Researchers have found a genetic risk factor that increases chances of a baby being born prematurely.
The study was conducted by University of California, San Diego School of Medicine scientists. They found that the absence of a gene that codes for a protein called Siglec-14 increases risk of premature birth. The protein helps immune cells indentify and kill Group B Streptococcus (GBS) bacteria.
Around 15 million babies are born preterm (before 37 weeks of pregnancy) every year, says the World Health Organization. According to the National Institutes of Health, preterm babies are at higher risk of learning disabilities, cerebral palsy, problems associated with breathing, vision and hearing loss and digestive problems.
GBS bacteria are found in the vagina of around 15 to 20 percent of healthy women. In some women, these bacteria can cause severe infections that can lead to meningitis in newborns, especially in premature babies.
"Pregnant women are universally screened for these bacteria during pregnancy and administered antibiotics intravenously during labor if they test positive to protect the infant from infection," said Victor Nizet, MD, professor of pediatrics and pharmacy and co-author, according to a news release. "Our research may explain why some women and their infants are at higher risk of acquiring severe GBS infections than others."
For the study, the team looked at two proteins on fetal membranes of the placenta. These proteins are associated with immunity. One of the proteins called Siglec-5 suppresses the immune system by binding to the foreign agent, whereas the other protein Siglec-14 activates immune reaction.
Siglecs are receptors found on immune cells. They work by identifying and binding to the sialic acids (sugar molecules) on our cells.
"We have one protein that tells the body to attack the pathogen and another that tells the body not to attack it," said Raza Ali, PhD, a project scientist in the Nizet laboratory and the study's lead author.
The presence of both proteins balances immune response and prevents excessive inflammation, which could be dangerous to the baby.
The team found the absence of the gene that codes for Siglec-14 (the activator) protein increases risk of premature birth. The reason for early birth could be the imbalance in immune response to the bacteria, researchers said.
Related studies have shown that the siglec gene interaction is unique to humans and is mutated in great apes. Also, loss of siglec14 reduces the risk of severe chronic obstructive pulmonary disease.
The study is published in the Journal of Experimental Medicine. National Institutes of Health funded the research.
Note- one of the study authors Ajit Varki has an equity interest in Sialix, Inc., which is exploring the possibility of using non-human sialic acid in developing drugs.