According to a study published Jan. 25 in The Lancet
Infectious Diseases, concentrations of specific
vaginal bacteria are associated with increased risk
of HIV acquisition in African women.
IMAGE - National Institute of Allergy and
Infectious Diseases
Scanning electromicrograph of an HIV-infected T
cell. (The image is modified from the original by
the NIAID.)
The finding could inform test interventions to
reduce or eradicate certain bacteria that appear to
increase women’s HIV susceptibility.
Early in the HIV/AIDS epidemic, men were thought to
be at a higher risk for the disease.
Today, according to the World Health Organization,
about half of the 35 million people living with HIV
are women.
In Africa in 2015, 56 percent of new HIV infections
were women.
Prior to this study, it was posited that bacterial
vaginosis, or the condition when there is too much
of a particular bacteria in the vagina, might
contribute to HIV transmission and the
disproportionate burden of HIV infection in African
women.
Because of new advances in molecular biology,
researchers’ understanding and categorizations of
vaginal bacteria types have catalyzed new studies on
the association between specific vaginal bacteria
and HIV acquisition.
Although research in this area has found strong
associations, the new research investigates absolute
concentrations of bacteria for more defined risk
analysis.
Primary authors in the University of Washington-led
study were Scott McClelland, professor of medicine,
epidemiology and global health; Jairam Lingappa,
professor of medicine and global health; and David
Fredericks, professor of medicine.
“It’s important to measure absolute concentrations
of bacteria for a couple of reasons,” McClelland
said. “First, there can be important differences
between relative abundance, which is measured by
broad range (polymerase chain reaction) and deep
sequencing, and absolute concentration, which is
measured using quantitative PCR assays. Second,
relative abundance comparisons are more likely to
overlook potentially important differences in
species that have low relative abundances.”
According to McClelland, absolute concentrations of
bacteria provide a more targeted approach to
identify specific vaginal bacteria.
For a decade, the team of researchers analyzed data
from five cohorts of eastern and southern African
women, including female sex workers, pregnant and
postpartum women, and women in mixed-status
relationships.
The data identified the specific vaginal bacteria
communities that were common among those who
acquired HIV.
“These results suggest that high concentrations of
certain bacteria may increase women’s susceptibility
to HIV,” McClelland said.
Between November, 2004, and August, 2014, scientists
identified 87 women who acquired HIV infection
(cases) and 262 controls who did not acquire HIV
infection.
Vaginal bacterial community diversity was higher in
women who acquired HIV infection than in
seronegative controls.
Seven of the 20 taxa showed significant
concentration-dependent associations with increased
odds of HIV acquisition:
Parvimonas species type 1 and type 2,
Gemella asaccharolytica,
Mycoplasma hominis,
Leptotrichia/Sneathia,
Eggerthella species type 1 and
vaginal Megasphaera species.
“This opens up the possibility of testing prevention
interventions targeted towards reducing or
eradicating these vaginal bacteria in women at risk
for HIV infection.”
Higher diversity vaginal bacteria communities are
more common in women of African and Hispanic descent
than women of Asian or European origin.
This helps inform population-level differences in
HIV transmission and prevalence.
Additionally, because bacterial vaginosis is
extremely heterogeneous (with multiple potential
causes), defining individual vaginal bacteria that
are associated with HIV risk can provide specific
targets and future strategies for HIV prevention
research.
For more information
Evaluation of the association between the
concentrations of key vaginal bacteria and the
increased risk of HIV acquisition in African women
from five cohorts: a nested case-control study
The Lancet - Infectious Dideases
Link...
University of Washington - UW Medicine
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