BIO315 Chapter 8: Poliovirus & Other Enteroviruses
What % of poliovirus infections cause a major illness, such as flaccid paralysis?
Less than 1%
poliovirus infects:
MOTOR NEURONS (not sensory)
In 1942, the Kenney Institute opened in:
Minneapolis
Dilated cardiomyopathy
disease of the <3 muscle that causes the <3 to become enlarged & to pump less strongly - the <3 becomes thin, weak, or floppy, & is unable to pump blood efficiently around the body causing fluid to build up in the lungs, which leads to congestion & the feeling of breathlessness. - this has been associated w/ certain Coxsackievirus infections
Serotype
groups w/in a species of virus that share distinctive surface structures, such as different antigens
poliovirus can be present in:
human feces for 3-6 weeks
Where do enteroviruses multiply?
in the mucosa of the gut
+ssRNA genome of poliovirus is
infectious
severe form of poliomyelitis:
inflammation & destruction of neurons in the gray matter of anterior horn of SC
serotype 2
least likely to cause paralysis
Peyer's patches
lymph nodes in walls of intestines near the junction of the ileum & colon
major viremia causes:
minor symptoms
Characteristic of Enteroviruses
most infections occur during childhood & tend to produce life-long immunity.
serotype 1
most likely to cause paralysis
infants
mostly those in diapers, the most efficient transmitters of infection
How are the ubiquitous pathogens of the enteroviruses transmitted?
person-to-person via an oral-fecal route
mouth
portal of entry for polioviruses
Autocleavage
process by which protease cleaves itself
vaccine-associated paralytic polio
rare occurrence of poliomyelitis in a person who received the OPV
polioviruses spread through:
regional lymph nodes to the blood
the 5' end of poliovirus genome forms a clover leaf or tRNA like structure that plays a key role in:
replicative process of RNA molecule
paralytic poliomyelitis
severe inflammation that can destroy motor nerves & resulting paralysis can be permanent
polioviruses replicate in:
the anterior horn cells of the SC
Rhinoviruses are restricted to replication in cells of
the respiratory tract
once poliovirus attaches to receptor:
the viral capsid enters host cell via ENDOCYTIC PATHWAY
~95% of all poliovirus infections are
asymptomatic
Bulbar Poliomyelitis
characterized by muscle weakness, impairing a persons ability to talk or swallow - eventually, lung muscles are paralyzed, requiring the need for an iron lung or respiratory to aid in breathing
chemical inactivation of enteroviruses is achieved via:
chlorine, HCl, aldehydes; heating at 122*F for 1 hr in absence of calcium & magnesium can inactivate enteroviruses
Bulbospinal Poliomyelitis
combination of bulbar & spinal paralysis
PPS
condition that affects polio survivors years after recovery from an initial acute infection by poliovirus - most common symptoms: muscle weakness & fatigue & muscle atrophy
WHAT PROPORTION NEEDS TO BE VACCINATED?
- % OF PEOPLE WHO NEED TO BE VACCINATED = 1 - GOAL R0 / EXISTING R0 IN CASE OF POLIO: 1 - (1/6) = 5/6 83% PEOPL E TO BE VACCINATED IN ORDER TO CONTROL THE INFECTION!
What is R0?
- R0 = # of new infections that can be caused by an existing infection. - Mainly in a susceptible population - What is minimal % of people in that area that need to be vaccinate.
OPV
- developed 1961 by Sabin - consists of mix of live, attenuated strains of all 3 virus serotypes - administered orally to infants 2-18 months of age w/ syrup, water, or milk or on cake, break, or a sugar cube
IPV
- developed in 1955 by Salk - consists of 3 killed strains of virus - given via intramuscular injection
Poliomyelitis
- infectious disease caused by enterovirus that's spread by oral-fecal route of transmission - in severe cases, symptoms may involve the weakening or paralysis of the muscles of the lungs & extremities of its victims - this is rare today because of vaccination efforts
Enterovirus Genome
- naked - ss+RNA genome packed w/in a small icosahedral capsid
What viruses make up the Picornaviridae family?
- polio - hep A - foot-and-mouth-disease virus
potential roadblocks to global eradication:
- poliovirus is contagious - IPV inefficient in preventing spread of virus - OPV us in tropical countries is problematic - tensions between those who favor mass vaccination & those who don't - verification of success is hard since poliovirus infections are NOT clinically obvious.
UTR
- section of viral or celluar mRNAs that's not translated by cellular ribosomes into protein - usually located at the 5' or 3' ends of viral mRNAs - may contain a hairpin structure at 5' end of a viral mRNA called the IRES
PVR
- transmembrane protein belonging to Ig superfamily of proteins - serves as a cellular receptor for poliovirus entry into host cells
In the US, a nationwide vaccination program using the Salk vaccine began in:
1955
How many types of enteroviruses have been determined to cause recognizable infectious diseases?
20
incubation period for poliomyelitis:
6-20 days; can range from 3-35 days
convalescent serum
Ab-rich serum obtained from a convalescing patient
After viral +ssRNA genome is 1st released into the cytoplasm of the cell it:
Acts as a messenger RNA
Enteroviruses can be inactivated by:
Aldehydes
Amantadine
An antiviral drug that blocks the M2 ion channel function of influenza A viruses, resulting in the incomplete release of the viral ribonuclear proteins through interference w/ the uncoating step of its replication cycle.
Which form of poliomyelitis results in the destruction of nerves involved in speaking, swallowing, and breathing, often necessitating use of an iron lung?
Bulbar - bulbar poliomyelitis causes muscle weakness, impairing a person's ability to talk or swallow. - Eventually it may cause paralysis of breathing, in which case an iron lung or respirator may be required - less common than spinal poliomyelitis.
What was the 1st enterovirus discovered AFTER poliovirus?
Coxsackie viruses
cDNA
DNA that's synthesized from viral RNA genome that acts as a template to copy the RNA into this - rxn is catalyzed by RT - RT is produced by all retroviruses, including HIV & hep B virus
infection with 1 serotype ___________ confer immunity against a different serotype.
DOES NOT
A mother brings her 3-year-old son to the family pediatrician. The child initially presents with a fever, headache, and neck pain. A few weeks later the child is admitted to the hospital due to severe difficulty breathing and unexplained paralysis of his left leg. Which of the following viruses is most likely to be the cause of this child's symptoms?
Enterovirus D68
As of 2015, countries in Arica & the Middle East were polio-free.
FALSE
Polio virus infection can be cured using anti-viral drugs.
FALSE
Poliovirus is one of the most thoroughly investigated viruses of all time, and its molecular mechanism of action is well known.
FALSE
Poliovirus isolation in culture is no longer used to diagnose poliomyelitis.
FALSE
Potential roadblock to global eradication was identified as the lack of an animal reservoir.
FALSE
The Salk Vaccine in rare cases can cause poliomyelitis, a situation termed vaccine-associated paralytic polio.
FALSE; OPV by Sabin
Gamma globulin was an effective early polio prophylactic.
FALSE; it was INEFFECTIVE
Only a small % of poliovirus infections are asymptomatic.
False; up to 95% are asymptomatic
most enteroviruses infect & replicated in the
GI tract
GOAL OF INFECTION IS TO:
HAVE R0 VALUE LESS THAN 1; TO STABILIZE OR ERADICATE!
Initiation of translation of the poliovirus poly-protein is dependent on which of the following?
IRES
What are hospital acquire infections?
NOSICOMIAL INFECTIONS
Due to low childhood vaccination rates and political unrest, _____________ remains one of the last remaining polio-endemic countries accounting for the majority of wild-type poliovirus infections.
Pakistan - accounts for 85% of all WT-poliovirus infections in 2014; this possess the continuous risk of spreading poliovirus infections as infected individuals move to other areas.
What family do the viruses of the Enterovirus genus belong to?
Picornaviridae family
Individuals who have recovered from paralytic polio can experience new muscle pain and weakness decades later due to:
Post-poliomyelitis syndrome (PPS)
What is the R0 for polio?
R0 < 1: - Existing: 00 - New: 0 - New/Existing : ½ = 0.5 <1 - When R0 is less than 1, the infection will not replicate any further & it can die out or be eradicated R0 = 1: - Existing: 00 - New: 00 - New/Existing 2/2=1 - When R0 value is 1, the infection can be stable For polio; R0 = 5 to 7: - R0 > 1 --> 00: 00000000: 8/2 = 4 - If greater than 1, it is an infection that is common to spread
Respiratory Enteroviruses
Rhinoviruses triggering asthma
The live, attenuated vaccine developed by Dr. Sabin included:
Serotypes 1, 2, 3
The polio virus is carried by the bloodstream to the:
Spinal Cord
At least 100 viruses w/in the Enterovirus genus are known to infect humans.
TRUE
Enteroviruses are transmitted from person to person by an oral-fecal route.
TRUE
Enteroviruses are transmitted from person to person via an oral-fecal route.
TRUE
In neutralization assays, Ab are added to a virus preparation.
TRUE
Nonhuman primates and humans are the sole natural hosts for the poliovirus.
TRUE
Polio viruses are naked and small.
TRUE
Post-poliomyelitis syndrome (PPS) occurs in a large portion of individuals who recover from paralytic poliomyelitis.
TRUE
Sister Elizabeth Kenney's new theory for treating paralysis emphasized "re-education" of muscles.
TRUE
The 1st step toward identifying host receptors involves the isolation of monoclonal Ab.
TRUE
T/F: Not all enteric viruses are enteroviruses.
TRUE!
Rhinoviruses are restricted to replication in cells of:
The respiratory tract
Flaccid paralysis
a loss of voluntary movt because weakness or loss of muscle tone tone has caused damage to nerves in the muscle (e.g., as a result of poliovirus infections)
Hand-foot-mouth disease
a virulent disease caused by enterovirus 71 & coxsackie viruses. - it's common in infants & children - symptoms: fever, sores in mouth, & blisters on the hands & bottoms of toes - self limiting, lasting 7-10 days
Spinal poliomyelitis
asymmetrical paralysis on one side of the body - the lower SC is infected by poliovirus, resulting in paralysis of the legs