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Novel neplanocin A derivatives have been identified as potent and selective inhibitors of hepatitis B virus (HBV) replication in vitro. These include (1S,2R,5R)-5-(5-bromo-4-methyl-7H-pyrrolo[2,3-d]-pyrimidin-7-yl)-3-(hydroxymethyl)cyclopent-3-ene-1,2-diol (AR-II-04-26) and (1S,2R,5R)-5-(4-amino-3-iodo-1H-pyrazolo[3,4-d]pyrimidin-1-yl)-3-(hydroxylmethyl)cyclopent-3-ene-1,2-diol (MK-III-02-03). The 50% effective concentrations of AR-II-04-26 and MK-III-02-03 were 0.77 ± 0.23 and 0.83 ± 0.36 μM in HepG2.2.15.7 cells, respectively. These compounds reduced intracellular HBV RNA levels in HepG2.2.15.7 cells and infected primary human hepatocytes. Accordingly, they could reduce HBs and HBe antigen production in the culture supernatants, which was not observed with clinically approved anti-HBV nucleosides and nucleotides (reverse transcriptase inhibitors). The neplanocin A derivatives also inhibited HBV RNA derived from cccDNA. In addition, unlike neplanocin A itself, the compounds did not inhibit S-adenosyl-l-homocysteine hydrolase activity. Thus, it appears that the mechanism of action of AR-II-04-26 and MK-III-02-03 differs from that of the clinically approved anti-HBV agents. Although their exact mechanism (target molecule) remains to be elucidated, the novel neplanocin A derivatives are considered promising candidate drugs for inhibition of HBV replication.

We report an AIDS patient with a high HIV RNA copy number in the plasma who was successfully treated for prolonged Mycobacterium avium bacteremia and other complications. An HIV-infected patient with high fever, anemia, high alkaline phosphatase, cystic lung lesions, hepatitis B virus infection and Kaposi's sarcoma was referred to our hospital. PCR of the blood revealed Mycobacterium avium bacteremia and the time to blood culture positivity was 8 days. The HIV-1 RNA copy number in the plasma was more than ten million copies/ml and the CD4-positive T cell count was 21 cells/μL. Although the high fever resolved five days after therapy for Mycobacterium avium was started, the fever recurred just before starting anti-retroviral therapy (ART) including dolutegravir. The patient experienced repeated but self-limiting bouts of severe inflammation. Mycobacteremia was intermittently detected up to 79 days, suggesting that the recurrent episodes of inflammation were due to the intermittent dissemination of mycobacteria, and that persistent treatment is needed. Five months after the beginning of ART, the HIV-1 RNA copy number in the plasma was still 28,000 copies/ml. An HIV drug-resistance test revealed sensitivity to all anti-retroviral drugs. Eleven months after the initiation of ART, the HIV RNA copy number in the plasma decreased to 45 copies/mL and the CD4-positive T cell count recovered to 205 cells/μL. Our case also suggests that dolutegravir can be effective in cases with prolonged high levels of HIV RNA. Our findings emphasize that prompt diagnosis and persistent therapy for mycobacterial infection are important for successful treatment.

Galectin-3 (Gal-3) is involved in many biological processes and pathogenesis of diseases in part through nuclear factor (NF)-κB activation. We demonstrated that Gal-3 expression was significantly induced by tumor necrosis factor (TNF)-α or phorbol 12-myristate 13-acetate in OM-10.1 and ACH-2 cells, which are considered as a model of HIV-1 latently infected cells. The expression of Gal-3 was also associated with their viral production. However, the induction of Gal-3 by TNF-α was not observed in their uninfected parental cells. Knockdown of Gal-3 resulted in the suppression of NF-κB activation and HIV-1 replication in the latently infected cells. The expression level of Gal-3 was highly correlated with that of HIV-1 Tat in the latently infected cells stimulated with TNF-α. Furthermore, colocalization and possible interaction of Gal-3 and Tat were observed in the stimulated cells. These results suggent that Gal-3 expression is closely correlated with HIV-1 expression in latently infected cells through NF-κB activation and the interaction with Tat.

The current antiretroviral therapy cannot cure the patients infected with human immunodeficiency virus type 1 (HIV-1) due to the existence of latently infected cells capable of virus production from harboring proviral DNA. MazF is an ACA nucleotide sequence-specific endoribonuclease derived from Escherichia coli. The conditional expression of MazF by binding of HIV-1 Tat to the promoter region of a MazF-expression vector has previously been shown to selectively inhibit HIV-1 replication in acutely infected cells. The expression of MazF significantly suppressed tumor necrosis factor (TNF)-α-induced HIV-1 production and viral RNA expression in the HIV-1 latently infected cell line OM-10.1 transduced with the MazF-expression vector (OM-10.1/MFR). Moreover, the viability of OM-10.1/MFR cells decreased with increasing concentrations of TNF-α, whereas such decrease was not observed for HL-60 cells transduced with the MazF-expression vector (HL-60/MFR), the uninfected parental cell line of OM-10.1. TNF-α increased the expression of cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase in OM-10.1/MFR cells, indicating that the cell death was caused by the induction of apoptosis. TNF-α-induced expression of MazF mRNA was detected in OM-10.1/MFR but not HL-60/MFR cells, suggesting that TNF-α-induced apoptosis of latently infected cells was due to the expression of MazF. Thus, the anti-HIV-1 gene therapy using the MazF-expression vector may have potential for the cure of HIV-1 infection in combination with suitable latency reversing agents through reducing the size of latently infected cells without viral reactivation.

Background/aim Adult T-cell leukemia (ATL) is a hematological malignancy caused by infection with human T-cell leukemia virus type 1 (HTLV-1). Chemotherapy, antibody therapy, and bone marrow transplantation are used to treat this disease, however, median survival time has not been significantly improved. Our aim was to develop and evaluate a novel antibody-drug conjugate (ADC) with regards to cell cytotoxicity and target specificity. Materials and methods In this study, we have constructed a novel ADC, which is composed of an anti-CD70 single chain Fv-Fc antibody conjugated with the anticancer agent emtansine using a novel antibody modification method. Cell cytotoxicity and target specificity were assessed using a cell proliferation assay. Results The anti-CD70 ADC selectively killed HTLV-1-infected cells and ATL cells without affecting other cells. Conclusion The anti-CD70 ADC offers some chemotherapeutic potential for the treatment of ATL.

Chronic hepatitis B virus (HBV) infection is currently treated with nucleoside/nucleotides analogs. They are potent inhibitors of HBV DNA polymerase, which also functions as reverse transcriptase. Although nucleoside/nucleotide analogs efficiently suppress HBV replication in liver cells, they cannot eradicate HBV DNA from liver cells and cure the disease. Therefore, it is still mandatory to identify and develop effective inhibitors that target a step other than reverse transcription in the viral replication cycle. HBV capsid assembly is a critical step for viral replication and an attractive target for inhibition of HBV replication. We conducted in silico screening of compounds expected to bind to the HBV capsid dimer-dimer interaction site. The selected compounds were further examined for their anti-HBV activity in vitro. Among the test compounds, novel pyrimidotriazine derivatives were found to be selective inhibitors of HBV replication in HepG2.2.15.7 cells. Among the compounds, 2-[(2,3-dichlorophenyl)amino]-4-(4-tert-butylphenyl)-8-methyl-4H,9H-pyrimido[1,2-a][1,3,5]triazin-6-one was the most active against HBV replication. Studies on its mechanism of action revealed that the compound interfered with HBV capsid assembly determined by a cell-free capsid assembly system. Thus, the pyrimidotriazine derivatives are considered to be potential leads for novel HBV capsid assembly inhibitors.

Background: Hepatitis C virus (HCV) infection became curable because of the development of direct acting antivirals (DAAs). However, the high cost of DAAs has greatly impeded their potential impact on the treatment of HCV infection. As a result, hepatitis C will continue to cause substantial morbidity, and mortality among chronically infected individuals in low and middle income countries. Thus, urgent need exists for developing cheaper drugs available to hepatitis C patients in these countries. Materials and Methods: Alpha-zam, an indigenous herbal formulation from Nigella sativa seed, was examined for its anti-HCV activity and cytotoxicity in genotype 1b HCV replicon cells. The antiviral activity was determined by luciferase expression and viral RNA synthesis, while the cytotoxicity was assessed by viable cell number and glyceraldehyde-3-phosphate dehydrogenase RNA synthesis in the replicon cells. Results: Alpha-zam was found to be a selective inhibitor of HCV replication. The 50% effective dilution and 50% cytotoxic dilution of Alpha-zam were 761- and < 100-fold, respectively, in the subgenomic replicon cells LucNeo#2. Its selective inhibition of HCV was also confirmed by HCV RNA levels in LucNeo#2 and in the full-genome HCV replicon cells NNC#2 using real-time reverse transcriptase polymerase chain reaction. Furthermore, the anti-HCV activity of Alpha-zam was not due to the induction of interferon. Conclusion: Alpha-zam selectively inhibits HCV replication and therefore has potential for a novel antiviral agent against HCV infection.

Background The novel phenanthridinone derivative HA-719 has recently been identified as a highly potent and selective inhibitor of hepatitis C virus replication. To elucidate its mechanism of inhibition, we have isolated and analyzed a clone of hepatitis C virus replicon cells resistant to HA-719. Methods To isolate HA-719-resistant replicon cells, Huh-7 cells containing subgenomic hepatitis C virus replicons (genotype 1b) with a luciferase reporter (LucNeo#2) were cultured in the presence of G418 and escalating concentrations of HA-719. After several passages, total RNA was extracted from the growing cells, and Huh-7 cells were transfected with the extracted RNA. Limiting dilution of the transfected cells was performed to obtain an HA-719-resistant clone. Results The 50% effective concentration (EC50) of HA-719 for hepatitis C virus replication was 0.058 ± 0.012 µM in LucNeo#2 cells. The replicon cells capable of growing in the presence of G418 and 3 µM HA-719 were obtained after 18 passages (72 days). The HA-719-resistant clone LucNeo719R showed 98.3-fold resistant to the compound (EC50 = 5.66 ± 0.92 µM), but the clone had no cross-resistance to telaprevir (NS3 inhibitor), daclatasvir (NS5A inhibitor), and VX-222 (NS5B inhibitor). The sequence analysis for the wild-type and LucNeo719R identified 3, 2 and 7 mutations in NS3/4 A, NS4B, and NS5A, respectively, but no mutations in NS5B. Conclusion None of the amino acid mutations in the resistant clone corresponds to those reported to confer drug-resistance to current anti-hepatitis C virus agents, suggesting that the target of HA-719 for hepatitis C virus inhibition differs from those of the existing agents.

Changes in the timing of bird migration in spring and autumn in a coastal forest near the city of Niigata, central Honshu, Japan, were analyzed based on 27 years of bird-banding records. Half of the bird species studied, including all migratory types except residents, arrived or departed significantly earlier in spring due to an increase in spring temperatures. The rate of change we observed in spring migration timing due to changes in temperature was identical to or slightly greater than those reported in studies from other countries. The spring arrival of the Narcissus Flycatcher Ficedula narcissina and the Japanese Thrush Turdus cardis, both long-distance summer migrants to the nearby mountains, became earlier (advanced), however, for reasons that remained unclear. Median capture date in autumn was significantly associated with year for five species. Of these, the median capture date of the Japanese White-eye Zosterops japonicus, a resident and wandering bird, and the Black-faced Bunting Emberiza spodocephala, a wandering bird, advanced annually, while for the Japanese Robin Luscinia akahige and two other species (all long-distance migrants), it was delayed. We hypothesize that forest succession from a simple pine forest to a mixed forest with well-developed sub-canopy and shrub layers may have strongly influenced the Japanese White-eye and the Black-faced Bunting due to changes in population structure in the study area, resulting in an earlier median autumn capture date. Forest succession may also have influenced the Japanese Robin's food resources, enabling it to stay longer in the study area and resulting in a delay in autumn departure date. Thus, changes in bird migration timing differ according to different environmental factors in spring and autumn.

Aims Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infectious disease. SFTS is epidemic in Asia, and its fatality rate is around 30% in Japan. The causative virus severe fever with thrombocytopenia syndrome virus (SFTSV) is a phlebovirus of the family Phenuiviridae (the order Bunyavirales). Although effective treatments are required, there are no antiviral agents currently approved for clinical use. Ribavirin and favipiravir were examined for their anti-SFTSV activity and found to be selective inhibitors of SFTSV replication in vitro. However, their activity was not sufficient. Therefore, it is mandatory to identify novel compounds active against SFTSV. To this end, we have established a safe and rapid assay system for screening selective inhibitors of SFTSV. Methods The virus was isolated from SFTS patients treated in Kagoshima University Hospital. Vero cells were infected with SFTSV and incubated in the presence of various concentrations of test compounds. After three days, the cells were examined for their intracellular viral RNA levels by real-time reverse transcription-PCR without extracting viral RNA. The cytotoxicity of test compounds was determined by a tetrazolium dye method. Results Among the test compounds, the antimalarial agent amodiaquine was identified as a selective inhibitor of SFTSV replication. Its 50% effective concentration (EC50) and cytotoxic concentration (CC50) were 19.1 ± 5.1 and >100 µM, respectively. The EC50 value of amodiaquine was comparable to those of ribavirin and favipiravir. Conclusion Amodiaquine is considered to be a promising lead of novel anti-SFTSV agents, and evaluating the anti-SFTSV activity of its derivatives is in progress.

A number of novel phenanthridinone derivatives were examined for their inhibitory effect on hepatitis C virus (HCV) replication in Huh-7 cells harboring self-replicating subgenomic viral RNA replicons with a luciferase reporter (LucNeo#2). The activity of compounds was further confirmed by inhibition of viral RNA copy number in different subgenomic and full-genomic replicon cells using real-time reverse transcription polymerase chain reaction. Among the compounds, 4-butyl-11-(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)-7-methoxy-[1,3]dioxolo[4,5-c]phenanthridin-5(4H)-one (HA-719) was found to be the most active with a 50% effective concentration of 0.063 ± 0.010 μM in LucNeo#2 cells. The compound did not show apparent cytotoxicity to the host cells at concentrations up to 40 μM. Western blot analysis demonstrated that HA-719 reduced the levels of NS3 and NS5A proteins in a dose-dependent fashion in the replicon cells. Interestingly, the phenanthridinone derivatives including HA-719 were less potent inhibitors of JFH1 strain (genobtype 2a HCV) in cell-free virus infection assay. Although biochemical assays revealed that HA-719 proved not to inhibit NS3 protease or NS5B RNA polymerase activity at the concentrations capable of inhibiting viral replication, their molecular target (mechanism of inhibition) remains unknown. Considering the fact that most of the anti-HCV agents currently approved or under clinical trials are protease and polymerase inhibitors, the phenanthridinone derivatives are worth pursuing for their mechanism of action and potential as novel anti-HCV agents.

Several novel γ-carboline derivatives were identified as selective inhibitors of bovine viral diarrhea virus (BVDV) replication in cell cultures. Among them, 3,4,5-trimethyl-γ-carboline (SK3M4M5M) was the most active against BVDV (Nose strain) in MDBK cells, with a 50% effective concentration of 0.017 ± 0.005 μM and a selectivity index of 435. The compound inhibited viral RNA synthesis in a dose-dependent fashion. In a time of drug-addition experiment during a single viral replication cycle, SK3M4M5M lost its antiviral activity when first added at 8 h or later after infection, which coincides with the onset of viral RNA synthesis. When selected γ-carboline derivatives, including SK3M4M5M, were examined for their inhibitory effect on the mutant strains resistant to some classes of nonnucleoside BVDV RNA-dependent RNA polymerase inhibitors, all of which target the top of the finger domain of the polymerase, the strains displayed cross-resistance to the γ-carboline derivatives. These results indicate that the γ-carboline derivatives may possibly target a hot spot of the RNA-dependent RNA polymerase. Although SK3M4M5M was highly active against BVDV, the compound proved inactive against hepatitis C virus (HCV) in HCV RNA replicon cells.

Background: A number of compounds were examined for their inhibitory effects on bovine viral diarrhoea virus (BVDV), a surrogate model of hepatitis C virus, in cell cultures. Among them, some diphenylmethane derivatives were found to be selective inhibitors of BVDV. Methods: Determination of compounds for their anti-BVDV activity was based on the inhibition of virus-induced cytopathic effect in Madin–Darby bovine kidney cells and reduction of infectious virus particles in culture supernatants. To gain insight into the mechanism of action, the inhibition of viral entry and RNA synthesis in the host cells was also determined by real-time reverse transcription-PCR. Results: Among the test compounds, four diphenylmethane derivatives significantly inhibited BVDV replication with a 50% effective concentration ranging between 6.3 and 10.8 μM. They were not cytotoxic at concentrations up to 100 μM. The representative compound, SH-595A, reduced the virus titre of culture supernatants in a dose-dependent manner. In addition, the compound appeared to somewhat affect viral entry to the host cells. Although SH-595A was inhibitory to viral RNA synthesis, the inhibition was achieved only at high concentrations and was not comparable to its antiviral activity. Conclusions: The novel diphenylmethane derivatives are effective against BVDV replication and might have a unique mechanism of action.

A phenanthridinone skeleton was derived from our previous researches on thalidomide and retinoids as a multi-template for generation of anti-viral lead compounds. Structural development studies focusing on anti-hepatitis C virus activity afforded 5-butyl-2-(1,1,1,3,3,3-hexafluoro-2-hydroxypropan-2-yl)phenanthridin-6(5H)-one (10) and 5-butylbenzo[b]phenanthridin-6(5H)-one (39), which showed EC(50) values of approximately 3.7 and 3.2microM, respectively.

Background: A number of compounds were examined for their inhibitory effect on bovine viral diarrhoea virus (BVDV) replication in cell cultures and found that some cyclooxygenase (COX) inhibitors had antiviral activity against the virus. Methods: Determination of compounds for their anti-BVDV activity was on the basis of the inhibition of virus-induced cytopathogenicity in Mardin–Darby bovine kidney (MDBK) cells. Anti-hepatitis C virus (HCV) activity was assessed by the inhibition of viral RNA synthesis in the subgenomic HCV RNA replicon cells. Results: Among the test compounds, 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-(trifluoromethyl)-1 H-pyrazole (SC-560) was the most active against BVDV, and its 50% effective and cytotoxic concentrations were 10.9 ±2.8 and 93.9 ±24.5 μM in virus and mock-infected MDBK cells, respectively. The compound also suppressed BVDV RNA synthesis in a dose-dependent fashion. Studies on the mechanism of action revealed that SC-560 did not interfere with viral entry to the host cells. Furthermore, it was assumed that the antiviral activity of SC-560 was not associated with its inhibitory effect on COX. The combination of SC-560 and interferon-α was additive to synergistic in inhibiting BVDV replication. More importantly, the compound proved to be a selective inhibitor of HCV replication. Conclusions: SC-560 and its derivative might have potential as novel antiviral agents against HCV.

Porcine endogenous retrovirus (PERV) is persistently integrated into the host genomic DNA as a provirus and released from a variety of porcine cells. PERV infects a certain range of human cells, which is a major concern in xenotransplantation. Therefore, the use of viral gene expression inhibitors could be envisaged, if they reduce PERV production from porcine organs and minimize viral transmission to human recipients. In the present study, four HIV-1 gene expression inhibitors were examined for their inhibitory effect on PERV replication in porcine cells constitutively producing the virus. Among the compounds, the fluoroquinolone derivative K-37 and the bacterial product EM2487 displayed potent and selective inhibition of PERV replication in the cells mediated by the suppression of viral mRNA synthesis. Thus, retroviral gene expression inhibitors may be able to reduce the risk of PERV transmission.

Human T-lymphotropic virus type 1 (HTLV-1) is the etiologic agent of adult T-cell leukemia (ATL). In Japan, the number of HTLV-1 carriers is estimated to be 1.2 million and more than 700 cases of ATL have been diagnosed every year. Considering the poor prognosis and lack of curative therapy of ATL, it seems mandatory to establish an effective strategy for the treatment of ATL. In this study, we attempted to identify the cell surface molecules that will become suitable targets of antibodies for anti-ATL therapy. The expression levels of approximately 40,000 host genes of three human T-cell lines carrying HTLV-1 genomes were analyzed by oligonucleotide microarray and compared with the expression levels of the genes in an HTLV-1-negative T-cell line. The HTLV-1-carrying T-cell lines used for experiments had totally different expression patterns of viral genome. Among the genes evaluated, the expression levels of 108 genes were found to be enhanced more than 10-fold in all of the T-cell lines examined and 11 of the 108 genes were considered to generate the proteins expressed on the cell surface. In particular, the CD70 gene was upregulated more than 1,000-fold and the enhanced expression of the CD70 molecule was confirmed by laser flow cytometry for various HTLV-1-carrying T-cell lines and primary CD4+T cells isolated from acute-type ATL patients. Such expression was not observed for primary CD4+T cells isolated from healthy donors. Since CD70 expression is strictly restricted in normal tissues, such as highly activated T and B cells, CD70 appears to be a potential target for effective antibody therapy against ATL.

TAK-652, a novel small-molecule chemokine receptor antagonist, is a highly potent and selective inhibitor of CCR5-using (R5) human immunodeficiency virus type 1 (HIV-1) replication in vitro. Since TAK-652 is orally bioavailable and has favorable pharmacokinetic profiles in humans, it is considered a promising candidate for an entry inhibitor of HIV-1. To investigate the resistance to TAK-652, peripheral blood mononuclear cells were infected with the R5 HIV-1 primary isolate KK and passaged in the presence of escalating concentrations of the compound for more than 1 year. After 67 weeks of cultivation, the escape virus emerged even in the presence of a high concentration of TAK-652. This virus displayed more than 200,000-fold resistance to TAK-652 compared with the wild type. The escape virus appeared to have cross-resistance to the structurally related compound TAK-779 but retained full susceptibility to TAK-220, which is from a different class of CCR5 antagonists. Furthermore, the escape virus was unable to use CXCR4 as a coreceptor. Analysis for Env amino acid sequences of escape viruses at certain points of passage revealed that amino acid changes accumulated with an increasing number of passages. Several amino acid changes not only in the V3 region but also in other Env regions seemed to be required for R5 HIV-1 to acquire complete resistance to TAK-652.

Background A new series of 1-aromatic methyl-substituted 3-(3,5-dimethylbenzyl)uracil and N-3,5-dimethylbenzyl-substituted urea derivatives were synthesized and evaluated as non-nucleoside HIV-1 reverse transcriptase inhibitors. Methods A series of new 6-azido and 6-amino derivatives of 1-substituted-3-(3,5-dimethylbenzyl)uracils were synthesized using our previously reported method, and three acyclic derivatives were synthesized from urea. The anti-HIV-1 activities of these compounds were determined based on the inhibition of virus-induced cytopathogenicity in MT-4 cells. The cytotoxicities of the compounds were evaluated using the viability of mock-infected cells. Results Some of these compounds showed good-to-moderate activities against HIV-1 with half maximal effective concentration (EC50) values in the submicromolar or subnanomolar range. Compared with emivirine, compound 6-amino-3-(3,5-dimethylbenzyl)-1-(4-aminobenzyl)uracil showed significant anti-HIV-1 activity with an EC50 value of 10 nM and a high selectivity index of 1923. Preliminary structure–activity relationship studies and molecular modeling analyses were carried out to explore the major interactions between HIV-1 reverse transcriptase and the potent inhibitor 6-amino-3-(3,5-dimethylbenzyl)-1-(4-aminobenzyl)uracil; these results may be important for further development of this class of compounds as anti-HIV-1 agents. Conclusion The excellent activity of 6-amino-3-(3,5-dimethylbenzyl)-1-(4-aminobenzyl)uracil (EC50: 0.010 ± 0.006 µM, SI: >1923) may serve as the basis for conducting further investigations on the behavior of this class of compounds against drug-resistant mutants.

FIT-039 has recently been identified as a novel cyclin-dependent kinase 9 inhibitor with potent antiviral activity against a broad spectrum of DNA viruses, such as herpes simplex virus type 1 (HSV-1) and human cytomegaloviruses. In this study, FIT-039 was examined for its inhibitory effect on human immunodeficiency virus type 1 (HIV-1) replication in chronically infected cells. Its 50% effective concentration was 1.4-2.1μM, irrespective of the cells used for antiviral assays, while its 50% cytotoxic concentration was >20μM, indicating that FIT-039 is a selective inhibitor of HIV-1 replication. FIT-039 also inhibited HIV-1 RNA expression in a dose-dependent fashion. Since previous studies demonstrated that FIT-039 exhibited antiviral efficacy without noticeable adverse effects in HSV-1-infected mice, the compound should be further investigated for its clinical potential against HIV-1 infection.

Brain macrophages/microglia and astrocytes are known to be involved in the pathogenesis of HIV-1-associated dementia (HAD). To clarify their interaction and contribution to the pathogenesis, HIV-1-infected or uninfected macrophages were used as a model of brain macrophages/microglia, and their effects on human astrocytes in vitro were examined. The culture supernatants of HIV-1-infected or uninfected macrophages induced significant astrocyte proliferation, which was annihilated with a neutralizing antibody to stromal cell-derived factor (SDF)-1alpha or a matrix metalloproteinase (MMP) inhibitor. In these astrocytes, CXCR4, MMP, and tissue inhibitors of matrix metalloproteinase mRNA expression and SDF-1alpha production were significantly up-regulated. The supernatants of infected macrophages were always more effective than those of uninfected cells. Moreover, the enhanced production of SDF-1alpha was suppressed by the MMP inhibitor. These results indicate that the activated and HIV-1-infected macrophages can indirectly induce astrocyte proliferation through up-regulating SDF-1alpha and MMP production, which implies a mechanism of astrogliosis in HAD.

Polystyrene nanospheres (NS) were found to be efficiently taken up by murine antigen-presenting cells (APC), especially bone marrow-derived dendritic cells (DC), in vitro and in vivo. The efficiency of NS uptake was not affected by the maturation state of DC. Both immature and mature DC had similar ability to take up NS in a dose- and time-dependent manner. Uptake and intracellular localization of NS was clearly demonstrated by confocal laser microscopy, using NS with fluorescence. DC could efficiently take up ovalbumin (OVA), when loaded on the surface of NS (OVA–NS). Consequently, OVA–NS-pulsed DC activated antigen-specific interferon (IFN)-γ-producing T cells much more strongly than OVA-pulsed DC in vitro. These results suggest that NS can be used as an efficient antigen delivery system to DC for a variety of vaccines, such as an anti-human immunodeficiency virus type 1 vaccine.

Breast cancer resistance protein (BCRP/ABCG2) is a novel member of ATP-binding cassette transporters, which induce multidrug resistance in cancer cells. We previously reported that a high level of BCRP expression in CD4(+) T cells conferred cellular resistance to nucleoside reverse transcriptase inhibitors (NRTIs) of human immunodeficiency virus type 1 (HIV-1). However, this BCRP was found to have a mutation of Arg to Met at position 482 (BCRP(R482M)). The present study demonstrated that the wild-type BCRP (BCRP(WT)) also conferred cellular resistance to NRTIs. MT-4 cells (a CD4(+) T-cell line) highly expressing BCRP(WT) (MT-4/BCRP) were generated and the expression of BCRP(WT) was confirmed by genotypic and phenotypic analyses. Compared to the parental MT-4 cells, MT-4/BCRP cells displayed resistance to zidovudine (AZT) in terms of antiviral activity as well as drug cytotoxicity. In addition, other NRTIs were also less inhibitory to HIV-1 replication in MT-4/BCRP cells than in MT-4 cells. Significant reduction of intracellular AZT accumulation was observed in MT-4/BCRP cells. An analysis for intracellular metabolism of AZT suggested that the resistance was attributed to the increased efflux of AZT and its metabolites in MT-4/BCRP cells. Furthermore, the BCRP-specific inhibitor fumitremorgin C completely restored the reduction of AZT in MT-4/BCRP cells. These results indicate that, like BCRP(R482M), BCRP(WT) also plays an important role in cellular resistance to NRTIs.

Human immunodeficiency virus type 1 (HIV-1)-associated central nervous system disorders, including encephalopathy, often occur in the late stage of HIV-1 infection. Some inflammatory cytokines and HIV-1 antigens released from infected microglia or brain macrophages are considered to play an important role in neuropathogenesis. In this study, an in vitro assay system has been established for the evaluation of neural cell death, which would be predictive of the pathogenesis of neural cell death in vivo. The human neuroblastoma cell line SK-N-SH was differentiated to a neural phenotype with retinoic acid, while the promyelocytic cell line HL-60 and its HIV-1-infected clone OM-10.1 were differentiated to macrophages with phorbol myristate acetate. When neural (differentiated SK-N-SH) cells were cocultured with either uninfected or HIV-1-infected macrophages (differentiated HL-60 or OM-10.1 cells, respectively) for 3–5 days, significant neural cell death was observed in the cells cocultured with infected macrophages. Direct contact with macrophages was not necessary for the induction of neural cell death, since indirect coculture or coculture supernatants could also induce neural cell death. Large amounts of cytokines and chemokines were released in the coculture supernatants. The CXCR4 antagonist AMD3100 and the HIV-1 transcription inhibitor K-37 partially inhibited neural cell death. These results indicate that this system seems to be a useful tool for the evaluation of compounds against HIV-1-induced neural cell death.

Breast cancer resistance protein (BCRP/ABCG2) is a novel member of ATP- binding cassette transporters, which induce multidrug resistance in cancer cells. We found that a high level of BCRP expression in CD4+ T cells conferred cellular resistance to human immunodeficiency virus type-1 (HIV-1) nucleoside reverse transcriptase inhibitors. The cell line MT-4/DOX 500 was established through the long-term culture of MT-4 cells in the presence of doxorubicin (DOX) and had reduced sensitivity to not only DOX but also zidovudine (AZT). MT-4/DOX 500 cells showed reduced intracellular accumulation and retention of DOX and increased ATP-dependent rhodamine 123 efflux. The cells were also resistant to several anticancer agents such as mitoxantrone, 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin, and 7-ethyl-10-hydroxycamptothecin. AZT was 7.5-fold less inhibitory to HIV-1 replication in MT-4/DOX 500 cells than in MT-4 cells. Furthermore, the anti-HIV-1 activity of lamivudine was severely impaired in MT-4/DOX 500 cells. In contrast, the antiviral activity of non-nucleoside reverse transcriptase inhibitors and protease inhibitors was not affected in the cells. MT-4/DOX 500 cells expressed glycosylated BCRP but not P-glycoprotein (ABCB1), multidrug resistance protein 1, 2, or 4 (ABCC1, -2, or -4), or lung resistance-related protein. In addition, the BCRP-specific inhibitor fumitremorgin C completely abolished the resistance of MT-4/DOX 500 cells to AZT as well as to DOX. An analysis for intracellular metabolism of AZT suggests that the resistance is attributed to the increase of ATP-dependent efflux of its metabolites, presumably AZT 5'-monophosphate, in MT-4/DOX 500 cells.

EM2487, a Streptomyces-derived substance, has previously been shown to inhibit HIV-1 replication in both acutely and chronically infected cells. In this study, we found that EM2487 was also a selective inhibitor of human T-lymphotropic virus type I (HTLV-I) replication in persistently infected cells. Its 50% effective concentrations for HTLV-I p19 antigen production were 3.6 and 1.2 μM in MT-2 and MT-4 cells, respectively. However, the compound did not reduce cell proliferation and viability at these concentrations. The 50% cytotoxic concentrations of EM2487 were 30.6 and 5.7 μM in MT-2 and MT-4 cells, respectively. The compound also displayed selective inhibition of HTLV-I production in peripheral blood mononuclear cells obtained from patients with HTLV-I-associated myelopathy/tropical spastic paraparesis. Quantitative reverse transcription PCR analysis revealed that EM2487 selectively suppressed HTLV-I mRNA synthesis in MT-2 cells in a dose-dependent fashion. However, the compound did not inhibit endogenous Tax-induced HTLV-I long terminal repeat-driven reporter gene expression. Furthermore, intracellular Tax accumulation was not suppressed in MT-2 cells exposed to EM2487. These results suggest that the inhibition occurred at the viral transcription level, but it cannot be attributed to the inhibition of the Tax function.

Adult T-cell leukemia (ATL) is caused by infection with human T-cell leukemia virus type-1 (HTLV-1). The tetrahydrotetramethylnaphthalene derivative TMNAA has recently been identified as a selective inhibitor of HTLV-1-infected T-cell lines and adult T-cell leukemia (ATL) cells but not of uninfected T-cell lines and peripheral blood mononuclear cells (PBMCs). In the present study, more than 100 derivatives of TMNAA were synthesized and examined for their inhibitory effects on the proliferation of various T-cell lines and PBMCs. Among the compounds, MN417 is a more potent inhibitor of ATL cells than TMNAA. This compound is a novel phenanthridinone derivative with the tetrahydrotetramethylnaphthalene structure. Interestingly, PN-H and MN314-B, which are also phenanthridinone derivatives but do not have the tetrahydrotetramethylnaphthalene structure, could not distinguish between HTLV-1-infected and uninfected T-cell lines in terms of their anti-proliferative activity. These results suggest that the tetrahydrotetramethylnaphthalene structure is required for the selective inhibition of HTLV-1-infected cells.

Cepharanthine (12- O-methyl cepharanoline) is a plant alkaloid and has been shown to inhibit tumour necrosis factor-α- or phorbol 12-myristate 13-acetate-induced HIV-1 replication in the chronically infected promonocytic cell line, U1. Its mechanism of action is considered to be the inhibition of nuclear factor κB, a potent inducer of HIV-1 gene expression. In this study, we have synthesized 96 derivatives of cepharanoline, including cepharanthine, and examined their inhibitory effects on HIV-1 replication in U1 cells. Among the 12- O-alkyl derivatives, cepharanthine proved to be the most active, and the activity decreased as the length of the alkyl chain increased. All of the 12- O-acyl derivatives were totally inactive, while a few 12- O-carbamoyl derivatives displayed modest activity. Since 12- O-ethyl derivatives were found to be as active as cepharanthine against HIV-1 replication, we further synthesized various 12- O-ethyl derivatives of cepharanoline. Among the derivatives, five proved to be more active inhibitors than cepharanthine, and the most active compound was 12- O-ethylpiperazinyl cepharanoline. The 50% effective concentrations of this compound and cepharanthine were 0.0041 and 0.028 μg/ml (0.0060 and 0.046 μM), respectively.

The beta-chemokine receptor CCR5 is considered to be an attractive target for inhibition of CCR5-using (R5 or macrophage-tropic) HIV-1. However, R5 HIV-1 cannot replicate in CD4+ T cell or monocyte lines because of the lack of CCR5 expression on their surface, which apparently hampers discovery and development of effective CCR5 antagonists against HIV-1 replication. In this study, we have established the CCR5-expressing T cell line MOLT-4/CCR5, highly permissive to the replication of R5 HIV-1. The cells express a considerable amount of CCR5 on their surface. When the cells were infected with the R5 HIV-1 strains Ba-L and JR-FL, the virus-induced cytopathic effect (syncytium formation) was observed, and the cells produced large amounts of HIV-1 p24 antigen in the culture supernatants. The analyses of progeny viruses for their coreceptor use and gp120 V3 nucleotide sequence revealed that they were R5 HIV-1. The parental cell line MOLT-4 was much less susceptible to Ba-L and totally insusceptible to JR-FL. Furthermore, MOLT-4/CCR5 cells could support the replication of an R5 clinical isolate, but MOLT-4 cells could not. When TAK-779, a novel small-molecule nonpeptide CCR5 antagonist, was examined for its inhibitory effect on R5 HIV-1 replication in MOLT-4/CCR5 cells, the compound displayed potent antiviral activity, as demonstrated in peripheral blood mononuclear cells. These results indicate that the established cell line will be an extremely useful tool for experiments with R5 HIV-1.

Human immunodeficiency virus type 1 (HIV-1) is unique in that it encodes its own transcriptional activator Tat, which specifically binds to the viral mRNA sequence TAR (transactivation response) element and activates viral transcription at the step of elongation as well as initiation. We recently reported that fluoroquinoline derivatives inhibited HIV-1 replication most likely by blocking viral transcription. In this report, we investigated the mechanism of action of one such compound 7-(3,4-dehydro-4-phenyl-1-piperidinyl)-1,4-dihydro-6-fluoro-1-methyl-8-trifluoromethyl-4-oxoquinoline-3-carboxylic acid (K-37). We demonstrated that K-37 inhibited not only Tat but also other RNA-dependent transactivators. No effect was observed with DNA-dependent transactivators such as p65 (NF-κB) and Gal4VP16. Moreover, K-37 did not inhibit carboxyl-terminal domain (CTD)-kinase activities of CDK-activating kinase (CAK) and positive transcription elongation factor b (P-TEFb), which are known to be involved in Tat-mediated transactivation at the step of transcriptional elongation. It is suggested that RNA-mediated transactivation may involve a common unknown factor to which K-37 directly interacts. Since K-37 did not appear to block DNA-mediated transactivation and thus did not show strong nonspecific cytotoxicity as reported previously, K-37 and its derivative compounds are considered to be feasible candidates for a novel AIDS therapy.

In a search for effective HIV-1 transcription inhibitors, we have evaluated more than 75,000 compounds for their inhibitory effects on Tat-induced human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR)-driven reporter gene expression and found that EM2487, a novel small-molecule substance produced by a Streptomyces species, is a potent and selective inhibitor of HIV-1 replication in both acutely and chronically infected cells. Its 50% effective concentration for acute HIV-1 infection was 0.27 μM in peripheral blood mononuclear cells (PBMCs), while the 50% cytotoxic concentration for mock-infected PBMCs was 13.3 μM. EM2487 proved inhibitory to a variety of HIV-1 strains and HIV-2 in acutely infected T-cell lines (MOLT-4 and MT-4). The compound could suppress tumor necrosis factor alpha (TNF-α)-induced HIV-1 production in latently infected cells (OM-10.1 and ACH-2) as well as constitutive viral production in chronically infected cells (MOLT-4/III B and U937/III B ) without showing any cytotoxicity. EM2487 did not affect early events of the HIV-1 replication cycle, as determined by proviral DNA synthesis in acutely infected MOLT-4 cells. In contrast, the compound selectively prevented viral mRNA synthesis in OM-10.1 cells, suggesting that HIV-1 inhibition occurs at the transcriptional level. Furthermore, EM2487 did not inhibit TNF-α-induced HIV-1 LTR-driven reporter gene expression but did inhibit that induced by Tat, irrespective of the presence or absence of the nuclear factor κB binding sites in the LTR. These results suggest that the mechanism of action is attributable in part to the inhibition of Tat function.

Interleukin 6 (IL-6) has been reported to upregulate the expression of human immuno-deficiency virus type 1 (HIV-1) in infected monocyte/macrophages. Since IL-6 signal is transduced through the membrane glycoprotein gp130, we investigated the inhibitory effect of anti-gp130 monoclonal antibody (mAb) on IL-6-induced viral expression in monocytic cell lines latently infected with HIV-I. IL-6 significantly induced the expression of HIV-1 in U1 cells, whereas it had no effect in OM-10.1 cells. Flow cytometric analysis revealed that U1 but not OM-10.1 cells expressed gp130 on their surface. The anti-gp130 mAb could inhibit IL-6-induced HIV-1 expression in U1 cells in a dose dependent fashion. These results suggest that blocking the gp130 signal transduction may have therapeutic potential for the treatment of HIV-1 infection.

To get insight into the involvement of tumor necrosis factor-alpha (TNF-alpha) and Fas (CD95) ligand in apoptosis (programmed cell death) of monocyte/macrophages in HIV-1-infected individuals, various T cell and myelomonocytic cell lines, including the HIV-1-infected clones OM-10.1 and U1 cells, were cultured in the presence of either TNF-alpha alone, anti-Fas agonist monoclonal antibody (Fas-mAb) alone, or their combinations. TNF-alpha moderately decreased the viability of myelomonocytic cell lines in a dose-dependent fashion (1-100 ng/ml). Unlike HIV-1-infected T cell lines, the viability of OM-10.1 and U1 cells was not affected by the treatment with Fas-mAb alone at concentrations up to 1,000 ng/ml. However, the viability of OM-10.1 cells further decreased with increasing concentrations of Fas-mAb when exposed simultaneously to TNF-alpha, suggesting that TNF-alpha sensitizes the cells to Fas-mAb-induced cell death. FACScan analysis and DNA gel electrophoresis revealed that the cell death was due to apoptosis. Such an effect of Fas-mAb was not identified in U1 cells. TNF-alpha but not Fas-mAb activated latent HIV-1 in OM-10.1 and U1 cells. Although all myelomonocytic cell lines expressed Fas on their cell surface, TNF-alpha significantly up-regulated the expression of Fas in only OM-10.1 cells. These results indicate that, unlike T cells, HIV-1-infected myelomonocytic cells are generally resistant to the Fas-mediated apoptosis. However, they would become sensitive to the apoptosis if the expression of Fas could be up-regulated by TNF-alpha or other factors.

Gene therapy using a Tat-dependent expression system of MazF, an ACA nucleotide sequence-specific endoribonuclease derived from Escherichia coli, in a retroviral vector appears to be an alternative approach to the treatment of human immunodeficiency virus type 1 (HIV-1) infection. MazF can cleave HIV-1 RNA, since it has more than 240 ACA sequences. Significant inhibition of viral replication, irrespective of HIV-1 strains, was observed in CD4(+) T cells that had been transduced with the MazF-expressing retroviral vector (MazF-T cells). The growth and viability of MazF-T cells were not affected by HIV-1 infection. Interestingly, the infectivity of HIV-1 produced from MazF-T cells was found to be lower than that from control CD4(+) T cells. A long-term culture experiment with HIV-1-infected cells revealed that viral replication was always lower in MazF-T cells than in CD4(+) T cells transduced with or without a control vector for more than 200 days. MazF was expressed and mainly localized in the cytoplasm of the infected cells. Unlike in CD4(+) T cells, the expression level of Tat gradually decreased rather than increased in MazF-T cells after HIV-1 infection. As a consequence, the expression level of MazF appeared to be well regulated and sustained during HIV-1 infection in MazF-T cells. Furthermore, the levels of cellular mRNA were not affected by HIV-1 infection. Thus, the Tat-dependent MazF expression system has great potential for inhibition of HIV-1 replication in vivo without apparent toxicity and may be able to avoid the emergence of resistant strains.

Human immunodeficiency virus type 1 (HIV-1) transcription is essential for viral replication and the only step for viral genome amplification. Cyclin T1 (CycT1) interacts with HIV-1 Tat and transactivation-responsive (TAR) RNA, leading to the activation of viral transcription through the hyperphosphorylation of RNA polymerase II (RNAPII). Thus, the CycT1/Tat/TAR RNA interaction represents a novel target for inhibition of HIV-1 replication. In this study, we conducted in silico screening of compounds targeting the CycT1/Tat/TAR RNA complex and found that two structurally related compounds (C1 and C2) had high docking scores for a model of the complex. These compounds proved inhibitory to HIV-1 replication in tumor necrosis factor alpha-stimulated chronically infected cells. In addition, C3, a derivative of C1 and C2, was found to be a more potent inhibitor of HIV-1 replication in chronically infected cells. C3 also inhibited HIV-1 replication in acutely infected cells. The compound could suppress Tat-mediated HIV-1 long terminal repeat-driven gene expression and phosphorylation of RNAPII through inhibition of Tat binding to CycT1. Furthermore, the docking pose of C3 was defined by analyses for its in silico docking energy and in vitro antiviral activity, which indicates that C3 interacts with Tat-binding amino acids of CycT1. Thus, a series of compounds described herein are novel inhibitors of HIV-1 transcription through inhibition of CycT1/Tat interaction.

We have investigated viral breakthrough during a long-term culture of HIV-1-infected cells with the non-nucleoside reverse transcriptase inhibitors (NNRTIs) 6-benzyl-1-ethoxymethyl-5-isopropyluracil (MKC-442), nevirapine and loviride (alpha-APA). When the compounds were examined for their inhibitory effects on HIV-1 (HE strain) replication in MT-4 cells on day 4 after virus infection, the 50% effective concentrations (EC50) of MKC-442, nevirapine and loviride were 9.4, 98 and 21 nM, respectively. After a 48-day culture period, MKC-442, nevirapine and loviride completely inhibited viral breakthrough at concentrations of 1, 5 and 1 microM, respectively. These concentrations were 50-100-fold higher than their EC50 values. When the cells were treated with either MKC-442 (0.04 and 0.2 microM), nevirapine (0.2 and 1 microM) or loviride (0.04 and 0.2 microM) in combination with AZT (0.005 microM), only the combination of 0.2 microM MKC-442 with 0.005 microM AZT could completely inhibit the breakthrough of HIV-1 after a 68-day culture period. Polymerase chain reaction (PCR) analysis revealed that no proviral DNA was detected in the cells treated with this combination. Except for two combinations (0.04 microM MKC-442 + 0.005 microM AZT and 0.04 microM loviride + 0.005 microM AZT), all of the viruses isolated during combination treatments had various amino acid mutations in their reverse transcriptase (RT). These results indicate that the combination treatment with a relatively high dose of MKC-442 and a low dose of AZT may have potential to suppress the emergence of drug resistance during a long-term treatment in vivo and should be further pursued in HIV-1-infected patients.

The conformations of nitrogen-in-the-ring sugars and their N-alkyl derivatives were studied from 1H NMR analyses, mainly using 3J(H,H) coupling constants and quantitative NOE experiments. No significant difference was seen in the ring conformation of 1-deoxynojirimycin (1), N-methyl-1-deoxynojirimycin (2), and N-butyl-1-deoxynojirimycin (3). However, it was shown that the C6 OH group in 1 is predominantly equatorial to the piperidine ring, while that in 2 or 3 is predominantly axial, and its N-alkyl group is oriented equatorially. In the furanose analogues 1,4-dideoxy-1,4-imino-D-arabinitol (4) and its N-methyl (5) and N-butyl (6) derivatives, the five-membered ring conformation differed significantly by the presence or absence of the N-substituted group and the length of the N-alkyl chain. Compound 3 reduced its inhibitory effect on almost all glycosidases, resulting in an extremely specific inhibitor for processing alpha-glucosidase I since N-alkylation of 1 is known to enhance both the potency and specificity of this enzyme in vitro and in vivo. This preferred (C6 OH axial) conformation in 2 and 3 appears to be responsible for their strong alpha-glucosidase I activity. Compound 4 is a good inhibitor of intestinal alpha-glucohydrolases, alpha-glucosidase II, and Golgi alpha-mannosidases I and II, but its N-alkyl derivatives 5 and 6 markedly decreased inhibitory potential for all enzymes tested. In the case of 2,5-dideoxy-2,5-imino-D-mannitol (DMDP, 7), which is a potent beta-galactosidase inhibitor, its N-methyl (8) and N-butyl (9) derivatives completely lost potency toward beta-galactosidase as well. N-Alkylation of compounds 4 and 7, known well as potent yeast alpha-glucosidase inhibitors, resulted in a serious loss of inhibitory activity toward yeast alpha-glucohydrolases. Activity of these nine analogues against HIV-1 replication was determined, based on the inhibition of virus-induced cytopathogenicity in MT-4 and MOLT-4 cells. Compounds 2 and 3, which are better inhibitors of alpha-glucosidase I than 1, proved active with EC50 values of 69 and 49 micrograms/mL in MT-4 cells and 100 and 37 micrograms/mL in MOLT-4 cells, respectively, while none of the furanose analogues exhibited any inhibitory effects on HIV-1. The change in potency and specificity of bioactivity by N-alkylation of nitrogen-in-the-ring sugars appears to be correlated with their conformational change.

The tetrahydrotetramethylnaphthalene derivative TMNAA has recently been identified as a selective inhibitor of human T-lymphotropic virus type 1 (HTLV-1)-infected T-cell lines and adult T-cell leukemia (ATL) cells but not of uninfected T-cell lines and peripheral blood mononuclear cells (PBMCs). Although the target molecule of TMNAA is still unknown, it does not inhibit nuclear factor-κB (NF-κB) activity. Therefore, TMNAA was examined for its inhibitory effect on the cell proliferation in combination with the NF-κB inhibitor cepharanthine. Synergism was observed for the combination, in inhibiting the proliferation of HTLV-1-infected T-cell lines. Although TMNAA alone did not induce the apoptosis of HTLV-1-infected T-cell lines, it strongly enhanced their apoptosis induced by cepharanthine. Thus, TMNAA may have potential as a therapeutic agent against ATL either alone or in combination with cepharanthine, which is clinically used as an anti-inflammatory drug in Japan.

Adult T-cell leukemia (ATL) is caused by infection with human T-lymphotropic virus type 1 (HTLV-1). A novel tetramethylnaphthalene derivative, TMNAA, selectively inhibited the proliferation of various HTLV-1-infected cells, including ATL cell lines and peripheral blood mononuclear cells (PBMCs) from ATL patients. In contrast, the proliferation of uninfected cell lines and PBMCs from healthy donors was hardly affected by the compound. Cell-cycle analysis revealed that TMNAA increased the population of the G0/G1 phase and reduced that of the S phase in HTLV-1-infected cells. TMNAA was found to suppress the phosphorylation of retinoblastoma protein and the expression of cyclin-dependent kinase 4 in HTLV-1-infected cells. Furthermore, the inhibition of cell proliferation was partially annihilated by removing the compound. These results indicate that TMNAA exerts selective inhibition of HTLV-1-infected cells through a novel mechanism, presumably modulating cell cycle regulatory proteins associated with the G0/G1 phase.

A multi-targeted "hemi-nested" PCR (M-PCR) assay in which the primer pairs derived from the 5' non-coding (5'NC) and the nonstructural protein 3 (NS3) regions of HCV genome were concurrently used for amplification in order to compare the sensitivity and specificity of polymerase chain reaction (PCR) with different primer pairs in detecting hepatitis C virus (HCV) genome. Sera from patients with virus-associated liver diseases were examined for the presence of HCV RNA by the M-PCR method following reverse transcription to cDNA. The amplified products derived from both the 5'NC and the NS3 regions were detected in 28 (70%) of the 40 HCV RNA-positive samples. However, 12 samples (30%) were devoid of the signal of NS3-derived product. Sensitivity tests using serial dilutions of HCV RNA revealed that the 5'NC-derived band was still detectable in the 10(5)-fold diluted sample by the M-PCR method, yet the NS3-derived band could hardly be detected in the 10(4)-fold diluted sample. Thus, as previously demonstrated by a single-targeted "nested" PCR assay, the present study using the M-PCR assay has clearly shown that the 5'NC-derived primers are more sensitive and specific than the NS3-derived primers in detecting HCV RNA.

Several anti-BVDV agents with a polymethylated γ-carboline skeleton were synthesized, and their anti-BVDV activity was evaluated. The most potent antiviral agent, SK3M4M5M (20), was synthesized by Pd-catalyzed Buchwald-Hartwig amination reaction followed by annulation reaction as key steps. The structure-activity relationship was analyzed.

Based on antiviral screening of our diphenylmethane derivatives prepared as steroid substitutes, we identified a 1,1-diphenylcyclobutane analog ( 9 ) and two diethyldiphenylsilane analogs ( 12 and 13 ) as superior lead compounds with potent anti-bovine viral diarrhea virus (BVDV) activity, having 50% effective concentration (EC 50 : based on reduction of BVDV replication-induced cell destruction) and 50% cytotoxic concentration (CC 50 : based on reduction of viable cell number) values of 6.2–8.4 μM and >100 μM, respectively, in Madin–Darby bovine kidney (MDBK) cells infected with BVDV.

In search for effective human immunodeficiency virus type 1 (HIV-1) transcription inhibitors, we have evaluated more than 100,000 compounds for their inhibitory effects on HIV-1 long terminal repeat (LTR)-driven reporter gene expression, and identified a novel naphthalene derivative, JTK-101. This compound could suppress tumour necrosis factor (TNF)-α-induced HIV-1 production in latently infected OM-10.1 cells at nanomolar concentrations. JTK-101 could also potently inhibit constitutive HIV-1 production in MOTL-4/IIIB. However, the antiviral activity of JTK-101 was found to be much weaker in acutely infected cells and the chronically infected cells U937/IIIB cells than in OM-10.1 and MOLT-4/IIIB cells. JTK-101 selectively suppressed TNF-α-induced HIV-1 mRNA synthesis in OM-10.1 cells in a dose-dependent fashion. JTK-101 modestly inhibited TNF-α-induced HIV-1 LTR-driven reporter gene expression, but potently inhibited Tat-induced gene expression. Immunoblot analysis revealed that low-level expression of the Tat cofactors CDK9 and cyclin T1 might contribute to the diminished antiviral activity in U937/IIIB cells. Furthermore, JTK-101 could not inhibit HIV-1 replication in chronically infected monocytes/macrophages, in which CDK9 and cyclin T1 were undetectable. These results suggest that JTK-101 exerts its anti-HIV-1 activity through the inhibition of known or unknown Tat cofactors, presumably CDK9/cyclin T1.

In the search for anti-human T-lymphotropic virus type-I (HTLV-I) compounds, we have evaluated several compounds for their inhibitory effects on HTLV-I replication in cell cultures. Among the test compounds, the fluoroquinolone derivative 7-(3,4-dehydro-4-phenyl-1-piperidinyl)-1,4-dihydro-6-fluoro-1-methyl-8- trifluoromethyl-4-oxoquinoline-3-carboxylic acid (K-37) was found to be a potent and selective inhibitor of HTLV-I replication in persistently infected cells, such as MT-2 and MT-4. When the cells were cultured in the presence of various concentrations of the compound, the 50% effective concentrations of K-37 for HTLV-I p19 antigen production were 0.44 and 0.24 microM in MT-2 and MT-4 cells, respectively. K-37 did not affect the viability and proliferation of these cells at these concentrations, and its 50% cytotoxic concentrations to MT-2 and MT-4 cells were 5.7 and 1.1 microM, respectively. The compound also showed selective inhibition of HTLV-I production in peripheral blood mononuclear cells obtained from patients with HTLV-I-associated myelopathy/tropical spastic paraparesis. Quantitative reverse transcription-polymerase chain reaction analysis revealed that K-37 selectively suppressed viral mRNA synthesis in MT-2 cells in a dose-dependent fashion. Furthermore, K-37 could inhibit the endogenous Tax-induced HTLV-I long terminal repeat (LTR)-driven reporter gene expression in MT-2 cells. Western blot analysis confirmed the reduced expression of Tax in MT-2 cells exposed to K-37. In contrast, when Tax was introduced into cells not infected with HTLV-I with a plasmid under the control of human cytomegalovirus promoter, the compound did not affect Tax-induced HTLV-I LTR-driven reporter gene expression. These results suggest that the inhibition occurred at the level of HTLV-I LTR-driven Tax expression.

RNA helicase A (RHA) has two double-stranded (ds) RNA-binding domains (dsRBD1 and dsRBD2). These domains are conserved with the cis-acting transactivation response element (TAR)-binding protein (TRBP) and dsRNA-activated protein kinase (PKR). TRBP and PKR are involved in the regulation of HIV-1 gene expression through their binding to TAR RNA. This study shows that RHA also plays an important role in TAR-mediated HIV-1 gene expression. Wild-type RHA preferably bound to TAR RNA in vitro and in vivo. Overexpression of wild type RHA strongly enhanced viral mRNA synthesis and virion production as well as HIV-1 long terminal repeat-directed reporter (luciferase) gene expression. Substitution of lysine for glutamate at residue 236 in dsRBD2 (RHA(K236E)) reduced its affinity for TAR RNA and impaired HIV-1 transcriptional activity. These results indicate that TAR RNA is a preferred target of RHA dsRBDs and that RHA enhances HIV-1 transcription in vivo in part through the TAR-binding of RHA.

The search for new small-molecule CCR5 antagonists by high-throughput screening (HTS) of the Takeda chemical library using [(125)I]RANTES and CHO/CCR5 cells led to the discovery of lead compounds (A, B) with a quaternary ammonium or phosphonium moiety, which were synthesized to investigate new MCP-1 receptor antagonists. A series of novel anilide derivatives 1 with a quaternary ammonium moiety were designed, synthesized, and tested for their CCR5 antagonistic activity. Through the optimization of lead compounds, we have found N,N-dimethyl-N-[4-[[[2-(4-methylphenyl)-6, 7-dihydro-5H-benzocyclohepten-8-yl]carbonyl]amino]benzyl]tetrahydr o-2 H-pyran-4-aminium chloride (1r, TAK-779) as a highly potent and selective nonpeptide CCR5 antagonist with a IC(50) value of 1.4 nM in the binding assay. Compound 1r also inhibited the replication of macrophage (M)-tropic HIV-1 (Ba-L strain) in both MAGI-CCR5 cells and PBMCs with EC(50) values of 1.2 and 3.7 nM, respectively. The synthesis and structure-activity relationships of 1r and its related compounds are detailed.

In our extensive screening of anti-HIV-1 agents in chronically infected cell lines, we have found acridone derivatives to be selective inhibitors of HIV-1 replication. Among the acridone derivatives, 1-hydroxy-10-methyl-9,10-dihydroacrid-9-one (RD6-5071) suppressed tumor necrosis factor (TNF)-alpha-induced HIV-1 expression in the latently infected cell line OM-10.1, U1, and ACH-2. Its 50% effective concentration for HIV-1 p24 antigen production was 2.0 microg/ml in OM-10.1 cells, while its 50% cytotoxic concentration was 18 microg/ml. The compound also inhibited phorbol 12-myristate 13-acetate (PMA)-induced HIV-1 expression in these cell lines. Furthermore, RD6-5071 was inhibitory to HIV-1 replication in acutely infected U937 and peripheral blood mononuclear cells. The compound was found to suppress TNF-alpha-induced HIV-1 long terminal repeat-driven gene expression. An inhibition assay for protein kinase C (PKC) revealed that RD6-5071 could reduce the enzyme activity. Furthermore, the compound was a moderate inhibitor of PMA-induced nuclear factor kappaB (NF-kappaB) activation, as determined by a gel mobility shift analysis. These results suggest that the acridone derivatives suppress HIV-1 replication at the transcriptional level primarily through a mechanism of PKC inhibition.