Viral CNS infections Flashcards
What are the three types of virus within the picornavirus family?
- Enterovirus - i.e. poliovirus / coxsackievirus
- Rhinovirus
- Hepatovirus - i.e. Hep A
What is the primary structural difference between Entervirus/Hepatovirus and Rhinovirus?
Entero/Hepato are resistant to low pH and grow optimally at normally body temp (can pass thru stomach and live in GI tract)
Rhinoviruses are labile to low pH, but grow at 33 C in the URT and have aerosolic transmission
What is the present in the 5’ UTR (untranslated region) of picornaviruses?
“Clover leaf” called Internal Ribosome Entry Site (IRES) which takes the place of the 5’ cap of RNA and controls translation
What is the VPg protein?
Protein linking to the 5’ end of viral RNA of picornaviruses, provides the polyU primer for RNA synthesis
What is the function of the 3’-UTR in picornaviruses
Controls RNA synthesis
What are P1-P3 and what is their general function?
Picornaviruses synthesize all their proteins from one polyprotein via open reading frame, which are then cleaved (total of 11-12 proteins)
P1: Viral capsid proteins
P2: Protein processing proteins
P3: Genome replication proteins
What receptor do picornaviruses use, and specifically what receptor does polio use?
Wide variety of host cell surface receptors
Polioviruses use a single Pvr (polio virus receptor)
Where do picornaviruses replicate?
In the cytoplasm
What is the mechanism of RNA replication in picornaviruses?
Use +RNA genome to make -RNA strand from which multiple +RNA’s are made (via RNA-dependent RNA polymerase)
What protein encodes the RNA-dependent RNA polymerase in picornaviruses?
3D
What must the 3D protein work in conjunction with to function?
VPg - which provides the polyU primer for RNA synthesis
What three loci encode viral proteases?
L, 2A, and 3C
Where does poliovirus try to replicate?
The lymphoid tissue of oropharynx and gut - i.e. tonsils, cervical nodes, Peyer’s patches, mesenteric nodes
What is the difference between transient and major viremia?
Transient - virus momentary passes through bloodstream to reach other lymphoid tissue
Major - no protective antibody is made, allowing for virus to reach various organs and ultimately invade CNS
What part of the CNS does polioviral replication occur? What can this lead to?
Mainly gray matter, especially the motor neurons in the anterior horn of the spinal corn. In severe cases, this can lead to flaccid paralysis
Where does poliovirus get excreted?
In the feces
What are the two types of poliovirus vaccines and which one is more effective in elliciting a long-term response?
- Salk - inactivated - given intramuscularly
2. Sabin - live, attenuated - given orally and most protective / longest term response
Why is eradication of polio very possible?
Humans are the only reservoir, vaccine is stable and easy to transfer with long-lasting immunity
What are three conditions caused by Cocksackie A virus?
- Hand-foot-mouth disease - statue of David with birds eating from hand food and mouth (rash)
- Aseptic meningitis - child shooting David with gun with a meningitis helmet on
- Herpangina - fever + ulcers on tonsils and palate (HFMD - HF)
What are the major viruses within the flavivirus family?
Yellow Fever virus, Dengue Fever virus, West Nile virus, Japanese Encephalitis, St. Louis Encephalitis, and Hepatitis C
Why is hepatitis C often given its own subdivision within the Flavivirus family?
All other flaviviruses use a 5’ cap for their +sense RNA
Hepatitis C is a “hepacivirus” - uses IRES-mediated translation similar to picornaviruses