PicornavirusesPicornaviruses

Eva L. Dizon M.D.,F.P.P.SEva L. Dizon M.D.,F.P.P.S

ObjectivesObjectives

1.To describe picornaviruses as to its 1.To describe picornaviruses as to its characteristics, genome, structurecharacteristics, genome, structure

2. To know the different genus and species 2. To know the different genus and species of family picornaviridaeof family picornaviridae

3. To know the process of replication of 3. To know the process of replication of picornavirusespicornaviruses

4. To know the different diseases caused 4. To know the different diseases caused by picornaviruses as to mode of by picornaviruses as to mode of transmission, pathogenesis, signs and transmission, pathogenesis, signs and symptoms, diagnosis , treatment and symptoms, diagnosis , treatment and preventionprevention

PicornavirusPicornavirus Picornaviruses are among the most diverse Picornaviruses are among the most diverse

(more than 200 serotypes) and 'oldest' (more than 200 serotypes) and 'oldest' known viruses (temple record from Egypt ca. known viruses (temple record from Egypt ca. 1400 B.C.). 1400 B.C.).

FMDV was one of the first viruses to be FMDV was one of the first viruses to be recognized - Loeffler and Frosch 1898. recognized - Loeffler and Frosch 1898.

Poliomyelitis as a viral disease was first Poliomyelitis as a viral disease was first recognized by Landsteiner and Popper, 1909 recognized by Landsteiner and Popper, 1909 (though the virus was not isolated until the (though the virus was not isolated until the 1930's.1930's.Name: 'Pico Name: 'Pico (Greek = very small)(Greek = very small) RNA RNA Viruses'.Viruses'.

FamilyFamily GenusGenus SpeciesSpeciesPicornaviridaePicornaviridae EnterovirusesEnteroviruses Poliovirus, Poliovirus,

Enterovirus, Enterovirus, Coxsackie,EchovirCoxsackie,Echovirusus

HepatovirusesHepatoviruses Hepatitis AHepatitis A

RhinovirusRhinovirus Human Human RhinovirusRhinovirus

CardiovirusCardiovirus EncephalomyocarEncephalomyocarditis virusditis virus

AphtovirusAphtovirus Hand foot and Hand foot and mouth virus Omouth virus O

ParechovirusParechovirus Human Human parechovirusparechovirus

ErbovirusErbovirus Equine rhinitis B Equine rhinitis B virusvirus

KobuvirusKobuvirus AichivirusAichivirus

TeschovirusTeschovirus Porcine Porcine teschovirusteschovirus

Classification + sense RNA Classification + sense RNA virusesviruses

GenomeGenome The genome consists of one s/s (+)sense The genome consists of one s/s (+)sense

RNA molecule of between 7.2kb (HRV14) to RNA molecule of between 7.2kb (HRV14) to 8.5kb (FMDV). 8.5kb (FMDV).

Genomic RNA is infectious (~1x106-fold less Genomic RNA is infectious (~1x106-fold less infectious than intact particles, although infectious than intact particles, although infectivity is increased if the RNA is infectivity is increased if the RNA is introduced into cells by transfection) - introduced into cells by transfection) - CHARACTERISTIC OF (+)SENSE RNA CHARACTERISTIC OF (+)SENSE RNA VIRUSES !!! VIRUSES !!!

There is a long (600-1200 base) There is a long (600-1200 base) untranslated region at the 5' end (important untranslated region at the 5' end (important in translation, virulence and possibly in translation, virulence and possibly encapsidation and a shorter 3' untranslated encapsidation and a shorter 3' untranslated region (50-100 bases) - important in region (50-100 bases) - important in (-)strand synthesis. (-)strand synthesis.

GenomeGenome

The 5' UTR contains a 'clover-leaf' The 5' UTR contains a 'clover-leaf' secondary structure known as the secondary structure known as the IRES: IRES: Internal Ribosome Entry SiteInternal Ribosome Entry Site

The rest of the genome encodes a single The rest of the genome encodes a single 'polyprotein' of between 2100-2400 aa's. 'polyprotein' of between 2100-2400 aa's.

Both ends of the genome are modified, the Both ends of the genome are modified, the 5' end by a covalently attached small, 5' end by a covalently attached small, basic protein VPg (~23 AA's), the 3' end by basic protein VPg (~23 AA's), the 3' end by polyadenylation (polyadenylic acid polyadenylation (polyadenylic acid sequences are not genetically coded, there sequences are not genetically coded, there is a 'polyadenylation signal' upstream of is a 'polyadenylation signal' upstream of the 3' end as in eukaryotic mRNAs): the 3' end as in eukaryotic mRNAs):

StructureStructure

The particle is 27-30nm in diameter The particle is 27-30nm in diameter (depending on type and degree of (depending on type and degree of desiccation), while the length of the desiccation), while the length of the genome (stretched-out) is ~2,500nm genome (stretched-out) is ~2,500nm therefore the genome is tightly therefore the genome is tightly packed into the capsidpacked into the capsid

StructureStructure

The capsid consists of a densely-The capsid consists of a densely-packed icosahedral arrangement of packed icosahedral arrangement of 60 protomers, each consisting of 4 60 protomers, each consisting of 4 polypeptides, VP1, 2, 3 and 4 - all polypeptides, VP1, 2, 3 and 4 - all derived from cleavage of the original derived from cleavage of the original protomer VP0.protomer VP0.

GenomeGenome

VP-virion polypeptideVPg- important in the packaging of genome into the capsid

and iniating viral RNA synthesis

•Naked picornavirus genome is sufficient to infect cells

VP1- proteins at the vertices of the virion that contain a canyon structure to which the receptor binds

VP4- protein released after binding and the virion weakens

ReceptorsReceptorsVirusVirus # of # of

Serotypes Serotypes ReceptorsReceptors DescriptioDescriptio

nnHuman rhinovirusHuman rhinovirus 9191 ICAM 1,CD 54ICAM 1,CD 54 Immunoglobulin Immunoglobulin

likelike

Human rhinovirusHuman rhinovirus 1010 Low density Low density lipoprotein lipoprotein receptor (LDLR)receptor (LDLR)

Coxsackie ACoxsackie A 33 ICAM 1ICAM 1

EchovirusEchovirus 22 VLA -2VLA -2 Integrin likeIntegrin like

EchovirusEchovirus 66 Decay Decay accelarating accelarating factor factor (DAF) ,CD55(DAF) ,CD55

Regulator of Regulator of complement complement activatoractivator

PoliovirusPoliovirus 33 CD 155CD 155 Immunoglobulin Immunoglobulin likelike

EMCVEMCV 11 VCAM Vascular VCAM Vascular cell adhesion cell adhesion moleculemolecule

Adhesion Adhesion MoleculeMolecule

ReplicationReplication VP1 (receptor binds) VP1 (receptor binds) VP4 (virion weakened) VP4 (virion weakened)

release of genomerelease of genomebinds to binds to ribosomesribosomespolyprotein containing all viral protein polyprotein containing all viral protein sequences is synthesized within 10-15 mins of sequences is synthesized within 10-15 mins of infectioninfectionpolyprotein is cleaved by viral polyprotein is cleaved by viral proteaseproteaseviral RNA-dependent RNA polymerase viral RNA-dependent RNA polymerase generates a negative strand RNA template from generates a negative strand RNA template from which the new mRNA/genome and templates can be which the new mRNA/genome and templates can be synthesized. synthesized.

VP0,VP1,VP3 are cleaved and assembled into VP0,VP1,VP3 are cleaved and assembled into subunitssubunits5 subunits into protomer and 12 5 subunits into protomer and 12 pentamers to form procapsidpentamers to form procapsidgenome is inserted genome is inserted into procapsidinto procapsidVP0 cleaved into VP2 and VP4 to VP0 cleaved into VP2 and VP4 to complete capsid and the viron is released from the complete capsid and the viron is released from the cell.cell.

ReplicationReplication

TranslationTranslation The kinetics of Picornavirus The kinetics of Picornavirus

replication are rapid, the cycle being replication are rapid, the cycle being completed in from 5-10 (typically 8) completed in from 5-10 (typically 8) hours. hours.

Genomic RNA is translated directly Genomic RNA is translated directly by polysomes, but ~30 min after by polysomes, but ~30 min after infection, cellular protein synthesis infection, cellular protein synthesis declines sharply, almost to zero, this declines sharply, almost to zero, this is called is called 'SHUTOFF''SHUTOFF' - the primary - the primary cause of c.p.e: cause of c.p.e:

Time after infectionTime after infection

~1-2h~1-2h Sharp decrease in cellular Sharp decrease in cellular macromolecular synthesis; margination of macromolecular synthesis; margination of chromatin (loss of homogeneous appearance of chromatin (loss of homogeneous appearance of nucleus) nucleus) ~2.5-3h~2.5-3h Start of viral protein synthesis; Start of viral protein synthesis; vaculoation of cytoplasm, beginning close to vaculoation of cytoplasm, beginning close to nucleus & spreading outwards nucleus & spreading outwards ~3-4h~3-4h Permeabilization of plasma Permeabilization of plasma membranemembrane~4-6h~4-6hVirus assembly in cytoplasm Virus assembly in cytoplasm (crystals sometimes visible) (crystals sometimes visible) ~6-10h~6-10h Cell lysis; release of virus Cell lysis; release of virus particles  particles 

EnterovirusesEnteroviruses

Species: Species: Serotypes:Serotypes: Bovine enterovirus Bovine enterovirus 2 2 Human enterovirus A (coxsackie A viruses) Human enterovirus A (coxsackie A viruses) 10 10 Human enterovirus Human enterovirus B (coxsackie B viruses, echoviruses) B (coxsackie B viruses, echoviruses)

36 36 Human Human enterovirus C (coxsackie A viruses) enterovirus C (coxsackie A viruses) 11 11 Human Human enterovirus D enterovirus D 2 2 Poliovirus Poliovirus 3 3 Porcine Porcine enterovirus A enterovirus A 1 1 Porcine Porcine enterovirus B enterovirus B Unassigned: Unassigned: 22 22

TransmissionTransmission

Human Fecal Matter

Hand Sewage Solid waste landfills

Water supply

Shellfish

TransmissionTransmission

Respiratory,oropharynx and intestinal Respiratory,oropharynx and intestinal tracttract

Viral replication is iniated in the Viral replication is iniated in the mucosa,lymphoid tissue of tonsils and mucosa,lymphoid tissue of tonsils and pharynx, peyer’s patchespharynx, peyer’s patches primary primary viremiaviremia spread of virus to receptor spread of virus to receptor bearing target tissuebearing target tissue 2nd phase of 2nd phase of replicationreplication signs and signs and symptomssymptomssecondary viremiasecondary viremia

* Most enterovirus are cytolytic* Most enterovirus are cytolytic

Polio PathogenesisPolio Pathogenesis

PoliovirusPoliovirus

Clinical forms:Clinical forms:1.Assymptomatic illness- 90%1.Assymptomatic illness- 90%

- infection is limited to - infection is limited to nasopharynx and GITnasopharynx and GIT

2. Abortive 2. Abortive (minor illness)- 5%(minor illness)- 5% - - non specific febrilenon specific febrile

- fever,vomiting,malaise,sore throat within 3-5 - fever,vomiting,malaise,sore throat within 3-5 days of illnessdays of illness

PoliovirusPoliovirus

Clinical formsClinical forms

3.Non paralytic or Aseptic meningitis3.Non paralytic or Aseptic meningitis1-2%- backpains, muscle spasm,meningeal 1-2%- backpains, muscle spasm,meningeal

signs signs 4. paralytic major – 0.1 4. paralytic major – 0.1

– 2% – 2% – -appears 3-4 days after the minor illness -appears 3-4 days after the minor illness - -

fever subsides producing biphasic illnessfever subsides producing biphasic illness

- virus - virus viremia viremia AHC AHC spine, bulbar, cranial, spine, bulbar, cranial, respiratory center respiratory center

PolioPolio

-assymetric paralysis with no sensory -assymetric paralysis with no sensory lossloss

-Poliovirus type 1-85% of cases-Poliovirus type 1-85% of cases -Result-recovery,residual paralysis or -Result-recovery,residual paralysis or

deathdeath -Bulbar form is more severe- death 75%-Bulbar form is more severe- death 75% Postpolio Syndrome- occur later in lifePostpolio Syndrome- occur later in life 30-40 years later in 20-80% of original 30-40 years later in 20-80% of original

victimvictim

CoxsackieCoxsackie Groups- A and BGroups- A and B Clinical forms:Clinical forms:

1.Herpangina- 1.Herpangina-

virus can be recovered from the lesions and virus can be recovered from the lesions and fecesfeces

2. Hand foot and mouth disease- A162. Hand foot and mouth disease- A16 3.Pleurodynia (Bornholm’s Disease)- Devil’s 3.Pleurodynia (Bornholm’s Disease)- Devil’s gripgrip

4. Myocardial and Pleurocardial-4. Myocardial and Pleurocardial-

5. Viral (Aseptic )meningitis5. Viral (Aseptic )meningitis Fever ,rash,common colds- Coxsackie and EchovirusFever ,rash,common colds- Coxsackie and Echovirus -maculopapular rash, petichial,vesicular-maculopapular rash, petichial,vesicular

EnterovirusesEnteroviruses

-A21,A24 and Echo 11 and 20 – cause -A21,A24 and Echo 11 and 20 – cause rhinoviral like syndromerhinoviral like syndrome

Acute hemorrhagic conjunctivitis-Acute hemorrhagic conjunctivitis- -caused by Enterovirus 70 and Coxsackie A -caused by Enterovirus 70 and Coxsackie A

2424 -I.P. 24 hours ,last for 1-2 weeks-I.P. 24 hours ,last for 1-2 weeks Some Coxsackie B and EchovirusSome Coxsackie B and Echovirus -can be transmitted to fetus-can be transmitted to fetus -cause infection of pancreas-cause infection of pancreas IDDM IDDM

Laboratory diagnosisLaboratory diagnosis 1.CSF - (Polio or Enterovirus)1.CSF - (Polio or Enterovirus) Predominance of lymphocytic pleocytosisPredominance of lymphocytic pleocytosis Presence of 25-500 cells/mmPresence of 25-500 cells/mm 2.Culture-2.Culture- Polio-Pharynx- in the first few daysPolio-Pharynx- in the first few days Feces- 30 days Feces- 30 days CSF- rareCSF- rare Media- Monkey/kidney TissueMedia- Monkey/kidney Tissue Coxsackie and Echovirus – Stool and throat during Coxsackie and Echovirus – Stool and throat during

infection,CSFinfection,CSF Coxsackie B- media- Monkey or tumor embryo kidney cellCoxsackie B- media- Monkey or tumor embryo kidney cell Coxsackie A-media- grow in suckling mice than tissue cellCoxsackie A-media- grow in suckling mice than tissue cell

'New' Enteroviruses:'New' Enteroviruses:

Since 1969, 'new' Enteroviruses have been Since 1969, 'new' Enteroviruses have been assigned numbers, not names: assigned numbers, not names:

Type: llness: Type: llness: 68 Pneumonia 68 Pneumonia 69 None (?) 69 None (?) 70 Acute haemorrhagic 70 Acute haemorrhagic

conjunctivitis conjunctivitis (1969-1974 (1969-1974 pandemic) pandemic) 71 71 Meningitis, Meningitis,

rhombencephalitis rhombencephalitis 72 72 Hepatitis A virusHepatitis A virus

MMWR: MMWR: EnterovirusEnterovirus Surveillance - Surveillance -

United States, 1970--2005United States, 1970--2005

Treatment and preventionTreatment and prevention

Treatment:Treatment: Pleconaril-inhibits penetration of Pleconaril-inhibits penetration of

picornavirus into the cellpicornavirus into the cell Prevention:Prevention: IPV- SalkIPV- Salk OPV-SabinOPV-Sabin

RhinovirusRhinovirus Most important cause of common colds and URIMost important cause of common colds and URI Self limitedSelf limited ICAM -1 receptorICAM -1 receptor Labile to acidLabile to acid Grow best in 33 CGrow best in 33 C Transmission- infected hands, fomites, inhalationTransmission- infected hands, fomites, inhalation Can be infected by 1 infectious particleCan be infected by 1 infectious particle The release of cytokine during inflammation can The release of cytokine during inflammation can

promote spread of virus by enchancing promote spread of virus by enchancing expression of ICAM-1 receptor.expression of ICAM-1 receptor.

Immunity is transient- 18 monthsImmunity is transient- 18 months

RhinovirusRhinovirus Laboratory Diagnosis:Laboratory Diagnosis: 1.Nasal washing1.Nasal washing 2. Grow in Human diploid fibroblast2. Grow in Human diploid fibroblast 3. ID by acid lability3. ID by acid lability Treatment:Treatment: Enviroxime- inhibit viral RNA- dependent RNA Enviroxime- inhibit viral RNA- dependent RNA

polymerasepolymerase Plecoranil,Arildone,Rhodanine,Disoxaril- Blocks Plecoranil,Arildone,Rhodanine,Disoxaril- Blocks

uncoatinguncoating Prevention:Prevention: Handwashing and Disinfection of contaminated Handwashing and Disinfection of contaminated

materialmaterial