Viruses primarily avoid detection by evading the host's immune system, particularly the systems designed to spot foreign genetic material.
Viruses, along with some intracellular bacteria and protozoa, must evade detection by nucleic acid sensors within the host cells. These sensors are part of the innate immune system, designed to recognize the genetic material (DNA or RNA) that is foreign to the host, signaling an infection.
To bypass these defenses, viruses employ sophisticated immune evasion strategies. These strategies target the host's ability to recognize and respond to the viral presence.
Key Strategies for Immune Evasion
Viruses use several methods to prevent the detection of their nucleic acids and disrupt the host's immune response:
- Sequestration of Nucleic Acids: Viruses can hide their genetic material within protective compartments or structures inside the host cell. This prevents the viral DNA or RNA from being exposed to and recognized by the host's nucleic acid sensors.
- Modification of Nucleic Acids: Viruses can chemically alter their DNA or RNA. These modifications can make the viral genetic material look more like host nucleic acids, effectively camouflaging it from the immune sensors that are looking for specific foreign signatures.
- Inhibition or Degradation of Host Factors: Viruses can produce proteins that interfere with or destroy host factors involved in innate immune signaling. This includes proteins that block the sensors themselves or disrupt the downstream pathways that are activated upon detection, thus preventing the immune system from mounting a response.
These combined approaches allow viruses to replicate and spread within a host without being immediately recognized and eliminated by the immune system.
