Dose escalation of biologic treatment in patients with moderate-to-severe psoriasis in Japan.

Patients receiving interleukin (IL)-inhibiting biologics for moderate-to-severe psoriasis (PsO) may be treated with escalated doses to optimize outcomes. This study evaluated escalation prevalence in a Japanese claims analysis of patients with PsO diagnosis preceding IL-inhibiting biologic treatment and ≥1 post-induction maintenance claim (index date) with sufficient data availability from January 2014 to May 2022. Patients with non-persistence were excluded. Expected daily dose (EDD) was calculated as the recommended maintenance dose divided by the treatment interval. Dose escalation was defined as ≥2 claims showing a ≥20% increase in the observed average daily dose (ADD) over the EDD (with sensitivities requiring ≥1 claim and ≥30%). Significant differences were tested using multivariable regressions. The study included 982 unique patients treated with brodalumab (BRO; n = 104), guselkumab (GUS; n = 207), ixekizumab (IXE; n = 159), risankizumab (RIS; n = 135), secukinumab (SEC; n = 215) and ustekinumab (UST; n = 196). Within 12 months, dose escalation was observed for all IL-inhibiting biologics other than GUS and RIS: 44.4% for UST, 37.2% for IXE, 3.4% for SEC and 1.4% for BRO. In multivariable-adjusted analyses, odds of dose escalation were significantly lower for all products relative to UST. In sensitivities, escalation was observed for all products except RIS.

Real-World Discontinuation and Switching Patterns for Interleukin-Inhibitor Treatments in Patients with Moderate-to-Severe Psoriasis in Japan.

INTRODUCTION: Patients with moderate-to-severe psoriasis (PsO) treated with interleukin (IL)-inhibitors may require treatment modification to achieve disease control. This study evaluated discontinuation and switching of IL-inhibitors for PsO patients in Japan. METHODS: Japan Medical Data Center claims (1/2005-5/2022) were used to identify patients with PsO diagnosis preceding a first IL-inhibitor claim (index date) with ≥ 6 months of eligibility prior. Treatment switch (claim for another biologic) and discontinuation (gap in care ≥ 150% of the days' supply of the preceding prescription) were assessed up to 24 months following initiation. Censored Kaplan-Meier time-to-event analyses calculated rates, and Cox proportional hazards models estimated hazard ratios (HRs) adjusting for baseline characteristics. RESULTS: The study included 1481 unique patients treated with brodalumab (BRO; n = 159), guselkumab (GUS; n = 360), ixekizumab (IXE; n = 279), risankizumab (RIS; n = 327), secukinumab (SEC; n = 366), tildrakizumab (n = 40; excluded due to limited data), and ustekinumab (UST; n = 262). At 12/24 months, 25.9%/38.6% of patients overall had discontinued their index IL-inhibitor and 13.5%/21.2% had switched to another biologic. Discontinuation at 12/24 months was lowest for RIS (11.2%/17.4%), followed by UST (17.9%/32.2%), IXE (27.0%/37.0%), GUS (29.8%/43.0%), SEC (35.6%/53.8%), and BRO (37.2%/47.2%). Switching showed a similar trend: RIS (5.7%/10.7%), UST (11.2%/19.9%), SEC (14.7%/25.7%), IXE (14.8%/21.5%), GUS (16.9%/23.2%), and BRO (19.7%/26.8%). HRs of discontinuation relative to RIS were 2.07 for UST, 2.59 for IXE, 2.70 for GUS, 3.65 for BRO, and 3.69 for SEC (all P ≤ 0.001). HRs of switching relative to RIS were 2.05 for IXE, 2.45 for GUS, 2.67 for SEC, 2.73 for UST, and 2.77 for BRO (all P ≤ 0.01). CONCLUSION: Treatment modification of IL-inhibitors for PsO was commonly observed and could indicate insufficient disease control and/or incremental economic burden. Discontinuation and switching rates were lowest for RIS regardless of time point and adjustment for patient characteristics.

Switch rates, time-to-switch, and switch patterns of antiretroviral therapy in people living with human immunodeficiency virus in Japan, in a hospital-claim database.

BACKGROUND: Regardless of chronic treatment with antiretroviral therapy (ART), the switching rate for ART regarding anchor drugs has not been articulated in real-world clinical-settings in Japan. We assessed switch rates and time-to-switch of ART regimens according to anchor drug classes (integrase strand transfer inhibitors (INSTI), non-nucleoside reverse transcriptase inhibitors (NNRTI) and protease inhibitors (PI)) and common switching patterns of anchor drug classes in people living with human immunodeficiency virus (HIV) (PLWH) from 2008 to 2016. METHODS: This retrospective, observational study used data of 1694 PLWH drawn from a large-scale medical claims database. The median time-to-switch and switch rates of anchor drug class were estimated by Kaplan-Meier analysis. To estimate 95% confidence intervals for switch rates and median days, the Brookmeyer and Crowley method and Greenwood method were used respectively. The switching patterns were summarized based on the time of switching. The switch rates were compared between two anchor drug classes for each year using log-rank tests. RESULTS: We focused our results on 2011-2016 (n = 1613), during which most ART prescriptions were observed. A total of 268 patients switched anchor drug class from the first to a second regimen. The switch rate constantly increased over four years for NNRTIs (17.8-45.2%) and PIs (16.2-47.6%), with median time-to-switch of 1507 and 1567 days, respectively, while INSTI maintained a low switch rate (2.3-7.6%), precluding median-days calculation. The majority originally treated with NNRTI and PI switched to INSTI regardless of the switching timing after starting the first regimen (< 1 year: 91.7 and 97.5%, respectively, and ≥ 1 year: 100.0 and 97.5%, respectively). The risk of switching anchor drug classes was lower for INSTI than for other anchor drug classes in the first regimen even after adjusting for potential confounding factors. CONCLUSIONS: Patients with an ART regimen including INSTI as an anchor drug class maintained a low switch rate for long durations. The major switching strategies of anchor drug class for secondary treatment were from NNRTI or PI to INSTI. These results suggest that INSTI may be a durable anchor drug class for PLWH on ART although there are limitations inherent to the database.

Long-term tolerability and effectiveness of raltegravir in Japanese patients: Results from post-marketing surveillance.

Antiretroviral agents are approved in Japan based on non-clinical and clinical data reported from overseas. Neither the long-term tolerability nor the effectiveness of raltegravir or other integrase strand transfer inhibitors in Japan is known. This study reports on the long-term tolerability and effectiveness of raltegravir in Japanese clinical practice using data collected through approximately 9 years of post-marketing surveillance. This observational survey used data on human immunodeficiency virus (HIV) infected patients initiated treatment with raltegravir between 2008 and 2017 in the HIV-related drug (HRD) cooperative survey to assess the safety and effectiveness of raltegravir in real world clinical practice. There were totally 1,303 patients prescribed raltegravir across 30 institutions; 1,293 patients and 1,178 patients were included for the safety and effectiveness analyses, respectively. The overall risk of adverse drug reaction was 17.25%, with abnormal hepatic function and hyperlipidaemia (<1.5%) having the highest proportion. Median HIV-1 RNA viral loads rapidly decreased below 40 copies/mL after 3 months of raltegravir use in treatment-naïve patients, and consistently sustained below 40 copies/mL after the start of raltegravir use in treatment-experienced patients. Among the patients who were treated for 7 years, 92.00% (95% CI: 73.97-99.02) maintained HIV-1 RNA viral load below 50 copies/mL. Additionally, CD4+ cell counts exceeded >500 cells/µL in treatment-naïve and treatment-experienced patients after 3 years and 4 years of treatment, respectively. In Japanese HIV patients, long-term treatment with raltegravir is well-tolerated and effective at viral suppression as measured by HIV-1 RNA levels and subsequent change in CD4+ cell counts. Such benefits can be expected for not only treatment-naïve but also treatment-experienced patients.

Robust Enhancement of Lentivirus Production by Promoter Activation.

Lentiviral vectors are a valuable tool to deliver exogenous genes for stable expression in cells. While much progress has been made in processing lentiviral vector-containing culture medium, it remains to be explored how the production of lentiviral vector from producer cells can be increased. We initially found that co-expression of the SPRY domain-containing SOCS box protein 1 (SPSB1) promotes the production of human immunodeficiency virus type 1 (HIV-1) and lentiviral vector with increased expression of the Gag and envelope proteins and activation of the HIV-1 LTR and CMV promoter. The presence of AP-1, NF-κB and CREB/ATF recognition sites in these promoters prompted us to utilize human T-lymphotropic virus type 1 (HTLV-1) Tax for lentiviral vector production because Tax activates all these transcription factors. Co-expression of a small amount of Tax markedly increased both the expression of viral structural proteins in producer cells and release of lentiviral vector particles, resulting in a more than 10-fold enhancement of transduction efficiency. Of note, the Tax protein was not detected in the lentiviral vector particles concentrated by ultracentrifugation, supporting the safety of this preparation. Collectively, these results indicate that promoter activation in producer cells represents a promising approach to preparing high-titer lentiviral vectors.

Suppressor of cytokine signaling 1 counteracts rhesus macaque TRIM5α-induced inhibition of human immunodeficiency virus type-1 production.

Old world monkey TRIM5α is a host factor that restricts human immunodeficiency virus type-1 (HIV-1) infection. Previously, we reported that rhesus macaque TRIM5α (RhTRIM5α) restricts HIV-1 production by inducing degradation of precursor Gag. Since suppressor of cytokine signaling 1 (SOCS1) is known to enhance HIV-1 production by rescuing Gag from lysosomal degradation, we examined if SOCS1 is involved in RhTRIM5α-mediated late restriction. Over-expression of SOCS1 restored HIV-1 production in the presence of RhTRIM5α to a level comparable to that in the absence of RhTRIM5α in terms of titer and viral protein expression. Co-immunoprecipitation studies revealed that SOCS1 physically interacted with RhTRIM5α. Over-expression of SOCS1 affected RhTRIM5α expression in a dose-dependent manner, which was not reversed by proteasome inhibitors. In addition, SOCS1 and RhTRIM5α were detected in virus-like particles. These results suggest that SOCS1 alleviates RhTRIM5α-mediated regulation in the late phase of HIV-1 life cycle probably due to the destabilization of RhTRIM5α.

A carboxy-terminally truncated human CPSF6 lacking residues encoded by exon 6 inhibits HIV-1 cDNA synthesis and promotes capsid disassembly.

Since HIV-1 replication is modulated at multiple stages by host cell factors, identification and characterization of those host cell factors are expected to contribute to the development of novel anti-HIV therapeutics. Previous studies showed that a C-terminally truncated cytosolic form of cleavage and polyadenylation-specific factor 6 (CPSF6-358) inhibits HIV-1 infection through interference with HIV-1 trafficking to the nucleus. Here we identified and characterized a different configuration of C-terminally truncated human CPSF6 (hCPSF6-375) through cDNA expression cloning coupled with ganciclovir-mediated lethal selection. Notably, hCPSF6-375, but not mouse CPSF6-358 (mCPSF6-358) as previously reported, remarkably interfered with viral cDNA synthesis after HIV-1 infection. Moreover, we found that hCPSF6-375 aberrantly accelerated the disassembly of the viral capsid in target cells, while CPSF6-358 did not. Sequence comparison of CPSF6-375 and CPSF6-358 cDNAs showed a lack of exon 6 and additional coding sequence for 54 amino acid residues in the C terminus of hCPSF6-375. Mutational analyses revealed that the residues encoded by exon 6, but not the C-terminal 54 residues in hCPSF6-375, is responsible for impaired viral cDNA synthesis by hCPSF6-375. This is the first report demonstrating a novel mode of HIV-1 inhibition by truncated forms of CPSF6 that involves rapid capsid disassembly and inhibition of viral cDNA synthesis. These findings could facilitate an increased understanding of viral cDNA synthesis in light of the viral capsid disassembly.

SIV replication in human cells.

Current human immunodeficiency virus type 1 pandemic is believed to originate from cross-species transmission of simian immunodeficiency virus (SIV) into human population. Such cross-species transmission, however, is not efficient in general, because viral replication is modulated by host cell factors, with the species-specificity of these factors affecting viral tropism. An understanding of those host cell factors that affect viral replication contributes to elucidation of the mechanism for determination of viral tropism. This review will focus an anti-viral effect of ApoB mRNA editing catalytic subunit, tripartite motif protein 5 alpha, and cyclophilins on SIV replication and provide insight into the mechanism of species-specific barriers against viral infection in human cells. It will then present our current understanding of the mechanism that may explain zoonotic transmission of retroviruses.

Molecular and enzymatic characterization of XMRV protease by a cell-free proteolytic analysis.

Xenotropic murine leukemia virus-related virus (XMRV) is a virus generated under artificial conditions by the recombination of 2 murine leukemia virus (MLV) proviruses, PreXMRV-1 and PreXMRV-2, during the in vivo passage of human prostate cancer cells in athymic nude mice. The molecular etiology of XMRV infection has not been characterized and its implication in human prostate cancer progression remains equivocal. As a step toward resolving this issue we developed an in vitro enzymatic assay system to characterize XMRV protease (PR)-mediated cleavage of host-cell proteins. Enzymatically-active XMRV PR protein was synthesized using a wheat-germ cell-free system. By monitoring cleavage activity of XMRV PR by AlphaScreen and 2-color immunoblot analyses, we revealed that the catalytic activity of XMRV PR is selectively blocked by the HIV PR inhibitor, Amprenavir, and identified several human tumor suppressor proteins, including PTEN and BAX, to be substrates of XMRV PR. This system may provide an attractive means for analyzing the function of retrovirus proteases and provide a technology platform for drug screening.

No association of xenotropic murine leukemia virus-related virus with prostate cancer or chronic fatigue syndrome in Japan.

BACKGROUND: The involvement of xenotropic murine leukemia virus-related virus (XMRV) in prostate cancer (PC) and chronic fatigue syndrome (CFS) is disputed as its reported prevalence ranges from 0% to 25% in PC cases and from 0% to more than 80% in CFS cases. To evaluate the risk of XMRV infection during blood transfusion in Japan, we screened three populations--healthy donors (n = 500), patients with PC (n = 67), and patients with CFS (n = 100)--for antibodies against XMRV proteins in freshly collected blood samples. We also examined blood samples of viral antibody-positive patients with PC and all (both antibody-positive and antibody-negative) patients with CFS for XMRV DNA. RESULTS: Antibody screening by immunoblot analysis showed that a fraction of the cases (1.6-3.0%) possessed anti-Gag antibodies regardless of their gender or disease condition. Most of these antibodies were highly specific to XMRV Gag capsid protein, but none of the individuals in the three tested populations retained strong antibody responses to multiple XMRV proteins. In the viral antibody-positive PC patients, we occasionally detected XMRV genes in plasma and peripheral blood mononuclear cells but failed to isolate an infectious or full-length XMRV. Further, all CFS patients tested negative for XMRV DNA in peripheral blood mononuclear cells. CONCLUSION: Our data show no solid evidence of XMRV infection in any of the three populations tested, implying that there is no association between the onset of PC or CFS and XMRV infection in Japan. However, the lack of adequate human specimens as a positive control in Ab screening and the limited sample size do not allow us to draw a firm conclusion.

The antiviral spectra of TRIM5α orthologues and human TRIM family proteins against lentiviral production.

BACKGROUND: Rhesus monkey TRIM5α (TRIM5αrh) recognizes the incoming HIV-1 core through its C-terminal B30.2(PRYSPRY) domain and promotes its premature disassembly or degradation before reverse transcription. Previously, we have shown that TRIM5αrh blocks HIV-1 production through the N-terminal RBCC domain by the recognition of Gag polyproteins. Although all TRIM family proteins have RBCC domains, it remains elusive whether they possess similar late-restriction activities. METHODOLOGY/PRINCIPAL FINDINGS: We examined the antiviral spectra of TRIM5α orthologues and human TRIM family members which have a genetic locus proximal to human TRIM5α (TRIM5αhu), against primate lentiviral production. When HIV-1 virus-like particles (VLPs) were generated in the presence of TRIM5α proteins, rhesus, African green and cynomolgus monkey TRIM5α (TRIM5αag and TRIM5αcy), but not TRIM5αhu, were efficiently incorporated into VLPs, suggesting an interaction between HIV-1 Gag and TRIM5α proteins. TRIM5αrh potently restricted the viral production of HIV-1 groups M and O and HIV-2, but not simian lentiviruses including SIV(MAC)1A11, SIV(AGM)Tan-1 or SIV(AGM)SAB-1. TRIM5αhu did not show notable late restriction activities against these lentiviruses. TRIM5αag and TRIM5αcy showed intermediate restriction phenotypes against HIV-1 and HIV-2, but showed no restriction activity against SIV production. A series of chimeric TRIM5α constructs indicated that the N-terminal region of TRIM5αag and TRIM5αcy are essential for the late restriction activity, while the C-terminal region of TRIM5αcy negatively regulates the late restriction activity against HIV-1. When select human TRIM family proteins were examined, TRIM21 and 22 were efficiently incorporated into HIV-1 VLPs, while only TRIM22 reduced HIV-1 titers up to 5-fold. The antiviral activities and encapsidation efficiencies did not correlate with their relative expression levels in the producer cells. CONCLUSIONS/SIGNIFICANCE: Our results demonstrated the variations in the late restriction activities among closely related TRIM5α orthologues and a subset of human TRIM family proteins, providing further insights into the late restriction activities of TRIM proteins.

Cytoplasmic body component TRIM5{alpha} requires lipid-enriched microdomains for efficient HIV-1 restriction.

TRIM5α is a member of the tripartite motif (TRIM) family of proteins and affects both early and late phases of the retroviral life cycle. Although TRIM5α multimerizes to form cytoplasmic bodies, which are thought to play an important role in viral restriction, the identity of TRIM5α-containing cytoplasmic bodies remains elusive. To better understand TRIM5α cytoplasmic body constituents and the cellular proteins that could be involved in the TRIM5α-mediated antiviral activities, we sought TRIM5α-binding factors. We identified a lipid microdomain protein flotillin-1/Reggie-2 as an interacting partner of TRIM5α via co-immunoprecipitation. Immunohistochemistry studies confirmed the co-localization of rhesus monkey TRIM5α (TRIM5αrh) cytoplasmic bodies with flotillin-1/Reggie-2. Caveolin-1, another lipid microdomain-associated protein, also co-localized with TRIM5α cytoplasmic bodies. Intriguingly, disruption of cellular cholesterol by cyclodextrin perturbed TRIM5α cytoplasmic body formation. Furthermore, lipid starvation partially relieved the endogenous post-entry restriction of HIV-1 infection, which could be subsequently restored by lipid repletion. These observations indicate the involvement of cellular lipids in TRIM5α-mediated antiviral activities. Given that many viruses utilize cellular lipid microdomains for viral entry and assembly, it is plausible that lipid-enriched domains provide microenvironments where TRIM5α recognizes retroviral components.

Determinants for the rhesus monkey TRIM5alpha-mediated block of the late phase of HIV-1 replication.

Rhesus monkey TRIM5alpha (TRIM5alpharh) includes RING, B-box, coiled-coil, and B30.2(PRYSPRY) domains and blocks HIV-1 infection by targeting HIV-1 core through a B30.2(PRYSPRY) domain. Previously, we reported that TRIM5alpharh also blocks HIV-1 production in a B30.2(PRYSPRY)-independent manner. Efficient encapsidation of TRIM5alpharh, but not human TRIM5alpha (TRIM5alphahu), in HIV-1 virus-like particles suggests the interaction between Gag and TRIM5alpharh during viral assembly. Here, we determined responsible regions for late restriction activity of TRIM5alpharh. The RING disruption, but not the replacement with human TRIM21 RING, ablated the efficient encapsidation and the late restriction, suggesting that a RING structure was essential for the late restriction and efficient interaction with HIV-1 Gag. The prominent cytoplasmic body formation of TRIM5alpharh, which depended on the coiled-coil domain and the ensuing linker 2 region, was not required for the encapsidation. Intriguingly, TRIM5alpharh coiled-coil domain mutants (M133T and/or T146A) showed impaired late restriction activity, despite the efficient encapsidation and cytoplasmic body formation. Our results suggest that the TRIM5alpharh-mediated late restriction involves at least two distinct activities as follows: (i) interaction with HIV-1 Gag polyprotein through the N-terminal, RING, and B-box 2 regions of a TRIM5alpharh monomer, and (ii) an effector function(s) that depends upon the coiled-coil and linker 2 domains of TRIM5alpharh. We speculate that the TRIM5alpharh coiled-coil region recruits additional factor(s), such as other TRIM family proteins or a cellular protease, during the late restriction. RBCC domains of TRIM family proteins may play a role in sensing newly synthesized viral proteins as a part of innate immunity against viral infection.

Xenotropic murine leukemia virus-related virus is susceptible to AZT.

The xenotropic murine leukemia virus-related virus (XMRV) is a human retrovirus, recently isolated from tissues of prostate cancer patients with impaired RNase L activity. In this study, we evaluated 10 licensed anti-HIV-1 compounds for their activity against XMRV, including protease inhibitors (PI), nucleoside reverse transcriptase (RT) inhibitors (NRTI), non-nucleoside RT inhibitors (NNRTI) and an integrase inhibitor. No PI affected XMRV production; even high concentrations of Ritonavir failed to inhibit the maturation of XMRV Gag polyproteins. Among the NRTI, NNRTI and integrase inhibitors used in this study, only AZT blocked XMRV infection and replication through inhibition of viral reverse transcription. This sensitivity of XMRV to AZT may be explained by the modest homology in the motif D sequences of HIV-1 and XMRV reverse transcriptases. If XMRV becomes established as an etiological agent for prostate cancer or other diseases, AZT may be useful for preventing or treating XMRV infections in humans.

Alpha interferon enhances TRIM5alpha-mediated antiviral activities in human and rhesus monkey cells.

Dominant, constitutively expressed antiretroviral factors, including TRIM5alpha and APOBEC3 proteins, are distinguished from the conventional innate immune systems and are classified as intrinsic immunity factors. Here, we demonstrate that interferon alpha (IFN-alpha) treatment upregulates TRIM5alpha mRNA in rhesus monkey cells, which correlates with the enhanced TRIM5alpha-mediated pre- and postintegration blocks of human immunodeficiency virus replication. In human cells, IFN-alpha increases the levels of TRIM5alpha mRNA, resulting in enhanced antiviral activity against N-tropic murine leukemia virus infection. These observations indicate that the TRIM5alpha-mediated antiviral effects can be orchestrated by the conventional innate immune response. It is conceivable that TRIM5alpha plays an essential role in controlling both the initial retroviral exposure and the subsequent viral dissemination in vivo.

The RAS/Raf1/MEK/ERK signaling pathway facilitates VSV-mediated oncolysis: implication for the defective interferon response in cancer cells.

Vesicular stomatitis virus (VSV) can replicate in malignant cells more efficiently than in normal cells. Although the selective replication appears to be caused by defects in the interferon (IFN) system in malignant cells, the mechanisms which render these cells less responsive to IFN remain poorly understood. Here we present evidence that an activated RAS/Raf1/MEK/ERK pathway plays a critical role in the defects. NIH 3T3 or human primary cells stably expressing active RAS or Raf1 were rapidly killed by VSV. Although IFNalpha treatment no longer protected the RAS- or Raf1-overexpressing cells from VSV infection, responsiveness to IFNalpha was restored following treatment with the mitogen-activated protein kinase kinase (MEK) inhibitor U0126. Similarly, human cancer-derived cell lines became more responsive to IFNalpha in conjunction with U0126 treatment. Intriguingly, dual treatment with both IFNalpha and U0126 severely reduced the levels of viral RNAs in the infected cells. Moreover, cancer cells showed defects in inducing an IFNalpha-responsive factor, MxA, which is known to block VSV RNA synthesis, and U0126 restored the MxA expression. Our observations suggest that activation of the extracellular signal-regulated protein kinase (ERK) signaling leads to the defect in IFNalpha-mediated upregulation of MxA protein, which facilitates VSV oncolysis. In view of the fact that 30% of all cancers have constitutive activation of the RAS/Raf1/MEK/ERK pathway, VSV would be an ideal oncolytic virus for targeting such cancers.

Rhesus monkey TRIM5alpha restricts HIV-1 production through rapid degradation of viral Gag polyproteins.

Mammalian cells have developed diverse strategies to restrict retroviral infection. Retroviruses have therefore evolved to counteract such restriction factors, in order to colonize their hosts. Tripartite motif-containing 5 isoform-alpha (TRIM5alpha) protein from rhesus monkey (TRIM5alpharh) restricts human immunodeficiency virus type 1 (HIV-1) infection at a postentry, preintegration stage in the viral life cycle, by recognizing the incoming capsid and promoting its premature disassembly. TRIM5alpha comprises an RBCC (RING, B-box 2 and coiled-coil motifs) domain and a B30.2(SPRY) domain. Sequences in the B30.2(SPRY) domain dictate the potency and specificity of the restriction. As TRIM5alpharh targets incoming mature HIV-1 capsid, but not precursor Gag, it was assumed that TRIM5alpharh did not affect HIV-1 production. Here we provide evidence that TRIM5alpharh, but not its human ortholog (TRIM5alphahu), blocks HIV-1 production through rapid degradation of HIV-1 Gag polyproteins. The specificity for this restriction is determined by sequences in the RBCC domain. Our observations suggest that TRIM5alpharh interacts with HIV-1 Gag during or before Gag assembly through a mechanism distinct from the well-characterized postentry restriction. This finding demonstrates a cellular factor blocking HIV-1 production by actively degrading a viral protein. Further understanding of this previously unknown restriction mechanism may reveal new targets for future anti-HIV-1 therapy.

Cyclosporine increases human immunodeficiency virus type 1 vector transduction of primary mouse cells.

Murine primary cells are poorly permissive to human immunodeficiency virus type 1 (HIV-1) vector infection. Retroviral infectivity is influenced by dominant inhibitors such as TRIM5alpha. Sensitivity to TRIM5alpha is altered by interactions between cyclophilin A and the HIV-1 capsid. Here we demonstrate that competitive inhibitors of cyclophilins, cyclosporine or the related Debio-025, stimulate HIV-1 vector transduction of primary murine cells, including bone marrow and macrophages, up to 20-fold. Unexpectedly, the infectivity of an HIV-1 mutant or a simian lentivirus that does not recruit cyclophilin A is also stimulated by these drugs. We propose that cyclosporine and related compounds will be useful tools for experimental infection of murine primary cells. It is possible that HIV-1 infection of murine cells is inhibited by dominant factors related to immunophilins.

Inhibitory and enhancing effects of insertion of central polypurine tract sequence on gene expression with vectors derived from human immunodeficiency virus type 1.

Reportedly, in human immunodeficiency virus type 1 (HIV) vectors, insertion of central polypurine tract (cPPT) increased expression of transgenes for a short period. To test this for a stable condition, we constructed a series of vectors carrying a Neo(r) gene as a stable marker driven by a synthetic thymidine kinase (hTK) promoter. Transduction efficiency was increased in about 2-fold and decreased in about 8-fold by insertion of the reported 178bp and our 282bp cPPTs, respectively. PCR analyses revealed that insertion of 282bp cPPT, but not 178bp cPPT, impaired integration, although it did not deteriorate nuclear transport much. Furthermore, we found that insertion of 282bp cPPT between hTK promoter and an upstream LTR sequence reduced reporter gene activity in about 5-fold. This inhibitory effect of 282bp cPPT may partly account for the observed decrease in transduction efficiency. We suggest that actual effect of cPPT insertion should be examined in each HIV vector.

Chromatin remodeling factor encoded by ini1 induces G1 arrest and apoptosis in ini1-deficient cells.

Ini1/hsnf5 gene encodes INI1 protein, a chromatin remodeling factor associated with the SWI/SNF complex. In yeast, this complex modifies chromatin condensation to coactivate various transcriptional factors. However, in human, little is known about the SWI/SNF complex and INI1. To elucidate cellular functions of ini1, we constructed a recombinant adenovirus (AdexHA-INI1) capable of overexpressing INI1 in ini1-deficient cells. AdexHA-INI1 produced intranuclear INI1 in three ini1-deficient cell lines, changed their morphology, and decreased the proportion of viable cells. Flow cytometry and a BrdU incorporation assay showed that after the infection, growth of these cells was partially arrested at G1. In two of the three ini1-deficient cell lines, apoptosis was found to occur after the infection, as detected by the presence of cleaved poly (ADP-ribose) polymerase. To determine functional domains of INI1, we constructed plasmids expressing INI1 and its deletion mutants, which were used for a colony formation assay. Repeats 1 and 2 of INI1 were found to be required to suppress the growth of the three ini1-deficient cell lines. The results support the hypothesis that ini1 is a tumor suppressor gene and suggest a novel link between human SWI/SNF chromatin remodeling complex and apoptosis.