Search

Beiji nairovirus (BJNV), in the family Nairoviridae, the order Bunyavirales, was recently reported as a causative agent of an emerging tick-borne zoonotic infection in China. This study investigated the prevalence of BJNV in ticks in Japan. Screening of over 2,000 ticks from multiple regions revealed a widespread distribution of BJNV and BJNV-related viruses in Japan, particularly in the northern island, and in other high altitude areas with exclusive occurrence of Ixodesticks. Phylogenetic analysis identified three distinct groups of nairoviruses in ticks in Japan: BJNV, Yichun nairovirus (YCNV) and a newly identified Mikuni nairovirus (MKNV). BJNV and YCNV variants identified in ticks in Japan exhibited high nucleotide sequence identities to those in China and Russia with evidence of non-monophyletic evolution among BJNVs, suggesting multiple cross-border transmission events of BJNV between the Eurasian continent and Japan. Whole genome sequencing of BJNV and MKNV revealed a unique GA-rich region in the S segment, the significance of which remains to be determined. In conclusion, the present study has shown a wide distribution and diversity of BJNV-related nairoviruses in Ixodesticks in Japan and has identified unique genomic structures. The findings demonstrate the significance of BJNV as well as related viruses in Japan and highlight the necessity of monitoring emerging nairovirus infections and their potential risks to public health.

In parallel with vaccination, oral antiviral agents are highly anticipated to act as countermeasures for the treatment of the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Oral antiviral medication demands not only high antiviral activity but also target specificity, favorable oral bioavailability, and high metabolic stability. Although a large number of compounds have been identified as potential inhibitors of SARS-CoV-2 infection in vitro, few have proven to be effective in vivo. Here, we show that oral administration of S-217622 (ensitrelvir), an inhibitor of SARS-CoV-2 main protease (Mpro; also known as 3C-like protease), decreases viral load and ameliorates disease severity in SARS-CoV-2–infected hamsters. S-217622 inhibited viral proliferation at low nanomolar to submicromolar concentrations in cells. Oral administration of S-217622 demonstrated favorable pharmacokinetic properties and accelerated recovery from acute SARS-CoV-2 infection in hamster recipients. Moreover, S-217622 exerted antiviral activity against SARS-CoV-2 variants of concern, including the highly pathogenic Delta variant and the recently emerged Omicron BA.5 and BA.2.75 variants. Overall, our study provides evidence that S-217622, an antiviral agent that is under evaluation in a phase 3 clinical trial (clinical trial registration no. jRCT2031210350), has remarkable antiviral potency and efficacy against SARS-CoV-2 and is a prospective oral therapeutic option for COVID-19.

Adult T-cell leukemia/lymphoma (ATL) is an aggressive neoplasm caused by human T-cell leukemia virus type 1 (HTLV-1). The HTLV-1 oncoprotein Tax plays an important role in ATL pathogenesis. ATL carries a poor prognosis due to chemotherapy resistance, stressing the need for alternative therapies. Here, we investigate the preclinical efficacy of the synthetic retinoid ST1926 in ATL and peripheral T-cell lymphomas. Clinically achievable concentrations of ST1926 induced a dramatic inhibition of cell proliferation in malignant T-cell lines and primary ATL cells with minimal effect on resting or activated normal lymphocytes. ST1926 induced apoptosis, DNA damage, and upregulation of p53 proteins in malignant T cells, whereas it caused an early downregulation of Tax proteins in HTLV-1–positive cells. In murine ATL, oral treatment with ST1926 prolonged survival and reduced leukemia cell infiltration, white blood cell counts, and spleen mass. In spleens of ST1926-treated animals, p53 and p21 proteins were upregulated, poly (ADP-ribose) polymerase was cleaved, and Tax transcripts were reduced. These results highlight the promising use of ST1926 as a targeted therapy for ATL.

Adult T-cell leukemia/lymphoma (ATL) is an aggressive neoplasm caused by human T-cell leukemia virus type 1 (HTLV-1). The HTLV-1 oncoprotein Tax plays an important role in ATL pathogenesis. ATL carries a poor prognosis due to chemotherapy resistance, stressing the need for alternative therapies. Here, we investigate the preclinical efficacy of the synthetic retinoid ST1926 in ATL and peripheral T-cell lymphomas. Clinically achievable concentrations of ST1926 induced a dramatic inhibition of cell proliferation in malignant T-cell lines and primary ATL cells with minimal effect on resting or activated normal lymphocytes. ST1926 induced apoptosis, DNA damage, and upregulation of p53 proteins in malignant T cells, whereas it caused an early downregulation of Tax proteins in HTLV-1–positive cells. In murine ATL, oral treatment with ST1926 prolonged survival and reduced leukemia cell infiltration, white blood cell counts, and spleen mass. In spleens of ST1926-treated animals, p53 and p21 proteins were upregulated, poly (ADP-ribose) polymerase was cleaved, and Tax transcripts were reduced. These results highlight the promising use of ST1926 as a targeted therapy for ATL.

Adult T-cell leukemia/lymphoma (ATL) is a highly invasive and intractable T-cell malignancy caused by human T-cell leukemia virus-1 infection. We demonstrate herein that normal tissue–derived epithelial cells (NECs) exert protective effects on the survival of leukemic cells, which may partially account for high resistance to antileukemic therapies in patients with ATL. Viral gene–silenced, ATL-derived cell lines (ATL cells) dramatically escaped from histone deacetylase inhibitor–induced apoptosis by direct co-culture with NECs. Adhesions to NECs suppressed p21Cip1expression and increased a proportion of resting G0/G1 phase cells in trichostatin A (TSA)–treated ATL cells. ATL cells adhering to NECs down-regulated CD25 expression and enhanced vimentin expression, suggesting that most ATL cells acquired a quiescent state by cell-cell interactions with NECs. ATL cells adhering to NECs displayed highly elevated expression of the cancer stem cell marker CD44. Blockade of CD44 signaling diminished the NEC-conferred resistance of ATL cells to TSA-induced apoptosis. Co-culture with NECs also suppressed the expression of NKG2D ligands on TSA-treated ATL cells, resulting in decreased natural killer cell–mediated cytotoxicity. Combined evidence suggests that interactions with normal epithelial cells augment the resistance of ATL cells to TSA-induced apoptosis and facilitate immune evasion by ATL cells.

ABSTRACTHuman cytomegalovirus (HCMV) strains may be genotyped based on polymorphisms that exist within the UL144 gene, which is one of 19 viral genes lost in attenuated laboratory strains. In the present study, UL144 genotypes in congenitally infected babies (congenital cytomegalovirus [cCMV]) were determined, and the relationship between the genotype, viral load, cytokine profile, and patient developmental outcome was investigated. All cCMV infections identified during 2006 and 2007 were included (n= 29). A portion of the infants were clinically assessed at birth and at 12 to 18 months postinfection for cCMV clinical sequelae (n= 18/29). The plasma viral load (PVL) was requested for 23/29 patients, and the UL144 genotype was determined (n= 27/29). The cytokine profile in patient plasma or serum was assessed (n= 20/29). UL144 genotypes A, B, and C were detected within the cCMV population at 33.3%, 29.6%, and 25.9%, respectively. UL144 A and C were associated with a high PVL (P< 0.04). Furthermore, a significant association between the developmental outcome and UL144 A and C was observed (P< 0.04). Only patients infected with UL144 B and A/B were described as having a normal clinical outcome. In addition, a significant correlation between interleukin 10 (IL-10) levels and the PVL was observed (P< 0.04); however, there was no association between the genotype and the cytokine profile. The present study determined that the specific detection of UL144 genotypes A and C was indicative of serious cCMV infection and more likely to lead to long-term cCMV-associated clinical manifestations. The inclusion of HCMV UL144 genotyping along with the recommended PVL monitoring following cCMV diagnosis may aid prediction of the clinical outcome.

ABSTRACTMumps is a vaccine-preventable disease; however, outbreaks have been reported in a number of countries with childhood immunization programs, particularly among young adults at the tertiary stage of education. We have retrospectively investigated the epidemiological, virological, and serological factors associated with mumps cases identified in Ireland from 2004 to 2009. Genetic analysis of mumps virus strain variability demonstrated that a single genotype, genotype G, was circulating, and it was also detected in cerebrospinal fluid samples obtained from patients with meningitis. We observed that younger individuals were disproportionately affected with neurological sequelae following mumps virus infection, and the average age of patients with mumps virus RNA detected in cerebrospinal fluid was 19.25 years (median, 19 years; range, 14 to 24 years). Our analysis showed a 4-fold rise in mumps cases in 2008-2009 and an increased incidence in infection in those =30 years of age. Over a 6-year period (2004 to 2009), a total of 7,805 serum samples were investigated; of this number, 1,813 (23%) were positive for mumps virus-specific IgM. We observed a strong bias for acute mumps virus infection in males compared to females (P< 10-32) that was independent of vaccination status.

ABSTRACTMyocarditis is a rare cause of sudden death in childhood. We describe the sudden death of a child from viral myocarditis, which we demonstrate was likely caused by an uncontrolled inflammatory response to a disseminated adenovirus serotype 3 infection originating in the tonsil.

Adult T-cell leukemia (ATL) is a T-cell malignancy caused by human T lymphotropic virus type I, and presents as an aggressive leukemia with characteristic widespread leukemic cell infiltration into visceral organs and skin. The molecular mechanisms associated with leukemic cell infiltration are poorly understood. We have used mouse models of ATL to investigate the role of chemokines in this process. Transfer of splenic lymphomatous cells from transgenic to SCID mice reproduces a leukemia and lymphoma that is histologically identical to human disease. It could be shown that lymphomatous cells exhibit specific chemotactic activity in response to stromal cell–derived factor-1α (SDF-1α). Lymphomatous cells exhibited surface expression of CXCR4, the specific receptor of SDF-1α. AMD3100, a CXCR4 antagonist, was found to inhibit both SDF-1α–induced migration and phosphorylation of extracellular signal-related kinase 1/2. Investigation of cultured cells from human ATL patients revealed identical findings. Using the SCID mouse model, it could be demonstrated that AMD3100 inhibited infiltration of lymphomatous cells into liver and lung tissues in vivo. These results demonstrate the involvement of the SDF-1α/CXCR4 interaction as one mechanism of leukemic cell migration and this may provide a novel target as part of combination therapy for ATL.

Adult T-cell leukemia (ATL) is a T-cell malignancy caused by human T lymphotropic virus type I, and presents as an aggressive leukemia with characteristic widespread leukemic cell infiltration into visceral organs and skin. The molecular mechanisms associated with leukemic cell infiltration are poorly understood. We have used mouse models of ATL to investigate the role of chemokines in this process. Transfer of splenic lymphomatous cells from transgenic to SCID mice reproduces a leukemia and lymphoma that is histologically identical to human disease. It could be shown that lymphomatous cells exhibit specific chemotactic activity in response to stromal cell–derived factor-1α (SDF-1α). Lymphomatous cells exhibited surface expression of CXCR4, the specific receptor of SDF-1α. AMD3100, a CXCR4 antagonist, was found to inhibit both SDF-1α–induced migration and phosphorylation of extracellular signal-related kinase 1/2. Investigation of cultured cells from human ATL patients revealed identical findings. Using the SCID mouse model, it could be demonstrated that AMD3100 inhibited infiltration of lymphomatous cells into liver and lung tissues in vivo. These results demonstrate the involvement of the SDF-1α/CXCR4 interaction as one mechanism of leukemic cell migration and this may provide a novel target as part of combination therapy for ATL.

Adult T-cell leukemia/lymphoma (ATL) is a malignant lymphoproliferative disorder caused by HTLV-I infection. In ATL, chemotherapeutic responses are generally poor, which has suggested the existence of chemotherapy-resistant cancer stem cells (CSCs). To identify CSC candidates in ATL, we have focused on a Tax transgenic mouse (Tax-Tg) model, which reproduces ATL-like disease both in Tax-Tg animals and also after transfer of Tax-Tg splenic lymphomatous cells (SLCs) to nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice. Using a limiting dilution transplantation, it was estimated that one CSC existed per 104 SLCs (0.01%). In agreement with this, we have successfully identified candidate CSCs in a side population (0.06%), which overlapped with a minor population of CD38−/CD71−/CD117+ cells (0.03%). Whereas lymphoma did not develop after transplantation of 102 SLCs, 102 CSCs could consistently regenerate the original lymphoma. In addition, lymphoma and CSCs could also be demonstrated in the bone marrow and CD117+ CSCs were observed in both osteoblastic and vascular niches. In the CSCs, Tax, Notch1, and Bmi1 expression was down-regulated, suggesting that the CSCs were derived from Pro-T cells or early hematopoietic progenitor cells. Taken together, our data demonstrate that CSCs certainly exist and have the potential to regenerate lymphoma in our mouse model.

Adult T-cell leukemia/lymphoma (ATL) is a malignant lymphoproliferative disorder caused by HTLV-I infection. In ATL, chemotherapeutic responses are generally poor, which has suggested the existence of chemotherapy-resistant cancer stem cells (CSCs). To identify CSC candidates in ATL, we have focused on a Tax transgenic mouse (Tax-Tg) model, which reproduces ATL-like disease both in Tax-Tg animals and also after transfer of Tax-Tg splenic lymphomatous cells (SLCs) to nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice. Using a limiting dilution transplantation, it was estimated that one CSC existed per 104SLCs (0.01%). In agreement with this, we have successfully identified candidate CSCs in a side population (0.06%), which overlapped with a minor population of CD38−/CD71−/CD117+cells (0.03%). Whereas lymphoma did not develop after transplantation of 102SLCs, 102CSCs could consistently regenerate the original lymphoma. In addition, lymphoma and CSCs could also be demonstrated in the bone marrow and CD117+CSCs were observed in both osteoblastic and vascular niches. In the CSCs, Tax, Notch1, and Bmi1expression was down-regulated, suggesting that the CSCs were derived from Pro-T cells or early hematopoietic progenitor cells. Taken together, our data demonstrate that CSCs certainly exist and have the potential to regenerate lymphoma in our mouse model.

Pediatric gastroenteritis places a considerable disease burden on children of the developed world. The national surveillance of gastroenteritis in Ireland is a combined virological and epidemiologic surveillance program. The objectives of this study were to characterize the norovirus (NoV) genotypes associated with viral gastroenteritis in children ≤5 y of age, and compare these strains with those detected in adult specimens. A total of five different NoV genotypes were associated with infection in Irish children Genogroup II/type 2 (GII/2),GII/4,GII/6,GII/b,GII/14 whereas only GII/4 strains were identified in adults. This significant genotypic difference in the NoV strains associated with pediatric and adult infection was found in both community- and hospital-based infection. To assess the burden that NoV places on Irish children, the relative prevalence of norovirus, rotavirus, and adenovirus was determined in hospitalized symptomatic children ≤5 y old. Our results identified NoV as a major cause of gastroenteritis in children ≥4 mo of age and determined that NoV and adenovirus infection are equally significant in children in the first 5 y of life. This group of pediatric patients reported diarrhea as their most common symptom raising the question whether Kaplan criteria are the most effective method for clinically diagnosing outbreaks of enteric infection in pediatric patients.

Pediatric gastroenteritis places a considerable disease burden on children of the developed world. The national surveillance of gastroenteritis in Ireland is a combined virological and epidemiologic surveillance program. The objectives of this study were to characterize the norovirus (NoV) genotypes associated with viral gastroenteritis in children =5 y of age, and compare these strains with those detected in adult specimens. A total of five different NoV genotypes were associated with infection in Irish children [Genogroup II/type 2 (GII/2),GII/4,GII/6,GII/b,GII/14] whereas only GII/4 strains were identified in adults. This significant genotypic difference in the NoV strains associated with pediatric and adult infection was found in both community- and hospital-based infection. To assess the burden that NoV places on Irish children, the relative prevalence of norovirus, rotavirus, and adenovirus was determined in hospitalized symptomatic children =5 y old. Our results identified NoV as a major cause of gastroenteritis in children =4 mo of age and determined that NoV and adenovirus infection are equally significant in children in the first 5 y of life. This group of pediatric patients reported diarrhea as their most common symptom raising the question whether Kaplan criteria are the most effective method for clinically diagnosing outbreaks of enteric infection in pediatric patients.

After the first description of TSP/HAM in 1985 and the elaboration of WHO’s diagnostic criteria in 1988, the experience of the professionals in this field has increased so that a critical reappraisal of these diagnostic guidelines was considered timely. Brazilian neurologists and observers from other countries met recently to discuss and propose a modified model for diagnosing TSP/HAM with levels of ascertainment as definite, probable, and possible, according to myelopathic symptoms, serological findings, and/or detection of HTLV-I DNA and exclusion of other disorders.

Human T‐lymphotropic virus type I (HTLV‐I) and type II (HTLV‐II) are closely related retroviruses with similar biological properties and common modes of transmission. HTLV‐I infection is endemic in well‐defined geographic regions, and it is estimated that some 20 million individuals are infected worldwide. Although most infected individuals are asymptomatic carriers, some 2 to 5% will develop a chronic encephalomyelopathy, HTLV‐I–associated myelopathy/tropical spastic paraparesis (HAM/TSP). In contrast with HTLV‐I, the role of HTLV‐II in the development of neurological disorders is much less clear. HTLV‐II is endemic in many native Amerindian groups and epidemic in injecting drug users (IDUs) worldwide. To evaluate the role of HTLV‐II in neurological disease, we have critically reviewed all reported cases of HTLV‐II–associated disorders. This has confirmed that although rare infection is associated with a disorder clinically similar or identical to HAM/TSP. However, most reports that have attributed infection to a range of other neurological disorders are difficult to evaluate in that in many cases either the association appears to be fortuitous or the presentations were confounded by a background of concomitant human immunodeficiency virus–1 infection and/or active IDU. In view of the many HTLV‐II–infected individuals in urban areas of North America and Europe, neurologists should be aware of the potential clinical consequences of this infection.

To investigate the relationship between the fusogenic properties of HTLV-II and the processing of the envelope precursor glycoprotein gp63, recombinant cowpox virus expressing this protein was used to infect a range of cell lines derived from different species. Syncytium formation and gp63 processing were observed in all cells with the exception of LoVo cells, which are known to have a dysfunctional form of the endoprotease, furin. Furin has been shown to be necessary for the processing of a number of viral envelope glycoproteins, and gp63 contains a consensus sequence 305Arg-Arg-Arg-Arg, which is a furin substrate motif. Pulse–chase studies demonstrated gp63 processing in Vero but not in LoVo cells. In addition it could be shown that expression of recombinant furin restored the processing of gp63 to gp46 in LoVo cells, and this resulted in syncytium formation. Our findings suggest that furin plays a pivotal role in cleavage of the HTLV-II envelope gp63, which in turn is a prerequisite for the fusogenic properties of the virus.

ABSTRACTHuman T-cell leukemia virus type 1 (HTLV-1) and HTLV-2 are retroviruses with similar biological properties. Whereas HTLV-1 is the causative agent of an aggressive T-cell leukemia, HTLV-2 has been associated with only a few cases of lymphoproliferative disorders. Tax1 and Tax2 are the transcriptional activators of HTLV-1 and HTLV-2, respectively. Here we show that Tax2 transformed a Rat-1 fibroblast cell line to form colonies in soft agar, but the size and number of the colonies were lower than those of Tax1. Use of a chimeric Tax protein showed that the C-terminal amino acids 300 to 353 were responsible for the high transforming activity of Tax1. Activation of cellular genes by Tax1 through transcription factor NF-?B is reportedly essential for the transformation of Rat-1 cells. Tax2 also activated the transcription through NF-?B in Rat-1 cells, and such activity was equivalent to that induced by Tax1. Thus, the high transforming activity of Tax1 is mediated by mechanisms other than NF-?B activation. Our results showed that Tax2 has a lower transforming activity than Tax1 and suggest that the high transforming activity of Tax1 is involved in the leukemogenic property of HTLV-1.

Polyomavirus JC (JCV) causes the human demyelinating disease, progressive multifocal leukoencephalopathy (PML). The recent demonstration of cases of PML in association with human T-lymphotropic virus type I (HTLV-I) infection prompted us to examine whether the HTLV-I-encoded regulatory protein Tax activates JCV transcription. By employing a dual luciferase assay, we initially found that the expression of Tax activated the transcriptional potential of both early and late promoters of JCV in human neuronal but not in non-neuronal cells. We subsequently analyzed the mechanism of Tax-induced activation of the JCV promoter in neuronal cells with the following results: 1) the JCV promoter that lacks the NF-κB-binding motif could not be activated by Tax; 2) the overexpression of IκBα abolished Tax-induced transcriptional activation of the JCV promoter; 3) a Tax mutant (M22) lacking the potential for activation via the NF-κB pathway did not activate the JCV promoter. Furthermore, Tax enhances the gene expression of JCV T antigen and VP1. We examined mechanisms of the cell-specific activation of the JCV promoter by Tax. Electrophoretic mobility shift assay demonstrated the presence of Tax-bound protein(s) that were specifically present in non-neuronal cells. This study is the first demonstration of the activation of JCV promoter by HTLV-I Tax in an NF-κB-dependent manner.

Analysis of human T-lymphotropic virus type II (HTLV-II) isolates from North America and Europe have demonstrated the existence of two molecular subtypes of the virus, HTLV-IIa and HTLV-IIb. Recently, studies on HTLV-II infections in Brazil have revealed isolates that are related phylogenetically to the HTLV-IIa subtype but have a HTLV-IIb phenotype with respect to the transactivating protein, tax. To more clearly define this relationship, HTLV-II was isolated from peripheral blood of an IVDA from Sao Paulo, Brazil (SP-WV), and the complete provirus was cloned and sequenced. Comparison of HTLV-IISP-WVnucleotide sequences to other available complete HTLV-II proviral sequences revealed that HTLV-IISP-WVis most closely related to HTLV-IIMo, the prototypic HTLV-IIa subtype sequence. Phylogenetic analysis of LTR, env,and taxregions unequivocally demonstrated that HTLV-IISP-WVand all other Brazilian sequences examined are members of the IIa subtype. The predicted amino acid sequences of the major coding regions of HTLV-IISP-WVare also most closely related to HTLV-IIMo, with the important exception of tax. The tax protein encoded by HTLV-IISP-WVis 96–99% identical to the tax of IIb isolates and is similar in that it has an additional 25 amino acids at the carboxy-terminus compared to the HTLV-IIMotax with which it shares 91% identity. Analysis of tax stop codon usage of a number of HTLV-IIa isolates from North American, Europe, and Brazil demonstrated that isolates from the last region appear to be unique in their extended tax phenotype. It could be demonstrated that the extended tax proteins in the HTLV-IIb and Brazilian isolates had equivalent ability to transactivate the viral LTR, and studies with deletion mutants indicated that the extended C-terminus is not essential for transactivation. In contrast, the HTLV-IIa tax was found to have a greatly diminished ability to transactivate the viral LTR, which appeared to be a consequence of reduced expression of the protein. The studies show that although the Brazilian strains do not represent an entirely new subtype based on nucleotide sequence analysis they are a phenotypically unique molecular variant within the HTLV-IIa subtype.

SARS-CoV-2 uses its spike protein to enter target cells. The spike protein is cleaved by a host protease, and this event facilitates viral entry and broadens cell tropism.

Serological and molecular analyses of a cohort of HIV-1-infected intravenous drug abusers (IVDAs) (n = 103) in Dublin, Ireland have demonstrated that 15 of 103 (14.6%) were infected with HTLV-II, which is the highest infection rate yet recorded for any European country. Restriction fragment length polymorphism (RFLP) analysis of the env region of the provirus demonstrated that the infection involved only the HTLV-IIa subtype; the HTLV-IIb subtype was not detected. Phylogenetic analysis of the nucleotide sequences of the long terminal repeat (LTR) confirmed infection with the HTLV-IIa subtype, and demonstrated that the viruses clustered closely with HTLV-IIa isolates from North American IVDAs. Previous observations that IVDAs in southern Europe, specifically Spain and Italy, appear to be infected predominantly with the HTLV-IIb subtype, along with the present report and evidence that IVDAs in Sweden are infected with the HTLV-IIa subtype, suggest different origins of HTLV-II infection in Europe.

VIROLOGICAL and immunological studies in subacute sclerosing panencephalitis (SSPE) have associated this disease with measles virus1,2. Measles-like virus (referred to as SSPE virus) has been isolated from brain material of patients with SSPE and all SSPE patients reveal an hyperimmune reaction to measles virus antigen. In spite of these major findings the aetiology and pathogenicity of SSPE is still not understood, and the rarity and rural prevalence of this disease remain unexplained3. If measles virus is involved then additional factors either host or virus dependent, must determine the disease since the occurrence of measles virus and its acute infection cannot be correlated with SSPE. So far, no major host factor, either immunological or genetic, has been discovered which would answer these questions4.

In the 10 year period since its discovery, human T cell leukemia virus type II (HTLV-II) has emerged as a significant human pathogen. Infection has been shown to be endemic in a large number of native Indian populations throughout the Americas, and high rates of infection have also been demonstrated in intravenous drug abusers (IVDAs) in both the United States and Europe. While the role of the virus in human disease remains to be clearly defined, there is accumulating evidence that it may be associated with neurological, and perhaps, rare lymphoproliferative disorders. This review summarizes the current status of our understanding of HTLV-II infections, and will emphasize important aspects of the epidemiology of infection, and the molecular and biological properties of the virus. In addition, the salient features of the clinical disorders known to be associated with infection are described.

Summary Atrial natriuretic peptide (ANP), a cardiac hormone, is known to be located in the atrial specific granules, but its presence and localization in the ventricular muscle of the human heart has not been examined fully. Using a specific antibody to human ANP, we studied the conduction system and ventricular muscle with immunohistochemical and ultrastructural methods in 30 hearts obtained at autopsy. These included 12 normal and 18 diseased hearts. In the normal hearts, ANP-positive granules, which were regularly observed in the atrial myocytes, were found in small quantities in the cells of the penetrating and branching bundles in 4 of 12, and in the cells of the ventricular free walls in 2 of the 12 hearts. In the diseased hearts, the positivity increased significantly (P<0.05), being found in 13 of 18 (72.2%) conduction systems and 10 of 18 (55.6%) ventricular muscles. The granules were confirmed to be immunoreactive with ANP by ultrastructural examination. Furthermore, the presence of ANP mRNA in the conduction system as well as in the ventricular myocytes was demonstrated by Northern blot hybridization for which we used the complementary DNA of human ANP. Thus, a small quantity of ANP appears to be synthesized and stored in the conduction system and ventricles of some normal hearts. However, ANP was shown to be present in a larger percentage of the diseased hearts.

The kinetics of thymidine incorporation into fractionated T lymphocytes responding to bacterial superantigens were compared to those of cells activated by phytohemagglutinin (PHA). Evident differences between the kinetics of cell proliferation induced by PHA-P and staphylococcal enterotoxin B (SEB) emerged after Day 4 of culture. PHA-P-induced proliferative responses of peripheral blood mononuclear cells (PBMCs) and fractionated cells were apparent on Day 4 because of the presence of accessory cells in the initial cell suspensions. This gradually diminished in correlation with the decline of accessory cells in the cultures. The SEB-induced cell growth (PBMCs and CD4+cells), however, continued until Day 9 of the culture. This finding suggests the reciprocal usage of MHC class II molecules to present SEB by activated T lymphocytes for superantigen-induced T cell activation and suggests that superantigen-related immune activation may depend in part on the potential of activated T lymphocytes to mediate reciprocal cell-to-cell interactions in the presence of superantigens. The decline observed in the CD8+cell response to SEB and toxic shock syndrome toxin-1 after Day 4 was revived by exogenous recombinant interleukin-2 (rIL-2) supplementation, suggesting that the consequent autocrine or paracrine secretion of IL-2 from the responding cells is essential for subsequent cell proliferation. SEB-induced cell proliferation was significantly suppressed by anti-CD11a (lymphocyte function-associated antigen-1; LFA-1, α-chain) monoclonal antibody, and the inhibitory effect was most obvious in 6-day cultured CD8+lymphocytes. The results suggest that the lymphocyte response associated with the cell-to-cell copresentation of superantigens involves LFA-1 molecules as an accessory factor, particularly in CD8+lymphocytes.

Abstract:  To understand the mechanisms involved in the pathogenesis of human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP), three in vivo phenomena which have been observed in the peripheral blood of patients and differing from that in asymptomatic HTLV-I carriers must be taken into consideration: (a) the presence of increased HTLV-I viral load, (b) a higher immune responsiveness against HTLV-I antigens, and (c) biased nucleotide substitutions in the HTLV-I pX region which indicate a decreased selection pressure for viral amino acid changes. We now propose a hypothesis which focuses on the in vivo dynamics of HTLV-I infected lymphocyte migration and which incorporates these features. In addition, the hypothesis assumes the existence of a deviation in immune surveillance for HTLV-I in the central nervous system (CNS) in spite of the presence of frequent specific immune effectors. We suggest that in the active phase of HAM/TSP, accompanied with or following autoaggressive interactions between infected lymphocytes and immunocompetent cells in the CNS, there is a consequential reflux of the infected lymphocytes to the peripheral blood. The reflux of infected cells would be expected to provide peripheral blood with tissue-derived HTLV-I proviruses which have been indulged and propagated in an immune-privileged site. This process would result in and account for the observed increase in viral load and the substitution bias in HTLV-I sequences in the peripheral blood.

While considerable information is available on the pathogenesis of human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP), fundamental questions remain unanswered. In particular the clinicopathological uniformity of the disorder among patients remains poorly understood. The potential role of TGF-β as a preferential immune regulator in the CNS and the functional heterogeneity of TGF-β has led us to assess the possible involvement of this cytokine in the pathogenic process. To investigate this, the modulatory effects of TGF-β1 on HTLV-I-induced in vitro phenomena were evaluated using fractionated lymphocytes from patients with HAM/TSP. It could be shown that the proliferative response of CD8⁺ cells against cultured and irradiated autologous CD4⁺ cells possessing HTLV-I antigens was significantly inhibited by TGF-β1. However, the in vitro activation of HTLV-I, which was evaluated by spontaneous proliferation of CD4⁺ cells, was unaffected by TGF-βI. The induction of intracytoplasmic HTLV-I antigens in cultured CD4⁺ cells was facilitated by TGF-β1 in a dose-dependent manner. These findings suggest that TGF-β may have a critical role in localized viral activation within the CNS in patients with HAM/TSP. Copyright 1995, 1999 Academic Press

Attempts to estimate the time of origin of human immunodeficiency virus (HIV)‐1 by using phylogenetic analysis are seriously flawed because of the unequal evolutionary rates among different viral lineages. Here, we report a new method of molecular clock analysis, called Site Stripping for Clock Detection (SSCD), which allows selection of nucleotide sites evolving at an equal rate in different lineages. The method was validated on a dataset of patients all infected with hepatitis C virus in 1977 by the same donor, and it was able to date exactly the ‘known’ origin of the infection. Using the same method, we calculated that the origin of HIV‐1 group M radiation was in the 1930s. In addition, we show that the coalescence time of the simian ancestor of HIV‐1 group M and its closest related cpz strains occurred around the end of the XVII century, a date that could be considered the upper limit to the time of simian‐to‐human transmission of HIV‐1 group M. The results show also that SSCD is an easy‐to‐use method of general applicability in molecular evolution to calibrate clock‐like phylogenetic trees.

SUBACUTE sclerosing panencephalitis (SSPE) is a rare, slowly evolving disease of the central nervous system (CNS) which has been associated with measles virus infection. A measles-like virus (SSPE virus) has been isolated from SSPE brain and lymph node material. Also, patients with SSPE show a humoral hyperimmune reaction against measles virus. These findings implicate measles virus as a possible aetiologic agent in this disease; however, they do not explain the pathogenicity of SSPE1,2. Additional factors, either host or virus derived, must have a pathogenetic role, as rarity and rural prevalence of SSPE cannot be correlated to the ubiquitous measles virus infection2. Indeed, biological, ultra-structural and biochemical investigations3–5have indicated minor differences between SSPE and measles virus strains. On the basis of these findings, we have analysed the mRNAs of these viruses from infected cells and compared the antigenic properties of membrane (M) proteins isolated from purified SSPE (leukoencephalitis (LEC) ) viruses with those of measles (Edmonston) viruses. The results presented here show differences among the M proteins as well as the pattern of mRNAs of these viruses. The findings allow differentiation between these viruses and indicate that SSPE viruses are related but not identical to measles virus.

No relevant conflicts of interest to declare.

Adult T cell leukemia (ATL) is a lymphoproliferative disorder caused by infection with HTLV-I. Although various chemotherapies have shown significant complete remission rates, most of the treated patients relapse. These data indicate the existence of leukemic stem cells (LSCs) and a specific niche that regulates stemness and protects LSCs from various chemotherapies.

No relevant conflicts of interest to declare.

Abstract 1877

Human T cell leukemia virus (HTLV) type II is endemic in certain American Indians, and high rates of infection occur in intravenous drug users (IVDUs). North American IVDUs are infected with two distinct variants, HTLV-IIa and -IIb. IfIVDUs became infected as a result ofinteraction with members of an American Indian population, both viral forms should be demonstrable in such populations. Nucleotide sequence analysis of 630 bases of the env gene encoding the gp21 protein was done on DNA from 12 New Mexico Indians (8 Pueblo, 4 Navajo). All samples were typical subtype a or b viruses. Seven of the 8 Pueblo and 2 of 4 Navajo had subtype b; the rest had subtype a. The results are compatible with an indigenous New World origin for both subtypes of HTLV-II.

Blood donors have been screened for antibodies to human T cell lymphotropic virus (HTLV) type I since December 1988. Screening for HTLV-II has been simultaneously done because of cross-reactivity between antibodies to the two viruses. Currently, <1 in 10,000 US blood donors is positive for HTLV-I or -II. Lookback studies led to the identification of6 HTLV-II-infected patients. Three received transfusions before introduction of HTLV-I screening tests, while the other 3 received blood components that tested negative for HTLV-I. The HTLV-II subtypes of each of 4 donor/recipient pairs, as determined by DNA amplification using polymerase chain reaction, were identical, supporting the view that transfusions were the source of infection. In conclusion, currently licensed blood donor screening tests for HTLV-I lack sensitivity for HTLV-II, and transfusion of blood from HTLV-II-infected donors that test negative on HTLVI screening tests may result in infection.