its about the influenza viruses, its serogroups, its transmission and aloyt of things about its genome,its replication cycle , major outbreaks of bird flu and its treatment

1. Rohama
24
Bs 4th
Presented by :
Presented to :
Dr . Shafiq

2. Bird flu

3. Outline
• What is bird flu?
• Types of influenza
• Transmission
• Subtypes
• Genome
• Virus structure
• Replication cycle
• Symptoms and treatments

4. What is bird flu?
• Bird flu is also known as avian influenza
• It is caused by type A strains of influenza
• It infects birds ,animals and humans
• Mostly infects birds
• Similar to dog flu ,swine flu and human flu
• Reassortment forms a new virus

5. Types of influenza
There are basically three types of influenza
Influenza type A
Influenza type B
Influenza type C
A virus
Source of seasonal influenza epidemics and
pandemics
Affects both animals and birds
B and C viruses
Infects human only and not cause pandemics

6. Transmission
• This influenza type A virus is present in wild aquatic birds
• Then it infects birds , animals and humans

7. Sub types of avian influenza
There are 15 subtypes
Based on
Hemagglutinin
Neuraminidase
 H5N1 infects mostly the birds

9. Genome of bird flu virus
It belongs to family orthomyxoviridae
This family contain ssRNA viruses
Influenza virus has negative stranded ssRNA
There are 8 segments of RNA

10. Virus structure

11. Replication cycle
Most common steps :
 Attachment (Adsorption)
 Penetration
 Uncoating
 Targeting
 Gene expression.
-synthesis of viral mRNA (transcription)
-synthesis of viral proteins (translation)
 Genome replication
 Virion assembly/maturation
Release of new infectious virus

12. Attachment
 HA forms spikes on the viral lipid membrane.
 These spikes of HA bind to sialic acid found on the surface of the
host membrane
Two major linkages are found between sialic acids and the
carbohydrates they are bound to in glycoproteins: α(2,3) and α(2,6)
Avians recognize the α(2,3) linkages

14. Entry and uncoating
Cell mediated endocytosis occurs
Low Ph 5 to 6
Conformational changes in HA
Open the channels of matrix proteins
Viral RNP released into the cytoplasm

15. Transcription and replication of the viral
genome
Replication of the genome does not require a primer
 The viral RNA dependent RNA polymerase (RdRp) initiates RNA
synthesis internally on viral RNA.
 This is possible, as the extreme 5’ and 3’ ends of the genome exhibit
partial inverse complementarity
 Are able to base pair with one another to form various corkscrew
configurations.

16. • Able to base pair with one another to form various
corkscrew configurations

17. Cap snatching
• Mature cellular messenger RNAs (mRNAs) have a 5’ methylated cap
and a poly(A) tail.
• The vRNPs have poly(A) tails but no 5’ caps
• It was determined that the 5’ methylated caps of the viral mRNAs
actually belonged to the cellular mRNAs
• Lead to the formulation of the “cap-snatching” mechanism

18. • The viral RdRp is made up of three viral proteins: PB1, PB2, and PA.
• PB2 has endonuclease activity.
• It binds to the 5’ methylated caps of cellular mRNAs
• Cleaves the cellular mRNAs’ 10 to 15 nucleotides 3’ to the cap
structure.
• This cellular capped RNA fragment is used by the viral RdRp to prime
viral transcription

20. • cellular RNA Polymerase II (Pol II) binds to DNA and starts transcription
During transcription initiation, serine 5 on the C-terminal repeat domain
(CTD) of Pol II is phosphorylated, leading to the activation of cellular cap
synthesis complex

21. Replication

22. Export vRNPs out of nucleus
• vRNPs appear to be exported out of the nucleus via the CRM1
dependent pathway through the nuclear pores
Assembly and budding
• Uses the host cell’s plasma membrane to form the viral
particles
• That leave the cell and go on to infect neighbouring cells
• All the viral proteins normally found within the viral lipid
bilayer, i.e., HA, NA, and M2, must be present to form a viral
particle

24. symptoms

25. Symptoms in humans

26. Treatment
World Health Organization (WHO) currently recommend antiviral drugs
• oseltamivir (Tamiflu)
• zanamivir (Relenza)
• peramivir (Rapivab)

27. vaccine
 The first vaccine in the United States for the prevention of H5N1
influenza
The vaccine was manufactured by Sanofi Pasteur
There are several hurdles to making a bird flu vaccine.
• It can take up to 6 months to produce and test each vaccine
• lack of overall production capacity
• One is the problem of scaling up production to meet demand

28. • Thank