Rapid titer determination using quantitative real-time PCR

Peptides as surface coatings of nanoparticles that penetrate human cystic fibrosis sputum and uniformly distribute in vivo following pulmonary delivery

Therapeutic delivery of drug and gene delivery systems have to traverse multiple biological barriers to achieve efficacy. Mucosal administration, such as pulmonary delivery in cystic fibrosis (CF) disease, remains a significant challenge due to concentrated viscoelastic mucus, which prevents drugs and particles from penetrating the mucus barrier. To address this problem, we used combinatorial peptide-presenting phage libraries and next-generation sequencing (NGS) to identify hydrophilic, net-neutral charged peptide coatings that enable penetration through human CF mucus ex vivo with ~600-fold better penetration than control, improve uptake into lung epithelial cells compared to uncoated or PEGylated-nanoparticles, and exhibit enhanced uniform distribution and retention in the mouse lung airways. These peptide coatings address multiple delivery barriers and effectively serve as excellent alternatives to standard PEG surface chemistries to achieve mucus penetration and address some of the challenges encountered using these chemistries. This biomolecule-based strategy can address multiple delivery barriers and hold promise to advance efficacy of therapeutics for diseases like CF.

Targeting Endothelial Erk1/2-Akt Axis as a Regeneration Strategy to Bypass Fibrosis during Chronic Liver Injury in Mice

Liver sinusoidal endothelial cells (LSECs) have great capacity for liver regeneration, and this capacity can easily switch to profibrotic phenotype, which is still poorly understood. In this study, we elucidated a potential target in LSECs for regenerative treatment that can bypass fibrosis during chronic liver injury. Proregenerative LSECs can be transformed to profibrotic phenotype after 4 weeks of carbon tetrachloride administration or 10 days of bile duct ligation. This phenotypic alternation of LSECs was mediated by extracellular regulated protein kinases 1 and 2 (Erk1/2)-Akt axis switch in LSECs during chronic liver injury; Erk1/2 was normally associated with maintenance of the LSEC proregenerative phenotype, inhibiting hepatic stellate cell (HSC) activation and promoting tissue repair by enhancing nitric oxide (NO)/reactive oxygen species (ROS) ratio and increasing expression of hepatic growth factor (HGF) and Wingless-type MMTV integration site family member 2 (Wnt2). Alternatively, Akt induced LSEC profibrotic phenotype, which mainly stimulated HSC activation and concomitant senescence by reducing NO/ROS ratio and decreasing HGF/Wnt2 expression. LSEC-targeted adenovirus or drug particle to promote Erk1/2 activity can alleviate liver fibrosis, accelerate fibrosis resolution, and enhance liver regeneration. This study demonstrated that the Erk1/2-Akt axis acted as a switch to regulate the proregenerative and profibrotic phenotypes of LSECs, and targeted therapy promoted liver regeneration while bypassing fibrosis, providing clues for a more effective treatment of liver diseases.

Shedding dynamics of Morogoro virus, an African arenavirus closely related to Lassa virus, in its natural reservoir host Mastomys natalensis

Arenaviruses can cause mild to severe hemorrhagic fevers. Humans mainly get infected through contact with infected rodents or their excretions, yet little is known about transmission dynamics within rodent populations. Morogoro virus (MORV) is an Old World arenavirus closely related to Lassa virus with which it shares the same host species Mastomys natalensis. We injected MORV in its host, and sampled blood and excretions at frequent intervals. Infection in adults was acute; viral RNA disappeared from blood after 18 days post infection (dpi) and from excretions after 39 dpi. Antibodies were present from 7 dpi and never disappeared. Neonatally infected animals acquired a chronic infection with RNA and antibodies in blood for at least 3 months. The quantified excretion and antibody patterns can be used to inform mathematical transmission models, and are essential for understanding and controlling transmission in the natural rodent host populations.

Modification of hematopoietic stem/progenitor cells with CD19-specific chimeric antigen receptors as a novel approach for cancer immunotherapy

Chimeric antigen receptors (CARs) against CD19 have been shown to direct T-cells to specifically target B-lineage malignant cells in animal models and clinical trials, with efficient tumor cell lysis. However, in some cases, there has been insufficient persistence of effector cells, limiting clinical efficacy. We propose gene transfer to hematopoietic stem/progenitor cells (HSPC) as a novel approach to deliver the CD19-specific CAR, with potential for ensuring persistent production of effector cells of multiple lineages targeting B-lineage malignant cells. Assessments were performed using in vitro myeloid or natural killer (NK) cell differentiation of human HSPCs transduced with lentiviral vectors carrying first and second generations of CD19-specific CAR. Gene transfer did not impair hematopoietic differentiation and cell proliferation when transduced at 1-2 copies/cell. CAR-bearing myeloid and NK cells specifically lysed CD19-positive cells, with second-generation CAR including CD28 domains being more efficient in NK cells. Our results provide evidence for the feasibility and efficacy of the modification of HSPC with CAR as a strategy for generating multiple lineages of effector cells for immunotherapy against B-lineage malignancies to augment graft-versus-leukemia activity.

Developing novel lentiviral vectors into clinical products

Gene therapy vectors based on murine retroviruses have now been in clinical trials for over 20 years. During that time, a variety of novel vector pseudotypes were developed in an effort to improve gene transfer. Lentiviral vectors are now in clinical trials and a similar evolution of vector technology is anticipated. These modifications present challenges for those producing large-scale clinical materials. This chapter discusses approaches to process development for novel lentiviral vectors, highlight considerations, and methods to be incorporated into the development schema.

A reporter system for replication-competent gammaretroviruses: the inGluc-MLV-DERSE assay

While novel retroviral vectors for use in gene-therapy products are reducing the potential for formation of replication-competent retrovirus (RCR), it remains crucial to screen products for RCR for both research and clinical purposes. For clinical grade gammaretrovirus-based vectors, RCR screening is achieved by an extended S+L− or marker rescue assay, while standard methods for replication-competent lentivirus detection are still in development. In this report, we describe a rapid and sensitive method for replication-competent gammaretrovirus detection. We used this assay to detect three members of the gammaretrovirus family and compared the sensitivity of our assay with well-established methods for retrovirus detection, including the extended S+L− assay. Results presented here demonstrate that this assay should be useful for gene-therapy product testing.

Cellular tumor vaccines administered after T cell-depleted allogeneic bone marrow transplantation induce effective anti-tumor immune responses

In allogeneic hematopoietic stem cell (HSC) transplantation, graft vs. tumor (GVT) activity contributes to the cancer cure. It is closely associated with graft vs. host disease (GVHD), an immune response initiated by transplanted donor T-cell responses against host minor histocompatibility antigens (mHAgs). GVHD is prevented by T-cell depletion of the donor graft, but T-cell depletion also abrogates curative GVT. We wished to test the hypothesis that cellular tumor vaccines administered after T cell-depleted HSC transplant can induce significant GVT effects, despite the absence of transplanted mature donor T cells. In this investigation, a murine model of major histocompatibility complex (MHC)-matched, mHAg-mismatched allogeneic HSC transplant was studied. T cell-depleted or normal T cell-containing grafts were given to myeloablated recipients. Following reconstitution the recipients were vaccinated with tumor vaccines. GVT responses were measured in vitro by T-cell function assays and flow cytometry, and in vivo by tumor burden or survival. Post-transplant tumor vaccines induced effective anti-tumor responses in recipients of T cell-depleted transplants, producing cytolytic and cytokine responses, reduced tumor burden and prolonged survival. Recipients of T cell-depleted transplants that still have significant thymic function may be suitable subjects for post-transplant vaccine therapy.

High-titer preparation of Bombyx mori nucleopolyhedrovirus (BmNPV) displaying recombinant protein in silkworm larvae by size exclusion chromatography and its characterization

Background

Budded baculoviruses are utilized for vaccine, the production of antibody and functional analysis of transmembrane proteins. In this study, we tried to produce and purify the recombinant Bombyx mori nucleopolyhedrovirus (rBmNPV-hPRR) that displayed human (pro)renin receptor (hPRR) connected with FLAG peptide sequence on its own surface. These particles were used for further binding analysis of hPRR to human prorenin. The rBmNPV-hPRR was produced in silkworm larvae and purified from its hemolymph using size exclusion chromatography (SEC).

Results

A rapid method of BmNPV titer determination in hemolymph was performed using quantitative real-time PCR (Q-PCR). A correlation coefficient of BmNPV determination between end-point dilution and Q-PCR methods was found to be 0.99. rBmNPV-hPRR bacmid-injected silkworm larvae produced recombinant baculovirus of 1.31 × 10⁸ plaque forming unit (pfu) in hemolymph, which was 2.8 × 10⁴ times higher than transfection solution in Bm5 cells. Its purification yield by Sephacryl S-1000 SF column chromatography was 264 fold from larval hemolymph at 4 days post-injection (p.i.), but 35 or 39 fold at 4.5 or 5 days p.i., respectively. Protein patterns of rBmNPV-hPRR purified at 4 and 5 days were the same and ratio of envelope proteins (76, 45 and 35 kDa) to VP39, one of nucleocapsid proteins, increased at 5 days p.i. hPRR was detected in only purified rBmNPV-hPRR at 5 days p.i..

Conclusion

The successful purification of rBmNPV-hPRR indicates that baculovirus production using silkworm larvae and its purification from hemolymph by Sephacryl S-1000 SF column chromatography can provide an economical approach in obtaining the purified BmNPV stocks with high titer for large-scale production of hPRR. Also, it can be utilized for further binding analysis and screening of inhibitors of hPRR.

Chemoprotection by transfer of resistance genes

Dose-limiting toxicity of chemotherapeutic agents, i.e., myelosuppression, can limit their effectiveness. The transfer and expression of drug-resistance genes might decrease the risks associated with acute hematopoietic toxicity. Protection of hematopoietic stem/progenitor cells by transfer of drug-resistance genes provides the possibility of intensification or escalation of antitumor drug doses and consequently an improved therapeutic index. This chapter reviews drug-resistance gene transfer strategies for either myeloprotection or therapeutic gene selection. Selecting candidate drug-resistance gene(s), gene transfer methodology, evaluating the safety and the efficiency of the treatment strategy, relevant in vivo models, and oncoretroviral transduction of human hematopoietic stem/progenitor cells under clinically applicable conditions are described.

Genetic modification of human hematopoietic cells: preclinical optimization of oncoretroviral-mediated gene transfer for clinical trials

This chapter provides information about the oncoretroviral transduction of human hematopoietic stem/ progenitor cells under clinically applicable conditions. We describe in detail a short -60 h transduction protocol which consistently yields transduction efficiencies in the range of 30-50% with five different oncoretroviral vectors. We discuss a number of parameters that affect transduction efficiency, including the oncoretroviral vector characteristics, the vector stock collection, the source of CD34+ cells and transduction conditions.

Retroviral vectors for clinical immunogene therapy are stable for up to 9 years

Recombinant retroviruses are one of the most commonly used gene transfer vehicles for therapeutic gene delivery. The stability of viral vectors upon long-term storage, anticipated to be short lived, is expected to impact timeline and financial course of clinical immunogene therapy. However, to date little is known about vector stability. Therefore, we analyzed the stability of retroviral vectors produced in culture supernatants (RTVsup) for ex vivo gene therapy upon long-term storage. We have generated RTVsups derived from two packaging cell lines, PG13 and Phoenix(Ampho). Both lines produced murine leukemia virus-derived SFG-scFv(G250)-CD4gamma vector, which were pseudotyped with the gibbon ape leukemia virus envelope and amphotropic envelope, respectively. The supernatants were stored at -80 or -196 degrees C. To date, the PG13-derived RTVsups have been evaluated over a period of 9 years (1998-2007). In addition, a clinical batch of Phoenix(Ampho)-derived RTVsup has been evaluated over a period of 5 years (2002-2007). Here, we show that both RTVsups, when stored up to 9 and 5 years, respectively, do not show any sign of decay in their capacity to functionally transduce primary human T cells. These data provide evidence that in terms of 'life expectancy' the production and storage of clinical batches of RTVsup for gene therapy warrants the corresponding professional and financial risks.

Quantitative polymerase chain reaction as a reliable method to determine functional lentiviral titer afterex vivo gene transfer in human mesenchymal stem cells

BACKGROUND

Human mesenchymal stem cells (hMSCs) are a promising target for ex vivo gene therapy and lentiviruses are excellent gene transfer vehicles in hMSCs since they achieve high transduction rates with long-term gene expression. Nevertheless, senescence of hMSCs may limit therapeutic applications due to time-consuming cell selection and viral titration. Here, we describe a fast and reliable method to determine functional lentiviral titer by quantitative polymerase chain reaction (qPCR) after highly efficient ex vivo gene transfer in hMSCs.

METHODS

Lentivirus production was tested with different types of packaging systems. Using p24 ELISA remaining viral particles were detected in the cell culture supernatant. The lentiviral gene transfer efficiency was quantified by FACS analysis. Lentiviral titers were determined by qPCR of expressed transgenes.

RESULTS

Third-generation self-inactivating vectors showed highly efficient gene transfer in hMSCs. No viral antigen was detected in the cell culture supernatant after four media changes, suggesting the absence of infectious particles after 4 days. We observed a linear correlation between virus dilution and level of transgene expression by qPCR analysis, therefore allowing viral titering by quantification of transgene expression. Finally, we demonstrated that transduced hMSCs retained their stem cell character by differentiation towards adipogenic, osteogenic and chondrogenic lineages.

CONCLUSIONS

Quantification of transgene copy numbers by qPCR is a fast and reliable method to determine functional lentiviral titer after ex vivo gene transfer in hMSCs.

Functional analysis of gammaretroviral vector transduction by quantitative PCR

BACKGROUND

In a clinical setting of gene therapy, quantitative methods are required to determine recombinant viral titres and transgene mRNA expression, avoiding the use of reporter genes.

METHODS

We describe procedures based on quantitative polymerase chain reaction (qPCR) designed to assess functional titres of murine leukaemia virus (MLV) vectors, determine proviral copy numbers in transduced cells, and estimate retroviral transgene expression in both target cell lines and mice with transduced chimeric haematopoiesis.

RESULTS

Compared to EGFP titration, proviral DNA detection by qPCR was more accurate in assessing the number of infective particles in supernatants, such that average viral titres in terms of proviral copies per cell were two-fold higher. Transgene mRNA expression was directly determined from the vectors used without the need for reporter assays. A new parameter, defined here as the 'transcription index' (TI), served to establish the association between transcribed transgenic mRNA and each proviral insertion. The TI represents the potential expression of every vector or insertion in each cell type, and is thus useful as a control parameter for monitoring preclinical or clinical protocols.

CONCLUSIONS

The practical use of qPCR is demonstrated as a valuable alternative to reporter genes for the assessment and surveillance of insertion numbers and transgene expression. In combination with protein expression, this approach should be capable of establishing safer therapeutic gene doses, avoiding the potential side effects of high transduction and expression levels.

Complete Regression of Large Solid Tumors Using Engineered Drug-Resistant Hematopoietic Cells and Anti-CD137 Immunotherapy

Combining chemotherapy and immunotherapy is problematic because chemotherapy can ablate the immune responses initiated by modulators of the immune system. We hypothesized that protection of immunocompetent cells from the toxic effects of chemotherapy, using drug resistance gene therapy strategies, would allow the combined use of chemotherapy and immunotherapy. In wild-type mice, the antitumor effectiveness of an immunotherapy regimen employing an agonistic anti-CD137 antibody is diminished with escalating doses of the antifolate trimetrexate (TMTX). Using retroviral gene transfer of a mutant form of dihydrofolate reductase (L22Y-DHFR), hematopoietic stem cells were genetically engineered to withstand the toxic effects of TMTX. Mice transplanted with L22Y-DHFR-modified bone marrow were then challenged with AG104 sarcoma cells and treated with TMTX only, anti-CD137 only, or a combination of chemotherapy and immunotherapy. Although tumor burden was transiently decreased during TMTX administration, no mice treated with TMTX alone survived the tumor challenge, whereas approximately 40% of transplanted mice treated with anti-CD137 alone survived. However, 100% of mice survived with complete tumor regression after transplantation with L22Y-DHFR-transduced bone marrow followed by combined treatment with TMTX and anti-CD137. In addition, adoptive transfer of splenocytes from cured mice extended the survival of tumor- bearing animals by approximately 3 weeks compared with controls. Therefore, protection of the hematopoietic system can allow for the combined administration of chemotherapy and immunotherapy, which results in complete tumor clearance.

Factors affecting the performance of different long terminal repeats in the retroviral vector

The long terminal repeat (LTR) of retrovirus contains the nucleotide sequences that control gene expression. Although several different LTRs have been used in the context of retroviral vector, the activity of the various LTRs has not yet been systematically compared for their level of gene expression. We evaluated the effect of four different LTRs on gene expression using luciferase, stem cell factor, and enhanced green fluorescence protein as reporter genes. LTRs tested in this study were derived from Moloney murine leukemia virus, myeloproliferative sarcoma virus, murine stem cell virus, and spleen focus-forming virus. It was found that the level of gene expression is affected by not only LTRs but also the transgenes and the cell types in which gene expression occurs. Furthermore, the presence of other nucleotide sequences such as the internal ribosome entry site (IRES)-neo cassette could also significantly affect gene expression. Our results suggested that the LTR should be chosen carefully, more or less on an empirical basis.

Retroviral vector production in the National Gene Vector Laboratory at Indiana University

The National Gene Vector Laboratory (NGVL) is a US National Institutes of Health initiative charged with providing clinical grade vectors for gene therapy trials. The program was started in 1995 and Indiana University has served as the production site for retroviral vectors and is also accepting applications for production of lentiviral vectors. The facility is designed to produce vectors for Phase I and Phase II clinical trials with the specific mandate to facilitate investigator-initiated research for academic institutions. To date, the facility has generated over 30 Master Cell Banks for gene therapy investigators throughout the United States. This required the facility to develop a system that can adapt to the varied needs of investigators, most of whom request different vector backbones, packaging cell lines, final product volumes, and media. In this review, we will illustrate some of the experiences of the Indiana University NGVL during the generation of retroviral vectors using murine-based packaging cell lines.

Neuroblastoma Cells Transiently Transfected to Simultaneously Express the Co-Stimulatory Molecules CD54, CD80, CD86, and CD137L Generate Antitumor Immunity in Mice

The goal of this study was to show that nonviral gene transfection technology can be used to genetically modify neuroblastoma cells with immune stimulatory molecules, and that the modified cells can generate an antitumor immune response. The authors found that an electroporation-based gene transfection method, nucleofection, could be used to modify mouse AGN2a (an aggressive variant of Neuro-2a) neuroblastoma cells to simultaneously express as many as four different immune stimulatory molecules encoded by separate plasmid vectors. Within 18 hours after nucleofection, greater than 60% of the cells typically expressed the transfected gene products, and the percentages of cells expressing the products often exceeded 96%. High levels of plasmid in cell nuclei immediately after nucleofection documented instantaneous availability of gene vectors to the transcriptional machinery. AGN2a cells nucleofected to express the co-stimulatory molecules CD80 and CD86 expressed higher levels of these molecules than cells that had been permanently transfected with these same plasmid vectors, and the nucleofected cells were as effective as the permanently transfected cells at inducing an antitumor response in vivo in a tumor prevention model. AGN2a cells nucleofected with four separate plasmid vectors encoding CD54, CD80, CD86, and CD137L induced a T-cell immune response in vitro and served as a potent tumor vaccine in the tumor prevention model. These data show that transient transfection using a nonviral based method, nucleofection, can be used to rapidly generate novel cell-based tumor vaccines.

Immediate transfection of patient-derived leukemia: a novel source for generating cell-based vaccines

Background

The production of cell-based cancer vaccines by gene vectors encoding proteins that stimulate the immune system has advanced rapidly in model systems. We sought to develop non-viral transfection methods that could transform patient tumor cells into cancer vaccines, paving the way for rapid production of autologous cell-based vaccines.

Methods

As the extended culture and expansion of most patient tumor cells is not possible, we sought to first evaluate a new technology that combines electroporation and chemical transfection in order to determine if plasmid-based gene vectors could be instantaneously delivered to the nucleus, and to determine if gene expression was possible in a cell-cycle independent manner. We tested cultured cell lines, a primary murine tumor, and primary human leukemia cells from diagnostic work-up for transgene expression, using both RFP and CD137L expression vectors.

Results

Combined electroporation-transfection directly delivered plasmid DNA to the nucleus of transfected cells, as demonstrated by confocal microscopy and real-time PCR analysis of isolated nuclei. Expression of protein from plasmid vectors could be detected as early as two hours post transfection. However, the kinetics of gene expression from plasmid-based vectors in tumor cell lines indicated that optimal gene expression was still dependent on cell division. We then tested to see if pediatric acute lymphocytic leukemia (ALL) would also display the rapid gene expression kinetics of tumor cells lines, determining gene expression 24 hours after transfection. Six of 12 specimens showed greater than 17% transgene expression, and all samples showed at least some transgene expression.

Conclusion

Given that transgene expression could be detected in a majority of primary tumor samples analyzed within hours, direct electroporation-based transfection of primary leukemia holds the potential to generate patient-specific cancer vaccines. Plasmid-based gene therapy represents a simple means to generate cell-based cancer vaccines and does not require the extensive infrastructure of a virus-based vector system.

Highly efficient transduction of repopulating bone marrow cells using rapidly concentrated polymer-complexed retrovirus

Using the cationic polymer, Polybrene, and the anionic polymer, chondroitin sulfate C, we concentrated recombinant retrovirus pseudotyped with an ecotropic envelope, which is susceptible to inactivation by high-speed concentration methods. To evaluate gene marking, murine bone marrow was harvested from C3H mice, transduced with polymer-concentrated GFP virus, and transplanted into lethally irradiated recipients. Total gene marking in mice averaged 30-35% at 8 weeks post-transplant and transgene expression remained stable for over 16 weeks. Using the polymer concentration method, a second retroviral vector encoding the drug resistant variant of dihydrofolate reductase (L22Y-DHFR) was concentrated and tested. Approximately 40% of transduced murine bone marrow progenitor cells were protected against trimetrexate concentrations that completely eliminated the growth of non-modified cells. These results show that anionic and cationic polymers can be combined to rapidly concentrate viruses that are normally difficult to concentrate, and the concentrated virus efficiently transduces hematopoietic stem cells.

Real-Time PCR: an Effective Tool for Measuring Transduction Efficiency in Human Hematopoietic Progenitor Cells

Accurate measurement of gene transfer into hematopoietic progenitor cells is an essential prerequisite for assessing the utility of gene therapy approaches designed to correct hematologic defects. We developed a reliable method to measure transduction efficiency at the level of the progenitor cell with real-time polymerase chain reaction (PCR) analysis of individual progenitor-derived colonies. We hypothesized that this method would demonstrate better sensitivity and specificity than are currently achievable with conventional PCR. An oncoretroviral vector containing the enhanced green fluorescent protein was used to transduce human CD34⁺ cells derived from bone marrow or granulocyte-colony-stimulating factor-mobilized peripheral blood. Progenitor assays were set up and colonies plucked after visualization by fluorescence microscopy. By analyzing microscopically identified fluorescent samples and nontransduced samples, we calculated an overall sensitivity and specificity of 90.2 and 95.0%, respectively. Real-time PCR had higher specificity and sensitivity than conventional PCR as analyzed by generalized linear models (P = 0.002 and P = 0.019, respectively). In conclusion, we found real-time PCR to have superior sensitivity and specificity compared to conventional PCR in determining transduction efficiency of hematopoietic progenitor cells.

Real-time Fluorescent PCR Techniques to Study Microbial-Host Interactions

This chapter describes how real-time polymerase chain reaction (PCR) performs and how it may be used to detect microbial pathogens and the relationship they form with their host. Research and diagnostic microbiology laboratories contain a mix of traditional and leading-edge, in-house and commercial assays for the detection of microbes and the effects they impart upon target tissues, organs, and systems. The PCR has undergone significant change over the last decade, to the extent that only a small proportion of scientists have been able or willing to keep abreast of the latest offerings. The chapter reviews these changes. It discusses the second-generation of PCR technology-kinetic or real-time PCR, a tool gaining widespread acceptance in many scientific disciplines but especially in the microbiology laboratory.

Rapid titer determination of baculovirus by quantitative real-time polymerase chain reaction

Titer determination is a prerequisite for the study of viruses. However, the current available methods are tedious and time-consuming. To improve the efficiency of titer determination, we have developed a rapid and simple method for the routine detection of baculovirus titers using a quantitative real-time PCR. This method is based on the amplification of approximately 150-bp fragments located in the coding regions of selected genes. The PCR was found to be quantitative in a range of 10(3) to 10(9) virus particles per 200 microL of supernatant, and the results were closely correlated with titers detected from 50% tissue culture infectious doses (TCID(50)) of baculovirus. This quantitative real-time PCR requires only 30 min to perform, and the entire titer determination can be accomplished within 1 h without the need for cell seeding or further virus dilution and infection. Because this technology is easy to operate, generates data with high precision, and most importantly is very quick, it will certainly be broadly applied for titer determination of baculoviruses in the future.

Relative gene-silencing efficiencies of small interfering RNAs targeting sense and antisense transcripts from the same genetic locus

Short interfering RNAs (siRNAs) directed against different regions of genes display marked variation in their potency in mediating mRNA degradation. Various factors have been proposed to affect the efficacy of siRNA. We explored some of the factors by evaluating in cultured human cells 28 randomly selected siRNAs targeting the GPR39 and MGC29643 transcripts derived from the same genetic locus but transcribed in opposite directions. Twenty of the 24 siRNAs targeting the overlapping regions of the transcripts simultaneously reduced the levels of both transcripts. Single nucleotide changes in either of the siRNA strands significantly reduced the gene-silencing efficiency of the siRNA on targeted sense transcript without affecting the antisense transcript. Overall, we observed a greater gene-silencing efficiency on the MGC29643 transcript than on the GPR39 transcript in HeLa cells. Since MGC29643 transcript is more abundant than the GPR39 transcript [0.24 versus 0.008% relative to 100% for glyceraldehyde-3-phosphate dehydrogenase (GAPDH)], the results suggest that the abundance of the mRNA affects the efficiency of silencing. Two additional observations supported this hypothesis. First, GAPDH whose intracellular level is the highest of the three was the most efficiently silenced. Second, a reversal of gene-silencing efficiency was observed in U-138 MG cells in which the relative abundance of the GPR39 and MGC29643 transcripts is also reversed. Our study suggests that low-abundant transcripts are less susceptible to siRNA-mediated degradation than medium- and high-abundant transcripts.

In vivo selection of human hematopoietic cells in a xenograft model using combined pharmacologic and genetic manipulations

Strategies that increase the ability of human hematopoietic stem and progenitor cells to repair alkylator-induced DNA damage may prevent the severe hematopoietic toxicity in patients with cancer undergoing high-dose alkylator therapy. In the context of genetic diseases, this approach may allow for selection of small numbers of cells that would not otherwise have a favorable growth advantage. No studies have tested this approach in vivo using human hematopoietic stem and progenitor cells. Human CD34(+) cells were transduced with a bicistronic oncoretrovirus vector that coexpresses a mutant form of O(6)-methylguanine DNA methyltransferase (MGMT(P140K)) and the enhanced green fluorescent protein (EGFP) and transplanted into nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. Mice were either not treated or treated with O(6)-benzylguanine (6BG) and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). At 8-weeks postinjection, a 2- to 8-fold increase in the percentage of human CD45(+)EGFP(+) cells in 6BG/BCNU-treated versus nontreated mice was observed in the bone marrow and was associated with increased MGMT(P140K)-repair activity. Functionally, 6BG/BCNU-treated mice demonstrated multilineage differentiation in vivo, although some skewing in the maturation of myeloid and B cells was observed in mice transplanted with granulocyte-colony stimulating factor (G-CSF)-mobilized peripheral blood compared to umbilical cord blood. Expansion of human cells in 6BG/BCNU-treated mice was observed in the majority of mice previously transplanted with transduced umbilical cord blood cells. In addition, a significant increase in the number of EGFP(+) progenitor colonies in treated versus nontreated mice were observed in highly engrafted mice indicating that selection and maintenance of human progenitor cells can be accomplished by expression of MGMT(P140K) and treatment with 6BG/BCNU.

Real-time PCR in the microbiology laboratory

Use of PCR in the field of molecular diagnostics has increased to the point where it is now accepted as the standard method for detecting nucleic acids from a number of sample and microbial types. However, conventional PCR was already an essential tool in the research laboratory. Real-time PCR has catalysed wider acceptance of PCR because it is more rapid, sensitive and reproducible, while the risk of carryover contamination is minimised. There is an increasing number of chemistries which are used to detect PCR products as they accumulate within a closed reaction vessel during real-time PCR. These include the non-specific DNA-binding fluorophores and the specific, fluorophore-labelled oligonucleotide probes, some of which will be discussed in detail. It is not only the technology that has changed with the introduction of real-time PCR. Accompanying changes have occurred in the traditional terminology of PCR, and these changes will be highlighted as they occur. Factors that have restricted the development of multiplex real-time PCR, as well as the role of real-time PCR in the quantitation and genotyping of the microbial causes of infectious disease, will also be discussed. Because the amplification hardware and the fluorogenic detection chemistries have evolved rapidly, this review aims to update the scientist on the current state of the art. Additionally, the advantages, limitations and general background of real-time PCR technology will be reviewed in the context of the microbiology laboratory.

Distinct temporal genetic signatures of neurogenic and gliogenic cues in cortical stem cell cultures

Cortical progenitor cells from rat embryos give rise to neurons or glia following exposure to platelet derived growth factor (PDGF) or ciliary neurotrophic factor (CNTF), respectively. Both growth factors impart their developmental cues quickly through a transcription-dependent mechanism. Do the alternate developmental responses to PDGF and CNTF reflect induction of qualitatively distinct genes? Alternatively, do the same genes respond to each growth factor, but with quantitatively distinct kinetics? Using differential library screening and custom cDNA microarrays we show that a common set of genes responds to either growth factor. However, quantitative differences in the onset and duration of gene induction equate to the expression of factor-specific gene signatures. Multitissue cluster analysis also reveals tissue-specific gene signatures that may play important roles in the developing brain.

Real-time quantitative reverse transcriptase-polymerase chain reaction as a method for determining lentiviral vector titers and measuring transgene expression

The use of lentiviral vectors for basic research and potential future clinical applications requires methodologies that can accurately determine lentiviral titers and monitor viral transgene expression within target cells, beyond the context of reporter genes typically used for this purpose. Here we describe a quantitative RT-PCR (qRT-PCR) method that achieves both goals using primer sequences that are specific for the woodchuck hepatitis virus posttranscriptional regulatory element (WPRE), an enhancer contained in many retroviral vectors and that is incorporated in the 3' UTR of nascent transgene transcripts. Quantitation of titers of three recombinant lentiviruses, genetically identical except for the transgene, demonstrated consistent differences in titer that were likely due to transgene-associated toxicity in producer cells and target cells. Viruses encoding the tumor-associated antigens tyrosinase and neo-poly(A) polymerase yielded reproducibly lower titers than a virus encoding enhanced green fluorescent protein (GFP) at the viral RNA, integrated DNA, and transgene mRNA levels, as measured by WPRE qPCR. Furthermore, the magnitude of differences in expression of the three transgenes in transduced target cells could not have been predicted by measuring vector DNA integration events. Since transgene expression in target cells is the most common goal of lentiviral transduction, and since methods to quantify transgene expression on the protein level are not always readily available, qRT-PCR based on a nucleotide sequence included in the transcript provides a useful tool for titering novel recombinant lentiviruses.

Cytokine imbalance in hyper-IgE syndrome: reduced expression of transforming growth factor beta and interferon gamma genes in circulating activated T cells

Hyper-IgE syndrome (HIES) is a primary immunodeficiency disease characterized by recurrent infections and marked immunoglobulin (Ig)E elevation. To assess the proper T-cell defects of HIES, the cytokine profile of naturally activated T cells was compared between HIES, atopic dermatitis and chronic granulomatous disease (CGD). Intracellular flow cytometric analysis after in vitro stimulation showed no difference in the proportion of interferon (IFN)gamma- or interleukin 4 (IL-4)-producing T cells among these diseases. Quantitative polymerase chain reaction (PCR) for the cytokine genes was performed using circulating highly fractionated HLA-DR+ and HLA-DR- T cells. The IFNgamma/IL-4 or IFNgamma/IL-10 ratios were lower in HLA-DR+ T cells of HIES than in CGD (P = 0.0106, 0.0445), but did not differ between HIES and atopy. The transforming growth factor-beta (TGFbeta)/IL-4 ratio in HLA-DR+ T cells of HIES was lower than that of atopy (0.0106) or CGD (0.0062). The TGFbeta/IL-4 ratio in HLA-DR- T cells of HIES was also lower than that of atopy (0.0285). Stepwise logistic regression analysis identified TGFbeta/IL-4 ratios in HLA-DR+ (0.0001) or HLA-DR- (0.0086) T cells as the most powerful parameters to distinguish HIES from atopy and/or CGD. Serum IgE levels negatively correlated with IFNgamma/IL-4 (0.0108), IFNgamma/IL-10 (0.0254), or TGFbeta/IL-4 (0.0163) ratios in HLA-DR+, but not HLA-DR-, T cells. These results suggested that the in vivo activated T cells of HIES did not sufficiently express the IFNgamma and TGFbeta genes, which could affect IL-4-dependent IgE production. The reduced TGFbeta expression may involve the indigenous T-cell defects of HIES.

Titering lentiviral vectors: comparison of DNA, RNA and marker expression methods

To better characterize lentiviral vector supernatants, we compared three methods of titer assessment. These titer methods include assessment of vector RNA sequences in supernatants, DNA sequences in transduced cells, and vector expression in transduced cells (using a vector which expressed the green fluorescence protein, GFP). For analysis of RNA and DNA, we developed a real-time PCR method for detecting the lentiviral packaging sequence and used this methodology to quantitate the number of vector sequences. Vector expression was assessed by flow cytometric analysis for GFP. As functional titers (DNA and GFP expression titers) are dependent on transduction efficiency, we calculated the titer of a lentiviral vector, RRL-CMV-GFP, after transduction of 293, HeLa, or Mus dunni cells. Genomic DNA was extracted at 4 and 14 days after transduction and the number of vector DNA molecules was determined against a plasmid standard. Of the three cell lines tested, 293 cells provided the highest rate of transduction (PCR estimated DNA titer for RRL-CMV-GFP vector was 2.52 +/- 0.25 x 10(6) molecules/ml at 14 days, and 2.31 +/- 0.15 x 10(6) molecules/ml at 4 days). When titer was calculated based on GFP expression, the highest titer was also obtained on 293 cells (0.26 +/- 0.04 x 10(6) TU/ml at 14 days, and 0.24 +/- 0.03 +/- 10(6) TU/ml at 4 days). The titers obtained by GFP expression assay were approximately one log lower than those obtained by DNA analysis suggesting that variability in vector expression may underestimate titer. Measurement of RNA titers directly from vector supernatants against a plasmid standard indicated that the RNA titers are substantially higher than the DNA (approximately 10(3)-fold) and GFP titers (approximately 10(4)-fold). To show that the lentiviral probe and primers could be used for titering a variety of lentiviral vectors, we have also used the real-time PCR method to determine the DNA titers of two other HIV1 derived vectors, RRL-PGK-GFP (6.1 +/- 1.4 x 10(5) molecules/ml), and SMPU-RRE-BN (1.26 +/- 0.2 x 10(6) molecules/ml). We conclude that of the three methods tested, titers assessed by DNA analysis of transduced cells provide the most reliable estimate of functional titers as these are least likely to be influenced by factors, such as defective interfering particles and vector expression levels. The real-time PCR method described offers a reproducible method for lentiviral titering and can be applied to a wide variety of vectors, regardless of transgene.

Inhibitor for advanced glycation end products formation attenuates hypertension and oxidative damage in genetic hypertensive rats

OBJECTIVE

A recent study demonstrated that free radicals were involved in the maintenance of hypertension in stroke-prone spontaneously hypertensive rats (SHRSP). Advanced glycation end-products (AGEs) accumulate progressively in the vasculature with ageing, and have been identified to be relevant mediators for various vascular complications. To elucidate the role of AGEs in genetic hypertension, we investigated the effect of OPB-9195, a novel inhibitor of AGEs, on hypertension and oxidative damage in SHRSP.

METHODS

Five-week-old male SHRSP were divided into a control group, fed a control diet and two, OPB-9195, (+/-)-2-isopropylidenehydrazono-4-oxo-thiazolidin-5-ylacetanilide, treatment groups, fed a diet supplemented with OPB-9195 at the concentration of 0.5 (OPB-L) or 2 mg/g (OPB-H) mixed chow for 10 weeks.

RESULTS

The plasma of OPB-9195-treated SHRSP had lower levels of glycated albumin as compared with that of control SHRSP. OPB-9195 lowered the systolic blood pressure (SBP) by the fourth week of administration, and this effect was maintained throughout the study. We also confirmed SBP and diastolic blood pressure (DBP) rhythms, monitored by telemetry, were significantly lower in the OPB-H group than in the control group. Urinary nitric oxide (NO) excretion as well as the expression of endothelial NO synthase (eNOS) mRNA, and eNOS activity in the aorta were significantly increased in OPB-9195-treated groups compared with the control group. The levels of 8-hydroxydeoxyguanosine (8-OHdG), produced from deoxyguanosine under conditions of oxidative stress, in the urine of OPB-9195-treated SHRSP was significantly lower than in the control SHRSP. We also confirmed that the expression of glutathione peroxidase in the aorta was significantly increased in OPB-9195 treated SHRSP.

CONCLUSIONS

Because long-term administration of a AGEs inhibitor reduces blood pressure and oxidative damage in SHRSP, this study suggests a role for AGEs in the progression or maintenance of hypertension and related diseases in genetic hypertension.

New methods to titrate EIAV-based lentiviral vectors

Ideally, gene transfer vectors used in clinical protocols should only express the gene of interest. So far most vectors have contained marker genes to aid their titration. We have used quantitative real-time PCR to titrate equine infectious anemia virus (EIAV) vectors for gene therapy applications. Viral RNA was isolated from vector preparations and analyzed in a one-step RT-PCR reaction in which reverse transcription and amplification were combined in one tube. The PCR assay of vector stocks was quantitative and linear over four orders of magnitude. In tandem, the integration efficiency of these vectors has also been determined by real-time PCR, measuring the number of vector genomes in the target cells. We have found that these methods permit reliable and sensitive titration of lentiviral vectors independent from the expression of a transgene. They also allow us to determine the integration efficiency of different vector genomes. This technology has proved very useful, especially in the absence of marker genes and where vectors express multiple genes.

Real-time PCR in virology

The use of the polymerase chain reaction (PCR) in molecular diagnostics has increased to the point where it is now accepted as the gold standard for detecting nucleic acids from a number of origins and it has become an essential tool in the research laboratory. Real-time PCR has engendered wider acceptance of the PCR due to its improved rapidity, sensitivity, reproducibility and the reduced risk of carry-over contamination. There are currently five main chemistries used for the detection of PCR product during real-time PCR. These are the DNA binding fluorophores, the 5' endonuclease, adjacent linear and hairpin oligoprobes and the self-fluorescing amplicons, which are described in detail. We also discuss factors that have restricted the development of multiplex real-time PCR as well as the role of real-time PCR in quantitating nucleic acids. Both amplification hardware and the fluorogenic detection chemistries have evolved rapidly as the understanding of real-time PCR has developed and this review aims to update the scientist on the current state of the art. We describe the background, advantages and limitations of real-time PCR and we review the literature as it applies to virus detection in the routine and research laboratory in order to focus on one of the many areas in which the application of real-time PCR has provided significant methodological benefits and improved patient outcomes. However, the technology discussed has been applied to other areas of microbiology as well as studies of gene expression and genetic disease.

Quantitative monitoring of circulating Epstein-Barr virus DNA for predicting the development of posttransplantation lymphoproliferative disease

Epstein-Barr virus (EBV)-DNA was quantitatively measured to assess posttransplantation virus reactivation by real-time polymerase chain reaction (PCR). In the first retrospective analysis of a 7-year-old boy with lymphoproliferative disease (LPD) after an unrelated cord blood transplantation, serum EBV-DNA progressively increased to 4 x 10(5) copies/mL. EBV load was then prospectively monitored in peripheral blood from posttransplantation patients. The second case was an 8 year-old boy with aplastic anemia who received a CD34+ cell transplantation. This patient died of LPD with the progression of pulmonary nodules. EBV-DNA increased to 4 x 10(4) copies/mL after the control of cytomegalovirus reactivation. On the other hand, EBV-DNA was undetectable (<200 copies/mL) in the series of all 58 samples from 10 patients who did not develop LPD after hematopoietic stem cell transplantation. Sequential monitoring of circulating EBV-DNA by quantitative PCR may be a useful indicator for predicting the development of posttransplantation LPD.

Rapid determination of adenoviral vector titers by quantitative real-time PCR

Replication defective adenoviruses have been used as vectors in a variety of settings including gene transfer, gene manipulation, and functionality studies. A quantitative real-time PCR-based assay is described for rapid determination of physical titers of recombinant adenovirus vectors. This method is based on amplification of a 77 bp fragment located near the left end of the adenovirus type 5 genome. Evaluation of this method demonstrated that it is simple, sensitive and reproducible, and has a dynamic range of quantitation over 5 logs. This assay is applicable to purified adenovirus as well as vectors prepared by simple cell lysis procedure, requiring only a small amount of starting material. The simplicity and short turn-around time of this assay should facilitate rapid titer determination for a large collection of adenoviral vectors.

Packaging cell line DNA contamination of vector supernatants: implication for laboratory and clinical research

Investigators conducting retroviral gene therapy trials are required to monitor for the presence of replication-competent retrovirus (RCR). The required testing utilizes a combination of biologic assays and molecular tests using PCR. In the course of a human clinical gene therapy trial, we detected 4070A viral envelope sequences in CD34(+) peripheral blood stem cells 2 days after transduction using a PCR-based assay, suggesting the presence of RCR. The supernatant and producer cells used for vector generation had been negative in extensive screening using the extended S(+)/L(-) assay. The presence of a replication-competent virus was subsequently excluded by a combination of biologic and PCR analyses. The source of the 4070A viral envelope sequences was determined to be packaging cell line DNA in the vector supernatant. The analysis of a variety of vector supernatants by quantitative real-time PCR revealed 4070A envelope DNA sequences from the packaging cell line in concentrations equivalent to approximately 50-500 focus-forming units per milliliter of wild-type 4070A virus. When PCR was performed after reverse transcriptase treatment of supernatant (i.e., assessing both RNA and DNA content), 4070A envelope sequence concentrations ranged from 10(2) to 3.5 x 10(3) focus-forming units per milliliter of wild-type 4070A virus. Our data indicate that PCR should not be used to analyze transduced cells for RCR within the first 2 weeks of vector exposure. Furthermore, investigators using PCR to analyze transduction efficiency shortly after vector exposure may experience false-positive findings.

Expansion of tropism of a feline parvovirus to target a human tumor cell line by display of an alpha(v) integrin binding peptide on the capsid

The autonomous parvoviruses are small, non-enveloped, single strand DNA viruses. They occur in many species and they have oncolytic properties. We are modifying the capsid of feline panleukopenia virus (FPV), a parvovirus which normally infects feline cells, with the goal of targeting human tumor cells for potential cancer therapy. Using recombinant viruses transducing a luciferase reporter, we show that insertion of a cyclically constrained, integrin-binding peptide at an exposed position on the FPV capsid enables transduction of an alpha(v) integrin-expressing human rhabdomyosarcoma cell line (Rh18A). These cells were not transduced by virus with the unmodified FPV capsid. Transduction of Rh18A was specifically inhibited by an alpha(v) integrin blocking antibody. However, other human tumor lines expressing alpha(v) integrins were not transduced by virus with either the modified or unmodified capsid. We conclude that modification of the FPV capsid to bind alpha(v) integrins can contribute to, but is not generally sufficient for, redirecting infection to human tumor cells. The permissiveness of Rh18A cells presumably involves additional factors unique to this line among various human cell lines tested.

Phytoestrogens attenuate oxidative DNA damage in vascular smooth muscle cells from stroke-prone spontaneously hypertensive rats

OBJECTIVES

A recent study demonstrated that reactive oxygen species (ROS) were involved in the maintenance of hypertension in stroke-prone spontaneously hypertensive rats (SHRSP). However, the role of oxidative stress in hypertension and its related diseases in SHRSP remains unknown. To determine whether phytoestrogens attenuate oxidative DNA damage in vascular smooth muscle cells (VSMC) from SHRSP and Wistar-Kyoto (WKY) rats, we investigated the effect of daidzein, genistein and resveratrol on oxidative DNA damage in VSMC, induced by advanced glycation end-products (AGEs).

METHODS

VSMC were treated with AGEs in the presence or absence of phytoestrogens for the indicated time. Cellular degeneration induced by AGEs was characterized in terms of intracellular oxidant levels, intracellular total glutathione (GSH) levels, mRNA expression for gamma-glutamylcysteine synthetase (GCS), and a new marker of oxidative stress, 8-hydroxy-2'-deoxyguanosine (8-OHdG) contents.

RESULTS

AGEs stimulated 8-OHdG formation in VSMC in a time- and dose-dependent manner. We also confirmed that VSMC from SHRSP were more vulnerable to oxidative stress induced by AGEs, than VSMC from WKY rats. Daidzein, genistein or resveratrol reduced AGEs-induced 8-OHdG formation in a dose-dependent manner. The preventive effects of phytoestrogens on 8-OHdG formation remarkably paralleled changes in the intracellular oxidant levels in VSMC following AGEs treatment. We further demonstrated that phytoestrogens increase intracellular total GSH level in VSMC. Increased GSH synthesis was due to enhanced expression of the rate-limiting enzyme for GSH synthesis, GCS. Phytoestrogens-stimulated total GSH level in VSMC could lead to decreased intracellular oxidant levels, and thus prevent oxidative DNA damage, induced by AGEs. The phytoestrogens are powerful antioxidants able to interfere with AGEs-mediated oxidative DNA damage of VSMC, and are potentially useful against vascular diseases where ROS are involved in hypertension.

Protective effect of inducible type nitric oxide synthase against intracellular oxidative stress caused by advanced glycation end-products in vascular smooth muscle cells from stroke-prone spontaneously hypertensive rats

OBJECTIVE

A recent study demonstrated that free radicals were involved in the maintenance of hypertension in stroke-prone spontaneously hypertensive rats (SHRSP). However, the role of oxidative stress in hypertension and its related diseases in SHRSP remains unknown. On the other hand, advanced glycation end-products (AGEs) accumulate progressively in the vasculature with ageing, and have been identified to be as relevant mediators for various vascular complications. To elucidate whether nitric oxide (NO) produced by inducible type NO synthase (iNOS) in vascular smooth muscle cells (VSMC) taken from SHRSP and Wistar-Kyoto rats (WKY) attenuate AGEs-induced oxidative stress, we investigated the effect of NO donors and iNOS-induction in VSMC on intracellular oxidant level caused by AGEs.

METHODS

The cells preincubated with or without NO donor, S-nitroso-n-acetylpenicillamine (SNAP) or 3-morpholinosydnonimine (SIN-1), IL-1beta and/or N(G)-monomethyl-L-arginine monoacetate (L-NMMA), were treated with AGEs, and the intracellular oxidant levels, total glutathione (GSH) levels, and gamma-glutamylcysteine synthetase (GCS) mRNA were determined. We also determined the expression of an iNOS in VSMC from SHRSP and WKY.

RESULTS

The intracellular oxidant level of VSMC was induced by AGEs in a dose-dependent manner. NO donor dose-dependently reduced AGEs-stimulated intracellular oxidant level. Treatment with IL-1beta reduced the AGEs-stimulated intracellular oxidant level through increased NO production, whilst inhibition of NO production by L-NMMA reduced the inhibitory effect of IL-1beta. We also confirmed that NO production as well as the expression of iNOS mRNA and the protein itself were significantly decreased in response to IL-1beta in VSMC from SHRSP compared with WKY. We also confirmed that total GSH levels, decreased by AGEs, were restored by stimulation with IL-1beta. Increased GSH synthesis was due to enhanced expression of the rate-limiting enzyme for GSH synthesis, GCS. These results indicate that NO release, produced by iNOS in VSMC in response to cytokines, might play a protective role against AGEs-stimulated oxidative stress in VSMC. This protective effect of NO is decreased in SHRSP compared to WKY.

Resveratrol inhibits AGEs-induced proliferation and collagen synthesis activity in vascular smooth muscle cells from stroke-prone spontaneously hypertensive rats

Advanced glycation end-products (AGEs) of plasma proteins and/or matrix proteins are candidate mediators for various vascular complications such as atherosclerosis. We previously reported a significantly larger accumulation of AGEs of the aorta in stroke-prone spontaneously hypertensive rats (SHRSP) than in age-matched Wistar-Kyoto rats (WKY). In this study, we examined the effects of AGEs on vascular smooth muscle cells (VSMC) from SHRSP and WKY rats. We also studied the in vitro effects of resveratrol (3, 4',5-trihydroxystilbene), a natural phytestrogen, on VSMC proliferation, DNA synthesis, and collagen synthesis activity in SHRSP-VSMC. AGEs accelerated the proliferation of SHRSP- or WKY-VSMC in a time- and dose-dependent manner. VSMC from SHRSP were more sensitive to AGEs than VSMC from normotensive WKY. AGEs also significantly increased DNA synthesis and prolyl hydroxylase activity, a marker for collagen synthesis, in SHRSP-VSMC. AGEs-induced increases in TGF-beta1 mRNA in SHRSP-VSMC were significantly greater than in WKY-VSMC. Resveratrol inhibited AGEs-stimulated proliferation, DNA synthesis, and prolyl hydroxylase activity in SHRSP-VSMC in a dose-dependent manner. ICI 182780, a specific estrogen receptor antagonist, partly blocked the inhibitory effects of resveratrol on AGEs-stimulated proliferation, DNA synthesis, and prolyl hydroxylase activity. Resveratrol significantly inhibited AGEs-induced TGF-beta1 mRNA increases in a dose-dependent manner. Thus, resveratrol may confer protective effects on the cardiovascular system by attenuating vascular remodeling and may be clinically useful as a safer substitute for feminizing estrogens in preventing cardiovascular disease.

Accurate estimation of transduction efficiency necessitates a multiplex real-time PCR

Transduction efficiency can be easily monitored during pre-clinical trials by inclusion of marker genes. However, the use of such marker genes should be avoided in the final clinical gene therapy application since their products are often immunogenic, making it difficult to monitor transduction, especially if the vector is applied in vivo. In these cases PCR-based methods like the real-time PCR might provide a powerful tool to estimate biodistribution. To investigate the accuracy of this method, we have developed and tested a real-time PCR assay for the quantification of the enhanced green fluorescent protein (EGFP) gene and compared the results with transduction efficiencies estimated by FACS analysis. Although our real-time PCR assay itself was characterized by a high precision over a wide dynamic range of quantification, significant differences in the transduction efficiency compared with FACS data were initially observed. Accurate determination could only be achieved using an optimized multiplex real-time PCR assay, which allows the simultaneous calculation of cell number and EGFP copy number in the same tube. In view of future needs for methods allowing precise and accurate analysis of biodistribution in gene therapy trials, our data highlight the necessity critically to check both parameters in the implemented assay.