The roles of direct recognition by animal lectins in antiviral immunity and viral pathogenesis

Abstract

Lectins are a group of proteins with carbohydrate recognition activity. Lectins are categorized into many families based on their different cellular locations as well as their specificities for a variety of carbohydrate structures due to the features of their carbohydrate recognition domain (CRD) modules. Many studies have indicated that the direct recognition of particular oligosaccharides on viral components by lectins is important for interactions between hosts and viruses. Herein, we aim to globally review the roles of this recognition by animal lectins in antiviral immune responses and viral pathogenesis. The different classes of mammalian lectins can either recognize carbohydrates to activate host immunity for viral elimination or can exploit those carbohydrates as susceptibility factors to facilitate viral entry, replication or assembly. Additionally, some arthropod C-type lectins were recently identified as key susceptibility factors that directly interact with multiple viruses and then facilitate infection. Summarization of the pleiotropic roles of direct viral recognition by animal lectins will benefit our understanding of host-virus interactions and could provide insight into the role of lectins in antiviral drug and vaccine development.

Figure 1

The role of lectins in viral infection. (A) Activate immune response; (B) Inhibit viral entry; (C) Facilitate viral attachment; (D) Benefit viral components maturation; (E) Facilitate viral components trafficking. The lectins involved in each role are listed in the black box.

Figure 2

Sequence alignment of carbohydrate-binding motifs. The core sequences of the carbohydrate-binding region of several C-type lectins were aligned using ClustalW2. The E-P-N and Q-P-D motifs are highlighted in yellow. SP-D: Surfactant protein-D; CTLD: C-type lectin domain; MBL: Mannose-binding lectin; MR: Mannose receptor; SP-A1: Surfactant protein-A1; ASCPR-H1: Asialoglycoprotein receptor H1 subunit; SRCL: Scavenger receptor with CTLD.

Figure 3

Diagram of lectin structures. (A) MBL; (B) SP-A; (C) SP-D; (D) Galectin-1; (E) Galectin-3; (F) DC-SIGN(R): DC-SIGN and DC-SIGNR; (G) Mannose Receptor; (H) CLEC5A; (I) Langerin; (J) CI-MPR; (K) CD-MPR; (L) Calnexin; (M) ERGIC-53.

Figure 4

The roles of intracellular lectins in the cytosolic pathway. (A) Facilitate the maturation of viral proteins; (B) Sort M-6-P modified viral proteins to the endosomal pathway; (C) Benefit the formation of infectious viral particles.