Evaluation of the opsonic requirements for phagocytosis of Streptococcus pneumoniae serotypes VII, XIV, and XIX by chemiluminescence assay

Abstract

A luminol-enhanced chemiluminescence assay was used to investigate opsonic requirements for phagocytosis of Streptococcus pneumoniae serotypes VII, XIV, and XIX. After opsonization with whole immune sera (with antibody and total complement pathway), heat-inactivated immune sera (with antibody alone), or magnesium, dichloride-ethylene glycol tetraacetic acid-chelated immune sera (with antibody and alternative complement pathway), live S. pneumoniae cells were incubated at 37°C with normal polymorphonuclear leukocytes while serial chemiluminescence measurements were recorded. The amount of chemiluminescence observed correlated closely with evidence of phagocytosis as observed by microscopy. Complement was required for efficient opsonization, since all three serotypes showed a slower rise and less integral chemiluminescence after opsonization with heat-inactivated serum as compared with whole serum. The alternative pathway provided opsonic activity equal to that of the total complement pathway for type XIX, but only intermediate activity for types VII and XIV. Type-specific antibody was also required for effective opsonization of all three serotypes since chemiluminescence was markedly reduced when bacteria were opsonized with antibody-depleted serum (serum absorbed with type-specific S. pneumoniae cells at 4°C). Thus, chemiluminescence proved to be an effective means of defining the requirement for both antibody and complement in the opsonization and phagocytosis of S. pneumoniae.