Enteroviruses

Enteroviruses
Presentation by: Dr. J. David Gangemi

OBJECTIVE: Review of enterovirus biology, pathogenesis, and immune response to infection
KEY WORDS: Polioviruses, echoviruses, coxsackie A & B viruses, enteroviruses, aseptic meningitis, paralytic disease, Salk vs Sabin vaccines,herpangina, pleurodynia, myocardiopathy

Outline of Major Teaching Points

I. BACKGROUND
II. CLASSIFICATION
III. BIOLOGICAL PROPERTIES
IV. VIRAL PATHOGENESIS
V. IMMUNITY
VI. DISEASE


Picornaviridae Rhinoviruses Enteroviruses Heparavirus
1) Echoviruses
2) Coxsackie viruses
3) Polioviruses

Cardiovirus Apthovirus
Enterovirus Prototype: “Poliovirus”
Diseases Associated with Enterovirus Infections

1. Non-specific Febrile Illness
2. Perinatal Infection
3. Febrile Disease With Rash
4. Meningitis
5. Myocarditis
6. Hepatitis
7. Pleurodynia
8. Poliomyelitis

I. BACKGROUND

The enteroviruses have been among the most intensively studied of all human pathogens. The war on poliomyelitis produced many breakthroughs in the science of virology (Salk/Sabin/Enders and Weller).


II. CLASSIFICATION
General Features Used For Taxonomy
III. Biological Properties
IV. VIRAL PATHOGENESIS

* Virus enters the body through the mucosa of the oropharynx and upper respiratory tract, then begin to multiply in the tissues around the oropharynx.
* Because the Enteroviruses are stable in acid they are able to pass through the stomach into the intestines, where they undergo further rounds of replication.
* Roughly at the same time as it reaches the intestine, the virus begins to spill into the systemic circulation. This early (primary) viremic phase is usually asymptomatic and involves fairly low titers of virus in the blood.
* During the primary viremia, tissues are seeded according to the tropism of the virus as determined by Vp1
* In the case of the polioviruses, the tissues infected include neurons, especially the anterior horn cells of the spinal cord

V. IMMUNITY

* Antibodies can be detected in the circulation by the seventh to tenth day after exposure, roughly the same time as the symptomatic disease and secondary viremia occur.
* With the exception of the gastrointestinal tract, viral replication in tissues soon slows to a halt. In contrast, gastrointestinal tract viral multiplication and fecal shedding can continue for weeks after the development of high neutralizing antibody titers.

VI. Disease
The Enteroviruses:

o Cause a variety of clinical syndromes, with a great deal of overlap among the different serotypes
o Viral tropism, as determined by the Vp1 capsid protein, ultimately determines tissue involvement and the clinical syndrome which each serotype can cause

Aseptic Meningitis

Symptoms- headache, neckache, rigidity of neck and back, malaise

Cause- while several viruses can cause aseptic meningitis (enteroviruses, mumps, lymphocytic choriomeningitis, herpes, etc.), there are other causes of nonpurulent meningitis (chlamydia, leptospira). Certain other bacteria and fungi may also cause nonpurulent spinal fluids but with altered chemistry compared to viral meningitis.

Poliomyelitis
* Poliovirus was once thought to be the main cause of paralysis before the advent of polio vaccines
* Poliovirus did account for a large portion of paralytic cases but many cases were caused by other agents or were due to unknown causes

Poliomyelitis: Disease Characteristics
Poliomyelitis: Prevention Diseases Associated with Coxsackie Viruses

Enteroviruses.ppt