Absolute quantification of HTLV-1 basic leucine zipper factor (HBZ) protein and its plasma antibody in HTLV-1 infected individuals with different clinical status.

Yasuo Shiohama,Yuetsu Tanaka,Tadasuke Naito,Hiroshi Takashima,Toshio Matsuzaki,Takeaki Tomoyose,Takuya Fukushima,Mineki Saito,Reiko Tanaka

doi:10.1186/s12977-016-0263-z

Abstract

BackgroundHuman T cell leukemia virus type 1 (HTLV-1) basic leucine zipper factor (HBZ), which is encoded by a minus strand mRNA, is thought to play important roles in the development of adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). However, a comprehensive analysis of HBZ, including mRNA and protein expression, humoral immunoreactivity against HBZ, and HTLV-1 proviral load (PVL), in HTLV-1-infected individuals with different clinical status has not been reported previously.ResultsIn this study, using novel monoclonal antibody-based in-house enzyme-linked immunosorbent assay systems, we report the absolute quantification of HBZ protein and its plasma antibody in clinical samples from HTLV-1-infected individuals with different clinical status. The data were compared to both HBZ mRNA levels and PVL. The results showed that plasma anti-HBZ antibody was detectable only in 10.4 % (5/48) of asymptomatic carriers (ACs), 10.8 % (13/120) of HAM/TSP patients, and 16.7 % (7/42) of ATL patients. HBZ protein was detected in three out of five patients with acute ATL, but was not detected in patients with HAM/TSP (0/10) or ACs (0/4). Thus, an antibody response to HBZ was not associated with the PVL or the expression of HBZ (both at the mRNA and protein levels) or the clinical status of the infection.ConclusionsThe present results emphasize the extremely low expression and immunogenicity of HBZ in natural HTLV-1 infection. However, there is a possibility that the low but distinct expression of HBZ protein in PBMCs is associated with the survival of HTLV-1-infected cells and the development of ATL.Electronic supplementary materialThe online version of this article (doi:10.1186/s12977-016-0263-z) contains supplementary material, which is available to authorized users.

Highlights

Human T cell leukemia virus type 1 (HTLV-1) basic leucine zipper factor (HBZ), which is encoded by a minus strand mRNA, is thought to play important roles in the development of adult T-cell leukemia (ATL) and HTLV1-associated myelopathy/tropical spastic paraparesis (HAM/HTLV-1-associated myelopathy/tropical spastic paraparesis (TSP))
Antibody reactivity and specificity were confirmed by the detection of HTLV-1 bZIP factor (HBZ) protein in the cell extracts of 293T cells transfected with the HBZ expression plasmid pCMVHA-HBZ, but not in extracts from mock-transfected cells
293T cells transfected with the HBZ expression plasmid were stained with the anti-HBZ monoclonal antibodies (mAbs), whereas mock-transfected cells were not. These results confirm the specificity of our mAbs against HBZ protein, and demonstrate that they can be used for intracellular flow cytometric analysis

Summary

Introduction

Human T cell leukemia virus type 1 (HTLV-1) basic leucine zipper factor (HBZ), which is encoded by a minus strand mRNA, is thought to play important roles in the development of adult T-cell leukemia (ATL) and HTLV1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The predicted binding affinity of HLA to HBZ peptides was significantly weaker than that to the Tax peptides, and the detection frequency of HBZ-specific CTLs in HTLV-1-infected individuals was significantly lower than that of Tax-specific CTLs [14] These observations suggest that efficient control of viral replication is associated with CTL recognition of poorly immunogenic HBZ protein, but not the immunodominant Tax protein [13], and that a strong immune response to HBZ is associated with a low PVL, which reduces the risk of both HAM/ TSP [15] and ATL [16]

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Results

Discussion

Conclusion