Priming Th1 immunity to viral core particles is facilitated by trace amounts of RNA bound to its arginine-rich domain

Particulate hepatitis B core Ag (C protein) (HBcAg) and soluble hepatitis B precore Ag (E protein) (HBeAg) of the hepatitis B virus share >70% of their amino acid sequence and most T and B cell-defined epitopes. When injected at low doses into mice, HBcAg particles prime Th1 immunity while HBeAg protein primes Th2 immunity. HBcAg contains 5-20 ng RNA/microg protein while nucleotide binding to HBeAg is not detectable. Deletion of the C-terminal arginine-rich domain of HBcAg generates HBcAg-144 or HBcAg-149 particles (in which >98% of RNA binding is lost) that prime Th2-biased immunity. HBcAg particles, but not truncated HBcAg-144 or -149 particles stimulate IL-12 p70 release by dendritic cells and IFN-gamma release by nonimmune spleen cells. The injection of HBeAg protein or HBcAg-149 particles into mice primes Th1 immunity only when high doses of RNA (i.e., 20-100 microg/mouse) are codelivered with the Ag. Particle-incorporated RNA has thus a 1000-fold higher potency as a Th1-inducing adjuvant than free RNA mixed to a protein Ag. Disrupting the particulate structure of HBcAg releases RNA and abolishes its Th1 immunity inducing potency. Using DNA vaccines delivered intradermally with the gene gun, inoculation of 1 microg HBcAg-encoding pCI/C plasmid DNA primes Th1 immunity while inoculation of 1 microg HBeAg-encoding pCI/E plasmid DNA or HBcAg-149-encoding pCI/C-149 plasmid DNA primes Th2 immunity. Expression data show eukaryotic RNA associated with HBcAg, but not HBeAg, expressed by the DNA vaccine. Hence, codelivery of an efficient, intrinsic adjuvant (i.e., nanogram amounts of prokaryotic or eukaryotic RNA bound to arginine-rich sequences) by HBcAg nucleocapsids facilitates priming of anti-viral Th1 immunity.

Adenovirus induced acute hepatitis in non-human primates after liver-directed gene therapy

OBJECTIVE

To define the mechanism of acute hepatitis in non-human primates after liver directed gene therapy.

METHODS

Differences in immune response exhibited by 8 rhesus monkeys receiving adenovirus (Ad) or lipofectamine-mediated gene transfer by various routes, the time course, and the nature of the specific immune responses to both adenoviral vectors and transgene products were studied using HE staining (H&E) and immunohistochemical staining.

RESULTS

The monkeys developed mild to moderate acute hepatitis 1 to 3 weeks after intravenous or intrabiliary injection of first generation replication-defective adenoviruses carrying the Escherichia coli lacZ gene. This was accompanied by adenovirus-mediated T-cell proliferation and neutralizing antibodies to the adenovirus. Increased numbers of CD3(+), CD4(+) and CD8(+) T-lymphocytes were detected in the diseased livers, while B-lymphocytes were absent. Hepatocytes demonstrated increased expression of beta 2-microglobulins (beta 2-MG) and HLA-DR antigens in the plasma membranes. The development of acute hepatitis and the accompanying immune abnormalities were delayed in immunosuppressed monkeys until after the discontinuation of immunosuppressive therapy. The monkeys infused with Ad. CMVluc showed more significant and longer durations of hepatitis than the monkeys infused with adenoviruses carrying the lacZ gene. Lipofectamine-mediated gene transfer was inefficient. There was neither lacZ expression nor significant immune response in the liver of monkeys infused with lipofectamine via the portal vein or the common bile duct.

CONCLUSION

Immune response to the hepatocytes in liver directed gene therapy is MHC class I restricted and T-cell mediated. Both adenoviral vectors and foreign genes are related to the liver damage. Mild to moderate hepatic inflammation seen with the E-1 deleted vector is reversible. Immunosuppression regimens may prolong transgene expression and delay the development of acute adenoviral hepatitis.

New prospectives of prostate cancer gene therapy: molecular targets and animal models

Prostate cancer is the most common cancer and the second leading cause of cancer-related death among North American men. The low cure rate for prostate cancer is associated with the fact that many patients have metastatic disease at the time of disease presentation. Currently available therapeutic modalities for prostate cancer, such as surgery, radiation, hormone therapy, and chemotherapy, have failed to cure patients because these therapies are not sufficiently tumor-specific, resulting in dose-limiting toxicity. Therefore, gene therapy may offer great promise in this regard. In this article, we summarize current advances in gene therapy technologies for the treatment of cancer in general, and future prospects for treatment of human prostate cancer metastasis. We specifically emphasize current studies for improvement, both in the efficiency and the specificity of viral and nonviral vectors, and restricted transgene expression in tumors, to achieve selective targeting with minimized host organ toxicity, based on the molecular understanding of potential regulatory differences between normal and tumor cells. Cell and animal models used to study prostate cancer growth, invasion, and metastasis, and their usefulness in preclinical evaluation of therapeutic vectors in the treatment of prostate cancer skeletal metastasis are also discussed.

Cationic liposome-mediated gene delivery in vivo

Several improvements have been made in liposomal delivery, thus making this technology potentially useful for treatment of certain diseases in the clinic. Success in non-viral delivery is complicated and requires optimization of several components. These components include nucleic acid purification, plasmid design, formulation of the delivery vehicle, administration route and schedule, dosing, detection of gene expression, and others. With further improvements, broad use of non-viral delivery systems to treat human disorders should be possible.

Immunotherapy with recombinant SFV-replicons expressing the P815A tumor antigen or IL-12 induces tumor regression

Replicons based on alphaviruses are emerging as candidate vectors for vaccination and gene therapy purposes. We have reported previously that mice vaccinated with a recombinant Semliki Forest virus (a member of the alphavirus genus) carrying the gene encoding the P815A tumor antigen (rSFV/E-P1A) were protected against a lethal challenge with the P815 tumor. In this study we investigated the anti-tumor therapeutic efficacy of rSFV/E-P1A or rSFV expressing the cytokine interleukin 12 (rSFV/IL12) on Day 5-established tumors. The results show that both antigen-specific and cytokine-mediated rSFV treatments exhibited a significant effect on P815 tumor growth, by delaying tumor progression and even inducing complete tumor regressions in several mice. The therapeutic potency of these vectors was dependent on the size of the treated tumor, as treatment of mice bearing larger tumors showed lower efficacy. In addition, rSFV treatment resulted in long-term immunity as observed by the lack of tumor recurrence in the majority of tumor-regressing mice after rechallenge with the tumor. Furthermore, the anti-tumor therapeutic effect was only achieved by local intratumoral injection of rSFV, as treatment by injection in the contralateral site resulted in tumor progression comparable to control-untreated mice. Accordingly, expression of a rSFV-RNA was localized to the tumor and draining lymph node. These results further demonstrate the potential of rSFV replicons as tumor therapeutic agents.

Tumor-directed targeting of liposomes

Tumor-specific targeting is a critical goal in the research area of liposomal drug delivery. Identification of the specific interactions between ligands and target tumor cells is a principle prerequisite in achieving this goal. Generally, tumor cells aberrantly express tumor-associated antigens that can be utilized as appropriate target molecules. Monoclonal antibodies against tumor-associated antigens have been successfully adopted for targeting to various types of cancer cells. The incorporation of humanized monoclonal antibodies or single chain human antibodies, instead of rodent antibodies into immunoliposomes has resulted in better clinical applicability. Tumor-specific ligands other than monoclonal antibodies have also been investigated as in vivo tumor-directing molecules. However, the number of pre-clinical studies of anticancer treatments using tumor-specific liposomal drugs reporting successful targeting and enhanced therapeutic efficacy has been limited. Further refinement of tumor-specific interactions and liposomal formulations will be necessary for the application of the tumor-specific liposomal drug strategy for anticancer chemotherapy or gene therapy.

Zebrafish yolk-specific not really started (nrs) gene is a vertebrate homolog of the Drosophila spinster gene and is essential for embryogenesis

By using retroviral insertional mutagenesis in zebrafish, we have identified a recessive lethal mutation in the not really started (nrs) gene. The nrs mutation disrupts a gene located in linkage group 3 that is highly homologous to the spinster gene identified in Drosophila and to spinster orthologs identified in mammals. In flies, spinster encodes a membrane protein involved in lysosomal metabolism and programmed cell death in the central nervous system and in the ovary. In nrs mutant fish embryos, we detect an opaque substance in the posterior yolk cell extension at approximately 1 day after fertilization. This material progressively accumulates and by 48 hr after fertilization fills the entire yolk. By day 3 of embryogenesis, mutant embryos are severely reduced in size compared with their wild-type siblings and they die a few hours later. By in situ hybridization, we show that the nrs mRNA is expressed in the yolk cell at the time the mutant phenotype becomes apparent. In wild-type embryos, nrs message is present maternally and zygotically throughout embryogenesis and is also detected in adult animals. In nrs homozygous mutant embryos, nrs transcripts are undetectable at the time the phenotype becomes apparent, indicating that the retroviral insertion has most likely abolished expression of the nrs gene. Finally, the nrs phenotype can be partially rescued by microinjection of nrs encoding DNA. These results suggest that the nrs mutation affects an essential gene encoding a putative membrane-bound protein expressed specifically in the yolk cell during zebrafish embryogenesis.

Fate of plasmid DNA encoding infectious bursal disease virus VP2 capsid protein gene after injection into the pectoralis muscle of the chicken

The objective of this study was to determine whether recombinant plasmid DNA injected intramuscularly into chickens expressed the gene of interest in vivo and could be subsequently detected in primary and secondary lymphoid tissues with polymerase chain reaction (PCR). The VP2 capsid protein gene of the standard challenge strain (STC) of infectious bursal disease virus (IBDV) was cloned into a eukaryotic plasmid, and purified DNA was prepared. Fourteen 2-wk-old chickens were injected in the pectoral musculature with 500 microg of plasmid DNA dissolved in sterile PBS. Seven chickens were similarly injected with PBS alone. Pectoral muscle, thymus, spleen, bursa of Fabricius, and cecal tonsils were collected at 12, 24, 36, 48, 72, 96, and 168 h postinjection for detection of protein expression (in muscle) and to extract total DNA for PCR amplification of the VP2 capsid gene. Expression of VP2 was demonstrated in muscle tissue at 12 and 24 h postinjection by using an indirect immunofluorescence assay. PCR amplification with primers specific for the VP2 gene showed that the DNA was present in the thymus, spleen, and bursa of Fabricius but not in cecal tonsils. These results demonstrate that plasmid DNA injected directly into the pectoral muscle of chickens is transcribed and translated at the injection site and promptly distributed to primary and secondary lymphoid tissues.

Role of intracellular cationic liposome-DNA complex dissociation in transfection mediated by cationic lipids

The cationic lipid-mediated gene transfer process involves sequential steps: internalization of the cationic lipid-DNA complexes inside the cells via an endocytosis-like mechanism, escape from endosomes, dissociation of the complex, and finally entry of free DNA into the nucleus. However, cationic lipid-DNA complex dissociation in the cytoplasm and the ability of the subsequently released DNA to enter the nucleus have not yet been demonstrated. In this report we showed, using confocal laser scanning analysis, that microinjection of a double fluorescent-labeled cationic lipid-pCMV-LacZ plasmid complex into the cytoplasm of HeLa cells results in efficient complex dissociation. However, the released DNA did not enter the nucleus, and no significant transfection could be detected. In contrast, nuclear microinjection of the cationic lipid-pCMV-LacZ plasmid complex resulted in efficient complex dissociation and transfection of all the cells. Taken together, the data suggest that intracellular dissociation of the cationic lipid-DNA complex is not a limiting step for transfection as previously thought.

The role of antigen in the localization of naive, acutely activated, and memory CD8(+) T cells to the lung during influenza pneumonia

The role of Ag in the recruitment and localization of naive, acutely activated, and memory CD8(+) T cells to the lung during influenza infection was explored using TCR-transgenic (Tg) mice. Naive, Thy1.2(+)CD8(+) OT-I TCR-Tg cells were primed and recruited to the lung after transfer into congenic Thy1.1(+) recipients challenged with a genetically engineered influenza virus (influenza A/WSN/33 (WSN)-OVA(I)) containing the K(b) restricted OVA(257-264) epitope (siinfekl) in the viral neuraminidase stalk. However, if the transferred animals were infected with a similar influenza virus that expressed an irrelevant K(b) epitope (WSN-PEPII), no TCR-Tg T cells were detectable in the lung, although they were easily visible in the lymphoid organs. Conversely, there were substantial numbers of OT-I cells found in the lungs of WSN-PEPII-infected mice when the animals had been previously, or were concurrently, infected with a recombinant vaccinia virus expressing OVA. Similar results were obtained with nontransgenic populations of memory CD8(+) T cells reactive to a murine gamma-herpesvirus-68 Ag. Interestingly, the primary host response to the immunodominant influenza nucleoprotein epitope was not affected by the presence of memory or recently activated OT-I T cells. Thus, although Ag is required to activate the T cells, the subsequent localization of T cells to the lung during a virus infection is a property of recently activated and memory T cells and is not necessarily driven by Ag in the lung.

A crucial role of macrophages in the immune responses to oral DNA vaccination against hepatitis B virus in a murine model

In the previous study, we had shown that live oral vaccination with Salmonella typhimurium delivering plasmid DNA-HBsAg (oral DNA vaccine) evoked a vigorous T cell response and a weak antibody response with predominant subclass IgG2a in mice, suggesting a significant involvement by professional antigen presenting cells (APC). In the present study, this possibility was further studied by infecting peritoneal macrophages (MPhi) with the oral DNA vaccine. Although, the infected cells could only express low level of the viral antigen, they nevertheless stimulated a vigorous lymphocyte proliferation of splenocytes from immune mice, induced these cells to elaborate interferon-gamma and stimulated development of HBV-specific cytotoxicity against target cells expressing the viral antigen. Infusion of the infected MPhi evoked a vigorous Th 1 and cytotoxic T lymphocyte (CTL) response and a weak IgG2a antibody response in mice, which was essentially the same as response to the oral DNA vaccine. In contrast, recombinant protein vaccine evoked a vigorous IgG1 antibody response and a weak T cell response. While, given intramuscularly, the same plasmid DNA vaccine as that contained in the oral DNA vaccine evoked a vigorous IgG1 antibody response and a moderate T cell response in these animals. It was concluded that professional APC may orchestrate the immune response to live oral DNA vaccine and it was of interest to note that different vaccine formulation and routes of administration evoke distinct immune response to HBV.

Gene-trap mutagenesis: past, present and beyond

Although at least 35,000 human genes have been sequenced and mapped, adequate expression or functional information is available for only approximately 15% of them. Gene-trap mutagenesis is a technique that randomly generates loss-of-function mutations and reports the expression of many mouse genes. At present, several large-scale, gene-trap screens are being carried out with various new vectors, which aim to generate a public resource of mutagenized embryonic stem (ES) cells. This resource now includes more than 8,000 mutagenized ES-cell lines, which are freely available, making it an appropriate time to evaluate the recent advances in this area of genomic technology and the technical hurdles it has yet to overcome.

Ketamine and its preservative, benzethonium chloride, both inhibit human recombinant alpha7 and alpha4beta2 neuronal nicotinic acetylcholine receptors in Xenopus oocytes

1. Ketamine is a dissociative anaesthetic that is formulated as Ketalar, which contains the preservative benzethonium chloride (BCl). We have studied the effects of pure racemic ketamine, the preservative BCl and the Ketalar mixture on human neuronal nicotinic acetylcholine receptors (nAChRs) composed of the alpha7 subunit or alpha4 and beta2 subunits expressed in Xenopus laevis oocytes. 2. Ketamine inhibited responses to 1 mM acetylcholine (ACh) in both the human alpha7 and alpha4beta2 nAChRs, with IC(50) values of 20 and 50 microM respectively. Inhibition of the alpha7 nAChRs occurred within a clinically relevant concentration range, while inhibition of the alpha4beta2 nAChR was observed only at higher concentrations. The Ketalar formulation inhibited nAChR function more effectively than was expected given its ketamine concentration. The surprising increased inhibitory potency of Ketalar compared with pure ketamine appeared to be due to the activity of BCl, which inhibited both alpha7 (IC(50) value of 122 nM) and alpha4beta2 (IC(50) value of 49 nM) nAChRs at concentrations present in the clinical formulation of Ketalar. 3. Ketamine is a noncompetitive inhibitor at both the alpha7 and alpha4beta2 nAChR. In contrast, BCl causes a parallel shift in the ACh dose-response curve at the alpha7 nAChR suggesting competitive inhibition. Ketamine causes both voltage-dependent and use-dependent inhibition, only in the alpha4beta2 nAChR. 4. Since alpha7 nAChRs are likely to be inhibited during clinical use of Ketalar, the actions of ketamine and BCl on this receptor subtype may play a role in the profound analgesia, amnesia, immobility and/or autonomic modulation produced by this anaesthetic.

Effect of administration of a recombinant adenovirus expressing the genes for IFN-gamma and interleukin-12 on acute murine toxoplasmosis

The effect of recombinant murine interferon-gamma (rMuIFN-gamma) produced from an adenovirus construct on Toxoplasma gondii in tissue culture and on the outcome of a T. gondii infection in mice was determined. Supernatants from AdCMVMuIFN-gamma-infected mouse lung epithelial (MuLE) cells were evaluated for the ability to produce biologically active IFN-gamma by measuring the capacity of the supernatants to activate peritoneal macrophages for killing of T. gondii. The bioactivity of IFN-gamma in supernatants increased with increasing multiplicity of infection (moi). Replication was inhibited 43%, 67%, and 70% by supernatants from MuLE cells infected with AdCMVMuIFN-gamma moi 5, 10, and 50, respectively, (p < 0.01 compared with controls). Bioactivity of IFN-gamma also increased as the length of time after infection increased. T. gondii replication was inhibited 28% and 36%, respectively, by AdCMVMuIFN-gamma-infected MuLE cell supernatants recovered at 24 and 48 h (p < 0.01 compared with control). In vivo administration of AdCMVMuIFN-gamma exhibited 33% mortality by day 9 in mice acutely infected with T. gondii compared with 100% mortality in control mice (p = 0.045). Administration of AdCMVIL-12 reduced mortality to 40% compared with control mice. However, this reduction was not significant (p = 0.08). Overall survival was extended 2 days with AdCMVMuINF-gamma administration and 5 days with AdCMVIL-12. AdCMVMuIFN-gamma in vitro inhibits T. gondii, and in vivo AdCMVMuIFN-gamma and AdCMVIL-12 lead to increased survival in mice.

[Construction and immunogenicity of DNA vaccine encoding secreted form of Ag85B protein of Mycobacterium tuberculosis]

OBJECTIVE

To construct the recombinant eukaryotic plasmid DNA expression vector encoding Mycobacterium tuberculosis antigen 85B (Ag85B) and to investigate its immunogenicity.

METHODS

The gene encoding secreted form of Ag85B was amplified by polymerase chain reaction (PCR) from genome of Mycobacterium tuberculosis H37Ra strain, and was inserted into sites cut with Hind III plus EcoR I of eukaryotic expression vector pcDNA3 after restriction endonuclease digestion. The gene fragment encoding secreted form of Ag85B was inserted into the vector of E. coli JM109 strain and was confirmed by restriction endonuclease digestion. After 4 weeks since BALB/c mice were vaccinated by recombinant eukaryotic expressing vector, dot blotting and ELISA were used to detect the serum antibody against Ag85B and its titer.

RESULTS

Recombinant eukaryotic expressing vector, namely pTB30s, constructed successfully based on the gene encoding secreted form of Mycobacterium tuberculosis Ag85B; pTB30s induced high titer specific antibody against Ag85B in immunized mice.

CONCLUSION

pTB30s as DNA vaccine should be further studied to confirm its stimulating role in cell-mediated immune responses in TB prevention.

Aerosol and lobar administration of a recombinant adenovirus to individuals with cystic fibrosis. I. Methods, safety, and clinical implications

Cystic fibrosis (CF), an autosomal recessive disorder resulting from mutations in the cystic fibrosis trans-membrane conductance regulator (CFTR) gene, is the most common lethal genetic illness in the Caucasian population. Gene transfer to airway epithelium, using adenoviruses containing normal CFTR cDNA, leads to transient production of CFTR mRNA and, in some studies, to correction of the airway epithelial ion transport defect caused by dysfunctional CFTR. Inflammatory responses to the adenoviral vector have been reported, particularly at high viral titers. We evaluated the effects of adenovirus-mediated CFTR gene transfer to airway epithelium in 36 subjects with CF (34 individuals, 2 of whom received two separate doses of vector), 20 by lobar instillation and 16 by aerosol administration. Doses ranged from 8 x 10(6) to 2.5 x 10(10) infective units (IU), in 0.5-log increments. After lobar administration of low doses there were occasional reports of cough, low-grade temperature, and myalgias. At the highest lobar dose (2.5 x 10(9) IU) two of three patients had transient myalgias, fever, and increased sputum production with obvious infiltrates on CT scan. After aerosol administration there were no significant systemic symptoms until the 2.5 x 10(10) IU dose, when both patients experienced myalgias and fever that resolved within 24 hr. There were no infiltrates seen on chest CT scans in any of the patients in the aerosol administration group. There were no consistent changes in pulmonary function tests or any significant rise in serum IgG or neutralizing antibodies in patients from either group. Serum, sputum, and nasal cytokines, measured before and after vector administration, showed no correlation with adenoviral dose. Gene transfer to lung cells was inefficient and expression was transient. Cells infected with the vector included mononuclear inflammatory cells as well as cuboidal and columnar epithelial cells. In summary, we found no consistent immune response, no evidence of viral shedding, and no consistent change in pulmonary function in response to adenovirus-mediated CFTR gene transfer. At higher doses there was a mild, nonspecific inflammatory response, as evidenced by fevers and myalgias. Overall, vector administration was tolerated but transfer of CFTR cDNA was inefficient and transgene expression was transient for the doses and method of administration used here.

Adenovirus-mediated targeted expression of toxic genes to adrenocorticotropin-producing pituitary tumors using the proopiomelanocortin promoter

Management of Cushing's disease remains challenging, despite advances in its diagnosis and treatment. Here, we describe a strategy for targeting the expression of toxic genes to ACTH-producing tumor cells using adenoviral vectors. The POMC promoter was used to express either a marker gene (beta-galactosidase) or a toxic gene [herpes simplex virus thymidine kinase (TK)]. In ACTH-producing AtT20 cells, infection with recombinant adenoviruses containing the POMC promoter (AdPOMCGal; AdPOMCTK) led to high-level gene expression. Stereotactic injection of AdPOMCGal into the rat pituitary resulted in localized expression of the beta-galactosidase transgene in corticotrope cells. Cytotoxicity studies were performed using the TK-containing vectors and treatment with ganciclovir. AdPOMCTK caused greater than 95% cytotoxicity of AtT20 cells at a viral dose (multiplicity of infection, 5 plaque-forming units/cell) that induced minimal toxicity using control viruses. No cellular toxicity was seen using a nonpituitary cell line (T47D breast tumor cells). AtT20 cells transplanted into nude mice induced features of Cushing's syndrome and were used as an in vivo model of ACTH-producing tumors. Injection of the AdPOMCTK virus caused significant regression of the transplanted AtT20 tumors. These studies suggest that the POMC promoter may provide a useful gene therapy strategy for the adjunctive treatment of pituitary tumors causing ACTH-dependent Cushing's syndrome.

Nonviral gene therapy

The last 10 years have seen substantial progress in the development and application of nonviral vectors in gene therapy. Several novel nonviral methods have been developed that approach viruses with respect to transfection efficiency. A variety of nonviral delivery systems that can be used for gene therapy in different clinical settings are also available. In this review article, we will detail all of the major nonviral vectors that are currently used in gene therapy while highlighting some recent developments, particularly the progress towards the understanding of the cellular and in vivo barriers in gene transfer. Recent advancement in achieving sustained and regulated gene expression will also be addressed. Finally, this review will briefly cover targeted gene repair using nonviral delivery systems. Their impact in gene therapy will also be discussed.

Effective generation of very low density lipoprotein receptor transgenic mice by overlapping genomic DNA fragments: high testis expression and disturbed spermatogenesis

The generation of functional transgenes via microinjection of overlapping DNA fragments has previously been reported to be successful, but it is still not a widely applied approach. Here we show that the method is very reliable, and should be considered, in case a single large insert clone of the desired gene is not available. In the present study, two large DNA fragments consisting of overlapping cosmids, together constituting the human very low density lipoprotein receptor (VLDLR) gene (35 kb), were used to generate VLDLR transgenic (VLDLR-Tg) mice. Three transgenic founders were born, of which two (strain #2 and #3) generated transgenic offspring. Using Fiber-FISH analysis, the integration site was shown to contain at least 44 and 64 DNA fragments in mouse strains #2 and #3, respectively. This copy number resulted in integration sites of 1.5 and 2.5 megabase in size. Notably, over 90% of the fragments in both mouse strains #2 and #3 were flanked by their complementary fragment. In line with this observation, Southern blot analysis demonstrated that the correct recombination between fragments predominated in the transgenic insertion. Human VLDLR expression was detected in testis, kidney and brain of both mouse strains. Since this pattern did not parallel the endogenous VLDLR expression, some crucial regulatory elements were probably not present in the cosmid clones. Human VLDLR expression in testis was detected in germ cells up to the meiotic stage by in situ mRNA analysis. Remarkably, in the F1 generation of both VLDLR-Tg mouse strains the testis was atrophic and giant cells were detected in the semineferous tubuli. Furthermore, male VLDLR-Tg mice transmitted the transgene to their progeny with low frequencies. This could imply that VLDLR overexpression in the germ cells disturbed spermatogenesis.

A prime-boost vaccination strategy using naked DNA followed by recombinant porcine adenovirus protects pigs from classical swine fever

Weaned pigs (6-week-old) and 7-day-old pre-weaned piglets were vaccinated with naked plasmid DNA expressing the gp55/E2 gene from classical swine fever virus (CSFV). Both groups of pigs were then given a booster dose of recombinant porcine adenovirus expressing the gp55 gene (rPAV-gp55). Following challenge with CSFV, 100% of weaned pigs and 75% pre-weaned piglets were protected from disease. Weaned pigs given a single dose of rPAV-gp55 were also protected, but showed a slight increase in temperature immediately post-challenge. However, weaned animals given a DNA prime before rPAV-gp55 showed no fluctuation in body temperature following challenge and no pathology in spleen or lymph nodes upon post-mortem. In addition, no CSFV could be re-isolated from the rPAV vaccinated group and from only one pig in the prime-boost group following challenge, suggesting that both vaccination regimes have the potential to reduce or prevent virus shedding following experimental challenge.

Randomized, single-blind, placebo-controlled pilot study of catheter-based myocardial gene transfer for therapeutic angiogenesis using left ventricular electromechanical mapping in patients with chronic myocardial ischemia

BACKGROUND

Catheter-based myocardial gene transfer (GTx) has not been previously tested in human subjects. Accordingly, we performed a pilot study to investigate the feasibility and safety of catheter-based myocardial GTx of naked plasmid DNA encoding vascular endothelial growth factor-2 (phVEGF-2) in patients with chronic myocardial ischemia.

METHODS AND RESULTS

A steerable, deflectable 8F catheter incorporating a 27-guage needle was advanced percutaneously to the left ventricular myocardium of 6 patients with chronic myocardial ischemia. Patients were randomized (1:1) to receive phVEGF-2 (total dose, 200 microgram), which was administered as 6 injections into ischemic myocardium (total, 6.0 mL), or placebo (mock procedure). Injections were guided by NOGA left ventricular electromechanical mapping. Patients initially randomized to placebo became eligible for phVEGF-2 GTx if they had no clinical improvement 90 days after their initial procedure. Catheter injections (n=36) caused no changes in heart rate or blood pressure. No sustained ventricular arrhythmias, ECG evidence of infarction, or ventricular perforations were observed. phVEGF-2-transfected patients experienced reduced angina (before versus after GTx, 36.2+/-2.3 versus 3.5+/-1.2 episodes/week) and reduced nitroglycerin consumption (33.8+/-2.3 versus 4.1+/-1.5 tablets/week) for up to 360 days after GTx; reduced ischemia by electromechanical mapping (mean area of ischemia, 10.2+/-3.5 versus 2.8+/-1.6 cm(2), P=0.04); and improved myocardial perfusion by SPECT-sestamibi scanning for up to 90 days after GTx when compared with images obtained after control procedure. Conclusions-This randomized trial of catheter-based phVEGF-2 myocardial GTx provides preliminary indications regarding the feasibility, safety, and potential efficacy of percutaneous myocardial GTx to human left ventricular myocardium.

Biomaterials for gene delivery: atelocollagen-mediated controlled release of molecular medicines

Over the last decade, increasing attention has been paid to the development of systems to deliver drugs for long periods at controlled rates. Some of these systems can deliver drugs continuously for over one year. However, little effort has been given to developing systems for the controlled release of nucleic acids. Recently, a novel gene transfer method which allows prolonged release and expression of plasmid DNA in vivo in normal adult animals was established. In this system, a biocompatible natural polymer such as collagen or its derivatives acts as the carrier for the delivery of DNA vectors. The biomaterial carrying the plasmid DNA was administered into animals and, once introduced, gradually released plasmid DNA in vivo. A single injection of plasmid DNA/biomaterial produced physiologically significant levels of gene-encoding proteins in the local/systemic circulation of animals and resulted in prolonged biological effects. These results suggest that the biomaterials carrying plasmid DNA may enhance the clinical potency of plasmid-based gene transfer, facilitating a more effective and long-term use of naked plasmid vectors for gene therapy. Furthermore, the biomaterials can be removed surgically, minimizing the effect of gene products if some unexpected side effects should be observed after application. The application of these systems to expand the bioavailability of molecular medicine, including antisense oligonucleotides and adenovirus vectors, and to aid in stem cell transplantation in the context of DNA-based tissue engineering will be discussed.

Feasibility of biolistic gene therapy in burns

Skin is an especially attractive target for genetic manipulation because it is readily accessible and easily monitored for both the presence and the expression of inserted genes. This study was designed to assess the feasibility of particle mediated gene transfer to burned skin and to compare the transfection efficiency, anatomic distribution, and duration of transgene expression achievable in normal versus burned skin. Two days following scald injury of varying depths in 60 degrees C water (10 s: superficial partial; 20 s: deep partial; 40 s: full thickness) reporter gene (beta-galactosidase) constructs were delivered using a gene gun at various helium pressures (200-600 psi) to normal and burned skin. A time course study was performed to examine the kinetics of transgene expression. Animals received a superficial partial thickness burn and were sacrificed 12 h, 1, 3, 5, 7, 14, or 21 days after gene transfer. India Ink injection and immunohistochemistry were used to assess the depth of the scald injury. Transfection efficiency was measured in skin homogenates 24 h after gene transfer by morphometric and chemoluminescent assays. We found that the extent of tissue damage was directly related to the duration of heat source exposure. Reporter gene activity was significantly higher in superficial partial thickness burns compared to normal controls and gradually declined with increasing tissue injury. No activity was seen in the full thickness burn group. Beta-galactosidase activity reached a maximum level 12 h after gene transfer in both normal and superficial partial thickness burned skin with no levels seen after 5 days post-transfection. These findings indicate that particle-mediated gene transfer in thermally injured skin is feasible and may provide a means of introducing biologic agents into injured tissue capable of enhancing bacterial clearance and improving wound healing.

Improvement of mouse beta-thalassemia by electrotransfer of erythropoietin cDNA

OBJECTIVE

A new intramuscular DNA electrotransfer method for erythropoietin (EPO) expression was evaluated in the natural mouse model of human beta-thalassemia (Hbb-thal1) in terms of its ability to reverse the anemia and improve the thalassemic features of erythrocytes.

MATERIALS AND METHODS

Intramuscular injection of small amounts of a plasmid encoding mouse EPO, immediately followed by controlled electric pulses, was used.

RESULTS

This procedure induced very high hematocrit levels in beta-thalassemic mice compared to nonelectrotransferred mice. The hematocrit increase was dose dependent, still increased 4 months after injection of plasmid DNA, and associated with a high transgenic EPO blood level in all mice (up to 2500 mU/mL of plasma). EPO gene electrotransfer not only led to a long-lasting and dose-dependent increase in the hematocrit but also to a 100% increase in the lifespan of erythrocytes of thalassemic mice. This was related to a nearly complete reestablishment of alpha/beta globin chain balance, as demonstrated by a marked decrease in unpaired alpha globin chain. Eight months after the first electrotransfer of pCMV-mEPO plasmid, reinjection of the same construct raised the hematocrit to a level close to that observed following the first electrotransfer.

CONCLUSION

This is the first description of the use of plasmid DNA to achieve long-term improvement in a mouse model of a human genetic disorder.

Linear DNAs concatemerize in vivo and result in sustained transgene expression in mouse liver

The short duration of transgene expression remains a major obstacle for the implementation of nonviral DNA vectors in clinical gene therapy trials. Here, we demonstrate stable, long-term transgene expression in vivo by transfecting a linear DNA expression cassette (LDNA) into mouse liver. Interestingly, despite similar quantities and cellular distribution of injected DNAs in their livers, mice receiving LDNA encoding human alpha1-antitrypsin (hAAT) expressed approximately 10- to 100-fold more serum hAAT than mice injected with closed circular (cc) DNA for a period of 9 months (length of study). Furthermore, when a linear human factor IX expression cassette was delivered to factor IX-deficient mice, sustained serum concentrations of more than 4 microg/ml (80% of normal) of the human clotting factor and correction of the bleeding diathesis were obtained. Southern blot analyses indicate that, unlike ccDNA, LDNA rapidly formed large, unintegrated concatemers in vivo, suggesting that transgene persistence from plasmid-based vectors was influenced by the structure of the vector in transfected cells. No differences in transgene expression or DNA molecular structures were observed when AAV ITRs were included to flank the hAAT expression cassette in both ccDNA- and LDNA-treated animals. Linear DNA transfection provides an approach for achieving long-term expression of a transgene in vivo.