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Clinical and Diagnostic Laboratory Immunology, August 2005, p. 970-976, Vol. 12, No. 8
1071-412X/05/$08.00+0     doi:10.1128/CDLI.12.8.970-976.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Interlaboratory Standardization of the Measurement of Serum Bactericidal Activity by Using Human Complement against Meningococcal Serogroup B, Strain 44/76-SL, before and after Vaccination with the Norwegian MenBvac Outer Membrane Vesicle Vaccine

Meningococcal Reference Unit, HPA North West Laboratory, PO Box 209, Clinical Sciences Building, Manchester Royal Infirmary, Manchester M13 9WZ, United Kingdom,¹ Division of Infectious Disease Control, Norwegian Institute of Public Health, NO-0403 Oslo, Norway,² Chiron Vaccines, 4560 Horton Street, Emeryville, California 94608-2916,³ Chiron Biostatistics, 4560 Horton Street, Emeryville, California 94608-2916,⁴ Chiron Vaccines, Via Fiorentina 1, 53100 Siena, Italy,⁵ Institute of Environmental Science & Research Ltd., Kenepuru Science Centre, Porirua, New Zealand⁶

Received 25 April 2005/ Returned for modification 13 May 2005/ Accepted 24 May 2005

There is currently no standardized serum bactericidal antibody (SBA) assay for evaluating immune responses to meningococcal outer membrane vesicle or protein vaccines. Four laboratories, Manchester Health Protection Agency (MC HPA), New Zealand Institute of Environmental Science and Research Limited (NZ ESR), Norwegian Institute of Public Health (NIPH), and Chiron Vaccines (Chiron), measured SBA titers in the same panel of human sera (n = 76) from laboratory staff (n = 21) vaccinated with MenBvac. Blood samples were collected prevaccination, prior to each of the three doses of MenBvac given at 6-week intervals, and 6 weeks following the third dose. Initial results showed a number of discrepancies in results between the four participating laboratories. The greatest effect on titers appeared to be due to differences among laboratories in the maintenance of the meningococcal serogroup B test strain, 44/76-SL. A repeat study was conducted using the same frozen isolate (meningococcal serogroup B test strain 44/76-SL), freshly distributed to all four laboratories. Using SBA titers from the tilt method for all samples, and using MC HPA as the comparator, the results were as follows for NZ ESR, NIPH, and Chiron, respectively, using log₁₀ titers: correlation coefficients (r) were 0.966, 0.967, and 0.936; intercepts were 0.08, 0.15, and 0.17; and slopes were 0.930, 0.851, and 0.891. In both prevaccination and postvaccination samples from 15 subjects assayed by all four laboratories, similar increases in SBA (fourfold or greater) were observed (for 11, 11, 9, and 9 subjects for MC HPA, NZ ESR, NIPH, and Chiron, respectively), and similar percentages of subjects with SBA titers of 4 prevaccination and 6 weeks following each dose were found. The SBA assay has been harmonized between the four different laboratories with good agreement on seroconversion rates, n-fold changes in titers, and percentages of subjects with SBA titers of 4.