PEX6 Mutations in Peroxisomal Biogenesis Disorders: An Usher Syndrome Mimic

PURPOSE

Peroxisomal biogenesis disorders (PBDs) represent a spectrum of conditions that result in vision loss, sensorineural hearing loss, neurologic dysfunction, and other abnormalities resulting from aberrant peroxisomal function caused by mutations in PEX genes. With no treatments currently available, we sought to investigate the disease mechanism in a patient with a PBD caused by defects in PEX6 and to probe whether overexpression of PEX6 could restore peroxisome function and potentially offer therapeutic benefit.

DESIGN

Laboratory-based study.

PARTICIPANTS

A 12-year-old boy sought treatment with hearing loss and retinopathy. After negative results in an Usher syndrome panel, targeted genetic testing revealed compound heterozygous mutations in PEX6. These included a 14-nucleotide deletion (c.802_815del: p.(Asp268Cysfs∗8)) and a milder missense variant (c.35T→C:(p.Phe12Ser)).

METHODS

Patient-derived skin fibroblasts were cultured, and a PEX6 knockout cell line was developed using clustered regularly interspaced short palindromic repeats and Cas9 technology in HEK293T cells to emulate a more severe disease phenotype. Immunoblot analysis of whole cell lysates was performed to assess peroxisome number. Immunofluorescence studies used antibodies against components of the peroxisomal protein import pathway to interrogate the effects of mutations in PEX6 on protein trafficking.

MAIN OUTCOME MEASURES

Primary outcome measures were peroxisome abundance and matrix protein import.

RESULTS

Peroxisome number was not significantly different between control fibroblasts and patient fibroblasts; however, fewer peroxisomes were observed in PEX6 knockout cells compared with wild-type cells (P = 0.04). Analysis by immunofluorescent microscopy showed significantly impaired peroxisomal targeting signal 1- and peroxisomal targeting signal 2-mediated matrix protein import in both patient fibroblasts and PEX6 knockout cells. Overexpressing PEX6 resulted in improved matrix protein import in PEX6 knockout cells.

CONCLUSIONS

Mutations in PEX6 were responsible for combined hearing loss and retinopathy in our patient. The primary peroxisomal defect in our patient's skin fibroblasts was impaired peroxisomal protein import as opposed to reduction in the number of peroxisomes. Genetic strategies that introduce wild-type PEX6 into cells deficient in PEX6 protein show promise in restoring peroxisome function. Future studies of patient-specific induced pluripotent stem cell-derived retinal pigment epithelium cells may clarify the role of PEX6 in the retina and the potential for gene therapy in these patients.

Ocular Gene Therapy with Adeno-associated Virus Vectors: Current Outlook for Patients and Researchers

In this "Perspective", we discuss ocular gene therapy - the patient's perspective, the various strategies of gene replacement and gene editing, the place of adeno-associated virus vectors, routes of delivery to the eye and the remaining question - "why does immunity continue to limit efficacy?" Through the coordinated efforts of patients, researchers, granting agencies and industry, and after many years of pre-clinical studies, biochemical, cellular, and animal models, we are seeing clinical trials emerge for many previously untreatable heritable ocular disorders. The pathway to therapies has been led by the successful treatment of the RPE65 form of Leber congenital amaurosis with LUXTURNA TM . In some cases, immune reactions to the vectors continue to occur, limiting efficacy. The underlying mechanisms of inflammation require further study, and new vectors need to be designed that limit the triggers of immunity. Researchers studying ocular gene therapies and clinicians enrolling patients in clinical trials must recognize the current limitations of these therapies to properly manage expectations and avoid disappointment, but we believe that gene therapies are well on their way to successful, widespread utilization to treat heritable ocular disorders.

Treatment of vulvar lichen sclerosus with topical corticosteroids in children: a study of 72 children

Treatment of vulvar lichen sclerosus (VLS) in children by topical corticosteroids gives control of symptoms and some resolution of physical signs, but large studies are limited. We report the largest study of 72 prepubertal girls with VLS, 62 of whom were prospectively treated with daily application of an ultrapotent topical corticosteroid (UPTC), clobetasol propionate 0.05% ointment, for 3 months, with a follow-up period of 4-8 years [the remaining 10 patients responded to mild to moderate potency topical corticosteroids (MPTCs)]. The results were compared with a retrospective study of 31 prepubertal girls with VLS treated with MPTCs. MPTCs led to symptom clearance in 32.2% of patients, whereas UPTC led to symptom clearance in 72.6% of patients. Improvement in clinical signs following UPTC occurred in 90.3% of children at 3 months, with total resolution of clinical signs occurring in 29.2% at the 4-year follow-up or at puberty. No serious adverse effects occurred with UPTC treatment. In children with VLS, UPTCs relieve symptoms, resolve signs and possibly prevent scarring. UPTCs should therefore be the treatment of choice for VLS in children.

Antigenic and genetic divergence of rabies viruses from bat species indigenous to Canada

Antigenic characterisation of over 350 chiropteran rabies viruses of the Americas, especially from species reported rabid in Canada, distinguished 13 viral types. In close accord with this classification, nucleotide sequencing of representative isolates, at both the N and G loci, identified four principal phylogenetic groups (I-IV), sub-groups of which circulated in particular bat species. Amongst the North American bat viruses, there was a notable division between group I specimens associated with colonial, non-migratory bats (Myotis sp. and Eptesicus fuscus) and those of group II harbored by solitary, migratory species (Lasiurus sp. and Lasionycteris noctivagans). Certain species of Myotis were clearly identified as rabies reservoirs, an observation often obscured previously by their frequent infection by viral variants of other chiroptera. An additional group (III) apparently circulates in E. fuscus, whilst viruses harbored by both insectivorous and haematophagus bats of Latin America clustered to a separate clade (group IV). Comparison of the predicted N and G proteins of these viruses with those of strains of terrestrial mammals indicated a similarity in structural organisation regardless of host species lifestyle. Finally, these sequences permitted examination of the evolutionary relationship of American bat rabies viruses within the Lyssavirus genus.

Phylogeographic patterns exhibited by Ontario rabies virus variants

A previous study on N gene variation of rabies viruses circulating in Ontario red foxes identified four viral variants. This study confirms the geographical localization of these variants and extends the analysis to the less conserved G gene of these viruses. A greater number of regionally localized variants was revealed and their phylogenetic relationships have been examined. Ongoing surveillance on recent disease outbreaks revealed that variants do not always persist in specific areas. The distribution of these variants did however appear to be influenced by topographical features of the study area likely to affect host animal movements and contacts. The majority of G gene base changes were synonymous and limited glycoprotein sequence variation predominantly to the C-terminal transmembrane and endo-domains. These data are most readily explained by random appearance of genetic viral variants followed by their spread throughout sub-populations of the fox host according to the easiest routes of transmission.

The long incubation period in rabies: delayed progression of infection in muscle at the site of exposure

The striped skunk (Mephitis mephitis) is a host of rabies in large areas of Canada and the United States. In each of two experiments, equal numbers of skunks in two groups were inoculated intramuscularly with low doses of a field strain of rabies virus (street rabies virus). In each experiment, skunks in one group surviving to 2 months were killed at this time and selected tissues were used for examination by the polymerase chain reaction (PCR) method or by immunohistochemistry for rabies antigen. Results of detailed examinations using PCR technology (experiment 1) indicated that muscle at the inoculation site contained viral RNA at 2 months postinoculation, when other relevant tissues on the route of viral migration and early entrance into the central nervous system were negative. The cellular location of virus/antigen, as determined immunohistochemically in experiment 2, was striated muscle fibers and fibrocytes. Our results indicate a major role of muscle (tissue) infection at the inoculation site in the long incubation period of rabies in skunks. These and related findings will be useful in rabies control and, if applicable to other species, will be relevant in postexposure treatment.

Duration of immunity in foxes vaccinated orally with ERA vaccine in a bait

Red foxes (Vulpes vulpes) vaccinated orally with the ERA strain of rabies vaccine in a bait were challenged after 83 mo. Ten of 11 foxes that had seroconverted following vaccination resisted challenge with a virulent rabies virus which produced clinical signs of rabies in 6 of 6 unvaccinated foxes. Five of 11 vaccinated animals retained titers of rabies virus neutralizing antibody throughout the period. Although 6 of 11 had no detectable antibody at the time of challenge, 5 of these 6 resisted challenge and had an anamnestic response, as indicated by elevated titers of antibody when measured at day 77 postchallenge. These results show that foxes can be immunized successfully with a single oral dose of ERA vaccine, probably with protection against a lethal rabies challenge, for at least 7 y.

Cluster of rabies cases of probable bat origin among red foxes in Prince Edward Island, Canada

Between 15 November and 13 December 1993, three cases of rabies of probable bat origin were confirmed in red foxes (Vulpes vulpes) from the same area of Prince Edward Island, Canada, previously thought to be free of rabies in terrestrial mammals. Such clusters have rarely been described in North America.

Early events in rabies virus infection of the central nervous system in skunks (Mephitis mephitis)

Twenty-four striped skunks were inoculated intramuscularly (long digital extensor muscle of right pelvic limb) with street rabies virus. Groups of two clinically normal skunks were killed at various times after inoculation; skunks that developed rabies were killed in early stages of the clinical signs. Four clinically normal skunks (numbered 1-4) had slight infection in lumbar spinal ganglia, spinal cord and brain. These four skunks were used for detailed immunohistochemical (rabies antigen) studies that included examination of sections from every segment of the spinal cord, most of the spinal ganglia from the 2nd cervical to the 2nd coccygeal (sections at 25-microns intervals of lumbar, sacral and coccygeal ganglia) and brain (sections at 50-micron intervals). In skunks 1-4, there was increasing distribution of antigen-containing neurons that was not correlated with the time elapsed since inoculation. In three skunks (nos. 1, 2 and 3), antigen-containing neurons were predominantly in caudal regions of the spinal cord, caudal right lumbar and sacral spinal ganglia and certain nuclei/regions of the brain (medial reticular formation, right interpositus and lateral vestibular nuclei, left red nucleus, left motor cortex, and left reticular nucleus of the thalamus). Skunk 4 had more extensive infection than skunks 1-3, but the previous pattern was still evident. The results are consistent with viral entrance into the lumbar spinal cord, initial replication mainly at the L2 and L3 levels, local spread in the cord by propriospinal neurons and early transit to the brain via long ascending and descending fiber tracts (bypassing the grey matter of the rostral spinal cord). These mechanisms could provide for early and rapid dissemination in the brain before a significant immune response develops and could induce behavioral changes before the animal is incapacitated by extensive spinal cord infection. Based on the distribution of antigen-containing neurons, the tracts considered most likely to serve as viral transitways from spinal cord to brain include: rubrospinal, corticospinal, spinothalamic, spino-olivary, vestibulospinal and/or spinovestibular, reticulospinal and/or spinoreticular, cerebellospinal and/or spinocerebellar, and dorsal column pathways.

A molecular epidemiological study of rabies virus in central Ontario and western Quebec

Rabies persists in Ontario wildlife in two predominant species: the red fox (Vulpes vulpes) and the striped skunk (Mephitis mephitis). A protocol applying reverse transcription/polymerase chain reaction (RT/PCR) and restriction endonuclease analysis (REA) to the rabies virus nucleoprotein gene was previously reported by Nadin-Davis et al. (Journal of General Virology 74, 829-837, 1993) to be useful for discrimination of rabies virus variants in Ontario. Four main types, which showed no host species specificity but which did exhibit different geographical distributions, were identified. Between 1989 and 1992 an area north and west of the city of North Bay experienced unusual and substantial rabies activity. In this report we describe the use of these molecular techniques to investigate the epidemiology of this recent rabies outbreak in central Ontario. It is shown that two of the four previously identified variants had invaded this region from the south and east, but in addition viruses very closely related to arctic isolates of rabies virus were found. The nucleoprotein and glycoprotein genes of this arctic type were sequenced and compared to those of its more southerly neighbours.

Identification of regional variants of the rabies virus within the Canadian province of Ontario

Although rabies outbreaks in most parts of the world tend to be host species-specific the rabies currently enzootic in the Canadian province of Ontario is hosted by two wildlife species, the red fox and the striped skunk. Previous studies employing monoclonal antibody panels failed to identify any host-specific differences in Ontario rabies virus street isolates, but certain observations suggested the existence of more than one viral strain in terrestrial mammals of this region. The extent of variation of the rabies virus circulating within this region has been re-examined using molecular biology techniques. The N gene of several independent isolates was amplified using PCR and the resulting products were compared by restriction enzyme analysis and, in some cases, by DNA sequencing. This analysis confirmed that there was indeed no host-specific variation in the portion of the viral genome under study but there were, however, very clear and consistent differences in the virus from distinct geographical regions.

Oral rabies vaccination of skunks and foxes with a recombinant human adenovirus vaccine

A new recombinant rabies vaccine (human adenovirus 5 containing the rabies glycoprotein gene) was given to striped skunks (Mephitis mephitis) and red foxes (Vulpes vulpes). Groups of skunks received the vaccine in baits, by direct instillation into the mouth, or intramuscularly. Foxes were given vaccine by direct instillation into the oral cavity (DIOC). Selected groups of vaccinated skunks and foxes were challenged with street rabies virus. There were high rates of seroconversion (generally with high antibody titers) in both foxes and skunks, with survival of all challenged vaccinated animals (all challenge controls developed rabies). In skunks, vaccine given DIOC was effective over a broad range of doses (10(8.7), 10(7.6) and 10(6.4) median tissue culture infective doses). There was no evidence of pathogenic effects. The results indicate that this adenovirus recombinant has considerable potential as a wildlife oral rabies vaccine.

Vaccinia recombinant virus expressing the rabies virus glycoprotein: safety and efficacy trials in Canadian wildlife

Twenty-six meadow voles (Microtus pennsylvanicus), ten woodchucks (Marmota monax), thirteen grey squirrels (Sciurus carolinensis), thirteen ring-billed gulls (Larus delawarensis), six red-tailed hawks (Buteo jamaicensis) and eight great horned owls (Bubo virginianus) received vaccinia virus recombinant expressing the rabies virus glycoprotein (V-RG) by direct instillation into the oral cavity. Each of ten coyotes (Canis latrans) received the virus in two vaccine-laden baits. Several voles and most of the gulls died from diseases unrelated to vaccination during the observation period, but all other animals remained healthy and survived. These deaths from causes other than vaccination and the absence of any lesions suggestive of vaccinia infection indicate that it is unlikely that any animal suffered or died as a result of V-RG administration. In addition several animals showed an unexpected high level of rabies neutralizing antibodies.

Ineffectiveness and comparative pathogenicity of attenuated rabies virus vaccines for the striped skunk (Mephitis mephitis)

Three attenuated rabies virus vaccines (SAD-B19, ERA/BHK-21, AZA 2) were compared for efficacy and safety in the striped skunk (Mephitis mephitis) by the oral and intranasal routes. The SAD-B19 and ERA/BHK-21 vaccines were given orally; all three vaccines were given intranasally. Oral administration of SAD-B19 and ERA/BHK-21 vaccines induced neither seroconversion nor significant protection against rabies challenge. One skunk which consumed a SAD-B19 vaccine-laden bait succumbed to vaccine-induced rabies. Intranasal instillation of the three vaccines resulted in the deaths of two of six (AZA 2), three of six (ERA/BHK-21) and six of six (SAD-B19) skunks.

Mutants of rabies viruses in skunks: immune response and pathogenicity

In studies to develop an oral rabies vaccine for wildlife, the immune response to and pathogenicity of two types of mutants of rabies viruses were examined. Forty-five small plaque mutants were selected from cultures of ERA rabies virus treated with 8-azaguanine or 5-fluorouracil and tested for pathogenicity in mice. Two of these mutants AZA 1 and AZA 2 (low pathogenicity in mice) were given to skunks by oral (bait), intestinal (endoscope) and intramuscular routes. Additionally, challenge virus standard (CVS) rabies virus and mutants of this and ERA rabies virus (CVS 3766 and 3713, and ERA 3629) that were resistant to neutralization by specific antiglycoprotein monoclonal antibodies (and apathogenic in mice) were tested by various routes in skunks. Skunks given AZA 1 and AZA 2 were challenged at three months postinoculation with street rabies virus. After oral administration, there were very low rates of seroconversion with AZA 1 and AZA 2 and on challenge only 2/7 given AZA 1 and 1/8 given AZA 2 survived. None of the skunks given the other mutants orally seroconverted. AZA 2 produced a high rate of seroconversion (8/8) by the intestinal route and all challenged skunks in this group survived (7/7). All skunks vaccinated intramuscularly with AZA 1 (4/4) or AZA 2 (4/4) developed high levels of rabies neutralizing antibodies and survived challenge. The mutant CVS 3766, while apathogenic when given intracerebrally to adult mice, was consistently pathogenic by this route (and intranasally) in skunks. These results demonstrate that skunks are highly resistant to oral immunization by live rabies virus vaccines and that pathogenicity (by intracerebral route) of the mutant CVS 3766 is markedly different in mice and skunks.

Persistent infections of a field strain of rabies virus in murine neuroblastoma (NA-C1300) cell cultures

Rabies virus from the brain of a striped skunk (Mephitis mephitis) from Ontario was inoculated into murine neuroblastoma (NA-C1300) cell cultures. These cultures were incubated and the cells were subcultured every three to four days. The presence of viral antigen in the cell cultures was monitored by direct immunofluorescent staining and in the culture fluids by titration in either baby hamster kidney (BHK/C13) or NA cells or in experimental mice. The virus-infected NA cultures evolved from an initial high viral concentration in supernatant fluid through a period of decreasing titers of infectious virus in the supernatant fluids to a final phase where no infectious virus has been found following cell culture and animal inoculation methods attempted although the persistently infected cells remained 95-100% viral nucleocapsid antigen-positive. Possible mechanisms involved in the perpetuation of this infection are discussed. This is the first report of a persistent infection of cell cultures by a field strain of rabies virus.

Skunk rabies

In North America, the number of cases of rabies diagnosed in skunks generally exceeds that in either raccoons or foxes. Enzootic skunk rabies occurs mainly in four geographic regions: (1) southern Ontario and Quebec and upper New York State; (2) the north central United States and the Canadian provinces of Manitoba, Saskatchewan, and Alberta; (3) California; and (4) south central United States (Texas and several adjacent states). Rabies in these areas (in skunks and, to a large extent, in other terrestrial mammals) is caused mainly by three street virus variants, as determined by monoclonal antibody testing (one variant for areas 2 and 3 and separate variants for each of areas 1 and 4). Experimental studies suggest that the species specificity (e.g., raccoon vs. skunk) of enzootic rabies is due, at least partly, to differences in the pathogenicity of variants of rabies virus.

Immunization of foxes against rabies with a vaccinia recombinant virus expressing the rabies glycoprotein

Foxes were vaccinated orally (by bait), gastrically (by stomach tube) and by scarification with a vaccinia recombinant virus expressing the rabies glycoprotein. Neutralizing antibodies against rabies virus were detected at two weeks postvaccination in 8/8 foxes in the bait-fed group, in 3/6 foxes inoculated by stomach tube and in 2/2 of the scarified foxes. After challenge at three months postvaccination with street rabies virus, all foxes that had developed antibodies were protected. The high rate of seroconversion, high levels of antibodies, and resistance to challenge suggest that this recombinant virus might be a suitable vaccine for oral immunization of foxes against rabies.

Growth characteristics in cell culture and pathogenicity in mice of two terrestrial rabies strains indigenous to Canada

Two strains of street rabies virus from striped skunks (Mephitis mephitis) were used to infect either a murine neuroblastoma (NA 1300) or a baby hamster kidney (BHK-21/C13) cell culture and the cell infection rates were noted during 4 days postinfection. These cultures were then passaged for four consecutive passages, and the viruses obtained in the supernatant fluids of passage 4 were then treated as original isolates and used to infect both neuroblastoma and baby hamster kidney cells. The mortality period in Swiss white mice caused by the various virus suspensions was noted. The virus strain from the brain of skunks from Saskatchewan infected neuroblastoma and baby hamster kidney cells equally well, produced similar virus titres in supernatant fluids after four subcultures in both cell types, and appeared to produce similar mortality periods in mice from either the original brain tissue or from cell culture supernatant fluids. On the other hand, the virus from the brains of skunks from Ontario readily infected neuroblastoma but poorly infected baby hamster kidney cell cultures. Passage of this strain through four subcultures in both cell types produced virus titres in the supernatant fluids of equal magnitude. However, reisolation of the virus from the supernatant fluid of passage 4 in neuroblastoma cell cultures showed a similar pattern to that from the original brain, while the virus from baby hamster kidney cell passage supernatant fluid was considerably altered. Although the mortality period in mice was similar with virus from the brain and neuroblastoma cell cultures, this period was shortened when mice were inoculated with baby hamster kidney culture supernatant virus.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental rabies in skunks and foxes. Pathogenesis of the spongiform lesions

The pathogenesis of rabies spongiform lesions in striped skunks (Mephitis mephitis) and red foxes (Vulpes vulpes) was studied by light and electron microscopy and peroxidase-antiperoxidase immunocytochemistry. Studies in skunks included use of several street virus variants (different antigenic profiles as tested by monoclonal antibodies) different routes of inoculation (intranasal, intracerebral and intramuscular), immunosuppression of infected skunks, different preparations of virus (brain and salivary gland suspensions and infective tissue culture fluids), and sequential development of the lesions. Foxes (Vulpes vulpes) were infected intramuscularly with a street virus isolate. Except for the group of immunosuppressed skunks, all animals that developed clinical signs of rabies had encephalitis characterized by varying degrees of mononuclear perivascular cuffing, focal gliosis, and Negri bodies. Spongiform change occurred in the neuropil of the grey matter (especially thalamus and cerebral cortex) in rabid animals from all groups, but not in controls or exposed animals that did not develop rabies. Rabies antigen (detected by peroxidase-antiperoxidase immunocytochemistry) occurred only in small amounts in many thalami; some vacuolated areas were devoid of antigen. Ultrastructurally, there was a gradation in lesions from small to large membrane-bound vacuoles in cellular processes (mainly dendrites, less frequently axons) and to large tissue spaces containing granular and/or membranous material. These studies indicate that rabies spongiform change occurs in skunks given street virus of several different antigenic profiles and challenge virus standard rabies virus and that the distribution of the lesions has remarkable similarities to those of the traditional spongiform encephalopathies. The occurrence of the lesion is not affected by the immune response, the route of inoculation of virus, the preparation (suspension of salivary gland or brain, or tissue culture fluid), or the incubation period. The paucity of antigen in many thalami suggests that incorporation of viral components into vacuolar membranes is not necessary for development of the spongiform change. The development of the lesions includes formation of small membrane-bound vacuoles in cellular processes, rapid enlargement (less than 3 days) with compression of adjacent neural tissue, and rupture resulting in the large tissue spaces readily visible by light microscopy.

Experimental rabies in skunks: immune response and salivary gland infection

Groups of striped skunks (Mephitis mephitis) were inoculated intramuscularly with graded doses of street rabies virus. At various intervals after inoculation, saliva and sera were tested for rabies virus and neutralizing antibodies, respectively. Skunks that developed rabies were killed in terminal stages of the disease and the following examinations were made: titers of virus and antibody in submandibular salivary glands and brain, extent of immunofluorescence in submandibular salivary glands, and histologic examination of various tissues. Skunks that received inocula containing 4 x 10(4) to 4 x 10(5) mouse intracerebral lethal dose50 (MICLD50) had detectable serum neutralizing antibodies by 7-12 days postinoculation; however, most of the skunks that received lower doses (40 to 4 x 10(3) MICLD50) did not have detectable serum neutralizing antibodies until clinical signs began. In the salivary glands, slight and extensive immunofluorescence corresponded to high and low titers of tissue neutralizing antibody. Also low viral titers were associated with high tissue neutralizing antibody titers. There was a close correlation between viral titers in right and left submandibular salivary glands. The results suggest that the immune response can impede the process of infection of the salivary glands resulting in lack of antigen or low amounts of antigen in this tissue. This could occur through interference with centrifugal neural transport of virus and/or neutralization of virus during transfer from neural elements to epithelial cells. Lack of infectious virus or low viral titers in salivary glands containing antigen and high levels of tissue neutralizing antibodies can be caused partly by postmortem virus neutralization (during viral titration).

Major antigenic groups of rabies virus in Canada determined by anti-nucleocapsid monoclonal antibodies

A total of 123 rabies virus isolates from various geographical areas in Canada were characterized by a panel of 43 anti-nucleocapsid monoclonal antibodies. Four major antigenic groups are found in terrestrial mammals: "Canadian Arctic" from Ontario, Quebec and the Northwest Territories; "south-eastern Georgian Bay" from Ontario; "south mid-central skunk" from Alberta, Saskatchewan and Manitoba; and "Brook's, Alberta skunk" from a restricted area in Alberta. Bat isolates can be divided into 4 major antigenic groups: "B-1" in Eptesicus fuscus from Ontario; "B-2" in a variety of bat species from British Columbia eastward into Ontario; "B-3" in Myotis spp. from Ontario and New Brunswick; and "B-4" in E. fuscus from Alberta and Saskatchewan. A single case of bat to horse transmission of rabies virus is recorded. These street isolates are compared with isolates of fixed virus. Epidemiological aspects are discussed.

Antigenic variants of rabies virus in isolates from eastern, central and northern Canada

Street rabies virus isolated from 51 specimens from Ontario, Quebec, Manitoba and the Northwest Territories have been typed by a panel of 36 antinucleocapsid monoclonal antibodies. Three main groups were found. The first group comprised those terrestrial mammals originating in Ontario, Quebec and the Northwest Territories. The second group was found in terrestrial mammals from Manitoba. The third heterogenous group was made up of bats from Ontario.

Rabies virus in the salivary glands and nasal mucosa of naturally infected skunks

Several salivary glands and the nasal mucosa of rabid skunks (Mephitis mephitis) contained rabies virus. Generally titers were high in the submandibular, moderate in the parotid and low to moderate in the zygomatic, molar and sublingual salivary glands. The nasal mucosa (glands and epithelium) contained virus at low to moderate titers that occasionally were equal to titers in brain.

Experimental rabies in skunks: effects of immunosuppression induced by cyclophosphamide

Striped skunks (Mephitis mephitis) were inoculated with street rabies virus and immunosuppressed with several doses of cyclophosphamide. Control skunks were inoculated with street virus only. The skunks were killed in terminal stages of the disease and several tissues were collected for examination by immunofluorescence, light microscopy and viral titration. Sera collected at euthanasia from most of the principals did not contain detectable rabies neutralizing antibodies, whereas high titers occurred terminally in controls. Immunofluorescence was much more entensive in submandibular salivary glands of cyclophosphamide-treated than control skunks. Similarly, virus was isolated from this tissue more consistently and at higher titer from principals than from controls. Immunofluorescence was extensive in brains of all skunks (both groups), but virus was isolated consistently only from brains of cyclophosphamide-treated skunks. Most of the cyclophosphamide-treated skunks had very few inflammatory cells in brain and cerebrospinal ganglia. Neuronal degeneration occurred in dorsal root ganglia of both principals and controls. The results suggest that the immune response has no effect on the development of rabies-induced aggressive behavior, that the immune response may inhibit salivary gland infection and that it is not essential for the development of neuronal degeneration in dorsal root ganglia.

Experimental rabies in skunks: mechanisms of infection of the salivary glands

Striped skunks (Mephitis mephitis) were inoculated into the right submandibular salivary gland with street rabies virus. They were killed at various times after inoculation and several tissues were examined by immunofluorescence and light microscopy. Right and left superior cervical, nodose and trigeminal ganglia, medulla oblongata and at least three regions of right and left submandibular salivary glands were examined by the fluorescent antibody technique. Intracerebral titrations of salivary gland suspensions were made in weanling white Swiss mice. Immunofluorescent material (inoculum) was detected in septa and connective tissue surrounding secretory units of the right submandibular gland immediately after inoculation, but otherwise antigen was not detected in either right or left submandibular glands without coincident antigen in the medulla oblongata. This occurred first on day 12 in areas of the gland remote from the inoculation site. Titers of virus were low at this time. Serum neutralizing antibodies occurred by day 7 in a few skunks. The time of development and distribution of antigen strongly suggest that, even after direct inoculation, neural networks are necessary for development of widespread infection of the salivary gland. The early occurrence of serum neutralizing antibodies in some of the skunks suggests that the immune response was activated by virus in the inoculum since immunofluorescence was not detected in any tissue at this time.

Paired associates: a workshop model for effecting change

A series of workshops for staff working with profoundly handicapped children was organized, the main concern of which was to improve the teaching approaches with such a population. The workshops were the result of an innovative attempt by the British Psychological Society's Standing Committee on Handicap to apply current knowledge of the real life problems of work settings in schools or hospitals where children are educated. The workshops covered a period of 3 months with approximately one term between the first and second. Participants attended in pairs, one member of each pair being either a clinical or educational psychologist, and a variety of problems presented by the children were tackled. This paper attempts to describe the structure and operation of the workshops, to evaluate their outcome, and to suggest ideas for the future of such an approach.

Antigenic variants of rabies virus

The authors studied nineteen street virus isolates from different regions of Canada using either anti-nucleocapsid and anti-glycoprotein monoclonal antibodies or cross-protection tests. This study only allowed us to recognize three groups of viruses with different nucleocapsid patterns, and no difference, as far as protection with a Pitmann-Moore vaccine is concerned, between four of these strains.

Experimental rabies in skunks: persistence of virus in denervated muscle at the inoculation site

Striped skunks (Mephitis mephitis) were inoculated into the denervated abductor digiti quinti muscle with street rabies virus. They were killed at various times after inoculation and several tissues were examined by immunofluorescence and light microscopy. Muscle at the inoculation site was examined electron microscopically. Rabies antigen was detected in muscle fibers first on day 7 and persisted until day 28. Light and electron microscopic lesions at the inoculation site included atrophic and degenerating muscle fibers and a few focal and regional endomysial accumulations of macrophages, lymphocytes and plasma cells. Scattered myocytes contained bodies of matrix, virions and anomalous tubular structures on electron microscopic examination. The results indicate that replication of rabies virus may occur in infected muscle fibers at the inoculation site until 28 days after exposure. This could contribute to variations in the incubation period for the first two to three months after exposure. However, the results do not support the contention that virus is contained in striated muscle cells throughout the long incubation periods.

Experimental rabies in skunks: immunofluorescence light and electron microscopic studies

Striped skunks (Mephitis mephitis) were inoculated into the abductor digiti quinti muscle with street rabies virus isolated from salivary glands of rabid skunks. Using the immunofluorescence technique, antigen was detected in muscle cells at the inoculation site before it was detected in the central nervous system. Neurons and their processes in nearly all regions of the brain, spinal cord, cerebrospinal ganglia, and peripheral nerves contained antigen in terminal stages of the disease. Electron microscopically, matrix (viral nucleocapsid), virions, and anomalous viral products were mainly in neuronal perikarya and dendrites, and less often in myelinated axons. Matrices, virions, and crystalloid structures were in muscle fibers at the inoculation site. Viral budding occurred on endoplasmic reticulum, neurotubules, and neuronal plasma membrane. In the brain and dorsal horn of the spinal cord, virus budded from the postsynaptic and adjacent dendritic or perikaryal plasma membrane. There was simultaneous esotropic uptake of these particles by adjacent axon terminals. The results strongly suggest that direct transneuronal transfer of virus from perikarya and dendrites to adjacent axon terminals is a mechanism in dissemination of rabies in the central nervous system of striped skunks. Variation in the length of the incubation period may be due partly to replication or virus in myocytes at the inoculation site and subsequent transfer to peripheral nerves.

Experimental rabies in skunks: oral, nasal, tracheal and intestinal exposure

Striped skunks (Mephitis mephitis) were exposed to challenge virus standard rabies virus by feeding infected mouse brain in suspension or as intact brain free choice, by forced feeding of suspension, and by intranasal, intratracheal and intraintestinal instillation of suspension. All of five skunks exposed intranasally, two of five exposed intratracheally and two of ten exposed by forced feeding developed rabies. None of the skunks exposed to challenge virus standard virus, by other methods, became rabid. Most of the survivors, when challenged intramuscularly with street rabies virus at six months, developed rabies. The results indicate that the skunk is much more susceptible to challenge virus standard rabies virus given intranasally than by the other methods used. When disease occurs following oral administration, infection may be associated with prolonged contact with buccal mucosa or accidental contact with nasal mucosa. Survivors had little or no protection when challenged intramuscularly with street rabies virus.

Experimental oral and nasal transmission of rabies virus in mice

Weanling female white Swiss mice were exposed to challenge virus standard rabies virus and street virus isolates from various domestic and wild animals. Virus was given free choice as suspension or as infected mouse brain by stomach tube, by single injection of suspension into the oral cavity of unanesthetized mice, by repeated injection into the oral cavity of anesthetized mice and by single application to the external nares of anesthetized mice. Challenge virus standard virus in mouse brain suspension and a suspension of skunk salivary glands infected with street virus (titers greater than or equal to 10(6)MICLD50/0.03 ml) consistently produced high rates of infection in mice exposed intranasally, low to high rates of infection in mice exposed by forced feeding and other artificial methods of oral exposure and very low rates of infection when given free choice. Street virus isolates passaged intracerebrally in mice had titers less than or equal to 10(4.5) MICLD50/0.03 ml and rarely caused rabies in mice exposed orally or nasally by any method. The results indicate that with the isolates used, virus of high titer (greater than or equal to 10(6)MICLD50/0.03 ml) is required to consistently produce infection in mice by the nasal route and that the mucosa of the nasal cavity probably is the chief route of infection even after oral administration.

The mouse inoculation test in rabies diagnosis: early diagnosis in mice during the incubation period

Brain tissue from 64 rabies suspect specimens were inoculated intracerebrally into twenty 9-12 gm adult Swiss white mice. Two mice from each specimen were killed on specific days postinoculation and examined for the presence of rabies virus by the fluorescent antibody staining technique. In this way a positive diagnosis was made in the majority of cases between postinoculation days 4 and 12 when the incubation period of these same specimens ranged between eight and 20 days.

Age and sex determination of striped skunks (Mephitis mephitis) from Ontario, Manitoba, and Quebec

The determination of age by the number of annular layers in the tooth cementum and the determination of sex by examination of the hippocampal neurons for sex chromatin are described. A total of 750 skunks, consisting of 351 females and 399 males, were examined. Of these, 376 were less than 1 year of age. The oldest animals were between 5 and 6 years of age.

Studies on the parasites of Chiroptera. 3. Helminths from various bat species collected in British Columbia

Eighty-two bats comprising the genera Eptesicus, Lasionycteris, Lasiurus, Myotis, and Plecotus collected in British Columbia were examined for the presence of gastrointestinal parasites. Helminths from 24 specimens of Eptesicus fuscus, 11 of Lasionycteris noctivagans, 1 of Lasiurus cinereus, 7 of Myotis californicus, 31 of M. lucifugus, and 3 of M. volans longicrus are listed. Some aspects of the parasitism encountered are discussed.

Demonstration of rabies antigen in salivary glands of rabies suspected animals

Submaxillary salivary glands from 129 rabies suspected animals were studied by the following methods: a) microscopic examination of frozen sections stained by the Fluorescent antibody technique (FAT), and b) mouse infectivity test (MIT). Flourescent antibody staining of frozen sections from the salivary glands of rabid animals proved to be a satisfactory method for demonstrating rabies antigen, when compared with the mouse infectivity test.