Orthomyxoviruses

September 15,16, 2010

The big pandemic of 1918

John Hopkins Hospital BulletinApril 1919

Nature Jan 18, 2007

The 1918 virus

Loo and GaleNature Jan 18, 2007

Orthomyxoviridae

• -ve stranded RNA, segmented

• Haemagglutinin (HA) and neuraminidase (N) on surface

Viruses with -ve RNA genomesParamyxoviridae

Rhabdoviridae

Orthomyxoviridae

Filoviridae

Bunyaviridae

parainfluenza viruscanine distemper virus

respiratory syncytial virus

rabies virus

vesicular stomatitis virus

influenzaviruses

Ebola virus

Haantan virus

Orthomyxoviridae

Influenzavirus A

Influenzavirus B

Influenzavirus C

humans

horses

pigs

birds

marine mammals

humans

humans

pigs

dogs

cats

Influenza virions

nucleocapsid(RNA fragmentswrapped in protein)

envelope

haemagglutinin andneuraminidase “spikes”In envelope

100 nm

Haemagglutinin and Neuraminidase

receptorbindingsite

active site

variableloops

variableloops

HA N

sialic acidon receptor

Distribution of HA serotypes in nature

HA serotype Birds Horses Pigs Humans

HA1

HA2

HA3

HA4

HA5

HA6

HA7

HA8-16

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

Distribution of N serotypes in nature

Birds Horses Pigs

N1

N2

N3

N4

N5

N6

N7

N8

yes

yes

yes

yes

yes

yes

yesyes

yes

yes

yes

yesyesyes

N9 yes

Humans

yes

Nomenclature

A/equine/Saskatoon/1/90(H3N8)

group

specieslocation

Isolate numberyear

Serotype of HA and N

•A/equine/Prague/1/56(H7N7)•A/fowl/Hong Kong/1/98(H5N1)•A/swine/Lincoln/1/86(H1N1)

Influenzavirus replicationHA cleavedbyproteases HA binds to

receptor

virus inphagolysosome

loweredpH, HAfusesmembranes

RNAreleased

virusbuds

N releasesvirus

Cleavage of HA

Clara (mucus),extracellular,serum,bacterialproteases

HA0

HA1

HA2

bindsreceptor binds

receptorpenetratescell

Chemotherapy

• Prevent membrane fusion– Amantidine (Symmetrel)– Remantidine (Flumadine)

• Neuraminidase inhibitors– Zanamivir (Relenza)– Oseltamivir (Tamiflu)

Epidemiology of influenza ?

How do flu viruses change?

virus polymerasemakes mistakes

selection ofantigenic and host variants

viruses re-assort

How changes have led to human pandemics

1918

1957

1968

2009

avian H1N1 virus adapts to humans

reassortment

H2, N2, PB1 from duckrest from human H1N1

H3, PB1 from duckrest from human H2N2

H2N2

H3N2

swine human

avianH1N1

Factors that sustain epizootics/epidemics

• Antigenic drift

• Reassortment and antigenic shift

• Short term immunity

• Cross species transfer

Introduction of influenza to horses

• Before 1950s– A/eq/Prague/1/56(H7N7)

• 1963 - from birds?– A/eq/Miami/1/63(H3N8)

• persists today (“Eurasian” “American strains”)

• 1989 - from birds– A/eq/Jilin/1/89(H3N8)– epizootoics in 1989,90– none since

Extinguished

World-wide, except New Zealand, Iceland

Extinguished, central Asia ?

dogs2004

Pathogenesis

opportunistic bacterial infections

no complicationsand rest

resolution in 3 weeks inhalation(infected animalor fomites)

replication inepithelial cellsupper RT

Clinical signs

• Sudden onset

• Fever (39-42), biphasic

• Dry cough

• Nasal discharge (serous ->mucopurulent)

Risk factors

Current specific antibody levelsTime since last vaccinationAgeSex

Other pathogens that cause similar signs

• influenza

• equine herpesvirus 1, 4

• S. equi

• equine viral arteritis

Diagnosis

• Clinical signs

• Virus isolation

• Directagen Flu-A

• Serological tests– HAI– Single radial haemolysis

Vaccines

• Inactivated, H7N7 and H3N8 isolates– Adjuvant– Most -> short lived protection

• Revaccinate at 6 week intervals

• Intranasal, cold-adapted

• Vectored (Recombitek)

Swine influenza

• H1N1 - two variants

• H3N2

• Ontario (1989-92)– 53% H1N1– 17% H3N2 (similar to human virus)– 4% H1N2 (similar to human virus)

WHO updatehttp://www.who.int/csr/don/2009_09_04/en/index.html

Avian influenza

• Highly Pathogenic Avian Influenza (to date H5, H7)– Pennsylvania - 1983 - $65,000,000– Mexico - 1993-4 - $$?– B.C. 2004– Saskatchewan 2007 (H7N3)

• http://www.inspection.gc.ca/english/anima/heasan/disemala/avflu/2007sask/repsaske.shtml

• Asymptomatic to fatal (HPAI)

HA cleavage and virulence

May ‘94 ->June ‘94

Dec ‘94 ->Jan ‘95

P Q - - R E T R lowcleavability

lowvirulence

P Q R K R K T R highcleavability

highvirulence

systemicinfection

respiratoryinfection

?

Cleavage of HA

Clara (mucus),extracellular,serum,bacterialproteases

HA0

HA1

HA2

bindsreceptor binds

receptorpenetratescell

The 2004 BC outbreak

• 17 million birds destroyed

• 1128 claims, 56 million dollars dispensed

• August 18, 2004– surveillance indicates highly pathogenic

influenza eliminated from BC flocks– all control measured eliminated

Avian H5N1 disease in catsintra tracheal inoculation

in-contactfeeding infected chick

control or H3N2

virus excretion by cats

Kuiken et al. Oct 2004Science 306:241

HA and host specificity

2,3 2,62,3 2,6

avian gut pig resp. tract human resp. tract

avian H1-H15 pig H1, H3 H1(1918) H2, H3human

Stevens. Science, March 19, 2004

Why does avian H5N1spread inefficiently between humans

Shinya et al. Nature March 22, 2006

nasal mucosa

paranasal sinus

bronchus

resp. bronchiolealveolus

Process for human influenza vaccines

• February meeting– Commonwealth Serum Labs (Australia)– CDC (USA)– Natl. Inst. For Medical Research (UK)– European Inst. For Biological Standardization

(EU)– Food and Drug Admin. (USA)

Process for human influenza vaccines

• March-April– Genetic and antigenic characterization of

approved strains– Distribution by WHO to manufacturers– Production of seed stock– Tests for contaminants (bacteria, mycoplasma,

viruses)

Process for human influenza vaccines

• April-August– Vaccine production– License application made– Clinical trials (to be submitted before

vaccination season)

Process for human influenza vaccines

• August-September– Distribution begins

Human flu vaccine composition for 2008

A/Brisbane/59/2007 (H1N1)A/Brisbane/2007 (H3N2)B/Florida/4/2006