Genetic variability of the 18 kDa/HP6 protective antigen in Taenia saginata and Taenia asiatica: Implications for vaccine development

Genomic characterization of the genes encoding the Taenia 18 kDa/HP6 protective antigens was carried out for Taenia saginata and T. asiatica using 42 taeniid isolates comprising 23 samples of T. saginata, 13 samples of T. asiatica and 6 samples of T. solium. The corresponding sequences from all taeniid isolates were PCR-amplified with specific primers and then sequenced. All the genes, and other described taeniid gene homologues, had the same genomic structure. Surprisingly, the T. saginata TSA18 gene showed nucleotide variability within the 23 samples analyzed. This resulted in two distinct genotypes with 96% DNA sequence similarity and deduced amino acid sequences with 21 substitutions, mainly located in the second exon which contains the fibronectin type III domain. In regards to T. asiatica, the 18 kDa gene (TASI18) was very similar to the T. saginata antigen homologues, both at the DNA and deduced amino acid sequence levels, and the TSOL18 gene was conserved among T. solium isolates as previously described. The implications of these findings on the future development of taeniid vaccines are discussed.

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► The 18 kDa/HP6 protective gene from 42 taeniid isolates (Taenia saginata (N = 23), T. asiatica (N = 13), T. solium (N = 6)), and other described taeniid gene homologues shared the same genomic structure.
► The T. saginata TSA18 genomic gene showed nucleotide variability within the 23 samples analyzed, with two distinct genotypes with 96% DNA sequence similarity and deduced amino acid sequences with 21 substitutions.
► The T. asiatica TASI18 genomic gene showed the same nucleotide sequence in all parasite isolates analyzed.
► The T. asiatica TASI18 gene was very similar to the T. saginata antigen homologues, both at the DNA and deduced amino acid sequence levels.
► The use of the effective T. saginata TSA18 recombinant antigen as a vaccine against infection of T. asiatica in pigs or cattle would be justified.