viruses - PowerPoint PPT Presentation

1 / 29
About This Presentation
Title:

viruses

Description:

Multiply by using host cell's synthesizing machinery to cause the production of ... Inherited and transmissible by ingestion, transplant, & surgical instruments ... – PowerPoint PPT presentation

Number of Views:64
Avg rating:3.0/5.0
Slides: 30
Provided by: SMC1
Category:
Tags: viruses

less

Transcript and Presenter's Notes

Title: viruses


1
viruses
2
  • Living
  • Nonliving

3
  • Contain a single type of nucleic acid (DNA or
    RNA), protein coat, sometimes an envelope.
  • Are obligatory intracellular parasites. Multiply
    by using host cells synthesizing machinery to
    cause the production of specialized elements that
    can transfer the nucleic acid to other cells.

4
  • Multiply inside living cells by using the
    synthesizing machinery of the cell.
  • Why does this make targeting viruses difficult?

5
Host Range
  • The spectrum of host cells in which a virus can
    multiply.
  • Mot viruses infect only specific types of cells
    in one host species.
  • The host is determined by the specific attachment
    site on the host cells surface and the
    availability of host cellular factors.

6
Virus Size
Figure 13.1
7
Taxonomy of viruses
  • Currently based on type of nucleic acid, strategy
    for replication and morphology.
  • Virus family names end in viridae genus names
    end in virus
  • A viral species is a group of viruses sharing the
    same genetic information and ecological niche

8
Viral Taxonomy
  • Herpesviridae
  • Herpesvirus
  • Human herpes virus 1, HHV 2, HHV 3
  • Flue H1N1
  • Retroviridae
  • Lentivirus
  • Human Immunodeficiency Virus 1, HIV 2

9
Isolation, growth and identification
  • Must be grown on living cells.
  • Easiest to grow are bacteriophage, because
    bacteria are easy to grow.

10
Growth results.
  • Plaques for bacteriophage.
  • Cytopathic effects on cell culture.

11
Growing Viruses
  • Viruses must be grown in living cells.
  • Bacteriophages form plaques on a lawn of bacteria.

Figure 13.6
12
Growing Viruses
  • Animal viruses may be grown in living animals or
    in embryonated eggs.

Figure 13.7
13
Growing Viruses
  • Animal and plants viruses may be grown in cell
    culture.
  • Continuous cell lines may be maintained
    indefinitely.

Figure 13.8
14
Identification.
  • Serological tests (Antibodies)
  • RFLP and PCR
  • (Discussion)

15
Typical viral infection
  • Attachment
  • Penetration
  • Biosynthesis
  • Maturation
  • Release
  • Burst size and burst time

16
Bacterial cell wall
Bacterial chromosome
Capsid
DNA
Capsid
Sheath
Tail fiber
Tail
1
AttachmentPhage attaches to host cell.
Base plate
Pin
Cell wall
Plasma membrane
2
PenetrationPhage pnetrates host cell and
injects its DNA.
Sheath contracted
Tail core
3
Merozoites released into bloodsteam from liver
may infect new red blood cells
Figure 13.10.1
17
Tail
DNA
4
MaturationViral components are assembled into
virions.
Capsid
5
ReleaseHost cell lyses and new virions are
released.
Tail fibers
Figure 13.10.2
18
One-step Growth Curve
Figure 13.11
19
Lysogeny or Lytic?
20
The Lysogenic Cycle
Figure 13.12
21
Animal virus infection
  • Attachment
  • Penetration (endocytosis)
  • Uncoating
  • Biosynthesis

22
Attachment, Penetration, and Uncoating
Figure 13.14
23
Release of an enveloped virus by budding
Figure 13.20
24
Multiplication of DNA Virus
1
Papovavirus
Virion attaches to host cell
7
Virions are released
Host cell
DNA
Capsid
2
Virion penetrates cell and its DNA is uncoated
DNA
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
25
Viruses and Cancer.
  • Viruses incorporated in to the host genome can
    cause mistakes and errors resulting in unchecked
    growth of the cell.
  • It this accidental or are these sites targeted?

26
  • Latent Viral Infections
  • Virus remains in asymptomatic host cell for long
    periods
  • Cold sores, shingles
  • Persistent Viral Infections
  • Disease processes occurs over a long period,
    generally fatal
  • Subacute sclerosing panencephalitis (measles
    virus)

27
Prions
  • Infectious proteins
  • Inherited and transmissible by ingestion,
    transplant, surgical instruments
  • Spongiform encephalopathies Sheep scrapie,
    Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Sc
    heinker syndrome, fatal familial insomnia, mad
    cow disease
  • PrPC, normal cellular prion protein, on cell
    surface
  • PrPSc, scrapie protein, accumulate in brain cells
    forming plaques

28
Prions
PrPSc
PrPc
2
3
4
1
Lysosome
Endosome
5
6
7
8
Figure 13.21
29
Topics on the flue
  • http//content.nejm.org/cgi/content/full/NEJMe0903
    995
  • NEJM N1H1 site http//h1n1.nejm.org/
  • An Old presentation http//www.strongnet.org/17152
    0529114210850/lib/171520529114210850/Influenza_pre
    sentation.pdf
Write a Comment
User Comments (0)
About PowerShow.com