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    Premature Birth Genetic Risk Factor Found
    By News Staff | May 5th 2014 09:47 PM | 1 comment | Print | E-mail | Track Comments
    A gene that codes for a protein that scientists have found helps the body’s immune cells recognize and fight Group B Streptococcus (GBS) bacteria has been implicated in premature birth risk.

    The 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, such as sepsis or meningitis in newborns, especially those born prematurely.

    In the study, the 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. Siglecs are cell surface receptors found typically on immune cells. They recognize (bind) sialic acids - sugar molecules that densely coat our cells.


    Group B Streptococcus bacteria (green) are shown binding to siglec proteins (red) that densely cover the surface of human immune cells (human cell nuclei in blue). Credit: UC San Diego

    “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. “Our research may explain why some women and their infants are at higher risk of acquiring severe GBS infections than others.”

    “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.

    Scientists believe that the pair of proteins together helps balance the body’s immune response to pathogens, by directing some antimicrobial response without provoking excessive inflammation.

    “Identifying the dual role of these receptors and how they are regulated may provide insight for future treatments against GBS,” Ali said.

    Interestingly, 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, likely due to an imbalanced immune response to the bacterial infection.

    “We found this association in GBS-positive but not GBS-negative pregnancies, highlighting the importance of GBS-siglec crosstalk on placental membranes,” said Ajit Varki, MD, Distinguished Professor of Medicine and Cellular and Molecular Medicine and study co-author.

    For reasons not completely understood, GBS infections are not found in any other animals, including chimpanzees, which share 99 percent of human protein sequences. “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.”

    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.

    Co-authors include Jerry J. Fong, Aaron F. Carlin, Rebecka Linden, Mana Parast, UC San Diego; Tamara Busch and Jeffrey Murray, University of Iowa; Takashi Angata, Academia Sinica, Taiwan and Thomas Areschoug, Lund University, Sweden.

    Published in the Journal of Experimental Medicine.

    Comments

    This is an interesting study! My daughter Joy was born at 23 weeks last year. Due to modern medicine and prayers she is doing great today. I hemorrhaged at 17 weeks for the first of 4 times because of 100% placenta previa, which turned into placenta accreta (which I believe was caused by 3 prior c-sections). After she came home from 121 days in the NICU, I wrote a memoir called "From Hope To Joy" about my life-threatening
 pregnancy and my daughter's 4 months in the NICU (with my 3 young sons at 
home), which is now available on both the Amazon and Barnes&Noble websites. It was quite a roller 
coaster that I am certain some of you have been on or are currently riding on. My mission is to provide hope to women struggling with
 high-risk pregnancies, encourage expectant mothers to educate themselves before 
electing cesarean deliveries, provide families of premature babies a realistic 
look at what lies ahead in their NICU journey, and show that miracles can 
happen, and hope can turn into joy.
 Please see my website http://www.micropreemie.net and www.facebook.com/jenniferdegl and watch our amazing video of my daughter’s miracle birth and life at: http://www.youtube.com/watch?v=V_hleySg-iU
    
Thank you.