Medical Daily (10.29.2013)
An article in Medical Daily reported on research indicating that pregnancy could result in a faster-replicating strain of hepatitis C virus (HCV). Pregnant HCV-infected women face a 25-percent risk of passing the disease to their infants. Researchers from the Research Institute at Nationwide Children’s Hospital in Columbus, Ohio, followed two HCV-positive women for five years, during which time both women had two children.
The researchers examined the evolution of the virus before, during, and after the pregnancies. They found that immune processes during pregnancy combined with natural viral processes, resulting in a faster-replicating virus strain that one woman passed on during childbirth. HCV spreads by mutating certain parts of its genome, making it difficult for CD8-positive T-cells to find and destroy them. This process, called immune escape mutations, makes it difficult for the virus to replicate. During pregnancy, a woman’s immune system withholds T-cells to prevent them from attacking the fetus. The virus then is able to replicate without being attacked by T-cells. The virus does not need to mutate and the result is a stronger virus that replicates faster and is passed to the infant.
Dr. Jonathan R. Honegger, an infectious disease specialist and lead researcher of the study, noted that the findings provided a unique view of the effect of pregnancy on the mothers’ control of viral infections and demonstration of HCV’s ability to adapt to changing environmental pressures. The researchers are not sure whether the stronger, faster-replicating virus would be more harmful to the child in the longer term.
The full report, “Loss of Immune Escape Mutations During Persistent HCV Infection in Pregnancy Enhances Replication of Vertically Transmitted Viruses,” was published online in the journal Nature Medicine (2013; doi:10.1038/nm.3351)