Researchers at the University of California, San Diego School of Medicine have discovered a genetic risk factor for premature birth. The risk factor is related to a gene that codes for a protein that the scientists have found helps the body’s immune cells recognize and fight Group B Streptococcus (GBS) bacteria. These bacteria are found in the vagina or lower gastrointestinal tract of approximately 15% to 20% of healthy women, but they may cause life-threatening infections, such as sepsis or meningitis, in newborns, especially those born prematurely.
In the study, published online in the May issue of the Journal of Experimental Medicine, scientists identified two proteins on fetal membranes of the placenta that are involved in immune function. One of the proteins (known as Siglec-5) binds to the GBS pathogen and suppresses immune response to the microbe, while the other protein (known as Siglec-14) binds to the pathogen and activates killing of the bacteria.
The gene for Siglec-14 is missing in some individuals, and the researchers have found that fetuses that lack the Siglec-14 protein are at higher risk of premature birth; this is probably due to an imbalanced immune response to the bacterial infection. “Our research may explain why some women and their infants are at higher risk of acquiring severe GBS infections than others,” says study co-author Victor Nizet, MD.
The scientists believe that identifying the mechanisms of Siglec protein action may help in designing therapeutic targets against bacterial infections that are becoming increasingly resistant to antibiotics and could have important implications for other disorders, such as blood clotting, chronic diseases, and HIV infections. Read the study abstract.
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