Impairment in auditory and visual function follows perinatal viral infection in the rat

Animal Model of Sensorineural Hearing Loss Associated with Lassa Virus Infection

Approximately one-third of Lassa virus (LASV)-infected patients develop sensorineural hearing loss (SNHL) in the late stages of acute disease or in early convalescence. With 500,000 annual cases of Lassa fever (LF), LASV is a major cause of hearing loss in regions of West Africa where LF is endemic. To date, no animal models exist that depict the human pathology of LF with associated hearing loss. Here, we aimed to develop an animal model to study LASV-induced hearing loss using human isolates from a 2012 Sierra Leone outbreak. We have recently established a murine model for LF that closely mimics many features of human disease. In this model, LASV isolated from a lethal human case was highly virulent, while the virus isolated from a nonlethal case elicited mostly mild disease with moderate mortality. More importantly, both viruses were able to induce SNHL in surviving animals. However, utilization of the nonlethal, human LASV isolate allowed us to consistently produce large numbers of survivors with hearing loss. Surviving mice developed permanent hearing loss associated with mild damage to the cochlear hair cells and, strikingly, significant degeneration of the spiral ganglion cells of the auditory nerve. Therefore, the pathological changes in the inner ear of the mice with SNHL supported the phenotypic loss of hearing and provided further insights into the mechanistic cause of LF-associated hearing loss.

IMPORTANCE

Sensorineural hearing loss is a major complication for LF survivors. The development of a small-animal model of LASV infection that replicates hearing loss and the clinical and pathological features of LF will significantly increase knowledge of pathogenesis and vaccine studies. In addition, such a model will permit detailed characterization of the hearing loss mechanism and allow for the development of appropriate diagnostic approaches and medical care for LF patients with hearing impairment.

Targeting Schwann cells by nonlytic arenaviral infection selectively inhibits myelination

Members of the arenavirus family, famous for their hemorrhagic syndromes, cause distinct neurological disorders; however, cellular and molecular targets as well as pathogenesis of peripheral nervous system disorders associated with these viruses are unknown. Using noncytolytic lymphocytic choriomeningitis virus, the prototype arenavirus, and pseudotyped Lassa fever virus, we showed that the Schwann cells, but not the neurons, were preferentially targeted and harbored the virus. This permissiveness was caused by the viral glycoprotein usage of its receptor alpha-dystroglycan, which was highly abundant on Schwann cell membranes. Persistent lymphocytic choriomeningitis virus infection rendered immature Schwann cells defective or incapable of forming compact myelin sheathes when they differentiated to myelinating phenotype in an in vitro differentiation model of Schwann cells. Persistent infection did not cause Schwann cell apoptosis or cytopathic effect. Defects in myelination coincided with the down-regulation of dystroglycan expression and disruption of the laminin-2 organization and basal lamina assembly on Schwann cell-axon units. The data provide evidence for a selective perturbation of laminin-2-laminin-2 receptor communication pathway in the peripheral nervous system by a nonlytic virus and the resulting myelin defects, which may partly contribute to neurological abnormalities associated with arenaviral infection.

Elicitation and modification of the acoustic startle reflex in animals prenatally exposed to cocaine

In separate experiments, pregnant Long-Evans rats were administered cocaine orally (60 mg/kg/day) on gestation days 14-21, or subcutaneously (40 mg/kg/day) on gestational days 8-21. For each route of administration, a vehicle control group was pair-fed to the group administered cocaine and another control group was left untreated. Throughout pregnancy, the dams that received cocaine gained approximately 15% less weight than the untreated controls, but none of the dosage procedures affected the size of the litters, or the weight and growth of the offspring. When the offspring reached adulthood, various assessments of reflex function were made using the acoustic startle reflex and prepulse inhibition of startle. There were no effects on startle habituation or reflex modification that could be attributed to the prenatal exposure to cocaine.