Background: Early antiretroviral therapy (ART) during primary HIV-1 infection (PHI) is now recommended to improve clinical outcome and prevent sexual transmission. Early ART may also impact HIV-specific serological response due to the rapid control of viral replication. Our aim was to assess the sensitivity of different HIV screening tests after a prolonged successful ART among patients treated during PHI.
Methods: Among HIV-infected patients enrolled at time of PHI in the ANRS PRIMO cohort, we selected those who received immediate ART and presented an undetectable viral load for ≥36 months afterwards. Frozen serum samples were tested using the CE-certified self-test Autotest VIH® (self-test), two point-of-care immunoassays (INSTI® HIV-1/HIV-2 Rapid Antibody Test [INSTI] and VIKIA® HIV1/2 [VIKIA]), and the 4th-generation ARCHITECT® HIV Ag/Ab Combo immunoassay (4thG ELISA).
Results: Patients (N=44) were mostly male (82%), median age was 40 years. At diagnosis, median CD4 cell count, plasma HIV-RNA and cell-associated HIV-DNA were 372/mm3, 5.3 log10 copies/ml and 3.6 log10 copies/106 PBMC, respectively. ART was initiated at a median of 43 days (range 20-115) after estimated date of infection, corresponding to Fiebig stage II (5%), III (2%), IV (36%), V (21%) or VI (36%). HIV-specific serological response was evaluated after a median of 84 months (range 36-204) of successful treatment. Non-reactivity was found to be 30% for self-test, 9% for INSTI test and 7% for VIKIA test. All participants remained positive with 4thG ELISA (median index=48 [range:1.9-491]) but 7/44 had an index value < 10. We did not find any baseline- or on-treatment immunogical or virological factor associated with non-reactivity of self-test, except the 4thG ELISA index measured at the same time which was weaker for patients with non-reactive self-test (index: 23 vs 60, p=0.003). Cell associated HIV-DNA level at time of self-test was not associated with non-reactivity; of note it remained detectable for 9 of 13 patients (69%) with negative self-test.
Conclusions: The HIV-specific antibody response is stopped and declines when ART is initiated during PHI. Several years of successful ART may lead to seronegativity of HIV self-test in 30% of patients. Particular caution should be given in case of HIV self-retesting.

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