VMED280: Infection And Immunity II - Virology - PDF

VMED280: Infection and Immunity II Introduction to Virology: Classification, Structure, Molecular Architecture  Learning Objectives How is virus different Properties of viruses than bacterial , – Structure –...

VMED280: Infection and Immunity II Introduction to Virology: Classification, Structure, Molecular Architecture  Learning Objectives How is virus different Properties of viruses than bacterial , – Structure – Classification – Properties History of viral diseases where aware there is people a disease Loading… Pock marks indicative of smallpox 1500 BC: Leg deformities indicative of poliomyelitis  enveloped" L surrounded e rate by membrane tructure S7 surrounded S Not... ~ ↑ gree A virus is: ~either A package of genetic information protected by a protein shell for delivery into a host cell to be expressed and replicated "Virus" is from the Greek meaning for "poison” and was initially described by Edward Jenner in 1798  Properties of Viruses Viruses grow by independent synthesis and assembly of their components Loading… inside of a host cell Human adenoviruses growing in the nucleus of their host cell  -taket enveloped Viruses ↳ transcribe very quick can fragmented : ~ some are Have DNA or RNA genomes Metabolically inert – Replicate only after infection of host cell – Parasitize the host machinery for transcribe and/or translate genes – Obligate intracellular parasites Viral particle (virion) – Naked or enveloped Envelope is usually from host cell origin The comparative sizes of representative viruses  Properties of Viruses seen under emicrosape Small size range: 30nm – 400 nm Picornavirus (“little RNA virus”) is one of the smallest viruses, about 20 nanometers in diameter Smallpox virus, one of the largest viruses, about 300 nanometers, near the resolution of the light microscope Viral diseases have played a major role in human history Biggest cause of mortality. Over the past 1000 years: Smallpox and measles Over the past 100 years: Spanish flu, HIV Over the past 10 years: West Nile, SARS, Avian Flu  Virus naming and classification & *I !' S D. Usually based on data available at the igJ 91110 ~ - time of discovery: & dist si , D = I Disease they are associated with – HIV, Measles Humen immunodifficiency virus · 2 Cytopathology they cause – Cytomegalovirus ?J 3 Site of isolation – Adenovirus, Enterovirus, Rhinovirus 4 Places discovered or people that discovered them – Epstein-Barr virus, West Nile Fever S Biochemical features – Retrovirus Respiratory opportunistic Syncytial Virus (RSV)  Viral taxonomy Viral classification is based upon: Rotaviru – Shape s " – Type and form of nucleic – acid Loading… Enveloped or naked – i Mode of replication – Organization of the genome and antigenic differences  Genomic organization Viral nucleic acids RNA viruses – RNA single stranded positive polarity negative polarity – RNA double stranded one piece segmented DNA viruses – single stranded – double stranded Symmetry and construction of the viral nucleocapsid Genome : single stranded (ss) or double stranded (ds) - linear or circular DNA or RNA Capsid: made up of protein capsomeres Nucleocapsid: capsid + genome - symmetry: icosahedral, helical or complex  Viral structure caspid represent - Capsomeres are structural subunits containing several proteins Capsomeres aggregate to produce the viral capsid. The viral capsid associates with the viral nucleic acid to produce a nucleocapsid Nucleocapsids are usually arranged in one of three ways – cubic, eg. icosahedral (Herpes viruses) – helical (Influenza viruses) – complex  Construction of an enveloped virus ↳ survive longer time Naked viruses: more resistant in the outside environment Enveloped viruses: less resistant to environment ↳ need to infect reinfect quickly , Do not Survive unte (Hot) conditions - influence ways viruses are transmitted  Viral structure (cont’d) Lipid envelopes are derived from Hest from cellular membranes Studded with surface projections: (spikes or peplomers). These are usually glysosylated by host systems prior to make them “sticky” The origin of Velcro?  Properties of Viruses Various morphologies – Polyhedral – Helical – Spherical – Filamentous – complex Ebola virus Rabies virus Polioviru Herpes virus Coronavirus Lassa virus s  Structure of Viruses virenee ↑ out embra e -inner Classification of Viruses Comparative size and shape of various groups of viruses representing diversity of form and host range How are viruses classified ? Hierarchical virus classification: (order) Family - subfamily - genus - species - strain/type All families have the suffix viridae, e.g Herpesviridae Genera have the suffix virus. For instance Coxsackie virus  Some representative DNA viruses DNA Icosahedral Comple x Naked Enveloped Papilloma S Herpes viruses 2 Hepatitis B Pox ! Parvovirus Adenoviruse viruses s Cytomegaloviru 2 Hs erpes simplex 1 and Varicella Zoster 2 is Epstein Barr HHV 6- Virus 8  Some representative RNA viruses RNA Icosahedral Helical Naked Enveloped Enveloped Picornaviruses Influenza Retroviruses Flaviviruses Paramyxoviruses HIV Hepatitis C Enteroviruses Rhinoviruses Hepatitis A Coxsackie viruses Echo virus Polio virus Routes by which viruses enter the body Most common: via inhaled droplets (e.g. rhinovirus) In food or water (e.g. hepatitis A) By direct transfer from other hosts (e.g. HIV) Bites of vector arthropods (e.g. yellow fever)  How do you acquire these viral infections? – Direct personal contact Herpes viruses, HIV, Influenza ⑧ Airborne spread – Chicken pox Parenteral – HIV, Hepatitis B and C, cytomegalovirus (CMV) Fomites – Enteroviruses and other sturdy drying resistant viruses Vectors – West Nile Vertical transmission – HIV, Herpes simplex, cytomegalovirus, rubella (German measles) Enteral (foodborne) – Hepatitis A, gastroenteritis viruses Stages in the infection of a host's cell and replication gut ready of a virus. to infect Re B - - each genome surrounded by its get rit sule & · blanket Stucket coment Several thousand virus particles may be formed from each cell Release of enveloped RNA virus by budding through host cell membrane. Influenza A virus is -Fructure surerareof shown in this example. ~ Hest AENA I. Aciabr  Consequences of virus-cell interaction 75% of Cancer Viral proliferation and cell lysis can be induced – Cold sores, genital herpes,chicken pox from virus Latent infection (non replicating virus) – Most Herpes viruses, Human papilloma viruses – Viral genome may be integrated or not Persistent infection (ongoing viral replication, few or no symptoms) – Hepatitis C and B, HIV – Tissue injury may be induced by the virus or the immune response to the viral infection Oncogenesis (cellular proliferation) – Human papilloma virus, EBV No apparent disease – eg Hepatitis G  Diagnosis of viral infections Clinical features typical of infection Laboratory diagnosis – Histology and cytology – Direct examination by electron microscopy – Examination looking for viral antigens In tissue In serum – Antibody testing (rising IgG, IgM, very high titre IgG, any IgG) – Virus isolation – DNA or RNA amplification (in tissue sections, from tissue, in serum and fluids) production for antibodies Elisa-see for. ↓ Digestion of those viruses “Owl’s Eye” Inclusion of Cytomegalovirus (CMV) in Lung Tissue Loading… ④ work DDCR-RNA virus PRR-NA Virus Electron Micrograph of Herpes Simplex Virus type 1 (HSV-1)  varicella-zoster virus A4 acquiring its lipid envelope by budding through nuclear membrane (bar: 0.1µm) where it but of E takeMembere Parainfluenza virus acquiring its lipid envelope by budding through plasma membrane (bar: 0.1µm) Molecules used by viruses in attaching to host cells Host specificity determined by ability of virus to attach to host cells bind to interaction with host receptor molecule evry virus have its own receptor. evry host receptor virulence factor would be Siffer  Once in host cytoplasm the virus is no longer infective acquired capsin get out - infective. On fusion or uptake into a phagosome, the virus particle is carried into the cytoplasm across the plasma membrane. envelope and/or capsid are shed and the viral nucleic acids released. The virus is now no longer infective: Called the ‘eclipse phase’  influenza Translation and cleavage of viral proteins from messenger RNA (mRNA). Host nucleic transcription - acid I translation-protin I Depend on Host Oncogenes, gene products, viruses known to carry them, and associated animal diseases. (ALV/FeLV/MuLV, avian, feline and murine leukemia viruses; GTP, guanosine triphosphate.) viruses make product where it would carbe cancell.  ~remember Some Families of Animal Viruses Not asked in exam - but if a write it u get Extra mark Some Families of Animal Viruses (continued)  host resort Keys facts · Depend cell on to increate number Viruses have RNA or DNA but are absolutely dependent upon the host to process their genetic information into new X d virus particles. RNA CRNA The outer surface of a virus (capsid or - envelope) is essential for host cell contact 5 and entry and determines the capacity to survive in the outside world. infact important to.  Keys facts 2 · transmition important Viruses are most often transmitted in use droplets or in food and water. it macrophage carrieras. Replication of viral RNA or DNA is a up out kill Then complex process, making use of hostinfect and/or viral enzymes. virus different microphage Same use - receptor RNA of retroviruses becomes integrated HiUbindto IDY infect CP4 into the host genome. 1 them - 1:. New virus particles are released by cell lysis or by budding through the host cell ↳ballons with plasma structure membrane. surrounded what can cause furthe infection. Put me ofdisease  integrate in genome thencomeone epprises Keys facts 3 HiV1(macrophage) actiquate d ~ & er some Some viruses may become latent and of people - - require a trigger to resume replication; "carrier" latent Active others replicate at a slow rate, persisting L as a source of infection in symptomless Si d 855 carriers. - 88 - ↳ Active Phase & A number viruses transform the host cell, by interfering with normal cellular regulation, resulting in the development of a cancer cell. This may be the result of the activity of viral or cellular oncogenes. virus can be cancer causing.