HIV Transmission Despite Adherence to PrEP and No Drug Resistance
A man in Amsterdam contracted HIV despite reporting excellent adherence to daily oral pre-exposure prophylaxis (PrEP) using tenofovir/emtricitabine (TDF/FTC, Truvada), according to a study presented at CROI 2017 in Seattle.
This is the third reported case of PrEP failure despite reportedly good adherence; however, this is the first case involving HIV without any drug resistance. The first case and second case involved transmission of drug-resistant HIV.
The case study, which was presented by Elske Hoornenborg, M.D., leader of the Amsterdam PrEP Project, followed a 50-year-old MSM (man who has sex with men) who became HIV positive eight months after starting PrEP. The patient tested negative for HIV at the start of PrEP, and at one month, three months and six months.
The patient reported an average of about 50 anal sex partners per month before diagnosis. He also reported having condomless anal sex on about 50% of the days before diagnosis. The median number of sex partners per day with condomless anal sex ranged between two to five each month.
Additionally, during his time on PrEP, the patient experienced two instances of rectal gonorrhea and one instance of rectal Chlamydia. He also reported using drugs during sex, including amphetamine, cocaine, mephedrone and ketamine.
Dried blood spots were collected at month six and month eight, both of which showed adequate levels of tenofovir, suggesting good adherence to PrEP.
During month eight after starting PrEP, the patient presented with symptoms of fever and urinary tract infection. He was then tested for HIV and tested positive for HIV antibodies, but negative for HIV antigen and HIV RNA. Additionally, no HIV DNA was detected in the patient's peripheral blood mononuclear cells (PBMCs).
PrEP was then interrupted and HIV RNA became detectable after three weeks. Resistance testing showed that the patient's virus had no mutations against TDF, FTC or any other antiretroviral agent. He was subsequently started on boosted darunavir (Prezista) with dolutegravir (Tivicay) and TDF/FTC and achieved an undetectable viral load after one month.
"The presence of an aberrant immune response under appropriate serum TDF levels raises the possibility that a very high HIV exposure, possibly in combination with inadequate TDF levels in gut mucosa may have led to infection," the researchers hypothesize. However, it remains unknown why and how the patient seroconverted.
"This underscores the importance of regular HIV testing in PrEP users and being aware of potential atypical patterns of seroconversion," the study authors conclude.