Introduction to Virology

1. IntroductiontoVirology Masheal Aljumaah OCT2018

2. What is a virus? “ • Viruses are very different from the other microbial groups. They are so small (filterable) that most can be seenonly withanelectronmicroscope, and they are acellular (not cellular). • Viruses can reproduce only by using the cellular machinery of other organisms (obligatory intracellular parasites) 2

3. Virus HostRange The host range of a virus is the cells the virus can infect. spectrum of host Viruses are able to infect specific types of cells of onlyone host species. (host-specific) In rare cases, viruses cross the host-species barrier, thus expandingtheir host range.

4. (Virology Principles & Applications Book,p1)

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6. Structure ofVirus

7. BacteriophageStructure

8. VirusGenomes In contrast to prokaryotic and eukaryotic cells, in which DNA is always the primary genetic material (and RNA plays an auxiliary role), a virus can have eitherDNA orRNA but never both. Thenucleicacidofaviruscanbe single-stranded double-stranded.

9. Virus Nucleicacid

10. GeneralMorphology(basis of their capsidarchitecture.) ▷ Complex Viruses: example :bacteriophage. ▷ Helical Viruses: ▷ Polyhedral Viruses: ▷ Example: Ebola viruses ▷ Example: poliovirus.

11. How do we Detect and Measure Viruses? (Isolation, Cultivation, and Identification of Viruses) 11

13. They can not be cultivated on artificial culturemedia. 29

14. Methods for growing viruses in the laboratory solidmedia plaquemethod (detect and countviruses) (1)GrowingBacteriophages liquidmedia LivingAnimals (2) Growing Animal Viruses Embryonated Eggs CellCultures (3) Growing plant Viruses 32

15. “ ▷ However, viruses that use bacterial cells as a host (bacteriophages) are rather easily grown on bacterial cultures. 15

16. (1) Growing Bacteriophages in the Laboratory The Number of Plaques = Plaque- forming Units (PFU). Figure 4. plaquemethod. 33

17. (2)Growing AnimalViruses A- In Living Animals ▷ Some animal viruses can be cultured only in living animals, such as mice, rabbits, and guinea pigs. ▷ Most experiments to study the immune system’s response to viral infections . ▷ Animal inoculation may be used as a diagnostic procedure for identifyingand isolatinga virus from a clinical specimen.

18. (2)Growing AnimalViruses B- In EmbryonatedEggs: 5.

19. (2)Growing AnimalViruses • B- In Embryonated Eggs: • Viral growth is signalled by: • the death of the embryo. • embryo cell damage. • by the formation of typical pocks or lesions on the egg membranes. 5.

20. (2)Growing AnimalViruses C- In Cell Cultures: Cellcultureshavereplacedembryonatedeggsasthepreferredtypeofgrowthmedium formanyviruses.Cellcultures consistofcellsgrowninculturemediainthelaboratory.

21. (2)Growing AnimalViruses C- In Cell Cultures: Cell culture lines are started by treating a slice of animal tissue with enzymes that separate the individual cells (Figure5). These cells are suspended in a solution that provides the osmotic pressure, nutrients, and growth factors needed for the cells to grow.

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24. (3) Growing plant Viruses in the Laboratory

25. (3) Growing plant Viruses in the Laboratory

26. Figure 2. Tobacco mosaic virus(TMV)