Herpes simplex virus-1 (HSV-1) infection induces a potent but ineffective IFN-λ production in immune cells of AD and PD patients

Background The sequential activation of immediate early (IE), early (E) and late (L) genes is required to allow productive herpes simplex virus type 1 (HSV-1) infection. Several evidences suggest that, together with inflammation, an immunological response incapable to counteract HSV-1 reactivation plays a role in the pathogenesis of Alzheimer’s (AD) and Parkinson’s (PD) diseases. IFN-lambda (IFN-λ), a cytokine endowed with a robust antiviral activity, contains HSV-1 reactivation. HSV-1-induced IFN-λ, IL-10 and IL-1β as well as the expression of viral IE, E and L genes were analyzed in vitro in peripheral blood mononuclear cells (PBMC) of AD and PD patients as well as of healthy controls (HC). Methods PBMC of AD, PD and HC were in vitro infected with one multiplicity of infection (1 MOI) HSV-1. IE, E, and L viral genes transcription as well as IFN-λ, IL-10 and IL-1β production were analyzed. Results In HSV-1-infected cells of AD and PD patients compared to HC: (1) transcription of IE (ICP0, ICP27) genes was reduced whereas that of E (UL41, UL29) and L (UL48, LAT) genes was increased; (2) IFN-λ mRNA expression was increased. IL-1β was augmented and IL-10 was reduced in unstimulated cells of AD and PD compared to HC; HSV-1 infection significantly increased IL-10 production in HC alone. Conclusions Data herein show that a proinflammatory condition is present in AD and PD, in whom attempts to obstacle viral replication via an initial, possibly more potent IFN-λ-mediated control of IE viral genes is unsuccessful.