The Science of Influenza Vaccine Development: Implications for the Public Health Practitioner

David Cho, PhD, MPH

Program Officer, Influenza Vaccine Development

Respiratory Disease Branch, DMID, NIAID

Goals of the Presentation

Describe the basic scientific differences between seasonal and pandemic influenza

Explain what researchers are doing to overcome the challenges that a pandemic strain brings

Explain what practitioners should consider in preparation for a pandemic

Characteristics of a Pandemic Influenza Virus

Influenza A virus with a novel hemagglutinin or novel hemagglutinin and neuraminidase in man

Susceptibility (no neutralizing antibody) to the novel virus in a large proportion of the population

Demonstration of the virus to cause and spread person-to-person in a sustained fashion

Influenza Virus Nomenclature

Source: Subbarao/Murphy

Clinical Burden of Influenza Virus Morbidity and Mortality

Previous pandemics

1918 H1N1 transferred from birds?: > 40 million deaths worldwide

1957 H2N2 avian-human reassortant: > 2 million deaths

1968 H3N2 avian-human reassortant: > 1 million deaths

Seasonal influenza

Millions of human cases; hundreds of thousands of hospitalizations yearly in the US alone

Influenza and pneumonia: 7th leading cause of mortality in the US in 2002

20,000 to 40,000 deaths annually US

250,000 to 500,000 deaths annually worldwide

Clinical Burden of Influenza Virus Morbidity and Mortality (continued)

H5N1 Avian influenza

290+ documented human cases

170+ deaths

Over 3 ½ + years, fewer than 100 documented cases/ year

Seasonal influenza Millions of human cases;

hundreds of thousands of hospitalizations yearly in the US alone

Influenza and pneumonia: 7th leading cause of mortality in the US in 2002

20,000 to 40,000 deaths annually US

250,000 to 500,000 deaths annually worldwide

Cumulative Number of Confirmed Human Cases of Avian Influenza A/(H5N1) Reported to WHO 11 April 2007

Country cases deathsAzerbaijan 8 5

Cambodia 7 (1) 7 (1)

China 24 (2) 15 (1)

Djibouti 1 0

Egypt 34 (16) 14 (4)

Indonesia 81 (6) 63 (5)

Iraq 3 2

Lao People’s Dem Rep 2 2

Nigeria 1 1

Thailand 25 17

Turkey 12 4

Viet Nam 93 42

Total 291 172

Cases and countries shown in gold for events since January 2007. WHO reports only laboratory-confirmed cases.

> 50% mortality

Mississippi Americas flyway

Pacific Americas flyway

Atlantic Americas flyway

East Atlantic flyway

Central Asia flyway

East Asia/ Australian flyway

East Africa West Africa flyway

Black Sea/ Mediterranean flywayDistricts with

H5N1 outbreaks since January 2005

Sources: AI outbreaks: OIE, FAO, and Government sources. Flyways: Wetlands International

H5N1 outbreaks in 2005 and major flyways of migratory birds(situation on 30 August 2005)

Influenza A subtypes: 16 Hemagglutnins (HA) 9 Neuramindases (NA)

All subtypes: endemic in birds

H1N1, H2N2, H3N2: endemic in people

HA trimers: Binds sialic acid and fuses viral and cell membranes

NA tetramers: Removes sialic acid to prevent adherence to self or cell during budding

Schematic Version of Influenza Virus (continued)

Schematic Version of Influenza Virus (continued)

RNA Polymerases (PB1, PB2, PA) attached to each RNP

Nucleoprotein (NP) binds RNA and Matrix protein (M1)

On viral and infected cell surface:

M2 tetramers Hydrogen ion channel

In infected cell: NS1 Binding host proteins Role in IFN resistance

Emergence of New Human Influenza Subtypes

H5N1 Virulence Factors in Mammals

HA with multibasic amino acid motif (RERRRKKR) at the HA1-HA2 cleavage site

Polymerase genes adapted to mammalian host 1997 H5N1 with PB2 lysine at AA position 627

2004 H5N1 with polymerases from human source more virulent in ferrets than same H5N1 with polymerases from avian source

NS1 gene adapted for mammalian host Inhibition of interferons

Increased TNF alpha

Source: Salomon et al. JEM 2006;203:689.

What Makes the HA Highly Pathogenic?

Source: Horimoto and Kawaoka. Nature Reviews Microbiology, 2005

Questions?

Common Features of H5N1 in Humans

Contact with sick/dying poultry

Frequently healthy young person Average age <18

Incubation period 2–4 days from probable exposure

Presenting symptoms fever, dyspnea, cough

Diarrhea more common than expected with influenza

Leukopenia/lymphopenia/thrombocytopenia

Metabolic abnormalities

Common Features of H5N1 in Humans (continued)

High frequency of progressive pneumonia Mostly primary viral

Occasional contribution of bacteria?• (Staphylococcus aureus and Haemophilus

influenzae)

Hepatic necrosis and acute tubular necrosis

High mortality rate in spite of antiviral/steroid/antibacterial treatment

Common Features of H5N1 in Humans (continued)

Diffuse activation of the innate immune system (“cytokine storm”) with increased levels of: Interleukin 1 beta

Interleukin 6

Interleukin 8

Tumor Necrosis Factor alpha

Interferon alpha

Interferon gamma

Interferon inducible protein 10

Soluble Interleukin 2 receptor

Monocyte chemoattractant protein 1

Source: Tran et al. N Engl J Med 350:1171, 2004

Chest Radiographs of Patient with Severe H5N1 Influenza Pneumonia: Vietnam, 2004

Additional H5N1 Virulence Factors in Humans

HA receptor binding

Two ketosidic linkages of sialic acid to galactose: alpha 2,3 and alpha 2,6

Avian HA preference for alpha 2,3 linkage

Human upper airway predominantly alpha 2,6 linkage

Human lower airway more abundant in alpha 2,3 linkage

Possibly contributes to the high incidence of primary viral pneumonia caused by H5N1 viruses

Source: Shinya et al. Nature 2006;440:435

Evidence for Person-to-Person H5N1 Transmission (Not Sustained)

Possible instances of infection of health care workers during 1997 outbreak in Hong Kong

Family clusters Vietnam, Thailand* and Indonesia**

Cluster in Indonesia suggests human to human to human transmission before the chain extinguished***

(* Ungchusak et al. N Engl J Med 2005;352:333-340

** Kandun et al. N Engl J Med 2006;355:2186-2194

***Normile Science 2006;312:1855)

Detection of H5N1 Viruses: Lessons from Recent Experiences Throat samples may give higher yield than nasal samples,

but both worth examining Rapid tests poor negative predictors and lack specificity

But microarray methods improving and may provide sensitivity and specificity

Polymerase chain reaction (PCR) increases sensitivity but success depends on the primers used for amplification

Laboratory confirmation generally accepted Viral culture Positive PCR for H5N1 RNA

• (see www.cdc.gov/mmwr/preview/mmwrhtml/mm5505a3.htm) Positive immunofluoresence using a monoclonal

antibody for H5 4-fold or greater rise in H5-specific antibody in

paired acute and convalescent sera

Questions?

Antiviral Therapies for Influenza

Antiviral Agents for Treatment of H5N1 Viruses

Early treatment recommended for suspect cases but efficacy, optimum dose, and duration uncertain

Treatment of choice is a neuraminidase inhibitor Oseltamivir has been most frequently used

• 5 days treatment of 75 mg twice daily for adults and dose decreases for children dependent on body mass is standard

• Higher doses may be considered by some authorities but no prospective studies

Oseltamivir resistance during treatment may not result in resistance to zanamivir

Antiviral Agents for Prophylaxis of H5N1 Viruses

Oseltamivir 75 mg once daily for 7–10 days may be considered for significant post exposure prophylaxis

But rationale is based on evidence from studies with other influenza A virus subtypes

Potential recipients would be poultry workers/cullers, health care workers, household contacts

Antiviral Agents for Treatment of H5N1 Viruses

Zanamivir administered as inhaled powder, which may be difficult with respiratory symptoms

Amantadine/rimantadine resistance common in Asian H5N1 viruses Possibly from agricultural use of drugs

Amantadine/rimantadine susceptibility of some recent strains (African/European/Middle East) May be clade specific May be a role for M2 inhibitors

Other drugs (ribavirin and interferon) may also be considered but no value clearly documented

Clinical studies in progress Peramivir (injectable neuraminidase inhibitor) CS8958 (once daily neuraminidase inhibior) 705 (polymerase inhibitor) Studies may start soon with FluDase (sialidase to remove viral receptors)

Pandemic Influenza Preparedness: Complementary Roles Within DHHS

Adults (18 – 64y; 7.5, 15, 45, 90ug)*

Immune response observed at all dose levels after a single dose, unadjuvanted vaccine

2 x 90mcg doses produced most frequent and highest antibody responses

April 17, 2007 FDA approval of sanofi vaccine at 90 mcg dose for persons exposed to H5N1

Additional studies in elderly (65y+; 45 or 90ug); children (2–9y; 45ug)

Immunogenicity results similar to adults

(* Treanor et al. N Engl J Med 2006; 354:1343-1351)

Adults (18 – 64y; 7.5, 15, 45, 90ug)*

Immune response observed at all dose levels after a single dose, unadjuvanted vaccine

2 x 90mcg doses produced most frequent and highest antibody responses

April 17, 2007 FDA approval of sanofi vaccine at 90 mcg dose for persons exposed to H5N1

Additional studies in elderly (65y+; 45 or 90ug); children (2–9y; 45ug)

Immunogenicity results similar to adults

(* Treanor et al. N Engl J Med 2006; 354:1343-1351)

NIH Trials with sanofi pasteur H5N1 A/Vietnam/1203/2004

Controlled trials completed or planned CSL Australia: subvirion vaccine +/- AlPO4

Baxter Austria: whole virus +/- AlOH

Novartis UK: subunit vaccine +/- AlOH

Sanofi France and US: subvirion vaccine +/- AlOH in adult and elderly populations

Summary Vaccines well tolerated with or without aluminum

adjuvant

Immunogenicity: Aluminum adjuvants do not show a clear advantage over vaccine alone

Controlled trials completed or planned CSL Australia: subvirion vaccine +/- AlPO4

Baxter Austria: whole virus +/- AlOH

Novartis UK: subunit vaccine +/- AlOH

Sanofi France and US: subvirion vaccine +/- AlOH in adult and elderly populations

Summary Vaccines well tolerated with or without aluminum

adjuvant

Immunogenicity: Aluminum adjuvants do not show a clear advantage over vaccine alone

Dose Optimization of Inactivated H5N1 Vaccines: Aluminum Adjuvants

Trials with other adjuvants

GSK: subvirion vaccine +/- AS (proprietary adjuvant system)

Novartis UK: subunit vaccine with MF59 (proprietary adjuvant system

Summary

Vaccines well tolerated with or without adjuvant but somewhat increased local reactogenicity

Immunogenicity: Adjuvants result in more frequent and higher antibody responses

Trials with other adjuvants

GSK: subvirion vaccine +/- AS (proprietary adjuvant system)

Novartis UK: subunit vaccine with MF59 (proprietary adjuvant system

Summary

Vaccines well tolerated with or without adjuvant but somewhat increased local reactogenicity

Immunogenicity: Adjuvants result in more frequent and higher antibody responses

Dose Optimization of Inactivated H5N1 Vaccines: Other Adjuvants

Trials with other alternate route of administration

Sanofi subvirion vaccine given intradermal (ID) at reduced dose or intramuscular (IM) at higher dose

Summary

Vaccines well tolerated but increased local reactogenicity with intradermal administration

Immunogenicity: High doses IM more immunogenic than lower doses ID

Additional studies planned for better direct comparison of same dose given ID and IM

Trials with other alternate route of administration

Sanofi subvirion vaccine given intradermal (ID) at reduced dose or intramuscular (IM) at higher dose

Summary

Vaccines well tolerated but increased local reactogenicity with intradermal administration

Immunogenicity: High doses IM more immunogenic than lower doses ID

Additional studies planned for better direct comparison of same dose given ID and IM

Dose Optimization of Inactivated H5N1 Vaccines: Route

Source: The WHO Global Influenza Program Surveillance Network

Clade 1 vaccine; trials underway Vaccine candidates: A/VN/1203/2004 and A/VN/1194/2004

Clade 2 - subclade 2 candidates available; vaccine production ongoing CDC: Indonesia/05 (Sanofi US; DHHS) NIBSC: A/Turkey/Turkey/1/05

St. Jude: A/BHG/Qinghai Lake/1A/2005 and A/WS/Mongolia/244/05

Clade 2 - subclade 3 candidates in development CBER/FDA: A/Duck/Laos/3295/06 CDC: A/Anhui/1/2005 St. Jude: A/Japanese White Eye/HK/1038/06

Clade 1 vaccine; trials underway Vaccine candidates: A/VN/1203/2004 and A/VN/1194/2004

Clade 2 - subclade 2 candidates available; vaccine production ongoing CDC: Indonesia/05 (Sanofi US; DHHS) NIBSC: A/Turkey/Turkey/1/05

St. Jude: A/BHG/Qinghai Lake/1A/2005 and A/WS/Mongolia/244/05

Clade 2 - subclade 3 candidates in development CBER/FDA: A/Duck/Laos/3295/06 CDC: A/Anhui/1/2005 St. Jude: A/Japanese White Eye/HK/1038/06

Keeping up with H5N1 Drift: Vaccine Reference Virus Efforts Underway

Questions?

What Can We Expect of H5N1 Influenza?

Since 2003, increasing number of countries in Africa, Asia, and Europe have documented H5N1 virus in poultry or migratory birds.

Continued H5N1 evolution, possibly amplified by uncontrolled transmission in high-density poultry.

Human cases track exposure to infected poultry and are accelerating in frequency.

Clusters and potential human-to-human spread plus epidemic influenza provide continuing chance for reassortment.

Hong Kong model for eliminating infected poultry and preventing human illness

Agricultural surveillance and action are critical early steps.

Enforcement of market sanitation.

Poultry segregation (quail as asymptomatic carriers eliminated).

Vaccination with agricultural vaccine (asymptomatic infections possible).

Difficult to implement because of social and economic concerns.

Annual Influenza Vaccine Production

Coordinated collaborative

&complex!

PHSstrain

selection

Global surveillance

(ongoing)

WHO strain

selection

Generation of highyield reassortants

“candidates”

FDA release testing

FDA potencyreagents

Filled into vials/syringes

FDA approvessupplement to

license

Formulated lots

Sheep sera

Millions of fertilized

eggs

Standardantigen

Millions of chickens

Bulk vaccine

production

~1 rooster for 10 hens

Antigenic relatednessconfirmed

Distribution/vaccine use

PurifiedHA

Manufacturersassess growth &

yield of candidates

? Demand

? Severity of Season

? Recommendations

Future:

revers

e

genetics

technology

Influenza Vaccine Production Timeline

U.S. Seasonal Influenza Vaccine: Production and Use

Beyond Eggs and Cell Culture: Research Efforts to Develop New Technologies

Goal: Develop “agile” vaccine platformsDNA

Plasmids – single or multiple gene combinations (HA + NP + M2); conserved regions; single subtype or multiple subtypes (H3 + H1 + H5)

VectorAdenovirus, alphavirus, salmonella strains

Recombinant subunitExpression systems, baculovirus, drosophila

Peptide vaccinesSynthesized multigenic peptides

Vector-based vaccines

Influenza Virus and Protein RNAs: Targets for a “Universal Vaccine”

Source: Subbarao/Murphy

Seasonal Influenza

Preparedness

Pandemic Influenza

Preparedness