The effect of antibody against ganglioside antigen on Trypanosoma brucei parasites was examined in vitro and ill Vivo Using antiGanalioside GM1 (AGIM-1) monoclonal antibody. The antibody showed complement-dependent cytotoxicity against T brucei with mouse complement. Furthermore. mice given AGM-1 were challenged intraperitoneally with T brucei. Although all non-treated control mice died within six days after infection, all of AGM-1-injected mice had survived by six days post-infection. These data suggest that antibody against ganglioside antigen on T brucei has potential in protection against T brucei infection. (c) 2004 Elsevier Ltd. All rights reserved.