A 3-year-old boy who has not received routine immunizations presents to the emergency department with high fever, drooling, and inspiratory stridor. A lateral neck radiograph shows a “thumbprint” sign consistent with epiglottitis. Blood cultures grow small, pleomorphic, gram-negative coccobacilli that grow on chocolate agar supplemented with factors X and V. Further testing confirms a type b strain expressing a polyribosylribitol phosphate (PRP) capsule. Which of the following describes the primary mechanism by which this capsule enhances the organism’s virulence?