Development of glycosylated human interleukin-1 alpha, neoglyco IL-1 alpha, coupled with D-mannose dimer: synthesis and biological activities in vitro.

Interleukin 1 (IL-1) is a nonglycosylated cytokine with pleiotropic effects on various cell types. In order to investigate the effect of carbohydrate introduction on IL-1 activity and to develop IL-1 with less deleterious effects recombinant human IL-1 alpha was chemically coupled with mannose dimers, alpha-D-Man1-6-D-Man[Man2(alpha 1,6)] and alpha-D-Man1-4-D-Man[Man2(alpha 1,4)]. About 5 molecules of mannose dimers were introduced per molecule of IL-1. Anti-IL-1 alpha antibody reacted only weakly with the glycosylated IL-1s. Conversely, antibody against the mannose dimer reacted with only glycosylated IL-1. The effect of glycosylation on IL-1 activity was evaluated by measuring a variety of IL-1 activities in vitro, including proliferative effect on T cells, antiproliferative effect on melanoma cells, stimulatory effect on IL-6 synthesis by melanoma cells, and stimulatory effect on prostaglandin E2 synthesis by fibroblast cells. Glycosylated IL-1s exhibited reduced activities, which were 10-fold to more than several hundred-fold lower than those of the original IL-1 alpha depending upon different aspects of activities addressed. Man2(alpha 1,6)-introduced IL-1 exhibited lower activity than Man2(alpha 1,4)-introduced IL-1. The competitive binding of 125I-IL-1 alpha to mouse T cells with unlabeled IL-1s suggests that the reduced activity of glycosylated IL-1s is due, at least partially, to the decrease of their receptor binding abilities.