ABSTRACT Defensins are a family antimicrobial peptides and play an important role in innate immunity. They are produced by leukocytes, macrophages, and epithelial cells. Some are produced constitutively, whereas others are induced by proinflammatory cytokines and infections caused by bacteria, fungi, parasites and viruses. Defensins are small cationic peptides containing six cysteines stabilized by three intramolecular disulfide bonds. Based on their size, structure and position of their disulfide bonds, they are classified in three groups: α, β and θ-defensins. The action mechanism is mainly based on the cationic and amphipathic properties which participate in the formation of pores in the cell membrane of infectious agents. They are also regulators of inflammation, cell proliferation inducers and damage repair. The abnormal expression of defensins has also been associated with human diseases. The effects of defensins on viral infections appear to be specific to the defensin, virus and target cell. The viral elimination is achieved by multiple mechanisms. Because of the ample spectrum of antiviral activity against different viruses and other microorganisms, defensins constitute attractive therapeutic candidates. In this review, we describe the general characteristics of the defensins as well as some action mechanisms in viral infections.
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