PrEP Failure Case Underscores Importance of Regular HIV Testing

A case of HIV transmission in a person who was adherent to pre-exposure prophylaxis (PrEP) was one of the most discussed studies at CROI 2017. We've seen two previous cases of PrEP failure where HIV was able to transmit because of drug resistance. This was the first case of PrEP failure that did not involve drug resistance, making it unclear why or how transmission happened. Terri Wilder, M.S.W., spoke with Elske Hoornenborg, M.D., the lead author of the study, at CROI 2017, in Seattle.

You can also read our study recap for more details on the case, or see the study abstract and poster.

Terri Wilder: Please start by telling us what happened.

Elske Hoornenborg, M.D.: A person was enrolled in our PrEP Project. He was using daily PrEP and reported excellent adherence. And then, he was HIV negative all the way; he got a few rectal infections that we treated. But after eight months of PrEP use, he got symptoms of a urinary tract infection. We tested him for HIV, and we found that he was antibody positive.

However, he was antigen negative. HIV viral load was negative at that point. We tried to establish a diagnosis, so we tested for proviral DNA in his PBMCs [peripheral blood mononuclear cells] and in sigmoid biopsies. But there was no viral DNA that we could find.

Because there was no diagnosis of HIV infection, we decided to stop his PrEP and try to establish a diagnosis. Three weeks later, his viral load became positive. So, there was indeed an HIV infection. We started him on therapy.

TW: Can you talk a bit more about his adherence to the medication?

EH: We checked adherence in three different ways: self-reported, pill counts, and dried blood spots. We collected the dried blood spots at month six and month eight. Month eight was the moment of seroconversion. And they showed very high intracellular levels of tenofovir diphosphate [Viread], comparable with very good, excellent adherence.

TW: Can you maybe describe in more detail how you were able to detect the HIV in this person?

EH: Yeah. It was really hard to establish a diagnosis because there was no HIV viral load at the point of seroconversion. There was no antigen. So, that really put us in a dilemma how to go forward.

We also did Western blot testing at the moment of seroconversion, which showed only one single gp160 band, which is very atypical for an acute HIV infection.

TW: He had some history of reoccurring sexually transmitted infections [STIs].

EH: Yes.

TW: Do we think this history may have anything to do with this?

EH: This was a guy who was on PrEP. He was very well aware of his risks. He had several partners; he reported, like, 50 partners per month. Most were condomless. Most were receptive. And, yes, he did acquire a few rectal STIs, which is not surprising if you look at his sexual behavior.

TW: What do you think this case report really means for the general scientific community about PrEP efficacy?

EH: I'm a very strong believer in the efficacy of PrEP. If you see worldwide the many thousands of people who are taking PrEP, who are happy to have a fulfilling sex life without fear of HIV, I think PrEP is an immensely important discovery.

Now, we have one breakthrough infection with a wild-type virus. This case had no resistance mutations, and that made it different. That's different from the other two cases that were reported previously. But it's only one case, compared with the several thousands, tens of thousands, of people who use PrEP. I think we have to conclude and communicate to our people that PrEP is very effective -- if you take it well.

It also underscores the importance of having your HIV tests done every three months while you take PrEP. It underscores, yeah, that we should educate people about use of condoms in addition to PrEP, not only for HIV, but also to protect them from STIs.

TW: In terms of his care right now?

EH: After establishing a diagnosis, we started him on combination antiretroviral therapy. He had an undetectable viral load after one month, and he's doing very well.

TW: Great. Thank you so much.

EH: You're welcome.

This transcript has been lightly edited for clarity.

Terri L. Wilder, M.S.W., is a director of HIV/AIDS education and training in New York City.