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163 Cards in this Set
- Front
- Back
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where do RNA viruses replicate?
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in the cytoplasm of the cell (DNA viruses replicate in the nucleus)
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what is the structure of the picornoviruses?
do they have envelopes? |
small ss +RNA
"pico""rna"=small RNA no, it is a naked capsid because it needs to be resistant to acid since it infects mostly through the GI tract |
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what is the size and shape of the picornavirus virion?
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25-30 nm
icosahedral (p"ico"rnavirus is "ico"sahedral |
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what are the five major types of picornaviruses?
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enterovirus
rhinovirus cardiovirus apthovirus heparnavirus |
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what are the five major types of enteroviruses?
what larger family do the enteroviruses belong to? |
poliovirus 1,2,3
Coxsackie A 1-22, 24 Coxsackie B 1-6 Echovirus (ECHO) 1-9, 11-27, 29-34 Enterovirus 68-71 |
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what is another name for the ECHO virus?
what larger family does the echovirus belong to? |
Entero cytopathic hepatic orphan
Picornavirus |
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what is the optimum temperature for rhinovirus replication?
what is their activity at low pH? |
33 degrees celsius
Labile at acidic pH (Which is why they only infect upper RT, because they would be degraded in GI tract) |
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what conditions are enteroviruses resistant to?
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pH 3-9, heat, mild sewage treatment
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what is the genome of the picornavirus family?
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mRNA (+ strand RNA = doesn't need to be copied to other form before transcription, can be transcribed as is)
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what is the minimum picornavirus particle(s) sufficient for infection?
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just the naked RNA genome!
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most picornaviruses are _______, with the exception of heparnavirus, which causes _________.
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cytolytic
Hepatitis A |
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with which virus type is it possible to have virion paracrystals form in the cell?
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picornavirus
(because the shape is so regular = icosahedral) |
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the viral protein of picornaviruses is first transcribed into what?
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A polyprotein
-it is cleaved into enzymatic and structural proteins |
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what is the most well known and best-studied picornavirus?
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poliovirus
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the promoters of the poliovirus are made of what?
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VP1
VP2 VP3 VP4 |
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Which protein(s) is/are made from VP0 in poliovirus?
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VP2
VP4 |
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what two things is VP4 important for in poliovirus?
when is VP4 made? |
entry into cell
structure of virus Made after the genome is incorporated into the capsid. |
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what are two compounds that are used for antibody neutralization of the picronaviruses?
how do they work? |
Pleconaril
3-methylisoxazole bind to the canyon of picornavirus capsid, changing its conformation, and preventing uncoating of virus |
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what are the three different receptors picornaviruses bind to?
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ICAM-1
CD-55 PVR/CD155 |
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which picornaviruses bind to ICAM-1?
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80% of rhinoviruses
some coxsackie viruses |
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Which picornaviruses bind to CD-55?
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echoviruses
some coxsackie viruses other enteroviruses |
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Which picornaviruses bind to PVR/CD155?
what is the receptor similar to? |
Poliovirus (PVR = poliovirus receptor)
similar to receptor for herpes virus |
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what are the three ways picornaviruses hijack the host system?
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1. cleave ribosome cap binding protein EIF4-G which prevents cellular mRNA from binding to ribosome
2. inhibit transcription factors and change membrane permeability to decrease cellular mRNA synthesis and reduce ability of mRNA to bind to ribosome 3. viral mRNA can outcompete cellular mRNA for factors required for protein synthesis. |
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what does the genome of picornavirus resemble?
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mRNA
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what is the genetic locus involved in the initiation of RNA synthesis for picornaviruses?
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guanidine resistance marker (Gr)
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what two things do the proteases coded by picornaviruses cleave?
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1. the polyprotein into its individual proteins
2. the EIF4-G ribosomal cap protein (preventing cellular mRNA from binding to ribosome) |
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what is the name of the protein responsible for packing the picornavirus into the capsid and initiating viral RNA synthesis?
where is it found on the viral genome? |
VPg
found on the 5' end of viral genome |
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what are the portals of entry for enteroviruses?
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oropharynx
intestinal mucosa upper respiratory tract |
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which picornavirus is NOT resistant to stomach acids and bile?
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rhinovirus
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where is replication of enteroviruses initiated?
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in mucosal lymphoid tissue of tonsils and pharynx
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most of the receptors for picornaviruses are part of what superfamily?
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immunoglobulin receptor superfamily
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what ultimately determines the disease for picornaviruses?
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the infected tissue type
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disease symptoms for picornaviruses are usually caused by ________, not _________
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viral effects
immune system response |
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is there anythign that could prevent spreading of picornavirus in blood?
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yes, serum antibody, but it is transient and is only present from past infection or vaccine
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what is transmission of enteroviruses?
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fecal-oral route (ie) hep a)
contaminated water |
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what age group is most at risk for:
1. polio (asymptomatic to mild disease) 2. polio (asymptomatic to paralytic disease) 3. coxsackie virus and enterovirus |
1. young children
2. older children and adults 3. neonates and infants |
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what time of year are enteroviruses most common?
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summer
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what are the vaccines available for enteroviruses?
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Polio-
live oral polio vaccine (trivalent OPV) Inactivated trivalent polio vaccine (IPV) other enteroviruses- NONE |
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how common is wild type polio in US?
what other forms can occur? |
Eradicated due to vaccine
vaccine related cases due to reversion of live vaccine to reestablish neurovirulence |
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what is the incubation period for enteroviruses?
which type has the shortest incubation period? |
1-35 days
viruses that affect oral and respiratory sites (bc they have short distance to travel) |
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is coxsackie A more severe in adults or infants?
Coxsackie B? |
adults
coxsackie B is particularly harmful to neonates (same with enterovirus 11) |
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what is herpangina caused by?
what are some manifestations of the disease? |
Coxsackie A
vesicular ulcers on soft palate |
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what are the four main different types of polio infection?
Which is most common? |
Asymptomatic illness
Abortive poliomyelitis (minor illness) Nonparalytic poliomyelitis (aseptic meningitis) Paralytic polio (major illness) asymptomatic polio is most common (90%) |
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what are the symptoms of abortive poliomyelitis?
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fever
malaise vomiting headache sore throat |
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what does the poliovirus infect in paralytic polio?
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Anterior horn cells of spinal cord
motor cortex of brain |
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what are the two types of paralytic polio?
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paralytic poliomyelitis
-asymmetrical paralysis with no sensory loss (85% caused by poliovirus 1) Bulbar poliomyelitis -more severe, may involve muscles of pharynx, vocal cords, and respiration. |
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is herpangina a herpes infection?
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NO
caused by several serotypes of Coxsackie A |
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what is Hand, Foot, and Mouth disease caused by?
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Coxsackie A
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What is pleurodynia?
what causes it? what is it also known as? |
acute illness with sudden fever, unilateral low thoracic, pleuritic chest pain.
Caused by Coxsackie B Devil's grip |
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which picornavirus causes myocardial and pericardial infections?
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Coxsackie B
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what are teh symptoms of aseptic meningitis? what's it also known as?
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headache and signs of meningeal irritation (including nuchal irritation)
Nonparalytic poliomyelitis |
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what is composition of CSF in poliovirus or enterovirus aseptic meningitis?
how is it different than bacterial meningitis? can the virus be found in the CSF? |
lymphocytic pleocytosis (more than usual)
No neutrophils Not normally |
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can coxsackievirus and echoviruses be isolated from CSF in patients with meningitis?
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yes (polio usually can't)
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what are the 2 drawbacks of the polio vaccines?
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1. Immunocompromised people may get infected by live virus
2. small potential for virus to revert back to infectious form and cause paralytic disease (1 in 4 million compared to 1 in 100 people in wild type) |
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what are the vaccines for echoviruses and coxsackie viruses?
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There are none!
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what is the most common cause of common cold and upper RT infections?
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rhinoviruses
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what causes runny nose during rhinovirus infection?
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infected cells releasing bradykinin and histamine
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what time of year is rhinovirus infection most common?
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early fall and late spring
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what is structure of coronavirus?
what is most famous coronavirus? |
Helix of +ss RNA
-nucleocapsid protein A -E1 -E2 most famous is SARS-CoV (causes SARS) |
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do coronaviruses have an envelope?
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yes, lipid bilayer derived from intracellular membranes (golgi) of host cell with E1 and E2
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what are the three major structural proteins of coronavirus?
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E1
E2 Nucleocapsid protein N |
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which protein on coronavirus envelope actually binds to receptor on cell?
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E2
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how many phases are there in replication of coronavirus genome?
what are they? |
2 phases
Early phase -RNA polymerase (L) Late phase -from negative sense mRNA template. -structural and nonstructural proteins |
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where in the cell does the coronavirus assemble?
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in the RER
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what is method of choice for detection of Coronaviruses?
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RT-PCR
-detection of viral RNA genome |
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where does coronavirus usually replicate?
Why? |
the upper respiratory tract (SARS is upper RT infection)
because its optimum temperature is 32-35 degrees celsius |
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is there a vaccine for Coronaviruses?
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NO
-if there was then we would have been vaccinated after SARS outbreak |
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what type of genomic material is coronavirus?
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ss + RNA
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what virus has the structural proteins nucleocapsid protein N, E1, E2?
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coronavirus
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is coronavirus enveloped?
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yes, lipid bilayer envelope from ER
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where does coronavirus assemble inside a cell?
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in the RER
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what are the two phases for translation of coronavirus, and what does each involve?
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1. Early phase - produces RNA polymerase
2. Late phase - from negative sense RNA template - structural and non structural proteins |
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what is appearance of coronavirus?
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solar "corona" (halo) - like appearance
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what is the method of choice to detect coronaviruses?
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RT-PCR in respiratory and stool samples
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which virus requires biosafety level 3 (BSL-3) conditions for isolation?
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coronavirus (SARS-CoV)
CoV = CoronaVirus |
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where does coronavirus infect?
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epithelial cells of upper Respiratory Tract
(SARS = Severe acute RESPIRATORY syndrome) |
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what temperature does coronavirus replicate best at?
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33-35 celsius
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can reinfection of coronavirus occur in the presence of serum antibodies?
why? |
Yes,
because the glycoprotein "corona" (E1 E2 N) helps it survive the GI tract |
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is SARS helped or worsened by inflammatory responses?
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Worsened bc inflammation in upper RT is not good
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what are the two forms of coronavirus?
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1. common cold form
2. SARS-CoV |
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how do you control the two most common forms of coronavirus?
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1. common cold form - difficult but unnecessary due to mildness of infection
2. SARS-CoV - screening when outbreak occurs and quarantine of infected individuals |
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what are the three major viruses in the calicivirus family?
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1. Norovirus
2. Astrovirus 3. other small gastroenteritis viruses (Hep E) |
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what family does norovirus belong to?
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calicivirus
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what is the prototypical norovirus called?
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norwalk virus
(found in norwalk ohio) |
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are noroviruses enveloped?
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NO
("no"rovirus = "no" envelope) |
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are noroviruses resistant to detergents, drying, and acid?
why? |
yes
-no envelope |
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how are noroviruses transmitted?
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Fecal-oral route by contaminated food
(norwalk ohio is asshole of world. asshole=fecal) |
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what does infection with norovirus cause?
for how long? |
gastroenteritis
48 hrs without serious consequences |
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what is structure of norovirus genome?
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+ sense RNA
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what two things does the genome of norovirus have on it?
what other virus is this similar to? |
1. VPg protein
2. 3' terminal poly-A sequence Picornovirus |
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what is typical structure of caliciviruses?
how is norovirus different? |
typical - six-point star shape or cup shaped indentations
norovirus - round with ragged outline |
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what do you use to distinguish norovirus from others?
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antibodies from seropositive people
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how many norovirus virions are needed to initiate disease in humans?
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as little as 10!
highly infectious bc it has naked capsid and no envelope |
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what is the major symptom of norovirus infection?
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Watery diarrhea (part of gastroenteritis virus family)
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how long can norovirus be shed after symptoms have stopped?
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up to 2 weeks after
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what do noroviruses cause in jejunum?
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blunted villi
cytoplasmic vacuolation infiltration of mononuclear cells |
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are there histologic changes in gastric mucosa with norovirus?
what may happen? |
no
gastric emptying may be delayed, causing vomiting (since the only way out is back up) |
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what is the most resistant out of:
1. poliovirus 2. norovirus 3. rotavirus |
Norovirus
-resistant to 60 celsius heat -pH 3 -detergent -chlorine levels in treated drinking water |
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how do you treat infection of norovirus?
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no specific treatment known.
treat symptoms with pepto bismo minimize outbreaks by good sanitary practices with food and water supply |
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what five things do lab methods do for virus studying?
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1. describe Cytopathologic Effects of virus (CPEs)
2. detect viral particles with electon microscope 3. isolate and grow virus 4. detect viral components (proteins, enzymes, genomes) 5. evaluate patient's immune response to virus (serology) |
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what is influenza and what is it characterized by?
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viral infection of the lungs
characterized by fever, cough, and severe muscle aches |
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what two things is influenza NOT?
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1. a low grade fever and sniffles that keeps you home in bed for a day
2. a GI upset (no such thing as "stomach flu") |
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what groups are most susceptible to influenza infection?
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elderly and infirm
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how many types of influenza are there?
which is most common? |
3 types
A, B, C A is most common |
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what two glycoproteins are found on Influenza virus envelope?
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HA (hemagluttinin)
NA (Neuraminidase) |
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how many nucleocapsid segments are there in influenza A and B?
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Eight segments!
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what two other proteins are found on outside of influenza other than HA and NA?
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M1 (matrix protein lines internal surface)
M2 (membrane protein) |
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where are all the proteins of influenza encoded on in comparison to one another?
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each encoded on separate segments
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what is structure of Hemagluttinin?
what virus has it? what 3 things does it do for the virus? |
Trimer
Influenza has it 1. promotes fusion of envelope to cell membrane 2. hemagluttinates RBCs 3. elicits Ab response |
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What is structure of Neuraminidase?
what virus has it? what does it do? |
Tetramer
Influenza has it cleaves sialic acid on glycoproteins of viron, preventing clumping and causing release of virus from cell |
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which Influenza protein is responsible for binding and fusion of virus?
what about release? |
HA
NA |
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What do the drugs Oseltamivir and Zanamivir target?
what are they also called? when are they used in regards to onset of symptoms? |
They target NA of Influenza
Oseltamivir = tamiflu Zanamivir = relenza used after onset stopping release of more virions |
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is Influenza virus enveloped?
what is the structure of its genome? |
yes, enveloped
8 - RNA nucleocapsid segments |
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where in cell does influenza virus transcribe and replicate its genome?
where does it assemble and bud from? |
in nucleus
from plasma membrane |
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what virus are the drugs amantidine and rimantadine used for?
what do they target? when are they used in course of infection? |
used for influenza
target M2 (membrane protein) used early, bc they inhibit uncoating step |
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which influenza drugs can only be used for type A?
what about A and B? |
only type A = amantidine and rimantidine
A and B = Oseltamivir and zanamivir |
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what promotes genetic diversity by mutation and reassortment in influenza virus?
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segmented nucleocapsid! (8 segments)
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which proteins are used to differentiate between the diff types of influenza?
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M1
M2 NP |
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where does influenza A and B infect?
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upper and lower RT
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what are the systemic symptoms of influenza a and b caused by?
local symptoms? |
interferon and lymphokine response to virus
epithelial cell damage by virus |
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what two things are important for immune resolution and immunopathogenesis?
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1. Interferon
2. cell mediated immune response (T-and NK-cells) |
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are people with influenza infection more susceptible to bacterial infection?
why? |
yes, because their protective barriers are compromised or broken down by influenza
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what influenza proteins are antibodies made against?
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HA
NA |
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what two influenza A proteins can undergo
Major (reassortment: shift) and minor (mutation: drift) antigenic changes? |
HA
NA |
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what are the two antigenic changes that influenza A virus can undergo?
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Major = reassortment = shift
Minor = mutation = drift |
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does Influenza B undergo antigenic changes?
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yes, but minor compared to influenza A
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what four characteristics are used to classify Influenza A virus?
which one is left out for Influenza B? why? |
1. type (A B C)
2. place of orig. isolation 3. date " " " " 4. Antigen (HA and NA) No HA or NA classification for B because there isn't as much antigenic shift or variation |
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what antigenic change is responsible for pandemics?
endemics? |
Major = reassortment = shift
minor = mutation = drift |
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what facilitates reassortment of HA and NA genes in animals simultaneously infected by two separate subtypes?
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the fact that they are encoded by separate RNA molecules
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what group is mostly responsible for spread of influenza virus?
what time of year is most common? why? |
schoolchildren
wintertime most common bc it likes cool, less humid atmosphere |
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is influenza resistant to dryness, acid, and detergents?
why? |
No
envelope |
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can Influenza a infect more than just humans?
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yes!
coinfection in animals is responsible for reassortment |
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how is Influenza virus transmitted?
|
inhalation of small aerosol droplets
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what often comes first?
symptoms or transmission of virus? |
transmission of virus
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are epidemics local or worldwide?
pandemics? |
local
worldwide |
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who is most at risk for influenza virus infection?
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Elderly and immunocompromised (including children)
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what are the two different types of flu vaccines?
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1. inactivated virus particles
2. purified HA |
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how many major strains do the flu vaccine carry?
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3 major strains
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what causes influenza strains to emerge that are no longer controlled by people's residual immunity?
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antigenic drift = mutation
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what are the three unique features of reovirus?
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1. double-layered capsid environ
2. double stranded RNA 3. 10-12 ds RNA nucleocapsid segments |
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what two RNA viruses have segmented nucleocapsids?
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1. influenza
2. reo/rotovirus |
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when rotaviruses and orthoreoviruses (reoviruses) are cleaved by mild proteolysis to intermediate subviral particles, are they more or less infectious?
|
MORE,
also called "infectious" subviral particles |
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where does viral replication of reo/rotovirus occur?
where does double stranded RNA remain? |
cytoplasm
inner core |
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which RNA virus has a double capsid?
|
Reo/rotovirus
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how is reo/rotovirus released from cell?
|
cell lysis
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what are the two major proteins on outside of reo/rotovirus?
|
VP4 - major attachment protein
VP7 - major capsid component |
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how is reo/rotovirus spread?
|
fecal-oral route
possibly respiratory route |
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how does reo/rotovirus affect different age groups
|
can be significant in infants <24 months
ASYMPTOMATIC in adults!! |
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what does reo/rotovirus affect intestinal cells?
causing what? |
Lyses them (bc thats how it's spread)
causes loss of electrolytes and prevents reabsorption of water |
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when are large amounts of reo/rotovirus released?
|
during diarrheal stage
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do proteolytic enzymes such as trypsin enhance or reduce infectivity? why?
|
enhance,
because they cleave rotavirus into infectious subviral particles |
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what makes rotaviruses so stable?
|
double capsid!!
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what protein of rotavirus acts in toxin like manner to promote calcium ion influx into enterocytes?
|
NSP4
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what does immunity to reo/rotavirus require?
|
IgA in lumen of gut
to VP4 and VP7 |
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is reo/rotavirus resistant to environmental and GI conditions?
why? |
yes
double capsid |
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rotavirus group A infects what age groups?
rotavirus group B? |
A = infants and young children
B = infants, older children, adults |
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what time of year is rotavirus/reovirus most common?
|
autumn
winter spring (not summer = too warm) |
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what are the two modes of control of rotaviruses?
|
1. live vaccines with reassorted virus
2. handwashing and isolation of known cases |
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what is the method of choice for diagnosis of rotavirus?
why? how else can it be diagnosed? |
direct detection of viral antigen
bc most infected patients have large quantities of virus in stool electron microscopy immunoelectron microscopy |
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do many people have rotavirus specific antibody?
how much of a rise is needed for diagnosis? |
yes, many people have it
four-fold rise in Ab is needed for diagnosis |
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what is the antiviral therapy available for rotavirus?
|
there is none!
|
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when is rotavirus usually acquired in life?
|
early!
|
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what is the morbidity and mortality associated with rotavirus attributed to?
what is purpose of supportive therapy for it? |
dehydration and electrolyte imbalance
replacement of fluids |
