Viruses can escape immune defenses by

• A. undergoing frequent genetic mutations.
• B. suppressing the immune system.
• C. integrating their nucleic acid into the host genome.
• D. all of the above.

Answer: (D)

Viruses can slip past immune defenses through several different tricks, and often more than one at a time. One major tactic is frequent genetic mutations that alter viral surface proteins. Antibodies and T cells recognize specific shapes on the virus; if those shapes change, previously effective antibodies may no longer bind well, allowing the virus to infect cells despite prior immunity or vaccination.

Another approach is active suppression of the immune response. Some viruses produce proteins that blunt interferon signaling, reduce the presentation of viral peptides on MHC molecules, or modulate cytokine environments. This makes antiviral responses slower or weaker, giving the virus a head start to replicate and spread.

A third mechanism involves integrating their nucleic acid into the host genome, creating latent reservoirs where little or no viral protein is made. In latency, infected cells aren’t readily detected by the immune system, and serologic tests may fail to reveal ongoing infection if antigen production is minimal.

Because viruses use these distinct strategies—mutating to evade antibodies, suppressing immune signaling, and establishing latency through integration—multiple avenues of escape exist. That’s why all of these mechanisms collectively describe how viruses evade immune defenses.