Vaginal dysbiosis and pre-exposure prophylaxis efficacy

A systematic review of adherence to oral pre-exposure prophylaxis for HIV - how can we improve uptake and adherence?

Introduction

Oral pre-exposure prophylaxis (PrEP) is an effective strategy to reduce the risk of HIV transmission in high risk individuals. However, the effectiveness of oral pre-exposure prophylaxis is highly dependent on user adherence, which some previous trials have struggled to optimise particularly in low and middle income settings. This systematic review aims to ascertain the reasons for non-adherence to pre-exposure prophylaxis to guide future implementation.

Methods

We performed structured literature searches of online databases and conference archives between August 8, 2016 and September 16, 2017. In total, 18 prospective randomized control trials and implementation studies investigating oral pre-exposure prophylaxis were reviewed. A structured form was used for data extraction and findings summarized regarding efficacy, effectiveness, adherence and possible reasons for non-adherence.

Results

Adherence varied between differing populations both geographically and socioeconomically. Common reasons for non-adherence reported over multiple studies were; social factors such as stigma, low risk perception, low decision making power, an unacceptable dosing regimen, side effects, and the logistics of daily life. Oral pre-exposure prophylaxis with included antiviral regimens was not associated with a high risk of antiviral resistance development in the reviewed studies.

Conclusion

Our findings indicate that oral pre-exposure prophylaxis should be delivered within a holistic intervention, acknowledging the other needs of the targeted demographic in order to maximise acceptability. Socioeconomic factors and poor governmental policy remain major barriers to widespread implementation of pre-exposure prophylaxis.

Genital inflammation undermines the effectiveness of tenofovir gel in preventing HIV acquisition in women

Several clinical trials have demonstrated that antiretroviral (ARV) drugs, taken as pre-exposure prophylaxis (PrEP), can prevent HIV infection¹, with the magnitude of protection ranging from -49 to 86%^2–11. While these divergent outcomes are thought to be due primarily to product adherence¹², biological factors likely contribute¹³. Despite selective recruitment of higher risk participants for prevention trials, HIV risk is heterogeneous, even within higher risk groups^14–16. To determine whether this heterogeneity could influence PrEP outcomes, we undertook a post-hoc prospective analysis of the CAPRISA 004 tenofovir 1% gel trial (n=774), one of the first trials to demonstrate protection against HIV infection. Concentrations of nine pro-inflammatory cytokines were measured in cervicovaginal lavages at >2,000 visits, and a graduated cytokine score was used to define genital inflammation. In women without genital inflammation, tenofovir was 57% protective against HIV (95% CI: 7 to 80%), compared to 3% (95% CI: −104 to 54%) if genital inflammation was present. Among high gel adherers, tenofovir protection was 75% (95% CI: 25 to 92%) in women without inflammation compared to −10% (95% CI: −184 to 57%) in women with inflammation. Host immune predictors of HIV risk may modify the effectiveness of HIV prevention tools; reducing genital inflammation in women may augment HIV prevention efforts.