Expression of the gag gene of human T-cell leukemia virus type I in Escherichia coli and its diagnostic use

Analysis of human lymphotropic T-cell virus type II-like particle production by recombinant baculovirus-infected insect cells

The molecular processes involved in retrovirus assembly and budding formation remain poorly understood. The gag-pro-pol genes of human lymphotropic T-cell virus type II (HTLV-II) are translated into Gag, Gag-Pro, or Gag-Pro-Pol by frameshift events. In the present study, we investigated the roles of the gag, pro, and pol regions of HTLV-II in viral particle formation using recombinant baculoviruses. In this study we could successfully produce mature HTLV-II viral particles containing core structures using a construct expressing the entire gag-pro-pol region. We also investigated the role of the pol region in particle formation. Deletion of the pol region affects viral particle assembly or release very little, indicating that the gag-pro region is sufficient for viral particle formation and maturation. Expression of the Gag proteins alone or Gag proteins with inactivated viral proteases (Pro) resulted in the formation of viral particles; however, these particles did not contain core structures. These results suggest the intracellular expression of Gag with Pro of HTLV-II is essential for the production of mature virus particles, whereas that of Pol is not.

The presence of antibodies to purified p24gag protein of HTLV-I in sera of patients with systemic lupus erythematosus (SLE)

Sera of patients with systemic lupus erythematosus (SLE) were tested for their reactivity to HTLV-I by western blotting (WB). Seven (18%) of 40 SLE serum samples reacted to the p24gag protein of HTLV-I by WB using purified gag antigens. The specificity of anti-p24gag antibodies in the SLE sera was confirmed by competitive inhibition on WB. Two of the seven patients were shown to be HTLV-I carriers, because HTLV-I infected T cell lines were easily established from their peripheral blood mononuclear cells (PBMC). Except for these two carrier patients, the gag proteins were not detected in the lysates of PBMC by WB using anti-p24gag and anti-p19gag monoclonal antibodies. The gag and pX genes of HTLV-I were not detected by PCR in PBMC of the SLE patients, with the exception of the 2 HTLV-I carrier patients. These results show no direct involvement of HTLV-I in the etiology of SLE. However, the existence of a specific antibody to p24gag in the sera of some of the noncarrier SLE patients suggests a crossreactivity to either unknown viruses or some autoantigens.

Myristoylation-dependent membrane targeting and release of the HTLV-I Gag precursor, Pr53gag, in yeast

The unprocessed HTLV-I Gag precursor, Pr53gag, was synthesized in yeast, Saccharomyces cerevisiae. The synthesized Pr53gag was myristoylated, associated with the cellular membrane, and released into the culture medium. The released Pr53gag was pelleted by centrifugation at 100,000 x g for 2 h. Conversion of Gly2 to Ala allowed synthesis of a non-myristoylated soluble Pr53gag which was not released into the culture medium. These results suggest that the release of the HTLV-I Gag precursors Pr53gag, occurs in yeast in a myristoylation-dependent manner.

Development and evaluation of a human T-cell leukemia virus type I serologic confirmatory assay incorporating a recombinant envelope polypeptide

A recombinant protein derived from the gp21 region of the human T-cell leukemia virus type I (HTLV-I) env gene was synthesized in Escherichia coli and purified by reversed-phase high-performance liquid chromatography. The purified protein was free of contaminating bacterial proteins and retained reactivity with human HTLV-I- and HTLV-II-positive sera and a gp21 monoclonal antibody. An immunoblot procedure using the recombinant polypeptide in conjunction with native viral proteins was more sensitive than the conventional immunoblot and radioimmunoprecipitation confirmatory assays for detection of antibodies to HTLV-I and HTLV-II env-encoded gene products. The recombinant protein was equally reactive with sera from polymerase chain reaction-confirmed HTLV-I or HTLV-II infections. Furthermore, on the basis of the differential reactivities of gp21-positive sera with the HTLV-I p19 and p24 gag-encoded proteins, an algorithm was proposed to distinguish exposure to HTLV-I from exposure to HTLV-II. These results establish the utility of a modified immunoblot assay incorporating a recombinant envelope polypeptide as an alternative to existing HTLV-I-confirmatory assays.

Low-titer antibodies reactive with HTLV-I gag p19 in patients with chronic myeloneuropathy

To elucidate the possible association of human T-lymphotropic virus type I (HTLV-I) and chronic neurological diseases, 156 serum samples from patients with various neurological diseases, including multiple sclerosis, chronic progressive myelopathy, chronic inflammatory polyradiculoneuropathy, myasthenia gravis, polymyositis, motor neuron disease, and tension headache, and healthy control subjects were examined for IgG antibodies to HTLV-I by three independent techniques--gelatin particle agglutination test, enzyme-linked immunosorbent assay, and Western blot assay. Specificity of antibodies was assessed by homologous competitive inhibition on Western blot assay. Six patients (3 with chronic progressive myelopathy, 1 with chronic inflammatory polyradiculoneuropathy, 1 with motor neuron disease, and 1 with tension headache) had high-titer HTLV-I antibodies. Twelve patients (5 with multiple sclerosis, 1 with chronic progressive myelopathy, 2 with chronic inflammatory polyradiculoneuropathy, 2 with myasthenia gravis, and 2 with motor neuron disease) had low-titer HTLV-I antibodies that reacted with a single gag protein, p19 or p24, on Western blot assay. In 4 (2 with multiple sclerosis, 1 with chronic progressive myelopathy, and 1 with chronic inflammatory polyradiculoneuropathy) of these 12, the antibodies that were all directed to p19 were determined to be specific by homologous competitive inhibition. In the remaining 8 patients (3 with multiple sclerosis, 1 with chronic inflammatory polyradiculoneuropathy, 2 with myasthenia gravis, and 2 with motor neuron disease), restricted reactions against p19 or p24 were considered to be nonspecific because they were not inhibited by homologous competitive inhibition. The results suggest that in some patients chronic myeloneuropathy diagnosed as chronic progressive multiple sclerosis, chronic progressive myelopathy, and chronic inflammatory polyradiculoneuropathy may be associated with HTLV-I or related retroviruses.

A gag-env hybrid protein of human T-cell leukemia virus type I and its application to serum diagnosis

A fused gene of the gag and env sequences of human T-cell leukemia virus type I (HTLV-I), the causative agent of adult T-cell leukemia, was constructed in vitro and expressed in Escherichia coli. The gag-env hybrid protein accumulated as insoluble granules with a yield of approximately 12% of the total proteins. In an enzyme-linked immunosorbent assay done with the use of the gag-env hybrid protein, all 57 seropositive sera gave positive signals, and none of the sera from normal persons did. This system can produce large quantities of the gag-env hybrid protein, which can be used for mass screening of human sera for HTLV-I infection.

Synthesis of proteins in Escherichia coli immunoreactive with sera from individuals infected with human T-cell leukemia virus type I

The env-pX IV fused gene of human T-cell leukemia virus type I (HTLV-I) was inserted into lac promoter-directed expression vectors for production of viral proteins in bacteria. Resulting recombinant plasmids, pK13 and pK15, directed synthesis of fused proteins of 59 kDa (Env-p40x) and 100 kDa (Gag-Env-p40x), respectively. Western blot analysis showed that these proteins were reactive with sera of patients with adult T-cell leukemia (ATL) and retained multiple antigenic determinants of viral proteins. In combination with recombinant Gag protein [S. Itamura, K. Shigesada, M. Imai, N. Kobayashi, T. Hamakado, T. Harada and M. Hatanaka, Gene 38, 57-64 (1985)], these bacterially synthesized proteins may provide a useful tool for differential diagnosis of ATL by detecting serum antibodies against individual viral proteins and for analysis of viral gene functions.

Construction of a new plasmid vector that can express cloned cDNA in all translational reading frames

Construction of a bacterial expression vector, pSI4001, is described. The vector contains the lac promoter-operator and three sets of ribosome-binding sites (RBSs) tandemly arranged in all possible reading frames. cDNA can be directly cloned downstream from these translational start points in the fixed and proper orientation by using the method of Okayama and Berg [Mol. Cell. Biol. 3 (1982) 280-289]. The open reading frame of any cDNA inserted may be automatically aligned in phase with either of the three ATG start codons, thus enabling its expression with a maximum theoretical probability of unity. Fusion with the lacZ gene (coding for beta-galactosidase) has shown that at least two of the three translation initiation sites exhibit high expression capacities and the remaining one can also function at a lower but significant rate. We used the vector to construct a bovine pituitary cDNA library, from which clones coding for prolactin were detected by immunological screening with an efficiency as high as two in three clones. The construction with triple RBSs should also provide a unique experimental model to study the regulation of overlapping translations.