The role of BST2/tetherin in feline retrovirus infection

Pathogenic retroviral infections of mammals have induced the evolution of cellular anti-viral restriction factors and have shaped their biological activities. This intrinsic immunity plays an important role in controlling viral replication and imposes a barrier to viral cross-species transmission. Well-studied examples of such host restriction factors are TRIM5α, an E3 ubiquitin ligase that binds incoming retroviral capsids in the cytoplasm via its C-terminal PRY/SPRY (B30.2) domain and targets them for proteasomal degradation, and APOBEC3 proteins, cytidine deaminases that induce hypermutation and impair viral reverse transcription. Tetherin (BST-2, CD317) is an interferon-inducible transmembrane protein that potently inhibits the release of nascent retrovirus particles in single-cycle replication assays. However, whether the primary biological activity of tetherin in vivo is that of a restriction factor remains uncertain as recent studies on human tetherin suggest that it is unable to prevent spreading infection of human immunodeficiency virus type 1 (HIV-1). The feline tetherin homologue resembles human tetherin in amino acid sequence, protein topology and anti-viral activity. Transiently expressed feline tetherin displays potent inhibition of feline immunodeficiency virus (FIV) and HIV-1 particle release. However, stable ectopic expression of feline tetherin in a range of feline cell lines has no inhibitory effect on the growth of either primary or cell culture-adapted strains of FIV. By comparing and contrasting the activities of the felid and primate tetherins against their respective immunodeficiency-causing lentiviruses we may gain insight into the contribution of tetherins to the control of lentiviral replication and the evolution of lentiviral virulence

Understanding the Wolbachia-mediated inhibition of arboviruses in mosquitoes: progress and challenges

Arthropod-borne viruses (arboviruses) pose a considerable threat to human and animal health, yet effective control measures have proven difficult to implement, and novel means of controlling their replication in arthropod vectors, such as mosquitoes, are urgently required. One of the most exciting approaches to emerge from research on arthropods is the use of the endosymbiotic intracellular bacterium Wolbachia to control arbovirus transmission from mosquito to vertebrate. These α-proteobacteria propagate through insects, in part through modulation of host reproduction, thus ensuring spread through species and maintenance in nature. Since it was discovered that Wolbachia endosymbiosis inhibits insect virus replication in Drosophila species, these bacteria have also been shown to inhibit arbovirus replication and spread in mosquitoes. Importantly, it is not clear how these antiviral effects are mediated. This review will summarize recent work and discuss determinants of antiviral effectiveness that may differ between individual Wolbachia/vector/arbovirus interactions. We will also discuss the application of this approach to field settings and the associated risks

Feline restriction factors to lentiviral replication

Strong adaptive evolutionary forces shape the interactions between pathogens and their hosts and typically lead to a stable co-existence. In this process of co-evolution, mammals have developed restriction factors that limit retrovirus infectivity, replication or assembly and narrow the spectrum of potential host species. These restriction factors are either constitutively expressed, such as APOBEC3 proteins, cytidine deaminases that interfere with reverse transcription, or form part of the type I interferon-induced innate immunity, such as TRIM5, a member of the tripartite motif protein family that induces degradation of retroviral capsid, blocks reverse transcription, or tetherin (BST-2, CD317), which inhibits release of nascent viral particles from infected cells. Conversely, viruses have evolved antagonists of restriction factors or proteins that limit IFN-induced gene expression, thus evading immune surveillance. The interaction between host and viral components is delicately balanced and has a significant impact on disease outcome. Feline immunodeficiency virus (FIV), a lentivirus closely related to human immunodeficiency virus (HIV), is a recent introduction into domestic cats and causes an immunodeficiency syndrome analogous to human AIDS. Interestingly, non-domestic cats such as lion or pumas have co-existed with lentiviruses for prolonged periods of time and FIV infections are largely benign. Although plasma viral and proviral loads are high in both domestic and non-domestic cats, in vitro studies have shown that FIV infection of non-domestic cat T lymphocytes is significantly less efficient than that of domestic cat T cells. Thus, this thesis tests the hypothesis that the differential disease outcome of FIV infections in felids is caused by differences in lentiviral restriction factor activities or their sensitivities to FIV restriction factor antagonists. Data presented in this study show for the first time that feline APOBEC3 proteins are expressed in tissues and cell types relevant for FIV infection. The APOBEC3 proteins A3H and A3CH exhibited a high antiviral activity against FIV lacking the APOBEC3 antagonist Vif in single-cycle replication assays, with no difference in activity being detected between domestic and non-domestic cat proteins. However, domestic cat A3CH was significantly more sensitive to antagonism by FIV Vif than lion or puma A3CH, which would allow efficient viral replication in domestic cat T lymphocytes and subsequently lead to T cell loss and immunodeficiency. Furthermore, this thesis provides evidence that felid tetherins can prevent FIV particle release from producer cells in single-cycle replication assays; however, stable expression of domestic and non-domestic cat tetherins in feline cell lines did not abrogate FIV replication. Indeed, syncytium formation indicative of viral cell-to-cell spread was significantly enhanced in type I interferon-treated feline cells infected with CD134-independent strains of FIV which often arise in chronic (late) stages of FIV infections in vivo. Finally, this work reports the generation of a synthetic domestic cat TRIM5α-cyclophilin A fusion protein which was highly efficient at preventing FIV pseudotype and productive infection. This novel feline restriction factor represents a potent antiviral defence agent with very low potential for toxicity and could in future be used in gene therapy approaches to treat FIV-infected cats

Spindle-E acts antivirally against alphaviruses in mosquito cells

Mosquitoes transmit several human- and animal-pathogenic alphaviruses (Togaviridae family). In alphavirus-infected mosquito cells two different types of virus-specific small RNAs are produced as part of the RNA interference response: short-interfering (si)RNAs and PIWI-interacting (pi)RNAs. The siRNA pathway is generally thought to be the main antiviral pathway. Although an antiviral activity has been suggested for the piRNA pathway its role in host defences is not clear. Knock down of key proteins of the piRNA pathway (Ago3 and Piwi5) in Aedes aegypti-derived cells reduced the production of alphavirus chikungunya virus (CHIKV)-specific piRNAs but had no effect on virus replication. In contrast, knock down of the siRNA pathway key protein Ago2 resulted in an increase in virus replication. Similar results were obtained when expression of Piwi4 was silenced. Knock down of the helicase Spindle-E (SpnE), an essential co-factor of the piRNA pathway in Drosophila melanogaster, resulted in increased virus replication indicating that SpnE acts as an antiviral against alphaviruses such as CHIKV and the related Semliki Forest virus (SFV). Surprisingly, this effect was found to be independent of the siRNA and piRNA pathways in Ae. aegypti cells and specific for alphaviruses. This suggests a small RNA-independent antiviral function for this protein in mosquitoes

Validation of an automated enzyme immunoassay for interleukin-6 for routine clinical use

Serum levels of Interleukin-6 (IL-6), a proinflammatory cytokine, are increased in early stages of inflammatory diseases such as infection and sepsis. Assay systems which permit its measurement within a few hours and as a single measurement have not been reported so far. We therefore evaluated a now commercially available automated method for IL-6 measurement on the Cobas Core(R) immunological analyzer (Roche Diagnostic Systems) which enables single IL-6 measurement within about 1 hour. The automated assay correlates well with an established, manual microtiter plate assay (Biosource GmbH) which uses the same antibodies and reagents (r=0.98). Accuracy of the automated method was established by adding known amounts of IL-6 international reference preparation. Recovery of the international standard was in the range of 92-104%. The automated assay had a precision of singletons below 6% and was linear up to 2800 pg/ml. This automated assay provides a suitable, convenient and time saving method for measurement of IL-6 serum levels in the routine clinical laboratory

Restriction of the felid lentiviruses by a synthetic feline TRIM5-CypA fusion

Gene therapy approaches to the treatment of HIV infection have targeted both viral gene expression and the cellular factors that are essential for virus replication. However, significant concerns have been raised regarding the potential toxic effects of such therapies, the emergence of resistant viral variants and unforeseen biological consequences such as enhanced susceptibility to unrelated pathogens. Novel restriction factors formed by the fusion of the tripartite motif protein (TRIM5) and cyclophilin A (CypA), or "TRIMCyps", offer an effective antiviral defence strategy with a very low potential for toxicity. In order to investigate the potential therapeutic utility of TRIMCyps in gene therapy for AIDS, a synthetic fusion protein between feline TRIM5 and feline CypA was generated and transduced into cells susceptible to infection with feline immunodeficiency virus (FIV). The synthetic feline TRIMCyp was highly efficient at preventing infection with both HIV and FIV and the cells resisted productive infection with FIV from either the domestic cat or the puma. Feline TRIMCyp and FIV infection of the cat offers a unique opportunity to evaluate TRIMCyp-based approaches to genetic therapy for HIV infection and the treatment of AIDS

Non-structural proteins of arthropod-borne bunyaviruses: roles and functions

Viruses within the Bunyaviridae family are tri-segmented, negative-stranded RNA viruses. The family includes several emerging and re-emerging viruses of humans, animals and plants, such as Rift Valley fever virus, Crimean-Congo hemorrhagic fever virus, La Crosse virus, Schmallenberg virus and tomato spotted wilt virus. Many bunyaviruses are arthropod-borne, so-called arboviruses. Depending on the genus, bunyaviruses encode, in addition to the RNA-dependent RNA polymerase and the different structural proteins, one or several non-structural proteins. These non-structural proteins are not always essential for virus growth and replication but can play an important role in viral pathogenesis through their interaction with the host innate immune system. In this review, we will summarize current knowledge and understanding of insect-borne bunyavirus non-structural protein function(s) in vertebrate, plant and arthropod

Risks and Challenges of Arboviral Diseases in Sudan: The Urgent Need for Actions

The risk of emergence and/or re-emergence of arthropod-borne viral (arboviral) infections is rapidly growing worldwide, particularly in Africa. The burden of arboviral infections and diseases is not well scrutinized because of the inefficient surveillance systems in endemic countries. Furthermore, the health systems are fully occupied by the burden of other co-existing febrile illnesses, especially malaria. In this review we summarize the epidemiology and risk factors associated with the major human arboviral diseases and highlight the gap in knowledge, research, and control in Sudan. Published data in English up to March 2019 were reviewed and are discussed to identify the risks and challenges for the control of arboviruses in the country. In addition, the lack of suitable diagnostic tools such as viral genome sequencing, and the urgent need for establishing a genomic database of the circulating viruses and potential sources of entry are discussed. Moreover, the research and healthcare gaps and global health threats are analyzed, and suggestions for developing strategic health policy for the prevention and control of arboviruses with focus on building the local diagnostic and research capacity and establishing an early warning surveillance system for the early detection and containment of arboviral epidemics are offered

Investigating afforestation and bioenergy CCS as climate change mitigation strategies

The land-use sector can contribute to climate change mitigation not only by reducing greenhouse gas (GHG) emissions, but also by increasing carbon uptake from the atmosphere and thereby creating negative CO2 emissions. In this paper, we investigate two land-based climate change mitigation strategies for carbon removal: (1) afforestation and (2) bioenergy in combination with carbon capture and storage technology (bioenergy CCS). In our approach, a global tax on GHG emissions aimed at ambitious climate change mitigation incentivizes land-based mitigation by penalizing positive and rewarding negative CO2 emissions from the land-use system. We analyze afforestation and bioenergy CCS as standalone and combined mitigation strategies. We find that afforestation is a cost-efficient strategy for carbon removal at relatively low carbon prices, while bioenergy CCS becomes competitive only at higher prices. According to our results, cumulative carbon removal due to afforestation and bioenergy CCS is similar at the end of 21st century (600–700 GtCO2), while land-demand for afforestation is much higher compared to bioenergy CCS. In the combined setting, we identify competition for land, but the impact on the mitigation potential (1000 GtCO2) is partially alleviated by productivity increases in the agricultural sector. Moreover, our results indicate that early-century afforestation presumably will not negatively impact carbon removal due to bioenergy CCS in the second half of the 21st century. A sensitivity analysis shows that land-based mitigation is very sensitive to different levels of GHG taxes. Besides that, the mitigation potential of bioenergy CCS highly depends on the development of future bioenergy yields and the availability of geological carbon storage, while for afforestation projects the length of the crediting period is crucial.Peer Reviewe