Comparison of Flu Viruses: Why Some Influenza Viruses Are More Dangerous Than Others

Understanding Severe Influenza Infections

• 🦠 Influenza A viruses are responsible for over 100,000 influenza cases in Germany annually.
• ⚠️ Particularly severe influenza cases are characterized by an excessive immune response, known as a cytokine storm.
• 💡 During a cytokine storm, the body overproduces messenger substances, specifically type I interferons, which promote infection severity and can lead to fatalities.

Research Question and Approach

• 🔍 The research focused on why some influenza strains cause serious infections and cytokine storms, while others result in only mild cases.
• 🔬 To address this, researchers compared eleven different influenza strains, including common seasonal viruses and dangerous highly pathogenic avian influenza viruses.
• 🧪 They infected various types of human immune cells with these viruses to observe their effects.

Key Immune Cell Discoveries

• 🎯 Surprisingly, plasmacytoid dendritic cells, a main producer of type I interferon, showed high production regardless of the influenza strain used.
• 🦠 The study found that myeloid dendritic cells and macrophages are primarily infected by highly pathogenic influenza strains.
• 🔥 Infections of these specific cells by dangerous strains are accompanied by a strong production of type I interferon.
• 📉 In contrast, low pathogenic seasonal virus strains did not lead to type I interferon release in myeloid dendritic cells and macrophages.

Implications for Immune Response

• 🧠 These findings highlight that myeloid dendritic cells and macrophages, previously not the focus, could be decisive in triggering an excessive immune system response.
• ✅ This research may help in the future to better assess the risk of dangerous virus variants.