Lectins in innate host defence against influenza virus

Soluble collagenous C-type lectins (collectins) present in plasma and lung fluids display antiviral activity against influenza virus in vitro. Our studies in the mouse model of influenza indicate that the collectin lung surfactant protein D (SP-D) plays an important role in vivo in innate defence of the respiratory tract against the virus. Furthermore, studies with diabetic mice indicated a direct link between their increased susceptibility to influenza virus infection and interference with collectin-mediated host defence of the lung by glucose. Macrophages are another important component of innate immunity to influenza virus, uptake of the virus leading to nonproductive viral replication and secretion or proinflammatory cytokines and type 1 interferons (FFN-alpha/beta), Our recent studies on infection of murine macrophages by influenza virus indicate that uptake is mediated by the macrophage mannose receptor, an integral membrane C-type lectin with carbohydrate specificity similar to that of the collectins. The oligosaccharide present on influenza viral glycoproteins thus appears to act as a target for recognition of the virus by endogenous lectins of the innate immune system. Evasion of such recognition by poorly glycosylated viruses may contribute to their virulence. (C) 2001 Elsevier Science B.V. All rights reserved.