Louis Pasteur was the first to propose that organisms smaller than bacteria caused disease. Common viral diseases include the common cold, rabies, AIDS, influenza, and SARS. Viruses are ultra-microscopic and can only be seen with an electron microscope. All viruses contain a central nucleic acid surrounded by a protein capsid that may have an outer envelope. Viruses replicate through entering a host cell and hijacking the cell's machinery to produce new viral components that assemble and exit to infect new cells. Diagnosing viruses involves culturing appropriate cells and tissues to look for cytopathic effects or detecting viral and immune components.

1. VIRULOGY - INTRODUCTION
Dr. Ashish V. Jawarkar, M.D. (Path)
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4. History
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Louis Pasteur was the first to suspect
that organisms smaller than bacteria
existed
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6. Viral diseases
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Common cold
Rabies
AIDS
Influenzae
SARS
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7. Morphology
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Size –
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Ultramicroscopic
Seen only by electron microscope
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9. Size of viruses
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11. The Viral Structures and
Shape
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12. 
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Central nucleic acid (DNA or RNA)
Capsid
May / may not have outer covering
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13. Capsids
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All viruses have capsids- protein coats
that enclose & protect their nucleic acid
Each capsid is constructed from
identical subunits called capsomers
made of protein
2 types:
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helical
iscosahedral
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14. Shape of Viruses, determined by the
arrangement of proteins (capsomers) in
the capsid
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15. Helical
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16. Icosahedral
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17. Additional Structures in some
Viruses, envelope and surface
proteins
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18. Function of the envelope
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19. Naming viruses
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No taxa above Family (no kingdom,
phylum, etc)
19 families of animal viruses
Family name ends in -viridae ,
Herpesviridae
Genus name ends in -virus,
Simplexvirus
Herpes simplex virus I (HSV-I) 19

20. EXAMPLE of VIRAL TAXONOMY
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Family – Herpesviridae
Genus – Varicellovirus
Common name – chickenpox virus
Disease - chickenpox
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21. VIRAL REPLICATION
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22. Phage Replication
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23. 6 steps in phage replication
1.
2.
3.
4.
5.
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adsorption – binding of virus to specific
molecule on host cell
penetration –genome enters host cell
replication – viral components produced
assembly - viral components assembled
maturation – completion of viral formation
release – viruses leave cell to infect other
cells

24. Fig 6.11
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25. Penetration
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26. Bacteriophage assembly line
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27. Impact of Bacteriophages
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Not all bacteriophages lyse cells
Temperate phages insert their viral DNA into
the host chromosome & viral replication stops
at there until some later time.
Lysogeny- bacterial chromosome carries
phage DNA
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28. Types of viruses
DNA and RNA viruses replicate in
different manner.
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29. The Most Common DNA
Viruses
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Adenoviruses
Cytomegalovirus
Epstein-Barr virus
Hepatitis B virus
Herpes simplex Types 1 &2
Papovavirus
Varicella-Zoster virus
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30. The RNA Viruses
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Dengue viruses
Ebola virus
Picorna viruses
Hanta virus
Hepatitis A and C
HIV
Influenza virus
Mumps virus
Norwalk virus
Corona virus
Rotavirus
Rubeola Virus
RSV
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31. VIRAL CPE
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32. Cytopathic effects- virusinduced damage to cells
1.
2.
3.
4.
5.
6.
7.
changes in size & shape
cytoplasmic inclusion bodies
nuclear inclusion bodies
cells fuse to form multinucleated cells
cell lysis
alter DNA
transform cells into cancerous cells
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33. Cytopathic changes in cells
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34. Inclusion body
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35. Transformation or conversion of cell division
to cells that divide indefinitely ( tumors
,warts)
Induces hyperplasia of the host cells
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36. Host Response to Viral
Infections
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37. 
Host Cell response includes :
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Antibody response
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Cellular Immune response
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Interferon production
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38. Antibody Response
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39. Cellular Immune response
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40. Interferons
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41. Diagnostic Virology
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42. How do we grow viruses?
Obligate intracellular parasites
require appropriate cells to
replicate.

43. Growing animal viruses
1.
2.
3.
live animals
bird embryos – chicken, duck; intact,
self-supporting unit, sterile, selfnourished
cell culture- cell lines
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44. Virus laboratory
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45. Cell Culture
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Cell culture is the process by which
prokaryotic, eukaryotic or plant cell are
grown under controlled conditions.
"cell culture" now , refers to the
culturing of cells derived from
multicellular eukaryotes, especially
animal cells.
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46. Cell lines
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Cells that are cultured directly from a subject are
known as primary cells.
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primary cell cultures have limited lifespan
after a certain number of population doublings cells undergo
the process of senescence and stop dividing, while generally
retaining viability.
An established or immortalised cell line has acquired
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the ability to proliferate indefinitely either through random
mutation or deliberate modification, such as artificial
expression of the telomerase gene
There are numerous well established cell lines
representative of particular cell types.
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47. Established human cell lines
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One of the earliest human cell lines,
descended from Henrietta Lacks, who
died of cervical cancer .
The cultured HeLa cells shown below
have been stained with Hoechst turning
their nuclei blue.
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48. Tissue Culture
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49. Tissue Culture
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50. No virus
virus
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51. Egg Inoculation
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52. Egg inoculation …
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53. Diagnosis of viral diseases
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More difficult than other agents
Consider overall clinical picture
Take appropriate sample
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Infect cell culture- look for characteristic
cytopathic effects
Screen for parts of the virus
Screen for immune response to virus
(antibodies)
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54. diagnosis
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55. Thank you end of lecture !
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