Crosstalk: waning immunity against Japanese encephalitis worsens dengue, Pg2

Key Highlights:

• A recent study reveals that waning immunity to Japanese Encephalitis Virus (JEV) can increase the severity of dengue fever.
• The study, conducted in Nepal between 2019 and 2023, examined the link between JEV immunity and dengue outcomes.
• Researchers found that individuals with mid-range anti-JEV antibody titres (1:160) had a 3x higher risk of developing dengue fever with warning signs.
• The study suggests that timely JE vaccine boosters could help mitigate the severity of dengue in regions where JEV vaccination is common.

Detailed Insights:

• The study was conducted in Nepal, a unique setting with high JEV immunity due to a successful vaccination program since 2006, but limited prior exposure to dengue.
• Researchers measured chymase levels, an enzyme released during inflammation, as a biomarker for severe dengue, confirming its elevation during both acute and defervescence phases.
• Moderate levels of anti-JEV antibodies may enhance viral infection and worsen disease, while very high levels are protective, echoing observations in studies of Zika and dengue viruses.
• Rising temperatures and extended monsoons are changing the epidemiology of dengue fever, leading to bigger outbreaks, requiring countries like India to prepare appropriate strategies.
• The study reinforces the importance of chymase as a biomarker for severe dengue, aiding physicians in managing the uncertain trajectories of the disease.

Scientific/Technical Concepts Involved:

• Japanese Encephalitis Virus (JEV): A mosquito-borne flavivirus that can cause encephalitis.
• Dengue Virus: A mosquito-borne flavivirus with four serotypes, causing dengue fever.
• Antibody-dependent enhancement: A phenomenon where antibodies from a previous infection worsen a subsequent infection.
• Chymase: An enzyme released by mast cells during inflammation, used as a biomarker for severe dengue.