West Nile and Usutu viruses are efficiently inactivated in platelet concentrates by UVC light using the THERAFLEX UV-Platelets system

BACKGROUND AND OBJECTIVES

West Nile virus (WNV) and Usutu virus (USUV) are mosquito-borne flaviviruses (Flaviviridae) that originated in Africa, have expanded their geographical range during the last decades and caused documented infections in Europe in the last years. Acute WNV and USUV infections have been detected in asymptomatic blood donors by nucleic acid testing. Thus, inactivation of both viral pathogens before blood transfusion is necessary to ensure blood product safety. This study aimed to investigate the efficacy of the THERAFLEX UV-Platelets system to inactivate WNV and USUV in platelet concentrates (PCs).

MATERIALS AND METHODS

Plasma-reduced PCs were spiked with the virus suspension. Spiked PC samples were taken after spiking (load and hold sample) and after UVC illumination on the Macotronic UV illumination machine with different light doses (0.05, 0.1, 0.15 and 0.2 (standard) J/cm2). Virus loads of WNV and USUV before and after illumination were measured by titration.

RESULTS

Infectivity assays showed that UVC illumination inactivated WNV and USUV in a dose-dependent manner. At a UVC dose of 0.2 J/cm2, the WNV titre was reduced by a log10 factor of 3.59 ± 0.43 for NY99 (lineage 1) and 4.40 ± 0.29 for strain ED-I-33/18 (lineage 2). USUV titres were reduced at the same UVC dose by a log10 factor of 5.20 ± 0.70.

CONCLUSIONS

Our results demonstrate that the THERAFLEX UV-Platelets procedure is an effective technology to inactivate WNV and USUV in contaminated PCs.

Secreted NS1 proteins of tick-borne encephalitis virus and West Nile virus block dendritic cell activation and effector functions

The flavivirus non-structural protein 1 (NS1) is secreted from infected cells into the circulation and the serum levels correlate with disease severity. The effect of secreted NS1 (sNS1) on non-infected mammalian immune cells is largely unknown. Here, we expressed recombinant sNS1 proteins of tick-borne encephalitis virus (TBEV) and West Nile virus (WNV) and investigated their effects on dendritic cell (DC) effector functions. Murine bone marrow-derived DCs (BMDCs) showed reduced surface expression of co-stimulatory molecules and decreased release of pro-inflammatory cytokines when treated with sNS1 of TBEV or WNV prior to poly(I:C) stimulation. Transcriptional profiles of BMDCs that were sNS1-exposed prior to poly(I:C) stimulation showed two gene clusters that were downregulated by TBEV or WNV sNS1 and that were associated with innate and adaptive immune responses. Functionally, both sNS1 proteins modulated the capacity for BMDCs to induce specific T-cell responses as indicated by reduced IFN-γ levels in both CD4+ and CD8+ T cells after BMDC co-cultivation. In human monocyte-derived DCs, poly(I:C)-induced upregulation of co-stimulatory molecules and cytokine responses were even more strongly impaired by TBEV sNS1 or WNV sNS1 pretreatment than in the murine system. Our findings indicate that exogenous flaviviral sNS1 proteins interfere with DC-mediated stimulation of T cells, which is crucial for the initiation of cell-mediated adaptive immune responses in human flavivirus infections. Collectively, our data determine soluble flaviviral NS1 as a virulence factor responsible for a dampened immune response to flavivirus infections. IMPORTANCE The effective initiation of protective host immune responses controls the outcome of infection, and dysfunctional T-cell responses have previously been associated with symptomatic human flavivirus infections. We demonstrate that secreted flavivirus NS1 proteins modulate innate immune responses of uninfected bystander cells. In particular, sNS1 markedly reduced the capacity of dendritic cells to stimulate T-cell responses upon activation. Hence, by modulating cellular host responses that are required for effective antigen presentation and initiation of adaptive immunity, sNS1 proteins may contribute to severe outcomes of flavivirus disease.

Preclinical immunogenicity and protective efficacy of a SARS-CoV-2 RBD-based vaccine produced with the thermophilic filamentous fungal expression system Thermothelomyces heterothallica C1

Introduction

The emergency use of vaccines has been the most efficient way to control the coronavirus disease 19 (COVID-19) pandemic. However, the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern has reduced the efficacy of currently used vaccines. The receptor-binding domain (RBD) of the SARS-CoV-2 spike (S) protein is the main target for virus neutralizing (VN) antibodies.

Methods

A SARS-CoV-2 RBD vaccine candidate was produced in the Thermothelomyces heterothallica (formerly, Myceliophthora thermophila) C1 protein expression system and coupled to a nanoparticle. Immunogenicity and efficacy of this vaccine candidate was tested using the Syrian golden hamster (Mesocricetus auratus) infection model.

Results

One dose of 10-μg RBD vaccine based on SARS-CoV-2 Wuhan strain, coupled to a nanoparticle in combination with aluminum hydroxide as adjuvant, efficiently induced VN antibodies and reduced viral load and lung damage upon SARS-CoV-2 challenge infection. The VN antibodies neutralized SARS-CoV-2 variants of concern: D614G, Alpha, Beta, Gamma, and Delta.

Discussion

Our results support the use of the Thermothelomyces heterothallica C1 protein expression system to produce recombinant vaccines against SARS-CoV-2 and other virus infections to help overcome limitations associated with the use of mammalian expression system.

Cross-reactive antibodies against Langat virus protect mice from lethal tick-borne encephalitis virus infection

Introduction

Naturally attenuated Langat virus (LGTV) and highly pathogenic tick-borne encephalitis virus (TBEV) share antigenically similar viral proteins and are grouped together in the same flavivirus serocomplex. In the early 1970s, this has encouraged the usage of LGTV as a potential live attenuated vaccine against tick-borne encephalitis (TBE) until cases of encephalitis were reported among vaccinees. Previously, we have shown in a mouse model that immunity induced against LGTV protects mice against lethal TBEV challenge infection. However, the immune correlates of this protection have not been studied.

Methods

We used the strategy of adoptive transfer of either serum or T cells from LGTV infected mice into naïve recipient mice and challenged them with lethal dose of TBEV.

Results

We show that mouse infection with LGTV induced both cross-reactive antibodies and T cells against TBEV. To identify correlates of protection, Monitoring the disease progression in these mice for 16 days post infection, showed that serum from LGTV infected mice efficiently protected from developing severe disease. On the other hand, adoptive transfer of T cells from LGTV infected mice failed to provide protection. Histopathological investigation of infected brains suggested a possible role of microglia and T cells in inflammatory processes within the brain.

Discussion

Our data provide key information regarding the immune correlates of protection induced by LGTV infection of mice which may help design better vaccines against TBEV.

Detection and Characterization of Alongshan Virus in Ticks and Tick Saliva from Lower Saxony, Germany with Serological Evidence for Viral Transmission to Game and Domestic Animals

The newly discovered group of Jingmenviruses has been shown to infect a wide range of hosts and has been associated with febrile illness in humans. During a survey for Jingmenviruses in ticks from Lower Saxony, Germany, Alongshan virus (ALSV) was identified in Ixodes spp. ticks. Additional virus screenings revealed the presence of ALSV in the bodies and saliva of ticks collected at several locations in Lower Saxony. Vector competence studies that included Ixodes ricinus and Dermacentor reticulatus validated the replication of ALSV within those tick species. In vitro feeding experiments with ALSV-injected Ixodes ricinus demonstrated effective viral transmission during blood feeding. To evaluate the potential viral transmission during a natural blood meal, sera from wild game and domestic animals were investigated. One serum sample from a red deer was found to be positive for ALSV RNA, while serological screenings in game and domestic animals revealed the presence of ALSV-specific antibodies at different locations in Lower Saxony. Overall, those results demonstrate the broad distribution of ALSV in ticks in Lower Saxony and hypothesize frequent exposure to animals based on serological investigations. Hence, its potential risk to human and animal health requires further investigation.

Co-exposure to Anaplasma spp., Coxiella burnetii and tick-borne encephalitis virus in sheep in southern Germany

The intracellular bacteria Anaplasma spp. and Coxiella burnetii and the tick-borne encephalitis virus (TBEV) are tick-transmitted pathogens circulating in the southern German sheep population. Knowledge of interaction among Anaplasma spp., C. burnetii and TBEV in sheep is lacking, but together they might promote and reinforce disease progression. The current study aimed to identify co-exposure of sheep to Anaplasma spp., C. burnetii and TBEV. For this purpose, 1,406 serum samples from 36 sheep flocks located in both southern German federal states, Baden-Wuerttemberg and Bavaria, were analysed by ELISAs to determine the antibody levels of the three pathogens. Inconclusive and positive results from the TBEV ELISA were additionally confirmed by a serum neutralisation assay. The proportion of sheep with antibodies against Anaplasma spp. (47.2%), C. burnetii (3.7%) and TBEV (4.7%) differed significantly. Significantly more flocks with Anaplasma spp. seropositive sheep (91.7%) were detected than flocks with antibodies against TBEV (58.3%) and C. burnetii (41.7%), but there was no significant difference between the number of flocks which contained TBEV and C. burnetii seropositive sheep. Seropositivity against at least two pathogens was detected in 4.7% of sheep from 20 flocks. Most co-exposed sheep had antibodies against Anaplasma spp./TBEV (n = 36), followed by Anaplasma spp./C. burnetii (n = 27) and Anaplasma spp./C. burnetii/TBEV (n = 2). Only one sheep showed an immune response against C. burnetii and TBEV. Flocks with sheep being positive against more than one pathogen were widely distributed throughout southern Germany. The descriptive analysis revealed no association between the antibody response of the three pathogens at animal level. Taking the flocks as a cluster variable into account, the exposure to TBEV reduced the probability of identifying C. burnetii antibodies in sheep significantly (odds ratio 0.46; 95% confidence interval 0.24-0.85), but the reason for this is unknown. The presence of Anaplasma spp. antibodies did not influence the detection of antibodies against C. burnetii and TBEV. Studies under controlled conditions are necessary to evaluate any possible adverse impact of co-exposure to tick-borne pathogens on sheep health. This can help to clarify rare disease patterns. Research in this field may also support the One Health approach due to the zoonotic potential of Anaplasma spp., C. burnetii and TBEV.

Antibody ratios against NS1 antigens of tick-borne encephalitis and West Nile viruses support differential flavivirus serology in dogs

Flavivirus diagnostics are complicated by substantial cross-reactivity of antibodies between different flavivirus species. This is of particular importance in regions with multiple endemic flaviviruses in co-circulation. Tick-borne encephalitis virus (TBEV) is the causative agent of tick-borne encephalitis, the most common infection of the central nervous system in endemic regions of Europe and Asia. Since 2018, the related West Nile virus (WNV) has spread to Germany where its geographic distribution overlaps with TBEV endemic regions. Besides humans, various animal species are susceptible to TBEV and WNV infection. To compare antibody responses against these flaviviruses and test for cross-reactivity, we developed a multi-species luciferase immunoprecipitation system antibody detection assay for several different antigens. We performed a serosurvey of 682 dogs from five different European countries to detect antibodies against TBEV and WNV. Twelve specimens were positive for TBEV NS1 only and seven for WNV NS1 only. Two specimens were reactive to both NS1 antigens and another two were equivocal for WNV NS1. Interestingly, 89.5% of positive specimens had TBEV/WNV or WNV/TBEV signal ratios of 10 to >300 between individual NS1 antigens, allowing for a clear distinction between the two viruses. The remaining 10.5% of reactive specimens showed a five- to 10-fold difference between the two viruses and included possible dual exposures to both viruses. In contrast, equivocal samples showed low signal ratios between the NS1 antigens, suggesting unspecific reactivity. Based on these data, we found the NS1 protein to be a suitable antigen to distinguish between TBEV- and WNV-specific antibodies in dogs with sensitivity and specificity similar to virus neutralization tests.

Network meta-analysis of transcriptome expression changes in different manifestations of dengue virus infection

Background

Several studies have been performed to study transcriptome profiles after dengue virus infections with partly different results. Due to slightly different settings of the individual studies, different genes and enriched gene sets are reported in these studies. The main aim of this network meta-analysis was to aggregate a selection of these studies to identify genes and gene sets that are more generally associated with dengue virus infection, i.e. with less dependence on the individual study settings.

Methods

We performed network meta-analysis by different approaches using publicly available gene expression data of five selected studies from the Gene Expression Omnibus database. The study network includes dengue fever (DF), hemorrhagic fever (DHF), shock syndrome (DSS) patients as well as convalescent and healthy control individuals. After data merging and missing value imputation, study-specific batch effects were removed. Pairwise differential expression analysis and subsequent gene-set enrichment analysis were performed between the five study groups. Furthermore, mutual information networks were derived from the top genes of each group comparison, and the separability between the three patient groups was studied by machine learning models.

Results

From the 10 possible pairwise group comparisons in the study network, six genes (IFI27, TPX2, CDT1, DTL, KCTD14 and CDCA3) occur with a noticeable frequency among the top listed genes of each comparison. Thus, there is an increased evidence that these genes play a general role in dengue virus infections. IFI27 and TPX2 have also been highlighted in the context of dengue virus infection by other studies. A few of the identified gene sets from the network meta-analysis overlap with findings from the original studies. Mutual information networks yield additional genes for which the observed pairwise correlation is different between the patient groups. Machine learning analysis shows a moderate separability of samples from the DF, DHF and DSS groups (accuracy about 80%).

Conclusions

Due to an increased sample size, the network meta-analysis could reveal additional genes which are called differentially expressed between the studied groups and that may help to better understand the molecular basis of this disease.

Analysis of avian Usutu virus infections in Germany from 2011 to 2018 with focus on dsRNA detection to demonstrate viral infections

Usutu virus (USUV) is a zoonotic arbovirus causing avian mass mortalities. The first outbreak in North-Western Germany occurred in 2018. This retrospective analysis focused on combining virological and pathological findings in birds and immunohistochemistry. 25 common blackbirds, one great grey owl, and one kingfisher collected from 2011 to 2018 and positive for USUV by qRT-PCR were investigated. Macroscopically, most USUV infected birds showed splenomegaly and hepatomegaly. Histopathological lesions included necrosis and lymphohistiocytic inflammation within spleen, Bursa fabricii, liver, heart, brain, lung and intestine. Immunohistochemistry revealed USUV antigen positive cells in heart, spleen, pancreas, lung, brain, proventriculus/gizzard, Bursa fabricii, kidney, intestine, skeletal muscle, and liver. Analysis of viral genome allocated the virus to Europe 3 or Africa 2 lineage. This study investigated whether immunohistochemical detection of double-stranded ribonucleic acid (dsRNA) serves as an alternative tool to detect viral intermediates. Tissue samples of six animals with confirmed USUV infection by qRT-PCR but lacking viral antigen in liver and spleen, were further examined immunohistochemically. Two animals exhibited a positive signal for dsRNA. This could indicate either an early state of infection without sufficient formation of virus translation products, occurrence of another concurrent virus infection or endogenous dsRNA not related to infectious pathogens and should be investigated in more detail in future studies.

Toll-like Receptors in Viral Encephalitis

Viral encephalitis is a rare but serious syndrome. In addition to DNA-encoded herpes viruses, such as herpes simplex virus and varicella zoster virus, RNA-encoded viruses from the families of Flaviviridae, Rhabdoviridae and Paramyxoviridae are important neurotropic viruses. Whereas in the periphery, the role of Toll-like receptors (TLR) during immune stimulation is well understood, TLR functions within the CNS are less clear. On one hand, TLRs can affect the physiology of neurons during neuronal progenitor cell differentiation and neurite outgrowth, whereas under conditions of infection, the complex interplay between TLR stimulated neurons, astrocytes and microglia is just on the verge of being understood. In this review, we summarize the current knowledge about which TLRs are expressed by cell subsets of the CNS. Furthermore, we specifically highlight functional implications of TLR stimulation in neurons, astrocytes and microglia. After briefly illuminating some examples of viral evasion strategies from TLR signaling, we report on the current knowledge of primary immunodeficiencies in TLR signaling and their consequences for viral encephalitis. Finally, we provide an outlook with examples of TLR agonist mediated intervention strategies and potentiation of vaccine responses against neurotropic virus infections.

Sequential MAVS and MyD88/TRIF signaling triggers anti-viral responses of tick-borne encephalitis virus-infected murine astrocytes

Tick-borne encephalitis virus (TBEV), a member of the Flaviviridae family, is typically transmitted upon tick bite and can cause meningitis and encephalitis in humans. In TBEV-infected mice, mitochondrial antiviral-signaling protein (MAVS), the downstream adaptor of retinoic acid-inducible gene-I (RIG-I)-like receptor (RLR) signaling, is needed to induce early type I interferon (IFN) responses and to confer protection. To characterize the brain-resident cell subset that produces protective IFN-β in TBEV-infected mice, we isolated neurons, astrocytes, and microglia from mice and exposed these cell types to TBEV in vitro. Under such conditions, neurons showed the highest percentage of infected cells, whereas astrocytes and microglia were infected to a lesser extent. In the supernatant (SN) of infected neurons, IFN-β was not detectable, while infected astrocytes showed high and microglia low IFN-β expression. Transcriptome analyses of astrocytes implied that MAVS signaling was needed early after TBEV infection. Accordingly, MAVS-deficient astrocytes showed enhanced TBEV infection and significantly reduced early IFN-β responses. Nevertheless, at later time points, moderate amounts of IFN-β were detected in the SN of infected MAVS-deficient astrocytes. Transcriptome analyses indicated that MAVS deficiency negatively affected the induction of early anti-viral responses, which resulted in significantly increased TBEV replication. Treatment with MyD88 and TRIF inhibiting peptides reduced only late IFN-β responses of TBEV-infected WT astrocytes and blocked entirely IFN-β responses of infected MAVS-deficient astrocytes. Thus, upon TBEV exposure of brain-resident cells, astrocytes are important IFN-β producers showing biphasic IFN-β induction that initially depends on MAVS and later on MyD88/TRIF signaling.

Increasing awareness for tick-borne encephalitis virus using small ruminants as suitable sentinels: Preliminary observations

Tick-borne encephalitis virus (TBEV) is one of the most common zoonotic vector-borne infections in Europe. An appropriate awareness is crucial to react quickly and efficiently to protect humans from this pathogen. From winter 2017 until spring 2018 serum samples were collected from 71 small ruminant flocks (3174 animals) in five German federal states. The sera were examined for TBEV antibodies by ELISA and serum neutralization test. In the TBEV risk areas, there was a coincidence in 14 districts between seropositive small ruminants and the occurrence of human TBE cases in 2017. In eight districts, the TBEV infection could not be detected in small ruminants although human cases were reported. In contrast, in five districts, small ruminants tested TBEV seropositive without notified human TBE cases in 2017. A changing pattern of TBEV circulation in the environment was observed by the absence of antibodies in a defined high-risk area. In the non-TBE risk areas, seropositive small ruminants were found in five districts. In two districts with a low human incidence the infection was missed by the small ruminant sentinels. An intra-herd prevalence of 12.5% was determined in a goat flock in the non-TBE risk area in 2017, two years prior the first autochthone human case was reported. All sheep and goats in this flock were examined for TBEV antibodies for three years. Individual follow-up of twelve small ruminants was possible and revealed mostly a short lifespan of TBEV antibodies of less than one year. The probability to identify TBEV seropositive sheep flocks was enhanced in flocks kept for landscape conservation or which were shepherded (p < 0.05). Our preliminary observations clearly demonstrated the successful utilization of small ruminants as sentinel animals for TBEV.

Susceptibility of Tick-Borne Encephalitis Virus to Inactivation by Heat, Acidic pH, Chemical, or UV Treatment

Tick-borne encephalitis virus (TBEV) is a single-stranded, positive-sense RNA virus in the family Flaviviridae that is endemic in parts of Europe and Asia and can cause meningitis or encephalitis. Due to the disease severity, TBEV requires handling under heightened biosafety measures. The establishment and validation of inactivation procedures is a prerequisite for downstream analyses and management of occupational exposure. Therefore, different procedures for TBEV inactivation were tested. Our results suggest that TBEV is susceptible to inactivation by heat, acidic pH, different concentrations of alcohol, formaldehyde, or detergents, and exposure to UV irradiation, which may depend on sample size and composition.

Seroreactivity against Marburg or related filoviruses in West and Central Africa

A serological survey of 2,430 archived serum samples collected between 1997 and 2012 was conducted to retrospectively determine the prevalence of Marburg virus in five African countries. Serum samples were screened for neutralizing antibodies in a pseudotype micro-neutralization assay and confirmed by enzyme-linked immunosorbent assay (ELISA). Surprisingly, a seroprevalence for Marburg virus of 7.5 and 6.3% was found in Cameroon and Ghana, respectively, suggesting the circulation of filoviruses or related viruses outside of known endemic areas that remain undetected by current surveillance efforts. However, due to the lack of validated assays and appropriate positive controls, these results must be considered preliminary.

Serologic Prevalence of Ebola Virus in Equatorial Africa

We conducted a serologic survey of 2,430 serum samples collected during 1997-2012 for various studies to determine the prevalence of the hemorrhagic fever virus Ebola virus (EBOV) in equatorial Africa. We screened serum samples for neutralizing antibodies by using a pseudotype microneutralization assay and a newly developed luciferase immunoprecipitation system assay. Specimens seroreactive for EBOV were confirmed by using an ELISA. Our results suggest a serologic prevalence of 2%-3.5% in the Republic of the Congo and the Democratic Republic of the Congo, which have reported outbreaks of infection with EBOV. In addition we detected a seroprevalence of 1.3% in southern Cameroon, which indicated a low risk for exposure in this region.

Ebola Virus Neutralizing Antibodies Detectable in Survivors of theYambuku, Zaire Outbreak 40 Years after Infection

The first reported outbreak of Ebola virus disease occurred in 1976 in Yambuku, Democratic Republic of Congo. Antibody responses in survivors 11 years after infection have been documented. However, this report is the first characterization of anti-Ebola virus antibody persistence and neutralization capacity 40 years after infection. Using ELISAs we measured survivor’s immunological response to Ebola virus Zaire (EBOV) glycoprotein and nucleoprotein, and assessed VP40 reactivity. Neutralization of EBOV was measured using a pseudovirus approach and plaque reduction neutralization test with live EBOV. Some survivors from the original EBOV outbreak still harbor antibodies against all 3 measures. Interestingly, a subset of these survivors’ serum antibodies could still neutralize live virus 40 years postinitial infection. These data provide the longest documentation of both anti-Ebola serological response and neutralization capacity within any survivor cohort, extending the known duration of response from 11 years postinfection to at least 40 years after symptomatic infection.

Serologic Markers for Ebolavirus Among Healthcare Workers in the Democratic Republic of the Congo

Healthcare settings have played a major role in propagation of Ebola virus (EBOV) outbreaks. Healthcare workers (HCWs) have elevated risk of contact with EBOV-infected patients, particularly if safety precautions are not rigorously practiced. We conducted a serosurvey to determine seroprevalence against multiple EBOV antigens among HCWs of Boende Health Zone, Democratic Republic of the Congo, the site of a 2014 EBOV outbreak. Interviews and specimens were collected from 565 consenting HCWs. Overall, 234 (41.4%) of enrolled HCWs were reactive to at least 1 EBOV protein: 159 (28.1%) were seroreactive for anti-glycoprotein immunoglobulin G (IgG), 89 (15.8%) were seroreactive for anti-nucleoprotein IgG, and 54 (9.5%) were VP40 positive. Additionally, sera from 16 (2.8%) HCWs demonstrated neutralization capacity. These data demonstrate that a significant proportion of HCWs have the ability to neutralize virus, despite never having developed Ebola virus disease symptoms, highlighting an important and poorly documented aspect of EBOV infection and progression.

Pan-Filovirus Serum Neutralizing Antibodies in a Subset of Congolese Ebolavirus Infection Survivors

One year after a Zaire ebolavirus (EBOV) outbreak occurred in the Boende Health Zone of the Democratic Republic of the Congo during 2014, we sought to determine the breadth of immune response against diverse filoviruses including EBOV, Bundibugyo (BDBV), Sudan (SUDV), and Marburg (MARV) viruses. After assessing the 15 survivors, 5 individuals demonstrated some degree of reactivity to multiple ebolavirus species and, in some instances, Marburg virus. All 5 of these survivors had immunoreactivity to EBOV glycoprotein (GP) and EBOV VP40, and 4 had reactivity to EBOV nucleoprotein (NP). Three of these survivors showed serologic responses to the 3 species of ebolavirus GPs tested (EBOV, BDBV, SUDV). All 5 samples also exhibited ability to neutralize EBOV using live virus, in a plaque reduction neutralization test. Remarkably, 3 of these EBOV survivors had plasma antibody responses to MARV GP. In pseudovirus neutralization assays, serum antibodies from a subset of these survivors also neutralized EBOV, BDBV, SUDV, and Taï Forest virus as well as MARV. Collectively, these findings suggest that some survivors of naturally acquired ebolavirus infection mount not only a pan-ebolavirus response, but also in less frequent cases, a pan-filovirus neutralizing response.

Incidental detection of breast cancer by 68Ga-DOTATOC-PET/CT in women suffering from neuroendocrine tumours

Aim: Somatostatin receptor (sstr) imaging using 68Ga- DOTATOC-PET/CT in neuroendocrine tumors (NET) is promising, suggesting a more sensitive detection of lesions with a low sstr-expression. This is also important for other sstr positive tumors, especially breast cancer whose incidence and age-range is similar to that of NET. Patients, methods: The PET/CT data of 33 consecutive women with NET (age: 33–78 years, mean 59) who underwent whole-body staging with 68Ga-DOTATOC was retrospectively analyzed for breast lesions. The data was read separately, side-byside and as fused images. Focal tracer uptake in the breast was semiquantitatively analyzed by comparing the lesional SUVmax to normal breast tissue using Wilcoxon's rank sum test. Breast cancer lesions were compared visually to concomitant NET- lesions. Results: In six of 33 patients (18%) breast lesions were observed on the CT-scans and classified in four patients (12%) as suspicious. The same lesions also showed a pathological tracer uptake on the corresponding PET-scan, visually and semiquantitatively (p<0.01). Histological reevaluation of the suspicious lesions revealed two patients with NET metastases. Two patients had primary breast cancer with lower tracer uptake than concomitant abdominal NET-lesions. Breast cancer diagnosis resulted in a change of the therapeutic regimen. Conclusion: 68Ga- DOTATOC-PET/CT not only improves the staging of NET-patients, but also increases the chance to detect sstr-positive breast cancer. Although these lesions may show a lower tracer uptake than NET, they must not be overlooked or misinterpreted as metastases. Further imaging and clarification by histopathology is warranted, as the confirmation of a secondary malignoma has great impact on further therapeutic proceedings.

Pseudotyping Viral Vectors With Emerging Virus Envelope Proteins

Previously unidentified viruses, such as Middle East respiratory syndrome coronavirus, continue to emerge and threaten populations, while powerful new techniques have identified many new human and animal viruses. Similarly, existing viruses, from Ebola virus to chikungunya virus, are reemerging and spreading to new geographical regions. These viruses often pose a challenge for researchers to study due to their highly pathogenic nature. Lentiviral and rhabdoviral pseudotypes are excellent tools for studying enveloped viruses and have contributed to many recent advances in areas such as receptor usage, viral entry and serology. In particular, pseudotypes allow the safe study of unknown or highly pathogenic viruses. They also allow the initial characterization of aspects of infection such as cellular tropism for difficult to culture viruses. In this review we will introduce various pseudotyping systems for emerging viruses, including chikungunya virus, Ebola virus, SARS and MERS coronaviruses and Nipah virus, as well as their use in diverse studies including drug screening and antibody neutralization. We will also discuss the limitations and potential caveats using pseudotypes.

Activity-based cost analysis of hepatic tumor ablation using CT-guided high-dose rate brachytherapy or CT-guided radiofrequency ablation in hepatocellular carcinoma

Purpose

To analyse and compare the costs of hepatic tumor ablation with computed tomography (CT)-guided high-dose rate brachytherapy (CT-HDRBT) and CT-guided radiofrequency ablation (CT-RFA) as two alternative minimally invasive treatment options of hepatocellular carcinoma (HCC).

Materials and methods

An activity based process model was created determining working steps and required staff of CT-RFA and CT-HDRBT. Prorated costs of equipment use (purchase, depreciation, and maintenance), costs of staff, and expenditure for disposables were identified in a sample of 20 patients (10 treated by CT-RFA and 10 by CT-HDRBT) and compared. A sensitivity and break even analysis was performed to analyse the dependence of costs on the number of patients treated annually with both methods.

Results

Costs of CT-RFA were nearly stable with mean overall costs of approximately 1909 €, 1847 €, 1816 € and 1801 € per patient when treating 25, 50, 100 or 200 patients annually, as the main factor influencing the costs of this procedure was the single-use RFA probe. Mean costs of CT-HDRBT decreased significantly per patient ablation with a rising number of patients treated annually, with prorated costs of 3442 €, 1962 €, 1222 € and 852 € when treating 25, 50, 100 or 200 patients, due to low costs of single-use disposables compared to high annual fix-costs which proportionally decreased per patient with a higher number of patients treated annually. A break-even between both methods was reached when treating at least 55 patients annually.

Conclusion

Although CT-HDRBT is a more complex procedure with more staff involved, it can be performed at lower costs per patient from the perspective of the medical provider when treating more than 55 patients compared to CT-RFA, mainly due to lower costs for disposables and a decreasing percentage of fixed costs with an increasing number of treatments.

Ventilation/perfusion SPECT/CT in patients with pulmonary emphysema. Evaluation of software-based analysing

The purpose of this study was to evaluate the reproducibility of a new software based analysing system for ventilation/perfusion single-photon emission computed tomography/computed tomography (V/P SPECT/CT) in patients with pulmonary emphysema and to compare it to the visual interpretation.

PATIENTS, MATERIAL AND METHODS

19 patients (mean age: 68.1 years) with pulmonary emphysema who underwent V/P SPECT/CT were included. Data were analysed by two independent observers in visual interpretation (VI) and by software based analysis system (SBAS). SBAS PMOD version 3.4 (Technologies Ltd, Zurich, Switzerland) was used to assess counts and volume per lung lobe/per lung and to calculate the count density per lung, lobe ratio of counts and ratio of count density. VI was performed using a visual scale to assess the mean counts per lung lobe. Interobserver variability and association for SBAS and VI were analysed using Spearman's rho correlation coefficient.

RESULTS

Interobserver agreement correlated highly in perfusion (rho: 0.982, 0.957, 0.90, 0.979) and ventilation (rho: 0.972, 0.924, 0.941, 0.936) for count/count density per lobe and ratio of counts/count density in SBAS. Interobserver agreement correlated clearly for perfusion (rho: 0.655) and weakly for ventilation (rho: 0.458) in VI.

CONCLUSIONS

SBAS provides more reproducible measures than VI for the relative tracer uptake in V/P SPECT/CTs in patients with pulmonary emphysema. However, SBAS has to be improved for routine clinical use.

A novel rhabdovirus associated with acute hemorrhagic fever in central Africa

Deep sequencing was used to discover a novel rhabdovirus (Bas-Congo virus, or BASV) associated with a 2009 outbreak of 3 human cases of acute hemorrhagic fever in Mangala village, Democratic Republic of Congo (DRC), Africa. The cases, presenting over a 3-week period, were characterized by abrupt disease onset, high fever, mucosal hemorrhage, and, in two patients, death within 3 days. BASV was detected in an acute serum sample from the lone survivor at a concentration of 1.09×10⁶ RNA copies/mL, and 98.2% of the genome was subsequently de novo assembled from ∼140 million sequence reads. Phylogenetic analysis revealed that BASV is highly divergent and shares less than 34% amino acid identity with any other rhabdovirus. High convalescent neutralizing antibody titers of >1∶1000 were detected in the survivor and an asymptomatic nurse directly caring for him, both of whom were health care workers, suggesting the potential for human-to-human transmission of BASV. The natural animal reservoir host or arthropod vector and precise mode of transmission for the virus remain unclear. BASV is an emerging human pathogen associated with acute hemorrhagic fever in Africa.

We used deep sequencing, a method for generating millions of DNA sequence reads from clinical samples, to discover a novel rhabdovirus (Bas-Congo virus, or BASV) associated with a 2009 outbreak of 3 human cases of acute hemorrhagic fever in Mangala village, Democratic Republic of Congo (DRC), Africa. The cases, presenting over a 3-week period, were characterized by abrupt disease onset, high fever, bloody vomiting and diarrhea, and, in two patients, death within 3 days. BASV was present in the blood of the lone survivor at a concentration of over a million copies per milliliter. The genome of BASV, assembled from over 140 million sequence reads, reveals that it is very different from any other rhabdovirus. The lone survivor and a nurse caring for him (with no symptoms), both health care workers, were found to have high levels of antibodies to BASV, indicating that they both had been infected by the virus. Although the source of the virus remains unclear, our study findings suggest that BASV may be spread by human-to-human contact and is an emerging pathogen associated with acute hemorrhagic fever in Africa.

In-depth investigation of archival and prospectively collected samples reveals no evidence for XMRV infection in prostate cancer

XMRV, or xenotropic murine leukemia virus (MLV)-related virus, is a novel gammaretrovirus originally identified in studies that analyzed tissue from prostate cancer patients in 2006 and blood from patients with chronic fatigue syndrome (CFS) in 2009. However, a large number of subsequent studies failed to confirm a link between XMRV infection and CFS or prostate cancer. On the contrary, recent evidence indicates that XMRV is a contaminant originating from the recombination of two mouse endogenous retroviruses during passaging of a prostate tumor xenograft (CWR22) in mice, generating laboratory-derived cell lines that are XMRV-infected. To confirm or refute an association between XMRV and prostate cancer, we analyzed prostate cancer tissues and plasma from a prospectively collected cohort of 39 patients as well as archival RNA and prostate tissue from the original 2006 study. Despite comprehensive microarray, PCR, FISH, and serological testing, XMRV was not detected in any of the newly collected samples or in archival tissue, although archival RNA remained XMRV-positive. Notably, archival VP62 prostate tissue, from which the prototype XMRV strain was derived, tested negative for XMRV on re-analysis. Analysis of viral genomic and human mitochondrial sequences revealed that all previously characterized XMRV strains are identical and that the archival RNA had been contaminated by an XMRV-infected laboratory cell line. These findings reveal no association between XMRV and prostate cancer, and underscore the conclusion that XMRV is not a naturally acquired human infection.

Development and application of a high-throughput microneutralization assay: lack of xenotropic murine leukemia virus-related virus and/or murine leukemia virus detection in blood donors

BACKGROUND

Xenotropic murine leukemia virus (MLV)-related virus (XMRV) and other related MLVs have been described with chronic fatigue syndrome and certain types of prostate cancer. In addition, prevalence rates as high as 7% have been reported in blood donors, raising the risk of transfusion-related transmission. Several laboratories have utilized microneutralization assays as a surrogate marker for detection of anti-MLV serologic responses--with up to 25% of prostate cancer patients reported to harbor neutralizing antibody responses.

STUDY DESIGN AND METHODS

We developed a high-throughput microneutralization assay for research studies on blood donors using retroviral vectors pseudotyped with XMRV-specific envelopes. Infection with these pseudotypes was neutralized by sera from both macaques and mice challenged with XMRV, but not preimmune serum. A total of 354 plasma samples from blood donors in the Reno/Tahoe area were screened for neutralization.

RESULTS

A total of 6.5% of donor samples gave moderate neutralization of XMRV, but not control pseudotypes. However, further testing by Western blot revealed no evidence of antibodies against MLVs in any of these samples. Furthermore, no evidence of infectious virus or viral nucleic acid was observed.

CONCLUSION

A microneutralization assay was developed for detection of XMRV and can be applied in a high-throughput format for large-scale studies. Although a proportion of blood donors demonstrated the ability to block XMRV envelope-mediated infection, we found no evidence that this inhibition was mediated by specific antibodies elicited by exposure to XMRV or MLV. It is likely that this moderate neutralization is mediated through another, nonspecific mechanism.

The Ebola virus glycoprotein and HIV-1 Vpu employ different strategies to counteract the antiviral factor tetherin

The antiviral protein tetherin/BST2/CD317/HM1.24 restricts cellular egress of human immunodeficiency virus (HIV) and of particles mimicking the Ebola virus (EBOV), a hemorrhagic fever virus. The HIV-1 viral protein U (Vpu) and the EBOV-glycoprotein (EBOV-GP) both inhibit tetherin. Here, we compared tetherin counteraction by EBOV-GP and Vpu. We found that EBOV-GP but not Vpu counteracted tetherin from different primate species, indicating that EBOV-GP and Vpu target tetherin differentially. Tetherin interacted with the GP2 subunit of EBOV-GP, which might encode the determinants for tetherin counteraction. Vpu reduced cell surface expression of tetherin while EBOV-GP did not, suggesting that both proteins employ different mechanisms to counteract tetherin. Finally, Marburg virus (MARV)–GP also inhibited tetherin and downregulated tetherin in a cell type–dependent fashion, indicating that tetherin antagonism depends on the cellular source of tetherin. Collectively, our results indicate that EBOV-GP counteracts tetherin by a novel mechanism and that tetherin inhibition is conserved between EBOV-GP and MARV-GP.

No evidence for XMRV nucleic acids, infectious virus or anti-XMRV antibodies in Canadian patients with chronic fatigue syndrome

The gammaretroviruses xenotropic murine leukemia virus (MLV)-related virus (XMRV) and MLV have been reported to be more prevalent in plasma and peripheral blood mononuclear cells of chronic fatigue syndrome (CFS) patients than in healthy controls. Here, we report the complex analysis of whole blood and plasma samples from 58 CFS patients and 57 controls from Canada for the presence of XMRV/MLV nucleic acids, infectious virus, and XMRV/MLV-specific antibodies. Multiple techniques were employed, including nested and qRT-PCR, cell culture, and immunoblotting. We found no evidence of XMRV or MLV in humans and conclude that CFS is not associated with these gammaretroviruses.

The SARS-coronavirus-host interactome: identification of cyclophilins as target for pan-coronavirus inhibitors

Coronaviruses (CoVs) are important human and animal pathogens that induce fatal respiratory, gastrointestinal and neurological disease. The outbreak of the severe acute respiratory syndrome (SARS) in 2002/2003 has demonstrated human vulnerability to (Coronavirus) CoV epidemics. Neither vaccines nor therapeutics are available against human and animal CoVs. Knowledge of host cell proteins that take part in pivotal virus-host interactions could define broad-spectrum antiviral targets. In this study, we used a systems biology approach employing a genome-wide yeast-two hybrid interaction screen to identify immunopilins (PPIA, PPIB, PPIH, PPIG, FKBP1A, FKBP1B) as interaction partners of the CoV non-structural protein 1 (Nsp1). These molecules modulate the Calcineurin/NFAT pathway that plays an important role in immune cell activation. Overexpression of NSP1 and infection with live SARS-CoV strongly increased signalling through the Calcineurin/NFAT pathway and enhanced the induction of interleukin 2, compatible with late-stage immunopathogenicity and long-term cytokine dysregulation as observed in severe SARS cases. Conversely, inhibition of cyclophilins by cyclosporine A (CspA) blocked the replication of CoVs of all genera, including SARS-CoV, human CoV-229E and -NL-63, feline CoV, as well as avian infectious bronchitis virus. Non-immunosuppressive derivatives of CspA might serve as broad-range CoV inhibitors applicable against emerging CoVs as well as ubiquitous pathogens of humans and livestock.

Different host cell proteases activate the SARS-coronavirus spike-protein for cell-cell and virus-cell fusion

Severe acute respiratory syndrome coronavirus (SARS-CoV) poses a considerable threat to human health. Activation of the viral spike (S)-protein by host cell proteases is essential for viral infectivity. However, the cleavage sites in SARS-S and the protease(s) activating SARS-S are incompletely defined. We found that R667 was dispensable for SARS-S-driven virus–cell fusion and for SARS-S-activation by trypsin and cathepsin L in a virus–virus fusion assay. Mutation T760R, which optimizes the minimal furin consensus motif 758-RXXR-762, and furin overexpression augmented SARS-S activity, but did not result in detectable SARS-S cleavage. Finally, SARS-S-driven cell–cell fusion was independent of cathepsin L, a protease essential for virus–cell fusion. Instead, a so far unknown leupeptin-sensitive host cell protease activated cellular SARS-S for fusion with target cells expressing high levels of ACE2. Thus, different host cell proteases activate SARS-S for virus–cell and cell–cell fusion and SARS-S cleavage at R667 and 758-RXXR-762 can be dispensable for SARS-S activation.

Mouse LSECtin as a model for a human Ebola virus receptor

The biochemical properties of mouse LSECtin, a glycan-binding receptor that is a member of the C-type lectin family found on sinusoidal endothelial cells, have been investigated. The C-type carbohydrate-recognition domain of mouse LSECtin, expressed in bacteria, has been used in solid-phase binding assays, and a tetramerized form has been used to probe a glycan array. In spite of sequence differences near the glycan-binding sites, the mouse receptor closely mimics the properties of the human receptor, showing high affinity binding to glycans bearing terminal GlcNAcβ1-2Man motifs. Site-directed mutagenesis has been used to confirm that residues near the binding site that differ between the human and the mouse proteins do not affect this binding specificity. Mouse and human LSECtin have been shown to bind Ebola virus glycoprotein with equivalent affinities, and the GlcNAcβ1-2Man disaccharide has been demonstrated to be an effective inhibitor of this interaction. These studies provide a basis for using mouse LSECtin, and knockout mice lacking this receptor, to model the biological properties of the human receptor.

Novel insights into proteolytic cleavage of influenza virus hemagglutinin

The influenza virus hemagglutinin (HA) mediates the first essential step in the viral life cycle, virus entry into target cells. Influenza virus HA is synthesised as a precursor protein in infected cells and requires cleavage by host cell proteases to transit into an active form. Cleavage is essential for influenza virus infectivity and the HA‐processing proteases are attractive targets for therapeutic intervention. It is well established that cleavage by ubiquitously expressed subtilisin‐like proteases is a hallmark of highly pathogenic avian influenza viruses (HPAIV). In contrast, the nature of the proteases responsible for cleavage of HA of human influenza viruses and low pathogenic avian influenza viruses (LPAIV) is not well understood. Recent studies suggest that cleavage of HA of human influenza viruses might be a cell‐associated event and might be facilitated by the type II transmembrane serine proteases (TTSPs) TMPRSS2, TMPRSS4 and human airway trypsin‐like protease (HAT). Here, we will introduce the different concepts established for proteolytic activation of influenza virus HA, with a particular focus on the role of TTSPs, and we will discuss their implications for viral tropism, pathogenicity and antiviral intervention. Copyright © 2010 John Wiley & Sons, Ltd.

Arabinogalactan isolated from cowshed dust extract protects mice from allergic airway inflammation and sensitization

BACKGROUND

Extract from cowshed dust (CDE) is a source of immunomodulating substances. We have previously shown that such substances protect from experimental allergic disorders in a mouse model of asthma.

OBJECTIVE

The objective of this study was to identify immunomodulatory molecules in extracts of dust from an allergy protective farming environment.

METHODS

Polysaccharides were isolated from CDE and plants by chromatography and precipitation with specific reagents. Polysaccharides were then characterized by nuclear magnetic resonance spectroscopy. Subsequently, the allergy-protective potential of isolated polysaccharides was tested in a mouse model of asthma.

RESULTS

The authors demonstrate that plant arabinogalactans are contained in CDE in high concentrations. The source of this arabinogalactan is fodder, in particular a prevalent grass species known as Alopecurus pratensis. Treatment of murine dendritic cells with grass arabinogalactan resulted in autocrine IL-10 production. Interestingly, these dendritic cells were not able to induce an allergic immune response. Furthermore, intranasal application of grass arabinogalactan protected mice from developing atopic sensitization, allergic airway inflammation and airway hyperreactivity in a mouse model of allergic asthma. This allergy-protective effect is specific for grass arabinogalactan because control experiments with arabinogalactan from gum arabic and larch revealed that these molecules do not show allergy-protective properties. This is likely because of structural differences because we were able to show by nuclear magnetic resonance spectroscopy that although they are predominantly composed of arabinose and galactose, the molecules differ in structure.

CONCLUSIONS

The authors conclude that grass arabinogalactans are important immunomodulatory substances that contribute to the protection from allergic airway inflammation, airway hyperresponsiveness, and atopic sensitization in a mouse model of asthma.