Science of Avian Influenza Vaccines

David E. Swayne Southeast Poultry Research Laboratory Agricultural Research Service U.S. Department of Agriculture Athens, Georgia

Avian Influenza (AI) • Small RNA virus • Surface spikes – hemagglutinin & neuraminidase proteins • 16 hemagglutinin and 9 neuraminidase subtypes – Ex. H5N1, H9N2, H7N7 • Vary in severity of disease: – Low Pathogenicity (LP) – High Pathogenicity (HP)

Disease Control Basics • Strategies for dealing with poultry disease are developed to achieve one of 3 goals or outcomes: – Prevention: preventing introduction – Management (Control): reducing losses by minimizing negative economic impact through management practices – Eradication: total elimination

• These goals are achieved through various strategies developed using universal components: – – – –

Biosecurity (exclusion and inclusion) including quarantine Diagnostics and surveillance Elimination of AI virus infected poultry Decreasing host susceptibility to the virus (vaccines and host genetics) – Education Swayne, Dev. Biol. Basel 119:219-228, 2004

Avian Influenza Vaccines: Poultry • Vaccination not routine in most of the world • No single vaccine for AI viruses • Anti-hemagglutinin antibodies are protective, but anti-neuraminidase also protective, less effective • Types of Vaccines – Inactivated whole AI virus (C,E) – Recombinant live virus vectors: Fowl Pox (C), Adenovirus (E)VEE (E), ALV (E), Vaccinia (E), ILT (E), NDV (C,E) – Subunit AI proteins (E) - HA, NA: Baculovirus, Yeast, Bacterial, Plant – Naked DNA vaccines (E)

Important Vaccine and Vaccination Issues to Develop Proper Immunity • Inactivated whole AI virus • Need adequate antigen content – minimum 1-5 micrograms/dose • Need good oil emulsion adjuvant system • Virus strains homology at hemagglutinin protein • Uniform administration • DIVA requires special tests

• Recombinant fowl pox-AI-H5 • Administered in hatchery – improved biosecurity, quality control • Birds cannot have prior exposed to or immunization with fowl poxvirus • DIVA uses existing tests

Vaccines in AI Control ƒ LPAI outbreaks -

Field Use

• H1N1 swine influenza: Turkey Breeders (2.6 million USA 2001): other subtypes in world used • H9N2 Middle East and Asia: ? doses • Waterfowl - origin viruses: Meat Turkeys (MN: 22 million doses) – • Layers - rare use USA (inactivated H6N2 & H7N2)

ƒ HPAI - $63 million to eradicate US 1983-84 outbreak • Mexico, Guatemala & El Salvador (1995-2005) - H5N2: 1.8b doses inactivated & 1.5b doses Fowlpox recombinant • Pakistan (1995-04) - H7N3: inactivated • Hong Kong (2002-04) – H5N1: inactivated; China, Vietnam & Indonesia

Avian Influenza Vaccines in Asia • Inactivated vaccine strains: • A/turkey/England/73 (H5N2) LPAIV • A/chicken/Mexico/94 (H5N2) LPAIV • A/chicken/Indonesia/03 (H5N1) HPAIV • A/turkey/Wisconsin/68 (H5N9) LPAIV • Infectious clone: H5 & N1 genes of A/goose/Guangdong/96, 6 internal genes PR8 • Recombinant fowlpox with cDNA inserts of AI viral genes • H5 gene - A/turkey/Ireland/83 • H5 & N1 genes - A/goose/Guangdong/96 • Recombinant Newcastle disease virus with H5 AI gene insert

Vaccination - AI 1. Vaccination as a Tool During Eradication •“Ring” vaccination: difficult - compartment

•“Suppressor” vaccination

Surveillance or Buffer Zone

Quarantine Zone or Compartment

Q

• Repopulation • In face of outbreak?

2. Vaccination as a Tool for Management • Decrease clinical disease and reduce economic losses • Use in high risk areas

Priorities for Vaccination Decreasing Order of Priority 1. High risk situations; e.g. in an outbreak zone as ring or suppressor vaccination 2. Valuable genetic stock such as pure lines or grandparent stocks whose individual value is high 3. Rare captive birds 4. Long-lived birds, such as egg layers or parent breeders 5. Meat birds

Properly Used AI Vaccines ƒ ƒ ƒ ƒ ƒ ƒ

Protection – Positive Aspects

Increase resistance to AI virus infection Prevent clinical signs and death Reduced shedding of field virus when infected Prevent contact transmission Provide long protection from single vaccination Protect against low or high exposure dose of field virus ƒ Protect against a changing virus, but vaccine strains have finite lifespan

Protection – Negative Aspects

ƒ “Silent” infections ƒ Special surveillance procedures and methods needed

Increased Resistance to AIV Infection

ƒ Requires 102 EID50 higher dose to infect vaccinated compared to non-vaccinated turkeys (Capua, personal communication)

Inactivated AI Vaccines: Assessing Asian H5N1 HPAIV Protection in Chickens Chickens vaccinated SQ 3 wks with inactivated whole AIV vaccine and IN challenged 3 wks later with high dose (106.0 EID50 of HPAIV A/chicken/Indonesia/7/2003 [H5N1]) • 1994 North American vaccine virus (Mexico/94) •1986 Eurasian vaccine virus (Pottsdam/86) Morbidity (3-4+)*

Mortality (MDT)**

Group

Vaccine

1

Nobilis Hepatitis + ND Inac (Control) Nobilis I.A. Inactivated H5N2 (Mexican Strain)

10/10A

Nobilis Influenza, H5N2 (European Strain)

2 3

Virus Isolation, 2 DPC (Log10 EID50 titer/ml) oral

cloacal

10/10A (2.2)

10/10A (6.16 a)

10/10A (5.82 a)

0/10B

0/10B

5/10B (1.23 b)

3/10B (1.00 b)

1/10B

1/10B (2.0)

6/10AB (1.78 b)

3/10B (1.53 b)

Recombinant Fowlpox Vaccine: Assessing Asian H5N1 HPAIV Protection in Chickens Chickens vaccinated SQ 1d with fowlpox-AIV-H5 recombinant* or inactivated whole AIV vaccine** and IN challenged at 3 wks with low challenge dose (103.3 EID50 of HPAIV A/chicken/South Korea/2003 [H5N1]) Virus Isolation, 2 days Post-challenge (Log10 EID50 titer/ml)

Mortality (Mean Death Time in days) Oral swab Cloacal swab 3/5AB (1.67) 0/5A (