Martin H. Groschup

Polyclonal anti-PrP auto-antibodies induced with dimeric PrP interfere efficiently with PrPSc propagation in prion-infected cells.

Prion diseases are neurodegenerative infectious disorders for which no prophylactic regimens are known. In order to induce antibodies/auto-antibodies directed against surface-located PrPc, we used a covalently linked dimer of mouse prion protein expressed recombinantly in Escherichia coli. Employing dimeric PrP as an immunogen we were able to effectively overcome autotolerance against murine PrP in PrP wild-type mice without inducing obvious side effects. Treatment of prion-infected mouse cells with polyclonal anti-PrP antibodies generated in rabbit or auto-antibodies produced in mice significantly inhibited endogenous PrPSc synthesis. We show that polyclonal antibodies are binding to surface-located PrPc, thereby interfering with prion biogenesis. This effect is much more pronounced in the presence of full IgG molecules, which, unlike Fab fragments, seem to induce a significant cross-linking of surface PrP. In addition, we found immune responses against different epitopes when comparing antibodies induced in rabbits and PrP wild-type mice. Only in the auto-antibody situation in mice an immune reaction against a region of PrP is found that was reported to be involved in the PrPSc conversion process. Our data point to the possibility of developing means for an active immunoprophylaxis against prion diseases.

Glycosylation deficiency at either one of the two glycan attachment sites of cellular prion protein preserves susceptibility to bovine spongiform encephalopathy and scrapie infections.

The conversion into abnormally folded prion protein (PrP) plays a key role in prion diseases. PrPC carries two N-linked glycan chains at amino acid residues 180 and 196 (mouse). Previous in vitro data indicated that the conversion process may not require glycosylation of PrP. However, it is conceivable that these glycans function as intermolecular binding sites during the de novo infection of cells on susceptible organisms and/or play a role for the interaction of both PrP isoforms. Such receptor-like properties could contribute to the formation of specific prion strains. However, in earlier studies, mutations at the glycosylation sites of PrP led to intracellular trafficking abnormalities, which made it impossible to generate PrP glycosylation-deficient mice that were susceptible to bovine spongiform encephalopathy (BSE) or scrapie. We have now tested more than 25 different mutations at both consensus sites and found one nonglycosylated (T182N/T198A) and two monoglycosylated (T182N and T198A) mutants that rather retained authentic cellular trafficking properties. In vitro all three mutants were converted into PrPres. PrP mutant T182N/T198A also provoked a strong dominant-negative inhibition on the endogenous wild type PrP conversion reaction. By using the two monoglycosylated mutants, we generated transgenic mice overexpressing PrPC in their brains at levels of 2–4 times that of nontransgenic mice. Most interestingly, such mice proved readily susceptible to a challenge with either scrapie (Chandler and Me7) or with BSE. Incubation times were comparable or in some instances even significantly shorter than those of nontransgenic mice. These data indicate that diglycosylation of PrPC is not mandatory for prion infection in vivo.

Classical and Atypical Scrapie in Sheep and Goats

Scrapie is a naturally occuring transmissible spongiform encephalopathy (TSE) in sheep, goat and mufflons almost world-wide and is known for about 250 years. It is characterized by the accumulation of an abnormal isoform (PrPSc) of host encoded prion protein (PrPC) in the central nervous system which leads to progressive neurodegeneration and death. Scrapie represents the prototype of the so-called prion diseases. It is observed to date as two types, classical and atypical scrapie. The susceptibility to both types is modulated by polymorphisms of the prion gene. Whereas classical scrapie is clearly a naturally occurring transmissible disease, atypical scrapie may also be caused by the spontaneous misfolding of prion protein. This review gives an overview on the current knowledge of classical and atypical scrapie in sheep and goats with special emphasis on epidemiology, clinical and pathological signs, genetic susceptibilities, diagnosis and the characteristics of the most common scrapie strains.

Serological and genomic evidence of Rift Valley fever virus during inter-epidemic periods in Mauritania

Rift Valley fever virus (RVFV) is an emerging pathogen of major concern throughout Africa and the Arabian Peninsula, affecting both livestock and humans. In the past recurrent epidemics were reported in Mauritania and studies focused on the analysis of samples from affected populations during acute outbreaks. To verify characteristics and presence of RVFV during non-epidemic periods we implemented a multi-stage serological and molecular analysis. Serum samples of small ruminants, cattle and camels were obtained from Mauritania during an inter-epidemic period in 2012-2013. This paper presents a comparative analysis of potential variations and shifts of antibody presence and the capability of inter-epidemic infections in Mauritanian livestock. We observed distinct serological differences between tested species (seroprevalence: small ruminants 3·8%, cattle 15·4%, camels 32·0%). In one single bovine from Nouakchott, a recent RVF infection could be identified by the simultaneous detection of IgM antibodies and viral RNA. This study indicates the occurrence of a low-level enzootic RVFV circulation in livestock in Mauritania. Moreover, results indicate that small ruminants can preferably act as sentinels for RVF surveillance.

Immune response and viral replication in experimentally hepatitis E virus-infected wild boar and domestic pigs

7/9 contacts), starting from 35 days. In contrast, in single HEV infection, all animals started seroconverting from 14 days post-infection. The average duration of shedding was estimated to 48.6 days and the transmission rate to 0.7 animals / day, against 9.6 and 0.15 respectively, during infection with HEV alone. CONCLUSION: Co-infection of swine with HEV and PRRSV induces a chronic HEV infection with a delayed appearance of anti-HEV antibodies and a long term HEV excretion. This co-infection, common in pig herds, probably contributes to the high prevalence of HEV in the pig reservoir. The absence or delayed humoral response observed in animals is similar to that observed in humans. This HEV/PRRSV co-infection seems to be a relevant animal model to study the mechanisms involved in HEV chronic infection and possibly for the identification of new anti-viral compounds.