IS THIS HIV SEROCONVERSION? AN UNUSUAL CASE OF REACTIVE HIV TESTS WITH GOOD PREP ADHERENCE

Introduction

HIV seroconversion in PrEP users is unusual; with breakthrough infection in the context of good adherence even rarer¹. PrEP exposure can also cloud the interpretation of reactive tests and real-time decisions to stop, continue or intensify PrEP become tricky. We describe a case of reactive HIV results in this context.

Methods

An MSM attends a UK GUM clinic requesting continuation of daily oral PrEP (TDF/FTC)-which started nine months ago in the USA. They report good adherence with history of unprotected anal intercourse. Initial 4th generation HIV antibody is reported as ‘low level reactive ’. The case is reported to UKHSA and the patient recalled.

Results

The reference lab also reports indeterminate HIV status, p24 antigen test-negative. Urgent HIV RNA viral load is negative. Decision is taken to continue PrEP pending further investigations. The patient recalls taking part in a HIV vaccine trial 10 years previous. The research team is contacted, confirming that participants will experience Vaccine Induced Seropositivity (VISP). Follow up sample indicates no progression of the Western blot, which remains indeterminate, Pro-viral DNA result is negative and the patient is determined to be HIV negative, with reactive tests due to VISP and the patient continues PrEP.

Discussion

VISP is a phenomenon which occurs in individuals who have received an HIV vaccine, the vaccine induces the formation of HIV antibodies which will cause participants to ‘screen positive’ on routine HIV testing. To monitor these individuals taking PrEP, HIV differentiation assays (such as western blot) and pro-viral DNA are required to exclude HIV infection.

References

Ambrosioni J, Petit E, Liegeon G, Laguno M, Miro J. Primary HIV-1 infection in users of pre-exposure prophylaxis. Lancet HIV 2021; 8:e166–e174.