1. Dengue virus Huan-Yao Lei, Ph.D.
Department of Microbiology & Immunology,
College of Medicine, National Cheng Kung University
Tainan, Taiwan

2. Dengue virus infection:
Dengue epidemiology
Disease control and surveillance
Pathogenesis (Immunopathogenesis)
Antibody-dependent enhancement
Development and challenge of Dengue vaccine
Development of anti-dengue virus drug ?

3. Several important features of dengue disease
Dengue virus infection causes diverse disease spectrum from mild DF to severe DHF/DSS.
Dengue disease can occur in infant, children, and adult.
Severe DHF/DSS is more prevalent in secondary infection with different serotype of dengue virus.
Antibody-dependent enhancement is hypothesized to explain the severe DHF/DSS in secondary infection.
Thrombocytopenia and plasma leakage are two major characteristics of DHF/DSS.
The pathogenesis of DHF/DSS is not clearly demonstrated. The progression from DF to DHF/DSS is not predictable.
Supportive care is the only way to treat the DHF/DSS patients.
Dengue vaccine is not commercially available yet.

4. Infant (5%) Children (85%) Adult (10%) Comparative study
Immune immature
Primary infection
Maternal antibody effect
ADE hypothesis
Secondary infections with different serotypes
Higher case fatality rate in elder in Taiwan
Comparative study
The pathogenesis for DHF/DSS has to account for all these three entities in dengue virus infection.

5. Population Infection Clinical Cases DHF/DSS Asymptomatic DF (non-DHF)
survive
Death 5%
24% 6%
0.8%
76%
94%
99.2%
Fig. 1 Rates in dengue model
by Shepard et al. Vaccine. 2004, 22:

6. Unique features of dengue disease in Taiwan
Dengue outbreak starts by imported case from abroad, spread out locally, then distinguish in the winter. This transmission pattern repeats every year.
Put all efforts to eliminate breeding sources and control of infectant mosquitoes.
Dengue disease primarily occur in adult.
Dengue virus-infected elders with underlined diseases have high case fatality of DHF.
Most clinicians are not familiar with the pathogenesis of dengue disease, and sometime have over or inappropriate medical treatment.
The progression from DF to DHF/DSS is not predictable.
Dengue vaccine is not commercially available or considered yet.

7. Age-specific DHF/DSS hospitalization in children and infant.
Halstead SB et al. Am J Trop Med Hyg 1969, 18:

8. DF DHF/DSS Fatal
Age-specific prevalent rate of DF, DHF/DSS and fatal cases in 2002 Kaohsiung outbreak.

9. The role of antibodies on dengue disease
Ab-dependent enhancement
Old dogma for dengue virus-induced DHF/DSS
Anti-prM Ab by its dual-specific binding of dengue virus and target cells to enhance the dengue virus infection.
Enhancing antibodies are concentration-dependent and serotype-independent..
Affected the design of dengue virus vaccine development..
Pathogenic autoantibody
Acute dengue virus infection induces autoantibody production
Anti-dengue Abs cross-react with platelet and endothelial cell, and cause a transient hemophagocytic-like syndrome.
Will have great impact on safety of dengue vaccine

10. Antibody-dependent Enhancement in Dengue Virus Infection: An Old but Unresolved Dogma
Enhance the dengue-infected cell mass.
Enhance the dengue virus replication?
Suppress the anti-viral activity via FcRII signaling?
The characteristics of the enhancing antibody?
The target cells: requirement of receptors other than FcR?
The dengue virion: E or prM? Which epitope?

11. Anti-prM antibody: 1. Enhancing 2. Neutralization Anti-E antibody:
2. Sub-neutralization
3. Enhancing
EMBO J 2003, 22:2604

12. ADE of dengue virus infection
Anti-E Ab/Anti-prM Ab on FcR-bearing cells via FcgR-dependent manner
Anti-prM Ab on non-FcR-bearing cells via dual specific binding
Enhancing antibodies for ADE are concentration-dependent, and serotype-independent.

13. Dengue infection: Immunopathogenesis
Immune deviation
Cytokine over-production
Dengue virus-induced vasculopathy
Dengue virus-induced coagulopathy
Anti-platelet autoantibody
Anti-endothelial cell autoantibody
Molecular mimicry
Dengue virus infects monocytes and B cells

14. Representative CD4-TCRab, CD8-TCRab plots in two dengue patients.
DHF
(patient 2)
9 month afterward DF
(patient 5)
CD4
TCRab
CD8
TCRab
Representative CD4-TCRab, CD8-TCRab plots in two dengue patients.

15. Kinetic changes of CD4+ ( ), CD8+ T ( )lymphocytes, CD4/CD8
D day -3 3 6 9 12
>250 80
2.0
patient 2 70 60
1.5 50
CD4/CD8 ratio, 40
1.0
percentage (%) 30 20
0.5 10 6 9 12 15 18 21
>250
F day
Kinetic changes of CD4+ ( ), CD8+ T ( )lymphocytes, CD4/CD8
ratio ( ), CD4dim or CD8dim monocytosis ( )in dengue patient 2.

16. Table 1. Summary of in 10 of 29 cases with CD4/CD8 ratio inversion.

17. Transient high elavation of IFN-g in DHF children
200
400
600
800
1000
1200
IFN-g (pg/ml)
Day
… Control
( n = )

18. Transient high elevation of IL-10 in DHF children50
100
150
200
250
IL-10 (pg/ml)
… Control
Day
( n = )

19. Th1/Th2 Cytokine profile in DHF patients
Infants (primary) Children (secondary)
* IFN-  (high)   (high) 
* TNF-  (mild) No
* IL  (high)   (high) 
* IL  (moderate) No
* IL-4, IL-2 No No

20. IFN-g IL-10 IL-6 Activated Hemophagocytic activity EC Vascular leakage
Activated PLT
CD69 M
Anti-E
Anti-prM
Anti-NS1
Activated EC
Thrombopcytopenia
Hemophagocytic activity

21. Issues need to be addressed in the next class:
Why dengue is not controllable worldwide?
Any measure for Taiwan’s dengue control and surveillance?
Pathogenesis or immunopathogenesis?
The mechanism of antibody-dependent enhancement?
Dengue virus infection and autoimmunity?
The prospect of Dengue vaccine development?
The need for anti-dengue virus or disease treatment?

22. Thank You for Your Attention