Stefan Finke

Raccoons (Procyon lotor) in Germany as potential reservoir species for Lyssaviruses

Raccoons can be found almost everywhere in Germany since their first successful introduction in 1934. Although the animal is a well-known reservoir species for rabies in the USA, during the last European fox rabies epizootic, only a few rabid raccoons were reported from Germany. In recent years, the raccoon population density has increased tremendously, especially in (semi) urban settings. Presently, Germany is free of terrestrial wildlife rabies. To assess the potential risk that the raccoon population in Germany could act as a reservoir species upon reemergence of rabies, the susceptibility of the local raccoon population was investigated. Wild-caught animals were inoculated with the most likely lyssavirus variants to infect the local population. It was shown that the raccoons were fully susceptible for a dog and raccoon rabies virus isolate. Also, five of six raccoons inoculated with a fox rabies virus isolate showed clinical signs. However, none of the raccoons infected with European Bat Lyssavirus type 1 succumbed to rabies; meanwhile, all these raccoons seroconverted. It is concluded that the highest risk for the raccoon population in Germany to become infected with lyssaviruses is through the importation of rabies infected dogs.

The lyssavirus host-specificity conundrum — rabies virus — the exception not the rule

Lyssaviruses are a diverse range of viruses which all cause the disease rabies. Of the 16 recognized species, only rabies viruses (RABV) have multiple host reservoirs. Although lyssaviruses are capable of infecting all mammals, onward transmission in a new host population requires adaptation of the virus, in a number of stages with both host and virus factors determining the outcome. Due to an absence of recorded non-RABV host shifts, RABV data is extrapolated to draw conclusions for all lyssaviruses. In this article, we have focused on evidence of host shifts in the same insectivorous bat reservoir species in North America (RABV) and Europe (EBLV-1, EBLV-2 and BBLV). How RABV has successfully crossed species barriers and established infectious cycles in new hosts to be the global multi-host pathogen it is today, whilst other lyssaviruses appear restricted in host species is explored in this review. It hypothesized that RABV is the exception, rather than the rule, in this fascinating genus of viruses.

Isolation, antigenicity and immunogenicity of Lleida bat lyssavirus

The lyssaviruses are an important group of viruses that cause a fatal encephalitis termed rabies. The prototypic lyssavirus, rabies virus, is predicted to cause more than 60 000 human fatalities annually. The burden of disease for the other lyssaviruses is undefined. The original reports for the recently described highly divergent Lleida bat lyssavirus were based on the detection of virus sequence alone. The successful isolation of live Lleida bat lyssavirus from the carcass of the original bat and in vitro characterization of this novel lyssavirus are described here. In addition, the ability of a human rabies vaccine to confer protective immunity following challenge with this divergent lyssavirus was assessed. Two different doses of Lleida bat lyssavirus were used to challenge vaccinated or naïve mice: a high dose of 100 focus-forming units (f.f.u.) 30 µl-1 and a 100-fold dilution of this dose, 1 f.f.u. 30 µl-1. Although all naïve control mice succumbed to the 100 f.f.u. 30 µl-1 challenge, 42 % (n=5/12) of those infected intracerebrally with 1 f.f.u. 30 µl-1 survived the challenge. In the high-challenge-dose group, 42 % of the vaccinated mice survived the challenge (n=5/12), whilst at the lower challenge dose, 33 % (n=4/12) survived to the end of the experiment. Interestingly, a high proportion of mice demonstrated a measurable virus-neutralizing antibody response, demonstrating that neutralizing antibody titres do not necessarily correlate with the outcome of infection via the intracerebral route. Assessing the ability of existing rabies vaccines to protect against novel divergent lyssaviruses is important for the development of future public health strategies.

Rapid Reverse Genetics Systems for Rhabdoviruses: From Forward to Reverse and Back Again

Methods to recover recombinant negative strand RNA viruses (rNSVs) from cloned cDNAs have been significantly improved in more than two decades of NSV reverse genetics . In particular, for non-segmented negative strand RNA viruses (NNSVs ) like rhabdoviruses , time-consuming generation of reverse genetics systems by stitching PCR subfragments of genomic rhabdovirus cDNAs using ligase-based conventional cloning approaches limited the number of available recombinant virus cDNA clones. As genetic variability is considered an intrinsic feature of RNA viruses, it is thus reasonable to conclude that reverse genetics approaches to investigate natural virus functions and pathogenesis require improved systems that reflect the complexity of naturally occurring wild-type viruses, and that largely exclude adaption to cell culture conditions.In order to allow rapid cloning of wild-type NSV genome populations into reverse genetics vector plasmids, we developed a system in which cDNA copies of complete rhabdovirus populations are inserted into a plasmid bank by linear-to-linear homologous RecE/T recombination (LLHR ). Limited requirements for sequence information a priori, high cloning efficiencies, and the possibility to directly generate recombinant viruses from individual cDNA clones now offer novel opportunities to combine forward genetic dissection of natural rhabdovirus populations and downstream reverse genetics approaches.