An overvew

1. Picorna Viruses
- Dr. Somosree (Ghosh) Mukherjee

2. • Picorna viruses represent a very large virus
family with respect to the no. of members but
is one of the smallest in terms of virion size
and genetic complexity.
• Pico - RNA viruses.
(Greek = very small)

3. • Picornaviruses are
among the most diverse
(more than 200
serotypes) and the
‘oldest’ known viruses
(temple record from
Egypt 1400 B.C.)

4. Structure
• Non-enveloped
• It is 27-30nm in diameter, with a tightly packed genome
inside the capsid, length of which (stretched-out) is ̴2500nm.
• The capsid consists of densely packed icosahedral
arrangement of 60 capsomers, whose pentamer consists of 4
polypeptides, VP1,2,3 and 4, - all derived from cleavage of
original polypeptide VP0.
• Surface capsid proteins VP1 and VP3 are major antibody
binding sites. VP4 is an internal protein.

7. Genome
• One linear single stranded positive sense RNA
molecule of size between 7.2kb to 8.5kb.
• Contains genome linked protein VPg.
• Genomic RNA is infectious ( ̴10⁶ fold less
infectious than intact particles, although
infectivity is increased if the RNA is introduced
into cells by transfection)- CHARACTERISTIC
OF (+)SENSE RNA VIRUSES.

8. Genome – code for the following
proteins

9. Classification
Family Genus Species
Picornaviridae Enterovirus Poliovirus,
Enterovirus,
Coxsackie virus,
Echovirus
Hepatoviruses Hepatitis A
Rhinovirus Human rhinovirus
Cardiovirus Encephalomyocarditis virus
(mice)
Aphtovirus Hand Foot Mouth disease
virus (cattle)
Parechovirus Human parechovirus
Erbovirus Equine rhinitis B virus
Kobuvirus Aichivirus
Teschovirus Porcine teschovirus

10. Receptors on host cell
• The receptors for polio virus and human rhino
viruses are all members of the
immunoglobulin gene superfamily, which
includes antibodies and some cell surface
adhesion molecules.
• In echovirus, it is integrin adhesion
superfamily

11. Receptors

12. Replication
• Cytoplasmic
• VP1 of the virion attaches to a specific receptor on the host cell
membrane which mediates endocytosis of the virus
• Capsid undergoes conformational change
• VP4 opens a pore in the host endosomal membrane and the viral
genomic RNA is released into the host cytoplasm
• VPg is removed from the viral RNA, binds to ribosomes, which is
then translated into a processed polyprotein.
• Polyprotein is cleaved by viral protease

13. • Viral RNA dependent RNA polymerase generates a negative strand
RNA template from which the new mRNA/ positive sense genome
can be synthesized.
• The VP0, VP1,VP3 are cleaved and assembled into subunits  5
subunits into protomer and 12 pentamers to form procapsid  VP0
cleaved into VP2 and VP4 to complete capsid and the virion is
released from the cell.
• Multiplication takes 5-10 hours.
• The genomic RNA is translated directly by the polysomes, but
within 30min after infection, cellular protein synthesis declined
sharply, almost to 0, this is called ‘SHUT-OFF’ – the primary cause
of c.p.e.

14. Replication

17. POLIOMYELITIS
 “polios”- gray mater ;
“myelos” – marrow or
spinal cord.
 3 types: Poliovirus 1,2,3
 Ingested, spread by
alimentary route:
Commoner in areas of poor
sanitation

18. Poliomyelitis is an acute infectious disease
which affects the CNS with destruction of
motor neurons of the anterior horns in the
spinal cord resulting in flaccid paralysis (less
than 0.1%). However, most poliovirus
infections are subclinical.
During epidemic outbreaks, type I is most
frequently isolated (in 65-95% of cases) while
types II and III account for the remaining 5-35%
of cases.

23. The poliomyelitis virus is cultivated
on kidney cells of green African
monkeys and on diploid human cells
devoid of latent SV40 viruses.
The cytopathic effect is attended by
destruction and the formation of
granules in the infected cells.
Cultivation

24. Antigenic properties
• 3 antigenic types :1,2,3
• Prototype strain are :
1. Brunhilde and Mahoney : type I : Epidemic
2. Lansing and MEFI : type II : Endemic
3. Leon and Saukett : type III : Epidemic
• By ELISA and CFT – 2 antigens can be recognised
D (N-naïve) – dense Ag
C (H- heated) – coreless or capsid Ag –are cross
reactive.

25. Pathogenesis
Source of infection: Apparent and
subclinical patients
Incubation: is usually 7-14 days, but it may
range from 3 to 35 days.

26. Transmission
Fecal – oral route: poor hygiene, dirty diapers
(especially in day-care settings)
Ingestion via contaminated food and water
Contact with infected hands
Inhalation of infectious aerosols

30. Stages of Poliomyelitis
• Abortive poliomyelitis
• Non paralytic
poliomyelitis (aseptic
meningitis)
• Paralytic poliomyelitis
• Progressive post
poliomyelitis muscle
atrophy

31. Most common
form
Recovery in few
days
Aseptic
meningitis
2-10 days
Flaccid paralysis –LMN
Incordination – brainstem
Recovery-6months
residualparalysis
Progressive Post poliomyelitis
muscle atrophy

34. Lab Diagnosis
A. Isolation of the virus –
• Throat swab - soon after the onset
• Rectal swab or stool – longer periods
• CSF – virus not isolated or recovered
• Specimens kept frozen during transit
• Human or monkey kidney cell cultures are inoculated,
incubated and observed. [fibroblastic MRC-5 cells]
• CPE appear in 3-6 days – infected cells round up and
become refractile and pyknotic
• Isolated virus is identified and typed by neutralization with
specific antiserum.

35. B. Serology –
• CFT
• Neutralization test using paired sera
• During inf. C antibodies form before D antibodies.
• Early acute stage – C antibodies only
• 1-2 weeks later - both antibodies
• Late convalescent stage – D antibodies only.

36. Immunity
Immunity is permanent and type specific
low degree of heterotypic resistance induced by
infection (between type 1 and type 2 ).
Passive immunity is transferred from mother to
offspring. The maternal antibodies gradually disappear
during the first 6 months of life.
Passively administered antibody lasts only 3-5
weeks.
IgG, IgM – blood
IgA – Immunity against Intestinal infection.

37. Treatment
NO SPECIFIC TREATMENT.
Reduction of pain and muscle spasm and maintenance of respiration
and hydration.
When the fever subsides, early mobilization and active exercise are
begun.
There is no role for antiserum.
Early injections of gamma-globulin, blood transfusion, wide use of
vitamins C and B, amino acids (leucine, glutamic acid), analgesic and
stimulants (proserine, galanthamine, etc.) are recommended.
Prevention of contractures and deformations.

38. Prevention
• Nonspecific measures-
• Safe drinking of water
• Improvement of sanitation
• Food hygiene
• Vaccination - Both live and killed vaccines are
available
• Killed vaccine – SALK parental vaccine
• Live vaccine – SABIN oral vaccine

39. Killed – Salk parental vaccine / IPV
• Formalinized vaccine prepared from virus
• Grown in monkey kidney culture
• Induces humoral antibodies but does not
induce local immunity.
• 1955- Cutter incident- incomplete inactivation
of viruses- over 100 cases of paralytic
poliomyelitis in vaccinated pts.

40. Live attenuated vaccine – Sabin’s /OPV
• Grown in primary or human diploid cell cultures
• Stabilized by MgCl2 and kept at 4°C for a year and
for weeks at room temperature.
• Live vaccines multiplies, infects and immunizes
• Progeny of vaccine virus are disseminated in the
community
• Multiple doses are required to establish
permanent immunity

41. • Criteria for attenuation of virus-
1. Should not be neurovirulent
2. should be able to set up intestinal infection
following feeding and induce immune response
3.should be stable
• Markers – d marker, rct40, MS, McBride’s
intratypic antigenic marker

42. • IgG , IgM and IgA are formed
• OPV contains :
Type 1 virus-10 lakhs (TCID50 per dose 0.5ml)
Type 2 virus-2 lakhs
Type 3 virus-3 lakhs
• Presently Bivalent Strain
• Shelf life 4-8°C 4 months, -20°C for yrs
• Failure of cold chain

43. • Killed vaccine schedule-
1st dose at 6 months
3 doses- 4to 6 weeks apart
Booster at 15-18 months

44. Present Dosage is :

46. • Safety-
Killed vaccine - Aquires neurovirulence
Live vaccine (OPV) - Not suitable for immunodeficient
• Ease of administration - OPV prefarable
• Economical – OPV more economical
• Booster doses are necessary in case of killed vaccine
• However OPV is given early during an epidemic.

48. Eradication of Poliomyelitis
• The WHO in 1988 proposed global eradication of
poliomyelitis by the year 2000
• By global immunization with OPV
• Poor progress in immunization in many countries has been
a setback to this objective
• In 2015 – only 74 cases in entire World
• In INDIA – 2009- 741cases
2010- 42cases
2011- 1 case (Howrah)
2012- NO CASE – INDIA’s name was taken off the
list of World’s Endemic countries
2014- INDIA was declared POLIO ERADICATED
COUNTRY
• Present – Pakistan, Afganistan, Nigeria

49. Pulse Polio Immunisation Programme
• Mass administration of OPV on a single day to all
children aged 0-5 years in the community
• The strategy is to give rounds of doses at an
interval of 4-6 weeks during the low polio
transmission period in winter (Nov-Feb)
• Given regardless of previous immunization status
and does not replace National universal
immunization programme.

50. Coxsackie Virus
• Groups A and B
• Based on early observations on their
pathogenicity in mice-
Group A – Flaccid paralysis d/t myositis
Group B – Spastic paralysis d/t muscle injury
and neuronal degeneration.
• Serotypes – Group A – 23serotypes (1-22, 24)
Group B – 6serotypes (1-6)

51. • Transmission –
Feco-oral route
respiratory aerosols
fomites.
Replicate in the upper respiratory tract and distal small
bowel.
• Pathogenesis similar to other enteroviruses
• Virus can be recovered from lesions, throat (for a few
days) and faeces( upto 5-6weeks)
• Incubation period 2-9 days

52. • Clinical forms -
1. Herpangina- Coxsackie A virus ( 2-6,8,10)
2. Hand-foot and mouth disease – CoxsackieA16
(A5,A10) and enterovirus 71
3. Pleurodynia ( Bornholm’s disease) – Devil’s grip –
Coxsackie B virus
4. Myocarditis, Pericarditis – Coxsackie B3 virus
5. Viral (aseptic meningitis) – Coxsackie virus (A7 and
A9) or echo virus.
6. Acute hemorrhagic conjuctivitis – Enterovirus mainly.
Coxsackie A24.
7. Respiratory infections
8. Diarrhoea

53. Herpangina: There is an abrupt onset of fever, sore
throat, anorexia, dysphagia, vomiting, or abdominal pain. The
pharynx is usually hyperaemic, and characteristic discrete
vesicles occur on the anterior pillars of the fauces, the
palate, uvula, tonsils, or tongue. The illness is self-limited
and most frequent in small children.

54. Exanthems – Rubelliform rashes

55. Hand, Foot, and Mouth Disease: The syndrome is
characterized by oral and pharyngeal ulcerations and a
vesicular rash of the palms and soles that may spread to the
arms and legs. Vesicles heal without crusting, which clinically
differentiates them from the vesicles of herpes- and pox-
viruses. The rare deaths are caused by pneumonia.

56. Hand-foot-and-mouth disease
• Hand-foot-and-mouth
disease: mostly coxackie A
– fever, malaise, sore
throat, vesicles on bucсal
mucosa, tongue, hands,
feet, buttocks
• highly infectious
• resolution – 1w

57. Lab diagnosis
• Specimens - throat swab, stool, nasal
secretions, CSF, conjunctival swab
• Culture – Tissue culture (CPE – 5-14 days)
Suckling mice ( develop illness -
Grp.A -> 3-8days and Grp.B -> 5-14days
• Serology – not practicable (many serotypes) -
CFT, ELISA, immunoflorescence
• RT PCR

58. • Treatment – Supportive
• No vaccines

59. ECHOVIRUSES
•The ECHO viruses (enteric cytopathogenic human orphan viruses)
• they infect the human enteric tract.
•Over 34 serotypes are known
•Clinical forms –
1.Aseptic meningitis (4, 6, 9, 11, 14, 16, 18, and others)
2.febrile illnesses with or without rash {9, 16 ("Boston exanthem
disease"), 18, and 4}. Rashes are commonest in young children.
3.common colds (type 28)
4.acute hemorrhagic conjunctivitis, muscle spasms (6,9 and others)
5.Infantile diarrhoea (18,20)

60. • Does not produce diseases in suckling mice,
rabbits, or monkeys
• Cultured in Monkey kidney and human
embryonated kidney cell culture, human
amnion cell and HeLa.

61. Boston exantem illness

62. Transmission
• Feco-oral
• Respiratory aerosols
• Direct contact
• Summer season

63. Laboratory Diagnosis –
•Isolation of virus –
Throat swabs, stools, rectal swabs, and, in aseptic
meningitis, cerebrospinal fluid.
•Tissue culture-
•Serologic tests- are impractical — (because of the many
different virus types)— Nt and HI antibodies are type-
specific and may persist for years. CF antibodies give
many heterotypic responses.
If an agent is isolated in tissue culture, it is tested against
different pools of antisera against enteroviruses.
•RT PCR

64. •Treatment – supportive
•Control. Avoidance of contact with patients exhibiting
acute febrile illness, especially those with a rash,
diarrhoea.
•No Vaccines

65. NEW ENTEROVIRUS TYPES
Enterovirus 68 - children with bronchiolitis or pneumonia.
Enterovirus 70 is the chief cause of acute hemorrhagic conjunctivitis.
Pandemic form in 1969-1971 in Africa and Southeast Asia
Acute hemorrhagic conjunctivitis (with sudden onset of subconjunctival
hemorrhage, epithelial keratitis and lumbar radiculomyelopathy).
I.P. 1 day and lasts for 8-10 days.
Complete recovery is the rule
The virus is highly communicable
There is no effective treatment.

66. Enterovirus 71 was isolated from patients with meningitis,
encephalitis, and paralysis resembling poliomyelitis.
It continues to be one of the main causes of CNS disease
around the world.
In some areas, particularly in Japan and Sweden, the
virus has caused outbreaks of hand, foot, and mouth
disease.

67. Rhinovirus
• Common cold virus
• More than 100 serotypes
• Attaches to ICAM-1 receptor in the nose
• Nasal secretions are infective
• Gross appearance like entero
• Acid labile (destroyed at pH3)
• Grown in Human cell lines – W-138, MRC-5
• Cultivated at 33°C

68. Pathogenesis
• Transmission- infected hands, fomites,
inhalation
• Entry- respiratory tract
• Multiplies in nasal mucosa
• vasodilatation, edema and mild cellular
infiltration in nasal mucosa
• Local inflammation and cytokines, histamine ,
IL-1 is responsible for symptoms of cold

70. • Clinical findings –
I.P. 2-4days
lasts for7days
sneezing, nasal obstruction and sore throat.
may lead to secondary bacterial infection.

71. Lab diagnosis
• Isolation of virus – nasal swab, throat swb
• Culturing on MRC5 and W-138, human diploid
fibroblast.
• Appearence of CPE
• Serology- no role (everyone- high titres)
• RT PCR
• Immunity
• Neutralizing antibodies are develop in the serum and
nasal secretions, 7-21 days after infection.

72. Prevention and control
• No specific treatment
• Enviroxime – inhibits viral RNA dependent RNA
polymerase
• Plecoranil – blocks uncoating
• Intranasal spray of Gamma interferone for 5 days.
• Vaccines are unsuccessful (Rhinovirus13 vaccine)
• Hand washing