Human Pegivirus (HPgV, formally GB virus C) infects lymphocytes and NK cells in vivo, and infection is associated with reduced T cell and NK cell activation in HIV-infected individuals. The mechanism by which HPgV inhibits NK cell activation has not been assessed. Following IL-12 stimulation, IFNγ expression was lower in HIV-HPgV co-infected subjects compared to HIV mono-infected subjects (p=0.02). In addition, HPgV positive human sera, extracellular vesicles containing E2 protein, recombinant E2 protein and synthetic E2 peptides containing a predicted Tyk2 interacting motif inhibited NK cell IL-12-mediated IFNγ release. E2 protein also inhibited Tyk2 activation following IL-12 stimulation. In contrast, cytolytic NK cell function was not altered by HPgV. Inhibition of NK cell-induced proinflammatory/antiviral cytokines may contribute to both HPgV persistence and reduced immune activation during HIV-coinfection. Understanding mechanisms by which HPgV alters immune activation may contribute towards novel immunomodulatory therapies to treat HIV and inflammatory diseases.
Keywords: GBV-C; HPgV; Immune modulation; NK cells; Tyk2.
Published by Elsevier Inc.