In dengue infection, antibody-dependent enhancement (ADE) is most likely to occur in a child with which serological profile during secondary dengue infection?

Explanation

## Antibody-Dependent Enhancement (ADE) in Dengue **Key Point:** ADE occurs when non-neutralizing, cross-reactive IgG antibodies from a prior dengue infection with a different serotype bind to the virus but fail to neutralize it. This allows the virus-antibody complex to enter macrophages and dendritic cells via Fc receptors, enhancing viral replication. **High-Yield:** ADE is the mechanism explaining why secondary dengue infection (especially with a different serotype) carries a higher risk of DHF/DSS compared to primary infection. This is a critical concept in pediatric dengue epidemiology. ### ADE Mechanism ```mermaid flowchart TD A[Primary dengue infection<br/>Serotype 1]:::outcome --> B[IgG antibodies produced<br/>Cross-reactive to Serotype 2]:::outcome B --> C[Secondary infection<br/>with Serotype 2]:::outcome C --> D{Antibody characteristics?}:::decision D -->|Neutralizing| E[Virus neutralized<br/>No enhancement]:::action D -->|Non-neutralizing| F[Virus-IgG complex<br/>binds Fc receptors]:::action F --> G[Enhanced entry into<br/>macrophages/dendritic cells]:::action G --> H[Increased viral replication<br/>Higher viremia]:::urgent H --> I[Severe DHF/DSS]:::urgent ``` **Clinical Pearl:** The "original antigenic sin" phenomenon explains why children with prior dengue exposure are at highest risk for severe dengue during secondary infection. The immune system preferentially produces antibodies to the first serotype encountered, which are poorly neutralizing against subsequent serotypes. **Mnemonic:** **ADE = CROSS-REACTIVE + NON-NEUTRALIZING** — Remember that ADE requires BOTH cross-reactivity (from prior infection) AND failure to neutralize (allowing Fc receptor–mediated entry).