Molecular and Biochemical Parasitology, 30 (1988) 27-34 27 Elsevier MBP 00992 Multiple Trypanosoma cruzi antigens containing tandemly repeated amino acid sequence motifs Carlos F. Ibafiez 1, Jose L. Affranchino 1, Roberto A. Macina 1, Maria B. Reyes 1, Susana Leguizamon 1, Mario E. Camargo 2, Lena *slund 3, Ulf Pettersson 3 and Alberto C.C. Frasch 1 Xlnstituto de Investigaciones Bioquimicas Fundacion Campomar, Buenos Aires, Argentina; 21nstituto de Medicina Tropical de Sao Paulo, Faculdade de Medicina de Universidade de Sao Paulo, Sao Paulo, Brazil; and 3Department of Medical Genetics, Biomedical Center, Uppsala, Sweden (Received 15 December 1987; accepted 1 March 1988) Chromosomal DNA from Trypanosoma cruzi, the agent of the American trypanosomiasis (Chagas' disease), was used for con- struction of a DNA library, employing the expression vector lambda gt11. Nine clones encoding different parasite antigens were isolated from this library by screening with an antiserum from a Chagasic patient. Nucleotide sequence analysis showed that seven out of the nine isolated clones code for antigens which contain tandemly repeated amino acid sequence motifs. Each of the seven antigens contains a unique repeat, ranging in length between 5 and 68 amino acids. The length of the repeats is highly conserved within each clone. Fusion proteins, expressed from two of the clones, reacted with a large proportion of sera collected from Cha- gasic patients in Argentina, Brazil and Chile. These clones appear thus to encode antigens which are shared between different strains of T. cruzi. Immunofluorescence experiments with live parasites showed that three of the antigens were detectable on the surface of trypanosomes. Key words: Trypanosoma cruzi; Antigen; Tandem repeat; Lambda gt11 Introduction Studies of cloned antigens from plasmodia have shown that many of them have an internal re- peated structure which is the target of the im- mune response [1-5]. Tandem repeats in malaria proteins may moreover generate a 'smokescreen' that prevents the production of effective antibod- ies against critical epitopes. Trypanosoma cruzi, the agent of the American trypanosomiasis (Cha- gas' disease), exists in two main stages in the hu- man host. The trypomastigotes are present in blood and are consequently exposed to the host immune system. Trypomastigotes are capable of invading cells, giving rise to amastigotes which Correspondence address: Dr. Ulf Pettersson, Department of Medical Genetics, Biomedical Center, Box 589, S-75123 Uppsala, Sweden. Abbreviation: H2, human Chagasic serum. replicate intracellularly. T. cruzi parasites must thus carry on their surface molecules that allow interactions with host cells [6,7]. These surface molecules seem to elicit an immune response, protecting against subsequent infection [8]. So far very few studies have been reported on the struc- ture of T. cruzi antigens. Recently, the genes for two proteins with a similar overall structure were described in Trypanosoma brucei [9] and in T. cruzi [10]. However, the T. brucei protein does not seem to play a role in cellular invasion or in the interaction with the immune system as it is expressed only in the insect/vector stage of the parasite [9]. The T. cruzi protein has a molecular mass of 85 kDa and contains tandemly repeated amino acid sequence motifs [10]. An internal T. cruzi antigen which is homologous to a heat-shock protein has also been described [11]. In a previous paper we described the isolation of a collection of clones encoding T. cruzi anti- 0166-6851/88/$03.50 © 1988 Elsevier Science Publishers B.V. (Biomedical Division)