Week 4 Micro Notes

Week 4 Micro Notes - Lecture 23: Polio and other...

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Lecture 23: Polio and other Enteroviruses Major groups of picornaviruses and their constituent viruses: Picornaviruses: o Non-enveloped, + sense RNA viruses with icosahedral capsule Protein capsid w/ 4 viral proteins forming the capsid RNA + sense: Polyadenylated Can be translated in the cell o Pico = small picornavirus = small RNA virus o Includes diseases range from common cold to polio o Acid stability Enteroviruses and hepatoviruses are stable at acid pH able to survive at gastric acidity & get to lower GI tract Rhinoviruses are not acid stable and limits them to URT o Thermal stabilities Rhinoviruses replicate at lower temperature and restricts them to the nasal passages Hepatoviruses more heat stable Feces remain infected after excretion Major clinical diseases associated with other enteroviral infections o Enteroviral meningitis (common) & encephalitis (uncommon) o Paralytic polio-like syndrome (Coxsackie A7) o Herpangina (Coxsackie A) Ulcerations on the palate o Hand-foot-mouth disease (Coxsackie A) Painful ulcerations on mouth, feet, bands in children o Myocarditis and pericarditis (Coxsackie B) o Pleurodynia (Coxsackie B) o Hemorrhagic conjunctivitis (Enterovirus 70 & Coxsackie A24) Caused by the listed viruses Poliovirus: Non-enveloped virus with outer protein capsid o VP (viral protein): VP 1, 2, 3 on exterior & VP 4 not exposed to the surface o Made into a pentamer o RNA is in the middle to protect it o Outer surface, or canyons, contains receptor binding Poliovirus binding and entering cell o Poliovirus receptor is CD155 Transmembrane protein with adhesion like properties Contains Ig like repeat domains Fits into a cleft (canyon) between the VP 1 and 2 proteins o Poliovirus attaches to receptor and is endocytosed Capsid undergoes conformational change release VP4 RNA passes across membrane and into the cytoplasm Poliovirus replication cycle o Binding and insertion of RNA into cytoplasm first step o Replication takes place in the cytoplasm; not in nucleus o + sense RNA is polyadenylates and serves as translation template Translated into viral proteins RNA-dependent RNA polymerase is made Made not brought into cell Copies it into negative strand serves as templates for more + strands o More + RNA is either packaged or enters back into replication cycle o Capsid proteins are also translated and assembled in cytoplasm Precursors cut by proteases Cell lyses to release it o NOTE : infected cells show polio induced membrane vesiculation Presence and formation of vesicles Protein translation and proteolytic processing o Proteolytic processing: polyprotein precursor cleaved by proteases o Viral RNA: VPg instead of 5’ methylguanosine CAP structure Internal ribosome entry site at the 5’ end Allows for translation of cytoplasmic RNA due to lack of packing enzymes to put the cap on VPg does not have to do with translation
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This note was uploaded on 09/14/2011 for the course PHARM mb taught by Professor Staff during the Spring '11 term at UCSD.

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Week 4 Micro Notes - Lecture 23: Polio and other...

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