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I. What is a virus? A. A virus is a set of genes, either DNA or RNA, packaged in

Micro 615 Principals of Virology: Virus Structure, Classification, Detection & Persistence Alice Telesnitsky. I. What is a virus? A. A virus is a set of genes, either DNA or RNA, packaged in a protein-containing coat

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I. What is a virus? A. A virus is a set of genes, either DNA or RNA, packaged in

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  1. Micro 615Principals of Virology:Virus Structure, Classification, Detection & PersistenceAlice Telesnitsky

  2. I. What is a virus? A. A virus is a set of genes, either DNA or RNA, packaged in a protein-containing coat B. Viruses are obligate intracellular parasites capable of directing their own replication viruses are small

  3. II. Examples of how viral infections are important in many A. Viruses cause diseases

  4. HIV infection may become a common chronic condition

  5. B. Can replicate in some humans without causing disease 1. Asymptomatic carriers with inapparent (subclinical) infection can transmit viral disease PolioInapparent infection in 90-95%Abortive infection in 4-8%Major CNS involvement in 1-2%

  6. B. Can replicate in some humans without causing disease, cont. 2. Viruses serve as co-factors for some diseasesC. Significant in initiating disease in aging, immune-deficient (eg: transplant recipients) and other at-risk populationsD. Virus-related entities such as endogenous retroelements 1. A significant portion of the human genome 2. Endogenous viruses can be mutagens and are a potential problem in xenograftsE. Emerging viruses

  7. III. Structural features of human viruses: from the inside outA. GenomesB. CapsidsC. With or without envelopA virus is a set of genes, either DNA or RNA, packaged in a protein-containing coat

  8. A. Genomes 1. RNA or DNA; single- or double-stranded; one or several segments 2. Small genomes--limited coding capacityB. Capsid morphologies 1. Helical Helical rods of a plant virus

  9. Rabies: an enveloped helical virus Cartoon of rabies Rabies virus

  10. 2. Cubic---Icosahedral20 triangular faces, 12 vertices adenovirus 3. Other example: “bullet-shaped” capsid of HIV

  11. C. Exterior surface1. Naked or enveloped 2. Physical properties affect transmission

  12. IV. Virus classification influenza HIV polio small

  13. DNA viruses large small

  14. V. Assay and detection of viruses and their replication“viruses are obligate intracellular pathogens” A. Virus culture 1. Animals (or plants, bacteria, etc) 2. Tissue culture

  15. B. Assays and detection • 1. Plaque assay • a. End point dilution • b. Plaque forming units (PFU) • 2. Agglutination • 3. Infectivity eg: LD50 • 4. Cytopathic effect (CPE) syncytia

  16. 4. Other ways of measuring virus a. Count particles by electron microscopeViruses differ in infectious units per biochemical unit

  17. VI. General types of viral infectionsA. Acute clinical disease1. Localized virus replication at site of infection2. Disseminated spread to and replication in secondary sitesB. Persistent infections on organism level1. Chronic infectionseg: acute phase disease followed by “smoldering infection” sometimes seen for adenovirus2. Latent infections eg: herpes3. Others

  18. C. Viral persistence on cellular level

  19. VII. Biology of herpes virusesA. Biology1. Large enveloped DNA viruses 2. Possess many genes 3. Replication involves acute and latent phasesB. Human infection by Herpes simplex virus I 1. Acute phase disease 2. Latency a. Physiology of virus and of cell during latency b. Immune response avoidance 3. Reactivation

  20. C. Other human Herpes viruses1.HSV-II 2. Varicella-Zoster (VSV) Chicken pox and shingles 3. Cytomegalovirus (CMV) a. Epidemiology b. Prenatal infection c. Transplant mortality

  21. 4. Epstein Barr virus a. Discovery and association with Burkitt's lymphoma Environmental cofactors? b. Primary infection (mononucleosis) c. Association with other malignancies5. HHV-6 (roseola); HHV-76. Kaposi's Sarcoma Herpes Virus (KSHV)/HHV-8 a. Epidemiology and prevalence HIV an environmental co-factor b. Primary disease unknown

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