Alsharifi L6 I&IB Ebola.pdf

Ebola virus infections Dr Mohammed Alsharifi School of Biological Sciences The University of Adelaide [email protected]  Ebola outbreaks Ebola virus: from discovery to vaccine. Nature...

Ebola virus infections Dr Mohammed Alsharifi School of Biological Sciences The University of Adelaide [email protected]  Ebola outbreaks Ebola virus: from discovery to vaccine. Nature Reviews Immunology 3, 677 1st outbreak: The Democratic Republic of Congo, in 1976: 318 cases and 280 deaths (88% fatality). 26 more outbreaks occurred in multiples African countries. http://papyrus.greenville.edu/2014/09/the-u-s-increases- response-to-ebola-outbreak/  2014-2016 outbreak The Public Health Emergency of International Concern (PHEIC) related to Ebola in West Africa was lifted on 29 March 2016. A total of 28 646 confirmed, probable and suspected cases have been reported in Guinea, Liberia and Sierra Leone, with 11 323 deaths.  http://www.premiumtimesng.com/news/231871-fourth-ebola-death-confirmed.html https://www.cdc.gov/ebola/outbreaks/index.html  Virus Classification http://www.nlv.ch/Virologytutorials/Classification.htm  Virus structure Filamentous 790 nm long for Ebolavirus. Diameter is about 80nm. Proc Natl Acad Sci U S A. 2011 May 17;108(20):8426-31. doi: 10.1073/pnas.1019030108. Epub 2011 May 2. Genome organization: Negative-stranded RNA linear genome, about 18-19 kb in size. Encodes for seven proteins. NP: Nucleoprotein VP30: Minor nucleoprotein VP35: Ploymerase complex protein VP40: Matrix GP: envelope glycoprotein L: RNA dep RNA Pol sGP: secretory glycoprotein might be anti-inflammatory. VP24: Inhibits STAT1 nuclear transport and render cells refractory to IFNs Pathogenesis of Virus Infection (In general) “viruses encounter susceptible hosts to establish infection of single cells and causing cell destruction and/or dysfunction and inducing an immune response” 1.Transmission: movement from one host to another 2. Viral Replication: Establishment of single cell infection “Direct effect of virus replication on infected cells” 3. Virus-Host interaction Host Defense Systems: “antiviral immunity both innate and adaptive” Localized infection versus Systemic infection Transient or Persistent infection  Virus entry into the body. (In general) Tissues of the body are lined by epithelium Epidermis (external) Mucosa (internal) Routes of virus entry: Respiratory: airborne Enteric: food/water borne or “fecal contamination” Sexually transmitted Skin: Tough outer layer is nearly impenetrable cuts, scrapes, bites, needles “Blood borne” Zoonotic  Transmission Animal hosts: Fruit bats, chimpanzees, gorillas, monkeys, forest antelope, and porcupines  Distribution of the four mainland Australian flying- fox species. Map by Pia Lentini 2018. https://www.theguardian.com/environment/2024/jan/29/the-megabats-of-adelaide-sa-adjusts-to- new-and-growing-colonies-of-flying-foxes  http://www.idausa.org/bushmeat-ebola-connection/ http://squathole.wordpress.com/2014/03/28/sorry-bats-off/ Need to consider: http://www.catholic.org/news/i nternational/africa/story.php?id Close contact with the blood, secretions, organs, or other bodily fluids of infected =54695 animals Handling infected animals found ill or dead in rainforests. Consumption of infected bushmeat Touching contaminated objects Ebola virus transmission: Virus gains access to mucosal surfaces How about the skin? (The virus can enter the body through broken skin or unprotected mucous membranes in, for example, the eyes, nose, or mouth) Contact with infected animals Direct contact with body fluids Hand-to-eye contact. Inhalation of aerosol particles? Sexual transmission!  Single cell infection: Target cells Monocytes, Macrophages, Dendritic cells, Hepatocytes (liver cells), Endothelial cells, and Epithelial cells. Volume 12, Issue 5, May 2006, Pages 206–215  Cellular receptors 1. C-type lectins: such as DC-SIGN or L-SIGN, the hepatic asialoglycoprotein receptor. Act as attachment factors to concentrate Ebola virus particles at the cell surface Facilitate interaction with the receptor TIM-1 2. TIM-1 “T-cell immunoglobulin and mucin domain 1” expressed on a number of mucosal epithelial surfaces 3. Axl receptor “Tyrosine-protein kinase receptor” promote virus particle uptake via macropinocytosis. Critically, Ebola virus does not directly engage Axl 4. Niemann–Pick C1 (NPC1): a cholesterol transporter protein a putative endosomal receptor J. Cell Biol. Vol. 195 No. 7: 1071–1082  Single cell infection: Virus replication Attachment: GP binds to TIM-1 Host DC-SIGN and DC-SIGNR play a role in virion attachment Entry: Receptors mediated endocytosis (or Macropinocytosis mediated by binding of GP to Axl) Fusion: (Within the late endosome/lysosome) GP1 undergoes sequential proteolytic cleavage by cathepsins L and B GP1 binds to NPC1 (and low pH) Exposure of GP2 Fusion of virus membrane with the endosome Release of nucleocapsid http://www.operonlabs.com/?q=node/7  Single cell infection: Virus replication Genome replication: RNA dep RNA pol carried within the virion +ssRNA is synthesized (mRNA) Translation: Viral mRNA is translated using host ribosomes Viral proteins are processed including the release of sGP from the cell. Genome replication (continue): +ssRNA is used as a template for the synthesis of new genomic (-)ssRNA  Single cell infection: Virus replication Assembly: new genomic (-)ssRNA, which is rapidly encapsidated. Budding: Nucleocapsid interacts with the matrix protein, and envelope proteins. virus buds from the plasma membrane, budding is associated with cytopathic effect.  Virus-Host interaction: Anti-viral immunity Successful control of any viral infection requires a concerted action of both innate and adaptive immune responses –Control virus spread –Eliminate virus-infected cells Innate immunity: Early, rapid responses, but limited & ‘non-specifc’ Adaptive (acquired) immunity: Take time but powerful - ‘specificity + memory’ Humoral Immunity (B cell responses or Antibody response) Cell-mediated immunity (Cytotoxic T cell response) Remember, Antiviral immunity causes most of the clinical symptoms following viral infection: Fever, aches, pains, nausea, diarrhea, coughing, sneezing, inflammation, etc.  Detection of virus infection and the induction of IFN-I Two types of pattern recognition receptors (PRR) recognizing broadly shared molecules among pathogens, which are distinguishable from host molecules, collectively referred to as pathogen-associated molecular patterns (PAMPs) The Cytosolic Receptors (CRs) The Toll-Like Receptors (TLRs) Ebola virus pathogenesis and host immune responses 1. Evading innate immune responses: Inhibiting IFN-I responses Inhibiting signalling pathways related to Cytosolic receptors Inhibiting Jak-Stat signalling pathway Inhibiting ISGs 2. Evading Ab responses Secretory GP (sGP) to decoy Ab responses 3. Enhancement of infection 1. Evading innate immune responses: Inhibiting IFN-I responses Inhibiting signalling pathways related to Cytosolic receptors VP35 targets VP35 protein suppresses the activation of RIG-I and prevents induction of downstream Interferon genes. VP35 also targets IKKε, TBK1, IPS- 1, and TRAF3. All these host proteins are downstream signals of RIG-I. 1. Evading innate immune responses: Inhibiting IFN-I responses Inhibiting Jak-Stat signalling pathway (interferon signaling pathway) VP24 blocks transcription factors like STAT1 that regulate transcription of the immune system genes http://viralzone.expasy.org/all_by_protein/883.html 1. Evading innate immune responses: Inhibiting IFN-I responses Inhibiting ISGs VP35 protein suppresses the activation of PKR The crucial role of PKR in the antiviral response: dsRNA structures (virus replication or gene transcripts) activate PKR by autophosphorylation. Activated PKR then catalyzes the phosphorylation of eIF2a at serine 51 (inactivation of eIF2a). This leads to inhibition of translational and induction of apoptosis. The crucial importance of PKR in the antiviral response is highlighted by the ability of virus-encoded proteins to inhibit all stages of PKR activation and functionality 2. Evading Ab responses sGP to decoy Ab responses Three proteins of different sizes are coded by the GP gene through transcriptional editing. the full-length 676-residue surface glycoprotein (GP1,2) the 364-residue presecreted glycoprotein (pre-sGP) the 298-residue small secreted glycoprotein (ssGP) Marc-Antoine de La Vega er al., VIRAL IMMUNOLOGY, 2015, Volume 28 (1): 3–9 DOI: 10.1089/vim.2014.0068 Research Center for Zoonosis Control, Hokkaido Universty: http://www.czc.hokudai.ac.jp/epidemiol/research/ebola2e_L.jpg 3. Enhancement of infection It is important to consider the following: I: Cellular receptors 1. C-type lectins: Attachment 2. TIM-1: Entry 3. Axl receptor: Entry 4. Niemann–Pick C1 (NPC1): Uncoating II: Virus structure: 1. The structure of GP (Fusion loop) 2. The number of GP J. Cell Biol. Vol. 195 No. 7: 1071–1082 III: Other receptors: (attachment and entry) FCR, and Complement receptors 3. Enhancement of infection Antibody-dependent enhancement (ADE) 1.FcR Host Abs facilitate or enhance the virus’s attachment to the host cells Cells expressing Fc-receptors include: Macrophages, dendritic cells, neutrophils and others 2. Complement pathway C1q component of the complement system binds to the Ab-GP complex. Many white blood cells express complement receptors on their surface, particularly monocytes and macrophages. Research Center for Zoonosis Control, Hokkaido Universty: http://www.czc.hokudai.ac.jp/epidemiol/research/ebola2e_L.jpg http://www.czc.hokudai.ac.jp/epidemiol/research/ebola2e_L.jpg  Pathogenesis of Ebola virus infection: Systemic infection Monocytes, macrophages, dendritic cells, hepatocytes (liver cells), endothelial cells, and epithelial cells. 4 1 The liver produces coagulation factors 5 I (fibrinogen), II (prothrombin), V, VII, VIII, IX, X and XI, as well as 3 protein C, protein S and antithrombin. 2 7 6 8 http://thecelestialconvergence.blogspot.com.au/2014/03/plagues-pestilences-deadly-ebola-virus.html  Sullivan N et al. J. Virol. 2003;77:9733-9737 Direct infection of monocytes and macrophages: release of cytokines associated with inflammation and fever. Infection of endothelial cells: cytopathic effect and damage to the endothelial barrier. Cytokine dysregulation and endothelial cell infection loss of vascular integrity and hemorrhage Clinical symptoms  Control of Ebola virus infection Surveillance Quarantine Personal care (masks, health care,….) Vaccination?  http://neemnet.blogspot.com.au/2014/08/ebola-virus- preventiontreatment-etc.html If you travel to or are in an area affected by an Ebola outbreak, make sure to do the following: Practice careful hygiene. For example, wash your hands and avoid contact with blood and body fluids (such as urine, feces, saliva, sweat, urine, vomit, breast milk, semen, and vaginal fluids). Do not handle items that may have come in contact with an infected person’s blood or body fluids (such as clothes, bedding, needles, and medical equipment). Avoid funeral or burial rituals that require handling the body of someone who has died from Ebola. Avoid contact with bats and nonhuman primates or blood, fluids, and raw meat. Avoid facilities in West Africa where Ebola patients are being treated. Avoid contact with semen from a man who has had Ebola until you know Ebola is gone from his semen. After you return, monitor your health for 21 days and seek medical care immediately if you develop symptoms of Ebola.  http://www.mirror.co.uk/news/world- news/ebola-virus-outbreak-doctors-say- http://www.valuewalk.com/2014/05/ebola- 3829640 virus-outbreak/ Healthcare workers who may be exposed to people with Ebola should follow these steps: 1. Wear appropriate personal protective equipment (PPE). 2. Practice proper infection control and sterilization measures. 3. Isolate patients with Ebola from other patients. 4. Avoid direct, unprotected contact with the bodies of people who have died from Ebola. 5. Notify health officials if you have had direct contact with the blood or body fluids, such as but not limited to, feces, saliva, urine, vomit, and semen of a person who is sick with Ebola.