Intra-arterial virus and nonvirus vector-mediated gene transfer to experimental rat brain tumors

Targeting human glioma cells using HSV-1 amplicon peptide display vector

Targeting cell infection using herpes simplex virus type 1 (HSV-1) vectors is a complicated issue as the process involves multiple interactions of viral envelope glycoproteins and cellular host surface proteins. In this study, we have inserted a human glioma-specific peptide sequence (denoted as MG11) into a peptide display HSV-1 amplicon vector replacing the heparan sulfate-binding domain of glycoprotein C (gC). The modified MG11:gC envelope recombinant vectors were subsequently packaged into virions in the presence of helper virus deleted for gC. Our results showed that the tropism of these HSV-1 recombinant virions was increased for human glioma cells in culture as compared with wild-type virions. The binding of these recombinant virions could also be blocked effectively by pre-incubating the cells with the glioma-specific peptide, indicating that MG11 peptide and the recombinant virions competed for the same or similar receptor-binding sites on the cell surface of human glioma cells. Furthermore, preferential homing of these virions was shown in xenograft glioma mouse model following intravascular delivery. Taken together, these results validated the hypothesis that HSV-1 binding to cells can be redirected to human gliomas through the incorporation of MG11 peptide sequence to the virions.

Nonviral approaches for neuronal delivery of nucleic acids

The delivery of therapeutic nucleic acids to neurons has the potential to treat neurological disease and spinal cord injury. While select viral vectors have shown promise as gene carriers to neurons, their potential as therapeutic agents is limited by their toxicity and immunogenicity, their broad tropism, and the cost of large-scale formulation. Nonviral vectors are an attractive alternative in that they offer improved safety profiles compared to viruses, are less expensive to produce, and can be targeted to specific neuronal subpopulations. However, most nonviral vectors suffer from significantly lower transfection efficiencies than neurotropic viruses, severely limiting their utility in neuron-targeted delivery applications. To realize the potential of nonviral delivery technology in neurons, vectors must be designed to overcome a series of extra- and intracellular barriers. In this article, we describe the challenges preventing successful nonviral delivery of nucleic acids to neurons and review strategies aimed at overcoming these challenges.

Intra-arterial delivery of endostatin gene to brain tumors prolongs survival and alters tumor vessel ultrastructure

Glioblastoma multiforme (GBM) is an incurable malignant brain tumor, usually fatal within 1 year of diagnosis. Using a syngeneic rat 9L gliosarcoma model, we have developed a novel drug delivery method in which naked plasmid DNA is selectively targeted to brain tumors via intra-arterial injection. Using a plasmid encoding the antiangiogenic endostatin, transgene expression can be detected in tumor cells in vivo, and therapeutic efficacy is observed. Administration of this plasmid resulted in an 80% tumor volume reduction 1 week after treatment and enhanced survival time by up to 47%. Treated tumors exhibited a 40% decrease in the number of tumor vessels; ultrastructural analysis of remaining tumor vessels demonstrated a number of changes including markedly narrowed or collapsed lumens. We conclude that intra-arterial injection of plasmids selectively targets therapeutic genes to CNS neoplasms. This method of gene therapy holds promise for the treatment of these highly malignant brain tumors.

Quantitation of HSV mass distribution in a rodent brain tumor model

A number of different viral vectors have been used for gene therapy of tumors, with many more under construction, ultimately designed to improve tumor targeting and transduction efficiency. It has become apparent that insufficient viral delivery can be a key limitation to treatment efficacy. We have studied the in vivo mass distribution of a herpes simplex virus type 1 (HSV) vector, hrR3, by radiolabeling it with 111In-oxine. The virus was administered to intracerebral 9L glioma bearing Fisher (F-344) rats by intracarotid and intratumoral injection. The blood half-life of the virus was 1 min (fast component, 10% contribution) and 180 min (slow component, 90% contribution). Approximately 20% of activity had been excreted by 24 h. With intracarotid injection, the total amount of virus that accumulated in tumor was 0.10+/-0.07% of the injected dose (ID)/g at 1 h and 0.19+/-0.01% ID/g at 24 h. By comparison, co-injection of RMP-7, a synthetic bradykinin analog, with the virus, resulted in slightly increased tumor delivery of 0.17+/-0.10% ID/g (P 0.05) at 1 h. The 1 h organ distribution after intra-arterial injection (%ID/organ) was as follows: liver 273+/-2.86%, lung 2.10+/-0.68% and kidney 1.78+/-1.60% with lesser amounts in other organs. When virus was injected directly into the tumor, 71% of virus remained in tumor at 24 h (590+/-212 %ID/g, consistent with the small tumor mass containing most of the virus) with the following distribution regions: tumor > border zone > normal brain (99:40: 1). These studies are the first quantitative mass distribution studies of HSV vectors in an experimental brain tumor model. Localization and quantitation of viral accumulation in vivo will enable detailed analysis of viral and organ interactions critical for advancing the therapeutic use of vectors.