Background:
Autophagy, a cytosolic-structure degradation pathway producing energy, allows efficient anti-HIV T-cell responses. Autophagy enables IL21 production in anti-HIV CD4 T-cells, which in turn stimulates lipophagy and enhances CD8 T-cell anti-HIV responses. Extracellular Acyl-CoA-Binding Protein (ACBP) inhibits autophagy, tricarboxyclic acid (TCA) cycle and oxidative phosphorylation in mouse models. Herein, we assessed the levels of circulating ACBP and its influence on T-cell function in people living with HIV (PLWH) on antiretroviral therapy (ART).
Methods:
Plasma ACBP and cytokines were quantified by ELISA in 50 PLWH on effective ART (mean duration 14.7 years) and 30 controls with similar age. Metabolomic analyses were performed on serum samples by GC-MS (10 participants with high and low ACBP). In vitro, recombinant ACBP (recACBP) was added at increasing concentration up to 10µg/mL on PBMCs from PLWH on ART and controls, T-cell responses were assessed by flow cytometry. Intracellular LC3B was visualized by microscopy.
Results:
ACBP levels were higher in PLWH on ART compared to controls (median 127.5 vs 78.1 ng/mL, p=0.03), independently of age and sex. In ART-treated PLWH, plasma ACBP levels were neither associated with CD4 nor CD8 T-cell counts, however they correlated with levels of growth factors (EGF, G-CSF, GRO), pro-inflammatory cytokines (IFNα2, IFNγ, IL1β) and homeostatic factors (IL7 and IL15) (r>0.3, p<0.05 for all comparisons). Conversely, ACBP levels were inversely associated with plasma IL21 levels (r=-0.54, p<0.01). PLWH with high ACBP had higher serum levels of TCA intermediates glutamate (2-fold, p=0.02) and α-ketoglutarate (1.5-fold, p=0.09), respectively. We added recACBP to PBMCs stimulated with either anti-CD3 antibodies or HIV Gag, Nef and Env peptides for 16 h, and observed a decrease in IFNγ, IL2 and TNFα production in CD4 and CD8 T-cells (p<0.03 for all). Upon anti-CD3 stimulation, IL17A and IL21 production were also decreased in CD4 T-cells while IL10 levels remained unaffected. RecACBP decreased intracellular levels of the autophagy marker LC3B without affecting cell viability.
Conclusions:
Higher plasma ACBP levels in PLWH on ART were associated with inflammation, unfit metabolism, and markers of T-cell dysfunction. Our findings indicate that circulating ACBP directly abates autophagy and anti-HIV T-cell functions, compelling the development of circulating ACBP inhibitors aiming at improving anti-HIV T-cell responses in PLWH, towards an HIV cure.