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Clinical and Diagnostic Laboratory Immunology, July 1999, p. 581-586, Vol. 6, No. 4
Respiratory Diseases Branch, Division of
Bacterial and Mycotic Diseases, National Center for Infectious
Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia
30333,1 and Institute for Child
Health, London, United Kingdom2
Received 6 November 1998/Returned for modification 8 January
1999/Accepted 22 March 1999
Opsonophagocytosis is the primary mechanism for clearance of
pneumococci from the host, and the measurement of opsonophagocytic antibodies appears to correlate with vaccine-induced protection. We
developed a semiautomated flow cytometric opsonophagocytosis assay
using HL-60 granulocytes as effector cells and nonviable 5,6-carboxyfluorescein, succinimidyl ester-labeled Streptococcus pneumoniae (serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F) as
bacterial targets. The flow cytometric opsonophagocytosis assay was
highly reproducible (for 87% of repetitive assays the titers were
within 1 dilution of the median titer) and serotype specific, with
1071-412X/99/$04.00+0
A Flow Cytometric Opsonophagocytic Assay for Measurement of
Functional Antibodies Elicited after Vaccination with the 23-Valent
Pneumococcal Polysaccharide Vaccine
97% inhibition of opsonophagocytic titer by addition of homologous serotype-specific polysaccharide. In general, opsonophagocytic titers were not significantly inhibited by the presence of either heterologous pneumococcal polysaccharide or penicillin in the serum.
The flow cytometric assay could reproducibly measure functional antibody activity in prevaccination (n = 28) and
postvaccination (n = 36) serum specimens from healthy
adult volunteers vaccinated with the 23-valent pneumococcal
polysaccharide vaccine. When compared with a standardized manual viable
opsonophagocytic assay, a high correlation (r = 0.89;
P
0.01) was found between the two assays for the
seven serotypes tested. The flow cytometric assay is rapid (~4 h)
with high throughput (~50 serum samples per day per technician) and
provides a reproducible measurement of serotype-specific
functional antibodies, making it a highly suitable assay for the
evaluation of the immune responses elicited by
pneumococcal vaccines.
*
Corresponding author. Mailing address: Mailstop A-36,
Respiratory Diseases Branch, Immunology Section, Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers
for Disease Control and Prevention, Atlanta, GA 30333. Phone: (404)
639-2473. Fax: (404) 639-3115. E-mail: SXS8{at}CDC.GOV.
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