Human gene marker/therapy clinical protocols

Characterization of complexes formed by polypropylene imine dendrimers and anti-HIV oligonucleotides

Current anti-HIV therapies are capable of controlling viral infection but do not represent a definitive cure. They rely on the administration of antiretroviral nucleoside analogues, either alone or in combination with vectors. Dendrimers are branched, synthetic polymers with layered architectures, promising non-viral vectors in gene therapy. The aim of the paper was to study the interactions between three anti-HIV antisense oligonucleotides (ODNs): SREV, ANTI TAR, GEM91 and different generation polypropylene imine dendrimers (PPI) by monitoring changes in the fluorescence polarization of fluorescein attached to the ends of the ODNs when increasing concentrations of dendrimers were added. Laser Doppler electrophoresis, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to characterize, respectively, zeta potential, particle size and morphology of dendriplexes formed in different molar ratios. Antisense oligonucleotides interacted with polypropylene imine dendrimers in different molar ratios depending on generation. Zeta potential of dendriplexes varied from (-25 to -21) mV to -5 mV (for PPIG3 and PPIG4 complexes) and to zero (for PPIG2 complexes). The structures presented a polydisperse size from about 50 nm to even 700-800 nm by TEM and about 250 nm by DLS. It means that besides single dendriplexes, aggregates were also present.

Pharmacokinetics of DS-96, an alkylpolyamine lipopolysaccharide sequestrant, in rodents

The pharmacokinetics of DS-96, an N-alkylhomospermine analog designed to sequester bacterial lipopolysaccharides, has been determined in rodent species. The elimination half-life in mice and rats are about 400 and 500 min, respectively, with other PK parameters being quite similar in the two rodent species. Interestingly, the mouse intravenous plasma concentration time curves exhibit an apparent absorption phase. While the rat intravenous data did not exhibit a pronounced apparent absorption phase immediately following injection, plasma levels did increase between 10 and 30 min following an expected drop from time 0 to 5 min. The data are consistent with first-pass uptake, possibly by the lung, with back diffusion as a function of time. The observed C(max) values of 1.36 microg/mL in the mouse intraperitoneal model suggest that a plasma concentration of 0.5-1 microg/mL corresponds to complete protection for a 200 ng/animal dose of intraperitoneally administered LPS in the D-galactosamine-primed model of endotoxin-induced lethality.

Protection from endotoxic shock by EVK-203, a novel alkylpolyamine sequestrant of lipopolysaccharide

Lipopolysaccharides (LPS) play a key role in the pathogenesis of septic shock, a major cause of mortality in the critically ill patient. The only therapeutic option aimed at limiting downstream systemic inflammatory processes by targeting lipopolysaccharide is Toraymyxin, an extracorporeal hemoperfusion device using solid phase-immobilized polymyxin B (PMB). While PMB is known to effectively sequester LPS, its severe systemic toxicity proscribes its parenteral use, and hemoperfusion may not be feasible in patients in shock. In our continuing efforts to develop small-molecule mimics which display the LPS-sequestering properties, but not the toxicity of PMB, a series of mono- and bis-substituted dialkylpolyamines were synthesized and evaluated. We show that EVK-203, an alkylpolyamine compound, specifically binds to and neutralizes the activity of LPS, and affords complete protection in a murine model of endotoxic shock. EVK-203 is without any apparent toxicity when administered to mice at multiples of therapeutic doses for several days. The specific endotoxin-sequestering property along with a very favorable therapeutic index renders this compound an ideal candidate for preclinical development.

Gene therapy approaches to HIV infection

The HIV pandemic represents a new challenge to biomedical research. What began as a handful of recognized cases among homosexual men in the US has become a global pandemic of such proportions that it clearly ranks as one of the most destructive viral scourges in history. In the past few years new treatments and drugs have been developed and tested, but the development of a new generation of therapies remains a major priority, because of the lack of chemotherapeutic drugs or vaccines that show long-term efficacy in vivo. Recently, gene therapeutic strategies for the treatment of patients with HIV infection have received increased attention because they are able to offer the possibility of simultaneously targeting multiple sites in the HIV genome, thereby minimizing the production of resistant virus. Recombinant genes for gene therapy can be classified as expressing interfering proteins (intracellular antibodies, dominant negative proteins) or interfering RNAs (antisense RNAs, ribozymes, RNA decoys). The latter group offers the advantage of avoiding the stimulation of host immune response which might progressively decrease the efficacy of proteins. The stumbling block to achieving lasting antiviral effects is still represented by the lack of efficient gene transfer techniques capable of generating persistent transgene expression and a high number of transduced cells relative to untransduced cells. Novel delivery vectors, such as lentiviruses, might overcome some of these shortcomings. The use of recombinant genes to generate immunity is a very promising concept that is rapidly expanding. Since the immune system can significantly amplify the response to tiny amounts of antigen, DNA vaccines can indeed be delivered by exploiting traditional gene therapy approaches without the need of high transduction efficiency.

Towards a rational development of anti-endotoxin agents: novel approaches to sequestration of bacterial endotoxins with small molecules

Endotoxins, or lipopolysaccharides (LPS), present on the surface of Gram-negative bacteria, play a key role in the pathogenesis of septic shock, a common clinical problem and a leading cause of mortality in critically ill patients, for which no specific therapeutic modalities are available at the present time. The toxic moiety of LPS is a glycolipid called 'lipid A', which is composed of a bisphosphorylated diglucosamine backbone bearing up to seven acyl chains in ester and amide linkages. Lipid A is structurally highly conserved in Gram-negative bacteria, and is therefore an attractive target for developing anti-endotoxin molecules designed to sequester, and thereby neutralize, the deleterious effects of endotoxins. The anionic and amphipathic nature of lipid A enables the interaction of a wide variety of cationic amphiphiles with the toxin. This review describes the systematic evaluation of several structural classes of cationic amphiphiles, both peptides and non-peptidic small molecules, in the broader context of recent efforts aimed at developing novel anti-endotoxin strategies. The derivation of a pharmacophore for LPS recognition has led to the identification of novel, nontoxic, structurally simple small molecules, the lipopolyamines. The lipopolyamines bind and neutralize LPS in in vitro experiments as well as in animal models of endotoxicity, and thus present novel and exciting leads for rational, structure-based development of LPS-sequestering agents of potential clinical value.

An episomally maintained MDR1 gene for gene therapy

Potential applications of the MDR1 multidrug transporter in gene therapy include protecting sensitive bone marrow cells against cytotoxic drugs during cancer chemotherapy and serving as a dominant selectable marker when coexpressed with a corrective passenger gene. To address safety concerns associated with integrating viral systems, such as retroviruses, we tested the feasibility of maintaining a nonvirally delivered MDR1 gene (pEpiHaMA) episomally. An MDR1 vector containing the Epstein-Barr virus (EBV) origin of replication (OriP) and its nuclear retention protein (EBNA-1) was transfected into human (KB-3-1) cells. MDR1 was expressed at a higher level in cells carrying the episomal vector, pEpiHaMA, compared with the vector lacking sequences needed for episomal maintenance (pHaMA). Furthermore, more drug-resistant KB-3-1 colonies were obtained on selection after transfection with pEpiHaMA. These observations correlated with longer maintenance of episomes in cells transfected with pEpiHaMA. In addition, episomes could still be recovered for more than 1 month from tumor explants in nude mice that were injected with pEpiHaMA-liposome complexes after drug selection, suggesting that these constructs can be maintained extrachromosomally in vivo.

Prolonged allograft survival through conditional and specific ablation of alloreactive T cells expressing a suicide gene

BACKGROUND

Control of antidonor activated T cells involved in allograft rejection while preserving immunocompetence is a challenging goal in transplantation. Engineered T cells expressing a viral thymidine kinase (TK) suicide gene metabolize the nontoxic prodrug ganciclovir (GCV) into a metabolite toxic only to dividing cells. We evaluated this suicide gene strategy for inducing transplantation tolerance in mice.

METHODS

Transgenic mice expressing TK in mature T cells were analyzed for (i) specific T-cell depletion under GCV treatment upon various stimulations; (ii) outcome of allogeneic nonvascularized skin or heart allografts under a short 14-day GCV treatment initiated at the time of transplantation; and (iii) the capacities of T cells from such allotransplanted mice to proliferate in mixed lymphocyte reactions and to induce graft-versus-host disease in irradiated recipients with the genetic background of the donor allograft.

RESULTS

Upon in vitro or in vivo GCV treatment, only activated dividing TK T cells but not B cells were efficiently depleted. Acute rejection of allogeneic grafts was prevented and a significant prolongation of graft survival was obtained, although associated with signs of chronic rejection. Prolonged skin graft survival correlated with decreased in vitro and in vivo T-cell reactivities against donor alloantigens, whereas overall immunocompetence was preserved.

CONCLUSIONS

Efficient and specific depletion of alloreactive TK T cells can be achieved by administrating GCV. These results open new perspectives for the control of allogeneic graft rejection using suicide gene therapy.

Scientific progress in understanding oral and pharyngeal cancers

Oral and pharyngeal cancers result from a complex interaction between genetic susceptibility and behavioral factors. Improved understanding of the underlying genetic events has led to insights about how oral and pharyngeal cancers develop and suggests promising new treatments. Tobacco and alcohol consumption are associated with most oral and pharyngeal cancers. Dental professionals' efforts to modify their patients' tobacco and alcohol use and to detect oral lesions at an early stage, together with scientific advances, will help reduce the impact of these cancers.

Prevention of Graft-Versus-Host Disease in Mice Using a Suicide Gene Expressed in T Lymphocytes

Alloreactive T cells present in a bone marrow transplant are responsible for graft-versus-host disease (GVHD), but their depletion is associated with impaired engraftment, immunosuppression, and loss of the graft-versus-leukemia effect. We developed a therapeutic strategy against GVHD based on the selective destruction of these alloreactive T cells, while preserving a competent T-cell pool of donor origin. We generated transgenic mice expressing in their T lymphocytes the Herpes simplex type 1 thymidine kinase (TK) suicide gene that allows the destruction of dividing T cells by a ganciclovir treatment. T cells expressing the TK transgene were used to generate GVHD in irradiated bone marrow grafted mice. We show that a short 7-day ganciclovir treatment, initiated at the time of bone marrow transplantation, efficiently prevented GVHD in mice receiving TK-expressing T cells. These mice were healthy and had a normal survival. They maintained a T-cell pool of donor origin that responded normally to in vitro stimulation with mitogens or third party alloantigens, but were tolerant to recipient alloantigens. Our experimental system provides the proof of concept for a therapeutic strategy of GVHD prevention using genetically engineered T cells.