Wednesday morning featured a series of oral presentations exploring the interplay of STIs and altered microbiomes might affect PrEP.
Renee Heffron presented research that explored whether bacterial vaginitis decreased the effectiveness of oral PrEP.
In the CAPRISA 004 study which demonstrated the effectiveness of intravaginal tenofovir it was observed that in women that had a vaginal biome consistent with BV there was a significantly decreased effectiveness of vaginal tenofovir gel. It is postulated that anaeobic bacteria may hasten the breakdown of tenofovir. This study explored data from the PARTNERS PrEP study . It compared baseline vaginal swabs , graded using the nugent scale as to the number of BV related bacteria, with serum tenofovir levels and HIV seroconversion. Reassuringly BV did not seem to affect either Serum levels or PrEP effectInness.
John-Michel Molina presented an interesting IPERGAY sub study. This looked at the controversial area of STI prevention using Doxycycline PEP. Men enrolled in IPERGAY were randomised to be provided with doxycycline PEP or not provided with PEP. Those asked to take the doxycycline PEP were asked to take a stat dose of 200mg between 1 and 3 days after sex. The time to acquisition of an STI (gonorrhoea , chlamydia or syphilis) was compared. In brief , no effect on gono but significantly reduced rates of syphilis and chlamydia. The data presented didn't address the thorny issue of antibiotic resistance. They are still looking at that.