Vaginal bacteria may influence effectiveness of anti-HIV drugs, study suggests
The make-up of a woman’s vaginal bacteria may influence the effectiveness of drugs that ward off the human immunodeficiency virus (HIV), research suggests.
Pre-exposure prophylaxis (PrEP) may be prescribed to HIV-negative people who are at high risk of catching the infection, for example those with HIV-positive partners. Taken before exposure, the tablet “blocks” HIV from taking hold.
Studies have shown the drug regimen reduces the risk of viral transmission via sex by around 99% when taken “consistently”.
Research has suggested, however, this high efficacy applies when men have intercourse with men, with PrEP being found to be less effective in women.
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To learn more, scientists from the University of Minnesota analysed vaginal samples from 44 women with and without bacterial vaginosis (BV); an extremely common condition caused by an imbalance of bacteria that can lead to itching, discharge and discomfort.
Results suggest the bacteria associated with BV can break down PrEP drugs, potentially reducing their efficacy.
BV is caused by a change in the natural balance of bacteria in the vagina.
While its onset is not fully understood, the condition is more common in women who are sexually active, have recently changed partners, have a “coil” contraceptive or use perfumed products around their genitals.
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BV is reportedly “the most common cause of vaginal symptoms among women” in the US, however, more than four in five (84%) experience no discomfort. According to the NHS, BV only causes symptoms in 50% of cases.
A 2017 UK study suggested nearly half (48.6%) of women experience BV over a 10-month period.
While not everyone develops symptoms, BV raises the risk of sexually-transmitted infections (STIs) and therefore should be treated via antibiotics.
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Studies have suggested an imbalance to vaginal bacteria raises a woman’s risk of HIV and alters the effectiveness of PrEP.
In the UK, the only approved PrEP drug is made up of the two medicines tenofovir and emtricitabine. The Minnesota scientists analysed this regimen, as well as others.
After looking at women with and without BV, the laboratory study revealed certain PrEP drugs were broken down in the samples taken from those with the vaginal condition.
The scientists then exposed the samples to HIV, along with PrEP.
Results – published in the journal PLOS Pathogens – revealed the BV cells were more likely to become infected with the sexually-transmitted virus, possibly due to the break down of the preventative drugs.
“Women’s health, and factors that contribute to health and disease prevention in women, are grossly under studied,” said study author Dr Nichole Klatt.
“This study demonstrates the critical need to develop better treatments for bacterial vaginosis, and in general, to promote more studies of women’s health.”
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In the UK alone, 105,200 people were thought to have HIV in 2019. Of these, around one in 16 were unaware they carried the infection.
HIV is treatable if caught early, with 97% of those on therapy in the UK reportedly being virally suppressed, meaning they cannot pass the infection on.
Left untreated, however, HIV can develop into acquired immune deficiency syndrome (Aids).
This occurs when the immune system is so severely damaged by HIV, the patient is at risk of life-threatening infections and diseases.
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