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What are Viruses? Obligate intracellular parasites Viral components – Nucleic acids – Capsid – Envelope 1 Viral Shapes and Sizes Helical Icosahedral 2 Infectious Properties Viral Host range Viral specificity Viral Origins 3 RNA Viruses Chromosomal Arrangements – + (sense) strand – – (antisense) strand – Double + strand 4 11 RNA virus families - *viridae Picornaviridae + strand RNA virus – 3 Genera: – Enterovirus – Hepatovirus – Rhinovirus 5 RNA Virus Families (cont.) Retroviridae (Two + RNA strands) – uses ____________________ – ds DNA ____________ – Inserted into host DNA • Include many tumor viruses • HIV – Enveloped viruses 6 RNA Virus Families (cont.) Rhabdoviridae - strand RNA virus – RNA dependent RNA polymerase makes a sense strand for mRNA – Includes _________ virus Reoviridae – ds RNA – Non-enveloped – Cause respiratory and intestinal infections in adults – Severe diarrhea in infants caused by Rotavirus – Animals may be affected by some members 7 DNA Virus Families Adenoviridae – Cause many “colds” – Highly stable over pH and temperature changes – 10-30% of infant diarrhea – Infection may be associated with a rash Herpesviridae – ds DNA virus – > 100 species – Latent viruses 8 DNA Virus Families (cont.) Papovaviridae – Cause skin and genital warts – 13 papilloma viruses are associated with cervical cancer – ____________ vaccine Parvoviridae – Ss DNA viruses – Unrelated viruses or host genes needed to allow replication – Human disease known as 5th disease (Erythrovirus) – Canine Parvovirus gastroenteritis – Dependovirus genus must be assoc. with Adenovirus or Herpesvirus for replication, no human diseases 9 Emerging Viruses Considerations: – – – – Reservoirs in animal populations Vectors Mutation/Recombination frequencies Immunity vs. containment (after rapid air travel of incubating patients) 10 Viral Replication Activities – Adsorption – Penetration (virus or chromosome) – Synthesis – Maturation/Assembly – Release 11 Animal DNA Viruses Virus is adsorbed/fuses to plasma membrane Uncoated DNA travels to nucleus, replicated and transcribed mRNA translated in cytoplasm – Capsid proteins return to nucleus for assembly of virions – Envelope proteins travel to plasma membrane 12 Animal Viruses RNA viruses Retroviruses 13 Culturing Animal Viruses Live animals Eggs 14 Culturing Animal Viruses Cell Culture – Primary – Continuous 15 Viral Cytopathic Effects Cytopathy Teratogenic effects – CMV, HSV-1, Rubella – TORCH series (T_______, O________ like Chicken pox and Hepatitis B, R_______, C___, H_____ 16 Viruses and Cancer Mechanism of cancer causation – Triggering of rapid uncontrolled cell division – Oncogenes (may be carried by DNA cancer viruses) – Proto-oncogenes (part of human genome) 17 Cancer causing viruses Adenoviridae Papovaviridae Hepadnaviridae Herpesviridae Retroviridae 18