Introduction_to_Virology_Medicaltechnology

Virology is the branch of science that studies viruses, which are microscopic infectious agents that require a host cell to replicate and propagate. It encompasses the structure, function, classification, and evolution of viruses, as well as their interactions with host organisms. Key areas of virology include:

1. **Virus Structure**: Understanding the physical composition of viruses, including their genetic material (DNA or RNA) and protein coats (capsids).

2. **Virus Replication**: Studying how viruses invade host cells, hijack cellular machinery, and produce new viral particles.

3. **Virus Classification**: Categorizing viruses based on their morphology, genetic material, and replication strategies.

4. **Pathogenesis**: Investigating how viruses cause disease, including mechanisms of viral infection and immune response.

5. **Epidemiology**: Examining the spread of viral infections within populations and strategies for controlling outbreaks.

6. **Antiviral Therapy and Vaccines**: Developing treatments and preventative measures to combat viral diseases.

Virology is crucial for understanding infectious diseases, developing vaccines, and addressing global health challenges.

1. INTRODUCTION TO VIROLOGY
CHARMAINE C MIRANDILLA

2. WHAT IS
VIRUS?
-Smallest infectious
agent
- a minuscule, acellular,
infectious agent
usually having one or
several pieces of
nucleic acid—either
DNA or RNA.

3. Why do we study Viruses?
1.Virus are everywhere
●Viruses infect all living
things
●We regularly eat and
breathe billions of virus
particles
●We carry viral genomes as
part of our own genetic
material

4. Did you Know?
●There are more than 10^ 30
Bacteriophage in the world's
oceans
●Whales are infected with
Caliciviridae that causes
rashes, blisters, intestinal
problems and they excrete it
10^13 calicivirus particles

5. Why do we study Viruses?
2. Viruses can Cause Human Disease
●Small pox
●Influenza
●Hepatitis
●HIV
●Cervical cancer
●COVID 19

6. Why do we study Viruses?
4. Virus can be Beneficial
●Viral infections in the ocean kill 20 to 40% of marine
microbes daily, converting these living organisms into
particulate matter, and in so doing release essential
nutrients that supply phytoplankton
●Infection of Hepatitis G in patient with HIV can
decrease the progression of disease
●Murine herpesvirus are resistant with Listeria
monocytogenes and Yersinia pestis
●Can stimulate Immune System

7. Why do we study Viruses?
5. Viruses are Unique Tools to
Study Biology
●Bacteriophage is
Foundation of Molecular
Biology
● Tobacco mosaic virus was a
landmark in structural
biology
●Development of
Recombinant DNA
Technology
●Use of Viral Vector

11. Becareful:Avoidanthropomorphicanalyses
Viruses do NOT think!
(or employ, ensure, exhibit, display, etc...)
They do not achieve their goals in a human-centered
manner
Viruses are passive agents!
Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University
©Principles of Virology, ASM Press

12. Viruses replicate by assembly of
pre-formed components into
particles
many
Make the parts,
assemble the final product
Not binary fission like cells
Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University ©Principles of Virology, ASM Press

13. Go to:
b.socrative.com/login/student
room number: virus
Which of the following is true concerning bacterial vs. viralreplication?
1.
2.
3.
4.
5.
Viruses must assemble using pre-formed components
Bacteria do not replicate via binary fission
Bacteria must assemble using pre-formed
Viruses do not have an "eclipse" period
Viruses replicate by binary fission
as viruses do
components
2
Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University

14. Howoldareviruses?
Orthoceras, a nautiloid cephalopod, 488 Ma
Nobu Tamura (http://spinops.blogspot.com)
•Estimates of molecular evolution
retroviruses >450 Ma, Ordovician
Likely originated billions of years
suggest marine
period
origin of some
• ago - before cells?
Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University ©Principles of Virology, ASM Press

15. Immunization
•Variolation - China (11th century), Lady Montagu
(1700s)
No knowledge of agent
Survivors of smallpox protected against disease
1790s - experiments by Edward Jenner in England
establish vaccination
•
•
•
Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University

16. Conceptofmicroorganisms
•
•
•
Leeuwenhoek (1632 -
Pasteur (1822 - 1895)
1723)
Koch(1843-1910)
Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University ©Principles of Virology, ASM Press

17. Theevolvingconceptofvirus
•As early as 1728, ‘virus’ was used to describe an
infectious disease
agentthatcauses
•
•
Virus = Latin, poison; so thought tobe liquids
Pasteur(1822-1895):“Everyvirusisamicrobe”
Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University

18. Keyevent: Chamberlandfilter
•Developed a porcelain filter to remove bacteria
from drinking water
•Pasteur
thought
foundthat rabies agent passedthroughit,
itwasasmallbacterium
Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University

19. Virology Lectures 2019 • Prof. Vincent Racaniello • Columbia University ©Principles of Virology, ASM Press

20. Filterable viruses
•
•
1898 - Loeffler & Frosch - agent of foot & mouth disease is filterable
Key concept: agents not only small,
in broth
but replicateonlyinthehost,not
•
•
0.2 micron filters (μm, onemillionthofameter)
Stillthoughttobeliquids
Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University

21. Filterablevirusdiscovery
•
•
•
•
•
•
•
1901
1903
1906
1908
1911
1915
1933
-
-
-
-
-
-
-
first human virus,
rabies virus
variola virus
chicken leukemia
yellow fever virus
virus,poliovirus
Rous sarcoma virus
bacteriophages
influenza virus
©Principles of Virology, ASM PressVirology Lectures 2020 • Prof. Vincent Racaniello • Columbia University

22. Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University ©Principles of Virology, ASM Press

23. 1939-Viruses arenotliquids!
microscope•
•
Helmut Ruska built first electron 1933
FirstEMofbacteriophage,1939
Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University

24. Key1939 experimentproved that viruses
werenotsimplysmallbacteria
Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University ©Principles of Virology, ASM Press

25. ©Principles of Virology, ASM PressVirology Lectures 2020 • Prof. Vincent Racaniello • Columbia University

26. Weknowmanydetailsaboutviruses
Virology Lectures 2019 • Prof. Vincent Racaniello • Columbia University

Chemical formula for poliovirus:
C
332,652
H
492,388
N
98,245
O
131,196
P
7,501
S
2,340

27. Virusclassification
•
•
•
•
Nature and sequence of nucleic acid
Symmetry of protein shell (capsid)
in virion
Presence or
Dimensions
absence of lipid
of virus particle
membrane(envelope)
©Principles of Virology, ASM PressVirology Lectures 2020 • Prof. Vincent Racaniello • Columbia University

28. Virusclassification
http://ictvonline.org/
Classical hierarchical
Kingdom
Phylum
Class
Order (-virales)
system:
Family (-viridae)
Genus (-virus)
Species*
Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University
Filoviridae
Ebolavirus
(filovirusfamily)
Zaire ebolavirus

29. Virusdiscovery-Oncedrivenonlybydisease
Analyzed RNA from 220 invertebrate species, found 1,445 newviruses
Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University http://www.nature.com/nature/journal/v540/n7634/full/nature20167.html

30. CHARACTERISTIC OF VIRUSES

31. STRUCTURE OF VIRUS
●Viral genome: RNA or DNA
●Capsid: protein coat that
encloses the genome
○Capsid + genome =
Nucleocapsid
●Capsomere
○represent clusters of
polypeptides seen in
icosahedral
●The entire virus particle is
called virion

32. VIRAL GENOME
●Composed of either RNA or DNA
●4 category based on the virus
genome
○Double stranded DNA
○Single stranded DNA
○Double stranded RNA
■Fungal viruses
○Single stranded RNA
■Plant viruses
●Basis of molecules
○Linear
○Circular

33. VIRAL PROTEIN
●As the size of genome increases the number of protein
increases.
○Structural protein
■Protects the virus genome
■Attachment of the virion to a host cell
■Fusion of the virion envelope to cell membrane
○Non structural Protein
■enzymes, e.g. protease, reverse transcriptase
■ transcription factors
■primers for nucleic acid replication
■interference with the immune response of the host

34. CAPSID
●A Protein coat that encloses the genome
●Function:
○the protection of the genome
○To recognize and attach to a host cell.
●Capsomere
○Cluster of polypeptide common in icosahedral
viruses

35. FUNCTION OF CAPSID
●Protects the viral genome
● Is the site of receptors necessary for naked viruses to initiate infection
● Stimulates antibody production
●Is the site of antigenic determinants important in some serologic tests

36. Symmetry or
Morphology
●Helical
○Complete virion
○Capsomere are in bagel shape
○Rod shape capsid
●Icosahedral
○Cube like
●Complex
○Non forming symmetry
○Example Poxviridae

38. OUTERMEMBRANE
ENVELOPE
●Phospholipid labile covering
●Susceptible to inactivation
○High temperature
○Extreme pH
○Chemical
●Host origin
●Peplomer (Spikes)
○Virus encoded glycoprotein
●Cannot infect GI tract.

NAKED/ NON ENVELOPE
•Heat resistant
•Lipid membrane

40. CLASSIFICATION OF VIRUSES
●Virion Morphology
○Based on Size, shape, type of symmetry, presence or absence of peplomer
●Virus genome (Baltimore Classification)
○Type of Nucleic Acid (DNA or RNA)
○Whether it is linear or circular
○Sense (positive, negative or ambisense)
○Size of genome
○Strandedness (Double or Single stranded)
●Physicochemical properties
●Virus Protein

41. CLASSIFICATION OF VIRUSES: DNA
VIRUSES
●Herpesviridae
●Hepadnaviridae
●Poxviridae
●Parvoviridae
●Adenoviridae
●Papovaviridae

•All DNA are Double
Stranded except
Parvoviridae
•All DNA viruses are
icosahedral except
Poxviridae
•Enveloped
•Herpesviridae
•Hepadnaviridae
•Poxviridae

43. CLASSIFICATION OF VIRUSES: RNA
VIRUSES
●Picornaviridae
●Caliciviridae
●Reoviridae
●Retroviridae
●Togaviridae
●Flaviviridae
●Bunyaviridae
●Arenaviridae

•Filoviridae
•Paramyxoviridae
•Orthomyxoviridae
•Reoviridae
•Retroviridae
•Rhabdoviridae

44. CLASSIFICATION OF VIRUSES: RNA
VIRUSES
●All RNA viruses are Single Stranded, Helical and Envelope
●All are Single stranded except Reoviridae
●All are Helical except
○Picronaviridae
○Caliciviridae
○Reoviridae
○Retroviridae
○Togaviridae
○Flaviviridae

45. CLASSIFICATION OF VIRUSES: RNA
VIRUSES
●All are envelope except Picornaviridae,
Caliciviridae and Reoviridae
●Largest: Paramyxoviridae
●Smallest: Picornaviridae
●Arthropod borne or vector borne
○Bunyaviridae
○Flaviviridae
○Togaviridae
●Replicate in Nucleus
○Orthomyxoviridae and Retroviridae

47. BALTIMORE CLASSIFICATION

48. Thereisanunderlyingsimplicityandorder
toviruses becauseoftwosimplefacts
•All viral genomes are obligate molecular
function after they replicate in a cell
parasites that canonly
•All viruses must make mRNA that can be translatedby host
synthesisribosomes:
machinery
they areallparasitesofthehostprotein
Virology Lectures 2020 • Prof. Vincent Racaniello • Columbia University