Host immune evasion

Definition

Host immune evasion refers to the strategies and mechanisms that viruses employ to avoid detection and destruction by the host's immune system. By circumventing immune responses, viruses can replicate and spread within the host, leading to persistent infections and increased virulence. Understanding these evasion tactics is crucial for comprehending how viruses cause disease and damage to cells.

5 Must Know Facts For Your Next Test

1. Viruses can produce proteins that inhibit key components of the host immune response, such as interferons, which are crucial for antiviral defense.
2. Some viruses disguise themselves by mimicking host molecules, making it difficult for the immune system to identify them as foreign invaders.
3. Infection with certain viruses can lead to downregulation of major histocompatibility complex (MHC) molecules on infected cells, reducing visibility to cytotoxic T cells.
4. Viruses may also induce apoptosis in immune cells or manipulate their signaling pathways to create an immunosuppressive environment.
5. Chronic viral infections often utilize immune evasion strategies to persist in the host for long periods, sometimes leading to long-term cellular damage.

Review Questions

• How do viruses use antigenic variation as a strategy for immune evasion?
  • Viruses utilize antigenic variation by changing their surface proteins, which are recognized by the host's immune system. This constant alteration helps them evade detection and allows for reinfection of hosts that have previously been exposed. As a result, even if the immune system has generated antibodies against one version of the virus, these changes can render those antibodies ineffective against new variants.
• What are some mechanisms through which viruses can downregulate MHC molecules on infected cells, and why is this significant?
  • Viruses can downregulate MHC molecules through various mechanisms, such as encoding proteins that interfere with their expression or transport to the cell surface. This downregulation is significant because it prevents cytotoxic T cells from recognizing and eliminating infected cells, allowing the virus to persist and replicate undetected. This tactic highlights how viruses can exploit cellular processes to enhance their survival and pathogenesis.
• Evaluate the role of latency in viral infections and its implications for host immune evasion.
  • Latency plays a critical role in viral infections by allowing viruses to remain dormant within host cells, effectively evading the immune system. During this dormant phase, the virus does not produce proteins that could trigger an immune response, thus avoiding detection. When conditions are favorable for reactivation, the virus can emerge and replicate again. This ability to switch between latency and active infection complicates treatment strategies and poses challenges in managing chronic viral diseases.

Related terms

Antigenic variation: The process by which viruses alter their surface proteins to escape recognition by the host's immune system.

Immunosuppression: A reduction in the efficacy of the immune system, which can be caused by viral infections that inhibit immune responses.

Latency:

A state in which a virus remains dormant within a host cell, evading the immune system while being capable of reactivation.