Safe, efficient, and reproducible gene therapy of the brain in the dog models of Sanfilippo and Hurler syndromes.

Recent trials in patients with neurodegenerative diseases documented the safety of gene therapy based on adeno-associated virus (AAV) vectors deposited into the brain. Inborn errors of the metabolism are the most frequent causes of neurodegeneration in pre-adulthood. In Sanfilippo syndrome, a lysosomal storage disease in which heparan sulfate oligosaccharides accumulate, the onset of clinical manifestation is before 5 years. Studies in the mouse model showed that gene therapy providing the missing enzyme α-N-acetyl-glucosaminidase to brain cells prevents neurodegeneration and improves behavior. We now document safety and efficacy in affected dogs. Animals received eight deposits of a serotype 5 AAV vector, including vector prepared in insect Sf9 cells. As shown previously in dogs with the closely related Hurler syndrome, immunosuppression was necessary to prevent neuroinflammation and elimination of transduced cells. In immunosuppressed dogs, vector was efficiently delivered throughout the brain, induced α-N-acetyl-glucosaminidase production, cleared stored compounds and storage lesions. The suitability of the procedure for clinical application was further assessed in Hurler dogs, providing information on reproducibility, tolerance, appropriate vector type and dosage, and optimal age for treatment in a total number of 25 treated dogs. Results strongly support projects of human trials aimed at assessing this treatment in Sanfilippo syndrome.

Replacing the enzyme alpha-L-iduronidase at birth ameliorates symptoms in the brain and periphery of dogs with mucopolysaccharidosis type I.

Mucopolysaccharidosis type I (MPS I) is a lysosomal storage disease caused by loss of activity of α-l-iduronidase and attendant accumulation of the glycosaminoglycans dermatan sulfate and heparan sulfate. Current treatments are suboptimal and do not address residual disease including corneal clouding, skeletal deformities, valvular heart disease, and cognitive impairment. We treated neonatal dogs with MPS I with intravenous recombinant α-l-iduronidase replacement therapy at the conventional 0.58 mg/kg or a higher 1.57 mg/kg weekly dose for 56 to 81 weeks. In contrast to previous results in animals and patients treated at a later age, the dogs failed to mount an antibody response to enzyme therapy, consistent with the induction of immune tolerance in neonates. The higher dose of enzyme led to complete normalization of lysosomal storage in the liver, spleen, lung, kidney, synovium, and myocardium, as well as in the hard-to-treat mitral valve. Cardiac biochemistry and function were restored, and there were improvements in skeletal disease as shown by clinical and radiographic assessments. Glycosaminoglycan levels in the brain were normalized after intravenous enzyme therapy, in the presence or absence of intrathecal administration of recombinant α-l-iduronidase. Histopathological evidence of glycosaminoglycan storage in the brain was ameliorated with the higher-dose intravenous therapy and was further improved by combining intravenous and intrathecal therapy. These findings argue that neonatal testing and early treatment of patients with MPS I may more effectively treat this disease.

Idiopathic eosinophilic meningoencephalomyelitis in a Rottweiler dog.

A 6-month-old, female, intact Rottweiler dog was presented to the Iowa State University Veterinary Teaching Hospital for a progressive history of abnormal behavior and generalized ataxia. At necropsy, there was eosinophilic infiltration of the brain and spinal cord, most severe in the medulla oblongata, cerebellum, and cervical spinal cord. Infiltrates of eosinophils were also present in the liver and small intestines. The dog was diagnosed with idiopathic eosinophilic meningoencephalomyelitis based on cerebrospinal fluid analysis, histopathology, and special stains to exclude etiologic agents.

Severe polymyositis and neuritis in a cat.

CASE DESCRIPTION: A 4-year-old domestic shorthair cat was evaluated for a 1-week history of shifting limb lameness that progressed to tetraparesis. CLINICAL FINDINGS: Physical examination revealed generalized muscle atrophy and signs of discomfort when the muscles of the appendicular skeleton were palpated. Neurologic examination revealed diminished myotatic and withdrawal reflexes in all 4 limbs. Results of a CBC indicated mild neutrophilia, and serum biochemical analysis revealed mild hyperalbuminemia and high creatine kinase activity. The cat was anesthetized, and an electromyogram (EMG), CSF sample, and nerve and muscle biopsy specimens were obtained. The EMG revealed positive sharp waves and fibrillation potentials, CSF analysis revealed albuminocytologic dissociation, and histologic examination of muscle and nerve specimens revealed severe myositis and neuritis. Immune-mediated polymyositis and neuritis were suspected. TREATMENT AND OUTCOME: With physical therapy and long-term corticosteroid drug treatment, the cat recovered complete motor nerve function. CLINICAL RELEVANCE: The severity and rapid progression of clinical signs, combined with the EMG abnormalities and histologic findings, could have led to inappropriate euthanasia for this cat. Veterinarians should be aware that immune-mediated polymyositis and neuritis in cats can have an excellent prognosis with appropriate, long-term treatment.

A vascular hamartoma arising from the cervical spine of a cat.

A 15-month-old cat presented for evaluation of worsening generalized proprioceptive ataxia. Computed tomography of the cervical spine revealed the presence of a compressive extradural bony mass involving the dorsal aspect of C1. Surgical exploration and debulking of the mass was performed. Histological evaluation of the mass revealed fibrovascular tissue consistent with a vascular hamartoma. This mass was deemed to be originating from the soft tissue associated with the C1 vertebra with subsequent bony proliferation. Surgical debulking of the mass resulted in complete resolution of clinical signs with no evidence of recurrence 2 years after surgery.

Imaging features of atlanto-occipital overlapping in dogs.

The imaging features of four dogs with atlanto-occipital overlapping are described. This malformation appeared to play a role in the development of neck pain, ataxia, variable cerebellar involvement, medullary kinking, and possibly syringomyelia. Using cervical radiographs, three of the four dogs were initially diagnosed with an atlanto-axial malformation. Because this disorder could not account for all clinical signs, magnetic resonance and computed tomography images were also acquired. These provided a more complete evaluation of the craniocervical junction, allowing detection of atlanto-occipital overlapping, medullary kinking, occipital dysplasia, abnormalities of the dens, and syringomyelia in these dogs. Head position during imaging affected the degree of atlanto-occipital overlap. These findings emphasize the need to modify the currently accepted imaging recommendations for dogs with head and neck pain and/or cranial cervical myelopathy. We suggest that the entire craniocervical junction be evaluated, even if atlanto-axial subluxation has already been detected. Moreover, we propose that atlanto-occipital overlapping is a perhaps underrecognized disorder that can influence the clinical signs and therapeutic outcome of dogs with anomalies of the craniocervical junction.

Neonatal cerebellar ataxia in Coton de Tulear dogs.

A neonatal ataxia syndrome was observed in Coton de Tulear dogs. Seven affected pups (32%; 7/22) of both genders came from 5 different litters with phenotypically normal parents. Neurologic examination revealed normal mental status, head titubation, intention tremors, and severe gait, stance, and ocular ataxia beginning at 2 weeks of age. One of the pups was able to walk with assistance, but most of the affected pups were unable to stand and used propulsive movements ("swimming") for goal-oriented activities. They frequently would fall to lateral recumbency with subsequent decerebellate posturing and paddling. Ocular motor abnormalities included fine vertical tremors at rest and saccadic dysmetria. The condition was nonprogressive at least until 4 months of age. No specific abnormalities were identified in routine laboratory screening of blood and urine. Cerebrospinal fluid (CSF) analysis was normal in 1 dog, and a mild increase in protein concentration was observed in a second dog. CSF organic and amino acid concentrations were within normal limits. Magnetic resonance imaging and computed tomography of the brain, electromyography, motor nerve conduction studies, and brain stem auditory-evoked potentials were within normal limits. Postmortem examinations were performed on 5 affected dogs between 2 and 4 months of age. Routine light microscopic and immunocytochemical examination of brain, spinal cord, peripheral nerve, and muscle did not disclose any gross or histologic lesions. Compared with the cerebellum from an age-matched normal dog, the cerebellum from an affected dog showed synaptic abnormalities, including loss of presynaptic terminals and organelles associated with parallel fiber varicosities within the molecular layer and increased numbers of lamellar bodies in Purkinje cells. An autosomal recessive trait affecting development of the cerebellum is suspected.

Complementary and alternative medicine for neurologic disorders.

The use of complementary and alternative veterinary medicine in treating neurologic disorders has increased in popularity in response to advances in human alternative and integrative therapies. Neurolocalization of lesions to the brain, spinal cord, and neuromuscular systems is discussed, as well as the diagnostics and therapeutics used to treat such disorders. Emphasis is placed on integrative and alternative treatments for such neurologic diseases as seizures, cerebrovascular accidents, canine cognitive disorder, meningitis, intervertebral disc disease, fibrocartilagenous embolism, degenerative myelopathy, and myopathies. Thorough physical and neurologic examinations, establishment of a correct diagnosis, and integrative therapeutics are aimed at improving the overall quality of life of the veterinary patient.