Time-course studies of 14-3-3 protein isoforms in cerebrospinal fluid and brain of primates after oral or intracerebral infection with bovine spongiform encephalopathy agent

Abstract

Experimental transmission of bovine spongiform encephalopathy (BSE) to cynomolgus monkeys (Macaca fascicularis) is an animal model for variant Creutzfeldt–Jakob disease (vCJD). The presence of 14-3-3 proteins in cerebrospinal fluid (CSF) samples indicates neuronal destruction and is therefore used as a clinical biomarker. However, time-course studies using 14-3-3 proteins have not been performed until now in simian vCJD. The main goals of this study were to determine isoform patterns, to examine kinetics and to correlate the clinical course with the occurrence of this biomarker in simian vCJD. In monkeys dosed intracerebrally with BSE, the earliest clinical sign of illness was a drop in body weight that was detected months before the onset of mild neurological signs. Macaques dosed orally or intracerebrally with BSE developed neurological signs 4.3 (3.7–4.6) and 4.8 (2.9–6.0) years post-infection, respectively. 14-3-3β- and -γ-positive CSF samples were found around the time of onset of mild neurological signs, but not earlier. In contrast, 14-3-3ϵ and -ηisoforms were not detectable. 14-3-3 levels increased with time and were positively correlated with the degree of neurological symptoms. Post-mortem examination of brain samples revealed a positive correlation between PrPresand 14-3-3ϵ levels. Interestingly, florid plaques characteristic of human vCJD could not be detected in diseased monkeys. It was concluded that analysis of 14-3-3 proteins in CSF is a reliable tool to characterize the time course of brain degeneration in simian vCJD. However, there are differences in the clinical course between orally and intracerebrally infected animals that may influence the detection of other biomarkers.