dengue virus: no one is safe caitlin reed smith college april 29, 2005
TRANSCRIPT
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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