Babies of mothers who have had chickenpox are more immune

Maitri Porecha New Delhi | Updated on December 17, 2019 Published on December 17, 2019

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A team of researchers have discovered that viral DNA gets transferred to babies, giving them longer protection

Children whose mothers have had chickenpox may be naturally more immune to the disease as compared to kids who are freshly exposed to the virus.

This is because the babies born to the mothers who had contracted the disease in the past may harbour viral DNA in the blood, according to a study published in the journal Viral Immunology on Monday.

A group of Delhi-based paediatricians from St Stephen’s Hospital and scientists from the National Institute of Immunology (NII) studied pairs of 350 mothers and their newborns between June 2016 and June 2017 to ascertain this. Those mothers who had received blood transfusion during pregnancy or were vaccinated against chickenpox were not included.

First such study

This is the first time ever that experts have studied the DNA of pregnant mothers and their babies for presence of chickenpox virus.

“We have concluded that stress caused by pregnancy can reactivate hibernating virus to start freely floating in the mother’s blood. This is called ‘viraemia’. It is known that stress can induce viraemia in astronauts or in patients that undergo surgery, but this is for the first time that this has been ascertained in pregnant women and their babies,” said Jacob Puliyel, co-author of the study.

Chickenpox is spread by varicella-zoster virus (VZV), and so VZV DNA and antibodies (which fight off the infection) were isolated in the mother-baby pairs from their cord blood and their levels were analysed.

Two tests were run on the blood — antibody blood tests and polymerase chain reaction tests for DNA. While 15 per cent of all mothers had antibodies, and 16 per cent were borderline-positive, 16.9 per cent babies were positive and 18 per cent borderline-positive.

As far as DNA tests went, they were performed only on 73 mother-baby pairs as PCR testing is expensive, the authors said. It was revealed that mothers who have had VZV infection in the past can transmit free-floating VZV DNA and antibodies to their babies. The researchers observed that babies of those mothers whose viral load was high had higher loads of viral DNA. This is a good thing, the authors said.

Viral DNA transferred

The present understanding is that mothers provide their babies protection against a variety of common infections, by transferring ready-made antibodies to them. “Such protection to the baby lasts for 12 to 15 months, but we have discovered that even viral DNA gets transferred to babies,” Puliyel said.

“Thus, babies develop more long-lasting active immunity with the transfer of chickenpox DNA from mothers — more than the short-term passive protection provided by the transfer of ready-made antibodies,” said Pramod Upadhyay, Scientist at NII.

The paper assumes that in cases where babies have high viral DNA, active antibodies are actively developed; however, it says that the exact nature of antibody-viral DNA interaction should be studied in further detail. “This also explains why chicken pox is a mild infection at less than fourteen years of age,” the study states.

Puliyel said, “Kids till the age of 14 develop milder form of chickenpox, as perhaps transfer of viral DNA from their mothers accords them more strength to develop active long lasting immunity. As an adult though, that immunity may wean away, which explains why adults develop more serious versions of chickenpox, like shingles, at 60 or 80 years, which is more painful.”

Published on December 17, 2019
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