Anti-gp41 antibody levels reflect HIV viral suppression and cellular reservoir in long-term antiretroviral-treated trial participants.

Background: A major challenge to HIV cure strategies is the quantification of persistent reactivation-prone virus in people living with HIV.

Objectives: To determine whether anti-gp41 antibody levels correlate with viral suppression and HIV-1 DNA levels in patients on ART.

Methods: Participants with plasma HIV-1 RNA below 50 copies/mL for >12 months were included from three ANRS cohorts (COPANA, MONOI and APROCO). Antibody levels to gp41 were measured by a low-sensitivity enzyme-linked immunoassay. Correlations with patient and virus characteristics, plasma HIV-1 RNA load (standard and ultrasensitive tests) and cell-associated HIV-1 DNA were assessed.

Results: Median age was 41 years and 77.5% of the 683 participants were men. Median CD4+ T cell count was 582 cells/mm3 and median viral suppression duration was 6.6 years (IQR 2.0-9.5). The overall median anti-gp41 antibody titre was 1.3 (IQR 0.6-1.9); median HIV-1 DNA level was 2.6 (IQR 2.1-3.0) log10 copies/106 leucocytes; and HIV-1 RNA was undetectable in 56% of samples. A lower titre of anti-gp41 antibodies correlated with male gender, longer viral suppression and lower HIV-1 DNA burden. Sustained undetectable HIV-1 RNA was associated with lower anti-gp41 levels [median 1.1 (IQR 0.5-1.6) versus 1.4 (IQR 0.7-1.9), P = 0.009].

Conclusions: Anti-gp41 levels decreased with the duration of antiviral suppression on ART. Lower titres were associated with lower HIV-1 DNA levels and longer duration of viral suppression, reflecting minimal antigen stimulation. Anti-gp41 antibody titration may be a useful biomarker reflecting long-term HIV-1 suppression on ART.