A 38-year-old woman undergoes a splenectomy following a motor vehicle accident. Two weeks later, she presents with sudden-onset fever, chills, and hypotension. Blood cultures yield alpha-hemolytic, optochin-sensitive, Gram-positive diplococci. The severity of her bacteremia is largely attributable to the organism’s polysaccharide capsule. This capsule enhances virulence primarily by which of the following mechanisms?