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. 2011 Oct;18(10):1728-36.
doi: 10.1128/CVI.05252-11. Epub 2011 Aug 18.

Establishment of a new human pneumococcal standard reference serum, 007sp

Affiliations

Establishment of a new human pneumococcal standard reference serum, 007sp

D Goldblatt et al. Clin Vaccine Immunol. 2011 Oct.

Abstract

Lot 89SF has been the reference standard serum pool used in pneumococcal enzyme-linked immunosorbent assays (ELISAs) since 1990. In 2005, it was estimated that there remained between 2 and 5 years' supply of lot 89SF. Since lot 89SF was the reference standard used in the evaluation of the seven-valent pneumococcal conjugate vaccine Prevnar (PCV7), the link to clinical efficacy would be severed if stocks became completely depleted. Furthermore, demonstration of immune responses comparable to those elicited by PCV7 is a licensure approach used for new pneumococcal conjugate vaccines, so a replacement reference standard was required. A total of 278 volunteers were immunized with the 23-valent unconjugated polysaccharide vaccine Pneumovax II, and a unit of blood was obtained twice within 120 days following immunization. Plasma was prepared, pooled, and confirmed to be free from hepatitis B virus (HBV), hepatitis C virus (HCV), and HIV. The pooled serum was poured at 6 ml per vial into 15,333 vials and lyophilized. Immunological bridging of 007sp to 89SF was used to establish equivalent reference values for 13 pneumococcal capsular serotypes (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F) by five independent laboratories. Antibody concentrations in 007sp were established relative to the lot 89SF reference preparation using the WHO reference ELISA. Subsequently, 12 existing WHO calibration sera had concentrations reassigned for 13 pneumococcal serotypes using new serum 007sp as the reference, and these were compared to concentrations relative to the original reference serum. Agreement was excellent for the 12 WHO calibration sera. The 007sp preparation has replaced 89SF as the pneumococcal reference standard. Sufficient quantity of this new preparation is available such that, with judicious use, it should be available for at least 25 years.

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Figures

Fig. 1.
Fig. 1.
Scatter plots showing the correlation of antibody concentrations between laboratories for the 13 serotypes in 007sp with the log concentration of the values represented on the x and y axes. Each point represents the mean of at least 40 log antibody concentrations for 007sp for each serotype from each laboratory. The concordance correlation coefficient (rc) is listed within each plot. The solid diagonal line indicates perfect agreement (where slope=1 and intercept=0).
Fig. 2.
Fig. 2.
Comparison of the original assigned values for 13 serotypes in 89SF with those assigned to 007sp.
Fig. 3.
Fig. 3.
Scatter plots showing the correlation among the derived concentrations for the panel of 12 calibration sera using 007sp (vertical scale) versus 89SF (horizontal scale) as reference standards for the first seven serotypes (1, 3, 4, 5, 6A, 6B, and 7F) analyzed (n=5 for each calibration serum from each laboratory). The plots illustrate a high degree of agreement and correlation among the derived concentrations.
Fig. 4.
Fig. 4.
Box plots illustrating the deviations of the 007sp estimates from those obtained using 89SF for the first seven serotypes (1, 3, 4, 5, 6A, 6B, and 7F) of the panel of 12 WHO calibration sera analyzed (n=5 for each calibration serum from each laboratory). In these plots, the box is defined by the 25th and 75th percentiles of the distribution, the horizontal line within the box represents the median or 50th percentile, and the asterisk signifies the mean. Vertical lines extend to the most extreme observation that is less than 1.5 times the interquartile range (75th to 25th percentiles), and diamonds and boxes correspond to individual assay values which are progressively distant from the mean. Data above the dotted horizontal line indicate 007sp estimates are greater than estimates using lot 89SF. On the vertical axis, the number 2 indicates a point where the 007sp estimate was twice the 0089SF estimate. A value of indicates the 89SF estimate was 4 times the 007sp estimate. Boxes centered on the horizontal dotted line indicate a good agreement between the 007sp and 89SF estimates.
Fig. 5.
Fig. 5.
Scatter plots showing the correlation among the calculated concentrations using 007sp (vertical scale) versus 89SF (horizontal scale) for the remaining six serotypes (9V, 14, 18C, 19A, 19F, and 23F) analyzed (n=5 for each calibration serum from each laboratory). The plots illustrate a high degree of agreement and correlation among the calculated concentrations.
Fig. 6.
Fig. 6.
Box plots illustrating the deviation of the 007sp estimates from those obtained using 89SF for the remaining six serotypes (9V, 14, 18C, 19A, 19F, and 23F) analyzed (n=5 for each calibration serum from each laboratory). In these plots, the box is defined by the 25th and 75th percentiles of the distribution, the horizontal line within the box represents the median or 50th percentile, and the asterisk signifies the mean. Vertical lines extend to the most extreme observation that is less than 1.5 times the interquartile range (75th to 25th percentiles), and diamonds and boxes correspond to individual assay values which are progressively distant from the mean. Data above the dotted horizontal line indicate 007sp estimates are greater than estimates using 89SF. On the vertical axis, the number 2 indicates a point where the 007sp estimate was twice the 89SF estimate. A value of indicates the 89SF estimate was four times the 007sp estimate. Boxes centered on the horizontal dotted line indicate good agreement between the 007sp and 89SF estimates.

References

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