Alternative splicing and sequence diversity of transcripts from the oncosphere stage of Taenia solium with homology to the 45W antigen of Taenia ovis.

ABSTRACT

Genes and transcripts which show homology to the host-protective 45W antigen of Taenia ovis have been cloned from the human parasite Taenia solium. The T. solium genes cloned in this study (TSO45) show conserved genomic structural features which are also features of the T. ovis 45W gene family. The TSO45 genes consist of a four exon and three intron structure. Eight TSO45 transcripts, encoded by at least five genes, were cloned from T. solium oncospheres and comparison of their DNA sequence indicates that some transcripts have arisen by alternative splicing, the first demonstration of exon inclusion/exon skipping in cestodes. Alternative splicing occurred with respect to both exons II and III with three splice variants identified from the TSO45-1 gene and two splice variants from TSO45-5. The proteins encoded by this family of genes contain putative N-linked glycosylation sites, an amino terminal secretory signal, a hydrophobic carboxy terminal sequence characteristic of GPI-anchored proteins and fibronectin type III motifs. These features are common to their T. ovis and Taenia saginata homologues. The similarities of the TSO45 genes cloned in this study with genes encoding host-protective antigens of T. ovis and T. saginata indicates that the encoded T. solium proteins are quite possibly antigenic and have potential use as a vaccine to prevent T. solium infection in the parasite's intermediate host. In this respect, the generation of sequence diversity and hence potential antigenic diversity through alternative splicing of TSO45 genes may have implications for the use of these proteins in vaccines against T. solium cysticercosis.