Drug blocks Zika pregnancy threat

Women who contract Zika when they're pregnant are at risk of the infection spreading to the baby's brain and causing the condition microcephaly. Recent predictions suggest that more than a million pregnant women may be at risk of infection across the Americas in the next few years. Now, US scientists have discovered that a drug that's already licensed for use in pregnancy can block the spread of Zika virus from a mother's bloodstream into the developing baby. Chris Smith spoke to Indira Mysorekar from the University of Washington in St Louis...

Chris - To kick us off this week, some good news about Zika virus. Women who contract Zika when they're pregnant are at risk of the infection spreading to the baby's brain and causing the condition microcephaly – a small head. Recent predictions suggest that more than a million pregnant women might be at risk of infection across the Americas in the next few years. Now, scientists have discovered that a drug that's already licensed for use in pregnancy can actually block the spread of Zika virus from a mother's bloodstream into her developing baby. It actually stops the virus from getting into the placenta that links the baby to its mother. From Washington University in St Louis, Indira Mysorekar…

Indira - Normally, the placenta is a fantastic barrier. For the most part, babies are born fine, normal. We found that the reason the virus was causing such terrible problems in the babies was because it was infecting the placenta and then from there directly, it could go into the baby’s circulation, and affect the baby’s brain. Knowing this, we started looking into – how is it that the virus is able to do that? There is essentially a garbage recycling system that’s found in the placenta as in other cells. This system is important – just housekeeping, cleaning up of the cell, and taking care of the bad guys or anything that’s broken and we found that the virus was essentially taking advantage of the system. And so, that led us to then looking at drugs that could block the system and maybe that way, block the ability of Zika to infect the baby.

Chris - So can we unpack this slightly then? Explain a bit more about what this garbage system is that the virus is exploiting and how.

Indira - Yes. Pretty much every cell in our body, all different kinds of cells have this garbage recycling system. Again, this is there to essentially protect us but many, many viruses and bacteria have developed ways to hijack the system and it turned out that Zika is no exception. It’s actually a little bit counterintuitive but it ramps up this garbage recycling system because we think it needs the end products of the clean-up and is able to use it to grow. so then we found this drug which happens to be used as an antimalarial – hydroxychloroquine. This drug has been known to block this recycling system. So we treated our animals that had been infected with the virus - pregnant animals - with this drug and found that within a course of a few days, it was completely able to block virus’ ability to grow in the placenta and is able to block any effects on the foetus.

Chris - So you take these pregnant – in this case, you're doing this on experimental animals – you administer this anti-malarial drug, hydroxychloroquine, this we know because people have studied this for years, we know it inhibits this garbage recycling system in cells.

Indira - That is correct.

Chris - When it’s doing that, the virus cannot penetrate through the placenta. It stops it infecting the placenta and that’s its relay station into the baby so the baby is indirectly protected.

Indira - That is correct.

Chris - Is it safe in pregnancy though because many, many people, when they're pregnant, they're very worried about taking drugs for obvious reasons. Is this drug safe?

Indira - Yeah. It has been shown to be safe in pregnancy. It has – in the United States – been FDA approved and obviously, as an anti-malarial, it’s used all over the world. Additionally, this drug is used to treat pregnant women who have lupus. The baby is followed and there doesn’t seem to be any adverse consequences to the baby as far as we know.

Chris - How long is the window period? By that, I mean after an individual contracts Zika infection, how long have you got to intervene with this therapy before it potentially can leapfrog into the baby via the placenta?

Indira - Excellent question. We don’t have all the answers yet, but from our studies, we can say that if we treat the infected animals almost immediately or a day after the infection, we’re able to block the infection.

Chris - Because one of the problems with Zika is that more than 80 per cent of people who catch it have no symptoms whatsoever. So if we relied on people reporting, “I might have been exposed” then we’re going to miss the vast majority of cases. So we would probably have to just encourage people at risk of infection to take this throughout their pregnancy, wouldn’t we?

Indira - That is correct. that’s the one thing that we would definitely have to test because even though hydroxychloroquine has been shown to be safe even in the first trimester of pregnancy, there have been no studies that show what happens if one takes hydroxychloroquine throughout the course of one’s pregnancy.