Systemic AA-amyloidosis is a protein-misfolding disease that is characterized by fibril deposition of serum amyloid-A protein (SAA) in several organs in humans and many animal species. Fibril deposits originate from abnormally high serum levels of SAA during chronic inflammation. In domestic short-hair cats, AA-amyloidosis has only been anecdotally reported and is considered a rare disease. Here we report that an astonishing 57-73% of early deceased short-hair cats kept in three independent shelters suffer from amyloid deposition in the liver, spleen, or kidney. Histopathology and mass spectrometry of post-mortem extracted deposits identified SAA as the major protein source. The duration of stay in the shelters was positively associated with a histological score of AA-amyloidosis (B=0.026, CI95%=0.007-0.046; p=0.010). Presence of SAA fragments in bile secretions raises the possibility of fecal-oral transmission of the disease.

Prion protein (PrP) is present at extremely low levels in the blood of animals and its detection is complicated by the poor sensitivity of current standard methodologies. Interesting results have been obtained with recent advanced technologies that are able to detect minute amounts of the pathological PrP (PrPSc), but their efficiency is reduced by various factors present in blood. In this study, we were able to extract cellular PrP (PrPC) from plasma-derived exosomes by a simple, fast method without the use of differential ultracentrifugation and to visualize it by Western blotting, reducing the presence of most plasma proteins. This result confirms that blood is capable of releasing PrP in association with exosomes and could be useful to better study its role in the pathogenesis of transmissible spongiform encephalopathies.

Prion protein (PrP) is encoded by the PRNP gene, which is highly polymorphic in goats, with polymorphisms encoding amino acid substitutions at the protein level. In the current study, the reactivity of monoclonal antibody (mAb) F99/97.6.1 in binding PrP from goats polymorphic at PRNP codon 222 was investigated. Nervous tissue from 30 scrapie-negative goats with 3 different genotypes (222Q/Q, 222Q/K, and 222K/K) was analyzed by Western blot using mAbs P4 and F99/97.6.1. Although PrP was detected in all 30 samples by mAb P4, detection of PrP by mAb F99/97.6.1 was limited to 222Q/Q (12/12). No PrP was detected by mAb F99/97.6.1 in the 222K/K samples ( n = 6), and the signal intensity of mAb F99/97.6.1 for PrP was lower for the 222Q/K samples (12/12 samples). To further investigate these results, additional Western blot analyses were performed, and the PrP signals detected by mAbs F99/97.6.1 and SAF84 were then quantified. The mean F99/SAF84 ratio (± standard deviation) calculated for the 222Q/Q group was 0.73 ± 1.26, and the mean for the 222Q/K group was 0.27 ± 1.31. Statistical analysis of these values evidenced statistically significant differences between the 222Q/Q and 222Q/K samples. The results of the study thus revealed an inhibition by lysine at position 222 on the binding of mAb F99/97.6.1 to goat PrP. This has implications for the use of mAb F99/97.6.1 for diagnostic purposes. Because the 222K allele could be a target for genetic selection in goats, the differential reactivity of mAb F99/97.6.1 could be exploited with a genotyping test setup.

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Corticosteroids have become the most widespread illegal growth promoters in veal calves and beef cattle. Testing for corticosteroids relies on either direct detection of compounds or their metabolites or indirect detection to identify changes in biological pathways. We used a comparative proteomic approach, based on two-dimensional electrophoresis (2DE), to identify plasma protein markers after short-term dexamethasone administration in veal calves. Twenty-three male Friesian veal calves were treated experimentally with dexamethasone sodium phosphate: 10 received low-dose administration of the drug (0.4 mg day⁻¹ per os) for 20 consecutive days (treatment group); 10 received the drug at therapeutic dosage (2-4 mg kg⁻¹ i.m.) for 3 consecutive days (comparison group). Three animals were not treated (control group). Plasma samples were collected from each animal at six time points (T1-T6; treatment and control group) and at four time points (T1-T4; comparison group) and stored at -80°C until analysis. Plasma proteins were quantified and analysed in triplicate by 2DE. The images were analysed with Bionumerics® software. Comparison of 2DE maps obtained from blood samples at T1 (before treatment) and at T6 (final sampling) showed a significant disappearance (p < 0.001) of two protein spots at T6 in the treatment group. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis and immunoblotting identified these isoforms as serum paraoxonase/arylesterase 1 precursor (PON1). Synthesised in the liver and released into the blood, PON1 has an important role in lipid metabolism. The absence of variation of this protein in the comparison group suggests that the marker has good specificity for detecting illicit corticosteroid treatment.