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Journal of Clinical Microbiology, Dec 1995, 3239-3244, Vol 33, No. 12
M Varma, DL Rudolph, M Knuchel, WM Switzer, KG Hadlock, M Velligan, L Chan, SK Foung and RB Lal
Immunoassays based on the highly immunogenic transmembrane protein of human
T-cell lymphotropic virus type 1 (HTLV-1) (protein 21c) are capable of
detecting antibodies in all individuals infected with HTLV-1 and HTLV-2.
However, because of antigenic mimicry with other cellular and viral
proteins, such assays also have a large proportion of false- positive
reactions. We have recently identified an immunodominant epitope,
designated GD21-I located within amino acids 361 to 404 of the
transmembrane protein, that appears to eliminate such false positivity.
This recombinant GD21-I protein was used in conjunction with additional
recombinant HTLV type-specific proteins and a whole virus lysate to develop
a modified Western blot (immunoblot) assay (HTLV WB 2.4). The sensitivity
and specificity of this assay were evaluated with 352 specimens whose
infection status was determined by PCR assay for the presence or absence of
HTLV-1/2 proviral sequences. All HTLV-1-positive (n = 102) and
HTLV-2-positive (n = 107) specimens reacted with GD21-1 in the HTLV WB 2.4
assay, yielding a test sensitivity of 100%. Furthermore, all specimens
derived from individuals infected with different viral subtypes of HTLV-1
(Cosmopolitan, Japanese, and Melanesian) and HTLV-2 (IIa0, a3, a4, IIb1,
b4, and b5) reacted with GD21-I in the HTLV WB 2.4 assay. More importantly,
HTLV WB 2.4 analysis of 81 PCR-negative specimens, all of which reacted to
recombinant protein 21e in the presence or absence of p24 and p19
reactivity in the standard WB assay, showed that only two specimens
retained reactivity to GD21-I, yielding an improved test specificity for
the transmembrane protein of 97.5%. None of 41 specimens with gag
reactivity only or 21 HTLV-negative specimens demonstrated reactivity to
GD21-I. In an analysis of additional specimens (n = 169) from different
geographic areas for which PCR results were not available, a substantial
increase in the specificity of GD21-I detection was demonstrated, with no
effect on the sensitivity of GD21-I detection among specimens from
seropositive donors. Thus, the highly sensitive, GD21-I-based HTLV WB 2.4
assay eliminates the majority of false-positive transmembrane results,
thereby increasing the specificity for serologic confirmation of HTLV-1 and
HTLV-2 infections.
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Enhanced specificity of truncated transmembrane protein for serologic confirmation of human T-cell lymphotropic virus type 1 (HTLV-1) and HTLV-2 infections by western blot (immunoblot) assay containing recombinant envelope glycoproteins
Department of Pathology, Stanford University, California 94305, USA.
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