Cerebrospinal Aß11-x and 17-x levels as indicators of mild cognitive impairment and patients' stratification in Alzheimer's disease.

In the present work, the concentrations of Aß11-x and Aß17-x peptides (x=40 or 42), which result from the combined cleavages of ß-amyloid precursor protein (AßPP) by ß'/α or α/γ-secretases, respectively, were assessed in cerebrospinal fluid (CSF) samples from patients with Alzheimer's disease (AD) or mild cognitive impairment (MCI). Specific multiplexed assays were set up using new anti-40 and anti-42 monoclonal antibodies (mAbs) for the capture of these N-truncated Aß peptides and anti-11 or anti-17 mAbs for their detection. The specificity, sensitivity and reproducibility of such assays were assessed using synthetic peptides and human cell models. Aß11-x and Aß17-x were then measured in CSF samples from patients with AD (n=23), MCI (n=23) and controls with normal cognition (n=21). Aß11-x levels were significantly lower in patients with MCI than in controls. Compared with the combined quantification of Aß1-42, total Tau (T-Tau) and phosphorylated Tau (P-Tau; AlzBio3, Innogenetics), the association of Aß11-40, Aß17-40 and T-Tau improved the discrimination between MCI and controls. Furthermore, when patients with MCI were classified into two subgroups (MCI ≤1.5 or ≥2 based on their CDR-SB (Cognitive Dementia Rating-Sum of Boxes) score), the CSF Aß17-40/Aß11-40 ratio was significantly higher in patients with CDR-SB ≤1.5 than in controls, whereas neither Aß1-42, T-Tau nor P-Tau allowed the detection of this subpopulation. These results need to be confirmed in a larger clinical prospective cohort.

Long-term storage at tropical temperature of dried-blood filter papers for detection and genotyping of RNA and DNA viruses by direct PCR.

In tropical countries the diagnosis of viral infections of humans or animals is often hampered by the lack of suitable clinical material and the necessity to maintain a cold chain for sample preservation up to the laboratory. This study describes the use of filter papers for rapid sample collection, and the molecular detection and genotyping of viruses when stored over long periods at elevated temperatures. Infected blood was collected on filter papers, dried and stored at different temperatures (22, 32 and 37 degrees C) for various periods (up to 9 months). Two animal viruses, African swine fever, a large double-stranded DNA virus and Peste des Petits Ruminants, a negative single-stranded RNA virus, were used to validate the method. Filter papers with dried blood containing virus or control plasmid DNA were cut in small 5mm(2) pieces and added directly to the PCR tube for conventional PCR. Nucleic acid from both viruses could still be detected after 3 months at 32 degrees C. Moreover, the DNA virus could be detected at least 9 months after conservation at 37 degrees C. PCR products obtained from the filter papers were sequenced and phylogenetic analysis carried out. The results were consistent with published sequences, demonstrating that this method can be used for virus genotyping.