Dengue virus

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%) 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 5% Infection 24% 76% Clinical Cases Asymptomatic Infection 6% 94% DHF/DSS DF (non-DHF) 0.8% 99.2% survive Death Fig. 1 Rates in dengue model by Shepard et al. Vaccine. 2004, 22:1275-1280.

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, 18:997-1021.

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

9. 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 The role of antibodies on dengue disease

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

15. D day -3 0 3 6 9 12 >250 2.0 80 patient 2 70 1.5 60 50 CD4/CD8 ratio, 40 1.0 percentage (%) 30 20 0.5 10 0 0 12 15 18 21 >250 6 9 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. 1200 1000 800 600 400 200 0 Transient high elavation of IFN-g in DHF children IFN-g (pg/ml) 3 4 5 6 7 8 9… Control Day ( n = 1 7 12 15 2 2 14 4 )

18. 250 200 150 100 50 0 Transient high elevation of IL-10 in DHF children IL-10 (pg/ml) 3 4 5 6 7 8 9… Control Day ( n = 1 7 12 15 2 2 14 4 )

19. Th1/Th2 Cytokine profile in DHF patients Infants (primary) Children (secondary) * IFN-  (high)   (high)  * TNF-  (mild)No * IL-10  (high)   (high)  * IL-6  (moderate)No * IL-4, IL-2 NoNo

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

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 Youfor Your Attention