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Molecular characteristics of an immobilization antigen gene of the fish‐parasitic protozoan Ichthyophthirius multifiliis strain ARS‐6
Author(s) -
Xu DeHai,
Panangala Victor S,
Van Santen Vicky L,
Dybvig Kevin,
Abernathy Jason W,
Klesius Phillip H,
Liu Zhanjiang,
Russo Riccardo
Publication year - 2009
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/j.1365-2109.2009.02301.x
Subject(s) - ichthyophthirius multifiliis , biology , antigen , catfish , genbank , microbiology and biotechnology , gene , genetics , fish <actinopterygii> , fishery
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)20 CX 2 CX 16−27 CX 2 CX 20(21) CX 3 . 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 # ACH87654 and # 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 #s 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.