Which one of the following pathogens does not use antigenic variation as a major means of evading host defences?
The principle of antibody structure explains that immunoglobulin fold with antiparallel beta-sandwich provides antigen binding. Hence Top of Form Streptococcus pneumonia fits best because it demonstrates immune recognition architecture, as documented in authoritative sources on immunology.
Ref: Owen, Punt and Stranford, Kuby Immunology, 8th Edition, Chapter 4, Antibody Structure, covers immunoglobulin domains, beta-sheet organization and antigen binding detailing immune recognition.
