Systemic gene expression after intravenous DNA delivery into adult mice

Elegant studies of transplant-derived repair of cognitive performance

Cholinergic-rich grafts have been shown to be effective in restoring maze-learning deficits in rats with lesions of the forebrain cholinergic projection system. However, the relevance of those studies to developing novel therapies for Alzheimer's disease is questioned.

Gene transfer and expression in progeny after intravenous DNA injection into pregnant mice

Several methods that enable foreign genes to be transferred directly into germ cells and adult animals have been developed, which have stimulated great interest in manipulating genes in vivo. However, there have been no methods available for introducing genes into fetuses. We report here that a single intravenous injection of expression plasmid: lipopolyamine complexes into pregnant mice resulted in successful gene transfer into the embryos. The transgenes thus introduced were expressed in the fetuses and newborn progeny. This simple and new method of gene transfer into embryos will facilitate rapid analysis of transgene effects in the fetuses and will be useful for studying gene-deficient animal models to gain transgene functions at desired stages of embryogenesis.

Neutrophil-mediated tissue injury and its modulation

Neutrophils play a key role in the development of the systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS). Since the lungs are the main target in these syndromes, with adult respiratory distress syndrome (ARDS) as the outcome, extensive research has been undertaken to prevent or mitigate ARDS. As evidence of the involvement of neutrophils in ARDS has accumulated, modulation of their function has become a major goal in terms of a therapeutic approach. In this short review, we sought to update our knowledge about neutrophils. Firstly, we summarized the various stimuli which activate neutrophils. Secondly, we described the different mediators, including cytokines, which are released by neutrophils. Lastly, we discussed the possible modulation of their function. Although we cannot assess the clinical usefulness of biochemical substances merely on the basis of their in vitro effects, understanding these mechanisms is fundamental to the success of the new therapeutic approach which is currently under way.

Neural transplants are grey matters

The lesion and transplantation data cited by Sinden et al., when considered in tandem, seem to harbor an internal inconsistency, raising questions of false localization of function. The extrapolation of such data to cognitive impairment and potential treatment strategies in Alzheimer's disease is problematic. Patients with focal basal forebrain lesions (e.g., anterior communicating artery aneurysm rupture) might be a more appropriate target population.

Immunobiology of neural transplants and functional incorporation of grafted dopamine neurons

In contrast to the views put forth by Stein & Glasier, we support the use of inbred strains of rodents in studies of the immunobiology of neural transplants. Inbred strains demonstrate homology of the major histocompatibility complex (MHC). Virtually all experimental work in transplantation immunology is performed using inbred strains, yet very few published studies of immune rejection in intracerebral grafts have used inbred animals.

Local and global gene therapy in the central nervous system

For focal neurodegenerative diseases or brain tumors, localized delivery of protein or genetic vectors may be sufficient to alleviate symptoms, halt disease progression, or even cure the disease. One may circumvent the limitation imposed by the blood-brain barrier by transplantation of genetically altered cell grafts or focal inoculation of virus or protein. However, permanent gene replacement therapy for diseases affecting the entire brain will require global delivery of genetic vectors. The neurotoxicity of currently available viral vectors and the transient nature of transgene expression invivomust be overcome before their use in human gene therapy becomes clinically applicable.

Neural grafting in human disease versus animal models: Cautionary notes

Over the past two decades, research on neural transplantation in animal models of neurodegeneration has provided provocative in sights into the therapeutic use of grafted tissue for various neurological diseases. Although great strides have been made and functional benefits gained in these animal models, much information is still needed with regard to transplantation in human patients. Several factors are unique to human disease, for example, age of the recipient, duration of disease, and drug interaction with grafted cells; these need to be explored before grafting can be considered a safe and effective therapeutic tool.

Building a rational foundation for neural transplantation

The neural transplantation research described by Sinden and colleagues provides part of the rationale for the clinical application of neural transplantation. The authors are asked to clarify their view of the role of the cholinergic system in cognition, to address extrahippocampal damage caused by transient forebrain ischemia, and to consider the effects of delayed neural degeneration in their structure-function analysis.

Intraretrosplenial grafts of cholinergic neurons and spatial memory function

The transplantation of cholinergic neurons into the hippocampal formation has been well characterized. We describe our studies on the effects of cholinergic transplants in the retrosplenial cortex. These transplants were capable of ameliorating spatial navigation deficits in rats with septohippocampal lesions. In addition, we provide evidence for the modulation of transplanted neurons by the host brain.

Gene therapy and neural grafting: Keeping the message switched on

A major problem in developing an effective gene therapy for the nervous system lies in understanding the principles that maintain or turn off the expression of genes following their transfer into the CNS.

Therapeutic neural transplantation: Boon or boondoggle?

Despite reports of recovery of function after neural transplantation, the biological interactions between transplanted neurons and the host brain that are necessary to mediate recovery are unclear at present. One source of confusion is in the variety of models and protocols used in these studies. It is suggested that multisite experimentation using standard protocols, models, and recovery criteria would be helpful in moving neural transplantation from the laboratory to the clinic.

The ethics of fetal tissue grafting should be considered along with the science

In addition to the scientific and medical issues surrounding the use of fetal tissue transplants, the ethical implications should be considered. Two major ethical issues are relevant. The first of these is whether this experimental procedure can be justified on the basis of potential benefit to the patient. The second is whether the use of tissue obtained from intentionally aborted fetuses can be justified in the context of historical and existing guidelines for the protection of human subjects. The separation of ethical decisions from medical practice and scientific research is necessary to prevent the exploitation of innocent human life.

Gene therapy for neurodegenerative disorders and malignant brain tumors

Gene therapy approaches have great promise in the treatment of neurodegenerative disorders and malignant brain tumors. Neuwelt et al. review available viral-mediated gene therapy methods and their blood-brain-barrier (BBB) disruption delivery technique, briefly mentioning nonviral mediated gene therapy methods. This commentary discussed the BBB disruption delivery technique, viral and nonviral mediated gene therapy approaches to Parkinson's disease, and the potential use of antisense oligo to suppress malignant brain tumors.

Behavioral effects of neural grafts: Action still in search of a mechanism

This commentary reviews data supporting circuitry reconstruction, replacement neurotransmitters, and trophic action as mechanisms whereby transplants promote recovery of function. Issue is taken with the thesis of Sinden et al. that adequate data exist to indicate that reconstruction of hippocampal circuitry damaged by hypoxia with CA1 transplants is a confirmed mechanism whereby these transplants produce recovery. Sinden et al.'s and Stein & Glasier's proposal that there is definitive evidence showing that all transplants produce trophic effects is also questioned.

Nucleic acids: Vaccines of the future

The recent successful immunization of experimental animals using nucleic acids has provided a revolutionary new approach in vaccinology. In this article, Gary Waine and Don McManus examine the potential of nucleic acid vaccines for their effectiveness not only against infectious and parasitic organisms exhibiting an intracellular phase during their life cycle, but also against parasitic helminths, whose life cycle stages are either predominantly or completely extracellular.

Neural transplantation, cognitive aging and speech

Research on neural transplantation has great potential societal importance in part because of the expanding proportion of the population that is elderly. Transplantation studies can benefit from the guidance of research on cognitive aging, especially in connection with the assessment of behavioral outcomes. Speech for example, might be explored using avian models.

Pathway rewiring with neural transplantation

A lesion to the brain is not necessary for a successful neural transplantation. Embryonic Purkinje cells placed on the surface of an uninjured adult cerebellum can develop and migrate into the host molecular layer. Both the Purkinje cells that migrated into the host cerebellum and those that remained in the graft were innervated by collateral sprouting of adult intact climbing fibers.

Multiple potential mechanisms of graft action is not a new idea

It is well established that neural grafts can exert functional effects on the host animal by a multiplicity of different mechanisms – by diffuse release of trophic molecules, neurohormones, and deficient neurotransmitters, as well as by growth and reformation of neural circuits. Our challenge is to understand how these different mechanisms complement each other.

Grafts and the art of mind's reconstruction

The use of neural transplantation to alleviate cognitive deficits is still in its infancy. We have an inadequate understanding of the deficits induced by different types of brain damage and their homologies in animal models against which to assess graft-induced recovery, and of the ways in which graft growth and function are influenced by factors within the host brain and the environment in which the host is operating. Further, use of fetal tissue may only be a transitory phase in the search for appropriate donor sources. Nevertheless, findings from our laboratory and elsewhere have made aprima faciecase for successful cognitive reconstruction by graft methods.

Studying restoration of brain function with fetal tissue grafts: Optimal models

We concur that basic research on the use of CNS grafts is needed. Two important model systems for functional studies of grafts are ignored by Stein & Glasier. In the first, reproductive function is restored in hypogonadal mice by transplantation of GnRH-synthesizing neurons. In the second, circadian rhythmicity is restored by transplantation of the suprachiasmatic nucleus.

Gene replacement therapy in the CNS: A view from the retina

Gene replacement therapy holds great promise in the treatment of many genetic CNS disorders. This commentary discusses the feasibility of gene replacement therapy in the unique context of the retina, with regard to: (1) the genetics of retinal neoplasia and degeneration, (2) available gene transfer technology, and (3) potential gene delivery vehicles.

The limitations of central nervous systemdirected gene transfer

Complementation and correction of a genetic defect with CNS manifestations lags behind gene therapy for inherited disorders affecting other organ systems because of shortcomings in delivery vehicles and access to the CNS. The effects of improvements in viral and nonviral vectors, coupled with the development of delivery strategies designed to transfer genetic material thoughout the CNS are being investigated by a number of laboratories in efforts to overcome these problems.

CNS transplant utility may surive even their hasty clinical application

Neural cell transplants have been introduced in clinical practice during the last decade with mixed results, encouraged by success with simple animal models. This commentary is a reminder that although the ideas and techniques of transplantation appear simple, the variables involved in host-transplant integration still require further study. The field may benefit from a concerted, multidisciplinary approach.

Are fetal brain tissue grafts necessary for the treatment of brain damage?

Despite some clinical promise, using fetal transplants for degenerative and traumatic brain injury remains controversial and a number of issues need further attention. This response reexamines a number of questions. Issues addressed include: temporal factors relating to neural grafting, the role of behavioral experience in graft outcome, and the relationship of rebuilding of neural circuitry to functional recovery. Also discussed are organization and type of transplanted tissue, the “trophic hypothesis” of transplant viability, and whether transplants are really needed to obtain functional recovery after brain damage.

Transplantation, plasticity, and the aging host

Neural transplantation as a recovery strategy for neuro-degenerative diseases in humans has used mainly grafting following acute denervation strategies in young adult hosts. Our work in aged mice and rats demonstrates an age-related increase in susceptibility to oxidative damage from neurotoxins, a remarkably poor recovery of C57BL/6 mice from MPTP insult with transplantation and growth factors, even at 12 months of age, and diminished plasticity of host neurons. We believe that extrapolation of data from young adult animal models to aged humans without thorough investigation of transplantation and host response inagedrecipients is scientifically and ethically inappropriate.

Targeted gene transfer into hepatoma cells with lipopolyamine-condensed DNA particles presenting galactose ligands: a stage toward artificial viruses

Optimal in vitro gene delivery with cationic lipids requires an excess of cationic charges with respect to DNA phosphates. In these conditions, in vivo delivery will be hampered by interference from cationic lipid-binding macromolecules either circulating or in the extracellular matrix. To overcome this problem, we are developing a modular transfection system based on lipid-coated DNA particles reminiscent of enveloped viruses. The particle core consists of the lipopolyamine-condensed nucleic acid in an electrically neutral ratio to which other synthetic lipids with key viral properties are hydrophobically adsorbed. As a first result, we have found that a good transfection level can be achieved simply with the neutral core particle, provided a zwitterionic lipid (dioleoyl phosphatidylethanolamine) is added to completely coat the DNA. Addition of lipids bearing a fusogenic or a nuclear localization peptide head group to the particles does not significantly improve an already efficient system, in contrast to polylysine-based gene transfer methods that rely on lysosomotropic or fusogenic agents to be effective. This emphasizes the distinctive properties of the lipopolyamines, including cell membrane destabilization, endosome buffering capacity, and possibly nuclear tropism. Most importantly, addition of lipids with a triantennary galactosyl residue drives the neutral nucleolipidic particles to the asialoglycoprotein receptor of human hepatoma HepG2 cells: Transfection increases approximately 1000-fold with 25% galactolipid. This receptor-mediated process is saturable and slightly less efficient than receptor-independent transfection obtained in vitro with a large excess of cationic lipid alone. Yet, electrically silent particles may provide an attractive solution for gene transfer in vivo where their external saccharide coat should allow them to diffuse within the organism and reach their target cells.

Acute hepatitis in rats expressing human hepatitis B virus transgenes

The molecular mechanisms responsible for hepatocyte death and the events leading to viral clearance in hepatitis B virus (HBV) infections are not well understood. Elucidation of the mechanisms involved have been complicated by the difficulty of infecting human hepatocytes with HBV in vitro and the lack of an appropriate animal model. We report an animal model of human HBV infection by in vivo transfection. We have directly introduced a replication-competent, cloned HBV construct into rat liver by using a membrane fusion-promoting cationic lipid. HBV mRNA and 3.2-kb HBV DNA were expressed in the liver by this in vivo transfection method. In the majority of rats, HBV virions and hepatitis B e antigen were found in the blood 3-7 days after transfection, after which antibody to the e antigen appeared. Two to three weeks after the transfection, glutamic-pyruvic transaminase levels were elevated in serum, hepatocyte death and lymphocyte infiltration were observed in the vicinity of the portal vein of liver, and HBV virions were no longer detected in the serum. Thus, transfection of HBV into rats resulted in histological and serological changes comparable to HBV-induced acute hepatitis in humans. In contrast, no hepatocellular injury was observed in T-lymphocyte-deficient nude rats transfected with the same HBV construct, and viremia was substantially prolonged, providing direct evidence that T lymphocytes play an essential role in liver cell injury and in the clearance of HBV. This rat hepatitis model will be useful for studying pathogenesis of HBV infection.

The impact of gene therapy on dentistry

To the casual observer, gene therapy--an emerging science--appears likely to have little impact on dentistry. However, even in these early research stages, it is clear that gene therapy will have a broad effect on dentistry. This article is designed to provide the practitioner with a general understanding of gene therapy, as well as several examples of how it is being used today in efforts to manage dental and oral problems better.

Gene therapy for lung cancer

BACKGROUND

The techniques of molecular genetics are being applied in many areas of oncology and have been spectacularly successful in elucidating the pathogenesis of cancer. Attempts are now being made to harness this knowledge for therapeutic use. Lung cancers are common solid tumours of complex aetiology and represent a major challenge for gene therapy.

CURRENT INVESTIGATIONS

The approaches presently under investigation include the correction of acquired genetic abnormalities, such as mutation of p53 and activation of the ras oncogene, immunotherapy, enhancement of host resistance to cytotoxic insult, and genetic activation of prodrugs by tissue-specific promoters. A variety of vector systems arc available, including liposomes, replication-defective retroviruses and adenoviruses. Local, regional and systemic routes of administration are being studied, and it seems likely that a combination of these approaches will be needed if such treatments are to become generally available.

Treatment of cystic fibrosis based on understanding CFTR

In the five years since the gene associated with cystic fibrosis was isolated, rapid progress has been made in understanding the structure and function of CFTR, the gene product. Based on the knowledge that CFTR is a cAMP-regulated chloride channel in the apical surface of epithelia in many tissues, new approaches to treating CF disease have emerged. These include development of agents to open alternative chloride channels, to relocate mutant CFTR, which commonly is mislocalized because of a trafficking defect, and to deliver CFTR using protein or gene therapy. Although the underlying basis of each of these approaches is now well understood, major practical problems face each of them. Nevertheless, it is difficult not to be optimistic that new therapies will emerge.

In vivo disposition characteristics of plasmid DNA complexed with cationic liposomes

To control disposition and hence gene expression, we investigated the disposition characteristics of plasmid DNA complexed with the cationic liposomes Lipofectin and LipofectACE after intravenous injection in mice via the tail vein. The optimum ratios of DNA and liposome complexes were selected through in vitro cytotoxicity and transfection studies. The highest transfection was found at the DNA:liposome ratio of 1:5 w/w. Hence, this ratio was used for in vivo disposition studies, and the distribution patterns were compared with that of naked pCAT. Following intravenous injection of [32P] pCAT, radioactivity was rapidly eliminated from plasma and approximately 60% of the dose was taken up by the liver within 1.5 min. In the case of LipofectACE samples, radioactivity elimination from plasma was equally rapid, but its accumulation was observed in both the liver (35%) and the lung (45%). For Lipofectin samples, radioactivity was initially accumulated in both the liver (55%) and the lung (25%), but lung accumulation was not sustained beyond 5 min after administration. Both liposomal samples showed in vivo gene expression in the lung, heart, kidney and spleen, but not in the liver. Thus, the present study demonstrated that disposition and gene expression of pCAT can be controlled by complex formation with liposomes.

Sustained expression of functional nerve growth factor in primary septo-hippocampal cell cultures by liposome-mediated gene transfer

We examined liposome-mediated gene transfection of nerve growth factor (NGF) in primary central nervous system cultures. RT-PCR analyses detected increased expression of NGF mRNA one day after liposome-mediated NGF gene transfection. ELISA studies detected large increases in NGF protein in cells and in culture medium after NGF gene transfection. Cells continued to secrete NGF into the medium for at least 2 weeks. NGF bioassays confirmed that the NGF secreted after gene transfection was biologically active.

Optimizing liposome-mediated gene transfer in primary rat septo-hippocampal cell cultures

Although liposomes have been widely employed to transfect DNA into a variety of cell types, no previous studies have systematically examined conditions producing optimal liposomal-mediated transfection of DNA into central nervous system (CNS) cells. Thus, we used the beta-galactosidase (beta-gal) reporter gene to examine factors influencing the efficiency of liposome-mediated gene transfection in CNS cell cultures. Our results indicate that without increasing the amounts of DNA, increased liposome concentrations within certain limits enhanced transfection efficiency. However, higher liposome levels could produce cell lysis. Without increasing liposome concentrations, increased amounts of DNA did not improve transfection efficiency. Employing the optimal concentration (1 microgram DNA/3 microliters liposomes/well), beta-gal gene expression was sustained for at least two weeks after transfection in primary septo-hippocampal cultures.

Non-viral gene therapy

Non-viral gene therapies are currently under development that employ drug-delivery methods for targeting genes to selected cells in the body, where they express therapeutic gene products. Various methods have been described for non-viral gene therapy, ranging from the direct intramuscular injection of purified DNA to the systemic administration of formulations comprising DNA and lipids, proteins, peptides, or polymers. Products for non-viral gene therapies are designed both for direct administration to patients by conventional routes and for expression of a therapeutic product over a finite period of time in a manner similar to conventional medicines. Initial preclinical and clinical studies indicate that non-viral gene delivery methods exhibit safety profiles similar to conventional pharmaceutical or biological products. Clinical trials have been proposed, or are currently under way, to assess the applicability of non-viral gene therapy for a variety of disorders, including cystic fibrosis, cancer, and peripheral vascular disease. Non-viral techniques may soon allow gene therapy to be applied in clinical practice alongside conventional medicines for the treatment of common diseases.

Gene expression following direct injection of DNA into liver

The liver is an attractive target tissue for gene therapy. Current approaches for hepatic gene delivery include retroviral and adenoviral vectors, liposome/DNA, and peptide/DNA complexes. This study describes a technique for direct injection of DNA into liver that led to significant gene expression. Gene expression was characterized in both rats and cats following injection of plasmid DNA encoding several different proteins. Luciferase activity was measured after injection of plasmid DNA encoding the luciferase gene (pCMVL), beta-galactosidase (beta-Gal) activity was evaluated in situ using plasmid DNA encoding Lac Z (pCMV beta), and serum concentration of secreted human alpha-1-antitrypsin was measured following injection of plasmid DNA encoding this protein (pRC/CMV-sHAT). Several variables, including injection technique, DNA dose, and DNA diluent, were investigated. Direct injection of pCMVL resulted in maximal luciferase expression at 24-48 hr. beta-Gal staining demonstrated that the majority of transfected hepatocytes were located near the injection site. Significant concentrations of human alpha-1-antitrypsin were detected in the serum of animals injected with pRC/CMV-sHAT. These findings demonstrate the general principle that direct injection of plasmid DNA into liver can lead to significant gene expression.

Improved biological activity of antisense oligonucleotides conjugated to a fusogenic peptide

Recently several groups reported a dramatic improvement of reporter gene transfection efficiency using a fusogenic peptide, derived from the Influenza hemagglutinin envelop protein. This peptide changes conformation at acidic pH and destabilizes the endosomal membranes thus resulting in an increased cytoplasmic gene delivery. We describe the use of a similar fusogenic peptide in order to improve the antiviral potency of antisense oligodeoxynucleotides (anti TAT) and oligophosphorothioates (S-dC28) on de novo HIV infected CEM-SS lymphocytes in serum-free medium. We observed as 5 to 10 fold improvement of the anti HIV activities of the phosphodiester antisense oligonucleotides after chemical coupling to the peptide in a one to one ratio by a disulfide or thioether bond. No toxicities were observed at the effective doses (0.1-1 microM). No sequence specificity was obtained and the fusogenic peptide possessed some antiviral activities on its own (IC50: 6 microM). A S-dC28-peptide disulfide linked conjugate and a streptavidin-peptide-biotinylated S-dC28 adduct showed similar activities as the free S-dC28 oligonucleotide (IC50: 0.1-1 nM). As expected, all the compounds were less potent in the presence of serum but the relative contribution of peptide coupling was maintained.

Gene transfer into hematopoietic progenitor and stem cells: progress and problems

Gene transfer to hematopoietic cells for the purpose of "gene therapy" is a new and rapidly developing field with clinical trials in progress. A fundamental goal of research in this field is the incorporation of exogenous genes into the chromosomes of the most primitive hematopoietic progenitor cells--stem cells. Recombinantly engineered retroviral vectors are the best characterized and are currently the only vector type in clinical trials directed at the hematopoietic system. High efficiency gene transfer and expression in murine stem cells and their progeny is now routine, but in larger animal models such as dogs or primates and preliminary clinical trials, gene transfer has been less successful. Problems such as retroviral efficiency, gene expression, insertional mutagenesis and helper virus contamination are being addressed. A promising new vector, the adeno-associated virus (AAV), has shown promise and may allow production of high titer, stable, recombinant virions without helper contamination and with potentially better safety parameters. However, the technology for AAV gene transfer is currently underdeveloped, and issues related to the reproducible production of vectors must be addressed. Other non-viral vector systems are being explored, but little data are available on applications to hematopoietic cells. Better preclinical models are needed to study gene targeting and expression in human cells. An overview of recombinant retroviral and adeno-associated viral vector production, preclinical data and preliminary clinical data will be given, and problems needing to be addressed at all stages of development before broad clinical utility can be achieved will be discussed.

Protein expression in vivo by injection of polynucleotides

Over the past few years, intramuscular injection of non-replicating DNA expression vectors has been demonstrated to be generally applicable as an effective method of producing functional proteins in vivo. This technique has been useful in the study of growth factors, regulation of protein expression, transplantation rejection, gene therapy, immune regulation and the production of monoclonal antibodies. The most successful application of DNA injection has, however, been the generation of immune responses in animal models, with the ultimate goal of developing vaccines for humans. Therefore, this approach has the potential to be a new vaccine technology, in addition to its utility in other areas of research.

Primary fibroblasts from human adults as target cells for ex vivo transfection and gene therapy

Diploid fibroblast (dFb) cultures were established from a total of 106 skin and serosa biopsies of human adults. Using an optimized enzymatic dissociation procedure, 10(11) dFb/cm2 skin were obtained from patients younger than 60 years after an average time of 89 +/- 8 days, with a mean population doubling time of 3.87 +/- 1.4 days. Enzymatic dissociation of skin biopsies yielded cultures of significantly higher growth capacity of dFb than those prepared by mechanical dissociation followed by spontaneous outgrowth of cells. The plating efficiency that may be crucial for clonal selection of transfected cells was negligible when dFb were plated without feeder cells at low density, while it was enhanced to 9-24% by the addition of a feeder layer of irradiated human embryonal fibroblasts. DFb secreted various cytokines with spontaneous release of interleukin-6 (IL-6) in high quantities of up to 20 ng/10(6) cells/24 hr. In addition, one-third of the culture secreted substantial amounts of granulocyte-macrophage colony-stimulating factor (GM-CSF), while low amounts of tumor necrosis factor-alpha (TNF-alpha) were detectable in some cases after irradiation of the cells. Comparison of various transfection methods by a transient luciferase expression assay demonstrated that receptor-mediated gene transfer was approximately 10-fold more efficient than cationic lipofection of dFb, while electroporation resulted in substantially less expression of the reporter gene. We conclude that primary dFb can be obtained reproducibly from human adults and represent a suitable target cell population for receptor-mediated gene transfer and cationic lipofection.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction in vitro of primary cytotoxic T-lymphocyte responses with DNA encoding herpes simplex virus proteins

Vaccines which successfully protect against virus infections usually need to induce a broadly reactive immune response which includes the induction of cytotoxic T lymphocytes (CTL). In this study, we have used a convenient in vitro approach to investigate if plasmid DNAs encoding proteins of herpes simplex virus (HSV) are capable of inducing primary CD8+ CTL. Dendritic cells or macrophages were transfected with either plasmid DNA encoding glycoprotein B or DNA encoding the immediate-early protein ICP27. These antigen-presenting cells (APC) were then used to stimulate enriched populations of naive T cells in microcultures for 5 days in vitro. Antigen-specific CD8+ CTL which reacted both with specific protein-expressing targets and with syngeneic targets infected with HSV could be demonstrated. Dendritic cells, as APC, generated the maximal responses, but such cells needed to be transfected with DNA in the presence of a cationic lipid. However, macrophages could act as APC when they were exposed to purified DNA. HSV-primed splenocytes were also shown to generate specific CTL responses when they were stimulated with purified DNA encoding ICP27. The novel approach described in this paper promises to be extremely useful, since defining immunogenicity profiles and identifying epitopes on viral proteins should be easier and more convenient when working with DNA and investigating variables in vitro. This is particularly the case with complex viruses such as HSV, most of whose encoded proteins have yet to be isolated in sufficient quantity or purity to perform in vivo immunological studies.