The Histopathogenesis of Paralytic Rabies in Six-Week-Old C57BL/6J Mice Following Inoculation of the CVS-11 Strain into the Right Triceps Surae Muscle

Abstract

ABSTRACT. A fatal encephalomyelitis was developed after intracerebral and hind limb inoculation of in 6-week-old C57BL/6J mice by the inoculation of fixed rabies virus (CVS-11 strain), intracerebrally and into hind. After the intracerebral inoculation, virus antigens were detected in the cerebral cortex and hippocampus at 2 days postinoculation (PI), and later spread centrifugally to thalamus, brain stem, cerebellum, spinal cord and spinal ganglia. At 4 days PI, severe apoptosis and DNA fragmentation were observed in the hippocampus and cerebral cortex. All mice infected intracerebrally were dead without limb paralysis at from 10 to 11 days PI. In contrast, mice infected with virus intramuscularly were persistently observed virus antigens in the myocytes at the site of inoculation from 2 days PI. At 4 days PI, the antigens were demonstrated in the spinal dorsal root ganglia, spinal cord and muscle spindles without their detection in the cerebrum and hippocampus. There were no apoptosis in the spinal cord and dorsal root ganglia, however hind limb paralysis was found in all infected mice. Hind limb paralysis was progressed to quadriparalysis, and mice were dead from 11 to 13 days PI. From 4 days PI, necrosis of neuron was observed in the the spinal and dorsal ganglia with infiltration of lymphocyte. This study suggested that the necrosis of spinal neurons was more important to cause the paralysis of hind limb rather than the severe cerebral infection and apoptosis in C57BL/6J mice infected with CVS-11 strain. The virus primarily replicated in the muscles was ascended the spinal cord via afferent fibers and retrogradely invaded the cerebrum, and with subsequent spread to muscle spindles. KEY WORDS: C57BL/6J mouse, encephalomyelitis, pathogenesis, rabies (CVS-11).

Involvement of the Rabies Virus Phosphoprotein Gene in Neuroinvasiveness

“…Previous histopathological studies showed that RABV replicates in muscle cells before infecting peripheral nerves, implying that viral replication in muscle cells enhances the infection of peripheral nerves (7)(8)(9)(10). However, this possibility has not been supported by experimental data showing a correlation between the abilities of the virus to replicate in muscle cells and to infect peripheral nerves.…”

“…Previous studies using both street and fixed RABV strains have demonstrated that muscle cells are the infection sites in peripheral tissue (7)(8)(9)(10)45). In this study, we compared in vivo replication efficiencies of the Ni-Luc, Ni-CE-Luc, and CE(NiP)-Luc strains in muscle and obtained data strongly suggesting that the Ni P gene, but not the Ni-CE P gene, mediates stable viral replication in muscle (Fig.…”

“…Previous histopathological studies using animals inoculated with street RABV strains (field isolates) or fixed RABV strains (laboratory and vaccine strains) via the intramuscular (i.m.) route have demonstrated the presence of the viral antigen in muscle cells prior to detection of the antigen in peripheral nerves (7)(8)(9)(10). These observations indicate the possibility that RABV replication in muscle cells contributes to efficient infection of peripheral nerves.…”

“…Mice were euthanized at 5 days postinoculation (dpi), and their brains, spinal cords at cervical spine 1 (C1) to the last lumbar vertebra, sciatic nerves, and thigh muscles were quickly collected. In another experiment, 10 mice per group were intramuscularly inoculated with 10 6 FFU of the Ni-CE or CE(NiP) strain, and their sciatic nerves and thigh muscles were collected at 8 dpi. Tissues were frozen in liquid nitrogen and stored at Ϫ80°C until being used for RNA extraction and reverse transcription (RT)-nested PCR.…”

Lesions of the Central Nervous System Induced by Intracerebral Inoculation of BALB/c Mice with Rabies Virus (CVS-11)

“…The spinal lesions were composed of the infiltration of T lymphocytes, the increase of microglial cells and astroglial cells and the majority of T lymphocytes exhibited apoptosis. In contrast, marked neuronal apoptosis was detected in the cerebral cortex, hippocampus and cerebellum of mice that were inoculated intracerebrally with CVS-11, but paralysis was absent [21]. Induction of apoptosis by fixed strain of rabies virus has been reported in vitro [19] and experimental animal models [11,13] to be associated with the expression level of the virus protein.…”