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. 2020 Jul:66:21-29.
doi: 10.1016/j.biologicals.2020.05.002. Epub 2020 Jun 20.

Evaluation of a standardised Vi poly-l-lysine ELISA for serology of Vi capsular polysaccharide antibodies

Peter Rigsby  1 , Emma Beamish  2 , Jason Hockley  1 , Eleanor Atkinson  1 , Krisztina Hitri  2 , Elizabeth Jones  3 , Jae Seung Yang  4 , Firdausi Qadri  5 , Novilia S Bachtiar  6 , Sean C Elias  7 , Akshay Goel  8 , Ravipratapnarayan Mishra  8 , Raju Dugyala  9 , Marcela F Pasetti  10 , James E Meiring  11 , Maurice Mbewe  12 , Melita A Gordon  12 , Andrew J Pollard  3 , Alastair Logan  2 , Sjoerd Rijpkema  13 ; anti-Vi IgG working group
Affiliations

Evaluation of a standardised Vi poly-l-lysine ELISA for serology of Vi capsular polysaccharide antibodies

Peter Rigsby et al. Biologicals. 2020 Jul.

Abstract

Typhoid vaccines based on protein-conjugated capsular Vi polysaccharide (TCVs) prevent typhoid in infants and young children. Analysis of the serum anti-Vi IgG response following immunisation against typhoid confirms the immunogenicity of TCVs and forms an important part of the pathway to licensing. Comparative studies could expedite the licencing process, and the availability of a standardised ELISA method alongside the 1st International Standard (IS) 16/138 for anti-typhoid capsular Vi polysaccharide IgG (human) will facilitate this process. To this end, a non-commercial ELISA based on a coat of Vi and poly-l-lysine (Vi-PLL ELISA) was evaluated by 10 laboratories. Eight serum samples, including IS 16/138, were tested in the standardised Vi-PLL ELISA (n = 10), a commercial Vi ELISA (n = 3) and a biotinylated Vi ELISA (n = 1). Valid estimates of potencies relative to IS 16/138 were obtained for all samples in the Vi-PLL ELISA and the commercial ELISA, with good repeatability and reproducibility evident from the study results and concordant estimates obtained by the two ELISA methods. The study demonstrates that the Vi-PLL ELISA can be used in clinical trial studies to determine the immunogenicity of TCVs.

Keywords: ELISA; IgG; Poly-l-lysine; Polysaccharide; Typhoid; Vi.

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Figures

Fig. 1
Fig. 1
Example of data reported for single Vi-PLL ELISA plate.
Fig. 2
Fig. 2
Overview of slope ratios of samples 10/126 and G-M relative to IS 16/138 when tested in the Vi-PLL ELISA and Vacczyme ELISA. Sample H is a coded duplicate of 16/138.
Fig. 3
Fig. 3
Geometric mean potency estimates for study samples relative to IS 16/138 in IU mL−1 for the VaccZyme ELISA performed by laboratories 1 and 6, the Vi poly-l-lysine ELISA (Vi-PLL) performed by laboratories 1, 3, 5, 6, 8, 9 and 10, and biotinylated-Vi ELISA performed by laboratory 6.
Fig. 4
Fig. 4
a Comparison of overall geometric mean potency estimates in IU mL−1 relative to IS 16/138 by the Vi poly-l-lysine ELISA performed by laboratories 1, 3, 5, 6, 8, 9 and 10 and the VaccZyme ELISA performed by laboratories 1 and 6. 4b: Comparison of overall geometric mean potency estimates in IU mL−1 relative to IS 16/138 by the Vi poly-l-lysine ELISA performed by laboratories 1, 3 and 8 and the VaccZyme ELISA performed by laboratories 1 and 6.
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