Effective interferon (IFN)-λ treatment regimen to control lethal MERS-CoV infection in mice

Dijkman, Ronald; Selvaraj, Muneeswaran; Gad, Hans Hendrik; Hartmann, Rune; More, Sunil; Perlman, Stanley; Thiel, Volker; Channappanavar, Rudragouda

Effective broad-spectrum antivirals are critical to prevent and control emerging human coronavirus (hCoV) infections. Despite considerable progress made towards identifying and evaluating several synthetic broad-spectrum antivirals against hCoV infections, a narrow therapeutic window has limited their success. Enhancing the endogenous interferon (IFN) and interferon-stimulated gene (ISG) response is another antiviral strategy known for decades. However, the side effects of pegylated type-I IFNs (IFN-Is) and the pro-inflammatory response detected after delayed IFN-I therapy have discouraged their clinical use. In contrast to IFN-Is, IFN-λ, a dominant IFN at the epithelial surface, is shown to be less pro-inflammatory. Consequently, we evaluated the prophylactic and therapeutic efficacy of IFN-λ in hCoV infected airway epithelial cells and mice. Human primary airway epithelial cells treated with a single dose of IFN-I (IFN-α) and IFN-λ showed similar ISG expression, whereas cells treated with two doses of IFN-λ expressed elevated levels of ISG compared to IFN-a treated cells. Similarly, mice treated with two dose IFN-λ were better protected compared to mice receiving a single dose, and a combination of prophylactic and delayed therapeutic regimens completely protected mice from lethal MERS-CoV-infection. A two dose IFN-λ regimen significantly reduced lung viral RNA and inflammatory cytokine levels with marked improvement in lung inflammation. Collectively, we identify an ideal regimen for IFN-λ use and demonstrate the protective efficacy of IFN-λ in MERS-CoV infected mice.