Viruses Lecture Notes PDF

Viruses Biomedical science Benjamin Tighe  Intended Learning Outcomes By the end of this sessions students should be able to: Be familiar with the structure and classification of viruses Outline the features of HIV, hepatitis B virus, varicella zoster virus, herpes. and inf...

Viruses Biomedical science Benjamin Tighe  Intended Learning Outcomes By the end of this sessions students should be able to: Be familiar with the structure and classification of viruses Outline the features of HIV, hepatitis B virus, varicella zoster virus, herpes. and influenza viruses according to their symmetry and nucleic classification. Identify dentally relevant viruses and link with their disease. Understand the concept of viral tropism. Outline how viruses replicate and spread within the host. Explain the terms viral persistence & viral latency Explain the structural features and relevance of prions  than bacteria · smaller itself so unable to replicate Features of a virus · It infects host. cells An infectious particle that reproduces by "commandeering" a host cell and using its machinery to make more viruses. Made up of a DNA or RNA genome inside a protein shell called a capsid. Loading… Some viruses have an external membrane envelope. Come in different shapes and structures, have different kinds of genomes, and infect different hosts. Viruses reproduce by infecting their host cells and reprogramming them to become virus-making "factories."  DNA or RNA either. Genome - Contac Type of Two · or virus Virus Did virus. RNA · Viral Genome may or of linear Consist DNA or Circula , or straded DNA Single Linear RNA.  Protection Genome Capsid - outer Layer of virus. nucli acid Loading… surrounds viral · helps introduce into host genomes alls. normal cell. · Stickanto  to symmetry Genome gives virus - up of Capsid made - together capmiser Tightly. capsid. to form Envelope - some certain envelopes. virus  Genome Capsid Envelope Enzymes -. some virus contain enzymes which place central roll during infection process. Further facts Small Size 10-100nm – 1/10 of bacteria Genome RNA or DNA (never both) Obligate intracellular parasites – viruses can only multiply in a living host cell Key structures of Viruses (complete the table in your virus Workbook) - Attached at end of slides. Viral Capsid Nucleocapsid nucleic acid Viral Envelope protein Classification of Viruses symmetry. · cassited by Classification Symmetry Nucleic acid Loading… Structure of Viruses Virus of symmetry  Symmetry Icosahedral Polygane · equaltric · 12 corners * triangle. · 20 faces/facets · 30 edges human Stable found in · most viruses, eg hopes Pathogenic types Pentegas/hexegas. · 2  · Liner thin rad shaped. Filamentous  between filamentous & Kosahadrea · Hybrid Head-tail. Nucleic acid DNA or RNA Viruses can have all possible combos of strandedness and nucleic acid type Double-stranded DNA Double-stranded RNA Single-stranded DNA Single-stranded RNA).  RNA viruses Viruses usually show much higher mutation rates than do the DNA viruses O DNA Virus Viruses and disease – please complete the below table which is in your workbook attached End of sides Virus Name Disease Picornavirus Astrovirus Calcivirus Togavirus Retrovirus Orthomyxovirus Outline the features of HIV, hepatitis B virus, varicella zoster virus influenza viruses and herpes according to their symmetry and nucleic classification end of slides. at the attached Common viruses relevant to dentistry Please complete activity in Virus workbook aeas attached We will be looking at these in more detail in Viral infections and Year 2  preceded of · cellular resets · influencing factors. · Avalibilty of transcription Viral Tropism · factes involved cello recepts of protein Viral tropism is the ability of a given virus to productively infect a particular cell (cellular tropism), tissue (tissue tropism) or host species (host tropism). affects als affect tissues Effects hust & · · How do they achieve the ability to be selective? Viral replication and dissemination Q Adsorption For some viruses some steps are not so · obvious ↓. Penetration & Some may be merged or omitted ↓. uncoating/eclipse & Transcription ⑪ ↓. The period between infection and the production of the new virion (eclipse or latent ↓ Synthesis of components viral period) could be as short as 3 hours or as ⑳ long as several months o ↓ Assembly ↓ o Release G ① Adsorption Or attachment of the virus particle to the specific receptors of host cell Positive/firm attachment requires presence of receptors on host plasma membrane  Penetration ② The process by which the virus or its genome enter the host cell Penetration can happen by 1. Endocytosis 2. Fusion – direct fusion of viral envelope & host cell 3. Translocation – non enveloped virus pass directly through host membrane  Uncoating/eclipse ③ For a period after penetration there is a time the virus cannot be detected – pause in infectivity This ‘eclipse’ phase begins uncoating the lipid membrane & protein capsid surrounding nucleic core Viral nucleic acid becomes free and can act as template for mRNA  Transcription ④ The mRNA codes for the synthesis of enzymes needed to initiate early steps in viral replication The virus takes advantage of the existing cell structures to replicate itself e.g. integrating in the host DNA  Synthesis of viral components ⑤ Assembly ⑥ Synthesis of components Assembly Loading… Viral proteins are 2 types: Viral assembly is accomplished by incorporating nucleic acid into capsomeres 1. Structural 2. Non-structural – Assembly can occur in host enzymes nucleus, cytoplasm or at plasma membrane Components are built on · forced into cell naked replicated and Leaves. Release G Lytic replication – host cells dies - virus relases makes you feel unwell Lysogenic replication – host cell continues to live and function normally virus excapes. Viral Terms Viral Persistence Examples Persistent infections are characterized as those in which the HIV virus is not cleared but remains in specific cells of infected individuals. Epstein-Barr Human Cytomegalovirus Persistent infections may involve Human Herpesviruses 6 and 7 stages of both silent and productive Varicella-Zoster Virus infection without rapidly killing or Human Papovaviruses even producing excessive damage of the host cells. Hepatitis B Virus 31  herpes Simplex virus Viral Latency. eg Virus latency (or viral latency) is the ability of a pathogenic virus to lie dormant (latent) within a cell, denoted as the lysogenic part of the viral life cycle. A latent viral infection is a type of persistent viral infection which is distinguished from a chronic viral infection Recommended Reading Structure and Classification of Viruses - Medical Microbiology - NCBI Bookshelf (nih.gov) Medical Microbiology 4thed. Chapter 41Structure and Classification of Viruses Hans R. Gelderblom.  EASTMAN DENTAL HOSPITAL EDUCATION CENTRE DENTAL HYGIENE & DENTAL THERAPY Structure of Viruses Capsid Protein shell that protects the virus’s genetic material Made of units called capsomeres Made of protein Either helical or icosahedral Viral nucleic Linear polymer chains of nucleotides acid Single molecule of nucleic acid surrounded by a protein coat Can be DNA or RNA Can be single stranded or double Function involves storage and expression of genomic information Nucleocapsid Entire unit of nucleic acid surrounded by capsid Viral structure Generally inside the cytoplasm Envelope Protective layer that surrounds the genetic material Lipid membrane Source is host cell Viral protein The bulk of the virus is protein – capsid etc Surface proteins attract to specific receptors Some enzyme proteins 3 4 EASTMAN DENTAL HOSPITAL EDUCATION CENTRE DENTAL HYGIENE & DENTAL THERAPY Complete the following table Virus Name Disease Picornavirus Polio Hepatitis A The common cold Hand, Foot and mouth disease Aseptic meningitis Astrovirus Gastroenteritis Meningitis in children Calcivirus Norovirus Sapovirus Togavirus Rubella Sindbis virus Retrovirus HIV Orthomyxovirus Influenza A,B,C Paramyxovirus Measles  Mumps Croup Papillomavirus HPV Genital warts Epidermodysplasia verruciformis Adenovirus Common cold Gastrointestinal illnesses Pink eye conjunctivitis Coronavirus SARS MERS EASTMAN DENTAL HOSPITAL EDUCATION CENTRE DENTAL HYGIENE & DENTAL THERAPY Class Common Viruses relevant in dentistry Virus Disease / notes Symmetry Nucleic classification Human HIV immunodeficiency/AIDs Icosahedral RNA Leads to compromised immune system and opportunistic infection Targets specific CD4 T- lymphocytes cells Infection of the liver Icosahedral DNA Hepatitis  B Spread in blood and bodily fluids Chicken pox Icosahedral DNA Varicella Shingles Zoster Herpes simplex virus Icosahedral DNA Infection that causes Herpes painful blisters or ulcers Flu that’s easily Helical RNA spread Infection of the nose,throat and lungs Members of the Influenza orthomyxoviridae 6 EASTMAN DENTAL HOSPITAL EDUCATION CENTRE DENTAL HYGIENE & DENTAL THERAPY Write short notes on Prions Structure – long chains of amino acids and are twisted isoforms of the major prion protein Replication – they replicate through self generating mechanism that involves binding to and converting normal prion proteins into a pathogenic molecule. Transmission- can be transmitted by eating contaminated meat , exposure to contaminated equipment , oral exposure , blood products or transplant surgery Prevention and dental implications – can be transmitted in dental setting through contact of potentially infected tissue. Therefore to prevent this to reduce risk by using : single use items , sterilised instruments , checking medical history’