Long-Term Behavioral Recovery in Parkinsonian Rats by an HSV Vector Expressing Tyrosine Hydroxylase

Abstract

One therapeutic approach to treating Parkinson's disease is to convert endogenous striatal cells into levo-3,4-dihydroxyphenylalanine (L-dopa)-producing cells. A defective herpes simplex virus type 1 vector expressing human tyrosine hydroxylase was delivered into the partially denervated striatum of 6-hydroxydopamine-lesioned rats, used as a model of Parkinson's disease. Efficient behavioral and biochemical recovery was maintained for 1 year after gene transfer. Biochemical recovery included increases in both striatal tyrosine hydroxylase enzyme activity and in extracellular dopamine concentrations. Persistence of human tyrosine hydroxylase was revealed by expression of RNA and immunoreactivity.Parkinson's disease (PD), a neurodegenerative disorder, is characterized by the progressive loss of the dopaminergic neurons in the substantia nigra pars compacta that project to the corpus striatum (1). The principal therapy for PD is the oral administration of L-dopa (2), which is converted to dopamine (DA) by endogenous striatal aromatic amino acid decarboxylase (AADC) (3). Although it is initially effective, L-dopa therapy loses efficacy over a period of several years (1). Transplantation of cells that produce L-dopa or DA into the striatum can correct animal models of PD (4) but has not been a viable therapy in most human trials (5). Peripheral cell types that are genetically modified to express tyrosine hydroxylase (TH) and produce L-dopa have supported only short-term improvement (less than 2 months) in animal models of PD (6,7). Genetically modified muscle cells support longer improvements (6 months) (8), but the viability of a muscle cell graft in the human striatum is not yet clear. An alternative therapeutic strategy is to convert a fraction of the striatal cells into L-dopa-producing cells by expression of TH in striatal cells (9) from a defective herpes simplex virus type 1 (HSV-1) vector (10). Potential advantages of this approach include production of L-dopa at the required site of action, so that diffusion over substantial distances is not necessary, and alleviation of potential problems caused by graft rejection or tumor formation. To test this strategy, a human TH complementary DNA (cDNA) (form II) (11, 12) was inserted into an HSV-1 vector (pHSVth). Infection of cultured striatal cells with pHSVth resulted in expression of human TH RNA, TH immunoreactivity, and the release of L-dopa into the culture medium (13). The amounts of L-dopa released per infected cell suggested that pHSVth might be evaluated in the 6-hydroxydopamine (6-OHDA)-lesioned rat, a model of PD.pHSVth virus or pHSVlac virus or vehicle alone [phosphate-buffered saline (PBS)], was delivered by stereotactic injection into the partially denervated striatum of unilaterally 6- OHDA-lesioned rats (14). The apomorphine-induced rotation rate was measured as an index of behavioral recovery. The average decrease in the rotation rate caused by pHSVth was 64 ± 6% at 2 weeks after gene transfer. This value remained relatively constant over a...

Functional expression of ATM gene carried by HSV amplicon vector in vitro and in vivo

“…18,19,[43][44][45] The full-length ATM cDNA is beyond the packaging capacity of most widely used viral vectors; so we employed an HSV-1-based amplicon vector that, in theory, can package 140 kb of DNA payload. 33,34 The ATM gene, therefore, was cloned into pTO HSV amplicon vector and the insert was confirmed to be intact by Southern blot analysis (data not shown).…”

“…[18][19][20][21][22][23] Several ongoing human clinical trials are based on HSV vectors. [24][25][26] One of the two broad categories of HSV-based vectors, the amplicon, is a plasmid-type vector, which carries an HSV-1 lytic replication origin (ori s ) and HSV-1 packaging signal sequence.…”

Constitutive and Inducible Innate Responses in Cells Infected by HSV-1- Derived Amplicon Vectors

“…This implies that all virus self-protective functions are absent, with the only exception of the functions carried by the structural proteins that are introduced in the cells during entry of vector particles, which have nevertheless a limited half-life and will soon disappear. This is probably at the basis of the low or transient expression often observed with helper-free amplicon vectors, both in cultured cells and in experimental animals [21, 22]. Actually, many observations suggest that expression from helper-free amplicons is transient in many experimental settings and that the length and intensity of transgene expression is cell-type specific.…”

In vivo expression of therapeutic human genes for dopamine production in the caudates of MPTP-treated monkeys using an AAV vector

“…However, it is more difficult to deliver gene products to nondividing neurons which might be the appropriate targets for increasing neurotransmitter production. We and others have previously used herpes simplex virus type I (HSV-1) 6 and adenoviral vectors, 7 to introduce the human TH gene into cells of the denervated striatum after 6-hydroxydopamine-induced dopamine depletion in the rat. Because of the inherent toxicity of current generation HSV, adenoviral, or HIV-derived vectors, [6][7][8] we chose to use an AAV vector in the present study.…”

“…We and others have previously used herpes simplex virus type I (HSV-1) 6 and adenoviral vectors, 7 to introduce the human TH gene into cells of the denervated striatum after 6-hydroxydopamine-induced dopamine depletion in the rat. Because of the inherent toxicity of current generation HSV, adenoviral, or HIV-derived vectors, [6][7][8] we chose to use an AAV vector in the present study. This vector can be generated free of any helper virus, without viral genes, and with just the minimal elements for packaging and DNA replication (the 145 base inverted terminal repeats).…”