PicoRNA Viruses(Small RNA virus)

Pico RNA Viruses

• Structure

• Classification

• Multiplication

• Clinical manifestations

• Epidemiology

• Diagnosis

• Control

Baron’s Web Site

Structure

• Icosahedral
  • 20-30 nm
  • C=32

• Non enveloped

• ss RNA
  • sense strand
  • VPAg covalently bound to 5’
  • 3’ poly A tail

Picornaviridae Classification

• Rhinovirus- nasal cavity

• Enterovirus- alimentary tract
  • poliovirus
  • coxcackievirus
  • echovirus
  • Enterovirus #

• Apthovirus
  • hoof and mouth
  • cloven hooved animals & humans

• Cardiovirus- rodents

Multiplication

• Multiply in cytoplasm

• sense ssRNA acts as mRNA

• Replication associated with cytoplasmic membrane

Multiplication

Polio

Polio

• Early undifferentiated febrile

• Gastrointestinal

• Spinal & bulbar poliomyeltis

• Paralytic polio - irreversible

Polio Pathogenesis

• Humans only natural host

• trophic for epithelial cells
  • gene product of chromosome 19

• HLA- 3 HLA-7 increased risk

Poliovirus Pathogenesis

• Virus ingested

• Multiples tonsils & upper respiratory tract

• Passes through stomach

• Multiples in Payers Patches

• Migrates to regional lymph nodes

Poliovirus Pathogenesis

• Virus passes into blood via lymph nodes

• virus crosses Blood-Brain barrier into CNS

• Virus shed in Feces

FDR ( 1921)

Diagnosis

Epidemiology Polio

• Stable survive for long periods
  • sewage
  • water
  • food

Cockroachs : transient vectors

Koprowki tests live vaccine (1950)

• Jonas Salk’s injectable vaccine effective (1954)

Control

• Oral vaccine
  • Albert Sabin
  • 1961

Future of Vaccines

Polio incidence 1987

Polio Incidence 1997

PPT Slide

Enterovirus Pathogenesis

Rhinoviruses Viruses

• Clinical manifestations

• Epidemiology

• Diagnosis

• Control

Rhinovirus Pathogenesis

Nasopharynx

Nasal Secretions

coryza

Common cause of

serious lower respiratory

tract infection in

children

Rhinovirus Clinical Manifestations

• Coryza - common cold

• mucous secretions

• watery eyes

• sneezing

Symptoms induced when

Virus stimulates histamine release from mast cells

Antihistamines reduce symptoms

Rhinovirus Multiplication

• Hosts humans & chimps
  • Grow epithelial cells
  • Multiples best at 33 C
  • sensitive to pH 3.0

• Restricted nasopharynx
  • occasionally lungs
  • especially newborn

Rhinovirus Epidemiology

• spread via nasal secretions

• Primarily Contaminated hands
  • Autoinoculate nasopharynx and eyes

• Secondarily Repiratory droplets & aerosols

Rhinovirus Diagnosis

• Clinical symptoms

• Tissue culture

• Serology-impractical
  • Over 115 serotypes
  • immunity is serotype specific

Rhinovirus Control

• Control symptoms

• Improve personal hygiene

• Ribavrin shortens duration

• prophylactic interferon nasal sprays

DONE!!!