Zika’s resurgence has spurred an uptick in both public fear of the virus and research into how it functions. A team of researchers from Emory University dove into the pathology of the virus to determine precisely how it passes through the placenta of a pregnant woman and puts her baby at risk. The results showed that Zika can infect and replicate in immune cells from the placenta without killing them — allowing the virus to move on to infect the developing brain of a growing fetus.
“Our results substantiate the limited evidence from pathology case reports,” said Dr. Mehul Suthar, the study’s senior author and an assistant professor of pediatrics at Emory University School of Medicine, in a press release. “It was known that the virus was getting into the placenta. But little was known about where the virus was replicating and in what cell type.”
The team, led by Suthar and pediatric infectious disease specialist Dr. Rana Chakraborty, found that had the ability to infect Hofbauer cells. A type of macrophage, these cells function by swallowing up smaller cells and particles. In addition, could infect a type of placental cell called cytotrophoblasts — though it could not invade these cells as readily, and could only do so after a couple days.
The researchers derived the cells for the study from full-term placentas taken from healthy volunteers. They noted that in some women the placenta may be more vulnerable to than in others, since the level of viral spread varied significantly from donor to donor.
“Not every pregnant woman who is infected by Zika transmits the virus to her fetus,” Suthar explained. “Host genetics and non-viral factors, including nutrition and microbiota, as well as timing may be influencing infectivity. A better understanding of these factors could allow the design of preventative measures, and eventually antiviral therapies.”
Suthar said may be unique in its ability to cross the placental barrier and infect a fetus’ cells, compared to other related viruses like dengue virus and West Nile virus.
Hofbauer cells are fetally derived, which is unique among maternally derived immune cells found in the placenta. Previous studies have found they may be less prone to inflammatory responses than other immune cells. Still, Suthar’s team found signs of antiviral and inflammatory response in the cells, and intend to continue their work in investigating their immunology.
“We need to answer questions such as: What are the receptors that allow the virus to enter Hofbauer cells?” Suthar said. “Do these cells change in their immune status during the different phases of pregnancy?”
Source: Quicke K, Bowen J, Rimawi B, Pulendran B, Schinazi R, Chakraborty R, et al. How Infects the Placenta. Cell Host & Microbe. 2016.
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