A presentation at the recent 25th Conference on Retroviruses and Opportunistic Infections (CROI 2018) describes what
appears to be another case of infection with HIV in someone consistently taking pre-exposure prophylaxis (PrEP). However, a lack of monitoring and a
failure to give the subject an HIV test around the time he experienced what may have
been HIV seroconversion symptoms means that it is difficult to be 100% certain
that this is a case of PrEP failure.
Two cases were presented in 2016 of people who were infected
with drug-resistant virus despite taking PrEP, one
in Toronto and one
in New York. A
third case from Amsterdam in 2017 did not involve drug-resistant HIV.
In this case, because of lack of monitoring, it is impossible
to say whether the patient caught HIV that was already resistant to the PrEP
drugs tenofovir and emtricitabine, or whether resistance developed as a result
of his staying on PrEP for a month after suspected symptoms of acute HIV infection were
seen.
The case features the first time that analysis of tenofovir levels
in hair have been used to establish retrospectively that the person infected
had been consistently taking PrEP over the time he is thought to have been
infected.
The case involved a
34-year-old gay man from North Carolina and was presented by Joshua Thaden of
the University of North Carolina, which has long hosted a key HIV clinic and
research centre – it was one of the first clinics in the world to offer
protease inhibitors in the 1990s.
The patient concerned had a negative HIV test in December
2015, and started taking PrEP in February 2016. He insists that he had no
sexual contacts between those two dates. After three months, in May 2016, he
decided to stop taking PrEP as he said he didn’t think he was at risk, but
resumed against two months later in July 2016.
This is all taken from the patient’s retrospective account of his
PrEP history. Although he was told he should attend at the end of his first and
third month of PrEP for HIV testing and monitoring, he was given not just one
month’s prescription but one month with eleven refill notes – so essentially a year’s
worth of PrEP at once. He was not contacted when he failed to turn up for his
monitoring appointments. So until January 2017, which is as far back as direct
measurements of PrEP in his hair can go, we only have the patient’s assurance
that he took PrEP regularly every day from July 2016 onwards.
The patient stayed on PrEP until April 2017. In March
2017 he came down with symptoms suggestive of HIV seroconversion illness – namely
fever and muscle ache. However, HIV seroconversion
symptoms are notoriously unspecific. The patient was given a test for influenza
A and B at this point, but it is impossible to rule out that his symptoms could
have been due to another viral infection. If he had been tested for HIV at this
point, acute HIV infection might have been detected.
He did test HIV positive when he came back for a test
in April 2017 – having spent at least another month on PrEP with HIV infection. At this point his viral load was 27,000 copies/ml –
typical of a ‘steady state’ infection rather than acute HIV, when viral load is
usually higher.
He was also tested for PrEP drug levels, which were found to
be adequate, and for HIV drug resistance. He turned out to have K65R and M184V,
the two signature resistance mutations against tenofovir and emtricitabine. He
also had K103N, which is the most common resistance mutation to the first-generation
non-nucleoside reverse transcriptase inhibitors (NNRTI) drugs efavirenz and nevirapine.
He was put on an initial antiretroviral therapy regimen
of rilpivirine, dolutegravir and boosted darunavir and quickly became virally
suppressed, with the darunavir being withdrawn from his treatment in July 2017.
Because the patient had gone unmonitored for so long, it was
decided to analyse tenofovir levels in his hair. These showed that he had tenofovir
levels consistent with seven-day-a-week dosing between 15 January 2017 and 15 April,
when he stopped PrEP. But measurements cannot go back beyond that,
The researchers think that the most likely scenario is that he
was infected with a virus with at least the K103N NNRTI mutation in March 2017.
But were the signature PrEP resistance mutations also in the virus he acquired,
or did they develop as a result of him staying on PrEP for a month – or more, if he actually caught HIV earlier – while
HIV positive?
On the one hand, infection with HIV with both K65R and M184V
is very rare, as confirmed by another presentation from Seattle at this conference (see this article), but
these mutations can develop relatively easily if someone stays on PrEP while
HIV positive. The researchers therefore think this is the most likely scenario.
But if his virus only had K103N when he was infected, this brings up the troubling possibility that this is the second case of PrEP breakthrough
by HIV that has no prior resistance to PrEP. We will probably never know,
because the chance to catch his infection in the process of it happening was
missed in this case.