Viruses can escape immune defenses by which mechanisms?

• 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 escape immune defenses by several different strategies, and these can act together to make immune clearance difficult. First, they can undergo frequent genetic mutations, especially RNA viruses, which leads to changes in surface proteins that antibodies target. This antigenic variation means antibodies trained on an earlier form may no longer recognize the newer variants, allowing the virus to slip past humoral immunity. Second, they can actively suppress the immune response by interfering with how immune cells communicate and present viral pieces to T cells, or by infecting immune cells themselves. This dampens both innate and adaptive defenses, reducing the overall ability to control infection. Third, some viruses integrate their genetic material into the host genome, entering a latent state with little or no viral protein production, which helps them hide from immune surveillance and later reactivate. Because each mechanism is a credible way for viruses to evade immunity, the best choice is all of the above.