Comparison of tsa417-like variant-specific surface protein (VSP) genes in Giardia intestinalis and identification of a novel locus in genetic Group II isolates.
Date
1998
Authors
Ey, P.
Darby, J.
Mayrhofer, G.
Editors
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
Journal article
Citation
Parasitology (Cambridge), 1998; 117(5):445-455
Statement of Responsibility
Conference Name
Abstract
<jats:p>A gene (<jats:italic>vsp417</jats:italic>-3<jats:sup>A-II</jats:sup>) encoding a new member
of the variant-specific surface protein (VSP) family of <jats:italic>Giardia</jats:italic>
is
described. <jats:italic>Vsp417</jats:italic>-3<jats:sup>A-II</jats:sup> is detected exclusively in
isolates belonging to the genetic Assemblage A/Group II sublineage
of
<jats:italic>G. intestinalis</jats:italic>, and it is closely related to a previously characterized
VSP gene (<jats:italic>tsp11</jats:italic>, herein renamed <jats:italic>vsp417</jats:italic>-2<jats:sup>A-I</jats:sup>)
found
in Group I isolates of <jats:italic>G. intestinalis</jats:italic>. Analysis of DNA amplified
from the genomes of Group II isolates using consensus
primers also revealed products corresponding to the <jats:italic>vsp417</jats:italic>-2 locus
(<jats:italic>vsp417</jats:italic>-2<jats:sup>A-II</jats:sup> allele), indicating that <jats:italic>vsp417</jats:italic>-2<jats:sup>A-II</jats:sup>
and <jats:italic>vsp417</jats:italic>-3<jats:sup>A-II</jats:sup> represent separate loci in these organisms.
Southern hybridizations revealed a single genomic copy of
<jats:italic>vsp417</jats:italic>-3<jats:sup>A-II</jats:sup> in Group II isolates, but efforts to detect
this locus in Group I organisms were unsuccessful. Together with
the <jats:italic>vsp417</jats:italic>-1 (<jats:italic>tsa417</jats:italic>) locus that was first identified
in the genetic Group I isolate WB and which has been detected since
in all tested genetic Group I isolates (as <jats:italic>vsp417</jats:italic>-1<jats:sup>A-I</jats:sup>)
and in genetic Group II isolates (as <jats:italic>vsp417</jats:italic>-1<jats:sup>A-II</jats:sup>),
<jats:italic>vsp417</jats:italic>-3<jats:sup>A-II</jats:sup> represents a third member of a stable
subset of <jats:italic>tsa417</jats:italic>-like VSP genes in genetic Group II <jats:italic>G. intestinalis</jats:italic>.
The encoded
polypeptide, <jats:italic>vsp417</jats:italic>-3<jats:sup>A-II</jats:sup> (667 residues, predicted
<jats:italic>M</jats:italic><jats:sub>r</jats:sub> 69120) possesses a high cysteine content (12·1
mol%), 28 copies
of the metal-binding -CXXC- motif, and a highly conserved C-terminal hydrophobic
domain – similar to all other
characterized <jats:italic>Giardia</jats:italic> VSP. A revised nomenclature for <jats:italic>Giardia</jats:italic>
VSP genes is proposed, prompted by the need to describe
the homologues found in the various major genotypes of the species complex,
<jats:italic>G. intestinalis</jats:italic>.</jats:p>