Re-validation and update of an extended-specificity multiplex assay for detection of Streptococcus pneumoniae capsular serotype/serogroup-specific antigen and cell-wall polysaccharide in urine specimens

Seyi D Eletu; Carmen L Sheppard; Samuel Rose; Kenneth Smith; Nick Andrews; Wei Shen Lim; David J Litt; Norman K Fry

doi:10.1099/acmi.0.000094

Re-validation and update of an extended-specificity multiplex assay for detection of Streptococcus pneumoniae capsular serotype/serogroup-specific antigen and cell-wall polysaccharide in urine specimens

Access Microbiol. 2020 Jan 28;2(3):acmi000094. doi: 10.1099/acmi.0.000094. eCollection 2020.

Authors

Seyi D Eletu¹, Carmen L Sheppard¹, Samuel Rose¹, Kenneth Smith², Nick Andrews³, Wei Shen Lim⁴, David J Litt¹, Norman K Fry^{1

5}

Affiliations

¹ Vaccine Preventable Bacteria Section, Public Health England - National Infection Service, Colindale Avenue, London, NW9 5EQ, UK.
² Oklahoma Medical Research Foundation, 825 NE 13th Street, Oklahoma City, OK 73104, USA.
³ Statistics, Modelling and Economics Department, Public Health England - National Infection Service, Colindale Avenue, London, NW9 5EQ, UK.
⁴ Department of Respiratory Medicine, Nottingham University Hospitals NHS Trust, Nottingham, UK.
⁵ Immunisation and Countermeasures Division, Public Health England - National Infection Service, Colindale Avenue, London, NW9 5EQ, UK.

Abstract

National surveillance of pneumococcal disease at the serotype level is essential to assess the effectiveness of vaccination programmes. We previously developed a highly sensitive extended-specificity multiplex immunoassay for detection of Streptococcus pneumoniae serotype-specific antigen in urine in the absence of isolates. The assay uses human mAbs that detect the 24 pneumococcal serotype/groups targeted by the pneumococcal conjugate vaccines (PCVs) and pneumococcal polysaccharide vaccine (PPV-23) plus some cross-reactive types and the pneumococcal cell-wall polysaccharide. However, the previous assay had some limitations, namely the reduced specificity of the serotype 7F, 20 and 22F assays, for which non-specific binding in urine samples was observed. Here we report on the further development and re-validation of a new version of the assay (version 2.1), which offers improved sensitivity towards serotypes 7F, 18C and 19F and increased specificity for serotypes 7F, 20 and 22F by replacement of some of the antibody clones with new clones. Using a panel of urine specimens from patients diagnosed with community-acquired pneumonia or pneumococcal disease, the overall clinical sensitivity of this version of the assay based on isolation of S. pneumoniae from a normally sterile site is 94.3 % and the clinical specificity is 93.6 %, in comparison with clinical sensitivity and specificity values of 96.2 % and 89.9 % in the previous assay.

Keywords: Streptococcus pneumoniae; diagnostics; monoclonal antibodies; pneumococcus; surveillance studies.