Intranasally inoculated neurotropic influenza viruses in mice infect not only the respiratory tract but also the central nervous system (CNS), mainly the brain stem. Previous studies suggested that the route of invasion of virus into the CNS was via the peripheral nervous system, especially the vagus nerve. To evaluate the transvagal transmission of the virus, we intranasally inoculated unilaterally vagectomized mice with a virulent influenza virus (strain 24a5b) and examined the distribution of the viral protein and genome by immunohistochemistry and in situ hybridization over time. An asymmetric distribution of viral antigens was observed between vagal (nodose) ganglia: viral antigen was detected in the vagal ganglion of the vagectomized side 2 days later than in the vagal ganglion of the intact side. The virus was apparently transported from the respiratory mucosa to the CNS directly and decussately via the vagus nerve and centrifugally to the vagal ganglion of the vagectomized side. The results of this study, thus, demonstrate that neurotropic influenza virus travels to the CNS mainly via the vagus nerve.

A/Hong Kong/483/97 (H5N1) influenza virus (HK483) isolated from the third patient during the outbreak of chicken and human influenza in Hong Kong in 1997 was shown to be neurovirulent in mice. HK483 was inoculated intranasally to mice, and the invasion routes of the virus in the central nervous system (CNS) were investigated by immunohistochemical and in situ hybridization. The pathological changes consisted of bronchopneumonia, ganglionitis, and nonpurulent encephalomyelitis of the brain stem and the anterior part of the thoracic cord. Viral antigens and viral nucleic acids (RNA and mRNA) were demonstrated in the pterygopalatine, trigeminal and superior ganglions prior to or simultaneously with their detection in the CNS. The antigens and nucleic acids were also observed in the olfactory bulb from an early stage of the infection. In the spinal cord, virus-infected cells were first demonstrated in the grey matter of the thoracic cord. The virus, which primarily replicated in the lungs, was considered to invade the thoracic cord via cardiopulmonary splanchnic nerves and sympathetic nerves. These findings indicate that the virus reached the CNS through afferent fibers of the olfactory, vagal, trigeminal, and sympathetic nerves following replication in the respiratory mucosa.

A six-month-old shiba dog with a one-month history of progressive motor dysfunction showed clinical signs of a cerebellar disorder, including ataxia, dysmetria and intention tremor of the head. Histopathological and ultrastructural studies revealed distended neurons packed with membranous cytoplasmic bodies throughout the central nervous system. The activities of lysosomal acid beta-galactosidase in its leucocytes and liver were less than 2 per cent of the control levels, and the compound accumulated in the brain was identified as GM1 ganglioside. A sibling which died immediately after birth was shown to have a beta-galactosidase deficiency in the brain and visceral organs. A family study revealed that the sire and dam of the probands were heterozygotes with approximately half of the normal level of beta-galactosidase activity, suggesting an autosomal recessive pattern of inheritance.

No abstract

ABSTRACT. The present study was conducted to determine the clinical and clinico-pathologic characteristics of Shiba dogs with GM1 gangliosidosis, which is due to an autosomal recessively inherited deficiency of lysosomal acid β-galactosidase activity. Clinical and clinicopathological features were investigated in 10 homozygous Shiba dogs with GM1 gangliosidosis. The age at onset was 5 to 6 months and the dogs manifested progressive neurologic signs including loss of balance, intermittent lameness, ataxia, dysmetria and intention tremor of the head. The dogs were unable to stand by 10 months of age due to a progression of ataxia and spasticity in all limbs. Corneal clouding, a visual defect, generalized muscle rigospasticity, emotional disorder and a tendency to be lethargic were observed at 9 to 12 months. The dogs became lethargic from 13 months of age. The survival period seemed to be 14 to 15 months. As a clinico-pathologic feature, lymphocytes with abnormally large vacuoles were observed in peripheral blood (30 to 50% of total lymphocytes) through the lifetime of the dogs. The clinical and clinico-pathologic characteristics of this animal model are useful for not only the development and testing of potential methods of therapy, but also the diagnosis of affected homozygous Shiba dogs in veterinary clinics. KEY WORDS: acid β-galactosidase deficiency, β-galactosidosis, GM1 gangliosidosis, lysosomal storage disease, Shiba dog.