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Vaginal bacteria inhibit sexual transmission of HSV-2, possibly Zika

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NEW ORLEANS — Researchers at ASM Microbe presented findings on the effect of a healthy vaginal microbiome against sexual transmission of Zika virus and herpes simplex virus-2, or HSV-2.

A study by researchers at the University of Texas Medical Branch showed that vaginal microbiomes containing mostly Lactobacillus bacteria — considered important for a healthy vaginal system — inhibited sexual transmission of HSV-2 but did not inhibit Zika.

Megan Amerson



Some microbiomes that were deficient in Lactobacillus allowed for increased replication of Zika while other Lactobacillus­-deficient microbiomes significantly decreased replication. Doctoral student and study researcher Megan Amerson explained that the action against Zika depended on the specific bacterial profiles of the vaginal microbiomes.

According to the CDC, most patients acquire Zika through the bite of an infected female Aedes aegypti mosquito, but the virus also can be sexually transmitted by both men and women. However, little is known about why some women who are exposed this way develop viremia while others do not, Amerson said.

“We do know that if you have higher titers of Zika replication in the vaginal epithelial cells, it can move systemically from the vaginal tissue into the circulation. And with decreased titers, you’re less likely to see viremia,” she told Infectious Disease News. “We’re looking at possible ways to prevent sexual transmission of Zika.”

For their study, Amerson and colleagues used a novel 3D culture system — the first, they said, to support colonization by transplanted vaginal microbiomes from healthy donors. They colonized cultures with either Lactobacillus-dominant vaginal microbiota or microbiota lacking Lactobacillus and used sterile cultures as a control. Then they inoculated the cultures with either Zika or HSV-2 and measured viral replication 48 hours later with PCR.

HSV-2 replicated more in cultures that were colonized with microbiomes that had fewer Lactobacillus bacteria, which Amerson said was in line with clinical observations.

The findings were not so simple in cultures inoculated with Zika.

According to Amerson, the results depended on the species of bacteria present in the vaginal microbiomes. Vaginal microbiomes with Staphylococcus species hardly showed any Zika virus replication at all, whereas those with more Atopobium vaginae increased replication.

Amerson said that more than anything, their research was aimed at targeting future preventive methods for sexually transmitted viruses.

“We’re looking to see if there are any metabolites being produced by Staphylococcus species that are inhibiting viral replication of Zika,” Amerson said. “We also looked at cytokine profiles to determine if specific inflammatory pathways can be further investigated to see if they’re involved with replication or inhibition of Zika.” – by Gerard Gallagher

Reference:

Amerson MH, et al. Cultivated human vaginal microbiome communities impact Zika and herpes simplex virus replication in ex vivo vaginal mucosal cultures. Presented at: ASM Microbe; June 1-5, 2017; New Orleans.

Disclosure: The researchers report no relevant financial disclosures.