Ivermectin Inhibits the Replication of Usutu Virus In Vitro.

Usutu virus (USUV) is an emerging mosquito-borne arbovirus within the genus Flavivirus, family Flaviviridae. Similar to the closely related West Nile virus (WNV), USUV infections are capable of causing mass mortality in wild and captive birds, especially blackbirds. In the last few years, a massive spread of USUV was present in the avian population of Germany and other European countries. To date, no specific antiviral therapies are available. Nine different approved drugs were tested for their antiviral effects on the replication of USUV in vitro in a screening assay. Ivermectin was identified as a potent inhibitor of USUV replication in three cell types from different species, such as simian Vero CCL-81, human A549 and avian TME R. A 2- to 7-log10 reduction of the viral titer in the supernatant was detected at a non-cytotoxic concentration of 5 µM ivermectin dependent on the applied cell line. IC50 values of ivermectin against USUV lineage Africa 3 was found to be 0.55 µM in Vero CCL-81, 1.94 µM in A549 and 1.38 µM in TME-R cells. The antiviral efficacy was comparable between the USUV lineages Africa 2, Africa 3 and Europe 3. These findings show that ivermectin may be a candidate for further experimental and clinical studies addressing the treatment of USUV disease, especially in captive birds.

The Occurrence of a Commercial Npro and Erns Double Mutant BVDV-1 Live-Vaccine Strain in Newborn Calves.

The major source for the spread of bovine viral diarrhea virus (BVDV) are in-utero infected, immunotolerant, persistently infected (PI) animals since they shed enormous amounts of viruses throughout their lives. During the sequence-based virus typing of diagnostic ear notch samples performed in the context of the obligatory German BVDV eradication program, the commercial Npro and Erns double mutant BVDV-1 live-vaccine strain KE-9 was detected in seven newborn calves; their mothers were immunized in the first trimester of gestation. Six calves either succumbed or were culled immediately, but the one remaining animal was closely monitored for six months. The viral RNA was detected in the skin sample taken in its first and fifth week of life, but the virus could not be isolated. Further skin biopsies that were taken at monthly intervals as well as every serum and urine sample, nasal, oral, and rectal swabs taken weekly tested BVDV negative. However, neutralizing titers against BVDV-1 remained at a consistently high level. To further control for virus shedding, a BVDV antibody and antigen negative calf was co-housed which remained negative throughout the study. The missing viremia, a lack of excretion of infectious virus and negative follow-up skin samples combined with consistently high antibody titers speak against the induction of the classical persistent infection by vaccination with recombinant KE-9 during gestation. We, therefore, suggest that the epidemiological impact of the RNA/antigen positivity for an extended period in the skin is very low. The detection of live-vaccine viruses in skin biopsies mainly represents a diagnostic issue in countries that implemented ear notch-based control programs; and KE9-specific RT-PCRs or sequence analysis can be used to identify these animals and avoid culling measures.

Outbreak and Cocirculation of Three Different Usutu Virus Strains in Eastern Germany.

Usutu virus (USUV) is a mosquito-borne flavivirus accounting for large-scale deaths in resident bird populations. In this study, we show the introduction of USUV to Eastern Germany resulting in massive death of birds, particularly blackbirds (Turdus merula). We found that three diverse USUV lineages ("Europe 3," "Africa 2," and "Africa 3-like") circulated simultaneously. Moreover, we detected USUV in Culex pipiens in a region where no dead birds were reported, strengthening the need for mosquito monitoring to uncover the spread of arboviruses. Furthermore, phylogenetic analyses revealed that mutations accumulated, in particular, in the NS3 region within short time periods. In addition, comparison of whole-genome sequences showed that diverse isolates of the cluster "Africa 3-like" are cocirculating in Germany due to independent introduction events.

Generation of serotype 1/serotype 2 reassortant viruses of the infectious bursal disease virus and their investigation in vitro and in vivo.

Infectious bursal disease virus (IBDV) is the causative agent of acute or immunosuppressive disease in chickens. Serotype 1 strains are pathogenic whereas serotype 2 strains neither cause disease nor protect against infection with the serotype 1 strains. The target organ of serotype 1 strains is the bursa Fabricii (BF). The molecular determinants of this tropism, and therefore pathogenicity, are poorly understood. IBDV is a non-enveloped icosahedral virus particle of 60 nm in diameter, which contains two genome segments of double-stranded RNA. Here, the generation of interserotypic reassortants using the reverse genetics approach is reported. The results of in vitro and in vivo investigations show that genome segment A determines the bursa tropism of IBDV, whereas segment B is involved in the efficiency of viral replication; they further indicate the significance of the interaction of the polymerase (segment B) with the structural protein VP3 (segment A) or the viral genome for efficient virus formation and replication.

[Testing for BTV, BVDV and BHV-1 in blood samples of new world camelids kept in middle Germany]. / Untersuchungen von Blutproben im mitteldeutschen Raum gehaltener Neuweltkameliden auf BTV-, BVDV- und BHV-1.

The susceptibility of camelids for infectious agents which may result in severe economic losses or which are strictly regulated for epidemiological reasons in farm animals potentially causes a mutual risk of transmission. This study aimed to investigate the presence of antibodies against bovine herpesvirus 1 (BHV-1), bluetongue virus (BTV) and bovine viral diarrhoea virus (BVDV) as well as the presence of pestivirus antigen in new world camelids in Central Germany. Therefore 107 serum samples from 93 alpacas and lamas from this region which had been obtained from 2007 to 2009 were examined using ELISA, serum neutralisation test, RT-PCR and a pestivirus specific gene probe. All sample were negative for BHV-1 antibodies. Antibodies against BVDV-1 could be detected in four animals, titres reaching from 1:64 to > 1:256. One animal was positive for BTV antibodies in the year 2008. This animal had been tested negative for BTV antibodies in 2007. It can be concluded that up to now, these viruses seem to be of minor importance as pathogens in new world camelids in Central Germany. Therefore the risk of infection originating from new world camelids for production animals could be considered to be rather low in this region at the moment. However, it must be taken into consideration that these animals due to lack of antibodies are fully susceptible in case of occurrence of one of these viruses. For maintenance and improvement of the present status, general hygienic precautions should be applied; direct and indirect contact between animals from different herds must be avoided and virological diagnostic and quarantine should be required trading these animals.

Novel polyomavirus detected in the feces of a chimpanzee by nested broad-spectrum PCR.

In order to screen for new polyomaviruses in samples derived from various animal species, degenerated PCR primer pairs were constructed. By using a nested PCR protocol, the sensitive detection of nine different polyomavirus genomes was demonstrated. The screening of field samples revealed the presence of a new polyomavirus, tentatively designated chimpanzee polyomavirus (ChPyV), in the feces of a juvenile chimpanzee (Pan troglodytes). Analysis of the region encoding the major capsid protein VP1 revealed a unique insertion in the EF loop of the protein and showed that ChPyV is a distinct virus related to the monkey polyomavirus B-lymphotropic polyomavirus and the human polyomavirus JC polyomavirus.

Apoptosis is induced by infectious bursal disease virus replication in productively infected cells as well as in antigen-negative cells in their vicinity.

The kinetics of infectious bursal disease virus (IBDV) replication and induction of apoptosis were investigated in vitro and in vivo. After infection of chicken embryo (CE) cells with IBDV strain Cu-1, the proportion of apoptotic cells increased from 5.8% at 4 h post-infection (p.i.) to 64.5% at 48 h p.i. The proportion of apoptotic cells correlated with IBDV replication. UV-inactivated IBDV particles did not induce apoptosis. Double labelling revealed that, early after infection, the majority of antigen-expressing cells were not apoptotic; double-labelled cells appeared more frequently at later times. Remarkably, apoptotic cells were frequently located in the vicinity of antigen-expressing cells. This indicated that an apoptosis-inducing factor(s) might be released by cells that replicate IBDV. Since interferon (IFN) production has been demonstrated after IBDV infection, IFN was considered to be one of several factors. However, supernatants of infected CE cells in which virus infectivity had been neutralized were not sufficient to induce apoptosis. Similar results were observed in the infected bursae of Fabricius: early after infection, most of the cells either showed virus antigens or were apoptotic. Again, double-labelled cells appeared more frequently late after infection. This suggests that indirect mechanisms might also be involved in the induction of apoptosis in vivo, contributing to the rapid depletion of cells in the IBDV-infected bursa.