Expression and Purification of a Novel Computationally Designed Antigen for Simultaneously Detection of HTLV-1 and HBV Antibodies.

Computational tools are reliable alternatives to laborious work in chimeric protein design. In this study, a chimeric antigen was designed using computational techniques for simultaneous detection of anti-HTLV-I and anti-HBV in infected sera. Databases were searched for amino acid sequences of HBV/HLV-I diagnostic antigens. The immunodominant fragments were selected based on propensity scales. The diagnostic antigen was designed using these fragments. Secondary and tertiary structures were predicted and the B-cell epitopes were mapped on the surface of built model. The synthetic DNA coding antigen was sub-cloned into pGS21a expression vector. SDS-PAGE analysis showed that glutathione fused antigen was highly expressed in E. coli BL21 (DE3) cells. The recombinant antigen was purified by nickel affinity chromatography. ELISA results showed that soluble antigen could specifically react with the HTLV-I and HBV infected sera. This specific antigen could be used as suitable agent for antibody-antigen based screening tests and can help clinicians in order to perform quick and precise screening of the HBV and HTLV-I infections.

Crystallization of a trimeric human T cell leukemia virus type 1 gp21 ectodomain fragment as a chimera with maltose-binding protein.

We present a novel protein crystallization strategy, applied to the crystallization of human T cell leukemia virus type 1 (HTLV-1) transmembrane protein gp21 lacking the fusion peptide and the transmembrane domain, as a chimera with the Escherichia coli maltose binding protein (MBP). Crystals could not be obtained with a MBP/gp21 fusion protein in which fusion partners were separated by a flexible linker, but were obtained after connecting the MBP C-terminal alpha-helix to the predicted N-terminal alpha-helical sequence of gp21 via three alanine residues. The gp21 sequences conferred a trimeric structure to the soluble fusion proteins as assessed by sedimentation equilibrium and X-ray diffraction, consistent with the trimeric structures of other retroviral transmembrane proteins. The envelope protein precursor, gp62, is likewise trimeric when expressed in mammalian cells. Our results suggest that MBP may have a general application for the crystallization of proteins containing N-terminal alpha-helical sequences.

Influence of amino acid substitutions on antigenicity of immunodominant regions of the HTLV type I envelope surface gylcoprotein: a study using monoclonal antibodies raised against relevant peptides.

By the use of sera of human T cell leukemia virus type I (HTVL-I)-infected individuals it was shown that amino acid substitutions at positions 192 (proline to serine) and 250 (serine to proline) in major immunodominant regions (175-199 and 239-261) of the surface envelope glycoprotein (gp46) of the virus may influence the humoral response. Since human sera are polyclonal in nature, one cannot readily discriminate between an immunoglobulin-specific recognition and multiple bindings of diverse antibodies. To overcome this difficulty we generated murine monoclonal antibodies to synthetic peptides mimicking all or portions of these gp46 regions. The reactivity of some of these antibodies to synthetic peptides harboring (or not harboring) the preceding amino acid substitutions at position 192 or 250, to denatured gp46 by Western blotting, and to live (variously substituted) HTLV-I-infected cells, combined with blocking experiments with various peptides, allow us to conclude that the major epitopes (positions 183-191, 190-197, 190-199, and 246-252) in the two immunodominant regions may elicit different antibody responses according to their sequences. It is worth noting that in a reporter gene inhibition assay, it was found that a neutralizing monoclonal antibody (MF1), the epitope for which is located between residues 190 and 197, had a high level of activity when cells (2060) harboring a gp46 with proline at position 192 were used and had no activity toward cells (1010) with a serine at this position. Therefore our results establish that certain amino acid substitutions of gp46 may drastically affect the antigenicity of the molecule and the biological activity of the antibodies elicited.

Novel complications with HTLV-1-associated myelopathy/tropical spastic paraparesis: interstitial cystitis and persistent prostatitis.

Lower urinary symptoms associated with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) are common, but have been regarded as 'neurogenic' due to spinal involvements. However, in some cases, these symptoms are persistent, progressive, and not directly correlated with the severity of other neurologic symptoms of the lower spinal cord. These findings prompted us to locate organic lesions in the lower urinary tract and to correlate them with HTLV-1 infection. Among 35 HAM patients with lower urinary symptoms, we found 4 cases with the symptoms persistent and progressive: 3 with contracted bladder and another with persistent prostatitis. Histological or cytological examinations indicated local lymphocytic infiltrations in the lower urinary tract in all cases: 3 by the infiltration in the bladder and the other by a high concentration of lymphocytes in expressed prostatic secretions. Of 3 cases whose urinary samples were available, 2 showed significant increase in the concentration of urinary anti-HTLV-1 antibody of IgA class. The urinary IgA antibody of the third case was not elevated, but the sample had been obtained after resection of the affected bladder. None of the control cases showed significant anti-HTLV-1 IgA antibody in urine except for a case of gross hematuria due to chemotherapy directed against adult T-cell leukemia. We suggest inclusion of these processes into the spectrum of complications for HAM/TSP. The elevated excretion of anti-HTLV-1 of IgA class in urine may be an indicator of these complications.