We report complete genome sequences of two skunk adenovirus 1 (SkAdV-1) strains from African pygmy hedgehogs (Atelerix albiventris) in Germany. The genome sequences of 31,786 bp and 31,788 bp contain five indel sites previously noted in an SkAdV-1 strain from this host species but not from other species.

CX3CR1 is a chemokine receptor expressed on respiratory epithelial and immune cells and has been identified as a host factor important for infections with respiratory syncytial virus (RSV). In this review, we discuss the roles CX3CR1 plays in the pathogenesis of RSV infections as a viral entry receptor and regulator of immune cell trafficking. The conserved CX3C motif of the RSV G glycoprotein binds to CX3CR1 to mediate viral attachment and entry into respiratory epithelial cells. Furthermore, soluble G protein (sG) can bind to CX3CR1 and competitively interfere with cell signaling induced by the chemokine CX3CL1, resulting in inhibition of immune cell recruitment to the site of infection. In addition, sG engages TLR2 on epithelial cells, activating MyD88-NF-κB signaling and priming the NLRP3 inflammasome, which enhances viral dissemination through pyroptotic cell death. CX3CR1 signaling should be viewed as one of several overlapping host factors that—along with developmental changes in interferon and STAT3 signaling, airway anatomy, inflammasome activity, and tissue-resident memory responses—contribute to differential disease outcomes of RSV infection. A more complete molecular understanding of RSV-CX3CR1 interactions and downstream host responses may enable the development of improved prevention and treatment strategies.

The live-attenuated RVFV-4s vaccine against Rift Valley fever has demonstrated safety and efficacy across multiple animal models and in a phase 1 clinical trial. In this study, we examined its impact on innate immune responses and found that RVFV-4s enhances the expression of costimulatory molecules critical for T-cell activation, while triggering proinflammatory responses in primary human monocytes.

Phocine herpesvirus-1 (PhHV-1) can cause acute pneumonia and hepatitis with high morbidity and frequently fatal outcomes in young harbour seals (Phoca vitulina) and, occasionally, in grey seals (Halichoerus grypus). Here, we report the virological and pathomorphological findings of a PhHV-1 infection in 10 out of 90 investigated young harbour seals, collected between January 2020 and December 2021 from the Dutch North Sea coast, found either dead or suffering from severe respiratory distress resulting in euthanasia. Macroscopic findings included poor nutritional condition, poorly deflated and slightly consolidated lungs, as well as a friable and pale liver parenchyma. Moreover, six seals showed several co-morbidities such as septicaemia, pancreatitis and pneumothorax. Microscopic investigation revealed predominantly a non-suppurative peribronchitis and necrotizing bronchitis. Multifocal to coalescing necrotizing hepatitis and non-suppurative inflammation of the liver were the most striking lesions. Eosinophilic intranuclear inclusion bodies were seen in bronchial epithelial cells and hepatocytes in three and six cases, respectively. Using a monoclonal anti-PhHV-1 glycoprotein B antibody, viral antigen was detected in situ, specifically intra- and perilesional, in the lung and/or liver of eight seals. Electron microscopy of two selected cases demonstrated numerous intranuclear viral capsids and, within the cytoplasm, enveloped mature virions. A pan-Herpesviridae polymerase chain reaction using a degenerative primer set was used to confirm PhHV-1 infection. Genome fragments were detected in lung and liver samples. Collectively, these data indicate that PhHV-1 infection was the most likely cause of disease in these 10 animals, although several co-morbidities were also present. This indicates that monitoring of PhHV-1 infection status in harbour seals, especially juvenile animals, is an integral part of population health surveillance of susceptible phocid populations.

Respiratory syncytial virus (RSV) causes severe lower respiratory tract infections in infants, immunocompromised individuals, and older adults. Although vaccines and monoclonal antibodies have recently become available, understanding RSV pathogenesis remains essential for next-generation therapeutic strategies. RSV attachment glycoprotein G mediates virus binding through a CX3C-like chemokine motif, and its secreted soluble form (sG) possesses immunomodulatory properties. We showed that recombinant sG binds TLR2, inducing proinflammatory mediators. In vitro, sG pretreatment of airway epithelial cells enhanced viral replication upon infection, indicating functions beyond canonical receptor binding. We demonstrated that RSV sG can activate MyD88-NF-κB signalling in uninfected cells via TLR2, leading to NLRP3 upregulation and ROS accumulation. Subsequent RSV infection provides the second signal for caspase‑1 activation and pyroptosis, preconditioning neighbouring cells for inflammasome-dependent lysis and viral egress. Targeting the sG-TLR2 interface could reduce inflammatory damage and viral spread, providing a rationale for CX3C motif-directed interventions and NLRP3 inhibitors during infection.

Multiple outbreaks with high mortality rates and a pattern of disease occurrence similar to peste des petits ruminants (PPR) were observed in sheep and goats across many states of Sudan between 2015 and 2018. Therefore, this study aimed to investigate and identify the cause of these disease outbreaks. A total of 276 blood and lung tissue samples were collected from infected sheep (n = 223) and goats (n = 53). Sample analysis in an IC-ELISA revealed the presence of the PPRV antigen in 56.9% of sheep and 62.3% of goat samples. Twenty-seven [sheep (18) and goats (9)] PPRV-positive samples from IC-ELISA were subsequently confirmed positive using the PPRV N-gene-based RT-PCR. Two PPR viruses were isolated from infected small ruminant lung tissues in Vero cells. The partial N-gene sequences for five PPRV strains originating from sheep and goats were determined. Phylogenetic tree grouped PPRV strains identified in this study in lineage IV in sub-lineage NEA (North-East Africa), with the highest sequence identity observed with strains circulating in North African countries. This study and earlier published phylogenetic analysis and patterns of animal movements suggest that the transboundary transmission of PPRV lineage IV strains between East and North African countries has been happening since 2008 and established a new North-East Africa episystem that needs to be disrupted for the successful global eradication of PPR.

Respiratory syncytial virus (RSV) is a leading cause of respiratory tract infections, leading to significant morbidity, hospitalizations, and mortality among high-risk populations. Despite the recent advent of vaccines and monoclonal antibodies, options to treat RSV infections are limited. Detailed understanding at the molecular level of virus-host interactions associated with disease severity may aid development of novel intervention strategies. In this study, we examined the role of transcription factor STAT1 in regulating cholesterol metabolism during RSV infection of epithelial-like cells. We demonstrated that CRISPR/Cas9-mediated STAT1 knock-out affected activation of the SREBP-SCAP cholesterol biosynthesis pathway, leading to intracellular cholesterol accumulation and increased RSV-induced syncytia formation. Pharmacological reduction of cholesterol levels blunted RSV-induced syncytia formation and affected the stability of the RSV fusion protein. These findings reveal a STAT1-dependent immune-metabolic pathway that constrains RSV dissemination through syncytia formation, which could be a novel target for intervention strategies.

BACKGROUND:Rift Valley fever virus (RVFV) is a mosquito-borne virus that affects livestock and humans. The 4-segmented live-attenuated human vaccine candidate hRVFV-4s has shown a strong safety profile and excellent tolerability in healthy adults during a first-in-human clinical trial, while also eliciting both neutralizing antibody and T-cell responses. Recognizing the critical role of cellular immunity in vaccine-induced protection and immune durability, this study aimed to comprehensively characterize the cytokine secretion profile, the antigen-specific breadth of RVFV-specific T-cell responses and memory T-cell formation, elicited by a single dose of hRVFV-4s, up to 6 months post-vaccination. METHODS:Peripheral blood mononuclear cells collected during the first-in-human clinical trial at 0, 7, 14, and 180 days post hRVFV-4s vaccination were analyzed for RVFV-specific T-cell responses using multiparametric flow cytometry and multiplex cytokine detection assays. RESULTS:A strong N-specific peripheral CD4+ and CD8+ T-cell response was detected among vaccinees, accompanied by Gn- and Gc-specific T cells, albeit the latter at comparatively lower frequencies. These responses were mediated by polyfunctional CD4+ and CD8+ T cells, which were detectable as early as at 2 weeks post-vaccination. The RVFV-specific T-cells were primarily of the effector memory phenotype and demonstrated cytokine secretion profiles characteristic of a T helper 1 (Th1)-type. CONCLUSIONS:This study demonstrates that the cell-mediated immune response induced by a single dose of the hRVFV-4s vaccine is characterized by robust, virus-specific Th1-type CD4+ and CD8+ T-cell response. Together with previously reported virus-neutralizing antibody responses, these coordinated immune responses are expected to contribute to vaccine-mediated protection.

Long-term persistent measles virus (MeV) infection of the central nervous system (CNS) can result in subacute sclerosing panencephalitis (SSPE), an invariably fatal late neurological complication of measles. Analogous SSPE-like chronic diseases have also been reported in adult dogs, cetaceans, and more recently harbor seals following infection by canine distemper virus (CDV), dolphin morbillivirus (DMV), and phocine distemper virus (PDV), respectively. Here, we characterize different animal morbilliviruses (CDVlynx, PDV2001, PDV2014, and DMV232-18) that persisted in the CNS of their respective host species for several years after the initial infections. The CDVlynx and DMV232-18 strains encode nonfunctional matrix proteins and hyperfusogenic fusion proteins which are hallmark features of SSPE MeV strains. The complex mutational profile apparent in the PDV2001 strain also has parallels with MeV strains from SSPE cases. In contrast, the PDV2014 strain encodes for a nonfunctional matrix protein but an unmodified F protein supporting the evolutionary precedence of M protein changes in facilitating long-term morbillivirus infections of the CNS. Consequently, our findings show that similar evolutionary pathways across different animal species drive morbilliviruses to evolve analogous mechanisms favoring virus persistence in the CNS and the development of chronic neurological disease. Such naturally occurring chronic animal morbillivirus infections of the CNS provide natural analogues for studying the evolutionary trajectory and molecular basis of the pathogenesis of SSPE in humans. This may pave the way for developing early diagnostics and intervention strategies.

Rift Valley fever virus (RVFV) is a Phlebovirus causing febrile and haemorrhagic illness in ruminants and humans. The viral protein NSs is a major virulence factor that suppresses the IFN-β response in various hosts. Hence, RVFV variants lacking functional NSs, such as Clone 13, are highly attenuated. It is speculated that from the sites of infection, the virus disseminates to the target organs via the bloodstream. We hypothesized that primary infection of circulating immune cells and their response to infection are critical factors determining systemic RVFV spread and pathogenesis. Human PBMC from healthy blood donors were exposed to both wild-type (WT) RVFV and Clone 13 strains. Flow cytometric analysis revealed that monocytes expressing LRP1, a known RVFV receptor, are target cells for RVFV. RNA-seq analysis of monocytes exposed to WT and Clone 13 strains showed a large number of differentially expressed genes compared to mock-exposed cells. Various genes involved in antiviral immune mechanisms were specifically modulated in monocytes either in response to WT or Clone 13 infection. Expression of genes encoding key inflammatory mediators, such as CCL2, CD40, and CD83, was only upregulated in Clone 13-infected monocytes, whereas IFNB1 and NFKB1 were downregulated specifically in WT-infected monocytes. Taken together, our findings suggest that RVFV NSs dampen the innate immune responses in monocytes which may be critical not only in RVFV pathogenesis but also in the induction of virus-specific immune response.

Phocine distemper virus caused epizootics of fatal pneumonia in North Sea harbor seals in 1988 and 2002. Two seals that stranded years later were infected with defective phocine distemper virus variants that caused severe encephalomyelitis. Old seal encephalitis resembled subacute sclerosing panencephalitis in humans and old dog encephalitis in canines.

Respiratory syncytial virus (RSV) is one of the leading causes of respiratory tract infection in children, immunocompromised individuals and older adults. Vaccines have recently been approved for use in adults and although further efforts to develop suitable interventions for children are ongoing, there are limited animal models for RSV infection. For preclinical efficacy testing of prophylactic and therapeutic treatments cotton rat and ferret models can be used. However, these can be expensive, difficult to source and house, and often have limitations such as insufficient virus replication in the respiratory tract and/or lack of horizontal transmission. In this study, Syrian hamsters (Mesocricetus auratus), which are relatively cheap, easy to source and house, were inoculated intranasally with a recombinant RSV-A-0594 strain expressing EGFP and using virological and pathological analyses. Viral replication was assessed and compared to viral replication in the ferret model. Although there was limited virus infection of the lower respiratory tract of Syrian hamsters, we show that a contemporary recombinant RSV-A strain replicates efficiently in the upper respiratory tract of Syrian hamsters (titers up to 4.5 Log10 TCID50/g and 12 Log10 RNA copies/g). These titers are comparable to those found in the ferret upper respiratory tract tissues post-infection with the same virus strain (up to 6.0 Log10 TCID50/g and 12 Log 10 RNA copies/g). Fluorescent regions indicating virus infection were macroscopically visible under UV-light in the nasal turbinates and histological assessment showed mucosal inflammation with necrotic cells in this tissue. In summary, Syrian hamsters generally displayed less severe systemic and pulmonary changes than ferrets, but do appear to be a promising model for upper respiratory tract infection with RSV.

The discovery of several novel hepatovirus species in marine and terrestrial mammals has expanded the recognised members of the genus Hepatovirus and has provided better understanding on the evolutionary origins of human hepatovirus A (HAV). Using high throughput sequencing we detected a seal hepatovirus (SealHAV_NL/PV/21), in liver tissue of a deceased harbor seal (Phoca vitulina) originating from the Dutch North Sea coast. RT-PCR screening of liver samples of 88 harbor seals and 12 grey seals (Halichoerus grypus) from the same region identified seal hepatovirus in nine juvenile harbor seals in which minor sequence variation was observed in the VP1 gene. Whole-genome sequence analysis showed that SealHAV_NL/PV/21 displayed 95.6% nucleotide indentity to New England seal hepatovirus but had a 5′-UTR which contained additional 51 bp. Phylogenetic analysis showed that seal hepatoviruses clustered in a monophyletic group separate from other hepatovirus species that have been identified in terrestrial mammals. Assessment of seal hepatovirus RNA loads in organs of all infected animals showed that the liver had the highest number of RNA copies with up to 107 RNA copies per mg of tissue. Seal hepatovirus RNA was readily detected by in situ hybridization in hepatocytes in the liver but was not associated with pathological lesions. Serological screening of 90 contemporary seal sera using a HAV-based ELISA showed the presence of hepatovirus antibodies in 14 harbor seals and one juvenile grey seal. These findings collectively show that seal hepatovirus is enzootic among seals of the North Sea, causing quiescent infections in young animals.

BACKGROUND:Since the onset of the COVID-19 pandemic, SARS-CoV-2 neutralising monoclonal antibodies (mAbs) are being developed for clinical use. With the appearance of new virus variants, most mAbs lost their virus-neutralising activity, highlighting the complexity of mAb development under conditions of continuous SARS-CoV-2 evolution. METHODS:Hamsters were treated with SARS-CoV-2 neutralising mAbs and then challenged with SARS-CoV-2. Recombinant VSV expressing the spike protein of SARS-CoV-2 was utilised in an in vitro system to select for antibody escape variants. Surface plasmon resonance measurements were performed to characterise the binding affinity and epitope of various mAbs. Fc-mediated effector functions of neutralising and non-neutralising mAb combinations were determined via multiple in vitro assays. FINDINGS:Few of the mAb treated and infected hamsters experienced breakthrough infections, which derived from mutated virus that emerged in vivo. We developed an in vitro antibody escape assay that recapitulated the in vivo situation and we found that somatic hypermutations (SHM) affected the profile of viral escape hotspots that mAbs selected for. Pairwise combination of mAbs binding non-overlapping epitopes suppressed the emergence of viral mutants. The formulation with a third, non-neutralising mAb enhanced the Fc-mediated effector functions of the mAb treatment in an additive manner. INTERPRETATION:We conclude that treatment with single mAbs rapidly leads to the formation of novel virus variants. An important function of SHM is to suppress the emergence of viral antibody escape variants. Our data suggest that the anticipatory B cell memory can be harnessed to design combinations of SARS-CoV-2 neutralising mAbs that have a reduced risk to induce viral escape. FUNDING:This study was supported by public funding from the German Research Foundation (DFG), the Federal Ministry of Education and Research (BMBF), the COVID-19-Research Network of the State of Lower Saxony (COFONI), the German Centre for Infection Research (DZIF), and the Helmholtz Association of German Research Centres.

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections worldwide, particularly affecting infants, older adults, and immunocompromised individuals. Understanding the cellular immune response to RSV infection is essential for developing effective treatments for infection and its complications. In this study, we investigated the susceptibility of blood-derived primary monocytes and monocytic THP-1 cells to infection with a contemporary RSV A-ON1 strain and characterized the subsequent cytokine and chemokine secretion, as well as the expression of surface markers involved in antigen presentation. Our findings demonstrate that primary monocytes and related THP-1 cells are permissive to abortive infection by RSV, leading to increased expression of proinflammatory cytokines and chemokines, including IP-10, IL-6, and CCL2. Furthermore, primary monocytes expressed CD80, CD86, and HLA-DR upon direct infection or through potential paracrine stimulation. Collectively, these findings demonstrate the activation of monocytes by RSV infection, suggesting their contributory role in orchestrating early immune responses during infection.

The availability of influenza vaccines that can induce broadly protective immune responses is highly desirable and could also mitigate the impact of future influenza pandemics. Ideally, these vaccines also induce virus-specific CD8 + T cells, which have been identified as an independent correlate of protection. In the present study, we explored the use of an artificial immunogen that comprises of twenty highly conserved influenza virus CD8 + T cell epitopes with an HLA coverage of 99.5% of the world population. The highly attenuated viral vector Modified Vaccinia virus Ankara (MVA) was used to deliver the artificial poly-epitope sequence (rMVA-PE) and by using T cell lines raised against individual epitopes, we confirmed that the epitopes are liberated from the artificial immunogen. For efficient antigen processing and presentation, the epitopes were separated by spacer sequences. Stimulation of peripheral blood mononuclear cells of HLA-typed blood donors with rMVA-PE resulted in the activation of influenza virus-specific T cell responses. Furthermore, immunization of humanized HLA-A2.1-/HLA-DR1-transgenic H-2 class I-/class II-knockout mice (HLA-A*02:01) with rMVA-PE induced influenza virus-specific CD8 + T cell responses. Thus, rMVA-PE proved to be immunogenic both in vitro and in vivo and constitutes a promising vaccine candidate for the induction of cross-reactive CD8 + T cell responses that could afford protection against antigenically distinct influenza A viruses (IAV) of various subtypes and species, and is currently considered for further clinical testing.

Einleitung Phopivirus, Genus Hepatovirus, ist dem humanen Hepatitis A Virus ähnlich und wurde in den USA erstmals 2015 bei Seehunden (Phoca vitulina) und einer Sattelrobbe (Phoca groenlandica) nachgewiesen.

Tick-borne encephalitis virus (TBEV) vaccine breakthrough (VBT) infections are not uncommon in endemic areas. The clinical and immunological outcomes have been poorly investigated. We assessed the magnitude and specificity of virus-specific antibody and T cell responses after TBE in previously vaccinated subjects and compared the results with those of unvaccinated TBE patients and study subjects that received vaccination without VBT infection. Symptomatic TBEV infection of unvaccinated study subjects induced virus-specific antibody responses to the E protein and non-structural protein 1 (NS1) as well as T cell responses to structural and other non-structural (NS) proteins. After VBT infections, significantly impaired NS1-specific antibody responses were observed, while the virus-specific T cell responses to the NS proteins were relatively strong. VBT infection caused predominantly moderate to severe disease during hospitalization. The level of TBEV EDIII- and NS1-specific antibodies in unvaccinated convalescent patients inversely correlated with TBE severity and neurological symptoms early after infection.

Background/Objectives: Respiratory syncytial virus (RSV) is a leading cause of respiratory infections, particularly affecting young infants, older adults, and individuals with comorbidities. Methods: This document, developed as a consensus by an international group of experts affiliated with the World Association of Infectious Diseases and Immunological Disorders (WAidid), focuses on recent advancements in RSV prevention, highlighting the introduction of monoclonal antibodies (mAbs) and vaccines. Results: Historically, RSV treatment options were limited to supportive care and the monoclonal antibody palivizumab, which required multiple doses. Recent innovations have led to the development of long-acting mAbs, such as nirsevimab, which provide season-long protection with a single dose. Nirsevimab has shown high efficacy in preventing severe RSV-related lower respiratory tract infections (LRTIs) in infants, reducing hospitalizations and ICU admissions. Additionally, new vaccines, such as RSVpreF and RSVpreF3, target older adults and have demonstrated significant efficacy in preventing LRTIs in clinical trials. Maternal vaccination strategies also show promise in providing passive immunity to newborns, protecting them during the most vulnerable early months of life. This document further discusses the global burden of RSV, its economic impact, and the challenges of implementing these preventative strategies in different healthcare settings. Conclusions: The evidence supports the integration of both passive (mAbs) and active (vaccines) immunization approaches as effective tools to mitigate the public health impact of RSV. The combined use of these interventions could substantially reduce RSV-related morbidity and mortality across various age groups and populations, emphasizing the importance of widespread immunization efforts.