Enteroviruses and Poliovirus Vaccines Flashcards
Enteroviruses
- Enterovirus genus of the Picornaviridae family
- ( + ) ss RNA icosohedral naked
- worldwide distribution
Enteroviruses Transmission
- Fecal-Oral transmission
- Infection of the intestinal tract epithelial and lymphoid tissues and shed into feces
Enteroviruses are resistant to…
…acidic pH (pH 3.0), detergents and many disinfectants, including 70% alcohol.
[] and [] are active against enteroviruses.
Formaldehyde and hypochlorite are active against enteroviruses.
Enteroviruses Replication
- Replicate at 37oC
- Enteroviruses (Picornaviruses) replicate in the cytoplasm by using +RNA replication strategies
Enteroviruses and IRES
•Shut off host cell protein synthesis by destroying mRNA capping complex and allowing ribosomes to bind on the internal ribosomal entry site (IRES) located on viral RNA
Enteroviruses cause…
…paralytic disease, mild aseptic meningitis, exanthems, myocarditis, pericarditis, nonspecific febrile illness.
Enterovirus Disease - Polio Transmission
•fecal-oral route
Enterovirus Disease - Polio Season
- Poliovirus is stable in environment, stomach acid
- Infections peak late summer in temperate regions, more young people infected but less severity
Enterovirus Disease - Polio Primary Site of Infection
- Virus enters oropharynx and multiplies in mucosa; shed in oral secretions and swallowed
- Multiply in intestines——>brief viremia; usually asymptomatic; recovery often occurs
Enterovirus Disease - Polio Incubation
•Incubation period ranges from 4 - 35 days (usually 7-14 days)
Enterovirus Disease - Polio Pathogenesis
Enterovirus Disease - Polio 3 Types
- Abortive poliomyelitis
- Aseptic meningitis
- Paralytic poliomyelitis
Enterovirus Disease - Abortive poliomyelitis
- nonspecific febrile illness
- 2-3 day duration
- no signs of CNS localization
Enterovirus Disease - Aseptic meningitis
- nonparalytic poliomyelitis
- stiff neck, back and pain
- recovery is rapid (within few days)
Enterovirus Disease - Paralytic poliomyelitis
- Occurs in less than 2% of infections
- It is the major possible outcome of infection, often preceded by a period of minor illness, sometimes with 2 or 3 intervening symptoms-free days
- Signs of meningeal irritation
- Asymmetric flaccid paralysis with no significant sensory loss is the hallmark
- variable forms; in most serious forms all four limbs may be completely paralyzed or the brainstem may be attacked followed by paralysis of cranial nerves and muscles of respiration (bulbar polio)
- temporarily damaged neurons regain their function
- recovery begins and may continue for 6 months
- paralysis persisting after this time is permanent
Polio Immune Response
- Antibodies appear about day 10, same time as symptoms; neutralizing antibodies protective, block virus binding to host cell and subsequent infection
- If immune response contains the disease, tissue replication stops but intestinal shedding can continue for weeks even with high antibody titers
- Cell mediated immunity occurs, but viral proteins are not found on the plasma membranes of infected cells
Polio Diagnosis
Polio Prevention
- Development of tissue culture for viral growth made possible the two polio vaccines in the 1950s
- Killed vaccines (Salk) stimulates IgG antibodies that can eliminate the virus during viremia
- Live attenuated vaccine (Sabin) stimulates IgA response, blocks enteral spread, inexpensive, can revert to virulence, few cases every year mostly due to vaccination (1 per 2.4 million doses distributed)
- Trivalent vaccine (3 major polio serotypes)
Common Enteroviral Diseases
•Coxsackieviruses (A and B), Echovirus and Enterovirus
Common Enteroviral Diseases Incubation
•Unapparent infections most common (most people have antibodies), incubation period: 2-14 days
Common Enteroviral Diseases Infections
- Aseptic meningitis most common infection
- Most serious in infants, self limiting (4 to 14 days)
- Sometimes accompanied by encephalitis, which can lead to permanent neurologic sequelae
- Enteroviruses cause the majority of nonbacterial CNS infections in the U.S. with severe disease in infants/children and people with weakened immune system than adults
Cocksackie A
- Exanthems (Rubella-like rash), also caused by enterovirus 71 Roseola infantum, or maculopapular exanthems, but may also appear as vesicular or hemangioma-like lesions
- Hand-foot-and-mouth disease (HFMD), which usually affects children younger than 5 years of age and is characterized by fever
- Herpangia (vesicles in mouth) blister-like sores in the mouth (herpangina) and a skin rash
- Conjunctivitis
- Some group A coxsackieviruses may cause gastro-intestinal syndrome in severely immunocompromised patients
