1. Saleh Bahaj
Prof. of Medical
Microbiology/Immunology
Replication of
viruses
Lecture 2

3. Objectives
By the end of this lecture the students will
be able to:-
I) Means of replication
II) Steps of virus replication
III) Action of anti-viral drug
V) Test yourself

4. Replication& Protein
synthesis of viruses
I) Means of replication

5. I) Means of Replication
Viruses Not
divided BUT
Replicate

6. I) Means of Replication
Obligate
intracellular N

7. Replication of
viruses
A) Enveloped viruses
II) Steps of virus replication

8. 1) Attachment
1) Attachment
(Adsorption)
2) Penetration
4) Eclipse
5) Synthesis of
viral components
6) Assembly
7) Release
3) Uncoating

9. 1) Attachment
Glycoprotein spikes
(Tropism)

10. 2) Penetration
Envelope fuses with
cytoplasmic membrane
(Fusion)

11. 2) Penetration
Nucleocapsid enter

12. 3) Uncoating

13. 4) Eclipse

14. 5) Synthesis of viral components

15. 6) Assembly

16. 7) Release
Budding (Partly from host cell)

17. Exercise 1
Discus with your
team the steps
of replication non-
enveloped virus
(Naked)

18. Replication of
viruses
B) Non-enveloped viruses
II) Steps of virus replication

19. 1) Attachment

20. 2) Penetration

21. 3) Uncoating

22. 2&3) Penetration &Uncoating

23. 4) Eclipse

24. 5) Synthesis of viral components

25. 6) Assembly

26. 7) Release

27. Exercise 2
Predict
What is the
difference between
Enveloped & Naked
in replication ?

28. Answer of Exercise 2
Attachment
Receptor on enveloped or
Receptor on Capsid
Penetration
By Fusion in enveloped and
By Endocytosis in naked

29. Note
Endocytosis

30. General Virology
5) Synthesis of
viral components

31. 5) Synthesis of viral components
 Nucleic acid replication
 Protein synthesis

32. 5) Synthesis of viral components
Anti-sense
(- strand)
sense
( +strand)
DNA dependent DNA
polymerase
(host)
T
A
C
G
C
G
C
T
C
A
T
G
C
G
C
G
A
G
Replication
A

33. 5) Synthesis of viral components
B
Transcription of
mRNA according
nucleic acid
Protein
mRNA

34. Nucleic acid talks
A
G
C
T
A
G
C
U
DNA RNA
+mRNA

35. Nucleic acid talks
A
U
G
C
G
C
U
C
U
Word (amino acid)
Word (amino acid)
Word (amino acid)
+mRNA

36. Nucleic acid talks
Positive
sense
Negative
sense
‫اشتي‬
‫اشرب‬
‫ما‬

37. Nucleic acid talks
A
U
G
G
C
G
A
G
A
‫اشتي‬
‫اندومي‬
‫بابا‬ ‫يا‬  It makes sense
+ ssRNA (+mRNA)

38. Nucleic acid talks
U
A
C
C
G
C
U
C
U
‫يتشا‬
‫يموندا‬
‫ابابااي‬
Non sense
- ssRNA (+mRNA)

39. 5) Synthesis of viral components
DNA dependent DNA polymerase
DNA DNA

40. 5) Synthesis of viral components
DNA dependent RNA polymerase
DNA mRNA

41. 5) Synthesis of viral components
RNA dependent RNA polymerase
RNA RNA

42. Exercise 3
Anti-sense
(- strand)
sense
( +strand)
Replicate & make mRNA
for the following dsDNA,
ssDNA,dsRNA, +ssRNA
& -ssRNA

43. Exercise 3
Anti-sense
(- strand)
sense
( +strand)
How the replicate will
occur and make mRNA?

44. Answer of Exercise 3
Anti-sense
(- strand)
sense
( +strand)
DNA dependent
DNA polymerase
(host)
T
A
C
G
C
G
C
T
C
A
T
G
C
G
C
G
A
G
Replication

45. Answer of Exercise 3
Anti-sense
(- strand)
sense
( +strand)
Tyr.
Ala
Pro.
copies of
+ DNA
strand
mRNA
Make mRNA?

46. Answer of Exercise 3
Anti-sense
(- strand)
sense
( +strand)
Viral
Protein
Met
Arg.
Gly.
mRNA

47. Nucleic acid talks
Act as mRNA
Start Codon
(AUG)
+ ssRNA

48. + ssRNA
Carry genetic
information
Act as mRNA
Directly translated
into protein
+ve RNA

49. - ssRNA
Cannot be
translated into a
protein
U
A
C
G
C
G
C
C
U
A
G
G
+ve
-ve
-ve +ve
 opposite sequence
to mRNA

50. dsDNA
Replication & transcription

51. dsDNA
Capsid
DNA-dependent
DNA polymerase
Copies (+) & (-)
DNA strand

52. ssDNA
Replication & transcription

53. ssDNA
Copies (+)
DNA strand
DNA-dependent
RNA polymerase
Copies (-)
DNA strand
Viral
portionTranslation
DNA-dependent
DNA polymerase

54. dsRNA
Replication & transcription

55. dsRNA
RNA-dependent RNA
polymerase (viral)
Copies (+) & (-)
RNA strand
From
virus

56. ssRNA
Replication & transcription

57. ssRNA
U
A
C
G
C
G
C
C
U
A
G
G
( strand)
RNA dependent RNA
polymerase(viral)
Copies (-) RNA strand
U
G
C
G
C
C
C
U
A
G
G
A
( strand)
Met
Arg.
Gly.
Ser.
Tyr.
Ala.
Pro.
Arg.
‫ماما‬
‫حبيبي‬

58. ssRNA replication
RNA-dependent RNA
polymerase (viral)
Copies (-)
RNA strand
(transcriptase)
RDRPV

59. ssRNA
Replication & transcription

60. ssRNA
Act as mRNA
Except HIV

61. ssRNA replication
RNA-dependent
RNA polymerase
Copies (+)
RNA strand
RNA-dependent
RNA polymerase
Copies (+) RNA
strand
Act as mRNA

62. Replication
Baltimore classification
Replication strategy
All viruses must generate
+ strand mRNA

63. Replication of viruses
III) Anti-viral drugs

64. III) Anti-viral drugs
1) Prevent attachment
2) Prevent Uncoating
3) Prevent Replication
4) Prevent release

65. 1) Inhibition of attachment

66. 2) Inhibition of Uncoating
attachment
Amantidine
Rimantadine
Uncoating

67. 3) Inhibition of Replication
DNA polymerase

68. 3) Inhibition of Replication
Block DNA
polymerase
 Acyclovir
 Ganciclovir

69. 4) Inhibition of mRNA
Ribavirin
Interferon
Transcription Translation

70. 5) Inhibition of viral release

71. 5) Inhibition of viral release
 Oseltamivir (Tamiflu)
 Zanamivir

72. Objectives
By the end of this lecture the students will
be able to:-
I) Means of replication
II) Steps of virus replication
III) Action of anti-viral drug
V) Test yourself

73. V) Test yourself

74. Q1
Monocyte
2-3 days
Eclipse period occurs in viral replication
during
Monocyte
2-3 days
Viral adsorption
Viral Penetration
Viral assembly
Transcription & Translation

75. Q2
Monocyte
2-3 days
DNA dependent DNA polymerase means
Monocyte
2-3 days
Monocyte
2-3 days
Enzyme reads DNA and builds RNA
Enzyme reads RNA and builds DNA
Enzyme reads DNA and builds DNA
Enzyme reads RNA and builds RNA

76. Q3
Monocyte
2-3 days
DNA dependent RNA polymerase means
Enzyme reads DNA and builds RNA
Enzyme reads DNA and builds DNA
builds mRNA
Enzyme reads RNA and builds DNA

77. Q4
Monocyte
2-3 days
Attachment of a virus to a host cell
requires
Fusion of virus envelope with host cell
membrane
Endocytosis
Interaction between the virus and
specific host cell receptor
Budding

78. Q5
Monocyte
2-3 days
What does mean by Positive sense RNA
SSRNA
Carry genetic material
Act as mRNA
Directly translated into protein

79. Q6
Monocyte
2-3 days
What does mean by Negative sense RNA
SSRNA
Carry reverse generic material
Can not act as mRNA
Should be converted into + sense

80. Q7
Monocyte
2-3 days
RNA-dependent RNA polymerase means
Enzyme reads DNA and builds RNA
Enzyme reads RNA and builds RNA
Enzyme reads RNA and builds DNA
Enzyme reads DNA and builds DNA

81. Q8
Uncoating step in replication is
Virus leave envelope on cell membrane
Destroy capsid in release nucleic acid
Virus attach to host cell
Translation started

82. Q9
Monocyte
2-3 days
In virus replication, fusion of the virus is
followed by
Budding
Attachment
Eclipse phase
Uncoating

83. Q10
Monocyte
2-3 days
In virus replication, Eclipse phase is followed
by
Attachment
Uncoating
Intracellular synthesis
Penetration

84. Q11
Monocyte
2-3 days
The newly viral particles are released from the
infected host cell by
Lysis
Budding
Assembly
Endocytosis

85. Q12
Monocyte
2-3 days
The newly viral particles are released from the
infected host cell by
Lysis
Budding
Assembly
Endocytosis