Scientists at the UCSD School of Medicine published a study in the Journal of Experimental Medicine on May 5 showing a discovered genetic risk factor for premature births is related to genes that fight Group B Streptococcus bacteria. According to a news release by the UCSD Health System, these bacteria are found in the vagina or lower gastrointestinal tract of approximately 15 to 20 percent of healthy women but may cause life-threatening infections in newborns, especially those born prematurely.

The human body has two receptors that tell the body how strongly to react to the bacteria. One of the receptors, siglec-5, indicates that there should not be an immune response while siglec-14 encourages a response. The two receptors work together to organize balanced responses to detected pathogens, although certain pathogens, such as streptococcus, can avoid innate immune responses by camouflaging their surfaces with sugars that mimic the host’s cells.

In the clinical study, UCSD scientists looked at the occurrence of premature births and found that siglec-14 deficient fetuses are at a higher risk of prematurity, likely due to an imbalanced immune response to GBS infection.

Dr. Ajit Varki, study co-author and distinguished professor of medicine and cellular and molecular medicine said in an interview with Bioscience Technology that the prematurity factor, along with the GBS and corresponding receptors, have been found to be human specific.

“The expression of the two siglec proteins on the fetal membranes is also unique to humans,” Varki said. “Our study offers intriguing insights into why certain bacterial pathogens may produce uniquely human diseases.”

Dr. Victor Nizet co-author and professor of pediatrics and pharmacy noted that having both receptors does not prevent all infections or diseases.

“An earlier study showed that the presence of both receptors made you more at-risk of having chronic obstructive pulmonary disease,” said Nizet. “There are upsides and downsides to having both.”

Nizet said women who are found to have one receptor may be given a different treatment than those with two receptors.

“In the future, we can imagine our approach to preventing prematurity and infection in infants will take into account this new information, and that management and therapy will be catered to the individual,” Nizet said.

Additionally, other papers concerning similar research have shown that both receptors were more likely to be present in some demographic populations than others.

“A previous paper showed that both of these receptors are found less frequently in the African population or Asian populations compared to Caucasian population,” Ali said. “However, there is no data to demonstrate this.”