Introduction:
Exosomes, virus-sized vesicles, carry protein cargos resembling those of their parent
cells and modify immune cell functions. Here, we address the query whether exosomes
derived from Human Papilloma Virus-positive (HPV+) or HPV-negative (HPV-) HNC cell
lines differ in molecular and immunoregulatory profiles.
Methods:
Concentrated supernatants of 3 HPV+ (SCC-2, SCC-47, SCC-90) and 2 HPV- (PCI-13, PCI-30)
HNC cell lines were added to Sepharose-based size exclusion chromatography columns.
Exosomes in fraction #4 were assessed for morphology and size by electron microscopy
(TEM) and for protein content by BCA. Protein profiles were determined by Western
blots and mass spectrometry. The impact of exosomes on immune functions were measured
in co-culture assays with human T cells.
Results:
Exosomes from all cell lines were similar in size (30 – 150nm) and protein levels
(2 – 10ug/mL). HPV+ cell line and exosomes carried E6, E7 and p16. Immunomodulating
molecules (TGFß, FasL, HSP70) were equally expressed on all exosomes. Mass spectrometry
and gene ontology analysis revealed that driving energy pathways were twice frequent
in HPV+ exosomes (p < 0.0001), whereas cell growth/maintenance and immune response
were higher expressed in HPV- exosomes. No differences were observed in the ability
of HPV+ vs. HPV- exosomes to induce apoptosis in activated T cells or suppress their
activation and proliferation.
Conclusions:
Exosomes derived from HPV+ HNCs carried viral antigens and had proteomic profiles
that were distinct from that of HPV- exosomes. Immunosuppression mediated by HPV+
and HPV- exosomes were comparable. Exosomes reflect the HPV status of their parent
cells and thus might serve as future plasma biomarkers of HPV infection in HNC.
