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Viruses: Bacterial and Animal Types

Viruses: Bacterial and Animal Types. Animal Viruses DNA vs RNA animal viruses Differences in replicating viral genome both ss and ds DNA & RNA forms DNA Viruses (E.g. smallpox, warts, tumors, herpes, colds) Life Cycle Attachment, penetration, (uncoating)

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Viruses: Bacterial and Animal Types

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  1. Viruses: Bacterial and Animal Types • Animal Viruses • DNA vs RNA animal viruses • Differences in replicating viral genome • both ss and ds DNA & RNA forms • DNA Viruses (E.g. smallpox, warts, tumors, herpes, colds) • Life Cycle • Attachment, penetration, (uncoating) • Replication of DNA in nucleus of host • Assembly in nucleus • Lysis from nucleus and plasma membrane • RNA Viruses (E.g... Polio, rabies, hepatitis, influenza, AIDS) • Life Cycle of RNA->RNA viruses • Attachment, penetration, (uncoating) • Replication of RNA to RNA in cytoplasm • Assembly in cytoplasm, then lysis • Retroviruses (HIV) • Types of Infections: Latent (herpes, shingles), slow (encephalitis), prions (kuru, CJD) • Oncogenesis • 15% of cancers are virally causes (e.g. EBV (mononucleosis), HIV, papovaviruses-warts) • Carcinogenic agents: mutagens, radiation, viruses • Cancer cell characteristics (contact inhibition loss, chromosome number) Figure 13.1

  2. Multiplication of Animal viruses • Attachment Viruses attaches to cell membrane • Penetration By endocytosis or fusion • Uncoating By viral or host enzymes • Biosynthesis Production of nucleic acid and proteins • Maturation Nucleic acid and capsid proteins assemble • Release By budding (enveloped viruses) or rupture Having an RNA genome means transcription may not be necessary but an RNA-dependent RNA polymerase must be provided for replication.

  3. Release of an enveloped virus by budding Figure 13.20

  4. Viruses: Bacterial and Animal Types • Animal Viruses • DNA vs RNA animal viruses • Differences in replicating viral genome • both ss and ds DNA & RNA forms • DNA Viruses (E.g. smallpox, warts, tumors, herpes, colds) • Life Cycle • Attachment, penetration, (uncoating) • Replication of DNA in nucleus of host • Assembly in nucleus • Lysis from nucleus and plasma membrane • RNA Viruses (E.g... Polio, rabies, hepatitis, influenza, AIDS) • Life Cycle of RNA->RNA viruses • Attachment, penetration, (uncoating) • Replication of RNA to RNA in cytoplasm • Assembly in cytoplasm, then lysis • Types of Infections: Latent (herpes, shingles), slow (encephalitis), prions (kuru, CJD) • Oncogenesis • 15% of cancers are virally causes (e.g. EBV (mononucleosis), HIV, papovaviruses-warts) • Carcinogenic agents: mutagens, radiation, viruses • Cancer cell characteristics (contact inhibition loss, chromosome number) • Bacterial viruses sometimes can lie dormant inside of cells. DNA animal viruses reproduce in the nucleus • while RNA viruses reproduce in the cytoplasm. Figure 13.1

  5. Multiplication of DNA Virus Papovavirus 1 Virion attaches to host cell 7 Virions are released Host cell DNA Capsid 2 DNA Virion penetrates cell and its DNA is uncoated Cytoplasm 6 Virions mature Capsid proteins mRNA 5 Late translation; capsid proteins are synthesized 3 Early transcription and translation; enzymes are synthesized 4 Late transcription; DNA is replicated Figure 13.15

  6. Single/Double-stranded DNA, nonenveloped viruses • Parvovirus • Fifths Disease • Tumors • Cancers • Warts • Hepatitis C • Smallpox • Cowpox • Herpes simplex cold sores • Genital herpes • Kaposi’s sarcoma Know the names of some DNA viruses

  7. Viruses: Bacterial and Animal Types • Animal Viruses • DNA vs RNA animal viruses • Differences in replicating viral genome • both ss and ds DNA & RNA forms • DNA Viruses (E.g. smallpox, warts, tumors, herpes, colds) • Life Cycle • Attachment, penetration, (uncoating) • Replication of DNA in nucleus of host • Assembly in nucleus • Lysis from nucleus and plasma membrane • RNA Viruses (E.g. Polio, rabies, hepatitis, influenza, AIDS) • Life Cycle of RNA->RNA viruses • Attachment, penetration, (uncoating) • Replication of RNA to RNA in cytoplasm • Assembly in cytoplasm, then lysis • Retroviruses • Types of Infections: Latent (herpes, shingles), slow (encephalitis), prions (kuru, CJD) • Oncogenesis • 15% of cancers are virally causes (e.g. EBV (mononucleosis), HIV, papovaviruses-warts) • Carcinogenic agents: mutagens, radiation, viruses • Cancer cell characteristics (contact inhibition loss, chromosome number) Figure 13.1

  8. Pathways of Multiplication for RNA-Containing Viruses Figure 13.17

  9. SS or DS RNA, +/- strand, enveloped/nonenveloped • Polio virus • Rhinovirus (colds) • Hepatitis A virus (vaccine) • Hepatitis E virus • Norwalk gastroenteritis • Mumps • Rubella virus • Measles • Yellow fever, dengue, and West Nile viruses • Hepatitis C virus Ebola & Marburg viruses • Respiratory infections Rabies virus • Hepatitis D virus, virulent • Influenza Know the names of some RNA viruses Hepadnaviridae Hepatitis B virus (esp. virulent, cirrhosis, cancer); used reverse transcription – (vaccine) Hanta virus Lassa fever Colorado tick fever

  10. Viruses Can Recombine Within Host Cells: E.g. Flu Virus

  11. Viruses: Bacterial and Animal Types • Animal Viruses • DNA vs RNA animal viruses • Differences in replicating viral genome • both ss and ds DNA & RNA forms • DNA Viruses (E.g. smallpox, warts, tumors, herpes, colds) • Life Cycle • Attachment, penetration, (uncoating) • Replication of DNA in nucleus of host • Assembly in nucleus • Lysis from nucleus and plasma membrane • RNA Viruses (E.g. Polio, rabies, hepatitis, influenza, AIDS) • Life Cycle of RNA->RNA viruses • Attachment, penetration, (uncoating) • Replication of RNA to RNA in cytoplasm • Assembly in cytoplasm, then lysis • Retroviruses (HIV) • Types of Infections: Latent (herpes, shingles), slow (encephalitis), prions (kuru, CJD) • Oncogenesis • 15% of cancers are virally causes (e.g. EBV (mononucleosis), HIV, papovaviruses-warts) • Carcinogenic agents: mutagens, radiation, viruses • Cancer cell characteristics (contact inhibition loss, chromosome number) Figure 13.1

  12. Multiplication of a Retrovirus Capsid Reverse transcriptase DNA Virus Two identical + stands of RNA 1 Retrovirus penetrates host cell. Host cell RNA tumor viruses HIV-AIDS DNA of one of the host cell’s chromosomes 5 Mature retrovirus leaves host cell, acquiring an envelope as it buds out. Reverse transcriptase 2 Virion penetrates cell and its DNA is uncoated Viral RNA Identical strands of RNA 4 Transcription of the provirus may also occur, producing RNA for new retrovirus genomes and RNA that codes for the retrovirus capsid and envelope proteins. Viral proteins RNA 3 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. Provirus (Hepatitis B also uses reverse transcriptase) Figure 13.19

  13. Viruses: Bacterial and Animal Types • Animal Viruses • DNA vs RNA animal viruses • Differences in replicating viral genome • both ss and ds DNA & RNA forms • DNA Viruses (E.g. smallpox, warts, tumors, herpes, colds) • Life Cycle • Attachment, penetration, (uncoating) • Replication of DNA in nucleus of host • Assembly in nucleus • Lysis from nucleus and plasma membrane • RNA Viruses (E.g... Polio, rabies, hepatitis, influenza, AIDS) • Life Cycle of RNA->RNA viruses • Attachment, penetration, (uncoating) • Replication of RNA to RNA in cytoplasm • Assembly in cytoplasm, then lysis • Retroviruses (HIV) • Types of Infections: Latent (herpes, shingles), slow (encephalitis), prions (kuru, CJD) • Oncogenesis • 15% of cancers are virally causes (e.g. EBV (mononucleosis), HIV, papovaviruses-warts) • Carcinogenic agents: mutagens, radiation, viruses • Cancer cell characteristics (contact inhibition loss, chromosome number) Figure 13.1

  14. Special Types of Viral or Viral-Like Infections • Acute infections • Peristent Viral Infections • Latent: Virus remains in asymptomatic host cell for long periods • Cold sores, shingles • Chronic: Infectious virus can be detected at all times • Hep B and C • Slow Viral Infections • Disease processes occurs over a long period, generally fatal • Subacute sclerosing panencephalitis (measles virus) • Retrovirus disease(HIV) • Prions (Protein infectious particles) – CJD, kuru, scrapie

  15. Prions (Proteinaceous Infectious Agents) Prion diseases: Creutzfeld-Jacob Disease (CJD), kuru, scrapie, bovine spongiform encephalophaty (BSE) PrPSc PrPc 2 3 4 1 Lysosome Endosome 5 6 7 8 Abnormally folded protein“recruits” normal ones to fold abnormally, leading to accumulations of abnormal proteins and neuron death. Abnormal protein is resistant to UV light, and proteases Figure 13.21

  16. Viruses: Bacterial and Animal Types • Animal Viruses • DNA vs RNA animal viruses • Differences in replicating viral genome • both ss and ds DNA & RNA forms • DNA Viruses (E.g. smallpox, warts, tumors, herpes, colds) • Life Cycle • Attachment, penetration, (uncoating) • Replication of DNA in nucleus of host • Assembly in nucleus • Lysis from nucleus and plasma membrane • RNA Viruses (E.g... Polio, rabies, hepatitis, influenza, AIDS) • Life Cycle of RNA->RNA viruses • Attachment, penetration, (uncoating) • Replication of RNA to RNA in cytoplasm • Assembly in cytoplasm, then lysis • Retroviruses (HIV) • Types of Infections: Latent (herpes, shingles), slow (encephalitis), prions (kuru, CJD) • Oncogenesis • 15% of cancers are virally causes (e.g. EBV (mononucleosis), HIV, papovaviruses-warts) • Carcinogenic agents: mutagens, radiation, viruses • Cancer cell characteristics (contact inhibition loss, chromosome number) Figure 13.1

  17. Cancer Cell Characteristics Cancer cell characteristics: loss of contact inhibition, chromosome abnormalities, cell fusion (polykaryocytes)

  18. Some Viruses are Oncogenic

  19. Viral Cancer Results Mostly From Activation of Oncogenes • Proto-oncogenes: Normal genes in human cells that control cellular division (mitosis) • Activated proto-oncogenes (oncogenes) transform normal cells into cancerous cells. Requires at least “2 hits” • Double-stranded DNA viruses cause most virus-induced tumors • Virus can go through productive cycle and lyse cell OR • Virus can transform cell without killing it by integrating into the middle of an oncogene

  20. Viruses: Bacterial and Animal Types • Animal Viruses • DNA vs RNA animal viruses • Differences in replicating viral genome • both ss and ds DNA & RNA forms • DNA Viruses (E.g. smallpox, warts, tumors, herpes, colds) • Life Cycle • Attachment, penetration, (uncoating) • Replication of DNA in nucleus of host • Assembly in nucleus • Lysis from nucleus and plasma membrane • RNA Viruses (E.g... Polio, rabies, hepatitis, influenza, AIDS) • Life Cycle of RNA->RNA viruses • Attachment, penetration, (uncoating) • Replication of RNA to RNA in cytoplasm • Assembly in cytoplasm, then lysis • Retroviruses (HIV) • Types of Infections: Latent (herpes, shingles), slow (encephalitis), prions (kuru, CJD) • Oncogenesis • 15% of cancers are virally causes (e.g. EBV (mononucleosis), HIV, papovaviruses-warts) • Carcinogenic agents: mutagens, radiation, viruses • Cancer cell characteristics (contact inhibition loss, chromosome number) Figure 13.1

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