Molecular characteristics of an immobilization antigen gene of the fish-parasitic protozoan Ichthyophthirius multifiliis strain ARS-6

Academic Article


  • Ichthyophthirius multifiliis (Ich), a ciliated protozoan parasite of fish, expresses surface antigens (i-antigens), which react with host antibodies that render them immobile. The nucleotide sequence of an i-antigen gene of I. multifiliis strain ARS-6 was deduced. The predicted protein of 47 493 Da is comprised of 460 amino acids (aa's) arranged into five imperfect repeats with periodic cysteine residues with the structure: CX(19)20CX 2CX16-27CX2CX20(21)CX3. The N-terminal aa's typify a signal peptide motif while a stretch of C-terminal aa's resemble a glycosyl-phosphatidyl-inositol (GPI)-anchor addition site. The degree of deduced i-antigen aa sequence identity of strain ARS-6 (GenBank accession no ACH87654 and no ACH95659) with other I. multifiliis i-antigen sequences present in GenBank ranges from 99% to 36% identity with 52 kDa i-antigens of I. multifiliis strain G5 (accession nos AAK94941 and AAK01661 respectively). Immunoblot analysis of i-antigens following exposure of I. multifiliis theronts to catfish anti-I. multifiliis immune serum did not show any appreciable alteration in i-antigen expression. The mechanism that regulates i-antigen expression in I. multifiliis remains a puzzling question. © 2009 Blackwell Munksgaard. No claim to original US government works.
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    Author List

  • Xu DH; Panangala VS; Van Santen VL; Dybvig K; Abernathy JW; Klesius PH; Liu Z; Russo R
  • Start Page

  • 1884
  • End Page

  • 1892
  • Volume

  • 40
  • Issue

  • 16