1   Structural  Virology   Lecture  4   Pavel  Plevka   2   Assembly  and  exit  of  virions  from  cells   1.  A?achment   2.  Entry   3.  TranscripCon   4.  TranslaCon   5.  Genome  replicaCon   6.  Assembly   7.  Exit   3   Assembly  of  helical  viruses   Tobacco  mosaic  virus   (TMV)   4   Effects  of  pH  and  ionic  strength  on  formaCon   of  TMV  capsid  protein  aggregates   5   TMV  iniCaCon  of  assembly   6   TMV  assembly  (GMO  tobacco)   7   Assembly  of  icosahedral  viruses   8   Picornavirus  assembly   9   Adenovirus  assembly   10   dsDNA  virus  genome  packaging   11   Herpesvirus  portal  structure   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   12   Podoviridae  phage  assembly   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   13   T4  assembly   14   AcquisiCon  of  a  virion  envelope  by  budding   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   15   ComplementaCon  of  enveloped  viruses   16   HIV  assembly  and  maturaCon   17   Retrovirus  budding   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   18   Assembly  and  maturaCon  of  dengue  virus   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   19   Structure  of  alphavirus   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   20   Structure  of  iridovirus   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   21   Summary  of  virus  membrane  acquisiCon   22   •  describe  the  assembly  mechanisms  for   nucleocapsids  with  (a)  helical  symmetry  and   (b)  icosahedral  symmetry   •  discuss  the  origins  of  internal  virion   membranes  and  of  virion  envelopes     •  explain  the  roles  played  by  membrane/matrix   proteins  in  the  budding  of  some  enveloped   viruses     •  describe  mechanisms  used  by  viruses  to  exit   from  cells   Learning  outcomes   23   Outcomes  of  virus  infecCon  for  the  host   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   24   Outcomes  of  virus  infecCon  for  the  host   Reasons  for  non-­‐producCve  infecCon:    -­‐  latent  infecCon    -­‐  aborCve  infecCon     Persistent  infecCons:    -­‐  producCve  (HIV)    -­‐  latent  (herpesviruses)     Factors  affecCng  outcomes  of  infecCon:    -­‐  host  immune  system    -­‐  “quality”  of  the  virus  (mutaCons,  suitable  host)   25   Innate  immunity   26   Components  of  innate  immunity   -­‐  Complement   -­‐  Interferons   -­‐  Natural  Killer  (NK)  cells   -­‐  APOBEC3  protein  complex   -­‐  tetherin   27   AcCvaCon  and  regulaCon  of  complement  system   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   28   Complement  effector  system   29   Interferon  acCon   Interferon  effects:   Alpha  and  beta    -­‐  acCvaCon  of  expression  of   anCviral  proteins:  dsRNA   dependent  protein  kinase  R;   tetherin    -­‐  producCon  of  MHC  I  and   proteasome  components   (presentaCon  of  pepCdes  for   control  by  T  cells)    -­‐  acCvaCon  of  NK  cells    -­‐  inducCon  of  apoptosis   Gamma    -­‐  produced  by  cells  of  immune   system    -­‐  acCvaCon  of  phagocytes  and  NK   cells   Many  viruses  inhibit  producCon  of   interferons  in  infected  cells.   30   AcCviCes  of  Natural  Killer  (NK)  cells   Recognize  infected  cells   Use  perforins  to  kill  cells   Induce  apoptosis   Many  viruses  produce  proteins  or   microRNAs  that  reduce  response  to   NK  cells.   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   31   APOBEC3  proteins   Vif  protein  of  HIV  induces   degradaCon  of  APOBEC3.   32   Tetherin   33   AdapCve  immunity   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   34   AnCbody  structure   35   AnCbody  structures   36   ProducCon  of  virus-­‐specific  anCbodies   37   AnCviral  effects  of  anCbodies   •  Neutrophils  and  macrophages  have  IgG  Fc   receptors  -­‐>  phagocytosis  of  infected  cells  and   inducCon  of  apoptosis   •  NK  cells  have  IgG  Fc  receptors  -­‐>  killing  of  infected   cells.   •  AnCbodies  can  induce  genome  release  from   virions  (poliovirus,  EV71).   •  PrevenCon  of  receptor  binding   •  Release  of  virions  a?ached  to  cells   •  InhibiCon  of  cell  entry  (fusion  proteins)   •  InhibiCon  of  genome  uncoaCng   •  AcCvaCon  of  complement   NeutralizaCon  of  viruses  by  anCbodies   E18  Fab   E19  Fab   Control  50nm   Electron  density  levels   (arbitrary  units)   E18   E19   E18  Fab   E19  Fab   Electron  density  levels   (arbitrary  units)   43   RecogniCon  and  killing  of  infected  cell  by   cytotoxic  T-­‐cell   Helper  T  cells   Cytotoxic  T  cells  (MHC  I)   44   RNA  silencing   •  FragmenCng  of  dsRNA  by   DICER  (producCon  of   21-­‐25bp  fragments  with   2-­‐3nt  3’  overhangs)   •  AcCvaCon  of  RISC  (RNA  – induces  silencing  complex)   •  DestrucCon  of  mRNAs   Many  plant  viruses  produce  proteins   that  inhibit  RNA  silencing.   45   Maintenance  of  genomes  during  latent  infecCon   Retroviruses   Polyoviruses,   Papillomaviruses   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   46   Signals  that  induce  acCvaCon  of  latent  infecCons   •  A  eukaryoCc  host  cell  moves  into  another  phase  of   the  cell  cycle   •  The  host  cell  is  irradiated  with  ultra-­‐violet  light.   (phages,  herpes  simplex  virus)     •  A  host  organism  becomes  immunocompromised.   (herpes  simplex  virus)     •  The  host  cell  becomes  infected  with  a  second  virus   that  provides  a  funcCon  that  the  first  virus  lacks.   (satellite  virus  and  helper  virus)   47   ProducCve  infecCons  in  plants   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   48   Disease   Virulence  of  a  virus  strain   Dose  of  virus     EffecCveness  of  immune  system  (age,  nutriConal   status,  previous  training)   Human  intervenCons     Virus  eliminaCon  x  latent  infecCons   49   •  describe  the  major  components  of  innate  and   adapCve  immunity  in  vertebrates   •  outline  the  process  of  RNA  silencing   •  explain  programmed  cell  death   •  explain  the  terms    ◦  producCve  infecCon      ◦  non-­‐producCve  infecCon      ◦  latent  infecCon    ◦  aborCve  infecCon    ◦  defecCve  virus   •  discuss  the  spread  of  virus  infecCons  within  animal   bodies  and  within  plants   •  discuss  the  factors  that  determine  whether  virus   infecCon  results  in  disease   Learning  outcomes   50   Virus  classificaCon   51   PhyogeneCcs  trees   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   52   Nomenclature   53   (David)  BalCmore  virus   classificaCon   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   54   •  evaluate  the  tradiConal  criteria  used  to  classify   viruses  into  families  and  genera   •  write  family  and  genus  names  in  the  correct   format   •  explain  how  genome  sequence  data  are  used  to   classify  viruses   •  evaluate  phylogeneCc  trees   •  explain  the  basis  of  the  BalCmore  classificaCon   of  viruses   Learning  outcomes   55   Herpesviruses   John  B.  Carter  and  VeneCa  A.  Saunders   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   56   Figures     Chapter  11   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   57   58   Latent  infecCon   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   59   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   60   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   61   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   62   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   63   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   64   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   65   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   66   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   67   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   68   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   69   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   70   ©  2012  John  Wiley  &  Sons  Ltd.   www.wiley.com/college/carter   71