Gut microbe may help screen for 'bubble boy disease' SCID

Date: Oct-03-2014 Researchers have discovered a possible biomarker that could lead to a noninvasive

newborn test for severe combined immune deficiency - or SCID - once referred to as "bubble boy

disease." The researchers found baby mice with defective immune systems have higher levels of a gut

microbe that can be detected in feces.

Although SCID affects less than 0.1% of the population, the genetic disorder is typically fatal to children if they are not diagnosed and treated in their first year.

The term "bubble boy" was used to describe David Vetter, the boy from Texas who touched the

hearts of a nation and beyond. David died 30 years ago after living all his short 12 years of life

in a germ-free, plastic bubble because he was born with SCID - a condition that robbed him of an

immune system.

Although SCID affects less than 0.1% of the population, the genetic disorder is typically fatal

to children if they are not diagnosed and treated in their first year.

Since David's death, doctors and researchers have improved treatments for children with SCID. If

diagnosed early in life, before the onset of infection, a bone marrow transplant can successfully

treat the disorder. Many children diagnosed with SCID who receive bone marrow transplants manage

to grow up, go to school, and for the most part lead very nearly normal lives.

Babies with SCID can appear perfectly healthy when they are born. Early detection relies on

screening a newborn's blood sample and is not routinely performed. According to the Centers for

Disease Control and Prevention (CDC) only 16 states currently screen for SCID.

Now, writing in The ISME Journal, researchers from Virginia Tech, Blacksburg, describe

how using laboratory mice they discovered a potential biomarker for a noninvasive test for SCID

that looks for a microbe on the fecal matter of infants.

Co-author Xin M. Luo, an assistant professor of immunology at Virginia-Maryland College of

Veterinary Medicine, says:

"If SCID is not detected, children cannot live past their first year. Now, we may have a

noninvasive way to screen for this disease because this microbe may be present only in negligible

amounts in healthy, young children. If larger populations of the microbe are present, quick

examination is needed to prevent a potentially deadly emergency."

Prof. Luo and colleagues compared the gut microbes of healthy baby mice with those of mice with

a defective immune system before and after weaning. Using gene sequencing, they found the immune-defective mice had higher gut levels of a bacterium called Akkermansia muciniphila.

This bacterium is also present in the human gut. Although only recently discovered, it has been

around for a long time, says the team who also notes that use of antibiotics seems to spur levels of

this microbe, suggesting it thrives under conditions that kill other microbes.

When the team performed bone marrow transplants and gave the immune-defective mice an adaptive

immune system, their gut levels of A. muciniphila returned to normal.

They also found higher levels of the bacterium only occurred in younger mice and gradually

subsided as they aged.

Prof. Luo says the discovery is interesting because "it means we can potentially screen for this

microbe at an early age to find defects in the immune system."

The researchers have filed a provisional patent for a screening tool based on the biomarker and

are now working with a pediatrician to test for the bacterium in fecal samples from human

infants.

The effect of gut microbes on the immune system has featured in many new discoveries in recent

years. For example, in November 2013, Medical News Today learned how researchers in Japan

found a mechanism through which a fatty acid in gut bacteria boosts

the immune system and reduces inflammation. But in their investigation, Prof. Luo and

colleagues looked in the other direction and asked "How does the immune system affect gut

microbes?"

Written by Catharine Paddock PhD

Not to be reproduced without permission.

Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.