Influenza H1N1 A: A close insight

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Influenza H1N1 A A close insight

• Dr. Mustafa Ababneh
• Molecular Virologist

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Outlines

• Virus structure, proteins and functions
• Influenza A replication
• Influenza A Reassortment
• Identification of reassortment
• Alignment of Current H1N1 influenza viruses , and
  between H1N1 and H5N1.
• Mutational effects

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Virus charateristics

• Orthomyxoviridae Family
• Has a segmented negative-sense, single-stranded
  RNA viruses
• total genome length is 12000-15000 nt.
• 16 H antigens (H1 - H16) and 9 N antigens (N1 -
  N9), which can be found in all possible
  combinations.
• The nucleoprotein antigen (A, B, C) determines
  the virus type. The HA and NA antigens determine
  subtypes.
• Influenza virus A
• both antigen shift and antigen drift noted. High
  antigenic variability in the surface
  glycoproteins HA and NA. Has 8 segments.
• Influenza virus B Members infect only humans
  associated with epidemics antigenic drift noted.
  Has 8 segments
• Influenza virus C human and swine, Has 7
  segments.

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Replication of orthomyxovirus

• Replication starts with the binding of HA protein
  to the sialic acid receptors
• Then penetration and uncoating
• Genome Replication takes place in the nucleus
• Cap-snatching
• NOT in the cytoplasm

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Antigenic variation

• Antigenic shift
• These are the major changes based on the
  reassortment of segments of the genome. In the
  reassortment entire segments of RNA can be
  exchanged between two or more viruses infecting
  the same host cell.
• Antigenic drifts these are minor changes caused
  by point mutation in the genes encoding HA or NA
  glycoproteins

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• Antigenic shift will render the resulting virus
  the ability to cross species barriers.
• Antigenic drift will render the virus to transmit
  efficiently between the same species. RNA
  dependent RNA polymerase

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Influenza Reassortment
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Reassortment in H1N1 influenza A
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How we can Know the reassortments events
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Multiplex RT-PCR identification of reassortment
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Influenza A

• Current circulating strains are H1N1 and H3N2
• Human subtypes include H1N1, H3N2, H1N2, and H2N2
• Avian subtypes include H1 to H16 and N1 to N9
• Bird ? human H5N1, H9N2, H7N7, H7N2, H7N3

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H1N1 sequence database
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H1N1 genes sequences
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Sequence similarity between current H1N1 and H5N1
(Jordan-2006)

• Alignment was done with ClustalW, lasergene DNA
  analysis Software.

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Sequence similarity between current H1N1 isolates
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Mutational analysis

• Amino acid markers of host specificity ,Does
  Influenza H1N1 A has the markers?
• Tamiflu resistant Mutation
• NS1 mutation- glutamic acid in position 92.

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• by compare the amino acids sequences of all
  influenza pandemic strains.
• If positions 87 NS1, 103 NS1, 207 NS1 and 63 NS2
  contains Human Amino acid this means the virus
  will be cross to human from other species.

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Tamiflu resistant H1N1

• H275Y
• Histidine to tyrosine subsiotiution in the
  neuraminidase active site (H 275Y in N1 )
• Detection by sequencing.
• The current H1N1 still Tamiflu sensitive

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Tamiflu reseistant H1N1
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Tamiflu resistant mutation in current H1N1
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Tamiflu resistant mutation in Human H1N1 (Human
strain)
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NS1 H5N1 (D 92 E)
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NS1 H5N1 (D 92 E)
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NS1 of H1N1 (D 92 E)
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Refernces
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• Thank you

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