MONTGOMERY COUNTY COMMUNITY COLLEGE CHAPTER 13: VIRUSES I. CHARACTERISTICS OF VIRUSES A. General Characteristics 1. Obligate intracellular parasites that multiply in living host cells 2. Contain a single type of nucleic acid 3. Contain a protein coat that surrounds the nucleic acid 4. Not a cell B. Viral Structure 1. Virion: complete, fully developed viral particle composed of nucleic acid 2. Nucleic acid: or 3. Protein coat called a 4. Envelope chemical composition: 5. Accessory structures on some viruses C. Host Specificity 1. 2. P:\sci\je\Viruses 2009 1
D. Viral Size 1. Smaller than a bacteria 2. Can see only with an electron microscope E. General Morphology 1. Helical viruses: 2. Polyhedral viruses: isohedral 3. Complex viruses: F. Comparison of Bacteria and Viruses TABLE 13.1 A comparison of Viruses and Bacteria BACTERIA Typical Bacteria Rickettsias Chlamydias VIRUSES Intracellular parasite + + + Plasma membrane + + + Binary fission + + + Pass through bacteriological filters Process both DNA and RNA ATP-generating metabolism + + + + + + + Ribosomes + + + Sensitive to antibiotics + + + Sensitive to interferon + P:\sci\je\Viruses 2009 2
II. ISOLATION, CULTIVATION, AND IDENTIFICATION OF VIRUSES A. Virus must grow within living host cells instead of on chemical medium. 1. Bacteriophages are grown on bacterial cells plaque method 2. Animal viruses (including human viruses) use: a. living animals: b. embryonated eggs: c. cell culture lines: B. Viral Identification Methods 1. C.P.E. = 2. F.A. 3. Serology (antigen/antibody) 4. DNA/RNA Probe and other molecular methods 5. Electron microscopy: Reference Lab P:\sci\je\Viruses 2009 3
III. VIRAL TAXONOMY A. Family ends in B. Genus ends in C. Viral species designated by D. Subspecies designated by E. Example: Herpesviridae Simplexvirus Human Herpes Virus 1, 2, 3,4,5,6 IV. VIRAL MULTIPLICATION A virus must invade the host cell in order to multiply and grow virus takes over the metabolism of host cell to make viral enzymes and components. A. Bacteriophages 1. T-even Bacteriophage: The Lytic Cycle Type of nucleic acid is: a. attachment b. penetration (entry) c. biosynthesis (replication) d. maturation e. release lytic (lyses cell) - burst time: - burst size: P:\sci\je\Viruses 2009 4
2. Bacteriophage Lambda: The Lysogenic Cycle Nucleic Acid is a. Lysogeny: A state in which is incorporated into the host cell without. b. Lysogenic Cycle: c. Prophage: Phage DNA 3. Specialized Transduction a. prophage excised b. prophage carries c. bacteriophage infects a new bacterial cell d. prophage now transfers genetic material (new genes) sometimes for bacterial toxins 4. Viral Mutation P:\sci\je\Viruses 2009 5
B. Animal Viruses (Human Viruses) 1. Replication a. attachment b. penetration c. uncoating d. biosynthesis e. maturation f. release V. EXAMPLES OF HUMAN VIRUSES A. DNA Non-Enveloped Viruses 1. Papovaviridiae (Family) Papillomavirus (Genus) a. type of disease c. CPE d. treatment d. latency P:\sci\je\Viruses 2009 6
2. Human Papilloma Virus HPV a. type of disease chronic disease c. CPE d. treatment e. latency B. Enveloped, DNA Viruses Replication cycle: C. Herpesviridiae (Family) 1. Herpes simplex-1 c. treatment d. latency recurrence e. diagnosis P:\sci\je\Viruses 2009 7
2. Herpes simplex-2 c. treatment d. latency recurrence e. diagnosis 3. Herpes Varicella-zoster c. treatment d. latency e. complications f. recurrence g. diagnosis 4. Epstein-Barr c. treatment d. latency e. diagnosis P:\sci\je\Viruses 2009 8
5. Cytomegalovirus (CMV) c. treatment d. latency e. recurrence f. diagnosis 6. Human Herpes Virus VI c. treatment d. diagnosis P:\sci\je\Viruses 2009 9
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D. RNA Human Viruses 1. Non-enveloped, RNA Rhinovirus c. treatment d. diagnosis 2. Coronavirus b. SARS c. treatment 3. Enveloped, RNA Influenza virus c. treatment d. prevention e. diagnosis f. shift vs. drift mutations g. Bird Flu: P:\sci\je\Viruses 2009 11
Health Services Health & Wellness Tip Is It a COLD or The FLU? Sometimes it can be hard to tell the difference between a simple cold and the more serious condition of the flu. They are similar in many ways, but the flu can lead to more serious illnesses. Below is a chart to help you determine the signs and symptoms of each. Symptoms Cold Flu Fever Rare Characteristic, high (102-104 F), lasts 3-4 days Headache Rare Prominent General Aches, Slight Usual; often severe Pains Fatigue, Weakness Quite Mild Can last up to 2-3 weeks Extreme Exhaustion Never Early and prominent Stuffy Nose Common Sometimes Sneezing Usual Sometimes Sore Throat Common Sometimes Chest Discomfort, Cough Complications Mild to moderate; hacking cough Sinus congestion or earache Common; can become severe Bronchitis; pneumonia; can be life threatening Prevention None Annual vaccination; antiviral medicines see your physician Treatment Only temporary relief of symptoms Antiviral medicines see your physician Adapted from: National Institute of Allergy and Infectious Diseases. 3/30/04 GAS P:\sci\je\Viruses 2009 12
4. Enveloped, RNA virus Human Immunodeficiency Virus b. the organism Acquired Immunodeficiency Syndrome (AIDS) HIV Infection Reverse transcriptase Capsid DNA Virus Two identical + stands of RNA Identical strands of RNA Viral proteins RNA 4 5 Mature retrovirus leaves host cell, acquiring an envelope as it buds out. Transcription of the provirus may also occur, producing RNA for new retrovirus genomes and RNA that codes for the retrovirus capsid and envelope proteins. Provirus Host cell Reverse transcriptase Viral RNA 1 Retrovirus penetrates host cell. DNA of one of the host cell s chromosomes 3 2 Virion penetrates cell and its DNA is uncoated The new viral DNA is tranported into the host cell s nucleus and integrated as a provirus. The provirus may divide indefinitely with the host cell DNA. Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 19.12a Copyright 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.19 c. route of transmission d. prevention e. informed consent for testing f. lab diagnosis P:\sci\je\Viruses 2009 13
VI. PRIONS A. Definition: B. Examples 1. Spongiform Encephalopathy Creutzfeldt-Jacob Disease (CJD) 2. Bovine Spongiform Encephalopathy (BSE) or Mad Cow Disease VII. TREATMENT OF VIRUSES A. Analogs Acyclovir AZT B. Other Anti-Virals Amantadine P:\sci\je\Viruses 2009 14
VIRUSES ORGANISM DISEASE TRANS- MISSION COMMENTS SYMPTOMS DIAGNOSIS TREATMENT DNA ds Papovaviridae Papillomavirus Human wart virus Non-enveloped Human Papillomavirus HPV Genital warts DNA ds Herpesviridiae Herpes simplex 1 Cold sores Enveloped Herpes simples 2 Genital Herpes P:\sci\je\Viruses 2009 15
ORGANISM Herpesviridiae Varicellavirus DISEASE Chickenpox VIRUSES TRANS- MISSION COMMENTS SYMPTOMS DIAGNOSIS TREATMENT Varicellavirus Shingles Re-emergence Cytomegalovirus CMV Bladder Pneumoniae Kidneys Epstein-Barr virus EBV Mononucleosis P:\sci\je\Viruses 2009 16
ORGANISM Herpesviridiae Human Herpes-6 HHV-6 DISEASE Roseola VIRUSES TRANS- MISSION COMMENTS SYMPTOMS DIAGNOSIS TREATMENT RNA ss Picornaviridiae Rhinovirus Colds Coronaviridiae Coronavirus SARS Colds RNA ss Orthamyxaviridiae Influenzavirus The Flu P:\sci\je\Viruses 2009 17
ORGANISM RNA Picornaviridae Hepatitis A virus DISEASE VIRUSES DISEASE HEPATITIS TRANS- MISSION COMMENTS SYMPTOMS DIAGNOSIS TREATMENT Flaviviridae Hepatitis C virus Deltaviridae Hepatitis D virus DNA ds Hepadnaviridae Hepatitis B virus RNA Retroviridae Lentivirus HIV AIDS P:\sci\je\Viruses 2009 18