1. Chapter 30 Replication and variation of viruses

2. Section 1
multiplication of viruses

3. Basic steps in viral multiplication cycle
Adsorption (attachment)
Penetration or entry
Uncoating to release the genome
virion component production
Assembly (maturation)
Release from the cell

4. Productive or lytic response the Basic steps
nonproductive response or lysogeny
no new virus is produced
the cell survives and divides
the viral genetic material persists indefinitely in a latent state
in the case of bacteriophages

5. Lytic or virulent viruses
can enter only into a productive relationship
temperate viruses
can establish ether a productive or a nonproductive relationship

6. Basic steps in viral multiplication cycle
self -replication
adsorption/
attachment ↓
penetration
uncoating
biosynthesis
assembly & release

7. Viral growth curve Fig 29-1
Eclipse period
Latent period
Cytopathic effect (CPE)

8. Specific events during the growth cycle

9. Adsorption or attachment
•Nonspecific adsorption
•Specific combination
---static electricity-combination between virus and cell
---virion attachment proteins adsorb to specific receptor on the surface of susceptible cells

10. Entry Uncoating naked virus---by endocytosis or viropexis
(吞饮或胞饮)
naked virus---by endocytosis or viropexis
enveloped virus---by fusion of viral envelope with host-cell membrane
(病毒胞膜与宿主细胞膜融合)
Uncoating
---The viral nuclei acid is
released from the capsid

11. ADSORPTION

12. ADSORPTION
Requires viral attachment protein
Cellular receptors

14. PENETRATION - ENVELOPED VIRUSES
Fusion融合with plasma membrane
Entry via endosomes内含体

15. herpesviruses, paramyxoviruses, HIV
PENETRATION
herpesviruses, paramyxoviruses, HIV

16. PENETRATION - ENVELOPED VIRUSES
Fusion with plasma membrane
Entry via endosomes

19. H+

20. VIRUS UPTAKE BY CLATHRIN COATED PITS内陷小窝
Called :Viropexis病毒吞饮/ endocytosis / pinocytosis

21. PENETRATION NON-ENVELOPED VIRUSES
entry directly across plasma membrane

22. PENETRATION NON-ENVELOPED VIRUSES
entry directly across plasma membrane

23. H+

24. UNCOATING Need to make genome available
Once uncoating occurs, enter eclipse period
Eclipse phase lasts until first new virus particle formed

25. BIOSYNTHESIS OF VIRUSES
mRNA production
genome synthesis
protein synthesis
early protein (function protein)
late protein (structural protein)

26. Gene expression and genome replication
Viral
(+) mRNA

27. biosynthetic site DNA in the nucleus RNA in the cytoplasm
protein in the cytoplasm

28. Biosynthesis of ds-DNA virus
利用核内依赖DNA 的RNA多聚酶转录
parental ds-DNA
early mRNA ⑴
in nucleus
in the cytoplasm ⑵
DNA聚合酶
半保留复制
early protein
progeny ds-DNA
later mRNA ⑶
in the cytoplasm
later protein
⑴biosynthesis of early protein---依赖DNA的DNA聚合酶等
⑵replication of progeny DNA
⑶biosynthesis of late protein

29. Biosynthesis of ss-RNA virus
acts directly as mRNA
parental ㈩ss-RNA
(依赖RNA的RNA聚合酶)
in the cytoplasm
early protein
+RNA acts as mRNA
later protein
㈠ss-RNA(±RNA)
(复制中间型)
progeny ㈩ss-RNA
----RNA must first transcribe the complementary
plus strand

30. ECLIPSE PHASE P260
The period of infection in which no infectious viruses are found inside the cell
The original virions lose their infectivity soon after entry

31. Assembly
the process of enclosing the viral genome in a protein capsid

32. release Disintegration 崩解: naked virus cause the host cell lysis
Budding: enveloped viruses
Budding viruses do not necessarily kill the cell. Thus, some budding viruses may be able to set up persistence

33. Release Budding through plasma membrane (enveloped virus)
Rupture(un-enveloped virus)

34. Replication cycle of virus
• progeny viruses • produce cell effects---damage and lysis of cells
adsorption
assembly and release
penetration
uncoating
biosynthesis
protein and nucleic acid

35. Abnormal multiplication of viral & interference
 Abortive infection (顿挫感染,无效感染)
When a virus infects a cell (or host), but cannot complete the full replication cycle ( not biosynthesize their components or not assemble virions.), i.e. a non-productive infection.
non-permissive cells
permissive cells(容纳性细胞)

36. Section 2
viral variation and resistence

37. defective viruses
Lacks one or more functional genes required for viral replication
Require helper activity from another virus for some step in replication or maturation

38. interference
Two viruses often leads to an inhibition of multiplication of one of the viruses
两种病毒同时感染同一种细胞,发生一种病毒抑制另一种病毒复制的现象称为干扰现象

39.  defective interfering particle (DIP)

40. Viral resistance 耐冷不耐热 耐抗生素和甘油 消毒剂可灭活 ；包膜病毒对脂溶剂敏感 pH5.0以下或pH9.0 以上迅速灭活
紫外线、χ线和射线可灭活
消毒剂可灭活 ；包膜病毒对脂溶剂敏感