Immune evasion strategies

Definition

Immune evasion strategies are tactics used by viruses to avoid detection and destruction by the host's immune system. These strategies can manipulate various components of the immune response, leading to a successful infection and persistence in the host. By employing these mechanisms, viruses can undermine the innate immune responses, which serve as the first line of defense against viral infections.

5 Must Know Facts For Your Next Test

1. Viruses can inhibit the production or function of interferons, which are crucial for mounting an effective innate immune response.
2. Some viruses can downregulate major histocompatibility complex (MHC) molecules on infected cells, reducing their visibility to cytotoxic T cells.
3. Certain viruses may produce proteins that mimic host cytokines or other immune molecules, tricking the immune system into not recognizing them as threats.
4. Many viruses can induce apoptosis in immune cells, specifically targeting those that could eliminate them, thereby enhancing their survival.
5. Some pathogens utilize rapid mutation rates to frequently change their surface antigens, making it difficult for the immune system to keep up with recognition.

Review Questions

• How do antigenic variation and downregulation of MHC molecules contribute to viral immune evasion?
  • Antigenic variation allows viruses to alter their surface proteins, making it hard for the immune system to recognize them as previously encountered threats. Similarly, downregulation of MHC molecules on infected cells prevents cytotoxic T cells from identifying and killing those cells. Both strategies significantly enhance a virus's ability to evade detection and destruction by the host's immune response, enabling sustained infection.
• Discuss the role of interferons in innate immunity and how viruses can counteract their effects.
  • Interferons are critical proteins in innate immunity that alert neighboring cells to viral infections and activate various immune responses. They enhance antiviral defenses and promote the expression of MHC molecules. Viruses can counteract these effects by producing proteins that inhibit interferon signaling pathways or by blocking interferon production altogether. This undermines the innate immune response and allows the virus to replicate more effectively within the host.
• Evaluate how latency as an immune evasion strategy affects viral persistence and reactivation in a host.
  • Latency is a clever strategy employed by some viruses, allowing them to hide within host cells without triggering an immune response. By remaining dormant, these viruses evade detection and can reactivate during times of immunosuppression or stress, causing disease. This persistent presence poses challenges for treatment, as the virus is not actively replicating and is thus less susceptible to antiviral therapies that target active replication cycles.

Related terms

Antigenic variation: The process by which viruses change their surface proteins to evade recognition by the immune system.

Interferons: Proteins produced by host cells in response to viral infections that have antiviral effects and modulate the immune response.

Latency: A strategy used by some viruses to remain dormant within host cells and evade immune detection while still being able to reactivate later.