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Christian W. MandlInstitute of Virology

Medical University of Vienna, AUSTRIA

Flaviviruses – New Challenges, New Vaccines

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Family Flaviviridae

• Genus Hepacivirus• Genus Pestivirus• Genus Flavivirus (>70 members)

– Yellow fever virus– Dengue virus (types 1 - 4)– Usutu virus– Japanese encephalitis virus– West Nile virus– St. Louis encephalitis virus– Murray Valley encephalitis virus– Rocio virus– Tick-borne encephalitis virus– Louping ill virus– Powassan virus– Omsk hemorrhagic fever virus

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Family Flaviviridae

• Genus Hepacivirus• Genus Pestivirus• Genus Flavivirus (>70 members)

– Yellow fever virus– Dengue virus (types 1 - 4)– Usutu virus– Japanese encephalitis virus– West Nile virus– St. Louis encephalitis virus– Murray Valley encephalitis virus– Rocio virus– Tick-borne encephalitis virus– Louping ill virus– Powassan virus– Omsk hemorrhagic fever virus

Vector: Mosquito

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Family Flaviviridae

• Genus Hepacivirus• Genus Pestivirus• Genus Flavivirus (>70 members)

– Yellow fever virus– Dengue virus (types 1 - 4)– Usutu virus– Japanese encephalitis virus– West Nile virus– St. Louis encephalitis virus– Murray Valley encephalitis virus– Rocio virus– Tick-borne encephalitis virus– Louping ill virus– Powassan virus– Omsk hemorrhagic fever virus

Vector: Tick

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Family Flaviviridae

• Genus Hepacivirus• Genus Pestivirus• Genus Flavivirus (>70 members)

– Yellow fever virus– Dengue virus (types 1 - 4)– Usutu virus– Japanese encephalitis virus– West Nile virus– St. Louis encephalitis virus– Murray Valley encephalitis virus– Rocio virus– Tick-borne encephalitis virus– Louping ill virus– Powassan virus– Omsk hemorrhagic fever virus

Hemorrhagicfever

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Family Flaviviridae

• Genus Hepacivirus• Genus Pestivirus• Genus Flavivirus (>70 members)

– Yellow fever virus– Dengue virus (types 1 - 4)– Usutu virus– Japanese encephalitis virus– West Nile virus– St. Louis encephalitis virus– Murray Valley encephalitis virus– Rocio virus– Tick-borne encephalitis virus– Louping ill virus– Powassan virus– Omsk hemorrhagic fever virus

Neurologicaldisorders

Encephalitis

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Family Flaviviridae

• Genus Hepacivirus• Genus Pestivirus• Genus Flavivirus (>70 members)

– Yellow fever virus– Dengue virus (types 1 - 4)– Usutu virus– Japanese encephalitis virus– West Nile virus– St. Louis encephalitis virus– Murray Valley encephalitis virus– Rocio virus– Tick-borne encephalitis virus– Louping ill virus– Powassan virus– Omsk hemorrhagic fever virus

Neurologicaldisorders

Encephalitis

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Flaviviruses

Yellow feverDengue

Tick-borne encephalitisJapanese encephalitis

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Flaviviruses

Yellow feverDengue

Tick-borne encephalitisJapanese encephalitis

West Nile

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West Nile virus in the United States

1999 …

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West Nile virus in the United States

… 2001 …

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West Nile virus in the United States

… 2003 …

9,862 cases, 264 deaths

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West Nile virus in the United States

… 2005

2004 – 2006: ~ 3,000 cases, 100 deaths per year

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West Nile virus transmission cycle

USA 2003: WN virus found in• 43 mosquito

species• 234 native and

captive exotic birds

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Flaviviruses

Yellow feverDengue

Tick-borne encephalitisJapanese encephalitis

West Nile

Usutu virus

Weissenbock, Kolodziejek, Url, Lussy, Rebel-Bauder, Nowotny. Emerg Infect Dis. 2002:652

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Flaviviruses

Yellow feverDengue

Tick-borne encephalitisJapanese encephalitis

West Nile

Usutu virus

Bakonyi, Hubalek, Rudolf, Nowotny. Emerg Infect Dis. 2005:225

Rabensburgvirus?

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Flaviviruses ...

… are pathogens of global importance.… are emerging pathogens that can conquer new

ecological niches.… are considered potential bioterroristic

weapons.

• There is no specific treatment for flavivirusinfections.

• There is a big and growing demand for vaccines.

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Flavivirus particle

• Small (50 nm), round, enveloped• Nucleocapsid (RNA genome and protein C)• Two surface proteins (M and E)

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Flavivirus particle

• Small (50 nm), round, enveloped• Protein E arranged in icosahedral lattice –• Main target for neutralizing antibodies

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Distribution map of Japanese encephalitisvirus

1983

1955

1970

1990

1985

1935

1965

1960

1952

1949

1947

1998

1990

1995

1870s (1935)

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JEV transmission cycle

No person-to-person transmissionCulex tritaeniorhyncus

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Japanese encephalitis fact sheet

• Most important recognised cause of viral encephalitis in Asia

• ~ 50,000 cases reported annually (probably heavily underreported)

• Only 1 in ~ 250 infections results in clinical disease

• Case-fatality rate: 30%

• Serious neurologic sequelae: 30%

• 3 Billion people live in endemic areas

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Travelers to JEV endemic areas

USA, ~8 million

Europe, ~20 million

Australia,~3 million

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Existing JEV vaccines (1/2)

Inactivated JEV wild-type virus from suckling mouse brain

• JE-VAX®: Biken / SanofiPasteur (and other local manufacturers)• Very successful (JE nearly eliminated in several countries)

However• Traces of myelin basic protein• Local reactions (20%)• Systemic symptoms, headache, fever etc. (20%)• Sporadic cases of acute disseminated encephalomyelitis??• 2005: Recommendation for childhood vaccination withdrawn in

Japan• 2004: Production in Japan discontinued

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Existing JEV vaccines (2/2)

Inactivated JE wild-type virus produced in cell culture

Live virus vaccine based on attenuated strain SA14-14-2

• Many million doses of both vaccines used in China.

However• Unresolved safety issues• Primary hamster kidney cells not approved by WHO for human

vaccine production• Production lacks purification steps• Not used in Western world

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New JEV vaccines (1/2)

Live virus vaccine based on a YFV-JEV chimeric strain

• Chimerivax®-JE: Acambis• Surface proteins M and E of YF-17D vaccine strain replaced

by the corresponding proteins from JEV strain SA14-14-2

Vaccinia virus vectored vaccine• MVA-BN®-JE: Bavarian Nordic• JEV surface proteins expressed from Modified Vaccinia Ankara

strain

Genetically engineered, live viruses

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New JEV vaccines (2/2)

Inactivated JEV produced in Vero cells• JEV-IC51: Intercell• Vero cells (originally from African green monkey kidney) are used

worldwide for human, e.g. polio, vaccine production.• Attenuated strain SA14-14-2 used as seed virus

2-Dose3-DoseVaccinationSchedule

Prefilled SyringeVialFormatLiquidLyophilizedFormulationNoneThimerosalPreservativeAlumNoneAdjuvantNonePorcine GelatinStabilizers

Vero CellsMouse BrainVirus GrowthAttenuatedVirulentVirus Seed

JE-PIVJE-VAX®

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Distribution map of tick-borne encephalitis virus

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TBEV vaccines

Formalin-

inact. Virus

Al ( OH )3

Stabilizer

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TBE in Austria and Czech Rep.1979 - 2005

1979 81 83 85 87 89 91 93 95 97 99 01 03 050

100

200

300

400

500

600

700

Years

Number of cases

Czech Rep. Austria

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Flaviviruses

Yellow feverDengue

Tick-borne encephalitisJapanese encephalitis

West Nile

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A new technology to generate attenuated flavivirus strains

Virus particle

>

Subviral particle

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A new technology to generate attenuated flavivirus strains

Virus particle

<Subviral particle

This strategy is currently applied to West Nile virus in a preclinical collaborative study between Intercell and the Institute of Virology

Capsiddeletion

mutations

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