1. Hugh B. Fackrell Fackrel@Uwindsor.ca Filename: orthomyx.ppt
Orthomyxovirus
Hugh B. Fackrell
Filename: orthomyx.ppt

2. Orthomyxovirus Outline
Structure
Classification
Multiplication
Clinical manifestations
Epidemiology
Diagnosis
Control
Baron’s Web Site

3. Structure Influenza viruses ssRNA, antisense,
multipartite genome, 7-8 segments, 10 genes
spherical OR filamentous
enveloped
hemagglutinin
neuraminidase

4. Flu Hemagglutinin Protein in viral envelope
13 different hemagglutinin antigens
binds to N-aceytlneuraminic acid on host cell glycolipids or glycoproteins
Hemagglutinin hydrolysed by host cell proteases to create infectious virion

5. Flu Neuraminidase Found in the viral envelope
9 different neuraminidase antigens
Removes N-acetylneuraminic acid from glycolipids and glycoproteins derived from host cell
Dissolves N-acetylneuraminic acid in mucus to increase liquefaction
Prevents self hemagglutination

6. Classification
Three antigenic types of nucleoprotein give rise to three different strains of influenza
Flu A,
Flu B
Flu C
No antigenic cross reactivity of nucleoproteins

7. Gene Reassortment ANTIGENIC SHIFT
Host cell is infected simultaneously with two different strains of flu
Progeny viruses have mixture of gene segments because RNA multipartite
Novel Type A strains
gives rise to pandemics of influenza A

8. Influenza 1918 Started in midwestern USA
Spread to Europe on troopships
Attacked healthy adults
Antigenic Shift
Trying to isolate cells with both strains of Virus

9. Antigenic Drift
Flu A Flu B undergo genetic changes in the enveloped proteins
MINOR antigenic changes
serologically cross reactive
Causes yearly epidemics

10. Influenza Subtypes Strain Influenza A first isolated Bangkok Year 79
Hemagglutinin :H1, H2, H3
Neuraminidase N1, N2
A/Bangkok/79 H3N2
Link to CDC Web site

11. Flu infection cycle

13. “Original Antigenic Sin”
Individual develops antibodies to flu antigens after first exposure
On second exposure antigens changed inducing a new array of antibodies
Antibodies to shared antigenic epitopes have higher avidity
Used to identify the original infection

14. Influenza Multiplication
virus binds to host by hemagglutinin
transcription & nucleocapside assembly in nucleus
infectious virions assembled in cytoplasm
bud from cell membranes
cycle takes 6 hours

15. Clinical Manifestations
Respiratory symptoms
Coryza, sore throat, cough, substernal chest pain
Systemic Symptoms
Headache, chills, fever (38-40C), prostration

16. Epidemiology Epidemic lasts 6 weeks in Jan-Feb
First in school age children (5-9 years)
Brought home to preschooler & adults
industrial absenteeism
Pneumonia influenza in elderly

17. Diagnosis Clinical symptoms more likely if
syndrome occurs in adults in winter
a febrile respiratory epidemic is underway
Detection of Virus
rise in antibody titre between acute phase and convalescent phase

18. Detection of Flu Virus Isolated from respiratory secretions
grown in tissue culture
embryonated eggs
Virus identified by presence of hemagglutinin

19. Tissue culture Hemadsorption
Red cells adhere to virions budding from the host cell
Hemagglutination inhibition
Confirm with serological analysis of tissue culture fluid

20. Prevention Prevention Influenza virus vaccine Rimantadine Treatment
Amantadine
1976 effective against type A Web site
Rimantadine
1993 effective against type A & type B
Neuraminidase Inhibitors
zanamivir and oseltamivir 1999 web Site
Prevention
Influenza virus vaccine

21. Treatment Amantadine Rimantadine Neuraminidase Inhibitors
1976 effective against type A Web site
Rimantadine
1993 effective against type A & type B
Neuraminidase Inhibitors
1999 zanamivir and oseltamivir web Site

22. Influenza virus vaccine
Developed half a century ago
virus grown in chick egg embryos
inactivated with formalin
One- doses administered pareenterally in the fall
50-90% effective
Web site

23. The national swine flu immunization of 1976 was accompanied by an increase risk of Guillain-Barre syndrome

24. Guillain- Barre Syndrome
AKA Acute Infectious Polyneuritis
Symptoms
symmetric flaccid paralysis
facial paralysis
Degeneration of myelin of peripheral nerves
Allergic reaction

25. Amantadine Amantadine hydrochloride administered for 10 days
blocks viral uncoating
prevents 50% of infections
prevents 67% of illnesses
prophylactically protects 80%