Evaluation of safety and early efficacy of AAV gene therapy in mouse models of vanishing white matter disease

Leukoencephalopathy with vanishing white matter (VWM) is a progressive incurable white matter disease that most commonly occurs in childhood and presents with ataxia, spasticity, neurological degeneration, seizures, and premature death. A distinctive feature is episodes of rapid neurological deterioration provoked by stressors such as infection, seizures, or trauma. VWM is caused by autosomal recessive mutations in one of five genes that encode the eukaryotic initiation factor 2B complex, which is necessary for protein translation and regulation of the integrated stress response. The majority of mutations are in EIF2B5. Astrocytic dysfunction is central to pathophysiology, thereby constituting a potential therapeutic target. Herein we characterize two VWM murine models and investigate astrocyte-targeted adeno-associated virus serotype 9 (AAV9)-mediated EIF2B5 gene supplementation therapy as a therapeutic option for VWM. Our results demonstrate significant rescue in body weight, motor function, gait normalization, life extension, and finally, evidence that gene supplementation attenuates demyelination. Last, the greatest rescue results from a vector using a modified glial fibrillary acidic protein (GFAP) promoter-AAV9-gfaABC(1)D-EIF2B5-thereby supporting that astrocytic targeting is critical for disease correction. In conclusion, we demonstrate safety and early efficacy through treatment with a translatable astrocyte-targeted gene supplementation therapy for a disease that has no cure.

Vanishing white matter disease expression of truncated EIF2B5 activates induced stress response

Vanishing white matter disease (VWM) is a severe leukodystrophy of the central nervous system caused by mutations in subunits of the eukaryotic initiation factor 2B complex (eIF2B). Current models only partially recapitulate key disease features, and pathophysiology is poorly understood. Through development and validation of zebrafish (Danio rerio) models of VWM, we demonstrate that zebrafish eif2b mutants phenocopy VWM, including impaired somatic growth, early lethality, effects on myelination, loss of oligodendrocyte precursor cells, increased apoptosis in the CNS, and impaired motor swimming behavior. Expression of human EIF2B2 in the zebrafish eif2b2 mutant rescues lethality and CNS apoptosis, demonstrating conservation of function between zebrafish and human. In the mutants, intron 12 retention leads to expression of a truncated eif2b5 transcript. Expression of the truncated eif2b5 in wild-type larva impairs motor behavior and activates the ISR, suggesting that a feed-forward mechanism in VWM is a significant component of disease pathophysiology.

Competing spatial and temporal instabilities in a globally coupled bistable semiconductor system near a codimension-two bifurcation

We study complex spatiotemporal dynamics in a globally coupled bistable reaction-diffusion model on a two-dimensional spatial domain. It is demonstrated that complex behavior appears near a codimension-two bifurcation point due to the competition of spatial and temporal instabilities. We derive sufficient conditions for the appearance of mixed spatiotemporal modes, and clarify the origin of a menagery of complex dynamics, such as periodic and chaotic oscillations of current filaments, low-dimensional spatiotemporal chaos including a Shil'nikov attractor, and periodic back-and-forth motion of current density fronts. Such dynamics is found in a wide range of domain sizes for square and rectangular domains. The type of dynamics is sensitive to small variations in the domain shape. We discuss and explain the differences between spatiotemporal dynamics on one-dimensional and two-dimensional domains.

Wave fronts may move upstream in semiconductor superlattices

In weakly coupled, current biased, doped semiconductor superlattices, domain walls may move upstream against the flow of electrons. For appropriate doping values, a domain wall separating two electric-field domains moves downstream below a first critical current, it remains stationary between this value and a second critical current, and then moves upstream above. These conclusions are reached by using a comparison principle to analyze a discrete drift-diffusion model, and validated by numerical simulations. Possible experimental realizations are suggested.

Karhunen-Loeve local characterization of spatiotemporal chaos in a reaction-diffusion system

By computing the Karhunen-Loeve decomposition (KLD) correlation length xi(KLD) of a reaction-diffusion system in the extensive chaos regime, we show that it is a sensitive measure of spatial dynamical inhomogeneities. It reveals substantial spatial nonuniformity of the dynamics at the boundaries and can also detect slow spatial variations in system parameters. The intensive length xi(KLD) can be easily computed from small local subsystems and is found to have a similar parametric dependence as the two-point correlation length computed over the full system size.

Comparative investigation of drug delivery of collagen implants saturated in antibiotic solutions and a sponge containing gentamicin

Collagen implants of various structures and a gelatine sponge were placed in five different antibiotic solutions until complete saturation occurred. The antibiotics were chosen to represent different drug classes (gentamicin sulphate, cefotaxim, fusidic acid, clindamycin, vancomycin). The collagen implants saturated with antibiotic solution and a lyophilized collagen sponge containing gentamicin sulphate were eluated in 0.066 M phosphate buffer (pH = 7.4) at 37 degrees C. The total eluation period is 7 d with buffer changes every 24 h. The antibiotic delivery by the collagen implants and the lyophilized sponge containing gentamicin sulphate is complete after a maximum of 4 d. If an implant that has a protective effect against wound infections over a period of 24-48 h is required, the materials described here are suitable. However, where treatment in infected areas should ensure antibiotic cover for 5-10 d, neither collagen materials immersed in antibiotic solutions nor collagen sponges containing gentamicin are suitable.

Characterization of mouse CD53: epitope mapping, cellular distribution and induction by T cell receptor engagement during repertoire selection

The pan-leukocyte antigen CD53 is a member of the poorly understood transmembrane 4 superfamily (TM4SF) of cell membrane glycoproteins. CD53 is proposed to play a role in thymopoiesis, since rat CD53 is expressed on immature CD4-8-thymocytes and the functionally mature single-positive subset, but is largely absent from the intermediate CD4+8+ cells. We have characterized CD53 in the mouse through the production of two new monoclonal antibodies, MRC OX-79 and OX-80, which were raised against the RAW 264 cell line and screened on recombinant CD53 fusion proteins. The epitopes recognized by both antibodies are dependent on disulfide bonding and map to the major extracellular region of CD53, requiring the presence of a single threonine residue at position 154. Mouse CD53 has a molecular mass of 35-45 kDa and is expressed on virtually all peripheral leukocytes, but not on cells outside the lymphoid or myeloid lineages. CD53 expression distinguishes subpopulations of thymocytes in the mouse and resembles the expression pattern of rat CD53. Amongst the immature CD4-8-thymocytes, mouse CD53 is clearly detectable on the earliest CD44high25- subset, but down-regulated on the later CD44high25+, CD44low25+ and CD44low25- stages. Also, the subsequent transient TcR-/low CD4-8+ cells and most CD4+8+ thymocytes express little or no CD53. This is consistent with the idea that cells which are committed to enter the selectable CD4+8+ compartment switch off CD53. The effect of T cell receptor (TcR) engagement on the re-expression of CD53 on CD4+8+ thymocytes was studied both ex vivo and in vitro using F5 mice, transgenic for the H-2b/influenza nucleoprotein-peptide-specific TcR, back-crossed onto an H-2q or H-2b background of RAG-2-deficient mice. CD4+8+ thymocytes from non-selecting H-2q F5 mice are CD53 negative, but in vitro stimulation through the TcR dramatically induces CD53 expression. In contrast, a fraction of CD4+8+ thymocytes from positively selecting H-2b F5 transgenic mice express CD53. Therefore TcR engagement by selecting major histocompatibility complex peptide complexes, or surrogate ligands, induces CD53 expression on otherwise CD53-negative, non-selected CD4+8+ thymocytes. Whether CD53 itself participates as a signaling molecule in further stages of thymic selection is still a matter of speculation.

Effects of myocardial revascularization following acute coronary occlusion in pigs

In a comparative study in pigs the extent of myocardial infarction has been estimated following a temporary three hour coronary occlusion and following a permanent coronary ligation. For evaluation of the cellular injury the infarct size has been determined by a histochemical staining procedure and correlated with serum enzyme studies (creatine phosphokinase, alpha-hydroxybutyric dehydrogenase) in the surviving animal. No significant difference could be detected between the two experimental groups and the extent of cellular damage was similar. A strict linear correlation was found between the serum enzyme activity plotted logarithmically and the morphological infarct size. Likewise the incidence of ventricular fibrillation depended on the extent of cellular injury. Myocardial revascularization does not appear to benefit a pig heart subjected to an acute coronary occlusion lasting three hours or more. Revascularization may even be harmful by creating a haemorrhagic infarct, as found in all the animals submitted to a transient coronary occlusion.

[Tolerance of the porcine kidney for temporary ischemia. (Biochemical and morphological studies)]

Pigs were used as experimental animals to study the relationship between the duration of renal ischaemia and the extent of biochemical, serological and pathological changes. In pigs subjected to unilateral nephrectomy, the maximum duration of ischaemia tolerated without adverse effects on vital functions was 3.5 to 4 hours.