Niche and Neutral Effects of Acquired Immunity Permit Coexistence of Pneumococcal Serotypes

Abstract

Diversity in Immune Adversity Streptococcus pneumoniae commonly colonizes the nasopharynx and has the potential to cause life-threatening infections. Many variants of this pathogen are recognized that have subtly different capsule (an external polysaccharide coat) structures, which prompt distinct immune responses from the host and allow classification of this pathogen into serotypes. A consistent pattern of multiple coexisting serotypes occurs in human populations. Cobey and Lipsitch (p. 1376 , published online 1 March) probed the mechanisms behind serotype coexistence by developing an ecological model and feeding it data from nasopharyngeal carriage studies.