An advance in the race to stop birth defects caused by Zika-infected mothers has been made by a team of researchers from Rensselaer Polytechnic Institute in Troy, New York. They have identified the process Zika uses to gain entry into the placenta, and published their findings in the journal Biochemistry.
Using their past experience conducting research on dengue virus (which is in the same Flavivirus family as Zika), the team—headed by Robert J. Linhardt and led by graduate student So Young Kim—looked to see if Zika's viral coating could bind sugar molecules. Sugars, called glycosaminoglycans, found on host cells are the target other flaviviruses use to attach to the cells, gain entry, and cause an infection.
The researchers extracted sugars from human placental and brain tissues and looked at the binding to proteins in the Zika viral envelope. They found a placental sugar, called chrondroitin sulfate, that bound tightly to the virus. Zika's binding to sugars from the brain was weaker.
Since Zika causes brain abnormalities in infected fetuses, the researchers are now developing a system to identify fetal brain sugars that Zika might attach to.
The research team also wants to come up with a way to block the binding of the virus with placental sugars, in an effort to protect the fetus from the infection.
In earlier work, the researchers developed a sneaky way to use the influenza virus's sugar preference against it. They created a nanoparticle—a tiny inert particle—that would kill the influenza virus, and they coated it in sugar. When given to mice, the virus-killing, sugar-coated nanoparticle prevented influenza infections. Now, the researchers are trying a similar approach with the Zika virus.
A significant stride has been made toward gaining an understanding of how Zika gets into placental cells to infect developing fetuses—and none too soon. With warmer weather coming to the US, the infection rate may ramp up and time to come up with a tool to fight this fetal infection is getting short.
From January 1, 2015 through April 5, 2017, 5,197 cases of Zika in the US were reported to the Centers for Disease Control and Prevention.
Of those, 4,901 cases were in people returning from travel to affected areas and 222 cases were presumed to be acquired through mosquito bites in the US (216 in Florida and six in Texas), and 1,716 cases occurred in pregnant women, with 56 infants.
The Aedes aegypti mosquito is the villain that carries and transmits the Zika virus, but the disease can also be transmitted congenitally, sexually, and through bodily fluids.
In healthy adults, Zika infections are usually mild and people experience fever, rash, headache, and joint pain for a couple of weeks. Some people have no symptoms at all.
Zika can be passed through sex with an infected partner. That means that infections in either females or their male partners can be a threat to developing fetuses, where infections have been associated with microcephaly—abnormally small brains—in newborns.
There is no treatment for Zika, so prevention is paramount in the effort to stop infection and transmission. Using an EPA-recommended insect repellant and using condoms to protect against sexual transmission are the best ways to prevent a Zika infection.
But prevention methods aren't 100% effective and to mitigate the risk to pregnancies, researchers have been working feverishly to find a way to stop Zika.
Vaccine development and insect control activities are ongoing, but a better understanding of how the virus infects—and particularly how it crosses the placenta—might provide us with the information we need to be able to stop Zika in its tracks.
Now that we know the virus binds tightly to a sugar molecule on the placenta, that can be investigated as the way Zika gains entry into those cells. So, Linhardt and his team are ramping up their research.
"We think Zika is going to come back with a vengeance this summer. That's why we are working really hard to understand Zika as best as we can, as fast as we can," said Linhardt in a press release from the American Chemical Society.