Exosomes are microvesicles originating from many cell types including immune cells. Prior studies suggest exosomes play a role in HIV pathogenesis and some comorbidities. The relationship of exosome cargo in peripheral blood to HIV infection, immune responses and comorbidities has potential applications for biomarker discovery and new treatment strategies. Here, we perform a cross-sectional study to characterize protein cargo of circulating exosomes in HIV patients and its relationship to virological and immunological markers.
Plasma exosomes were isolated from 53 subjs (n=30 HIV+ from NNTC, age 38-54, 66% male, 53% black, on ART with suppressed viral load [VL<1500 copies] & n=23 HIV- controls matched for age, gender, race). Exosome quality was assessed by dynamic light scattering, transmission electron microscopy & immunoblotting (WB) for exosome markers (HSP70, CD9, CD63, CD81). Proteomic analysis was by LC/MS/MS. Following bioinformatic analysis of hits, proteins were confirmed by WB
Circulating exosomes were increased in HIV+ subjects compared to controls based on WB for exosomal HSP70 & CD9 (p<0.01). HSP70, CD9 & CD63 were also detected in exosomes released by PBMCs treated with hemin (24 hrs). Exosomal HSP70 & CD9 levels correlated with plasma VL & kynurenine:tryptophan ratio (K:T ratio, a marker of immune activation) in HIV+ subjects (p<0.01). CD81+ exosome numbers (by ELISA) & exosome-associated NOTCH4 (by WB), but not HSP70 & CD9 levels, were higher in HIV+ subjects using cocaine compared to non-users, despite similar VL & K:T ratios (p<0.05). LC/MS/MS proteomics suggested plasma exosomes were mainly derived from myeloid cells (CD33, CD11A, CD11B, CSF1R) & revealed proteins related to exosomes (EXOSC10, BST2, SYNE1, VPS), immune activation/inflammation (CD69, CRP, TNFRSF10, CSF1R, chemokines), Wnt signaling (E-Cadh, DDR1, LRP5, NOTCH4), & metabolism (ADIPOQ); many of these were also detected in exosomes released by heme-treated PBMC. Treatment of THP-1 cells with HIV+ patient-derived exosomes induced modest increases in CXCL10 & other IFN-induced genes, indicating pro-inflammatory effects.
This study demonstrates associations between exosome proteins & disease markers in HIV patients on ART. Circulating exosomes in HIV+ individuals on ART are mainly derived from myeloid cells, carry protein cargo related to immune responses, inflammation, Wnt signaling and may have pro-inflammatory effects during pathogenesis.