How glycoproteins get damaged during bacterial vaginosis

January 28, 2013 § 2 Comments

Bacterial vaginosis in pregnant women could lead to preterm labor and birth. Image from http://en.wikipedia.org/wiki/File:Premature_infant_with_ventilator.jpg

Bacterial vaginosis in pregnant women could lead to preterm labor and birth. Image from http://en.wikipedia.org/wiki/File:Premature_infant_with_ventilator.jpg

Bacterial vaginosis is an imbalance of vaginal bacteria and linked to a variety of serious health problems in women. In a recent paper in the Journal of Biological Chemistry, researchers described how a class of enzymes involved in bacterial vaginosis attacked glycoproteins in vaginal mucus.

Bacterial vaginosis can be an asymptomatic condition, meaning that women can walk around without knowing that the bacterial composition in their vaginal mucus is out of whack. But, explains Amanda Lewis at Washington University in St. Louis, who was the senior author on the paper, the condition in pregnant women is known to be associated with an elevated risk of preterm birth. “Despite being the most common reason for a woman to seek treatment from her (obstetrician/gynecologist), bacterial vaginosis is not often discussed,” she says.

Researchers know that in bacterial vaginosis the vaginal mucus shifts away from its normal state. The shift is caused by the action of hydrolytic enzymes, which researchers think come from bacteria, that chew down glycoproteins in the vaginal mucus. These glycoproteins have a protective function.

However, “despite the clinical significance of bacterial vaginosis, experimental systems for studying the condition are lacking, the bacteria involved are difficult to grow in the lab, and other tools used in studies of infectious diseases are difficult to apply since bacterial vaginsos is a polymicrobial condition,” says Lewis.

So she and her colleagues decided to use vaginal swabs to observe the breakdown of protective vaginal molecules. They observed that sialidases attacked the mucus glycoproteins and removed their sialic acid residues. “Glycobiologists have known for a long time that once sialic acid residues are removed other glycosidase enzymes can better act on carbohydrates underneath, leading to more extensive deglycosylation of proteins,” says first author and Lewis’ husband, Warren Lewis. This means that the protection offered by these vaginal glycoproteins is destroyed.

Lewis says her group will be working to identify which bacteria produce the sialidases. “We are also interested in developing a better understanding of which combinations of enzymes and bacteria produce the greatest degree of mucus destruction,” she says, adding they would like to understand which combinations are correlated with symptomatic bacterial vaginosis or adverse outcomes, such as preterm birth.

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