Validation of a multiplexed opsonophagocytic assay for 11 additional pneumococcal serotypes and its application to functional antibody evaluation induced by pneumococcal polysaccharide vaccine

Jihei Cha, Han Wool Kim, Ji Hyen Lee, Soyoung Lee, Kyung Hyo Kim

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Abstract

Background: Various pneumococcal vaccines have been evaluated for immunogenicity by opsonophagocytic assay (OPA). A multiplexed OPA (MOPA) for 13 pneumococcal serotypes was developed by Nahm and Burton, and expanded to 26 serotypes in 2012. The development of new conjugate vaccines with increased valence has necessitated expanded MOPAs to include these additional serotypes. In this study, we validated this expanded MOPA platform and applied to measure antibodies against 11 additional serotypes (2, 8, 9N, 10A, 11A, 12F, 15B, 17F, 20B, 22F, and 33F) in human sera. Methods: All materials, including serum, complement, bacterial master stocks, and HL-60 cells, were evaluated for assay optimization. Following optimization, the assay was validated for accuracy, specificity, and intra- and inter-assay precision with sera from adult donors following standard protocols. The assay was applied to evaluate functional antibodies of 42 sera immunized with 23-valent pneumococcal polysaccharide vaccine (PPV23). Results: The expanded MOPA platform was specific for all serotypes, with the exception of serotype 20. The assay results were highly correlated with those obtained from single-serotype OPA, indicating acceptable accuracy. The coefficients of variation were 7%-24% and 13%-39% in tests of intra- and inter-assay precision, respectively, using three quality-control samples. A MOPA that included 11 additional serotypes in the PPV23 was established and validated with respect to accuracy, specificity, and precision. The opsonic indices of immune sera were obtained using this validated assay. Conclusion: The expanded MOPA will be useful for evaluation of the immunogenicity of PPV23 and future conjugate vaccine formulations.

Original languageEnglish
Article numbere340
JournalJournal of Korean Medical Science
Volume33
Issue number51
DOIs
StatePublished - 2018

Bibliographical note

Funding Information:
This study was supported by a grant from the Ministry of Food and Drug Safety (15172MFDS164 and 16172MFDS270). Jihei We are grateful to Moon H. Nahm and Robert L. Burton at the University of Alabama at Birmingham (UAB) for their careful reading of the manuscript and valuable advice for the establishment of MOPA with an additional 11 serotypes at the Ewha Center for Vaccine Evaluation and Study (ECVES). We also thank Moon H. Nahm for providing the target pneumococcal strains used in this study. UAB owns intellectual property rights on the reagents used for the MOPA studies. We also would like to thank Soo Young Lim and Je Eun Cha at ECVES for laboratory support.

Publisher Copyright:
© 2018 The Korean Academy of Medical Sciences.

Keywords

  • Biologic assay
  • Immunogenicity
  • Opsonin proteins
  • Pneumococcal vaccines
  • Validation studies

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