November 6, 2013
Did you know that a process that protects babies in the womb can also help hepatitis C replicate more quickly? So says a recent study conducted at the Research Institute at Nationwide Children's Hospital and published in Nature Medicine last month. Hepatitis C (HCV) -- sometimes called a "twin epidemic" to HIV, in part because roughly a quarter of people living with HIV in the U.S. are coinfected with it -- is not easily transmitted from a woman to her baby, and about 25 percent of babies clear HCV infection on their own. This is a good thing, since there's currently no way to prevent vertical HCV transmission, and most key treatments for HCV are not safe to take while pregnant or even while trying to conceive, whether it's the woman or man taking them. Transmission to babies happens in about 3 to 5 percent of pregnancies among women living with HCV. But when it does happen, according to this study, babies may be acquiring a hardier version of the virus.
One of the many natural changes a woman's body undergoes during pregnancy is that her T cells are restrained, so that her body won't think her fetus is foreign tissue and attack it. Meanwhile, HCV tricks the immune system by mutating to hide from attack by T cells -- specifically CD8+ T cells, which help people clear acute HCV on their own -- in what are called immune escape mutations. In the 60 to 80 percent of cases in which people don't clear HCV infection, those escape mutations can slow the virus' ability to replicate.
The researchers in this study followed two women living with HCV over five years, in which each woman had two children; the doctors were able to observe their viruses before, during and after pregnancy. They saw that, unlike "regular HCV," "pregnant HCV" has more freedom to replicate because of those restrained CD8+ T cells. As a result, once "pregnant HCV" is vertically transmitted to a baby (which it was, in the case of one woman in the study), it's particularly good at replicating.
In the hospital's statement regarding the study, lead investigator Jonathan R. Honegger, M.D., said:
We found that better replicating versions of the virus emerged during pregnancy, and these 'fit' viruses were passed to the babies. This surprised us because the virus' immune escape mutations are usually stable in a patient The loss of these immune escape mutations from HCV during pregnancy provided strong evidence that the immune changes of pregnancy, intended to protect the fetus, significantly impaired the ability of CD8+ T cells to exert pressure on the virus.
However, researchers did observe that the women's viral loads dropped rapidly within three months after they gave birth, and the virus' immune escape mutations returned, which indicates that T cells get their HCV-fighting groove back once pregnancy ends.
Is acquiring a faster-replicating variety of HCV a boon to the baby or the virus? And what bearing could this new information have on HCV treatment and prevention? The researchers hope to answer these and other questions as they follow a larger group of pregnant women living with HCV -- armed with the "unique insight into the impact of pregnancy on the mothers' control of viral infections" that these new findings provide.
Olivia Ford is the executive editor for TheBody.com and TheBodyPRO.com.