Capsid consist of 60 identical units – capsomers. 5 protomers constitute a pentamer. Every capsomer is consist of 4 for different proteins – VP1, 2, 3, 4.
After uncoating, the genome RNA functions as mRNA and is translated into one very large polypeptide called noncapsid viral protein 00. This polypeptide is cleaved by proteases in multiple steps to form both the capsid proteins of the progeny virions and several noncapsid proteins including the RNA polymerase that synthesizes the progeny RNA genomes. Picornaviruses have positive RNA. So, purified viral RNA (without the capsid protein) can enter and replicate in the cell and . It is “infectious RNA”.
Replication of the genome occurs by synthesis of a complementary negative strand, which then serves as the template for the positive strands. Some of these positive strands function as mRNA to make more viral proteins, and the remainder become progeny virion genome RNA.
Assembly of the progeny virions occurs by coating of the genome RNA with capsid proteins. At first, procapsid (without RNA) forms. After that viral RNA enters to procalsid and assembly of mature virion is finished. Virions accumulate in the cell cytoplasm and are released upon death of the cell.
The picornavirus family includes 3 group of medical importance: the enteroviruses, the hepatovirus and the rhinoviruses. EV and HV infect primarily the enteric tract, whereas RV are found in the hose and throat (hence their name). EV and HV replicate optimally at 37 0 C, whereas RV grow better at 33 0 C, in accordance with the lower temperature of the nose. EV and HV are stable under acid conditions, which enables them to survive exposure to gastric acid, whereas RV are acid-labile.
Abortive p. is the most common clinical form. Most patients recover spontaneously. Nonparalytic P. manifests as ……. This also usually recover spontaneously.
The prefix ECHO is an acronym for enteric cytopatogenic human orphan. Although called “orphans” because they were not initially associated with any disease, they are now known to cause a variety of diseases such as:
Due to mass vaccination spread of poliomyelitis is reduced to 1998 if compare it with 1988.
Doctor should take material that contain a agent of disease.
Assembly of the picornaviral virion Formation and assembly of capsid proteins Procapsid Viral RNA Provirion Finishing of virion proteins formation Matured virion
Different properties of enteroviruses, hepatoviruses and rhinoviruses Rhinitis, respiratory infection No 33 0 C Upper respiratory tract Rhino-viruses Hepatitis A Diseases Yes Yes Stableness under acid conditions (pH3-5) 37 O C 37 O C Optimal temperature of replication Enteric tract Enteric tract Primarily infected tissue Hepato-virus Entero-viruses Property
Modern classification of enteroviruses Enterovirus 68,70 Human enterovirus D (HEV-D) Coxsackie А types 1, 11, 13, 15, 17-22, 24 Human enterovirus C (HEV-C) Coxsackie А-9, Coxsackie В types 1-6, ЕСНО types 1-7,9,11-21,24-27, 29-33; Enterovirus 69 Human enterovirus B (HEV-B) Coxsackie А types 2-8, 10, 12, 14, 16; Enterovirus 71 Human enterovirus A (HEV-A) Polioviruses 1, 2, 3 types Polienterovirus (PEV) Past name Species
Diseases caused by enteroviruses Fever, chest pain, and signs of congestive failure Myocarditis, pericarditis Vesicular rash on the hands and feet and ulceration in the mouth Hand-foot-and- mouth disease Aseptic meningitis, mild paresis and transient paralysis. Upper respiratory infections and minor febrile illness with or without rash. Both CAV and CBV Fever and severe pleuritic-type chest pain Pleurodynia Coxsackie-viruses B (CBV) Fever, sore throat and tender vesicles in the oropharynx Herpangina Coxsackie-viruses A (CAV) Paralysis Poliomyelitis Polioviruses Symptoms Disease Viruses
Poliomyelitis in an ancient civilization Poliomyelitis is an acute enteroviral infection of the spinal cord that can cause neuromuscular paralysis.
Abortive poliomyelitis. Mild, febrile illness with headache, sore throat, nausea, and vomiting.
Nonparalytic poliomyetitis. Aseptic meningitis with fever, headache, and a stiff neck.
Paralytic poliomyelitis. Flaccid paralysis is the predominant finding but brain stem involvement can lead to life-threatening respiratory paralysis. Painful muscle spasms occurs. The motor nerve damage is permanent.
Isolation the viruses in cell culture and suckling mice (for Coxsackie A viruses) and identification in neutralization test with specific antiserum
Testing serum samples (from patient) for observing a rise in titer of antiviral antibody
CPE caused by polioviruses Native Vero cells CPE – full destruction of cell monolayer after virus multiplication
Differentiation of enteroviruses - + ЕСНО + ( spastic ) + Coxsackie В + ( flaccid ) + Coxsackie А + + Polioviruses Paralysis in newborn mice CPE in cell culture Virus
Diagnosis of Coxsackievirus infection Native suckling mice Mouse with flaccid paralysis of back extremities Mice is affected by virus Flaccid paralysis in newborn mice caused by Coxsackievirus A 10
IPV - inactivated (killed) vaccine (made by Salk in 1954).
IPV is inactivated by formalin
OPV – attenuated (live), oral vaccine (made by Sabin in 1955-1958).
OPV is made using selection technology
Both OPV and IPV contain 3 serologic types .
Important features of poliovirus vaccines Yes No Affords secondary protection by spread to others Yes No Induces local intestinal immunity (IgA) Yes Yes Induces humoral immunity (IgG) Yes No Interrupts transmission Yes Yes Prevents disease Live (Sabin) Killed (Salk) Attribute
Important features of poliovirus vaccines Longer Shorter Duration of immunity Yes No Requires refrigeration Oral Injection Route of administration Yes No Can cause disease in the immunocompromised Yes No Reverts to virulence Yes No Interferes with replication of virulent virus in gut Live (Sabin) Killed (Salk) Attribute