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

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 ?

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.

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.

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, 22:1275-1280.

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.

Age-specific DHF/DSS hospitalization in children and infant. Halstead SB et al. Am J Trop Med Hyg 1969, 18:997-1021.

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

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

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?

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

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.

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

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.

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.

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

Transient high elavation of IFN-g in DHF children 200 400 600 800 1000 1200 IFN-g (pg/ml) Day 3 4 5 6 7 8 9… Control ( n = 1 7 12 15 2 2 14 4 )

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

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 No No

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

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?

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