Disruption of influenza virus packaging signals results in various misassembled genome complexes

IMPORTANCE

The influenza A virus genome consists of eight distinct viral RNAs (vRNAs) that are typically packaged into a single virion as an octameric complex. How this genome complex is assembled and incorporated into the virion is poorly understood, but previous research suggests a coordinative role for packaging signals present in all vRNAs. Here, we show that disruption of two packaging signals in a model H7N7 influenza A virus results in a mixture of virions with unusual vRNA content, including empty virions, virions with one to four vRNAs, and virions with octameric complexes composed of vRNA duplicates. Our results suggest that (i) the assembly of error-free octameric complexes proceeds through a series of defined vRNA sub-complexes and (ii) virions can bud without incorporating complete octameric complexes.

The non-classical major histocompatibility complex II protein SLA-DM is crucial for African swine fever virus replication

African swine fever virus (ASFV) is a lethal animal pathogen that enters its host cells through endocytosis. So far, host factors specifically required for ASFV replication have been barely identified. In this study a genome-wide CRISPR/Cas9 knockout screen in porcine cells indicated that the genes RFXANK, RFXAP, SLA-DMA, SLA-DMB, and CIITA are important for productive ASFV infection. The proteins encoded by these genes belong to the major histocompatibility complex II (MHC II), or swine leucocyte antigen complex II (SLA II). RFXAP and CIITA are MHC II-specific transcription factors, whereas SLA-DMA/B are subunits of the non-classical MHC II molecule SLA-DM. Targeted knockout of either of these genes led to severe replication defects of different ASFV isolates, reflected by substantially reduced plating efficiency, cell-to-cell spread, progeny virus titers and viral DNA replication. Transgene-based reconstitution of SLA-DMA/B fully restored the replication capacity demonstrating that SLA-DM, which resides in late endosomes, plays a crucial role during early steps of ASFV infection.

A new duplex qPCR-based method to quantify Mycoplasma mycoides in complex cell culture systems and host tissues

Bacterial pathogen-host interactions are a complex process starting with adherence and colonization followed by a variety of interactions such as invasion or cytotoxicity on one hand and pathogen recognition, secretion of proinflammatory/antibacterial substances and enhancing the barrier function of epithelial layers on the other hand. Therefore, a variety of in vitro, ex vivo and in vivo models have been established to investigate these interactions. Some in vitro models are composed of different cell types and extracellular matrices such as tissue explants or precision cut lung slices. These complex in vitro models mimic the in vivo situation more realistically, however, they often require new and more sophisticated methods for quantification of experimental results. Here we describe a multiplex qPCR-based method to quantify the number of bacteria of Mycoplasma (M.) mycoides interacting with their hosts in an absolute manner as well as normalized to the number of host cells. We choose the adenylate kinase (adk) gene from the pathogen and the Carcinoembryonic antigen-related cell adhesion molecule 18 (CEACAM18) gene from the host to determine cell numbers by a TaqMan-based assay system. Absolute copy numbers of the genes are calculated according to a standard containing a defined number of plasmids containing the sequence which is amplified by the qPCR. The new multiplex qPCR therefore allows the quantification of M. mycoides interacting with host cells in suspension, monolayer, 3D cell culture systems as well as in host tissues.

Detection of Novel Poxvirus from Gray Seal (Halichoerus grypus), Germany

We detected a novel poxvirus from a gray seal (Halichoerus grypus) from the North Sea, Germany. The juvenile animal showed pox-like lesions and deteriorating overall health condition and was finally euthanized. Histology, electron microscopy, sequencing, and PCR confirmed a previously undescribed poxvirus of the Chordopoxvirinae subfamily, tentatively named Wadden Sea poxvirus.

TGF-β/IFN-γ Antagonism in Subversion and Self-Defense of Phase II Coxiella burnetii-Infected Dendritic Cells

Dendritic cells (DCs) belong to the first line of innate defense and come into early contact with invading pathogens, including the zoonotic bacterium Coxiella burnetii, the causative agent of Q fever. However, the pathogen-host cell interactions in C. burnetii-infected DCs, particularly the role of mechanisms of immune subversion beyond virulent phase I lipopolysaccharide (LPS), as well as the contribution of cellular self-defense strategies, are not understood. Using phase II Coxiella-infected DCs, we show that impairment of DC maturation and MHC I downregulation is caused by autocrine release and action of immunosuppressive transforming growth factor-β (TGF-β). Our study demonstrates that IFN-γ reverses TGF-β impairment of maturation/MHC I presentation in infected DCs and activates bacterial elimination, predominantly by inducing iNOS/NO. Induced NO synthesis strongly affects bacterial growth and infectivity. Moreover, our studies hint that Coxiella-infected DCs might be able to protect themselves from mitotoxic NO by switching from oxidative phosphorylation to glycolysis, thus ensuring survival in self-defense against C. burnetii. Our results provide new insights into DC subversion by Coxiella and the IFN-γ-mediated targeting of C. burnetii during early steps in the innate immune response.

Phenotypic effects of mutations observed in the neuraminidase of human origin H5N1 influenza A viruses

Global spread and regional endemicity of H5Nx Goose/Guangdong avian influenza viruses (AIV) pose a continuous threat for poultry production and zoonotic, potentially pre-pandemic, transmission to humans. Little is known about the role of mutations in the viral neuraminidase (NA) that accompanied bird-to-human transmission to support AIV infection of mammals. Here, after detailed analysis of the NA sequence of human H5N1 viruses, we studied the role of A46D, L204M, S319F and S430G mutations in virus fitness in vitro and in vivo. Although H5N1 AIV carrying avian- or human-like NAs had similar replication efficiency in avian cells, human-like NA enhanced virus replication in human airway epithelia. The L204M substitution consistently reduced NA activity of H5N1 and nine other influenza viruses carrying NA of groups 1 and 2, indicating a universal effect. Compared to the avian ancestor, human-like H5N1 virus has less NA incorporated in the virion, reduced levels of viral NA RNA replication and NA expression. We also demonstrate increased accumulation of NA at the plasma membrane, reduced virus release and enhanced cell-to-cell spread. Furthermore, NA mutations increased virus binding to human-type receptors. While not affecting high virulence of H5N1 in chickens, the studied NA mutations modulated virulence and replication of H5N1 AIV in mice and to a lesser extent in ferrets. Together, mutations in the NA of human H5N1 viruses play different roles in infection of mammals without affecting virulence or transmission in chickens. These results are important to understand the genetic determinants for replication of AIV in mammals and should assist in the prediction of AIV with zoonotic potential.

Comparative analysis of ChAdOx1 nCoV-19 and Ad26.COV2.S SARS-CoV-2 vector vaccines

Vector-based SARS-CoV-2 vaccines have been associated with vaccine- induced thrombosis with thrombocytopenia syndrome (VITT/TTS), but the causative factors are still unresolved. We comprehensively analyzed the ChAdOx1 nCoV-19 (AstraZeneca) and Ad26.COV2.S (Johnson & Johnson) vaccines. ChAdOx1 nCoV-19 contains significant amounts of host cell protein impurities, including functionally active proteasomes, and adenoviral proteins. A much smaller amount of impurities was found in Ad26.COV2.S. Platelet factor 4 formed complexes with ChAdOx1 nCoV-19 constituents, but not with purified virions from ChAdOx1 nCoV-19 or with Ad26.COV2.S. Vascular hyperpermeability was induced by ChAdOx nCoV-19 but not by Ad26.COV2.S. These differences in impurities together with EDTAinduced capillary leakage might contribute to the higher incidence rate of VITT associated with ChAdOx1 nCoV-19 compared to Ad26.COV2.S.

Point Mutations in the Glycoprotein Ectodomain of Field Rabies Viruses Mediate Cell Culture Adaptation through Improved Virus Release in a Host Cell Dependent and Independent Manner

Molecular details of field rabies virus (RABV) adaptation to cell culture replication are insufficiently understood. A better understanding of adaptation may not only reveal requirements for efficient RABV replication in cell lines, but may also provide novel insights into RABV biology and adaptation-related loss of virulence and pathogenicity. Using two recombinant field rabies virus clones (rRABV Dog and rRABV Fox), we performed virus passages in three different cell lines to identify cell culture adaptive mutations. Ten passages were sufficient for the acquisition of adaptive mutations in the glycoprotein G and in the C-terminus of phosphoprotein P. Apart from the insertion of a glycosylation sequon via the mutation D247N in either virus, both acquired additional and cell line-specific mutations after passages on BHK (K425N) and MDCK-II (R346S or R350G) cells. As determined by virus replication kinetics, complementation, and immunofluorescence analysis, the major bottleneck in cell culture replication was the intracellular accumulation of field virus G protein, which was overcome after the acquisition of the adaptive mutations. Our data indicate that limited release of extracellular infectious virus at the plasma membrane is a defined characteristic of highly virulent field rabies viruses and we hypothesize that the observed suboptimal release of infectious virions is due to the inverse correlation of virus release and virulence in vivo.

Development of a Modular Vaccine Platform for Multimeric Antigen Display Using an Orthobunyavirus Model

Emerging infectious diseases represent an increasing threat to human and animal health. Therefore, safe and effective vaccines that could be available within a short time frame after an outbreak are required for adequate prevention and control. Here, we developed a robust and versatile self-assembling multimeric protein scaffold particle (MPSP) vaccine platform using lumazine synthase (LS) from Aquifex aeolicus. This scaffold allowed the presentation of peptide epitopes by genetic fusion as well as the presentation of large antigens by bacterial superglue-based conjugation to the pre-assembled particle. Using the orthobunyavirus model Schmallenberg virus (SBV) we designed MPSPs presenting major immunogens of SBV and assessed their efficacy in a mouse model as well as in cattle, a target species of SBV. All prototype vaccines conferred protection from viral challenge infection and the multivalent presentation of the selected antigens on the MPSP markedly improved their immunogenicity compared to the monomeric subunits. Even a single shot vaccination protected about 80% of mice from an otherwise lethal dose of SBV. Most importantly, the MPSPs induced a virtually sterile immunity in cattle. Altogether, LS represents a promising platform for modular and rapid vaccine design.

Role of Vesicle-Associated Membrane Protein-Associated Proteins (VAP) A and VAPB in Nuclear Egress of the Alphaherpesvirus Pseudorabies Virus

The molecular mechanism affecting translocation of newly synthesized herpesvirus nucleocapsids from the nucleus into the cytoplasm is still not fully understood. The viral nuclear egress complex (NEC) mediates budding at and scission from the inner nuclear membrane, but the NEC is not sufficient for efficient fusion of the primary virion envelope with the outer nuclear membrane. Since no other viral protein was found to be essential for this process, it was suggested that a cellular machinery is recruited by viral proteins. However, knowledge on fusion mechanisms involving the nuclear membranes is rare. Recently, vesicle-associated membrane protein-associated protein B (VAPB) was shown to play a role in nuclear egress of herpes simplex virus 1 (HSV-1). To test this for the related alphaherpesvirus pseudorabies virus (PrV), we mutated genes encoding VAPB and VAPA by CRISPR/Cas9-based genome editing in our standard rabbit kidney cells (RK13), either individually or in combination. Single as well as double knockout cells were tested for virus propagation and for defects in nuclear egress. However, no deficiency in virus replication nor any effect on nuclear egress was obvious suggesting that VAPB and VAPA do not play a significant role in this process during PrV infection in RK13 cells.

Generation and characterization of monoclonal antibodies specific for the Pseudorabies Virus nuclear egress complex

During herpesvirus replication, newly synthesized nucleocapsids exit the nucleus by a vesicle-mediated transport, which requires the nuclear egress complex (NEC), composed of the conserved viral proteins designated as pUL31 and pUL34 in the alphaherpesviruses pseudorabies virus (PrV) and herpes simplex viruses. Oligomerization of the heterodimeric NEC at the inner nuclear membrane (INM) results in membrane bending and budding of virus particles into the perinuclear space. The INM-derived primary envelope then fuses with the outer nuclear membrane to release nucleocapsids into the cytoplasm. The two NEC components are necessary and sufficient for induction of vesicle budding and scission as shown after co-expression in eukaryotic cells or in synthetic membranes. However, where and when the NEC is formed, how membrane curvature is mediated and how it is regulated, remains unclear. While monospecific antisera raised against the different components of the PrV NEC aided in the characterization and intracellular localization of the individual proteins, no NEC specific tools have been described yet for any herpesvirus. To gain more insight into vesicle budding and scission, we aimed at generating NEC specific monoclonal antibodies (mAbs). To this end, mice were immunized with bacterially expressed soluble PrV NEC, which was previously used for structure determination. Besides pUL31- and pUL34-specific mAbs, we also identified mAbs, which reacted only in the presence of both proteins indicating specificity for the complex. Confocal microscopy with those NEC-specific mAbs revealed small puncta (approx. 0.064 μm²) along the nuclear rim in PrV wild type infected cells. In contrast, ca. 5-fold larger speckles (approx. 0.35 μm²) were detectable in cells infected with a PrV mutant lacking the viral protein kinase pUS3, which is known to accumulate primary enveloped virions in the PNS within large invaginations of the INM, or in cells co-expressing pUL31 and pUL34. Kinetic experiments showed that while the individual proteins were detectable already between 2-4 hours after infection, the NEC-specific mAbs produced significant staining only after 4-6 hours in accordance with timing of nuclear egress. Taken together, the data indicate that these mAbs specifically label the PrV NEC.

Comparative Pathology of Domestic Pigs and Wild Boar Infected with the Moderately Virulent African Swine Fever Virus Strain "Estonia 2014"

Endemically infected European wild boar are considered a major reservoir of African swine fever virus in Europe. While high lethality was observed in the majority of field cases, strains of moderate virulence occurred in the Baltic States. One of these, "Estonia 2014", led to a higher number of clinically healthy, antibody-positive animals in the hunting bag of North-Eastern Estonia. Experimental characterization showed high virulence in wild boar but moderate virulence in domestic pigs. Putative pathogenic differences between wild boar and domestic pigs are unresolved and comparative pathological studies are limited. We here report on a kinetic experiment in both subspecies. Three animals each were euthanized at 4, 7, and 10 days post infection (dpi). Clinical data confirmed higher virulence in wild boar although macroscopy and viral genome load in blood and tissues were comparable in both subspecies. The percentage of viral antigen positive myeloid cells tested by flow cytometry did not differ significantly in most tissues. Only immunohistochemistry revealed consistently higher viral antigen loads in wild boar tissues in particular 7 dpi, whereas domestic pigs already eliminated the virus. The moderate virulence in domestic pigs could be explained by a more effective viral clearance.

Peste Des Petits Ruminants Virus and Goatpox Virus Co-Infection in Goats

Infection of small ruminants with peste des petits ruminants virus (PPRV) and goatpox virus (GTPV) are endemic and can have devastating economic consequences in Asia and Africa. Co-infection with these viruses have recently been reported in goats and sheep in Nigeria. In this study, we evaluated samples from the lips of a red Sokoto goat, and describe co-infection of keratinocytes with PPRV and GTPV using histopathology and transmission electron microscopy. Eosinophilic cytoplasmic inclusion bodies were identified histologically, and ultrastructural analysis revealed numerous large cytoplasmic viral factories containing poxvirus particles and varying sizes of smaller cytoplasmic inclusions composed of PPRV nucleocapsids. These histopathological and ultrastructural findings show concurrent infection with the 2 viruses for the first time as well as the detection of PPRV particles in epithelial cells of the mucocutaneous junction of the lip.

Function of Torsin AAA+ ATPases in Pseudorabies Virus Nuclear Egress

Newly assembled herpesvirus nucleocapsids traverse the intact nuclear envelope by a vesicle-mediated nucleo-cytoplasmic transport for final virion maturation in the cytoplasm. For this, they bud at the inner nuclear membrane resulting in primary enveloped particles in the perinuclear space (PNS) followed by fusion of the primary envelope with the outer nuclear membrane (ONM). While the conserved viral nuclear egress complex orchestrates the first steps, effectors of fusion of the primary virion envelope with the ONM are still mostly enigmatic but might include cellular proteins like SUN2 or ESCRT-III components. Here, we analyzed the influence of the only known AAA+ ATPases located in the endoplasmic reticulum and the PNS, the Torsins (Tor), on nuclear egress of the alphaherpesvirus pseudorabies virus. For this overexpression of wild type and mutant proteins as well as CRISPR/Cas9 genome editing was applied. Neither single overexpression nor gene knockout (KO) of TorA or TorB had a significant impact. However, TorA/B double KO cells showed decreased viral titers at early time points of infection and an accumulation of primary virions in the PNS pointing to a delay in capsid release during nuclear egress.

Koi herpesvirus (KHV) and KHV disease (KHVD) - a recently updated overview

Over the last years, there has been an enormous increase in the knowledge on koi herpesvirus (KHV), koi herpesvirus disease (KHVD), pathogenesis and virus variants. Different KHV lineages have clearly been identified, possible genomic changes during replication in different cell cultures at different temperatures but also in several hosts have been identified, a persistent stage of infection has been specified and it has been shown that infection with KHV is not host specific at all, but KHVD is. Additionally, it has been shown that it is possible to combat KHVD by immunization with inactivated and attenuated live vaccines using different delivery systems but also to benefit from alternative treatments with e.g. exopolysaccharids obtained from Arthrospira platensis.

Bat influenza viruses transmit among bats but are poorly adapted to non-bat species

Major histocompatibility complex class II (MHC-II) molecules of multiple species function as cell-entry receptors for the haemagglutinin-like H18 protein of the bat H18N11 influenza A virus, enabling tropism of the viruses in a potentially broad range of vertebrates. However, the function of the neuraminidase-like N11 protein is unknown because it is dispensable for viral infection or the release of H18-pseudotyped viruses. Here, we show that infection of mammalian cells with wild-type H18N11 leads to the emergence of mutant viruses that lack the N11 ectodomain and acquired mutations in H18. An infectious clone of one such mutant virus, designated rP11, appeared to be genetically stable in mice and replicated to higher titres in mice and cell culture compared with wild-type H18N11. In ferrets, rP11 antigen and RNA were detected at low levels in various tissues, including the tonsils, whereas the wild-type virus was not. In Neotropical Jamaican fruit bats, wild-type H18N11 was found in intestinal Peyer's patches and was shed to high concentrations in rectal samples, resulting in viral transmission to naive contact bats. Notably, rP11 also replicated efficiently in bats; however, only restored full-length N11 viruses were transmissible. Our findings suggest that wild-type H18N11 replicates poorly in mice and ferrets and that N11 is a determinant for viral transmission in bats.

Henipavirus-like particles induce a CD8 T cell response in C57BL/6 mice

Nipah virus (NiV), a BSL-4 pathogen, belongs to the genus Henipavirus within the family Paramyxoviridae. To date, no effective vaccine is available. Although most of the current vaccine studies aim to induce a neutralizing antibody response, it has become evident that a promising vaccine should target both, humoral and cell-mediated immune response. Virus-like particles (VLPs) have been shown to activate both arms of the adaptive immune response. In our study, VLPs composed of the NiV surface glycoproteins G and F and the matrix protein of the closely related Hendra virus (HeV M) induced both, a neutralizing antibody response and an antigen-specific CD8 T cell response with proliferation, IFN-γ expression and Th1 cytokine secretion in C57BL/6 mice. In contrast, in BALB/c mice only a neutralizing antibody response was observed. All three viral proteins included in the VLPs were shown to harbor CD8 T cell epitopes; however, the combination of all three proteins enhanced the magnitude of the CD8 T cell response. To conclude, VLPs represent a promising vaccine candidate, as they induce humoral as well as CD8 T cell-mediated immune responses.

Investigation of suspected Newcastle disease (ND) outbreaks in Egypt uncovers a high virus velogenic ND virus burden in small-scale holdings and the presence of multiple pathogens

Highly contagious Newcastle disease (ND) is associated with devastating outbreaks with highly variable clinical signs among gallinaceous birds. In this study we aimed to verify clinical ND suspicions in poultry holdings in Egypt suffering from respiratory distress and elevated mortality, comparing two groups of ND-vaccinated poultry holdings in three governorates. Besides testing for Newcastle disease virus (NDV), samples were screened for infectious bronchitis virus (IBV) and avian influenza virus (AIV) by RT-qPCR as well as by non-directed cell-culture approach on LMH-cells. Virulent NDV was confirmed only in group A (n = 16) comprising small-scale holdings. Phylogenetic analysis of the fusion protein gene of 11 NDV-positive samples obtained from this group assigned all viruses to genotype 2.VIIb and point to four different virus populations that were circulating at the same time in one governorate, indicating independent epidemiological events. In group B, comprising large commercial broiler farms (n = 10), virulent NDV was not present, although in six farms NDV vaccine-type virus (genotype 2.II) was detected. Besides, in both groups, co-infections by IBV (n = 10), AIV H9 (n = 3) and/or avian reovirus (ARV) (n = 5) and avian astrovirus (AastVs) (n = 1) could be identified. Taken together, the study confirmed clinical ND suspicion in small scale holdings, pointing to inefficient vaccination practices in this group A. However, it also highlighted that, even in an endemic situation like ND in Egypt, in cases of suspected ND vaccine failure, clinical ND suspicion has to be verified by pathotype-specific diagnostic tests. RESEARCH HIGHLIGHTS Velogenic NDV circulates in small-scale poultry holdings in Egypt. Viral transmission occurred among neighbouring farms and over long distances. Co-infections with multiple pathogens were identified. Pathotype specific diagnostic tests are essential to verify ND suspicions.

The Dengue ED3 Dot Assay, a Novel Serological Test for the Detection of Denguevirus Type-Specific Antibodies and Its Application in a Retrospective Seroprevalence Study

There are four distinct antigenic serotypes of dengue viruses (DENV-1-4). Sequential infections with different serotypes lead to cross-reactive but also serotype-specific neutralizing antibody responses. Neutralization assays are considered as gold standard for serotype-specific antibody detection. However, for retrospective seroprevalence studies, access to large serum quantities is limited making neutralization assays well-nigh impossible. Therefore, a serological test, wasting only 10 µL serum, was developed using fusion proteins of maltose binding protein and E protein domain 3 (MBP-ED3) as antigens. Twelve MBP-ED3 antigens for DENV-1-4, three MBP-ED3 antigens for WNV, JEV, and TBEV, and MBP were dotted onto a single nitrocellulose strip. ED3 dot assay results were compared to virus neutralization and ED3 ELISA test results, showing a >90% accordance for DENV-1 and a 100% accordance for DENV-2, making the test specifically useful for DENV-1/-2 serotype-specific antibody detection. Since 2010, DENV-1 has replaced DENV-2 as the dominant serotype in Cambodia. In a retrospective cohort analysis, sera collected during the DENV-1/-2 endemic period showed a shift to DENV-2-specific antibody responses in 2012 paralleled by the decline of DENV-2 infections. Altogether, the ED3 dot assay is a serum-, time- and money-saving diagnostic tool for serotype-specific antibody detection, especially when serum samples are limited.

W protein expression by Newcastle disease virus

Differential editing of transcripts from the Newcastle disease virus (NDV) phosphoprotein gene results in mRNAs capable of encoding the phosphoprotein (P), the V protein, and the W protein which share a common N-terminus but specify different C-termini. Whereas the expression and viral incorporation of the P - and V proteins by NDV has been documented, evidence for the existence of a W protein was lacking. To analyze expression of the NDV W protein, two peptides encompassing predicted antigenic sites of the unique C-terminal W protein amino acid sequence of NDV Clone 30 were used for the generation of W-specific rabbit antisera. One of them detected plasmid-expressed W protein and identified W protein after infection by indirect immunofluorescence and Western blot analyses. W protein was absent in cells infected by a newly generated recombinant NDV lacking W protein expression. Furthermore, Western blot and mass spectrometric analyses indicated the incorporation of W protein into viral particles. Confocal microscopic analyses of infected cells revealed nuclear accumulation of W protein that could be attributed to a bipartite nuclear localization sequence (NLS) within its unique C-terminal part. Redistribution of the W protein to the cytoplasm within transfected cells confirmed functionality of the NLS after mutation of its two basic clusters. This finding was additionally corroborated in cells infected with a recombinant virus expressing the mutated W protein.

New cell lines for efficient propagation of koi herpesvirus and infectious salmon anaemia virus

The production of piscine viruses, in particular of koi herpesvirus (KHV, CyHV-3) and infectious salmon anaemia virus (ISAV), is still challenging due to the limited susceptibility of available cell lines to these viruses. A number of cell lines from different fish species were compared to standard diagnostic cell lines for KHV and ISAV regarding their capability to exhibit a cytopathic effect (CPE) and to accumulate virus. Two cell lines, so far undescribed, appeared to be useful for diagnostic purposes. Fr994, a cell line derived from ovaries of rainbow trout (Oncorhynchus mykiss), produced constantly high ISA virus (ISAV) titres and developed a pronounced CPE even at high cell passage numbers, while standard cell lines are reported to gradually loose these properties upon propagation. Another cell line isolated from the head kidney of common carp (Cyprinus carpio), KoK, showed a KHV induced CPE earlier than the standard cell line used for diagnostics. A third cell line, named Fin-4, established from the fin epithelium of rainbow trout did not promote efficient replication of tested viruses, but showed antigen sampling properties and might be useful as an in vitro model for virus uptake or phagocytosis.

Electron Microscopy Methods for Virus Diagnosis and High Resolution Analysis of Viruses

The term "virosphere" describes both the space where viruses are found and the space they influence, and can extend to their impact on the environment, highlighting the complexity of the interactions involved. Studying the biology of viruses and the etiology of virus disease is crucial to the prevention of viral disease, efficient and reliable virus diagnosis, and virus control. Electron microscopy (EM) is an essential tool in the detection and analysis of virus replication. New EM methods and ongoing technical improvements offer a broad spectrum of applications, allowing in-depth investigation of viral impact on not only the host but also the environment. Indeed, using the most up-to-date electron cryomicroscopy methods, such investigations are now close to atomic resolution. In combination with bioinformatics, the transition from 2D imaging to 3D remodeling allows structural and functional analyses that extend and augment our knowledge of the astonishing diversity in virus structure and lifestyle. In combination with confocal laser scanning microscopy, EM enables live imaging of cells and tissues with high-resolution analysis. Here, we describe the pivotal role played by EM in the study of viruses, from structural analysis to the biological relevance of the viral metagenome (virome).

Characterization of gene deletion mutants of Cyprinid herpesvirus 3 (koi herpesvirus) lacking the immunogenic envelope glycoproteins pORF25, pORF65, pORF148 and pORF149

Cyprinid herpesvirus 3 (CyHV-3) or koi herpesvirus is a global pathogen causing mass mortality in koi and common carp, against which improved vaccines are urgently needed. In this study we investigated the role of four nonessential, but immunogenic envelope glycoproteins encoded by members of the ORF25 gene family (ORF25, ORF65, ORF148 and ORF149) during CyHV-3 replication. Single deletion of ORF65 did not affect in vitro replication, and deletion of ORF148 even slightly enhanced virus growth on common carp brain (CCB) cells. Deletions of ORF25 or ORF149 led to reduced plaque sizes and virus titers, which was due to delayed entry into host cells. An ORF148/ORF149 double deletion mutant exhibited wild-type like growth indicating opposing functions of the two proteins. Electron microscopy of CCB cells infected with either mutant did not indicate any effects on virion formation and maturation in nucleus or cytoplasm, nor on release of enveloped particles. The ORF148, ORF149 and double deletion mutants were also tested in animal experiments using juvenile carp, and proved to be insufficiently attenuated for use as live virus vaccines. However, surviving fish were protected against challenge with wild-type CyHV-3, demonstrating that these antibody inducing proteins are dispensable for an efficient immune response in vivo.

Detection, infection dynamics and small RNA response against Culex Y virus in mosquito-derived cells

Many insect cell lines are persistently infected with insect-specific viruses (ISV) often unrecognized by the scientific community. Considering recent findings showing the possibility of interference between arbovirus and ISV infections, it is important to pay attention to ISV-infected cell lines. One example is the Entomobirnavirus, Culex Y virus (CYV). Here we describe the detection of CYV using a combination of small RNA sequencing, electron microscopy and PCR in mosquito cell lines Aag2, U4.4 and C7-10. We found CYV-specific small RNAs in all three cell lines. Interestingly, the magnitude of the detected viral RNA genome is variable among cell passages and leads to irregular detection via electron microscopy. Gaining insights into the presence of persistent ISV infection in commonly used mosquito cells and their interactions with the host immune system is beneficial for evaluating the outcome of co-infections with arboviruses of public health concern.

Crude extracts of recombinant baculovirus expressing rabbit hemorrhagic disease virus 2 VLPs from both insect and rabbit cells protect rabbits from rabbit hemorrhagic disease caused by RHDV2

Vaccines against viral pathogens are often composed of recombinant proteins expressed in different systems. Such proteins expressed by recombinant baculoviruses have been proven to be effective for vaccination. Especially, after codon usage optimization high amounts of recombinant viral proteins can be obtained which can assemble to virus like particles (VLPs) spontaneously. In this study we compared two different codon usages of RHDV2-VP1 to improve the expression of recombinant VP1 of RHDV2 by recombinant baculoviruses after infection of insect SF9 cells or transduction of mammalian RK13 cells in order to gain high protein yields. Also the influence on the auto-assembly of RHDV2-VP1 to VLPs was investigated. Finally, the immunogenic potential of such recombinant vaccines against RHDV2 to induce a protective immune response in rabbits against RHDV2 should be characterized. There was no influence of different codon usages on RHDV2-VP1 gene expression in the respective cell lines detected. However, in insect cell line SF9 higher rates of recombinant VP1 were measured in comparison to the transduction of mammalian cells RK13. Auto-assembly of RHDV2-VP1 to VLPs was observed in both cell systems by electron microscopy. Finally, both RHDV-VP1 VLPs derived from mammalian and insect cells were able to induce a protective humoral immune response in rabbits against RHDV2.

Electron Microscopy Methods for Virus Diagnosis and High Resolution Analysis of Viruses

The term "virosphere" describes both the space where viruses are found and the space they influence, and can extend to their impact on the environment, highlighting the complexity of the interactions involved. Studying the biology of viruses and the etiology of virus disease is crucial to the prevention of viral disease, efficient and reliable virus diagnosis, and virus control. Electron microscopy (EM) is an essential tool in the detection and analysis of virus replication. New EM methods and ongoing technical improvements offer a broad spectrum of applications, allowing in-depth investigation of viral impact on not only the host but also the environment. Indeed, using the most up-to-date electron cryomicroscopy methods, such investigations are now close to atomic resolution. In combination with bioinformatics, the transition from 2D imaging to 3D remodeling allows structural and functional analyses that extend and augment our knowledge of the astonishing diversity in virus structure and lifestyle. In combination with confocal laser scanning microscopy, EM enables live imaging of cells and tissues with high-resolution analysis. Here, we describe the pivotal role played by EM in the study of viruses, from structural analysis to the biological relevance of the viral metagenome (virome).

A novel alphaherpesvirus associated with fatal diseases in banded Penguins

A novel avian alphaherpesvirus, preliminarily designated sphenicid alphaherpesvirus 1 (SpAHV-1), has been independently isolated from juvenile Humboldt and African penguins (Spheniscus humboldti and Spheniscus demersus) kept in German zoos suffering from diphtheroid oropharyngitis/laryngotracheitis and necrotizing enteritis (collectively designated as penguin-diphtheria-like disease). High-throughput sequencing was used to determine the complete genome sequences of the first two SpAHV-1 isolates. SpAHV-1 comprises a class D genome with a length of about 164 kbp, a G+C content of 45.6 mol% and encodes 86 predicted ORFs. Taxonomic association of SpAHV-1 to the genus Mardivirus was supported by gene content clustering and phylogenetic analysis of herpesvirus core genes. The presented results imply that SpAHV-1 could be the primary causative agent of penguin-diphtheria-like fatal diseases in banded penguins. These results may serve as a basis for the development of diagnostic tools in order to investigate similar cases of penguin diphtheria in wild and captive penguins.

Pulmonary metastasectomy - A retrospective comparison of surgical outcomes after laser-assisted and conventional resection

INTRODUCTION

Indications and surgical techniques for pulmonary metastasectomy (PME) are controversially discussed issues. Laser-assisted surgery (LAS) is a recent innovation that has been advocated especially in patients with multiple pulmonary metastases (PM). However, there are hardly any studies comparing surgical outcomes after laser-assisted and conventional resection. The aim of the current study was to evaluate the value of LAS in a larger study population.

MATERIALS & METHODS

A retrospective analysis was completed on 178 consecutive patients undergoing 236 PMEs at a single center between 2010 and 2015. The main endpoint was survival. Statistical analysis was performed using the Kaplan-Meier method and survival rates were compared with the log rank test. Follow-up was done with special attention to the development of recurrent PM. Local relapse was defined as a recurrent metastasis in direct relation to the previously resected area according to CT scan comparisons.

RESULTS

LAS was performed on 256 metastases in 99 patients, non-laser-assisted surgery (NLAS) on 127 metastases in 79 patients. 5-year-survival rates were 69.3% in all patients, 65.7% after LAS and 73.6% after NLAS. There was no statistically significant survival difference after LAS or NLAS (p = 0.41). The rate of local relapse was 0.8% after LAS vs 3.1% after NLAS (p = 0.073).

CONCLUSION

Despite a larger number of negative predictors for survival in LAS patients, overall survival (OS) was similar in the compared groups. There was also a trend for a lower risk of local relapses after LAS. Therefore, LAS should be considered a promising method for PME.

Crystal Structure of the Herpesvirus Nuclear Egress Complex Provides Insights into Inner Nuclear Membrane Remodeling

Although nucleo-cytoplasmic transport is typically mediated through nuclear pore complexes, herpesvirus capsids exit the nucleus via a unique vesicular pathway. Together, the conserved herpesvirus proteins pUL31 and pUL34 form the heterodimeric nuclear egress complex (NEC), which, in turn, mediates the formation of tight-fitting membrane vesicles around capsids at the inner nuclear membrane. Here, we present the crystal structure of the pseudorabies virus NEC. The structure revealed that a zinc finger motif in pUL31 and an extensive interaction network between the two proteins stabilize the complex. Comprehensive mutational analyses, characterized both in situ and in vitro, indicated that the interaction network is not redundant but rather complementary. Fitting of the NEC crystal structure into the recently determined cryoEM-derived hexagonal lattice, formed in situ by pUL31 and pUL34, provided details on the molecular basis of NEC coat formation and inner nuclear membrane remodeling.

High level expression of the Drosophila Toll receptor ectodomain and crystallization of its complex with the morphogen Spätzle

Drosophila Toll receptors are involved in embryonic development and in the immune response of adult flies. In both processes, the Toll receptor ligand is the NGF-like cystine knot protein Spätzle. Here we present the expression of Toll receptor ectodomain in Schneider cells at high yields and demonstrate a high affinity interaction with the refolded and trypsin-processed Spätzle cystine knot domain dimer. Poorly and anisotropically diffracting crystals of the complex could be improved by deglycosylation and dehydration, paving the way for structural analyses of the Toll-Spätzle interaction.

Scintigraphic Monitoring of Catheter-Port Systems in Type I Diabetics with Continuous Insulin Therapy

OBJECTIVE

We developed a non-invasive scintigraphic procedure to control the function of percutaneous catheter-port systems for continuous insulin therapy. The aim of the study was to evaluate the scintigraphic results and to compare the absorption kinetics of intraperitoneal and umbilical catheter-ports.

MATERIAL AND METHODS

Seven patients with intraperitoneal and nine patients with umbilical catheter-port systems implanted into the partially redilated umbilical vein were investigated. All these patients had normal functioning catheter-ports. Additionally, three patients with intraperitoneal and three patients with umbilical catheter-port dysfunction confirmed either by radiography or laparoscopy were studied. After the injection of (99 m)TcO (4)(-) into the port a region-of-interest was drawn around the activity at the tip of the catheter and the half-life of tracer absorption (T(1/2)) calculated.

RESULTS

The normal intraperitoneal catheter-port group showed a T(1/2) value of 6.7 +/- 3.2 min and the normal umbilical catheter-port group a T(1/2) of 6.6 +/- 2.0 min. There was no significant difference in T(1/2) between intraperitoneal and umbilicial systems. The dysfunctional catheter-port group (T(1/2) 19.3 +/- 6.7 min) differed ( p = 0.0005) from the normal catheter-port group (T(1/2) 6.7 +/- 3.2 min). On the basis of the normal group an upper threshold value of T(1/2) was calculated to be 11.8 min.

CONCLUSIONS

Imaging with (99 m)TcO (4)(-) is an accurate, non-invasive, and quick method to assess the function of insulin catheter-ports. A T(1/2) value > 11.8 min is indicative of a catheter dysfunction. Umbilical and intraperitoneal catheter-ports show similar absorption rates of (99 m)TcO (4)(-).