Anti-human immunodeficiency virus type 1 (HIV-1) activity of lectins from Narcissus species.

Mannose-specific lectins (MSLs) were isolated from bulbs of fifteen wild Narcissus species growing in Spain and assayed for their HIV-1 infection inhibitory activity in MT-4 cells and compared to the Narcissus pseudonarcissus agglutinin (NPA), the commercially available MSL obtained from daffodils. Almost all the tested MSLs were found to be active, showing EC50 values (microg/mL) similar to that of NPA, with some being comparable to those obtained with dextran sulfate without significant cytotoxicity. However, on a molar basis almost all of the MSLs tested exhibited lower EC50 values than dextran sulfate whilst six MSLs had values lower than AZT. The most efficacious anti-HIV-1 activity was exhibited by the Narcissus tortifolious MSL, which was 10- (microg/mL) and 100- (molarity) fold more potent than dextran sulfate. Significantly, although this MSL was 15-fold less potent than AZT in terms of quantity (microg/mL), it was 68-fold more potent on a molar basis. The antiviral indices, a ratio of the concentrations that produce cytotoxicity and HIV-1 replication, were calculated and three of the MSLs, N. confusus, N. leonensis and N. tortifolius reported 1.5-, 2- and 8.5-fold greater AI values than dextran sulfate or AZT. Comparison of MSL haemagglutination activities (HAA) to their anti-HIV-1 activities showed that there was no significant correlation. It was suggested that this may be due to a dissociation between both activities as a consequence of multiple isolectin composition.