Avian influenza (Bird flu)

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Avian influenza (Bird flu)
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??? 2005.11.03
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The migration of birds(1)

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• 1.??resident??????????
• 2.??migrant ???????????????????? ????????
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• 3.??straggler
• 4.???wander

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The migration of birds(2)

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• ????
• ????energy storage??????
• ????neuroendocrine?? longer
  sunshine?pineal body ?hypotituitary
  gl.?corticosteroids, prolactin? physical
  prepiration for sexual gl.growth increase the
  ability of localization
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The migration of birds(3)

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• 1. ??????????
• 2.????
• ?????3070km/hr
• ????68hr/dayx3040km/hr200280km
  ???,??,??(????)??
• 3.????
• ????1000m,???????300m,?? ???30006300
  ,???????9000m
• ??????,???????,??????

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The migration of birds(4)

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• 1.visual orientationsun,stellar,landmark
• 2.non-visual orientationgeomagnetic,acoustic
  
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• ???(?,?,?)????
• ???????( landbridges,?????)
• ???--???
• ??-----??
• ??-----???

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Types of influenza viruses

• Type A8 separate gene segments
• infect people,birds,pigs,horses,seals,w
  hales,etc
• natural hostswild birds
• subtypes15 HA(hemagglutinin),9NA(neuram
  inidase,sialidase)
• birds are hosts to all
  known subtypes
• other animal species
  are to certain subtypes
• both antigenic drift(endemic) and
  antigenic shift(pandemic)
• Type B8 separate gene segments
• infect normally humans
• type changesonly antigenic
  drift(endemic),different strains
• Type C7 separate gene segments
• only cause mild illness in humans

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Influenza C virus
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H5N1 virus(golden color ones)
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Structure of influenza viruses

• enveloped, pleiomorphic (vary their size and
  shape), typically spherical with a constant
  diameter of 100 nm if filamentous, particles
  retain a constant diameter(of 100 nm) but vary in
  length( up to several micrometers )
• Similar internal components,markedly different
  constituent of their envelopes
• Influenza A and B produce 10 proteins from 8 RNA
  segments,yet differ in ion channel (tetrameric M2
  encoded by M gene vs. NB encoded by NA gene )
• Influenza C single glycoprotein (
  haemagglutinin-esterase-fusion, HEF,
  glycoprotein) functional replaces both HA and NA,
  ion channel CM2,genome consisting 7 segments

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MorphologyHA 135 A0 trimerNA 60 Ao tetramer
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The HA molecule with fusion sites indicated(1)
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SuperXP a.uncleaved HA0,b.cleaved BHA,with
R-binding- siteC.conformational TBHA2
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SuperXP The receptor binding site on the virus
is a pocket that is not exposed to the immune
system
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Biological significance of receptor-binding
specificity

• 1.different viruses infect different species
• viruses from humans recognize
  a(2,6)linkages(pentasaccharide)
• viruses from avians/equines----
  a(2,3)linkages(penrasialoside)
• viruses from swine recognize both LSTc and
  LSTa
• first years of the Asia H.K.pandemics,virus
  es with either a(2,6)- or a(2,3)-recognition
  specificity were identified?a gradual change in
  specificity(nature of sialic linkage on cells)
• the failure of the outbreak of H5 avian
  flu,1997,---the inappropriate a(2,3)- receptor
  binding specificity of the virus involved
• mucins from human lung are rich in
  a(2,3)-linked sialic acis?inhibit cell receptor
  recognition by a(2,3)linkage-specific HAswhile
  equine fluids are rich in nonspecific inhibitors
  containing sialic acid in a(2,6)linkage (soluble
  inhibitors)

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• 2.similar selection process during virus
  replication in different cells in
  vitroinfluenza surveillance and vaccination
• the HAs of viruses from humans with a(2,6)
  linkage recognition specificity, function
  effectively in hen egg infections
• obtained material for analysis the
  virusesgrown either in mammalian cells or
  embryonated hens eggs?diferent systems result in
  the propagation of related but distinguishable
  viruses
• the covariation of differences in
  antigenicity receptor-binding specificity
  location of the conserved receptor-binding site
  is closely surrounded by antigenically important
  variable residues occasionally influence
  receptor-binding affinity or specificity

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SuperXP Overlaid images of alpha(2,6)-and
alpha(2,3)-linked sialypentasaccharides LSTc and
LSTa,respectively,in the HA receptor binding site
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Antigenic variation

• 1.HAs of H.K. pandemic isolated between 1968
  1999 amino acid substitutions at a rate of 3.5
  residues/year
• 60/101 of the changes detected are
  retained in HAs in subsequent years
• 57/60 (between residues HA1 50 and
  280) involved residues on the membrane-distal
  surface of HA, whereas 2/3 of those not
  retained(27/41) are buried
• retained substitutions selected for
  preventing Abs recognition
• 2.Antigenicity oligosaccharide attachment
• carbohydrate side chains are
  antigenically self
• during antigenic driftcreat new
  attachment sites in Ab- binding regions

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• 3.Antigenic subtypes
• avian species15 HA,9 NA
• equines H3,H7
• humans H1,H2,H3H5 in 1997/H9 in
  1998 in small no.
• swine H1,H2,H3,H9
• HA1 more variable than HA2(antigenic
  properties)

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HAoHA precursor cleavage?generate C terminals of
HA1 N terminals of HA2?required for membrane
fusion activity infectivity

• 1.extracellular cleavageserine protease,tryptase
  Clara
• 2.intracellular cleavage(more efficient)H5 H7
• subtilisin-like enzymes(wide tissue
  distribution) active in the post-translational
  processing of hormone growth factor
  precursors---?more virulent more widespread

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History of influenza viruses

• Influenza A
• 1930sfirst isolated ,H1N1present in
  the pandemic 1918 strain
• 1958antigenic shift,H2N2
• 1968antigenic shift,H3N2,remained the
  most prevalent in recent years
• 1970sco-circulating influenza
  H1N1,probably from a laboratory source
• Influenza Bnot been given the same H N
  designation,represent a minor population of
  circulating viruses in humans
• Influenza Cmild respiratory illness
• Avian fluvia mixing vessel(pigs)
  19971998H5Hong Kong avian flu
  
  2003H7N7Holland

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SuperXP History of influenza antigenic
drift/shift
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Instances of Avian Influenza Infections in
Humans confirmed instances in AI viruses
infecting humans since 1997

• H5N1,HK,1997HPAI, 18 hospitalized,6 died1.5
  million chickens are slaughtered
• H9N2,China and HK,1999LHAI
• H7N2,Virginia,2002one person
• H5N1,China and HK,2003HPAI,one recovered,the
  other diedanother family member died in China
  without testing
• H7N7,Netherlands,200378/89 conjunctivitis
  only,5/89 with conjunctivitis,cough,fever,muscle
  aches,2/89 flu-like illness only,4/89 other,1/89
  died
• H9N2,HK,2003LPAI,a child,recovered
• H7N2,NY,2003one person,recovered
• H7N3,Canada,2004HPAI with conjunctivitis
• H5N1,Thailand and Vietnam,2004,and other
  outbreaks in Asia during 2004 and 2005HPAI

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Influenza catastrophe

• 1918, Spanish flu,H1N1
  20millions expired
• 19571958,Asian flu,H2N2 12 millions
  expired
• 19681969,Hong Kong flu,H3N2 700 thousands
• 1997now H5N1 67
  persons expired
• 
  140millions poultry
  slaughtered

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SuperXP Drifterror prone transcriptase that
copies the vRNA Shiftchange in viral genome
caused by the swapping of bird/animal gene
segments for human segments
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SuperXPpH56 pH activated ion-channels made up
of M2 protein are also important in uncoating
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Replication
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Genomehighly conserved
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Host defenses

• INF signals for cells to produce PKR which
  inactivates eLF2 and inhibits protein
  synthesis(muscle aches,fatigue,fever are
  associated with the efficient induction of INF)
• ButInfluenzas NS1 protein binds to dsRNA which
  keeps PKR inactivated
• Anti-HA Abs (most important) bind and stay with
  the virus as it makes its way through the cell
  and somehow interferes with the replication
  process(viral clearance)
• Anti-NA Abs stop the molecule from shaving off
  the sialic acid residues

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SuperXP Type IINF-alpha(leukocyte
INF),INF-beta(fibroblast or epithelial INF)Type
IIINF-gamma(immune)
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SuperXP Host defensefirst humoral,following
cellular
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Species barriersialic acid present on the virus
glycoproteins

• Human viruses HA226leu, HA228Ser
• Avian viruses HA226gln, HA228Gly
• Pigs and birdsmixing pot,important reservoirs,
  generating pools of genetically/ antigenically
  diverse viruses,get transferred back to human
  population via reassortment

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Treatment of influenza

• Targets adsorption,nucleic acid replication,
  nucleocapsid assembly
• Problems with developing drugs
• the drug must get inside the bodies
  cells hard to get broad spectrum agents,there
  are many strains of influenza to target
• virus replication may decline before
  symptoms occur
• difficult to establish in vitro assays
• difficult to achieve selective toxicity
  since viruses share many pathways with their
  host cells
• Neuraminidase inhibitors for both flu A B
  (reduce one day duration) Tamiflu(oseltamivir
  phosphate,GS4104 ,capsule), Relenza(zanamivir,inha
  led)
• Target on matrix protein(M2,only for flu A)
  Amantadine,Rimantadine (prophylatic)
• Vaccine phase I phase II clinical trials
• H5N1April,2005 1.Aventis
  Pasteur Inc. of Swifwater,PA(8000 doses)
• (Vietnamese patient,Feb.2004) 2.Chiron
  Corporation of Emeryville,CA(10000 doses)
• H9N2

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SuperXP Block virus enry across the endosomeand
also interfere with virus release
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SuperXP Depiction of interaction of Relenza (GG
167) in the neuraminidase binding site
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SuperXP Relenza bound to neuraminidase clump
viruses
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Influenza vaccines

• Whole virus vaccinesinactivated forms of virus
  with the predicted HA,are grown in embryonated
  eggs
• Subunit vaccinesuses both HA and NA subunits
  extracted from recombinant virus forms
• Split-virus vaccinespurified HA(lessens the side
  effects)
• Recommended for health care workers,elderly
  people in nursing home,asthmatics,chronic lung
  disease patients,some pregnant women,and anyone
  who is susceptible to infection

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SuperXP Influenza vaccine
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SuperXP Louis Pasteur 18221895 FIRST VACCINE
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SuperXP
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What would happen to Taiwan?

• Disaster may happen between JanMar 2006
• Estimated 5 millions infected
• 70 thousands hospitalized
• 14 thousands expired----if
  not well- prepared
• CDC recommended Tamiflu storage10 of
  national population,yet right now under 4
• incubation period37 days?23 days
• Every August next May,20 strains of migrant
  birds visit Taiwan

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Genetic characterization of H5N1 avian flu
viruses isolated in south China during the
2003-04 AI outbreaks

• Cambodia.China,Indonesia,Japan,Laos,South
  Korea,Thailand, Vietnam
• 53 samples(tracheal and cloacal swaps, trachea,
  lung, spleen, pancreas,kidney,spleen,brain)
  collected from Guangdong Province,isolated 12
  strains of H5N1 AIVs
• HA1- HA2 connecting peptide
• Ck/GD/174/04 RRRKKR (basic amino
  acids,motif)
• Ck/Gd/178/04,Ck/GD/191/04,A/duck/China/E31
  9.2/03 loss of an amino acid K at the fifth
  position
• Dk/Gd/173/04RRKKR( lost the R residue at
  the first position)
• NS1
• all the 4 isolates have Asp at the 92
  position
• Isolates originated from subgroup from
  reassortment between territorial AIVs such as
  H9N2 and H5N1,H6N1
• A possible active reassortment occurred between
  H5N1 and H6N1 AIVs and generated novel H5N1
  AIVs,seeds for future flu pandemics
  

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???????where there are human beings,there are
viruses