DENGUE VIRUS: NO ONE IS SAFE

Caitlin ReedSmith CollegeApril 29, 2005

www.invivo.fiocruz.br/dengue/home_dengue.htm

OVERVIEW OF THEMES

Background Information

Clinical Presentation & Diagnosis

Biology

Vaccination Prospects

Public Health

WHAT IS DENGUE?WHAT IS DENGUE?

Flavivirus (type of arbovirus)Flavivirus (type of arbovirus)

Transmitted from Transmitted from Aedes aegyptiAedes aegypti and and Aedes albopictusAedes albopictus mosquitoes mosquitoes

Four Serotypes (Dengue 1-4)Four Serotypes (Dengue 1-4)

DENGUE (cont’d)DENGUE (cont’d) Three Manifestations:Three Manifestations:

1. Dengue Fever1. Dengue Fever

2. Dengue Hemorrhagic Fever2. Dengue Hemorrhagic Fever

3. Dengue Shock Syndrome3. Dengue Shock Syndrome

Leads to death in 5% of cases Leads to death in 5% of cases

More dangerous if infected second More dangerous if infected second time by different serotypetime by different serotype

WHY DO WE CARE ABOUT WHY DO WE CARE ABOUT DENGUE?DENGUE?

CDC Category A Infectious DiseaseCDC Category A Infectious Disease Infects 50-100 million people every Infects 50-100 million people every

yearyear About half the world lives in a “hot About half the world lives in a “hot

zone”zone” Very hard to create vaccineVery hard to create vaccine Mosquito evolution = Mosquito evolution =

threat to U.S. threat to U.S. Global warmingGlobal warminghttp://klab.agsci.colostate.edu/aegypti/

aegypti.html

WHY NOW?WHY NOW?

Failed eradication attempt in the Americas in 1970

Previously unestablished serotypes are establishing themselves in various countries

Recent Outbreaks:1. India, 20032. Hawaii, 20013. Taiwan, 20014. Puerto Rico, 1994-1995

WHERE IS DENGUE WHERE IS DENGUE FOUND?FOUND?

www.traveldoctoronline.net/diseases/dengue.htm

DENGUE DENGUE TRANSMISSITRANSMISSI

ON ON

1. Mosquitoes transmitdengue to human dendriticcells

2. Dengue targets areaswith high WBC counts(liver, spleen, lymph nodes, bone marrow, andglands)

3. Dengue enters

WBCs & lymphatic

tissue

4. Dengue enters bloodcirculation

3

4

1

2

http://phil.cdc.gov/PHIL_Images/08051999/00004/dengue_phf/sld006.htm

3

HOW DENGUE SPREADS

CLINICAL CLINICAL PRESENTATIOPRESENTATION OF DENGUEN OF DENGUE

SYMPTOMSSYMPTOMS OF DHF OF DHF

GRADE I: Fever with other symptoms such as vomiting, headache, muscle and joint pain: positive tourniquet test is the only evidence of hemorrhaging

GRADE II: Grade I symptoms + spontaneous bleeding

GRADE III*: Failure of circulatory system, clammy skin, rapid & weak pulse, restlessness

GRADE IV*: Severe shock, no measurable blood pressure or pulse

*Considered Dengue Shock Syndrome (DSS)

DENGUE GRADATIONDENGUE GRADATION

http://w3.whosea.org/en/Section10/Section332/Section554_2564.htm

http://www.cdc.gov/ncidod/dvbid/dengue/slideset/set1/images/petechiae2-small.jpg

P E T E C H I A E

P U R P U R A

http://www.pediatrics.wisc.edu/education/derm/tutb/85m.jpg

http://www-medlib.med.utah.edu/WebPath/ATHHTML/ATH036.html

E C C H Y M O S I S

http://www.cgste.mq/brainstorm/dengue/image/hemo.gif

NASAL HEMORRHAGING

BIOLOGY OF BIOLOGY OF DENGUEDENGUE

http://www.stanford.edu/group/virus/flavi/2000/deng_em.jpg

BASIC BIOLOGYBASIC BIOLOGY Single, positive-Single, positive-

stranded RNA stranded RNA surrounded by an surrounded by an icosahedral coreicosahedral core

90 glycoprotein E 90 glycoprotein E dimers overly M dimers overly M proteinsproteins

Protein E is most Protein E is most important important characteristic of characteristic of denguedengue

Modis, Ogata, Clements, et. al., 2004

BASIC DENGUE BASIC DENGUE GENOMEGENOME

http://microvet.arizona.edu/Courses/MIC419/VaccProp05html/Dengue.html

FUSION PROTEIN EFUSION PROTEIN E

Modis, Ogata, et. al., 2004.

IMMUNE IMMUNE RESPONSERESPONSE

http://www.ethal.org.my/opencms/opencms/ethal/Images/MedGeneralImages/Lymphocyte.jpg

FIRST INFECTIONFIRST INFECTION Humoral and cellular immune Humoral and cellular immune

responseresponse

- Ab serum neutralizing levels - Ab serum neutralizing levels increaseincrease

- T-lymphocytes activated by - T-lymphocytes activated by dendritic dendritic cellscells

- Memory cells develop - Memory cells develop antibodies to antibodies to fight off future fight off future infection of same infection of same serotypeserotype

SECOND INFECTIONSECOND INFECTION

Antibody dependent Antibody dependent enhancementenhancement

- Enhancing immunoglobulin - Enhancing immunoglobulin G (IgG) G (IgG) antibodiesantibodies

- Fc Receptors- Fc Receptors

CELLULAR CELLULAR LEVEL OF LEVEL OF DENGUE DENGUE FUSIONFUSION

ENTRY INTO CELLENTRY INTO CELL

Dengue infectionDengue infection

Endosome entry & pH changeEndosome entry & pH change

E protein conformational changeE protein conformational change

Release of viral RNA into cellRelease of viral RNA into cell

Replication & further infection Replication & further infection

PRE-FUSION

POST-FUSION

PROTEIN E CONFORMATIONAL CHANGE

Modis, Ogata, et. al., 2004

PROTEIN E INSERTION PROTEIN E INSERTION INTO PMINTO PM

http://crystal.med.harvard.edu/cover_modis_vsmall.jpgModis, Ogata, et. al., 2004.

VIRAL REPLICATIONVIRAL REPLICATION

http://chen.bio.purdue.edu/images/flavi/viruslifecycle.jpg

TO TO SUMMARIZESUMMARIZE

……THE BODY’S THE BODY’S RESPONSE TO A RESPONSE TO A

DENGUE INFECTIONDENGUE INFECTION

DENGUE IN THE CELLDENGUE IN THE CELL

Dendritic cell infection Dendritic cell infection T-cell T-cell activationactivation

Previous infection = increase in Previous infection = increase in viral load and decrease in viral load and decrease in incubation periodincubation period

ADE is problem for 20 years after ADE is problem for 20 years after first infectionfirst infection

PATHOGENIC STRATEGIES PATHOGENIC STRATEGIES OF DENGUE OF DENGUE

Invades circulatory system, causing:

- vascular permeability

- Disseminated intravascular coagulation

- Potentially death

http://www.ehu.es/biomoleculas/PROT/blood-clot.gif

DENGUE DENGUE DIAGNOSISDIAGNOSIS

http://bensguide.gpo.gov/images/ben/ben_doctor.jpg

LABORATORY DIAGNOSIS LABORATORY DIAGNOSIS OF DENGUEOF DENGUE

METHODS:

1. Viral Isolation & Characterization

2. Genomic Sequencing

3. Antibody Detectionwww.synergene.net/de/images/

dnasmall.jpg

VIRAL ISOLATION & VIRAL ISOLATION & CHARACTERIZATIONCHARACTERIZATION

Old “Gold Standard”Old “Gold Standard” Cell Culture (mammals Cell Culture (mammals

& mosquitoes)& mosquitoes)-Indirect -Indirect

ImmunofluorescenceImmunofluorescence Useful to study basic Useful to study basic

virology, epidemiology,virology, epidemiology,and pathogenesisand pathogenesis

Impractical for rapid Impractical for rapid diagnosis & treatmentdiagnosis & treatment

http://www.cdc.gov/ncidod/dvbid/dengue/slideset/set1/image/virus-isolation-cell-culture2.jpg

GENOMIC SEQUENCINGGENOMIC SEQUENCING

Quicker, more reliable Quicker, more reliable means of diagnosismeans of diagnosis

NASBA method (RNA-NASBA method (RNA-specific amplification specific amplification assay)assay)

RT-PCR method to provide RT-PCR method to provide most accuracy, uses 5’-3’ most accuracy, uses 5’-3’ nuclease oligonucleotide nuclease oligonucleotide probe (which may not be probe (which may not be able to distinguish among able to distinguish among serotypes) – new “Gold serotypes) – new “Gold Standard”Standard”

Beware of false-positives Beware of false-positives due to contaminationdue to contamination

http://animal.intron.co.kr/Image/RT-pcr.gif

ANTIBODY DETECTIONANTIBODY DETECTION

Most common Most common methodsmethods1. Hemagglutinin 1. Hemagglutinin inhibition test (HI test)inhibition test (HI test)

2. ELISA2. ELISA

3. Rapid 3. Rapid immunochromatograpimmunochromatography test hy test (commercial kits (commercial kits available) available)

http://webdb.dmsc.moph.go.th/ifc_nih/applications/pics/Qualitative_test.jpg

VACCINE VACCINE DEVELOPMENT AND DEVELOPMENT AND

PUBLIC HEALTH PUBLIC HEALTH STRATEGIESSTRATEGIES

STOPPING STOPPING DENGUEDENGUE

MOST PROMISING MOST PROMISING VACCINEVACCINE

ChimeriVax-ChimeriVax-DengueDengue

- Tetravalent- Tetravalent

- Uses yellow - Uses yellow fever fever vaccine vaccine as baseas base

- 92% of - 92% of monkeys monkeys passed passed “virulent “virulent virus challenge”virus challenge”

Guirakoo, Pugachev, and Zhang, 2004

WHAT ABOUT HUMANS?WHAT ABOUT HUMANS?

Tetravalent Tetravalent vaccinevaccine ChimeriVax-ChimeriVax-

Dengue?Dengue? 20% 20%

seroconversion rateseroconversion rate

More research More research necessary!necessary!

http://www.lung.ca/pneumonia/images/doc2.gif

PUBLIC HEALTH PUBLIC HEALTH STRATEGIES STRATEGIES

Vector Control

Surveillance

Preparation for outbreaks

Research

NON-BIOLOGICAL MEANS OF DECREASING THE

INCIDENCE OF DENGUE

w3.whosea.org/extrelations/ images/Bed%20net.jpg

MOSQUITO MOSQUITO NETSNETS

NO MORE NO MORE MOSQUITOES!MOSQUITOES!

www.mosquitobarrier.com/ images/tincan.jpg

www.headlice.org/ images/unsanitary.jpg

ABOUT THAT STANDING WATER…

“Children play in sewage in Nairobi's sprawling Mukuru

Kaiyaba slum.”

http://www.alertnet.org/thefacts/reliefresources/108273140124.htm

IMPEDIMENTSIMPEDIMENTS

Still lack complete understanding Still lack complete understanding of dengue virus virulenceof dengue virus virulence

Social/socioeconomicSocial/socioeconomic Travel spreads different serotypesTravel spreads different serotypes Demographic changesDemographic changes Decentralized and therefore weak Decentralized and therefore weak

public health systemspublic health systems

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