A common virus may be linked to heart problems in fetuses

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A common virus that typically causes only mild symptoms in adults might lead to heart defects in developing human fetuses, a recent study finds. Previous research has suggested that the virus, called coxsackievirus B, may be linked to miscarriages in early pregnancy. But many questions remained about the specific threat the virus poses to developing fetuses. (Another form of the virus, called coxsackievirus A, causes hand, foot and mouth disease).
The new findings, presented last month at the American Heart Association’s Scientific Sessions annual meeting, suggest that coxsackievirus B infection in pregnant women may be linked with heart defects in fetuses.
“Because it’s such a common virus and it’s known to have effects on adults, [we thought] it could be problematic in fetal stages, too,” said lead study author Vipul Sharma, a postdoctoral fellow in the department of surgery at Washington University School of Medicine in St. Louis. (In adults, coxsackievirus B symptoms are typically mild, though in rare cases the infection has been linked to more severe symptoms, such as myocarditis, or inflammation of the heart muscles, Sharma noted.) To learn about the effects in fetuses, the researchers started in mice.
In the first part of their study, they infected pregnant mice with one strain of the virus at different doses and at different points in fetal development correlating to human pregnancy. They found that 60 percent of the infected mice had fetuses that developed a heart defect, the most common defect being a form of ventricular septal defect. In humans, this defect is among the most common types, and it is characterized by a hole in the septum — the wall that separates the left side of the heart from the right. The septum protects deoxygenated blood from mixing with oxygenated blood, but if the hole is big enough, mixing occurs, and the body may not get enough oxygenated blood, Sharma told Live Science.
The team found that the timing of infection was also important, and the risk of developing heart defects was highest if the pregnant mice were infected at a time corresponding to “early pregnancy” in humans. The coxsackievirus works by binding to the Coxsackie-Adenovirus Receptor (CAR), which is found at high levels in mice fetuses’ hearts and brains, Sharma said. And though the presence of this receptor gives the virus free reign to infect the body, without it, studies have shown that mouse fetuses don’t survive, Sharma said.

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