control are required to drive down infection risk.
The Aedes aegypti mosquito vector, meanwhile is very aggressive, Frieden said. It bites more than five people in one blood meal and it bites relatively painlessly, "so you don't swat it and kill it," he said. It is also ideally suited for a crowded urban environment where there is standing water that can be "as small as a drop of water in a bottle cap where it can breed," and where it is challenging to avoid because the mosquito bites all day long, not just at dawn and dusk.
"Zika reminds us that nature is a formidable enemy — that's why we have to invest in laboratories, disease detectives, tracking systems, mosquito surveillance and control programs, in the US and around the world," Frieden said.Â