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Virus Infection

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Virus Infection Major responses of plants and animals to virus infections The scientific basis for prevention and treatment of virus diseases Transmission of plant ... – PowerPoint PPT presentation

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Title: Virus Infection


1
Virus Infection
  • Major responses of plants and animals to virus
  • infections
  • The scientific basis for prevention and
    treatment of
  • virus diseases

2
Transmission of plant viruses
  • Mechanical
  • Seeds
  • Vegetative propagation/grafting
  • Vectors
  • Bacteria (e.g. Agrobacterium tumefaciens - Ti
    plasmid)
  • Fungi
  • Nematodes
  • Arthropods
  • insects
  • arachnids

3
Movement Proteins
4
Symptoms of virus infection in plants
  • Growth retardation
  • Distortion
  • Mosaic patterning on leaves
  • Yellowing
  • Wilting
  • Resulting from
  • Necrosis
  • Hypoplasia
  • Hyperplasia

5
The hypersensitive response
  • Pathogenesis-related (PR) proteins
  • Production of cell wall phenolic substances
  • Release of active oxygen species
  • Production of phytoalexins
  • Accumulation of salicylic acid

6
Virus-resistant plants
  • Traditional plant breeding
  • Transgenic plants expressing
  • Virus coat proteins
  • Intact or partial virus replicases
  • Antisense RNAs
  • Defective virus genomes
  • Satellite sequences
  • Catalytic RNA sequences (ribozymes)
  • Modified movement proteins

7
Immune Responses to Virus Infections in Animals
  • Humoral immune response

8
Cell-mediated immunity
9
Recognition of virus-infected cells
10
Viruses and Apoptosis
11
Interferons
1957, Alick Issacs and Jean Lindenmann
12
Different types of interferon (IFN)
  • IFN-a
  • IFN-ß
  • Other interferons

13
Induction of interferon synthesis
  • Virus infection
  • Double-stranded (ds) RNA
  • Metabolic inhibitors

14
Interferon Antiviral Mechanisms
  • Induction of 2',5'-oligo A synthetase

15
Interferon Antiviral Mechanisms
  • Activation of PKR

16
Evasion of Immune Responses by Viruses
  • Inhibition of MHC-I-restricted antigen
    presentation
  • Inhibition of MHC-II-restricted antigen
    presentation
  • Inhibition of natural killer cell lysis
  • Interference with apoptosis
  • Inhibition of cytokine action
  • Evasion of humoral immunity
  • Evasion of the complement cascade

17
VirusHost Interactions
  • Site of virus entry
  • into the body

18
Transmission of viruses through the environment
19
Local infection
  • Virus infection of polarized epithelial cells

20
Outcome of infection
  • Clearance vs. persistence
  • Antigenic variation
  • Antigenic drift
  • Antigenic shift

21
The Course of Virus Infections
  • Abortive Infection
  • Acute Infection
  • Chronic Infection
  • Persistent Infection
  • Latent Infection

22
Prevention and Therapy of Virus Infection
  • Drugs (cure) versus vaccines (prevention)
  • Synthetic vaccines
  • Recombinant vaccines
  • DNA vaccines
  • Subunit vaccines
  • Virus vectors are recombinant viruses
  • Inactivated vaccines
  • Attenuated vaccines

23
RNA interference (RNAi)
24
Virus Vectors and Gene Therapy
  • Delivery of large biomolecules to cells
  • The possibility of targeting a specific cell
    type
  • High potency of action due to replication of
    vector
  • Potential to treat cancer

25
Chemotherapy of Virus Infections
  • Chemotherapeutic index
  • Dose of drug that inhibits virus replication
  • Dose of drug that is toxic to host
  • The process targeted by a drug must be
    essential for
  • replication
  • The drug is active against the virus but has
  • acceptable toxicity to the host

26
Chemotherapy of Virus Infections
  • Attachment
  • Penetration/uncoating - Amantadine
  • Genome replication -
  • Acyclovir, reverse transcriptase inhibitors
  • Gene expression, release - ?
  • Maturation - protease inhibitors

27
Summary
  • Virus infection is a complex, multistage
    interaction between the virus and the host
    organism.
  • The course and outcome of any infection are the
    result of a balance between host and virus.
  • Host factors include route of virus transmission
    and the immune response.
  • Virus processes include site of initial
    infection, spread throughout the host, regulation
    of gene expression to evade the immune response.

28
Further Reading
  • Aliyari, R. Ding S.W. (2009) RNA-based viral
    immunity initiated by the Dicer family of host
    immune receptors. Immunol Rev. 227(1) 176-188
  • Crotty, S. and Andino, R. (2002) Implications of
    high RNA virus mutation rates lethal mutagenesis
    and the antiviral drug ribavirin. Microbes and
    Infection, 4 13011307
  • Coiras, M., López-Huertas, M.R., Pérez-Olmeda, M.
    and Alcamí, J. (2009) Understanding HIV-1 latency
    provides clues for the eradication of long-term
    reservoirs. Nat Rev Microbiol. 7(11) 798-812
  • Cullen, B.R. (2010) Five Questions about Viruses
    and MicroRNAs. PLoS Pathog 6(2) e1000787
  • Ding, S.W. Voinnet. O. (2007) Antiviral
    immunity directed by small RNAs. Cell 130(3)
    413-426
  • Kindt, T.J., Goldsby, R.A., Osborne, B.A. Kuby,
    J. (2007) Kuby Immunology. W.H. Freeman,
    ISBN 1429202114.
  • Kutzler, M.A. Weiner, D.B. (2008) DNA vaccines
    ready for prime time? Nature Reviews Genetics 9
    776-788
  • Lisnica, V.J., Krmpotica, A. and Jonjica, S.
    (2010) Modulation of natural killer cell activity
    by viruses. Current Opinion in Microbiology
    13(4) 530-539
  • Liu, T.C. Kirn, D. (2008) Gene therapy progress
    and prospects cancer oncolytic viruses. Gene
    Ther 15(12) 877-884
  • Lu, L.F. Liston A. (2009) MicroRNA in the
    immune system, microRNA as an immune system.
    Immunology 127(3) 291-298
  • Mallery, D.L. et al (2010) Antibodies mediate
    intracellular immunity through tripartite
    motif-containing 21 (TRIM21) PNAS USA 107(46)
    19985-19990
  • Palese P. (2006) Making better influenza virus
    vaccines? Emerg Infect Dis. http//www.cdc.gov/nci
    dod/EID/vol12no01/05-1043.htm
  • Randall, R.E. and Goodbourn, S. (2008)
    Interferons and viruses an interplay between
    induction, signalling, antiviral responses and
    virus countermeasures. J Gen Virol. 89(1)
  • Sen, G.C. (2001) Viruses and interferons. Annual
    Review of Microbiology, 55 255281
  • Tortorella, D. et al. (2000) Viral subversion of
    the immune system. Annual Review of Immunology,
    18 861926
  • Welsh, R.M. et al. (2004) Immunological memory to
    viral infections. Annual Review of Immunology,
    22 711743
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