Histopathology and immunohistochemistry of tissues outside central nervous system in bovine rabies

Transactivation response DNA-binding protein of 43 kDa proteinopathy and lysosomal abnormalities in spastic paraplegia type 11

Spastic paraplegia type 11 (SPG11) is the most common autosomal recessive hereditary spastic paraplegia with thinning of the corpus callosum. Spatacsin, a protein encoded by the SPG11 gene, is associated with autophagy. SPG11 patients show spastic paraplegia, intellectual disability, dementia, and parkinsonism. A previous neuropathological analysis of SPG11 cases reported neurodegeneration mimicking amyotrophic lateral sclerosis without transactivation response DNA-binding protein of 43 kDa (TDP-43) deposits and unique sequestosome 1 (SQSTM1)-positive neuronal inclusions. We performed a neuropathological examination of two Japanese patients with complicated spastic paraplegia with thinning of the corpus callosum from different families, and one was genetically diagnosed as having SPG11. Both cases showed diffuse atrophy of the brain and spinal cord. Depigmentation of the substantia nigra was also observed. Immunohistochemistry revealed widespread distribution of areas showing TDP-43 aggregation in the central nervous system. The TDP-43 deposits in the thalamus and substantia nigra especially resembled skein-like inclusions. Unique SQSTM1-positive neuronal inclusions, as previously reported, were widespread in the whole central nervous system as well as the dorsal root ganglia. Double-labeling immunofluorescence of the dorsal root ganglia revealed that the unique, large SQSTM1-positive cytoplasmic inclusions of the ganglion cells were labeled with lysosome-associated membrane protein 1 and lysosome-associated membrane protein 2. This is the first report showing TDP-43 pathology in SPG11. The common neuropathological findings of TDP-43-positive inclusions in both the cases imply a causal connection between the TDP-43 proteinopathy and autophagy dysfunction in SPG11.

A rabies virus vampire bat variant shows increased neuroinvasiveness in mice when compared to a carnivore variant

Rabies is one of the most important zoonotic diseases and is caused by several rabies virus (RABV) variants. These variants can exhibit differences in neurovirulence, and few studies have attempted to evaluate the neuroinvasiveness of variants derived from vampire bats and wild carnivores. The aim of this study was to evaluate the neuropathogenesis of infection with two Brazilian RABV street variants (variant 3 and crab-eating fox) in mice. BALB/c mice were inoculated with RABV through the footpad, with the 50% mouse lethal dose (LD₅₀) determined by intracranial inoculation. The morbidity of rabies in mice infected with variant 3 and the crab-eating fox strain was 100% and 50%, respectively, with an incubation period of 7 and 6 days post-inoculation (dpi), respectively. The clinical disease in mice was similar with both strains, and it was characterized initially by weight loss, ruffled fur, hunched posture, and hind limb paralysis progressing to quadriplegia and recumbency at 9 to 12 dpi. Histological lesions within the central nervous system (CNS) characterized by nonsuppurative encephalomyelitis with neuronal degeneration and necrosis were observed in mice infected with variant 3 and those infected with the crab-eating fox variant. However, lesions and the presence of RABV antigen, were more widespread within the CNS of variant-3-infected mice, whereas in crab-eating fox-variant-infected mice, RABV antigens were more restricted to caudal areas of the CNS, such as the spinal cord and brainstem. In conclusion, the results shown here demonstrate that the RABV vampire bat strain (variant 3) has a higher potential for neuroinvasiveness than the carnivore variant.