What Organism (Besides Trypanosoma Brucei) Is Noted for Its Antigenic

What organism (besides Trypanosoma brucei) is noted for its antigenic variation that leads to its ability to repeatedly reinfect the same person and cause disease and has led to difficulty in vaccine development? Estimates of number of different serotypes are well over 1 million.

A) Chlamydia trachomatis
B) Neisseria gonorrhoeae
C) Neisseria meningitidis
D) Streptococcus pneumoniae
E) Treponema pallidum