Antiviral Lectins of the Plant Family Amaryllidaceae

Abstract

AbstractPlants have long served as a first line of defence against viral-borne diseases. Their chemical constituents have also afforded a sound basis for antiviral drug discovery. The plant family Amaryllidaceae is distinguished for its isoquinoline alkaloids, some of which have proved to be interesting antiviral drug leads. Its lectin (or agglutinin) principles have likewise attracted considerable attention as potential antiviral drugs. This review focuses on the antiviral activities that have been described for the lectins of the Amaryllidaceae. Of the thirty lectins known in the family, fourteen have been screened against nearly seventy pathogens belonging to thirteen viral families. Whilst good activities were reported in most cases, the lectins from Galanthus nivalis, Narcissus pseudonarcissus and Hippeastrum hybrid were identified with the best overall activities. They displayed potent inhibitory effects against the human immunodeficiency virus HIV-1(IIIB) proliferation in CEM lymphoblastic cells (EC50s 0.005, 0.009 and 0.004 μM, respectively). Although significant effort was dedicated to the Retroviridae, noteworthy effects were also observed against members of other viral families (such as hepatitis C virus of the Flaviviridae). Furthermore, the lectins were shown to be highly selective antiviral agents, devoid of significant toxicities towards the nearly forty cells employed as hosts. Almost all of the details of their modes of operation have emerged from studies carried out on HIV. They were shown to inhibit viral attachment, fusion and adsorption to a variety of host cells. Modulation of viral entry was shown to occur via interference with the virus envelope glycoprotein. These observations fit into the key biological characteristic of lectins, that of sugar-binding proteins. Graphical Abstract