- Volume 1, Issue 1A, 2019
Volume 1, Issue 1A, 2019
- Poster Presentation
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- Virology Workshop: Pathogenesis
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Aberrant RNA replication products of highly pathogenic avian influenza viruses and its impact in the mammalian associated cytokine storm
More LessHighly pathogenic avian influenza viruses (HPAIVs), can sporadically cross the species barrier and cause zoonotic infections in mammalian hosts (including humans), with often fatal consequences. Severe disease has been associated with an overexuberant host innate immune response known as hypercytokinema (cytokine storm) where excessive levels of pro-inflammatory cytokines are produced. Previous work in our laboratory shows that high levels of viral replication by HPAIV in murine myeloid immune cells correlated with high cytokine levels and mapped this phenotype to the polymerase genes. Innate sensing of IAV is performed by the cytoplasmic helicase RIG-I, which recognises blunt ended double stranded RNA with 5’-triphosphate extremities, a pattern present in the viral genome. Defective viral genomes (DVGs) can be produced by aberrant RNA replication and these are also recognised by RIG-I and could play a role in hypercytokinemia. Our studies aim to probe for the presence of DVGs in influenza infected cells in vitro, and in lung samples from infected mice in vivo as well as in murine immune cells ex vivo, using RT-PCR and sequencing. We will establish whether DVGs are correlated to pathogenicity and high pro-inflammatory cytokine levels. Preliminary data utilising minigenome assays show that the polymerase genes from an HPAIV H5N1 strain do generate DVGs, whereas DVGs could not be detected from a H3N2 seasonal polymerase. Ultimately, we aim to identify mutations within the polymerase genes that contribute to virulence and by using reverse genetics, create mutant viruses that test the hypothesis that aberrant polymerase activity drives hypercytokinemia.
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Human immunodeficiency virus type 2 (HIV-2) dynamics and whole genome deep sequence analysis in Mauritian-origin cynomolgus macaques (Macaca fascicularis)
More LessHuman immunodeficiency virus type 2 (HIV-2) is a pathogenic human retrovirus with a distinct natural history and lineage derivation from pandemic HIV-1. HIV-2 infections in humans are the result of zoonotic transmission from sooty mangabey monkeys naturally infected with SIVsm. Unlike HIV-1, HIV-2 infects other non-human primate species, including baboons and macaques. We determined the infectivity and infection kinetics of a Gambian-origin HIV-2 isolate HIV-2SBL6669 strain in Mauritian-derived cynomolgus macaques (MCM) in the context of a heterologous superinfection resistance study. The ability of HIV-2 to replicate in unvaccinated MCM with limited host genetic MHC and TRIM5 spectrum was determined where the kinetics of plasma HIV-2 RNA mimic the phenotypic response typically observed in HIV-2-infected humans. HIV-2SBL669 replication is not completely restricted in this species and may establish a persistent infection. This is determined by moderate peak viral loads (105–6 log10 HIV-2 RNA copies/ml) controlling to a low level determined by qRT-PCR and detectable in-situ hybridisation signals in lymphoid tissue 20 weeks after challenge. In MCM vaccinated for 20 weeks with an attenuated SIV, we observed high levels of superinfection resistance as determined by virus-specific PCR analysis of tissues and low total plasma viral RNA levels in vaccinates compared to unvaccinated HIV-2 controls. Recovery of whole viral genome and next generation sequence analysis of challenge controls, including low-level breakthrough variants characterises viral challenge and vaccine-escape viruses. HIV-2 in cynomolgus macaques recapitulates many of the features of HIV-2 infections in humans.
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Infectious bursal disease virus (IBDV) replicates in the gut associated lymphoid tissue and alters the gut microbiome of chickens
More LessInfectious bursal disease virus (IBDV) is a member of the Birnaviridae family that infects B cells in chickens, leading to immunosuppression and mortality. Immunosuppression is known to exacerbate the colonisation and shedding of zoonotic gut bacteria, for example Campylobacter jejuni, Salmonella Enteritidis and Escherichia coli, for reasons that are poorly understood. In order to address this, we infected groups of chickens (n=6) with either a classical strain (F52-70) or a very virulent strain (UK661) of IBDV. At 3 days post-infection, both strains were found to replicate in the gut-associated lymphoid tissue of thecaecaltonsils. 16 s rRNA sequencing revealed that in birds infected with IBDV, regardless of strain, there was a decrease in bacterial diversity in the caecal tonsils, but an increase in diversity of bacteria shed from the cloaca. Secretary IgA binding to commensal bacteria is known to influence the composition of the microbiome, and we speculate that IBDV alters the repertoire of sIgA thereby altering the microbiome composition. Interestingly, we found the number of clostridial species was reduced following IBDV infection. Clostridial species have been shown to induce Treg populations in mice and we speculate that IBDV-mediated changes in the microbiome affect the population of different immune cells in the mucosa. Taken together, we hypothesise that IBDV infection directly affects the B cell population and indirectly affects other immune cell populations in the gut and alters the gut microbiome, which leads to a more favourable environment for zoonotic bacterial infections to colonise.
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Zika virus: out of sight but not out of the mind. Viral persistence and host responses within the central and peripheral nervous systems
Following the rapid spread of Zika virus infection through the Caribbean and Americas, model systems of Zika virus infection have been established to determine disease pathology and potential health impacts for those infected with this neurotropic flavivirus. NIBSC has established both Old World (rhesus and cynomolgus macaques) and New World (red-bellied tamarins) non-human primate disease models of human Zika virus infection. Animals were infected sub-cutaneously with the Caribbean Zika isolate PRVABC59 and pairs terminated during primary viremia (3 dpc) or post clearance of plasma viremia (42 and 101 dpc). FFPE sections from multiple tissues, including brain and peripheral nerves were analysed for Zika virus RNA (RNAscope), viral proteins and host responses (immunohistochemistry). All animals became infected and rapidly cleared high levels of peripheral viremia. Zika virus RNA was detected in multiple tissues from 3 dpc with low levels of viral RNA and viral NS1 protein remaining detectable through to 101 dpc. Viral RNA was associated with both glial and neuronal cells throughout the brain and schwann cell nuclei in peripheral nerves. Neuroinflammation (astrogliosis, microgliosis, peri-vascular cuffing) and increased levels of CD3+, CD8+ or CD45+ cells were present from 3 dpc through to 101 dpc. Disruption of MAP2 neuronal dendrite staining and peripheral nerve myelin basic protein staining was also observed. The continued detection of Zika virus within tissues 3 months post infection and in the absence of a detectable peripheral viremia raises questions regarding potential long term effects of this virus and associated inflammatory responses within the nervous systems.
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Zika virus: persisting tissue reservoirs and their potential for clinically relevant pathology
The rapid spread of Zika virus through the Caribbean and Americas appears associated with greater levels of congenital zika and Guillain-Barre syndromes than previously seen. In addition, new disease pathologies such as persisting sexual transmission and severe liver injury have been identified. With zika vaccines years away from licensing an understanding of potential long-term health consequences following adult infection needs to be gained, especially where organs from infected people may be used for transplantation. To model the pathology of human Zika virus infection Old World and New World non-human primates were sub-cutaneously infected with a Caribbean Zika virus isolate. Following termination during primary viremia or later time points post peripheral viral clearance FFPE tissue sections were analysed for Zika virus RNA (RNAscope) and host responses (immunohistochemistry). Zika virus RNA was detected in multiple tissues from 3dpc with low levels of viral RNA detectable by RNAscope through to 101 dpc. New World non-human primates retained higher levels of persisting virus within tissues, notably within spleen, small intestine, kidney, liver and genital tissues. Differing pathologies were observed with Zika virus detected clustered within kidney glomeruli and associated with liver inflammatory infiltrates within New World species. Such pathologies are being documented in adults with resolved primary infection symptoms. This includes clinical complications following solid organ transplantation where immune suppression may allow viral reactivation either from the patient or transplanted organ. In the absence of a protective vaccine the potential risks from persisting viral reservoirs needs to be understood to ensure appropriate clinical management.
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Investigating the requirement for host cell chloride ion channels during human respiratory syncytial virus infection
More LessIon channels are a diverse class of transmembrane proteins, which selectively allow ions across cellular membranes, influencing a multitude of cellular processes. Modulation of these channels by viruses is emerging as an important host-pathogen interaction, and has been demonstrated to regulate critical stages of the virus multiplication cycle including entry, replication and egress. Human respiratory syncytial virus (HRSV) causes severe respiratory tract infections (RTIs) globally and is one of the most lethal respiratory pathogens for infants in developing countries, with many cases leading to severe lower respiratory tract infections, and the development of bronchiolitis. Evidence also suggests that childhood HRSV infection contributes towards the increased incidence of adult asthma. There is no HRSV vaccine, and the only treatment is immunoprophylaxis that is prohibitively expensive and only moderately effective; thus new treatment options are required. In this study, by infecting human lung epithelial cells with HRSV in the presence of various broad-range channel modulators, Cl- channels were identified to play an important role during HRSV infection. Time of addition assays using these broad-acting Cl- channel blockers identified the stages within the HRSV lifecycle that were dependant on Cl- channel activity, and the use of family-specific Cl- channel blocking drugs identified a small sub-family of Cl-channels which, when inhibited, resulted in significantly reduced HRSV multiplication. We are now identifying the specific Cl- channel(s) facilitating the multiplication of HRSV using genetic means, and well as assessing the importance of Cl- channels in replication cycles of other negative sense RNA viruses.
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Unravelling the features of Influenza as entry mechanism
Influenza virus is the causative agent of the ‘flu’. According to the World Health Organisation, Influenza causes up to 5 million cases of severe flu and 500 000 deaths annually. To release its genome inside the cell and start an infection, Influenza virus must fuse its envelope with the endosomal membrane of the host, making this process an excellent drug target. In order to attempt to control, or better yet, eradicate this pathogen, a greater understanding of its entry mechanism, a fundamental aspect of the viral life cycle, is required. It is well established that Influenza A virus (IAV) fusion is driven by the viral glycoprotein hemagglutinin (HA), which when exposed to low pH transitions from a meta-stable pre-fusion to post-fusion state. However, it is becoming increasingly apparent that the ionic balance of the endosomes also has a significant role in the entry of enveloped viruses. Specifically, our preliminary studies on Influenza virus suggest that K+ concentrations within the endocytic pathway play a significant role in Influenza A fusion events. Through the use of broad-spectrum K+ channel inhibitors, a dose-dependant reduction in Influenza infectivity in tissue culture can be observed. Further to these studies, we have isolated Affimers (novel antibody-like proteins that can be produced in large quantities in E. coli) that recognise HAs from different Influenza subtypes (H3N2 and H1N1). Using these Affimers, we aim to develop an early detection method to distinguish between bacterial respiratory infections and ‘the flu’ to alleviate mounting pressures on an already diminishing antibiotic treatment system.
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Effect of antibacterial lipids on biofilm formation by Streptococcus mutans
More LessStreptococcus mutans is the major cariogenic organism associated with Dental Caries, a widespread chronic disease of the oral cavity (Muras et al. 2018). It is associated with oral biofilm formation, production of organic acids, and has the capacity to out-compete non-cariogenic commensal species (Lemos et al. 2013). Recent studies carried out on fatty acids demonstrated effective antimicrobial activity against S. mutans (Hughes, 2014). This study will evaluate the activity of lipids on S. mutans biofilm formation and proposes that dietary constituents may be used as a natural therapy to maintain oral hygiene. Clinical isolate S. mutans 3014 D5929 was exposed to various concentrations of lipid for 24 h. Crystal violet assay was performed for quantification of biofilm biomass. Fluorescent microscopy using SYTO® 9 and Alexa Fluor® 647-labelled dextran conjugate was performed to visualise biofilm formation pre- and post-exposure to MCO. Biofilm biomass was reduced for all lipid concentrations. Fluorescent microscopy indicated a significant reduction in bacterial cell number and a lack of structural biofilm upon exposure to fatty acid mixtures when compared to control. The research demonstrated that lipid does have S. mutans based antimicrobial and antibiofilm capabilities.
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D-Amino acids do no inhibit biofilm formation in Staphylococcus sp.
More LessD-amino acids are responsible for cell wall re-modelling in Staphylococcus and are capable of inhibition and mature biofilm disassembly. Staphylococcus aureus and Staphylococcus epidermidis are recognised as recurrent nosocomial pathogens and a common cause of biofilm-associated infections. The combination of amino acids used in the study consisted of d- and l- isomers of tyrosine, methionine, tryptophan and phenylalanine. A semiquantitative microplate crystal violet assay was used to assess the effect of amino acids on biofilm development. Biofilm viability staining using fluorescent microscopy was performed to assess the effect of the amino acid mixtures on biofilm development on submerged surfaces. None of the amino acids when tested individually or as a mixture could reduce biofilm formation. However, at the highest concentration tested 25 mmol 1−1 equimolar D-amino acid mixture of tryptophan, phenylalanine, tyrosine and methionine caused a considerable biofilm inhibition in three Staphylococcus strains. Microscopy analysis showed that initial surface attachment remained unaffected at 25 mmol 1−1 mixture of d-amino acids but bacteria did not proceed to form mature biofilms. This suggests inhibition of protein synthesis or a lack of polysaccharide extracellular adhesin formation as no aggregates were observed. The reported bioactivity of D-amino acid on biofilm development and disassembly has been conflictual. It has been established that D-amino acids are incorporated in the bacterial cell wall suggesting they play a role in the complexity of biofilm lifecycle. However, our study indicates that they play no direct role in the inhibition of biofilm formation in Staphylococcus.
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