Virology 15 Picornaviruses*
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- What are the three major genera within the human Picornaviruses?
-
Enteroviruses
Rhinoviruses
Hepatoviruses - Why do you care about Picornavirus RNA?
- Picornavirus RNA is infectious
- What does the Picornavirus genome consist of?
-
A single open reading frame producing a long polyprotein precursor
(AS DOES HCV!) - What does a mature Picornavirus Protomer consist of?
- Four proteins: VP 1, 2, 3, 4
- Why is there no single neutralizing antibody against all picornaviruses
- The receptor binding site is located in a “canyon†on the capsid surface such that it is inaccessible to neutralizing antibodies. This may be why there is no single neutralizing antibody against all picornaviruses (the lining of the canyon wall can also mutate)
- Why are Picornaviruses considered highly stable?
-
Picornaviruses are
resistant to:
Drying
70% Ethanol
5% lysol - What determines the predominant disease caused by an enterovirus
- The target tissue infected by the enterovirus
- How many types of poliovirus are there?
- 3 serotypes of poliovirus (1, 2, and 3) but no common antigen
- Initial replication of poliovirus occurs in the gut followed by:
- Viremia
- What are the 3 possible outcomes of poliovirus infection?
-
Subclinical infection (90-95%)
Abortive infection (4-8%)
Major illness (1 - 2%) - How does the abortive infection of poliovirus present
- A minor influenza-like illness occurs, recovery occurs within a few days and the diagnosis can only be made by the laboratory. The minor illness may be accompanied by aseptic meningitis
- How does the major illness in poliovirus infection present
- The major illness may present 2 - 3 days following the minor illness or without any preceding minor illness. Signs of aseptic meningitis are common. Involvement of the anterior horn cells lead to flaccid paralysis. Involvement of the medulla may lead to respiratory paralysis and death
- What are the two types of polio vaccine
-
Salk (killed): immunosupressed patients; raises serum antibody levels but not local or gut immunity; given as multiple doses
Sabin (attenuated): For all three polio serotypes - Coxsackieviruses are distinguished from other enteroviruses by their
- Pathogenicity for suckling rather than adult mice
- What Coxsackieviruses cause herpangina, hand foot and mouth disease, and acute hemorrhagic conjunctivitis
- Group A members
- What Coxsackieviruses cause mild or fatal encephalitis in infants, cardiomyopathy, aseptic meningitis, and pleurodynia
- Group B members
- What type of diseases do Group A Coxsackieviruses produce
- A diffuse myositis with acute inflammation and necrosis of fibers of voluntary muscles
- What type of diseases do Group B Coxsackieviruses produce
- Focal areas of degeneration in the brain, necrosis in the skeletal muscles, and inflammatory changes in the dorsal fat pads, the pancreas and occasionally the myocardium
- Describe hand-foot-and-mouth disease
-
Caused by coxsackie A virus.
Lesions initially appear in the oral cavity and then develop within 1 day on the palms and soles. - Describe Enterovirus 70
- The causative agent of epidemics of acute hemorrhagic conjunctivitis that swept through Africa, Asia, India and Europe from 1969 to 1974. The virus is occasionally neurovirulent
- What Picornaviruses are associated with paralytic disease
- Most commonly associated with polioviruses but other enteroviruses may also be responsible, enterovirus 71
- What Picornaviruses are associated with meningitis
- Caused by all groups of enteroviruses, most commonly seen in children under 5 years of age.
- What is Picornavirus-induced encephalitis associated with
- Focal or generalized encephalitis may accompany meningitis. Most patients recover completely with no neurological deficit
- Undifferentiated febrile illness is associated with what Picornaviruses
- May be seen with all groups of enteroviruses
- Hand-foot-mouth disease is associated with what Picornaviruses
- Usually caused by group A coxsackieviruses although group B coxsackieviruses and other enteroviruses have caused outbreaks
- Herpangina is associated with what Picornaviruses
- Caused by group A coxsackieviruses
- Epidemic Pleurodynia (Bornholm disease) is associated with what Picornaviruses
- Normally caused by group B coxsackieviruses
- What are the most common causes of viral meningitis in all age groups?
- Enteroviruses including Coxsackie A and B and Echoviruses
- What are the basic characteristics of the Picornaviruses
-
Single stranded positive RNA
Naked
Icosahedral
One of the smallest viruses - What immune system molecules are required to prevent viremia in polio infection
- Serum antibodies
- What are the characteristics of viral meningitis
-
WBC counts not elevated
Protein near normal levels
Gram stain reveals nothing
Culture reveals nothing