Characterization of Sm20.8, a member of a family of schistosome tegumental antigens

Magdy M. Mohamed, Kamal A. Shalaby, Philip T. LoVerde, Amr M. Karim

Research output: Contribution to journalArticlepeer-review

66 Scopus citations


Two cDNA clones each encoding a 20.8-kDa protein (Sm20.8) were identified from the human blood fluke Schistosoma mansoni sporocyst and adult worm cDNA expression libraries by antibodies derived from rabbits vaccinated with irradiated cercariae and purified over an NP-40 extract of 3h schistosomula. Each identified cDNA has an open reading frame encoding a protein of 181 amino acids and shows homology (29-30%) with Sm21.7, Sm22.6, and Sj22.6, previously identified as belonging to a family of soluble schistosome tegumental antigens. An EF-hand calcium-binding motif is found in Sm20.8 protein in two different positions. However, neither motif binds 45calcium (45Ca) Recombinant Sm20.8 showed immunoreactivity with sera from infected humans and rabbits vaccinated with irradiated cercariae. Polyclonal rabbit sera against the Sm20.8 recognized the native protein in an extract of infected snail (sporocyst), cercariae, 3 hour schistosomules (3 h NP-40) and an adult worm preparation but not in uninfected snail tissue or eggs. Further demonstration that Sm20.8 was expressed in the different developmental stages of the parasite was by RT-PCR. Confocal microscopy demonstrates that Sm20.8 localizes to the tegument of adult worms and 3 h np-40. The IgG fraction specific to Sm20.8 mediated complement killing of schistosomules in vitro by 34%. Vaccination of mice with naked DNA containing the Sm20.8 gene and subsequently challenged with cercariae showed 30% reduction in worm burden compared to controls. Copyright (C) 1998 Elsevier Science B.V.

Original languageEnglish (US)
Pages (from-to)15-25
Number of pages11
JournalMolecular and Biochemical Parasitology
Issue number1-2
StatePublished - Oct 30 1998
Externally publishedYes


  • EF hand Ca binding domain
  • Schistosoma mansoni
  • Sm20.8
  • Tegumental antigen

ASJC Scopus subject areas

  • Molecular Biology
  • Parasitology


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