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Background: Infection, such as by human immunodeficiency virus (HIV), has been reported to cause atherosclerosis by inducing inflammation. Because human T-cell leukemia virus type 1 (HTLV-1) is a retrovirus, as is HIV, we investigated the possible influence of HTLV-1 on the pathogenesis of atherosclerosis by use of established atherosclerosis parameters. Methods: The study was done on Iki Island, Fukuoka, an area endemic for HTLV-1. The data of 1,424 residents who reported to an annual health check were available for analysis. Anti-HTLV-1 antibody status and factors associated with atherosclerosis were examined, including maximum intima-media thickness (Max-IMT) and brachial-ankle pulse wave velocity (PWV). Results: HTLV-1 positive participants had significantly higher Max-IMT (1.15 ± 0.55 vs. 1.08 ± 0.61 mm, P = 0.04) and PWV (1,760.6 ± 414.5 vs. 1,657.1 ± 425.5 cm/s, P < 0.01) values than did those negative. Moreover, in multiple regression analysis (odds ratio: 1.39, P < 0.01) of participants with Max-IMT 1.1 mm or over, HTLV-1 was extracted as an independent factor for the development of atherosclerosis. Conclusion: Our results indicate that HTLV-1 infection confers a high risk of atherosclerosis, although its opposite relation is also possible. It is important to carefully follow the health status of HTLV-1 carriers. J Clin Med Res. 2021;13(3):164-169 doi: https://doi.org/10.14740/jocmr4457

Background The reliable diagnosis of human T-cell leukemia virus type 1 (HTLV-1) infection is important, particularly as it can be vertically transmitted by breast feeding mothers to their infants. However, current diagnosis in Japan requires a confirmatory western blot (WB) test after screening/primary testing for HTLV-1 antibodies, but this test often gives indeterminate results. Thus, this collaborative study evaluated the reliability of diagnostic assays for HTLV-1 infection, including a WB-based one, along with line immunoassay (LIA) as an alternative to WB for confirmatory testing. Results Using peripheral blood samples from blood donors and pregnant women previously serologically screened and subjected to WB analysis, we analyzed the performances of 10 HTLV-1 antibody assay kits commercially available in Japan. No marked differences in the performances of eight of the screening kits were apparent. However, LIA determined most of the WB-indeterminate samples to be conclusively positive or negative (an 88.0% detection rate). When we also compared the sensitivity to HTLV-1 envelope gp21 with that of other antigens by LIA, the sensitivity to gp21 was the strongest. When we also compared the sensitivity to envelope gp46 by LIA with that of WB, LIA showed stronger sensitivity to gp46 than WB did. These findings indicate that LIA is an alternative confirmatory test to WB analysis without gp21. Therefore, we established a novel diagnostic test algorithm for HTLV-1 infection in Japan, including both the performance of a confirmatory test where LIA replaced WB on primary test-reactive samples and an additional decision based on a standardized nucleic acid detection step (polymerase chain reaction, PCR) on the confirmatory test-indeterminate samples. The final assessment of the clinical usefulness of this algorithm involved performing WB analysis, LIA, and/or PCR in parallel for confirmatory testing of known reactive samples serologically screened at clinical laboratories. Consequently, LIA followed by PCR (LIA/PCR), but neither WB/PCR nor PCR/LIA, was found to be the most reliable diagnostic algorithm. Conclusions Because the above results show that our novel algorithm is clinically useful, we propose that it is recommended for solving the aforementioned WB-associated reliability issues and for providing a more rapid and precise diagnosis of HTLV-1 infection.

The diagnosis of human T -cell leukemia virus type 1 (HTLV-1) infection in Japan is usually performed by serological testing, but the high rate of indeterminate results from western blotting makes it difficult to assess the infection accurately. Nucleic acid tests for HTLV-1 and/or HTLV-2 are used to confirm infection with HTLV-1 and/or HTLV-2 and are also used for the follow-up of HTLV-1 related diseases. To prepare a highly sensitive method that can discern infection with HTLV-1 and HTLV-2, a multiplex quantitative polymerase chain reaction (qPCR) by large-scale primer screening was developed. Sensitivity and specificity were evaluated by serial dilution of cell lines and by testing with known clinical samples. The resulting multiplex qPCR can detect about four copies of HTLV-1 provirus per 105 cells. Moreover, HTLV-1 provirus could be detected in 97.2% (205 of 211) of HTLV-1 seropositive clinical samples. These sensitivities were sufficiently high compared with the methods reported previously. Also, all the HTLV-2 seropositive clinical samples tested were found to be positive by this method (three of three). In conclusion, this method can successfully and simultaneously detect both types of HTLV-1 and HTLV-2 provirus with extremely high sensitivity.

Quantitative PCR (qPCR) of human T-cell leukemia virus type 1 (HTLV-1) provirus is used for HTLV-1 testing and for assessment of risk of HTLV-1-related diseases. In this study, a reference material was developed for standardizing HTLV-1 qPCR. Freeze-dried TL-Om1 cells diluted with Jurkat cells were prepared and an assigned value for proviral load (PVL) of 2.71 copies/100 cells was determined by digital PCR. Nine Japanese laboratories using their own methods evaluated the PVLs of this reference material as 1.08-3.49 copies/100 cells. The maximum difference between laboratories was 3.2-fold. Correcting measured PVLs by using a formula incorporating the assigned value of this reference material should minimize such discrepancies.

Human T-cell leukemia virus type I (HTLV-1) infection is endemic in Japan, particularly clustered in the southwestern district, Kyushu-Okinawa, which consists of eight prefectures that further consist of 274 municipalities. However, no information is available about the fine-scale distribution of HTLV-1 infection within Kyushu-Okinawa. To assess the municipal-level distribution of people with HTLV-1 infection in Kyushu-Okinawa, we performed a cross-sectional study using a fine-scale geographic information system map based on HTLV-1 screening test results from the Japanese Red Cross database from September 2012 to February 2014. Of the 881 871 (646 914 male, 234 957 female) screened blood donors, 981 were seropositive for HTLV-1 by confirmatory test. The seroprevalence was 0.11% (95% confidence interval [CI] 0.10%-0.12%) for all, 0.094% (95% CI, 0.09%-0.10%) for male, and 0.16% (95% CI, 0.14%-0.18%) for female individuals. The sex- and age-specific HTLV-1 seroprevalence varied significantly across municipalities; particularly, the seroprevalence among women aged 50 years was significantly higher than that of men in both the mainland of Kyushu-Okinawa and the satellite island, in all of which the seroprevalence of HTLV-1 was more than 1.2%. These results show that, even in the Kyushu-Okinawa district, there are endemic clusters of HTLV-1 in small areas. This suggests that public health education programs are needed to eliminate new HTLV-1 infection in these areas.

Western blotting (WB) for human T cell leukemia virus type 1 (HTLV-1) is performed to confirm anti-HTLV-1 antibodies detected at the initial screening of blood donors and in pregnant women. However, the frequent occurrence of indeterminate results is a problem with this test. We therefore assessed the cause of indeterminate WB results by analyzing HTLV-1 provirus genomic sequences. A quantitative PCR assay measuring HTLV-1 provirus in WB-indeterminate samples revealed that the median proviral load was approximately 100-fold lower than that of WB-positive samples (0.01 versus 0.71 copy/100 cells). Phylogenic analysis of the complete HTLV-1 genomes of WB-indeterminate samples did not identify any specific phylogenetic groups. When we analyzed the nucleotide changes in 19 HTLV-1 isolates from WB-indeterminate samples, we identified 135 single nucleotide substitutions, composed of four types, G to A (29%), C to T (19%), T to C (19%), and A to G (16%). In the most frequent G-to-A substitution, 64% occurred at GG dinucleotides, indicating that APOBEC3G is responsible for mutagenesis in WB-indeterminate samples. Moreover, interestingly, five WB-indeterminate isolates had nonsense mutations in Pol and/or Tax, Env, p12, and p30. These findings suggest that WB-indeterminate carriers have low production of viral antigens because of a combination of a low proviral load and mutations in the provirus, which may interfere with host recognition of HTLV-1 antigens.

Adult T-cell leukemia/lymphoma (ATL) occurs in approximately 5% of individuals infected with human T-cell leukemia virus type 1 (HTLV-1). A high proviral load (PVL; more than four copies per 100 peripheral blood mononuclear cells (PBMCs) or 1.6 copies per 100 blood leukocytes) and being male are risk factors for ATL development. Whether anti-HTLV-1 antibody level is related to such risk is unknown. Here, PVL and antibody levels were examined using real-time PCR and other tests in 600 HTLV-1 positive screened Japanese blood donors to understand the relationship between PVL and antibody level in asymptomatic carriers and to gain insights toward better antibody testing for HTLV-1 infection. The 430 donors in whom proviral DNA was detected were considered as true positives for HTLV-1 infection. Among donors aged 40 years or older, more males than females had a PVL corresponding to more than 1.6% infected leukocytes, and an antibody titer below the median (P = 0.0018). In antibody tests using an HTLV-1 positive cell line or Env antigens there was a large discrepancy in antibody titer among 13 provirus-positive samples, probably suggesting that antibody-based screening tests should incorporate multiple HTLV-1 antigens, such as Gag and Env antigens.

Human T-lymphotropic virus 1 (HTLV-1) infection has an especially high prevalence in Japan. Transmission has been confirmed in infancy through breastfeeding; however, little is known about the epidemiological aspects of new HTLV-1 infections later in life. We aimed to estimate the nationwide annual number of new HTLV-1 infections among adolescents and adults in Japan.In this retrospective cohort analysis, we assessed new HTLV-1 infections of repeat blood donors aged 16-69 years between Jan 1, 2005, and Dec 31, 2006, in the Japanese Red Cross Blood Centres database. We used results of antibody tests done in repeat blood samples collected until Dec 31, 2011, to assess the number who seroconverted to HTLV-1. We calculated the incidence density by dividing the number of seroconverters by the number of person-years of follow-up, and then extrapolated densities to regional populations to estimate the annual number of new HTLV-1 infections.We included 3 375 821 HTLV-1-seronegative blood donors (2 100 915 men and 1 274 906 women). Within a median follow-up of 4·5 years (IQR 2·3-5·8), 532 people (204 men and 328 women) had seroconverted. The incidence density was significantly higher in women (6·88 per 100 000 person-years; 95% CI 6·17-7·66) than in men (2·29 per 100 000 person-years; 95% CI 1·99-2·62; p0·0001). The estimated annual number of new HTLV-1 infections was 4190 (95% CI 4064-4318) with 975 (914-1038) infections in men and 3215 (3104-3328) in women.New HTLV-1 infections in adolescents and adults are an important public health concern in Japan and preventive strategies are needed to reduce new transmission.Ministry of Health, Labour, and Welfare of Japan; Japan Agency for Medical Research and Development.

Elevated levels of soluble CD30 (sCD30) are linked with various T-cell neoplasms. However, the relationship between sCD30 levels and the development of adult T-cell leukemia (ATL) in human T-cell leukemia virus type 1 (HTLV-1) carriers remains to be clarified. We here investigated whether plasma sCD30 is associated with risk of ATL in a nested case-control study within a cohort of HTLV-1 carriers. We compared sCD30 levels between 11 cases (i.e., HTLV-1 carriers who later progressed to ATL) and 22 age-, sex- and institution-matched control HTLV-1 carriers (i.e., those with no progression). The sCD30 concentration at baseline was significantly higher in cases than in controls (median 65.8, range 27.2-134.5 U/mL vs. median 22.2, range 8.4-63.1 U/mL, P=0.001). In the univariate logistic regression analysis, a higher sCD30 (≥30.2 U/mL) was significantly associated with ATL development (odds ratio 7.88 and the 95% confidence intervals 1.35-45.8, P = 0.02). Among cases, sCD30 concentration tended to increase at the time of diagnosis of aggressive-type ATL, but the concentration was stable in those developing the smoldering-type. This suggests that sCD30 may serve as a predictive marker for the onset of aggressive-type ATL in HTLV-1 carriers.

We investigated the incidence of human T-cell leukemia virus type I (HTLV-1) infection in a total of 17 regions in four countries, including 13 regions in Japan, as well as Korea (Seoul and Busan), China, and Vietnam, by testing breast milk using a particle agglutination assay (PA) and line immunoassay (LIA). Among 266 samples from Japan, 24 (9.0%) were positive on PA and 3 (1.1%) were positive on LIA. Among 50 samples from Seoul, 2 were positive on PA and 1 was positive on LIA. In contrast, all 50 samples from Busan were negative on both tests, suggesting the maldistribution of HTLV-1 infectants in South Korea. The numbers of positive samples were 2/91 on PA and 1/91 on LIA for China and 1/88 on both PA and LIA for Vietnam. In China, one sample with a high probability of HTLV-2 infection was identified by LIA and synthetic peptide enzyme-linked immunosorbent assay (ELISA). We examined HTLV-1 antibody in breast milk samples using commercially available test kits, suggesting the existence of HTLV-1 carriers in endemic areas in Southeast Asia and an HTLV-2 infectant in China. As a part of human ethno-epidemiological research, these results constitute valuable epidemiological data. Further studies on the sensitivity, specificity, and reliability of assays using antibodies to HTLV-1 and 2 in breast milk will be necessary for large-scale epidemiological surveys of HTLV infection.

Adult T-cell leukemia/lymphoma (ATLL) is a lymphoproliferative disease caused by human T-cell lymphotropic virus type 1 (HTLV-1) infection. HTLV-1 is spread by cell-to-cell transmission via the gp46-197 region, from Asp197 to Leu216, in the envelope protein gp46. A correlation exists between the prevalence and titer of the antibody recognizing the gp46-197 region (anti-gp46-197 antibody) and the severity of ATLL. In the present study, immunohistochemical staining was performed on samples of paraffin embedded lymph nodes of three different histological types of ATLL (anaplastic large cell type, n = 10; pleomorphic type, n = 10; and Hodgkin's-like type, n = 10) from 30 cases and 10 cases of HTLV-associated lymphadenitis. Of the three ATLL subtypes, gp46 expression was highest in the anaplastic large cell type, followed by the pleomorphic type and Hodgkin's-like type (mean: 53.4%, 34.9% and 16.0%, respectively; P= 0.0003). In HTLV-1 associated lymphadenitis cases, gp46 positive cells were rarely seen (4.0%). These results suggest that gp46-197 immunohistochemical staining can be a useful histological indicator for prediction of the aggressiveness of ATLL and prognosis for ATLL patients.

Definitive risk factors for the development of adult T-cell leukemia (ATL) among asymptomatic human T-cell leukemia virus type I (HTLV-1) carriers remain unclear. Recently, HTLV-1 proviral loads have been evaluated as important predictors of ATL, but a few small prospective studies have been conducted. We prospectively evaluated 1218 asymptomatic HTLV-1 carriers (426 males and 792 females) who were enrolled during 2002 to 2008. The proviral load at enrollment was significantly higher in males than females (median, 2.10 vs 1.39 copies/100 peripheral blood mononuclear cells [PBMCs]; P < .001), in those 40 to 49 and 50 to 59 years of age than that of those 40 years of age and younger (P = .02 and .007, respectively), and in those with a family history of ATL than those without the history (median, 2.32 vs 1.33 copies/100 PBMCs; P = .005). During follow-up, 14 participants progressed to overt ATL. Their baseline proviral load was high (range, 4.17-28.58 copies/100 PBMCs). None developed ATL among those with a baseline proviral load lower than approximately 4 copies. Multivariate Cox analyses indicated that not only a higher proviral load, advanced age, family history of ATL, and first opportunity for HTLV-1 testing during treatment for other diseases were independent risk factors for progression of ATL.

Human T-cell leukemia virus type-1 (HTLV-1) causes adult T-cell leukemia/lymphoma (ATL), frequently associated with hypercalcemia and bone destruction. A positive correlation between the appearance of an antibody recognizing the central region (Asp197 to Leu216) on Gp46, gp46-197, and the severity of ATL has been demonstrated. In this study, five male Nihon Hakusyoku rabbits were immunized with a synthetic peptide corresponding to the gp46-197 region to clarify its action and mechanism. Two of the rabbits showed piloerection, anorexia, and somnolence, and died soon after booster administration. The serum calcium level of the dead rabbits was significantly high, compared to those of surviving rabbits. Interestingly, amino acid sequences homologous with gp46-197 were found in the carboxyl-terminal half of osteoprotegerin (OPG), an osteoclast inhibitory factor. To confirm the effect of the gp46-197 region on osteogenesis in vivo, the peptide was intraperitoneally administered to male Sprague-Dawley rats. The administration of the gp46-197 peptide resulted in a decrease of bone mineral density (BMD), a significant increase of serum calcium level, and inhibition of normal bone growth in both short- and long-term experiments. In rats, femoral growth inhibition by the gp46-197 peptide was restored by the coadministration of recombinant human OPG. Improvement by OPG in the adverse effect indicates that the central region of HTLV-1 Gp46 acts as an antagonist for OPG and leads to hypercalcemia.

Human T-lymphotropic virus type 1 (HTLV-1) infection is known to affect hepatitis C virus (HCV) clearance and to accelerate the development of hepatocellular carcinoma in HCV-infected patients. In this study, we found the prevalence and titer of an antibody recognizing the central region of the HTLV-1 Gp46 protein to be associated with the severity of chronic liver disease. The antibody prevalence was significantly correlated with the stage of chronic liver disease (P < 0.0001): 3 (14.3%) of 21 patients with minimal-mild chronic hepatitis, 12 (24%) of 50 with moderate-severe chronic hepatitis, 7 (87.5%) of 8 with liver cirrhosis, and 13 (100%) of 13 with hepatocellular carcinoma. These results indicate that the antibody may be a useful marker of the deterioration of liver disease in patients co-infected with HCV and HTLV-1. This antibody may be useful for the diagnosis of liver diseases and the development of more effective treatments.

Human T-cell lymphotropic virus type 1 (HTLV-1) is an etiologic agent of adult T-cell leukemia/lymphoma (ATL). HTLV-1 is spread by cell-to-cell transmission via the gp46-197 region, Asp197 to Leu216, on the envelope protein gp46. In the present study, we revealed a positive correlation between the appearance of an antibody recognizing the gp46-197 region (anti-gp46-197 antibody) and the severity of ATL. The prevalence and titer of the anti-gp46-197 antibody were found to be elevated along with the progression of ATL. In serial samples obtained from a single patient, the anti-gp46-197 antibody was detected before treatment in acute phase, then diminished after allogeneic bone marrow transplantation, to which the patient had a complete response. However, the antibody appeared again before a relapse, along with an increase of the serum-soluble interleukin-2 receptor level and proviral load. The results from the other six patients also indicate that seroconversion of this antibody was synchronized with the deterioration of ATL. Taken together, the findings indicate that the anti-gp46-197 antibody may be a novel beacon for gauging the efficacy of therapeutic approaches to ATL, and a survey of this antibody would be useful for identifying asymptomatic carriers infected with HTLV-1 who are at high risk of developing ATL.

Quantitative PCR (qPCR) analysis of human T-cell leukemia virus type 1 (HTLV-1) was used to assess the amount of HTLV-1 provirus DNA integrated into the genomic DNA of host blood cells. Accumulating evidence indicates that a high proviral load is one of the risk factors for the development of adult T-cell leukemia/lymphoma and HTLV-1-associated myelopathy/tropical spastic paraparesis. However, interlaboratory variability in qPCR results makes it difficult to assess the differences in reported proviral loads between laboratories. To remedy this situation, we attempted to minimize discrepancies between laboratories through standardization of HTLV-1 qPCR in a collaborative study. TL-Om1 cells that harbor the HTLV-1 provirus were serially diluted with peripheral blood mononuclear cells to prepare a candidate standard. By statistically evaluating the proviral loads of the standard and those determined using in-house qPCR methods at each laboratory, we determined the relative ratios of the measured values in the laboratories to the theoretical values of the TL-Om1 standard. The relative ratios of the laboratories ranged from 0.84 to 4.45. Next, we corrected the proviral loads of the clinical samples from HTLV-1 carriers using the relative ratio. As expected, the overall differences between the laboratories were reduced by half, from 7.4-fold to 3.8-fold on average, after applying the correction. HTLV-1 qPCR can be standardized using TL-Om1 cells as a standard and by determining the relative ratio of the measured to the theoretical standard values in each laboratory.

We previously showed that 71-kDa heat shock cognate protein (HSC70) functions as a cellular receptor for gp46 protein via the gp46-197 region, corresponding to Asp197 to Leu216 of human T-cell lymphotropic virus type 1 (HTLV-1), leading to cell-to-cell transmission of HTLV-1. We found that HSC70 protein was contained in goat serum and casein used as blocking agents in the usual ELISA method. Here, it was demonstrated that HSC70 contamination in the blocking agents causes a false-negative result in the detection of anti-gp46-197 antibody in serum samples from HTLV-1-infected individuals. By using ELISA without the blocking agents, we detected antibodies recognizing the HSC70-binding site of gp46, and the anti-gp46-197 antibody specifically appeared in sera from patients with HTLV-1-associated diseases. The frequency of serum anti-gp46-197 antibody-positive individuals was 98% and 100% among ATLL and HAM/TSP patients, respectively, but only 6% among asymptomatic HTLV-1-infected carriers (ACs). The antibody titer in ATLL and HAM/TSP patients was higher than that in ACs (P < 0.002 for ATLL; P < 0.0001 for HAM/TSP). These findings suggest that appearance of the anti-gp46-197 antibody is a predictive marker for the onset of HTLV-1-associated disease.

71kDa heat shock cognate protein (HSC70) is a member of the Hsp70 family and is constitutively expressed in organisms as diverse as slime molds, bacteria, plants and higher eukaryotes. Proteins in the Hsp70 family are known as chaperones that involve quality control of cellular proteins, folding of nascent polypeptide chains and trafficking of proteins via membrane structure. Recently, it was revealed that Hsp/HSC70 proteins were presented on surface of virus- or bacteria-infected cells, immortalized cells and blood cells of autoimmune disease patients. We previously reported that the HTLV-1 receptor consists of HSC70, β-actin and phosphatidylglycerol on the surface of MOLT-4 cells. In this study, we examined the induction of HSC70 protein on the surface of peripheral blood mononuclear cells (PBMCs) from healthy individuals. Little HSC70 protein was observed on the surface of PBMCs before cultivation. However, after 72 hours culture, 41±9.1% of PBMCs presented HSC70 proteins on the cell surface. On the other hand, in culture with phytohemagglutinin (PHA), 70±14% of PBMCs exposed HSC70 protein on the cell surface after 24 hours, and 84±5.0% after 72 hours. PHA stimulated the presentation of HSC70 protein on the cell surface of CD4+ T cells, which are the target cells of HTLV-1 in vivo, as well as that on the surface of PBMCs. Susceptibility to HTLV-1 of target cells was parallel to the expression level of HSC70 molecules on the cell surface. These results demonstrate that HSC70 protein on the surface of PBMCs and CD4+ T cells exposes the domains which are functional for HTLV-1 infection, and that stimulation by cultivation and mitogen enhances the trafficking of HSC70 proteins to the surface of plasma membrane. This is the first finding that HSC70 on the surface of CD4+ T cells functions as a receptor for cell-to-cell transmission of HTLV-1.

Although a serum thermolabile β-2 macroglycoprotein (TMG) may play a role in host defense as a lectin, little is known of its related physiological functions, mainly due to a lack of appropriate methods for tracing the functions of TMG. We identified a polysaccharide from Aerococcus viridans , PSA, which reacts with TMG, and based on this finding, we developed an enzyme-linked immunosorbent assay to trace the functions of TMG. Using ethanol precipitation and DEAE-Sepharose and Sephacryl S-400 column chromatographies, we isolated PSA from cultured medium of A. viridans , and it exhibited specific binding against TMG in blood samples. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the isolated PSA showed ladder bands that implied the existence of repeating units composed of d -glucose, N -acetyl- d -glucosamine, d -mannose, and d -xylose, as confirmed by gas chromatography-mass spectrometry. SDS-PAGE and immunochemical analysis, using rabbit anti-TMG antibody, showed that PSA specifically binds solely to intact serum TMG but not to TMG heated at 56°C for 30 min, a condition under which antigenicity is lost. TMG in serum samples bound to PSA in a dose-dependent manner, and this binding was clearly suppressed by addition of PSA. These observations indicate that PSA is a useful adsorbent to TMG and can be used to develop appropriate methods for tracing the functions of TMG.

Human T-cell lymphotropic virus type 1 (HTLV-1) envelope proteins play an important role in viral entry into target cells. In a syncytium formation assay consisting of a coculture of HTLV-1-bearing cells and target cells, mature gp46 and gp21 proteins each inhibited syncytium formation induced by HTLV-1-bearing cells. Experiments with 125I-labeled proteins showed that 125I-gp46 bound specifically with MOLT-4 target cells even in the presence of large amounts of gp21, whereas 125I-gp21 binding to target cells was completely blocked in the presence of large amounts of gp46. These observations suggest that HTLV-1 envelope proteins in syncytium formation interact with at least two components, which are located close to each other on the cell membrane. We isolated two components from MOLT-4 cell lysate, using Sepharose 4B columns coupled with peptides corresponding to amino acids 197 to 216 and 400 to 429, respectively, of the envelope protein. One is a trypsin digestion-sensitive component of approximately 34 to 35 kDa, which interacts specifically with gp46. The other is a nonprotein component, which interacts with gp21. This component was destroyed by sodium periodate oxidation and was partitioned into the methanol-chloroform phase. These observations suggest that these two components play an important role in HTLV-1 entry into target cells via membrane fusion.

To identify the regions that are important in human T-cell leukemia virus type 1 (HTLV-1) envelope function, we synthesized 23 kinds of peptides covering the envelope proteins and examined the inhibitory effect of each peptide on syncytium formation induced by HTLV-1-bearing cells. Of the 23 synthetic peptides, 2, corresponding to amino acids 197 to 216 on gp46 and 400 to 429 on gp21, inhibited syncytium formation induced by HTLV-1-bearing cells but did not affect syncytium formation induced by human immunodeficiency virus type 1-producing cells. The peptide concentrations giving 50% inhibition of syncytium formation for gp46 197 to 216 and gp21 400 to 429 were 14.9 and 6.0 microM, respectively. A syncytium formation assay with overlapping synthetic peptides containing amino acids 175 to 236 and 391 to 448 of the envelope proteins showed that syncytium formation was inhibited by peptides that contained the amino acid sequences 197 to 205 (Asp-His-Ile-Leu-Glu-Pro-Ser-Ile-Pro) and 397 to 406 (Gln-Glu-Gln-Cys-Arg-Phe- Pro-Asn-Ile-Thr). These observations suggest that the two regions corresponding to amino acids 197 to 216 and 400 to 429 are involved] in HTLV-1 envelope function.

The gene structure of bovine adrenodoxin (Ad), a component of the steroid hydroxylating system in adrenal cortex mitochondria, was determined. This gene seems to be a single copy, but contains a pseudo exon in addition to the genuine gene region. The gene region for the active Ad is divided into 4 exons by 3 introns, and spans at least 27 kb. All the splice donor and acceptor sites follow the GT/AG rule. The transcription initiation site was determined by primer extension analysis, and putative TATA and GC boxes are present in the 5'-flanking region. A 12 base sequence, CCAGGGCCAGGG, is present 95 bases upstream from the transcription initiation site. A similar sequence was also found in the 5'-flanking regions of all genes for the steroid hydroxylating cytochromes P-450: P-450(SCC), P-450(11 beta), P-450(17 alpha), and P-450(C21), in the adrenal cortex. The consensus sequence for these five sequences is CGCAGGGCCATGGGA. The pseudo exon, exon 1', was present about 0.5 kb upstream from exon 1. It encodes the prepeptide region of the minor type Ad mRNA, but has a stop codon (TAA) in the frame. A TATA-box-like sequence and a CAAT-box-like sequence are also present in the 5'-flanking region of exon 1'. The GC content of exon 1 was over 80%, whereas for each of the other four exons, including exon 1', it was about 40%. Our observations suggest that exon 1, which encodes the prepeptide region of the major type Ad mRNA, has intruded into the region between exon 1' and exon 2.

Background : Hakata antigen (Hakata) is a novel serum glycoprotein that consists of collagen- and fibrinogen-like domains, similar to ficolin/p35. Our research suggested that serum Hakata may be a target of a polysaccharide (PSA) produced by Aerococcus viridans . Methods : A. viridans was incubated with human plasma and Hakata-depleted plasma to examine Hakata binding and growth inhibition of A. viridans through binding with PSA. Results : When A. viridans was mixed with human acid citrate dextrose-one (ACD-A) plasma, it pulled down Hakata complexed with mannose-binding lectin (MBL)-associated serine proteases 1 and 2 (MASP-1 and MASP-2). This complex had the potential for C4 deposition. Serum Hakata circulates as Hakata–MASPs complex in the blood and is proteolytically active. By mixing A. viridans with human plasma, we prepared a Hakata-depleted plasma, deficient in Hakata–MASPs complex. This plasma failed to inhibit A. viridans growth plasma, but does not inhibit Staphylococcus aureus , Yersinia enterocolitica and Escherichia coli . However, a decrease of growth inhibition of A. viridans in Hakata-depleted plasma could be restored by adding a Hakata–MASPs complex preparation in a dose-dependent manner. On the other hand, the Hakata–MASPs complex exhibited strong binding to A. viridans , but not to S. aureus , Y. enterocolitica and E. coli . Conclusions : The serum concentration of Hakata is linked with growth inhibition of A. viridans upon binding of Hakata via PSA.

Adult T-cell leukemia /lymphoma (ATL) caused by human retrovirus, HTLV-1, is a neoplasm of mature T-cell. ATL is still an incurable disease with approximately 1,000 annual deaths in Japan. The useful biomarkers are required to achieve the success of treatment. In order to test whether or not two soluble cytokine receptors (sCD25 and sCD30) are useful biomarkers of the development of ATL, we investigated changes in the concentration of the two markers in 11 HTLV-1 carriers (pre/post ATL progression) and six patients with chronic ATL (pre/post acute crisis). Serum (or plasma) samples of newly diagnosed or referred ATL patients and HTLV-1 carriers were preserved in freezer to measure the level of soluble proteins, sCD25 and sCD30, using ELISA. The sCD25 concentration was measured by Cell freeN IL-2R (Kyowa Medex, Japan) and Determiner CL IL-2R (Kyowa Medex, Japan). The sCD30 concentration was measured by Human sCD30 Platinum ELISA (eBioscience). The probability of ATL development from HTLV-1 carrier state was analysed by Kaplan-Meier method. We found that the elevation of soluble cytokine receptors was one of the earlier events of ATL development. In addition, chronic type patients followed in our hospital showed sCD30 as well as sCD25 elevation prior to the diagnosis of acute crisis. Our findings suggest that a combination of sCD25 and sCD30 facilitates accurate diagnosis and intervention of ATL as useful biological markers. Further careful follow-up should be required for HTLV-1 carriers with elevated level of cytokine receptors, sCD25 and sCD30 to diagnose the early phase of ATL.

We previously reported that 71-kDa heat shock cognate protein (HSC70) was expressed on the cell surface of human T cell lymphotropic virus type 1 (HTLV-1)-susceptible cells and that HSC70, beta-actin, and a lipid-like component on the target cell membrane participated in syncytium formation by HTLV-1. We have now identified this lipid-like component to be palmitoyl (16:0)-oleoyl (18:1)-phosphatidylglycerol (POPG), using preparative thin-layer chromatographic fractionation and tandem mass spectrometric analysis. In the syncytium formation assay, exogenously added PG inhibited cell-to-cell transmission of HTLV-1 in a dose-dependent manner. Other phospholipids showed less (PE) or no effect (PC, PS, PI, PA, lysoPC, lysoPE, and CL). Binding experiments showed that PG interacted with three synthetic peptides, gp46--111, gp46--197, and gp21--400, which correspond to regions Lys111--Asp138 and Asp197--Leu216 on the gp46 surface glycoprotein, and to region Cys400--Leu429 on the gp21 transmembrane glycoprotein, respectively, as well as with intact gp46 and gp21 proteins of HTLV-1. On the other hand, HSC70 and beta-actin interacted with gp46--197 and gp46, not with gp46--111. However, the eluate from an affinity column coupled with gp46--111 contained not only PG but also HSC70 and beta-actin, despite the lack of direct interaction between gp46--111 and these proteins. In the in vitro binding assay, HSC70 showed interaction with both PG and beta-actin, while there was no evidence of any interaction between PG and beta-actin. These results suggest that HSC70 molecules on target cell surface interact with both PG in lipid bilayers and intracellular beta-actin and that these three cellular components form a receptor complex that plays a critical role in syncytium formation induced by HTLV-1-bearing cells.

In syncytium formation induced by HTLV-1-bearing cells, 71-kDa heat shock cognate protein (HSC70) functions as a receptor molecule and the receptor complex with beta-actin and palmitoyl(16:0)-oleoyl(18:1)-phosphatidylglycerol (PG) is thus formed. We now have evidence that the molecular association between HTLV-1 gp46 envelope protein and HSC70 led to pore formation on the surface of target cell membrane and cell death followed. The peptide segment corresponding to the region from Asp-197 to Leu-216 (gp46-197), and which serves as a binding site to both HSC70 and PG for syncytium formation, also had cytotoxic effects on target cell MOLT-4. This cytotoxicity was due to necrosis, not apoptosis. On the other hand, two other receptor-binding sites, Lys-111 to Asp-138 on gp46 (gp46-111) and Cys-400 to Leu-429 on gp21 (gp21-400), and which bound only with PG, had no cytotoxic effects on MOLT-4 cells. The HTLV-2 peptide (gp46-194; Glu194 to Leu-213) corresponding to the region of HTLV-1 gp46-197 showed no cytotoxicity, and interacted only with PG, not with either HSC70 or beta-actin. Amino acid alterations between HTLV-1 gp46-197 and HTLV-2 gp46-194 were significant on the hydrophilic face of the amphipathic structure. Taken together, the interaction between HSC70 and gp46 of HTLV-1 through the hydrophilic face of gp46-197 may lead to pore formation in lipid bilayers to be followed by membrane fusion or cell death.

We previously reported that the region corresponding to amino acids 197 to 216 of the gp46 surface glycoprotein (gp46-197) served as a binding domain for the interaction between gp46 and trypsin-sensitive membrane components of the target cell, leading to syncytium formation induced by human T-cell lymphotropic virus type 1 (HTLV-1)-bearing cells. Our new evidence shows that the 71-kDa heat shock cognate protein (HSC70) acts as a cellular receptor for syncytium formation. Using affinity chromatography with the peptide gp46-197, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, we isolated three components (bands A, B, and C) from MOLT-4 cell lysate which exhibited specific interactions with gp46 and inhibitory activities for syncytium formation induced by HTLV-1-bearing cells. Band A and B components were identified as HSC70 and β-actin, respectively, through amino acid sequencing by tandem mass spectrometry and immunostaining with specific monoclonal antibodies. Band C is likely to be a nonprotein component, because full activity for syncytium formation was seen after extensive trypsin digestion. Anti-HSC70 monoclonal antibody clearly blocked syncytium formation in a coculture of HTLV-1-bearing cells and indicator cells, whereas no inhibition was seen with anti-β-actin monoclonal antibody. Furthermore, flow cytometric analysis indicated that anti-HSC70 antibody reacted with MOLT-4 cells. Thus, we propose that HSC70 expressed on the target cell surface acts as a cellular acceptor to gp46 exposed on the HTLV-1-infected cell for syncytium formation, thereby leading to cell-to-cell transmission of HTLV-1.

HTLV-1 is the causative retrovirus of ATL. Eighty percent of ATL patients develop hypercalcemia, a severe complication resulting from bone resorption. PTHrP is known as the major pathogenic factor to hypercalcemia associated malignancies. Recently, we observed hypercalcemia in rabbits with antibody against central region of HTLV-1 Env Gp46 (gp46-197), which shows a homology with osteoprotegerin (OPG), an inhibitor to the maturation of osteoclasts. To observe the effect of gp46197 synthetic peptide on osteogenesis, the peptide was intraperitoneally administered to mice in the presence or absence of co-administration of E2. Seven days later, serum E2 level and bone mineral density (BMD) were measured. Both of males and females exhibited a clear reduction in E2 and BMD by the gp46-197 peptide. Histomorphological analyses revealed that the peptide induced the loss of Ob.S/BS and increase in ES/BS, N. Oc/B.Pm, and Oc.S/BS. These results suggest that the structural mimicry of gp46-197 inhibits the OPG function and promote the maturation and stimulation of osteoclasts in vivo. Co-administration of E2 abrogated the adverse effects by gp46-197. This is a novel mechanism of osteolysis directly induced by HTLV-1 structural protein. We presume the therapeutic potential of E2 for the treatment of hypercalcemia in ATL patients.