Interferon-λ in immunocompetent individuals with a history of recurrent herpes labialis

Background: Herpes labialis (HL) is the most common manifestation of recurrent oral herpes simplex virus type-1 (HSV-1) infection. Between 20% and 40% of the population is affected by recurrent HL. The biological basis for the difference between HSV-1-infected individuals who do and who do not suffer recurrences, has long been investigated. Interferon (IFN)-α and IFN-λ are essential for antiviral immunity, but the precise role of IFN-λ in vivo is not yet well understood. Methods: Healthy immunocompetent patients with or without a history of recurrent HL were recruited from the Policlinico of the University of Rome Tor Vergata (Rome, Italy), and HSV-1-seronegative individuals were recruited from the Department of Experimental Medicine of the University of Rome Tor Vergata, between July 2007 and December 2008. Participants were interviewed by medically trained investigators and underwent a blood test. Peripheral blood mononuclear cells (PBMCs) were obtained from heparinized blood of patients and stimulated in vitro with intact HSV-1 strain F1 (1 plaque-forming unit/cell). PBMC supernatants were assayed for IFN-α, IFN-γ and IFN-λ production by ELISA at 24 and 48 h after viral challenge. Results: PBMC from patients with a history of recurrent HL produced markedly lower levels of IFN-λ and marginally lower levels of IFN-α and IFN-γ than those from the history-negative HSV-1-seropositive controls. Among individuals with HL recurrences, those with more frequent and severe manifestations showed a significant trend towards lower levels of IFN-λ production. Conclusions: A reduced IFN-λ response might correlate with the development of recurrent HSV-1 infection in immunocompetent individuals. Testing for IFN-λ response might be useful to predict individual patterns of antiviral response, contributing to more successful therapeutic or prophylactic interventions.