So far there have been two well documented cases of individuals on PrEP contracting HIV despite good adherence and high TDF levels. This poster presents a case where a 50 year old gentleman, who had optimal TDF levels (on 2 dried blood spot examinations) - 8 months in to the AMPrEP study he tested antibody reactive, antigen negative on a 4th generation Ab/Ag HIV test. During this visit he described symptoms of fever and dysuria. Western blot reveleaved a single band at gp160. At the time the patient had tested negative on pol PCR (DNA and RNA) of bulk PBMCs and sigmoid colon biopsy, and had no detectable HIV viral load. PrEP was subsequently stopped due to concerns around inducing resistance (looks like this was done within a few days of the results - see attached poster). 3 weeks later, HIV RNA was detected in plasma (40,000 copies/ml). No resistance mutations were identified. The patient was commenced on treatment and 1 month later had an undetectable viral load.
The presenter highlights this as being a probable third case of HIV seroconversion in a PrEP-adherent individual. This would be a first case of wild-type virus being transmitted under these conditions. They postulate possible reasons for PrEP failure such as very high exposures, and repeated trauma.
What’s not clear to me is whether the possibility of a false reactive HIV Ab/Ag was considered. The poster does not detail the reactivity score (i.e. was this a borderline result) on the LIAISON XL platform. If this result was a borderline reactive, was this more of a PEP failure, i.e. the patient did not have a long enough PrEP-tail following last UPAI, or was this indeed a PrEP failure? Did they stop the PrEP too soon? This brings us to question how we go about managing indeterminate HIV results in the the context of PrEP.
What do you think?