Transcript What is a Virus?

Viruses and
Computer Scientists
Courtney D. Corley
Computational Epidemiology Research Laboratory
Department of Computer Science
University of North Texas
Department of Biostatistics
UNT Health Science Center
Motivation
Why is a computer scientist looking at
viruses?
Current Research in Comp Epi
• Graph-based data mining (SUBDUE)
• Dynamic social networks (STD transmission dynamics)
• Models and tools to facilitate public health strategy
evaluation
• Global Stochastic Field Simulation
• Agent-based Models
Herpes Simplex type-1
Herpes Simplex type-1
Smallpox
Smallpox
Overview
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Motivation
Etymology
Epistemology
Living Cells
Virus definition
Viral diversity
Conclusion
Etymology
• Derived from Latin: virulentus poisonous
• 1392 -- first used in English.
• 1728 – “agent that causes infectious
diseases”
• 1972 – biological virus and metaphor for
other parasitically reproducing things.
Virus
A subcellular parasite with genes of DNA or
RNA and which replicates inside the host
cell upon which it relies for energy and
protein synthesis.
In addition, it has an extra-cellular form in
which the virus genes are contained inside
a protective coat
Epistemology part 1
Are viruses “GOOD” or “BAD”?
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Biological Knowledgebase
Viro-therapy
Vectors
Nanotechnology – the golden thread
Epistemology part 2
Is a virus “ALIVE” or “DEAD”
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Living Cells
Which of the following apply to a living cell?
a)
b)
c)
d)
e)
It contains genetic information (DNA)
It uses RNA as a genetic messenger
It is capable of making its own proteins
It generates its own energy
It is surrounded by a cell membrane
Living Cell
A Virus Flunks the “Living Cell” test
c) It is capable of making its own proteins
d) It generates its own energy
Is the following true?
e) It is surrounded by a cell membrane
What defines a “VIRUS”
• Cannot multiply without a host cell
• Intracellular parasites
• Two forms
– Viron – inert particle that survives out of the
host cell
– Active intracellular phase
• Capsid – Protein surrounding a length of
nucleic acid (DNA or RNA) which caries the
virus genes.
• Viral Genome
Virus Lifecycle
a)
b)
c)
d)
e)
f)
Attachment to the correct host cell
Entry of the virus genome
Replication of the virus genome
Manufacture of the virus proteins
Assembly of new virus particles
Release of new virus particles from the
host cell
Retrovirus: Infection and Replication
Thief
Many animal viruses have an extra envelope
outside the protein shell.
This membrane is STOLEN from the
previous host cell into which viruses have
been stuck.
Now, the virus encoded proteins function to
detect and bind to the next target cell
Animal Virus
When an enveloped virus enters a new cell, its
envelope layer merges with the cell membrane
and the inner protein shell containing the nucleic
acid enters.
Once inside, the protein shell disassembles
exposing the genome
Bacterial Virus
Cell wall protects cell membrane – so
Bacteriophages do not bother with an outer
envelope.
After binding to cell surface, they inject their
genome into the bacterial cell and leave the
protein shell behind
Summary
• Viral Philosophy
• Living Cells
• Great Diversity
– Animal
– Bacteria
Thanks!
References:
“Molecular Biology Made Simple and Fun” Clark and Russell
http://science.nhmccd.edu/biol/bio1int.htm#virus
http://www.whfreeman.com/kuby/content/anm/kb03an01.htm
http://www.hhmi.org/biointeractive/animations/anim_index.htm
http://www.hhmi.org/biointeractive/animations/subunit/sub_frames.htm
http://www.hhmi.org/biointeractive/animations/infection/inf_frames.htm
http://pathmicro.med.sc.edu/weaver/testflash-1.htm
http://highered.mcgrawhill.com/sites/0072437316/student_view0/chapter26/animations.html