Lectin Switching During Dengue Virus Infection

Dejnirattisai, Wanwisa; Webb, Andrew I.; Chan, Vera; Jumnainsong, Amonrat; Davidson, Andrew; Mongkolsapaya, Juthathip; Screaton, Gavin

L-SIGN contains a tandem repeat in its neck region, Nterminal to the carbohydrate recognition domain, which can be of variable length between 3 and 9 repeats. L-SIGN exists as tetramers, and previous studies have suggested that heterogeneity in the tandem repeat region of the L-SIGN neck region may contribute to severe acute respiratory syndrome (SARS) susceptibility by altering the viral Env-receptor affinity [24] . To determine whether heterogeneous L-SIGN neck lengths affect DENV infection levels, we examined the effects of a single length repeat and compared it with cells expressing 2 different-length L-SIGN alleles simultaneously. We examined this by transient transfection, and 293T cells were used for these assays as they can be transiently transfected to a high level. 293T were transfected with L-SIGN containing 5 or 7 repeats singly or together in equal amounts. L-SIGN expression was confirmed by surface staining and flow cytometry. Equal expression of alternate-length L-SIGN constructs was also confirmed by western blotting. Transfectants were then infected with dengue virus, and infection was monitored by intracellular staining together with an antibody specific to L-SIGN to reveal transfected cells. All transfectants were equally infected with no reduction in cells expressing both L-SIGN alleles, suggesting that heterotetrameric L-SIGN was as effective as homotetrameric L-SIGN at promoting infection ( Figure 5 ).