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

Biologicals : journal of the International Association of Biological Standardization (2020-06-24)
Peter Rigsby, Emma Beamish, Jason Hockley, Eleanor Atkinson, Krisztina Hitri, Elizabeth Jones, Jae Seung Yang, Firdausi Qadri, Novilia S Bachtiar, Sean C Elias, Akshay Goel, Ravipratapnarayan Mishra, Raju Dugyala, Marcela F Pasetti, James E Meiring, Maurice Mbewe, Melita A Gordon, Andrew J Pollard, Alastair Logan, Sjoerd Rijpkema
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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Poly-L-lysine hydrobromide, mol wt 150,000-300,000
Sigma-Aldrich
Streptavidin from Streptomyces avidinii, essentially salt-free, lyophilized powder, ≥13 units/mg protein