| Summary: | <p>Abstract</p> <p>A previously described <it>Taenia saginata </it>HDP2 DNA sequence, a 4-kb polymorphic fragment, was previously used as the basis for developing PCR diagnostic protocols for the species-specific discrimination of <it>T. saginata </it>from <it>T. solium </it>and for the differentiation of <it>T. saginata </it>from <it>T. asiatica</it>. The latter was shown subsequently to lack the required specificity, so we undertook genetic studies of the HDP2 sequence from <it>T. saginata </it>and <it>T. asiatica </it>to determine why, and to develop a novel HDP2-PCR protocol for the simultaneous unambiguous identification of human taeniids. Sequencing and further analysis of the HDP2 DNA fragments of 19 Asiatic isolates of <it>T. saginata </it>and <it>T. asiatica </it>indicated that the HDP2 sequences of both species exhibited clear genomic variability, due to polymorphic variable fragments, that could correspond to the non-transcribed region of ribosomal DNA. This newly observed polymorphism allowed us to develop a novel, reproducible and reliable HDP2-PCR protocol which permitted the simultaneous discrimination of all <it>T. saginata </it>and <it>T. asiatica </it>isolates examined. This species-specific identification was based on, and facilitated by, the clear size difference in amplicon profiles generated: fragments of 1300 bp, 600 bp and 300 bp were produced for <it>T. asiatica</it>, amplicons of 1300 bp and 300 bp being obtained for <it>T. saginata</it>. Control <it>T. solium </it>samples produced one amplicon of 600 bp with the HDP2-PCR protocol. The assay has the potential to prove useful as a diagnostic tool in areas such as South East Asia where <it>T. saginata</it>, <it>T. asiatica </it>and <it>T. solium </it>coexist.</p>
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