RESUMEN
The histopathological response of scrapie-infected hamsters treated at the late stage of the infection with an "anti-scrapie" drug, a polyene macrolide antibiotic designated MS-8209, was evaluated in the brain. The results showed that (1) MS-8209 prolonged significantly the incubation time of the experimental disease, (2) MS-8209 delayed the appearance of spongiosis and astrogliosis in the brain, (3) immunodetection of abnormal prion protein and glial fibrillary acidic protein was significantly reduced in the central nervous system. In addition, this report indicates that polyene antibiotics markedly delay the development of the classical brain lesions that result from scrapie infection.
Asunto(s)
Anfotericina B/análogos & derivados , Antivirales/uso terapéutico , Astrocitos/efectos de los fármacos , Encéfalo/efectos de los fármacos , Gliosis/tratamiento farmacológico , Priones/metabolismo , Scrapie/tratamiento farmacológico , Anfotericina B/uso terapéutico , Animales , Antibacterianos/uso terapéutico , Astrocitos/patología , Western Blotting , Encéfalo/metabolismo , Encéfalo/patología , Cricetinae , Modelos Animales de Enfermedad , Edema/tratamiento farmacológico , Femenino , Proteína Ácida Fibrilar de la Glía/metabolismo , Gliosis/patología , Inmunohistoquímica , Mesocricetus , Scrapie/metabolismo , Scrapie/patologíaRESUMEN
Studies of abnormal prion protein (PrPres) are hindered by the lack of specific monoclonal antibodies (mAbs), and the relationships between PrPres, infectivity, and strain specificity in prion diseases are still subject to debate. We have studied PrPres with new mAbs produced against PrP in mice using various immunization strategies. PrPres was analyzed by Western blot with different prion strains in various hosts. Differences in the electrophoretic pattern of human PrPres revealed by these antibodies provide new insight into PrPres cleavage by proteases and interpretation of strain typing. This study confirms that the N-terminal extremity of PrPres is differentially sensitive to proteases. Conversely, the C-terminal extremity, which resists proteolysis, seems to be abnormally detectable by antibodies in ultrastructural studies. This work confirms the highly complex role of PrPres in prion diseases and provides new tools which will be made available to facilitate progress in qualitative and quantitative studies of PrP.
Asunto(s)
Anticuerpos Monoclonales , Priones/inmunología , Secuencia de Aminoácidos , Animales , Especificidad de Anticuerpos , Síndrome de Creutzfeldt-Jakob/etiología , Cricetinae , Encefalopatía Espongiforme Bovina/etiología , Humanos , Inmunización , Ratones , Microscopía Inmunoelectrónica , Datos de Secuencia Molecular , Enfermedades por Prión/etiología , Priones/genética , Priones/ultraestructura , Scrapie/etiología , Especificidad de la EspecieRESUMEN
Amphotericin B (AmB) has been shown to delay hamster scrapie. Infectivity studies have been performed previously using AmB in order to understand the relationship between the accumulation of an abnormal isoform (PrPres) of the prion protein and 263K scrapie agent replication in the brain. The first study reported that AmB had no effect upon agent replication, although it delayed the development of both clinical signs and PrPres accumulation. However, subsequent experiments using the same model showed a significant effect both on agent replication and PrPres accumulation early in infection. This fundamental discrepancy was assumed to be linked to differences in experimental protocols. In order to unravel the issue, a new experiment has been performed encompassing different protocols and using an AmB derivative, MS-8209, that can be used at higher doses because of its lower toxicity. The findings of this study exclude the suspected differences in the protocols as the reason for previous conflicting results, and suggest strongly that these discrepancies were due to a low dose of AmB causing a 'threshold effect'. Overall, this study indicates that, in this model, PrPres cannot be dissociated from infectivity by polyene antibiotics.
Asunto(s)
Anfotericina B/análogos & derivados , Antivirales/farmacología , Proteínas PrPSc/efectos de los fármacos , Anfotericina B/farmacología , Animales , Cricetinae , Relación Dosis-Respuesta a Droga , Femenino , Mesocricetus , Proteínas PrPSc/metabolismoRESUMEN
Amphotericin B (AmB) is one of the few drugs able to prolong survival times in experimental scrapie and delays the accumulation of PrPres, a specific marker of this disease in the brain in vivo. Previous reports showed that the AmB effect is observed only if the drug is administered around the time of infection. In the present study, intracerebrally infected mice were treated with AmB or one of its derivatives, MS-8209, between 80 and 140 days postinoculation. We observed an increased incubation time and a delay in PrPres accumulation and glial fibrillary acidic protein gene expression. Treatment starting at 80 days postinoculation was as efficient as long-term treatment starting the day of inoculation. Our results indicate that polyene antibiotics may interfere, throughout the course of the experimental disease, with the propagation of the scrapie agent.