The major 85-kD surface antigen of the mammalian form of Trypanosoma cruzi is encoded by a large heterogeneous family of simultaneously expressed genes.

Abstract

SummaryTrypanosoma cruzi is an obligate intracellular protozoan parasite. The parasite mammalian stage surface antigens exhibit extensive antigenic diversity. We have characterized a family of T. cruzi genes that code for a polymorphic set of85-kD surface antigens, the SA85-1 antigens. The family contains >100 genes and pseudogenes, of which a minimum of nine are transcribed. The gene family is expressed in the mammalian stage only. A subset of the gene family is present in two Teomere-linked copies in the genome . Telomere linkage of other expressed SA85-1 genes has not been demonstrated. We have shown that at least three members of the SA85-1 gene family encode antigens at the surface of the mammalian stage of the parasite. Interestingly, these three antigens are expressed on all the trypanosomes examined. This suggests that T. cmzi simultaneously expresses a large repertoire of similar, but diverse antigens at its surface. Thus, T. cruzi exhibits extensive antigenic diversity in a system unique from that ofAfrican trypanosomes, perhaps reflecting its intracellular niche. rypanosoma cmzi, an obligate intracellular protozoan para-

Expression and evolution of members of the Trypanosoma cruzi trypomastigote surface antigen multigene family

“…An internal location is not strictly correlated with the absolute level of transcription, since the single member in the Silvio strain is internal and transcripts of this member are detected in Northern blots of A + RNA [16]. Likewise, studies on related members of the multigene family demonstrated that genes from telomeric and internal locations can be expressed simultaneously [24]. However, within the TSA family it is clear that when both internal and telomeric genes are present in the same genome, transcripts from internal member(s) are much less abundant than transcripts from telomeric member(s).…”

Nucleotide sequence and transcription of a trypomastigote surface antigen gene of Trypanosoma cruzi

“…This observation suggests that not all members of the gene family are being co-expressed and that those members which areexpressed might be located at telomeric sites. In contrast, another study has shown that several members of an 85-kDa gene family, both telomeric and non-telomeric, are being expressed simultaneously in both amastigotes and trypomastigotes [ 10]. Since the pattern of expression of these 2 gene families seems quite different, the question arises as to whether they represent two distinctly different 85-kDagene families.…”

“…Although an 85-kDa trypomastigote surface glycoprotein has not yet been purified and characterized, genes which encode portions of trypomastigote specific 85-kDa surface antigens have been identified and partially characterized [7][8][9][10]. Examination of the genomic organization and RNA transcription products of these genes show them to share certain common features.…”

Isolation and characterization of the TSA/trans-sialidase family gene from the Silvio strain of Trypanosoma cruzi

“…The major surface glycoproteins of the bloodstream trypomastigote stage of Trypanosoma cruzi are encoded by a large multigene family [1][2][3][4][5][6][7][8][9][10], several members of which are expressed simultaneously and encode glycoproteins of 85-160 kDa. We have previously isolated, characterized, and obtained the complete nucleotide sequence of TSA-1, a surface antigen gene from the Peru strain of T. cruzi belonging to the 85-kDa multigene family [1,2,5].…”

“…The COOH terminus of the coding region represents one of the two regions conserved in all 85-kDa multigene family members characterized to date [2][3][4][5][6][7][8] and is the proposed processing site for a phosphatidylinositol linkage [12]. The other conserved region found in all family members examined is a 12-aa region which lies immediately upsteam of the repeat array in TSA-S1 [4,10]. Interestingly, the predicted signal sequence at the amino terminus of TSA-1 shows only 35% identity with the predicted amino terminus of TSA-S1 (Fig.…”