A 34-year-old man presents to the emergency department with sudden onset of high fever, headache, and neck stiffness. His medical history is significant for a splenectomy after a motor vehicle accident two years ago. On examination, he has a petechial rash over his trunk and extremities. Lumbar puncture reveals cloudy cerebrospinal fluid with an elevated neutrophil count, and Gram stain demonstrates Gram-negative diplococci. Blood and CSF cultures grow Neisseria meningitidis. Which of the following virulence factors of this organism best explains its ability to evade phagocytosis and cause overwhelming sepsis in this asplenic patient?