Prion seeding activity and infectivity in skin samples from patients with sporadic Creutzfeldt-Jakob disease

Sporadic Creutzfeldt-Jakob disease (sCJD), the most common human prion disease, is transmissible through iatrogenic routes due to abundant infectious prions [misfolded forms of the prion protein (PrP^Sc)] in the central nervous system (CNS). Some epidemiological studies have associated sCJD risk with non-CNS surgeries. We explored the potential prion seeding activity and infectivity of skin from sCJD patients. Autopsy or biopsy skin samples from 38 patients [21 sCJD, 2 variant CJD (vCJD), and 15 non-CJD] were analyzed by Western blotting and real-time quaking-induced conversion (RT-QuIC) for PrP^Sc Skin samples from two patients were further examined for prion infectivity by bioassay using two lines of humanized transgenic mice. Western blotting revealed dermal PrP^Sc in one of five deceased sCJD patients and one of two vCJD patients. However, the more sensitive RT-QuIC assay detected prion seeding activity in skin from all 23 CJD decedents but not in skin from any non-CJD control individuals (with other neurological conditions or other diseases) during blinded testing. Although sCJD patient skin contained ~10³- to 10⁵-fold lower prion seeding activity than did sCJD patient brain tissue, all 12 mice from two transgenic mouse lines inoculated with sCJD skin homogenates from two sCJD patients succumbed to prion disease within 564 days after inoculation. Our study demonstrates that the skin of sCJD patients contains both prion seeding activity and infectivity, which raises concerns about the potential for iatrogenic sCJD transmission via skin.

Prion Protein Protects against Renal Ischemia/Reperfusion Injury

The cellular prion protein (PrP^C), a protein most noted for its link to prion diseases, has been found to play a protective role in ischemic brain injury. To investigate the role of PrP^C in the kidney, an organ highly prone to ischemia/reperfusion (IR) injury, we examined wild-type (WT) and PrP^C knockout (KO) mice that were subjected to 30-min of renal ischemia followed by 1, 2, or 3 days of reperfusion. Renal dysfunction and structural damage was more severe in KO than in WT mice. While PrP was undetectable in KO kidneys, Western blotting revealed an increase in PrP in IR-injured WT kidneys compared to sham-treated kidneys. Compared to WT, KO kidneys exhibited increases in oxidative stress markers heme oxygenase-1, nitrotyrosine, and N^ε-(carboxymethyl)lysine, and decreases in mitochondrial complexes I and III. Notably, phosphorylated extracellular signal-regulated kinase (pERK) staining was predominantly observed in tubular cells from KO mice following 2 days of reperfusion, a time at which significant differences in renal dysfunction, histological changes, oxidative stress, and mitochondrial complexes between WT and KO mice were observed. Our study provides the first evidence that PrP^C may play a protective role in renal IR injury, likely through its effects on mitochondria and ERK signaling pathways.

Preservation of Rhizobium viability and symbiotic infectivity by suspension in water

Three Rhizobium japonicum strains and two slow-growing cowpea-type Rhizobium strains were found to remain viable and able to rapidly modulate their respective hosts after being stored in purified water at ambient temperatures for periods of 1 year and longer. Three fast-growing Rhizobium species did not remain viable under the same water storage conditions. After dilution of slow-growing Rhizobium strains with water to 10(3) to 10(5) cells ml-1, the bacteria multiplied until the viable cell count reached levels of between 10(6) and 10(7) cells ml-1. The viable cell count subsequently remained fairly constant. When the rhizobia were diluted to 10(7) cells ml-1, they did not multiply, but full viability was maintained. If the rhizobia were washed and suspended at 10(9) cells ml-1, viability slowly declined to 10(7) cells ml-1 during 9 months of storage. Scanning electron microscopy showed that no major morphological changes took place during storage. Preservation of slow-growing rhizobia in water suspensions could provide a simple and inexpensive alternative to current methods for the preservation of rhizobia for legume inoculation.