Single-step conversion of cells to retrovirus vector producers with herpes simplex virus-Epstein-Barr virus hybrid amplicons

Proteomic analysis of non-muscle invasive and muscle invasive bladder cancer highlights distinct subgroups with metabolic, matrisomal, and immune hallmarks and emphasizes importance of the stromal compartment

We present the proteomic profiling of 79 bladder cancers, including treatment-naïve non-muscle-invasive bladder cancer (NMIBC, n = 17), muscle-invasive bladder cancer (MIBC, n = 51), and neoadjuvant-treated MIBC (n = 11). Proteins were extracted from formalin-fixed, paraffin-embedded samples and analyzed using data-independent acquisition, yielding >8,000 quantified proteins. MIBC, compared to NMIBC, shows an extracellular matrix (ECM) and immune response signature as well as alteration of the metabolic proteome together with concomitant depletion of proteins involved in cell-cell adhesion and lipid metabolism. Neoadjuvant treatment did not consistently impact the proteome of the residual tumor mass. NMIBC presents two proteomic subgroups that correlate with histological grade and feature signatures of cell adhesion or lipid/DNA metabolism. Treatment-naïve MIBC presents three proteomic subgroups with resemblance to the basal-squamous, stroma-rich, or luminal subtypes and signatures of metabolism, immune functionality, or ECM. The metabolic subgroup presents an immune-depleted microenvironment, whereas the ECM and immune subgroups are enriched for markers of M2-like tumor-associated macrophages and dendritic cells. Markers for natural killer cells are exclusive for the ECM subgroup, and markers for cytotoxic T cells are a hallmark of the immune subgroup. Endogenous proteolysis is increased in MIBC alongside upregulation of matrix metalloproteases, including MMP-14. Genomic panel sequencing yielded the prototypical profile of prevalent FGRF3 alterations in NMIBC and TP53 alterations in MIBC. Tumor-stroma interactions of MIBC were investigated by proteomic analysis of patient-derived xenografts, highlighting specific tumor and stroma contributions to the matrisome and tumor-induced stromal proteome phenotypes. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Whole-transcriptome analysis of longissimus dorsi muscle in cattle-yaks reveals the regulatory functions of ADAMTS6 gene in myoblasts

Cattle-yak, which is the hybrid F1 generation of cattle and yak, demonstrates better production performance compared to yak. However, there is limited research on the molecular mechanisms responsible for the muscle development of cattle-yak. To address this knowledge gap, a comprehensive transcriptomic survey of the longissimus dorsi muscle in cattle-yak was conducted. Three transcript types, namely lncRNAs, miRNAs, and circRNAs, along with protein-coding genes were characterized at two developmental stages (6 m, 18 m) of cattle-yak. The results revealed significant enrichment of these transcripts into pathways related to myoblast differentiation and muscle development signaling. Additionally, the study identified the TCONS00024465/circHIPK3-bta-miR-499-ADAMTS6 regulatory network, which may play a crucial role in the muscle development of cattle-yak by combining the transcriptome data of yak and constructing the ceRNA co-expression network. HEK 293 T cells were used to validate that TCONS00024465 and circHIPK3 are located upstream of bta-miR-499, and can competitively bind to bta-miR-499 as ceRNA. The study also verified that ADAMTS6 regulates skeletal muscle development by inhibiting myoblast proliferation, promoting myoblast differentiation, and positively regulating the apoptosis of myoblasts. Taken together, this study provides new insights into the advantages of cattle-yak production performance and offers a molecular basis for further research on muscle development.

HSV-1 Amplicon Vectors as Genetic Vaccines

HSV-1 amplicon vectors have been used as platforms for the generation of genetic vaccines against both DNA and RNA viruses. Mice vaccinated with such vectors encoding structural proteins from both foot-and-mouth disease virus and rotavirus were partially protected from challenge with wild-type virus (D'Antuono et al., Vaccine 28:7363-7372, 2010; Laimbacher et al., Mol Ther 20:1810-1820, 2012; Meier et al., Int J Mol Sci 18:431, 2017), indicating that HSV-1 amplicon vectors are attractive tools for the development of complex and safe genetic vaccines.This chapter describes the preparation and testing of HSV-1 amplicon vectors that encode individual or multiple viral structural proteins from a polycistronic transgene cassette. We further put particular emphasis on generating virus-like particles (VLPs) in vector-infected cells. Expression of viral genes is confirmed by Western blot and immune fluorescence analysis and generation of VLPs in vector-infected cells is demonstrated by electron microscopy. Furthermore, examples on how to analyze the immune response in a mouse model and possible challenge experiments are described.

MiR-142a-3p alleviates Escherichia coli derived lipopolysaccharide-induced acute lung injury by targeting TAB2

Acute lung Injury (ALI) is the clinical syndrome of parenchymal lung disease, leading to an extremely high mortality. The pathogenesis of ALI is suggested to be a consequence of uncontrolled inflammation. Lipopolysaccharide (LPS)-induced ALI mice model is often used for the mechanism. Studies show that TGF-beta activated kinase 1 (MAP3K7) binding protein 1/2 (TAB2) plays a crucial role in LPS-induced inflammation response. Furthermore, microRNA-142a-3p (miR-142a-3p) has been observed to be involved in inflammation-induced disease. Thus, we investigated the role of miR-142a-3p and TAB2 on LPS-induced ALI, which involved the TLR4/TAB2/NF-κB signaling. ALI and normal lung tissues were collected to access the relative expression of pro-inflammatory cytokines and miR-142a-3p. Histopathological examination and Wet to Dry weight ratios of lung tissues were used to access the establishment of ALI models. Raw264.7 cells were transfected with si-TAB2 or miR-142a-3p mimics to elucidate the role of TAB2 or miR-142a-3p in the inflammatory cascade in ALI. Additionally, the relationship between miR-142a-3p and TAB2 was validated by dual-luciferase report system. Our study discovered that miR-142-3p was up-regulated both in LPS-induced ALI mice model and RAW264.7 cells model. MiR-142a-3p mimics group experienced significant decrease in the secretion of pro-inflammatory cytokines as a result of the inhibition of NF-κB signaling pathway. Bioinformatics database showed that the adaptor protein, TAB2, was critical in this pathway and it is the target gene of miR-142a-3p. Their relation was first confirmed by us via dual-luciferase report system. Results of our study demonstrated that miR-142a-3p exerts as a protective role in LPS-induced ALI through down-regulation of NF-κB signaling pathway.

Identifying DNase I hypersensitive sites as driver distal regulatory elements in breast cancer

Efforts to identify driver mutations in cancer have largely focused on genes, whereas non-coding sequences remain relatively unexplored. Here we develop a statistical method based on characteristics known to influence local mutation rate and a series of enrichment filters in order to identify distal regulatory elements harboring putative driver mutations in breast cancer. We identify ten DNase I hypersensitive sites that are significantly mutated in breast cancers and associated with the aberrant expression of neighboring genes. A pan-cancer analysis shows that three of these elements are significantly mutated across multiple cancer types and have mutation densities similar to protein-coding driver genes. Functional characterization of the most highly mutated DNase I hypersensitive sites in breast cancer (using in silico and experimental approaches) confirms that they are regulatory elements and affect the expression of cancer genes. Our study suggests that mutations of regulatory elements in tumors likely play an important role in cancer development.

Cancer driver mutations can occur within noncoding genomic sequences. Here, the authors develop a statistical approach to identify candidate noncoding driver mutations in DNase I hypersensitive sites in breast cancer and experimentally demonstrate they are regulatory elements of known cancer genes.

Cold Atmospheric Plasma Inhibits HIV-1 Replication in Macrophages by Targeting Both the Virus and the Cells

Cold atmospheric plasma (CAP) is a specific type of partially ionized gas that is less than 104°F at the point of application. It was recently shown that CAP can be used for decontamination and sterilization, as well as anti-cancer treatment. Here, we investigated the effects of CAP on HIV-1 replication in monocyte-derived macrophages (MDM). We demonstrate that pre-treatment of MDM with CAP reduced levels of CD4 and CCR5, inhibiting virus-cell fusion, viral reverse transcription and integration. In addition, CAP pre-treatment affected cellular factors required for post-entry events, as replication of VSV-G-pseudotyped HIV-1, which by-passes HIV receptor-mediated fusion at the plasma membrane during entry, was also inhibited. Interestingly, virus particles produced by CAP-treated cells had reduced infectivity, suggesting that the inhibitory effect of CAP extended to the second cycle of infection. These results demonstrate that anti-HIV activity of CAP involves the effects on target cells and the virus, and suggest that CAP may be considered for potential application as an anti-HIV treatment.

Re-visiting the functional Relevance of the highly conserved Serine 40 Residue within HIV-1 p6(Gag)

BACKGROUND

HIV-1 formation is driven by the viral structural polyprotein Gag, which assembles at the plasma membrane into a hexagonal lattice. The C-terminal p6(Gag) domain harbors short peptide motifs, called late domains, which recruit the cellular endosomal sorting complex required for transport and promote HIV-1 abscission from the plasma membrane. Similar to late domain containing proteins of other viruses, HIV-1 p6 is phosphorylated at multiple residues, including a highly conserved serine at position 40. Previously published studies showed that an S40F exchange in p6(Gag) severely affected virus infectivity, while we had reported that mutation of all phosphorylatable residues in p6(Gag) had only minor effects.

FINDINGS

We introduced mutations into p6(Gag) without affecting the overlapping pol reading frame by using an HIV-1 derivative where gag and pol are genetically uncoupled. HIV-1 derivatives with a conservative S40N or a non-conservative S40F exchange were produced. The S40F substitution severely affected virus maturation and infectivity as reported before, while the S40N exchange caused no functional defects and the variant was fully infectious in T-cell lines and primary T-cells.

CONCLUSIONS

An HIV-1 variant carrying a conservative S40N exchange in p6(Gag) is fully functional in tissue culture demonstrating that neither S40 nor its phosphorylation are required for HIV-1 release and maturation. The phenotype of the S40F mutation appears to be caused by the bulky hydrophobic residue introduced into a flexible region.

The nucleocapsid domain of Gag is dispensable for actin incorporation into HIV-1 and for association of viral budding sites with cortical F-actin

Actin and actin-binding proteins are incorporated into HIV-1 particles, and F-actin has been suggested to bind the NC domain in HIV-1 Gag. Furthermore, F-actin has been frequently observed in the vicinity of HIV-1 budding sites by cryo-electron tomography (cET). Filamentous structures emanating from viral buds and suggested to correspond to actin filaments have been observed by atomic force microscopy. To determine whether the NC domain of Gag is required for actin association with viral buds and for actin incorporation into HIV-1, we performed comparative analyses of virus-like particles (VLPs) obtained by expression of wild-type HIV-1 Gag or a Gag variant where the entire NC domain had been replaced by a dimerizing leucine zipper [Gag(LZ)]. The latter protein yielded efficient production of VLPs with near-wild-type assembly kinetics and size and exhibited a regular immature Gag lattice. Typical HIV-1 budding sites were detected by using cET in cells expressing either Gag or Gag(LZ), and no difference was observed regarding the association of buds with the F-actin network. Furthermore, actin was equally incorporated into wild-type HIV-1 and Gag- or Gag(LZ)-derived VLPs, with less actin per particle observed than had been reported previously. Incorporation appeared to correlate with the relative intracellular actin concentration, suggesting an uptake of cytosol rather than a specific recruitment of actin. Thus, the NC domain in HIV-1 Gag does not appear to have a role in actin recruitment or actin incorporation into HIV-1 particles. Importance: HIV-1 particles bud from the plasma membrane, which is lined by a network of actin filaments. Actin was found to interact with the nucleocapsid domain of the viral structural protein Gag and is incorporated in significant amounts into HIV-1 particles, suggesting that it may play an active role in virus release. Using electron microscopy techniques, we previously observed bundles of actin filaments near HIV-1 buds, often seemingly in contact with the Gag layer. Here, we show that this spatial association is observed independently of the proposed actin-binding domain of HIV-1. The absence of this domain also did not affect actin incorporation and had a minor effect on the viral assembly rate. Furthermore, actin was not enriched in the virus compared to the average levels in the respective producing cell. Our data argue against a specific recruitment of actin to HIV-1 budding sites by the nucleocapsid domain of Gag.

HSV-1 amplicon vectors as genetic vaccines

HSV-1 amplicon vectors have been used as platforms for the generation of genetic vaccines against both DNA and RNA viruses. Mice vaccinated with such vectors encoding structural proteins from both foot-and-mouth disease virus and rotavirus were partially protected from challenge with wild-type virus (D'Antuono et al. Vaccine 28: 7363-7372, 2010; Laimbacher et al. Mol Ther 20: 1810-1820, 2012), indicating that HSV-1 amplicon vectors are attractive tools for the development of complex and safe genetic vaccines. This chapter describes the use of HSV-1 amplicon vectors that encode individual or multiple viral structural proteins from a polycistronic transgene cassette in mammalian cells. More precisely, amplicon vectors that encode multiple structural viral proteins support the in situ production of viruslike particles (VLPs) in vector-infected cells. The expression of the viral genes is confirmed by Western blot and immune fluorescence analysis, and the generation of VLPs in vector-infected cells is demonstrated by electron microscopy.

Enhancing production and cytotoxic activity of polymeric soluble FasL-based chimeric proteins by concomitant expression of soluble FasL

Membrane FasL is the natural trigger of Fas-mediated apoptosis. A soluble homotrimeric counterpart (sFasL) also exists which is very weakly active, and needs oligomerization beyond its trimeric state to induce apoptosis. We recently generated a soluble FasL chimera by fusing the immunoglobulin-like domain of the leukemia inhibitory factor receptor gp190 to the extracellular region of human FasL, which enabled spontaneous dodecameric homotypic polymerization of FasL. This polymeric soluble human FasL (pFasL) displayed anti-tumoral activity in vitro and in vivo without systemic cytotoxicity in mouse. In the present work, we focused on the improvement of pFasL, with two complementary objectives. First, we developed more complex pFasL-based chimeras that contained a cell-targeting module. Secondly, we attempted to improve the production and/or the specific activity of pFasL and of the cell-targeting chimeras. We designed two chimeras by fusing to pFasL the extracellular portions of the HLA-A2 molecule or of a human gamma-delta TCR, and analyzed the consequences of co-expressing these molecules or pFasL together with sFasL on their heterotopic cell production. This strategy significantly enhanced the production of pFasL and of the two chimeras, as well as the cytotoxic activity of the two chimeras but not of pFasL. These results provide the proof of concept for an optimization of FasL-based chimeric proteins for a therapeutic use.

HSV-1 as a Model for Emerging Gene Delivery Vehicles

The majority of viral vectors currently used possess modest cargo capability (up to 40 kb) being based on retroviruses, lentiviruses, adenoviruses, and adenoassociated viruses. These vectors have made the most rapid transition from laboratory to clinic because their small genomes have simplified their characterization and modification. However, there is now an increasing need both in research and therapy to complement this repertoire with larger capacity vectors able to deliver multiple transgenes or to encode complex regulatory regions, constructs which can easily span more than 100 kb. Herpes Simplex Virus Type I (HSV-1) is a well-characterized human virus which is able to package about 150 kb of DNA, and several vector systems are currently in development for gene transfer applications, particularly in neurons where other systems have low efficiency. However, to reach the same level of versatility and ease of use as that of smaller genome viral vectors, simple systems for high-titer production must be developed. This paper reviews the major HSV-1 vector systems and analyses the common elements which may be most important to manipulate to achieve this goal.

Gene delivery using helper virus-free HSV-1 amplicon vectors

Herpes simplex virus type 1 (HSV-1)-based amplicon vectors contain only a very small percentage of the 152-kbp viral genome. Consequently, replication and packaging of amplicons depend on helper functions that are provided either by replication-defective mutants of HSV-1 or by replication-competent, but packaging-defective, HSV-1 genomes. Sets of cosmids that overlap and represent the entire HSV-1 genome can form, via homologous recombination, circular replication-competent viral genomes, which give rise to infectious virus progeny. However, if the DNA cleavage/packaging signals are deleted, reconstituted virus genomes are not packageable, but still provide all the helper functions required for the packaging of cotransfected amplicon DNA. The resulting stocks of packaged amplicon vectors are essentially free of contaminating helper virus. This unit describes the cotransfection of amplicon and cosmid or bacterial artificial chromosome (BAC) DNA into 2-2 cells by cationic liposome-mediated transfection and the harvesting of packaged vector particles. Support protocols provide methods for preparing cosmid and BAC DNA and determining the titers of amplicon stocks.

An analysis and validation pipeline for large-scale RNAi-based screens

Large-scale RNAi-based screens are a major technology, but require adequate prioritization and validation of candidate genes from the primary screen. In this work, we performed a large-scale pooled shRNA screen in mouse embryonic stem cells (ESCs) to discover genes associated with oxidative stress resistance and found several candidates. We then developed a bioinformatics pipeline to prioritize these candidates incorporating effect sizes, functional enrichment analysis, interaction networks and gene expression information. To validate candidates, we mixed normal cells with cells expressing the shRNA coupled to a fluorescent protein, which allows control cells to be used as an internal standard, and thus we could detect shRNAs with subtle effects. Although we did not identify genes associated with oxidative stress resistance, as a proof-of-concept of our pipeline we demonstrate a detrimental role of Edd1 silencing in ESC growth. Our methods may be useful for candidate gene prioritization of large-scale RNAi-based screens.

Comprehensive mutational analysis reveals p6Gag phosphorylation to be dispensable for HIV-1 morphogenesis and replication

The structural polyprotein Gag of human immunodeficiency virus type 1 (HIV-1) is necessary and sufficient for formation of virus-like particles. Its C-terminal p6 domain harbors short peptide motifs that facilitate virus release from the plasma membrane and mediate incorporation of the viral Vpr protein. p6 has been shown to be the major viral phosphoprotein in HIV-1-infected cells and virions, but the sites and functional relevance of p6 phosphorylation are not clear. Here, we identified phosphorylation of several serine and threonine residues in p6 in purified virus preparations using mass spectrometry. Mutation of individual candidate phosphoacceptor residues had no detectable effect on virus assembly, release, and infectivity, however, suggesting that phosphorylation of single residues may not be functionally relevant. Therefore, a comprehensive mutational analysis was conducted changing all potentially phosphorylatable amino acids in p6, except for a threonine that is part of an essential peptide motif. To avoid confounding changes in the overlapping pol reading frame, mutagenesis was performed in a provirus with genetically uncoupled gag and pol reading frames. An HIV-1 derivative carrying 12 amino acid changes in its p6 region, abolishing all but one potential phosphoacceptor site, showed no impairment of Gag assembly and virus release and displayed only very subtle deficiencies in viral infectivity in T-cell lines and primary lymphocytes. All mutations were stable over 2 weeks of culture in primary cells. Based on these findings, we conclude that phosphorylation of p6 is dispensable for HIV-1 assembly, release, and infectivity in tissue culture.

An expanded model of HIV cell entry phenotype based on multi-parameter single-cell data

Background

Entry of human immunodeficiency virus type 1 (HIV-1) into the host cell involves interactions between the viral envelope glycoproteins (Env) and the cellular receptor CD4 as well as a coreceptor molecule (most importantly CCR5 or CXCR4). Viral preference for a specific coreceptor (tropism) is in particular determined by the third variable loop (V3) of the Env glycoprotein gp120. The approval and use of a coreceptor antagonist for antiretroviral therapy make detailed understanding of tropism and its accurate prediction from patient derived virus isolates essential. The aim of the present study is the development of an extended description of the HIV entry phenotype reflecting its co-dependence on several key determinants as the basis for a more accurate prediction of HIV-1 entry phenotype from genotypic data.

Results

Here, we established a new protocol of quantitation and computational analysis of the dependence of HIV entry efficiency on receptor and coreceptor cell surface levels as well as viral V3 loop sequence and the presence of two prototypic coreceptor antagonists in varying concentrations. Based on data collected at the single-cell level, we constructed regression models of the HIV-1 entry phenotype integrating the measured determinants. We developed a multivariate phenotype descriptor, termed phenotype vector, which facilitates a more detailed characterization of HIV entry phenotypes than currently used binary tropism classifications. For some of the tested virus variants, the multivariant phenotype vector revealed substantial divergences from existing tropism predictions. We also developed methods for computational prediction of the entry phenotypes based on the V3 sequence and performed an extrapolating calculation of the effectiveness of this computational procedure.

Conclusions

Our study of the HIV cell entry phenotype and the novel multivariate representation developed here contributes to a more detailed understanding of this phenotype and offers potential for future application in the effective administration of entry inhibitors in antiretroviral therapies.

HSV-1 amplicon vectors launch the production of heterologous rotavirus-like particles and induce rotavirus-specific immune responses in mice

Virus-like particles (VLPs) are promising vaccine candidates because they represent viral antigens in the authentic conformation of the virion and are therefore readily recognized by the immune system. As VLPs do not contain genetic material they are safer than attenuated virus vaccines. In this study, herpes simplex virus type 1 (HSV-1) amplicon vectors were constructed to coexpress the rotavirus (RV) structural genes VP2, VP6, and VP7 and were used as platforms to launch the production of RV-like particles (RVLPs) in vector-infected mammalian cells. Despite the observed splicing of VP6 RNA, full-length VP6 protein and RVLPs were efficiently produced. Intramuscular injection of mice with the amplicon vectors as a two-dose regimen without adjuvants resulted in RV-specific humoral immune responses and, most importantly, immunized mice were partially protected at the mucosal level from challenge with live wild-type (wt) RV. This work provides proof of principle for the application of HSV-1 amplicon vectors that mediate the efficient production of heterologous VLPs as genetic vaccines.

Lysine residue at position 22 of the AID protein regulates its class switch activity

BACKGROUND

Activation induced deaminase (AID) mediates class switch recombination and somatic hypermutation of immunoglobulin (Ig) genes in germinal centre B cells. In order to regulate its specific activity and as a means to keep off-target mutations low, several mechanisms have evolved, including binding to specific cofactors, phosphorylation and destabilization of nuclear AID protein. Although ubiquitination at lysine residues of AID is recognized as an essential step in initiating degradation of nuclear AID, any functional relevance of lysine modifications has remained elusive.

METHODOLOGY/PRINCIPAL FINDINGS

Here, we report functional implications of lysine modifications of the human AID protein by generating a panel of lysine to arginine mutants of AID and assessment of their catalytic class switch activity. We found that only mutation of Lys22 to Arg resulted in a significant reduction of class switching to IgG1 in transfected primary mouse B cells. This decrease in activity was neither reflected in reduced hypermutation of Ig genes in AID-mutant transfected DT40 B cell lines nor recapitulated in bacterial deamination assays, pointing to involvement of post-translational modification of Lys22 for AID activity in B cells.

CONCLUSIONS/SIGNIFICANCE

Our results imply that lysine modification may represent a novel level of AID regulation and that Lys22 is important for effective AID activity.

Role of chaperone mediated autophagy (CMA) in the degradation of misfolded N-CoR protein in non-small cell lung cancer (NSCLC) cells

Nuclear receptor co-repressor (N-CoR) plays important role in transcriptional control mediated by several tumor suppressor proteins. Recently, we reported a role of misfolded-conformation dependent loss (MCDL) of N-CoR in the activation of oncogenic survival pathway in acute promyelocytic leukemia (APL). Since N-CoR plays important role in cellular homeostasis in various tissues, therefore, we hypothesized that an APL like MCDL of N-CoR might also be involved in other malignancy. Indeed, our initial screening of N-CoR status in various leukemia and solid tumor cells revealed an APL like MCDL of N-CoR in primary and secondary tumor cells derived from non-small cell lung cancer (NSCLC). The NSCLC cell specific N-CoR loss could be blocked by Kaletra, a clinical grade protease inhibitor and by genistein, an inhibitor of N-CoR misfolding previously characterized by us. The misfolded N-CoR presented in NSCLC cells was linked to the amplification of ER stress and was subjected to degradation by NSCLC cell specific aberrant protease activity. In NSCLC cells, misfolded N-CoR was found to be associated with Hsc70, a molecular chaperone involved in chaperone mediated autophagy (CMA). Genetic and chemical inhibition of Lamp2A, a rate limiting factor of CMA, significantly blocked the loss of N-CoR in NSCLC cells, suggesting a crucial role of CMA in N-CoR degradation. These findings identify an important role of CMA-induced degradation of misfolded N-CoR in the neutralization of ER stress and suggest a possible role of misfolded N-CoR protein in the activation of oncogenic survival pathway in NSCLC cells.

A SNAP-tagged derivative of HIV-1--a versatile tool to study virus-cell interactions

Fluorescently labeled human immunodeficiency virus (HIV) derivatives, combined with the use of advanced fluorescence microscopy techniques, allow the direct visualization of dynamic events and individual steps in the viral life cycle. HIV proteins tagged with fluorescent proteins (FPs) have been successfully used for live-cell imaging analyses of HIV-cell interactions. However, FPs display limitations with respect to their physicochemical properties, and their maturation kinetics. Furthermore, several independent FP-tagged constructs have to be cloned and characterized in order to obtain spectral variations suitable for multi-color imaging setups. In contrast, the so-called SNAP-tag represents a genetically encoded non-fluorescent tag which mediates specific covalent coupling to fluorescent substrate molecules in a self-labeling reaction. Fusion of the SNAP-tag to the protein of interest allows specific labeling of the fusion protein with a variety of synthetic dyes, thereby offering enhanced flexibility for fluorescence imaging approaches.

Here we describe the construction and characterization of the HIV derivative HIV^SNAP, which carries the SNAP-tag as an additional domain within the viral structural polyprotein Gag. Introduction of the tag close to the C-terminus of the matrix domain of Gag did not interfere with particle assembly, release or proteolytic virus maturation. The modified virions were infectious and could be propagated in tissue culture, albeit with reduced replication capacity. Insertion of the SNAP domain within Gag allowed specific staining of the viral polyprotein in the context of virus producing cells using a SNAP reactive dye as well as the visualization of individual virions and viral budding sites by stochastic optical reconstruction microscopy. Thus, HIV^SNAP represents a versatile tool which expands the possibilities for the analysis of HIV-cell interactions using live cell imaging and sub-diffraction fluorescence microscopy.

Targeted signal-amplifying enzymes enhance MRI of EGFR expression in an orthotopic model of human glioma

Epidermal growth factor receptor (EGFR) imaging in brain tumors is essential to visualize overexpression of EGFRvIII variants as a signature of highly aggressive gliomas and to identify patients that would benefit from anti-EGFR therapy. Seeking imaging improvements, we tested a novel pretargeting approach that relies on initial administration of enzyme-linked anti-EGFR monoclonal antibodies (mAb; EMD72000) followed by administration of a low-molecular-weight paramagnetic molecule (diTyr-GdDTPA) retained at the site of EGFR mAb accumulation. We hypothesized that diTyr-GdDTPA would become enzyme activated and retained on cells due to binding to tissue proteins. In support of this hypothesis, mAb-enzyme conjugates reacted with both membrane-isolated wild-type (wt) EGFR and EGFRvIII, but they bound primarily to EGFRvIII-expressing cells and not to EGFRwt-expressing cells. In vivo analysis of magnetic resonance (MR) tumor signal revealed differences in MR signal decay following diTyr-GdDTPA substrate administration. These differences were significant in that they suggested differences in substrate elimination from the tissue which relied on the specificity of the initial mAb binding: a biexponential signal decay was observed in tumors only upon preinjection with EGFR-targeted conjugates. Endpoint MRI in this setting revealed detailed images of tumors which correlated with immunohistochemical detection of EGFR expression. Together, our findings suggest an improved method to identify EGFRvIII-expressing gliomas in vivo that are best suited for treatment with therapeutic EGFR antibodies.

Hybrid herpes simplex virus/Epstein-Barr virus amplicon viral vectors confer enhanced transgene expression in primary human tumors and human bone marrow-derived mesenchymal stem cells

BACKGROUND

Herpes simplex virus type-1 (HSV-1) amplicon vectors are attractive tools for gene transfer because of their large DNA insert capacity, their broad host range of vector transduction and a minimal immune response as a result of the absence of helper viruses during viral packaging. However, the transient gene expression remains a challenge for the translation of HSV-1 amplicon based therapeutic strategies to a clinical setting. Although oriP/EBV nuclear antigen (EBNA)-1 elements of Epstein-Barr virus (EBV) have been successfully employed to achieve prolonged transgene expression, little is known about the stability of the EBNA-1 elements in the context of HSV-1 amplicon viral vectors.

METHODS

We have generated HSV/EBV hybrid vectors expressing the mutant EBNA-1 gene with the luciferase reporter gene bicistronically to enable monitoring of EBNA-1 expression in real-time, both in vitro and in vivo.

RESULTS

The results obtained showed that the HSV/EBV hybrid vectors could mediate high levels of transgene expression (ranging from approximately two-fold to nine-fold) in primary human tumor cells and human bone marrow-derived mesenchymal stem cells compared to the control vector. Prolonged transgene expression could also be observed in primary patient-derived human hepatocellular carcinoma xenografts and in the mouse brain parenchyma up to a period of 17 and 365 days, respectively.

CONCLUSIONS

Taken together, we have demonstrated that these hybrid vectors could be promising tools as carriers of therapeutic genes in mesenchymal stem cells or even provide an alternative non-integrating platform for the generation of induced pluripotent stem cells.

Adenovirus-retrovirus hybrid vectors achieve highly enhanced tumor transduction and antitumor efficacy in vivo

Murine leukemia virus (MLV)-based replication-competent retrovirus (RCR) vectors have been shown to mediate efficient, selective, and persistent tumor transduction, thereby achieving significant therapeutic benefit in a wide variety of cancer models. To further augment the efficiency of this strategy, we have developed a delivery method employing a gutted adenovirus encoding an RCR vector (AdRCR); thus, tumor cells transduced with the adenoviral vector transiently become RCR vector producer cells in situ. As expected, high-titer AdRCR achieved significantly higher initial transduction levels in human cancer cells both in vitro and in vivo, as compared to the original RCR vector itself. Notably, even at equivalent initial transduction levels, more secondary RCR progeny were produced from AdRCR-transduced cells as compared to RCR-transduced cells, resulting in further acceleration of subsequent RCR replication kinetics. In pre-established tumor models in vivo, prodrug activator gene therapy with high-titer AdRCR could achieve enhanced efficacy compared to RCR alone, in a dose-dependent manner. Thus, AdRCR hybrid vectors offer the advantages of high production titers characteristic of adenovirus and secondary production of RCR in situ, which not only accelerates subsequent vector spread and progressive tumor transduction, but can also significantly enhance the therapeutic efficacy of RCR-mediated prodrug activator gene therapy.

Herpes simplex virus type 1/adeno-associated virus hybrid vectors

Herpes simplex virus type 1 (HSV-1) amplicons can accommodate foreign DNA of any size up to 150 kbp and, therefore, allow extensive combinations of genetic elements. Genomic sequences as well as cDNA, large transcriptional regulatory sequences for cell type-specific expression, multiple transgenes, and genetic elements from other viruses to create hybrid vectors may be inserted in a modular fashion. Hybrid amplicons use genetic elements from HSV-1 that allow replication and packaging of the vector DNA into HSV-1 virions, and genetic elements from other viruses that either direct integration of transgene sequences into the host genome or allow episomal maintenance of the vector. Thus, the advantages of the HSV-1 amplicon system, including large transgene capacity, broad host range, strong nuclear localization, and availability of helper virus-free packaging systems are retained and combined with those of heterologous viral elements that confer genetic stability to the vector DNA. Adeno-associated virus (AAV) has the unique capability of integrating its genome into a specific site, designated AAVS1, on human chromosome 19. The AAV rep gene and the inverted terminal repeats (ITRs) that flank the AAV genome are sufficient for this process. HSV-1 amplicons have thus been designed that contain the rep gene and a transgene cassette flanked by AAV ITRs. These HSV/AAV hybrid vectors direct site-specific integration of transgene sequences into AAVS1 and support long-term transgene expression.

Peroxisome proliferator-activated receptor-gamma regulates the expression and function of very-low-density lipoprotein receptor

Very-low-density lipoprotein receptor (VLDLR) is a member of the low-density receptor family, highly expressed in adipose tissue, heart, and skeletal muscle. It binds apolipoprotein E-triglyceride-rich lipoproteins and plays a significant role in triglyceride metabolism. PPARgamma is a primary regulator of lipid metabolism in adipocytes and controls the expression of an array of genes involved in lipid trafficking in adipocytes. However, it is not known whether VLDLR is also under the control of PPARgamma. In this study, we investigated the role of PPARgamma in the regulation of VLDLR expression and function in vivo and in vitro. During the differentiation of 3T3-L1 preadipocytes, the levels of VLDLR protein and mRNA increased in parallel with the induction of PPARgamma expression and reached maximum in mature adipocytes. Treatment of differentiated adipocytes with PPARgamma agonist pioglitazone upregulated VLDLR expression in dose- and time-dependent manners. In contrast, specific inhibition of PPARgamma significantly downregulated the protein level of VLDLR. Induction of VLDLR is also demonstrated in vivo in adipose tissue of wild-type (WT) mice treated with pioglitazone. In addition, pioglitazone increased plasma triglyceride-rich lipoprotein clearance and increased epididymal fat mass in WT mice but failed to induce similar effects in vldlr(-/-) mice. These results were further corroborated by the finding that pioglitazone treatment enhanced adipogenesis and lipid deposition in preadipocytes of WT mice, while its effect in VLDLR-null preadipocytes was significantly blunted. These findings provide direct evidence that VLDLR expression is regulated by PPARgamma and contributes in lipid uptake and adipogenesis.

Viral hybrid vectors for somatic integration - are they the better solution?

The turbulent history of clinical trials in viral gene therapy has taught us important lessons about vector design and safety issues. Much effort was spent on analyzing genotoxicity after somatic integration of therapeutic DNA into the host genome. Based on these findings major improvements in vector design including the development of viral hybrid vectors for somatic integration have been achieved. This review provides a state-of-the-art overview of available hybrid vectors utilizing viruses for high transduction efficiencies in concert with various integration machineries for random and targeted integration patterns. It discusses advantages but also limitations of each vector system.

Herpes Virus Amplicon Vectors

Since its emergence onto the gene therapy scene nearly 25 years ago, the replication-defective Herpes Simplex Virus Type-1 (HSV-1) amplicon has gained significance as a versatile gene transfer platform due to its extensive transgene capacity, widespread cellular tropism, minimal immunogenicity, and its amenability to genetic manipulation. Herein, we detail the recent advances made with respect to the design of the HSV amplicon, its numerous in vitro and in vivo applications, and the current impediments this virus-based gene transfer platform faces as it navigates a challenging path towards future clinical testing.

HSV-1-derived amplicon vectors: recent technological improvements and remaining difficulties--a review

Amplicons are defective and non-integrative vectors derived from herpes simplex virus type 1. As the vector genome carries no virus genes, amplicons are both non-toxic for the infected cells and non-pathogenic for the inoculated organisms. In addition, the large transgenic capacity of amplicons, which allow delivery of up to 150 Kbp of foreign DNA, makes these vectors one of the most powerful, interesting and versatile gene delivery platforms. We present here recent technological developments that have significantly improved and extended the use of amplicons, both in cultured cells and in living organisms. In addition, this review also discusses the many difficulties still pending to be solved, in order to achieve stable and physiologically regulated transgene expression.

Mutant sodium channel for tumor therapy

Viral vectors have been used to deliver a wide range of therapeutic genes to tumors. In this study, a novel tumor therapy was achieved by the delivery of a mammalian brain sodium channel, ASIC2a, carrying a mutation that renders it constitutively open. This channel was delivered to tumor cells using a herpes simplex virus-1/Epstein-Barr virus (HSV/EBV) hybrid amplicon vector in which gene expression was controlled by a tetracycline regulatory system (tet-on) with silencer elements. Upon infection and doxycycline induction of mutant channel expression in tumor cells, the open channel led to amiloride-sensitive sodium influx as assessed by patch clamp recording and sodium imaging in culture. Within hours, tumor cells swelled and died. In addition to cells expressing the mutant channel, adjacent, noninfected cells connected by gap junctions also died. Intratumoral injection of HSV/EBV amplicon vector encoding the mutant sodium channel and systemic administration of doxycycline led to regression of subcutaneous tumors in nude mice as assessed by in vivo bioluminescence imaging. The advantage of this direct mode of tumor therapy is that all types of tumor cells become susceptible and death is rapid with no time for the tumor cells to become resistant.

ICP0 inhibits the decrease of HSV amplicon-mediated transgene expression

The herpes simplex virus (HSV) amplicon vector produces an initial host response that limits transgene expression. In this study, we hypothesized that restoration of the HSV gene infected cell protein (ICP0) into the amplicon could circumvent this host response and thus overcome silencing of encoded transgenes. To test this, we constructed an amplicon vector that encodes the ICP0 under control of its native promoter (ICP0+ amplicon). Expression of ICP0 was transient and, at a multiplicity of infection (MOI) of 1, did not significantly alter interferon (IFN)-based responses against the vector or cell kinetics/apoptosis of infected cells. Chromatin immunoprecipitation (ChIP) PCR analysis revealed that conventional amplicon DNA became associated with histone deacetylase 1 (HDAC1) immediately after infection, whereas ICP0+ amplicon DNA remained relatively unbound by HDAC1 for at least 72 hours after infection. Mice administered systemic ICP0+ amplicon exhibited significantly greater and more sustained transgene expression in their livers than did those receiving conventional amplicon, likely due to increased transcriptional or post-transcriptional activity rather than increased copy numbers of vector DNA. These findings indicate that restoration of ICP0 expression may be employed within HSV amplicon constructs to decrease transgene silencing in vitro and in vivo.

Methods, potentials, and limitations of gene delivery to regenerate central nervous system cells

This review evaluates methods, success and limitations of transgenes delivery in central nervous system (CNS). Both viral and nonviral (such as liposome mediated) methods, expression and stability of transgenes have been discussed. The controlled expression and delivery techniques of transgene at the injured or diseased sites have also been discussed. Mifepristone (RU486) and tetracycline-based switch system for controlled expression could be a very useful tool for clinical purposes. Here we emphasized the importance and consequences of viral- and nonviral-mediated transgenes transfer and therapeutic ability along with advantages of controlled expressions.

Stable transgene expression from HSV amplicon vectors in the brain: potential involvement of immunoregulatory signals

The herpes simplex virus (HSV) amplicon is a plasmid-based, infectious gene delivery system that carries up to 150 kilobase (kb) of exogenous DNA. We previously characterized early host responses and stability of transgene expression in mice systemically injected with HSV amplicon vectors. Transgene expression was readily detected primarily in the liver but rapidly declined to undetectable levels within 2 weeks. Molecular analyses revealed induction of type I interferons (IFN) as the primary response, and early transcriptional silencing of the vector followed IFN's activation of signal transducers and activators of transcription 1 (STAT1). In this study, we investigate vector administration by stereotactic injection into the striatum. In the brain, induction of type I IFN was rather modest, and transgene expression lasted more than 1 year despite dose-dependent inflammation and infiltration of immune cells around injection sites. Further analyses revealed dose-dependent upregulation of immunosuppressive cytokines and molecular markers specific to regulatory T cells in the injected brain regions, which supported the immune-privileged properties of the brain parenchyma. Overall, our findings indicate that the spectrum of host responses can differ significantly depending on target organs and administrative routes, and that HSV amplicon vectors hold great potential for gene therapy of chronic neurological disorders.

A formylpeptide receptor, FPRL1, acts as an efficient coreceptor for primary isolates of human immunodeficiency virus

Background

More than 10 members of seven-transmembrane G protein-coupled receptors (GPCRs) have been shown to work as coreceptors for human immunodeficiency virus type 1 (HIV-1), HIV type 2 (HIV-2), and simian immunodeficiency viruses (SIVs). As a common feature of HIV/SIV coreceptors, tyrosine residues are present with asparagines, aspartic acids or glutamic acids in the amino-terminal extracellular regions (NTRs).

We noticed that a receptor for N-formylpeptides, FPRL1, also contains two tyrosine residues accompanied by glutamic acids in its NTR. It was reported that monocytes expressing CCR5 and FPRL1 in addition to CD4 are activated by treatment with ligands or agonists of FPRL1. Activated monocytes down-modulate CCR5 and become resistant to infection by HIV-1 strains. Thus, FPRL1 plays important roles in protection of monocyptes against HIV-1 infection. However, its own coreceptor activity has not been elucidated yet. In this study, we examined coreceptor activities of FPRL1 for HIV/SIV strains including primary HIV-1 isolates.

Results

A CD4-transduced human glioma cell line, NP-2/CD4, is strictly resistant to HIV/SIV infection. We have reported that when NP-2/CD4 cells are transduced with a GPCR having coreceptor activity, the cells become susceptible to HIV/SIV strains. When NP-2/CD4 cells were transduced with FPRL1, the resultant NP-2/CD4/FPRL1 cells became markedly susceptible to some laboratory-adapted HIV/SIV strains. We found that FPRL1 is also efficiently used as a coreceptor by primary HIV-1 isolates as well as CCR5 or CXCR4.

Amino acid sequences linked to the FPRL1 use could not be detected in the V3 loop of the HIV-1 Env protein. Coreceptor activities of FPRL1 were partially blocked by the forymyl-Met-Leu-Phe (fMLF) peptide.

Conclusion

We conclude that FPRL1 is a novel and efficient coreceptor for HIV/SIV strains. FPRL1 works as a bifunctional factor in HIV-1 infection. Namely, the role of FPRL1 in HIV-1 infection is protective and/or promotive in different conditions. FPRL1 has been reported to be abundantly expressed in the lung, spleen, testis, and neutrophils. We detected mRNA expression of FPRL1 in 293T (embryonal kidney cell line), C8166 (T cell line), HOS (osteosarcoma cell line), Molt4#8 (T cell line), U251MG (astrocytoma cell line), U87/CD4 (CD4-transduced glioma cell line), and peripheral blood lymphocytes. Roles of FPRL1 in HIV-1 infection in vivo should be further investigated.

HSV-1 amplicon vectors: a promising and versatile tool for gene delivery

Amplicons are defective and non-integrative vectors derived from herpes simplex virus type 1. They carry no virus genes in the vector genome and are, therefore, not toxic to the infected cells or pathogenic for the transduced organisms, making these vectors safe. In addition, the large transgenic capacity of amplicons, which allow delivery of < or = 150 Kbp of foreign DNA, make these vectors one of the most powerful, interesting and versatile gene delivery platforms. Here, the authors present recent technological developments that have significantly improved and extended the use of amplicons, both in cultured cells and in living organisms. In addition, this review illustrates the many possible applications that are presently being developed with amplicons and discuss the many difficulties still pending to be solved in order to achieve stable and physiologically regulated transgenic expression.

Early STAT1 activation after systemic delivery of HSV amplicon vectors suppresses transcription of the vector-encoded transgene

The herpes simplex virus (HSV) amplicon vector is a powerful gene delivery vehicle that can accommodate up to 150 kilobase of exogenous DNA. However, amplicon-mediated transgene expression is often transient outside the nervous system. In order to define the role of host immune responses in silencing amplicon-encoded transgenes, we evaluated the kinetics of cytokine-/chemokine-expression after tail-vein injection of a luciferase-encoding amplicon into mice. Type I interferons (IFNs) were induced earliest, within an hour after injection, and several other cytokines/chemokines were subsequently upregulated in the livers of wild-type (WT) mice. When the same experiment was performed in signal transducers and activators of transcription 1 (STAT1)-knockout (KO) mice, the levels of type I IFN expression were significantly lower and chemokine induction was almost non-existent. Importantly, STAT1-KO mice exhibited significantly higher and more sustained luciferase activity than did the WT mice, which is attributable to increased transcriptional activity rather than increased copy numbers of luciferase-encoding vector DNA. Further studies using primary cultured fibroblasts derived from WT and STAT1-KO mice revealed the significance of STAT1 signaling in transcriptional silencing of the amplicon-encoded transgene in vitro. Our results indicate that type I IFNs induced by systemic delivery of HSV amplicon vectors initiate a cascade of immune responses and suppress transgene expression at the transcriptional level by activation of STAT1.

Plasmid DNA sequences present in conventional herpes simplex virus amplicon vectors cause rapid transgene silencing by forming inactive chromatin

The herpes simplex virus (HSV)-based amplicon vector, a bacterial-viral-mammalian cell shuttle system, holds promise as a versatile gene delivery vehicle because of its large transgene capacity. However, amplicon-mediated transgene expression is often transient. We hypothesized that the presence of prokaryotic DNA sequences within the packaged vector genome can trigger transcriptional silencing of the entire vector sequence. To test this, we constructed a novel amplicon vector devoid of bacterial sequences (minicircle [MC] amplicon). Although the same dose of the minicircle amplicon vector in normal human fibroblasts resulted in an expression of luciferase approximately 20 times higher than that caused by the conventional amplicon vector, no significant difference was observed in copy numbers of luciferase DNA between MC amplicon- and control-transduced cells. Quantitative analyses of levels of luciferase mRNA revealed that differential expression of luciferase was controlled at the transcriptional level. Chromatin immunoprecipitation PCR analyses of several regions of vector genomes revealed that the bacterial sequences found in the conventional amplicon DNA were associated with an inactive form of chromatin immediately after infection. The presence of bacterial sequences also affected the remaining vector sequences in the conventional amplicon vector. Finally, nude mice injected with the MC amplicon exhibited higher and more sustained expression of luciferase than those injected with the conventional amplicon, confirming the usefulness of the MC amplicon devoid of bacterial sequences. Although additional improvements are absolutely required, these findings are a significant first step toward developing a novel HSV amplicon vector that can achieve enhanced long-term transgene expression.

Efficient site-specific integration of large transgenes by an enhanced herpes simplex virus/adeno-associated virus hybrid amplicon vector

We previously demonstrated that a herpes simplex virus type 1 (HSV-1)/adeno-associated virus (AAV) hybrid amplicon vector constructed by inserting the sequences of regulatory protein (rep) and inverted terminal repeats of AAV into an HSV amplicon vector resulted in the enhanced stability of transgene expression compared to the original HSV-1 amplicon vector. However, problems related to the expression of Rep compromised its therapeutic applications. We report here a new HSV/AAV hybrid amplicon vector system that not only solved problems associated with Rep expression but also markedly improved the stable transduction efficiency of this vector. This new HSV/AAV vector is designed in a way that little or no Rep would be expressed in packaging cells, but it can be expressed in transduced cells if Cre recombinase is provided. Furthermore, Rep expression will be automatically suppressed as a consequence of Rep-mediated integration. Our results showed that the new hybrid amplicon vector yielded titers comparable to those of standard amplicon vectors. When Cre-expressing 293 cells were transduced, a low level of Rep expression was detected, and stable transduction was achieved in approximately 22% of transduced cells; of those cells, approximately 70% transduction was achieved by Rep-mediated site-specific integration. In the majority of the stably transduced cells, Rep expression was no longer observed. Our results also proved that this vector system is capable of efficiently accommodating and site-specifically integrating large transgenes, such as the full-length dystrophin expression cassette. Thus, the new HSV/AAV vector demonstrated unique advantages in safe and effective delivery of long-lasting transgene expression into human cells.

HSV-1-based amplicon vectors: design and applications

Amplicons are defective, helper-dependent herpes simplex virus type 1 (HSV-1)-based vectors able to convey more than 100 kbp of foreign DNA to the nucleus of mammalian cells. This unique feature make amplicons very appealing for preventive or therapeutic gene transfer requiring the transduction of very large pieces of DNA, as well as for upstream fundamental studies, such as functional genomics. Several recent achievements in amplicon technology have allowed to produce relatively large amounts of essentially helper-free amplicons, as well as to expand the host range of these vectors. In this review, we will update the current know-how concerning design, construction, and recent applications, as well as the potential and current limitations, of this interesting and promising class of vectors.

Neural precursor cells and their role in neuro-oncology

Neural precursor cells (NPCs) provide a new mode for delivery of genes and proteins to brain tumors. These cells exist both in the developing and the adult nervous systems of all mammalian organisms. They have the ability to self-renew, migrate to diseased areas of the brain and differentiate into neurons, astrocytes and oligodendrocytes. The migratory ability of NPCs and their capacity to differentiate into all neural phenotypes provides a powerful tool for the treatment of both diffuse and localized neurological disorders. NPCs have been used in transplantation to replace damaged cells and in cancer therapy to provide therapeutic proteins and vectors to eliminate malignant cells in the brain. This review focuses on the characteristics of NPCs and their experimental use in the therapy for brain tumors. Examples are provided of monitoring migration of NPCs by bioluminescence imaging in living animals and of using them to deliver the apoptotic protein, TRAIL, to kill tumor cells.

Enhancing protein expression in single HEK 293 cells

Recombinant proteins are routinely expressed in heterologous expression systems such as human embryonic kidney 293 (HEK 293) cells. The efficiency of the expression is critical when the expressed protein must be characterized at the single-cell level. Here we describe a simple method by which the protein expression efficiency in single HEK 293 cells is enhanced by coexpressing simian virus 40 large T antigen (TAg), a powerful oncoprotein. Using the GluR2 ionotropic glutamate receptor as an example, we found that the receptor expression in single HEK 293S cells increased approximately seven-fold. The ratio of the plasmid amount of TAg to that of the receptor was optimized at 1:10, while the receptor function was unaffected in the presence of TAg. We further used fluorescence imaging from a population of cells as an independent detection method and found a similar increase in expression of green fluorescent protein (GFP) by TAg coexpression. This method is thus applicable for enhancing the expression of both membrane and soluble proteins at the single-cell level. More importantly, the function of a protein can be studied directly in intact cells, a feature particularly useful for studying membrane proteins.

Gene transfer into hepatocytes mediated by herpes simplex virus–Epstein-Barr virus hybrid amplicons

Gene transfer into hepatocytes is highly desirable for the long-term goal of replacing deficient proteins and correcting metabolic disorders. Vectors based on herpes simplex virus type-1 (HSV-1) have been demonstrated to mediate efficient gene transfer into hepatocytes both in vitro and in vivo. Large transgene capacity and extrachromosomal persistence make HSV-1/EBV hybrid amplicon vectors an attractive candidate for hepatic gene replacement therapy. To assess liver-directed gene transfer, we constructed (i) a conventional HSV-1 amplicon vector encoding a secreted reporter protein (secreted alkaline phosphatase, SEAP) under the control of the HSV-1 immediate-early 4/5 promoter; (ii) a HSV-1 amplicon encoding SEAP under the control of the artificial CAG promoter (the chicken beta-actin promoter and cytomegalovirus (CMV) immediate-early enhancer); and (iii) a HSV-1/EBV hybrid amplicon, also encoding SEAP under the control of the CAG promoter. While all three vector constructs yielded high SEAP concentrations in vitro and in vivo, use of HSV-1/EBV hybrid amplicon vectors significantly prolonged the duration of gene expression. Using conventional amplicon vectors in cultured hepatocytes, SEAP was detected for two weeks, whereas SEAP was detected for at least six weeks when HSV-1/EBV amplicons were used. Intraparenchymal injection into the liver of SICD mice yielded high (up to 77 ng of SEAP per milliliter serum) and sustained (greater than three weeks) expression of SEAP. Serum transaminases (ALT/AST) were measured at different time points to monitor for hepatocellular damage. While initially elevated four times above baseline, the transaminase levels returned to normal after three to seven days. These results demonstrate the usefulness of HSV-1-based amplicons and SEAP for the evaluation of gene replacement strategies in the liver.

Mutation of GATA3 in human breast tumors

GATA3 is an essential transcription factor that was first identified as a regulator of immune cell function. In recent microarray analyses of human breast tumors, both normal breast luminal epithelium and estrogen receptor (ESR1)-positive tumors showed high expression of GATA3. We sequenced genomic DNA from 111 breast tumors and three breast-tumor-derived cell lines and identified somatic mutations of GATA3 in five tumors and the MCF-7 cell line. These mutations cluster in the vicinity of the highly conserved second zinc-finger that is required for DNA binding. In addition to these five, we identified using cDNA sequencing a unique mis-splicing variant that caused a frameshift mutation. One of the somatic mutations we identified was identical to a germline GATA3 mutation reported in two kindreds with HDR syndrome/OMIM #146255, which is an autosomal dominant syndrome caused by the haplo-insufficiency of GATA3. The ectopic expression of GATA3 in human 293T cells caused the induction of 73 genes including six cytokeratins, and inhibited cell line doubling times. These data suggest that GATA3 is involved in growth control and the maintenance of the differentiated state in epithelial cells, and that GATA3 variants may contribute to tumorigenesis in ESR1-positive breast tumors.

Perinuclear biogenesis of mutant torsin-A inclusions in cultured cells infected with tetracycline-regulated herpes simplex virus type 1 amplicon vectors

TorsinA is a novel protein identified in the search for mutations underlying the human neurologic movement disorder, early onset torsion dystonia. Relatively little is understood about the normal function of torsinA or the physiological effects of the codon deletion associated with most cases of disease. Overexpression of wild-type torsinA in cultured cells by DNA transfection results in a reticular distribution of immunoreactive protein that co-localizes with endoplasmic reticulum resident chaperones, while the dystonia-related mutant form accumulates within concentric membrane whorls and nuclear-associated membrane stacks. In this study we examined the biogenesis of mutant torsinA-positive membrane inclusions using tetracycline-regulated herpes simplex virus amplicon vectors. At low expression levels, mutant torsinA was localized predominantly around the nucleus, while at high levels it was also concentrated within cytosolic spheroid inclusions. In contrast, the distribution of wild-type torsinA did not vary, appearing diffuse and reticular at all expression levels. These observations are consistent with descriptions of inducible membrane synthesis in other systems in which cytosolic membrane whorls are derived from multilayered membrane stacks that first form around the nuclear envelope. These results also suggest that formation of mutant torsinA-positive inclusions occurs at high expression levels in culture, whereas the perinuclear accumulation of the mutant protein is present even at low expression levels that are more likely to resemble those of the endogenous protein. These nuclear-associated membrane structures enriched in mutant torsinA may therefore be of greater relevance to understanding how the dystonia-related mutation compromises cellular physiology.

Orientation-dependent gene expression with Epstein-Barr virus-derived vectors

Episomal vectors, described for efficient and regulated expression of heterologous proteins in mammalian cells, have the advantage that they persist in multiple copies in the cell without integrating into the chromosome. To efficiently express heterologous proteins we used such a vector based on elements of the Epstein-Barr virus (EBV), namely the sequences coding for Epstein-Barr nuclear antigen 1 and the viral origin of replication. Because constitutive expression is often deleterious to the cell, we combined the interferon-inducible Mx promoter with this EBV-derived vector. This resulted in an efficient and strictly regulated expression of the reporter gene chloramphenicol acetyltransferase (CAT) and of the neurotransmitter receptor h5-HT(1B), reaching levels of 16 ng CAT/mg cytoplasmic protein and 1300 fmol receptor/mg membrane protein, respectively. For both proteins, the expression levels were influenced by the orientation of the expression cassette. The higher expression in the favored orientation did not result from a higher copy number of these episomes. Northern analysis revealed a transcriptional read-through from the thymidine kinase promoter on the episomal vector, which interfered with the transcription of the heterologous gene in the less favored orientation.

Construction of a cytomegalovirus-based amplicon: a vector with a unique transfer capacity

Cytomegalovirus (CMV) has a number of interesting properties that qualifies it as a vector for gene transfer. Especially appealing is the ability of the CMV genome to persist in hematopoietic progenitor cells and the packaging capacity of the viral capsid that accommodates a DNA genome of 230 kbp. In order to exploit the packaging capacity of the CMV capsid we investigated whether the principles of an amplicon vector can be applied to CMV. Amplicons are herpesviral vectors, which contain only the cis-active sequences required for replication and packaging of the vector genome. For construction of a CMV amplicon the sequences comprising the lytic origin of replication (orilyt) and the cleavage packaging recognition sites (pac) of human CMV were cloned onto a plasmid. A gene encoding the green fluorescent protein was used as a model transgene. The amplicon plasmid replicated in the presence of a CMV helper virus and was packaged into CMV particles, with replication and packaging being dependent on the presence of the orilyt and pac sequences. The packaged amplicon could be transferred to recipient cells and reisolated from the transduced cells. Analysis of the DNA isolated from CMV capsids revealed that the CMV amplicon was packaged as a concatemer with a size of approximately 210 kbp. The CMV amplicon vector has the potential to transfer therapeutic genes with a size of more than 200 kbp and thus provides a unique transfer capacity among viral vectors.

Potentiated gene delivery to tumors using herpes simplex virus/Epstein-Barr virus/RV tribrid amplicon vectors

The development and use of gene transfer techniques creates an opportunity to achieve better treatment modalities for numerous disease entities. Promising results for treatment in tumor cells in culture and in small animal models have been reported. Nevertheless, the lack of widespread vector distribution throughout tumor tissue is one of the current limitations for successful clinical application of gene therapy paradigms. The use of migratory tumor cells themselves as vector delivery vehicles may allow wider vector distribution in tumors. In addition, continuous release of retrovirus vectors on-site could generate a high local virion concentration over an extended time period with consequent increases in transduction efficiency. In this paper, we present in culture and in vivo data of a herpes simplex virus-Epstein-Barr virus hybrid amplicon vector containing retrovirus vector components (tribrid vector) that allows conversion of tumor cells into retroviral producer cells. With this method, we were able to achieve a local fourfold amplification of stable transgene expression in tumors. The application of this system, which can integrate a transgene cassette into tumors with therapeutic bystander effects, could increase the local amplification effect to a level of clinical relevance.

Dynamics of transgene expression in human glioblastoma cells mediated by herpes simplex virus/adeno-associated virus amplicon vectors

One of the challenges in gene therapy is to ensure stable transgene expression at the site of disease with a high degree of accuracy and safety. In this paper, we examine both viral and cellular elements that may affect the level of transgene expression mediated by herpes simplex virus type 1 (HSV-1) adeno-associated virus (AAV) amplicon vectors. These elements include the AAV inverted terminal repeats (ITRs), the AAV Rep proteins, and the allelic status of 19q in human glioma cell lines. The latter is of particular interest because the AAV integration site (AAVS1) is located on the long arm of chromosome 19 and 30-40% of human glioblastoma tumors are reported to have loss of heterozygosity in this region of chromosome 19q. Fluorescence-activated cell-sorting analysis results indicate that inclusion of minimal or full-length AAV ITRs in HSV-1 amplicon vectors markedly increases the efficiency of transgene expression. On the other hand, insertion of the AAV rep gene decreases the level of transgene expression, apparently because of the cytotoxic effects of Rep proteins. Further, the levels of transgene expression appear to be independent of 19q allelic status or the number of endogenous AAVS1 sequences in the various glioma cell lines studied. Taken together, these data support employing AAV ITRs, in the context of HSV-1 amplicon vectors, to enhance short-term levels of transgene expression.