A tubulin-related 55 kilodalton surface antigen recognized by different Trypanosoma cruzi stage-specific monoclonal antibodies from infected mice.

Thirteen monoclonal antibodies (MAbs) specific for the membrane of live Trypanosoma cruzi have been obtained from BALB/c infected mice. Most of them had greater avidity for intact than for disrupted parasites. According to the staining by indirect immunofluorescence of the different live developmental stages of the parasite the MAbs could be divided into several groups. Three of them were trypomastigote specific, one amastigote-specific and two epimastigote-specific. The rest reacted with either all stage forms or with various combinations of the different stages. However, despite the fact that they seemed to correspond to stage-specific antibodies, ten of them reacted with the same 55/50 kDa antigen by immunoblotting. Similarly, a 55 kDa protein was immunoprecipitated from these MAbs. By contrast, a single band or a dimer of about 25 kDa was the predominant antigen(s) immunoprecipitated by the same MAbs in absence of protease inhibitors. This smaller protein may arise from proteolysis of the 55 kDa band. This protein is related to tubulin since tubulin (a 55 kDa protein) but not other cytoskeleton proteins blocked the binding of these MAbs to T. cruzi, and some MAbs react with pig alpha-tubulin by immunoblotting.