HIV-1 diagnosis during pre-exposure prophylaxis: A case report

We report a case of HIV diagnosis in a 36-year-old man who has sex with men receiving daily oral PrEP (emtricitabine/tenofovir) in Argentina, where viral load or HIV PCR testing is not routinely available before or during prophylaxis. In 2022, PrEP was initiated after a diagnosis of primary syphilis, with a non-reactive fourth-generation HIV test performed 13 days earlier (outside the recommended window), so very early infection already present at initiation cannot be excluded. Self-reported adherence was >95%. Serology was negative at day 23 and became reactive at day 73, with an indeterminate Western blot (gp120 only), undetectable plasma HIV-RNA and preserved lymphocyte counts; dolutegravir was added to complete antiretroviral treatment. Standard diagnostic algorithms were initially inconclusive, and confirmation required approaches beyond routine practice: HIV-1 RNA was detected only after ultracentrifugation of 14 mL of plasma (55 copies), and low-level proviral HIV-1 DNA was identified after analysis of an extensive number of cells; Nef- and p24-specific T-cell responses were also detected. No resistance-associated mutations were found on proviral DNA (integrase region). The Western blot eventually became positive at day 382, while a rapid immunochromatographic assay remained negative at 34 months. Atypical presentations of this kind have been reported under oral TDF/FTC PrEP and were subsequently characterized as long-acting early viral inhibition (LEVI) syndrome, predominantly in the context of long-acting cabotegravir. The present case illustrates the extent of non-routine investigation required to confirm HIV acquisition, and the challenges this poses in settings where oral PrEP is the only available option and HIV-1 RNA PCR cannot be routinely deployed. PrEP should be initiated promptly following a negative HIV test performed on the same day, or as close as possible to PrEP initiation, particularly when recent exposure is possible. HIV testing should be repeated sequentially after initiation, and discordant results should prompt continued serological and molecular evaluation.