Multilaboratory Comparison of Pneumococcal Multiplex Immunoassays Used in Immunosurveillance of Streptococcus pneumoniae across Europe

Pneumococcal IgG Antibody Responses to 23vPPV in Healthy Controls Using an Automated ELISA

Measurement of pre- and post-pneumococcal antibody levels after immunization with the 23-valent capsular polysaccharide pneumococcal vaccine (23vPPV) is indicative of a T-independent antibody response. The World Health Organisation ELISA is considered gold standard yet is labor-intensive and technically difficult to perform. Interpretation criteria defining an adequate response to 23vPPV remain controversial. The diagnostic Immunology Laboratory at The Royal Children's Hospital, Melbourne (RCH), performs an in-house multi-serotype automated ELISA. The primary objective of this study was to verify RCH interpretation criteria for the laboratory's automated ELISA. Forty pneumococcal conjugate vaccine (PCV)-naïve healthy adults aged 18 to 25 years and 22 PCV-primed healthy children aged 2 to 5 years were immunized with 23vPPV. A serum sample was collected immediately prior and 28 to 42 (± 7) days post immunization. Samples were analyzed on the Tecan Freedom Evo 200 ELISA with adequate response defined as post-immunization antibody level of 1.3 µg/mL or fourfold rise from baseline in ≥ 10/15 serotypes in adult participants and ≥ 4/8 serotypes in pediatric participants. Thirty-nine (97.5%) adults and 22 (100%) children achieved an adequate response to 23vPPV. In PCV-naïve adults, serotypes contained within the conjugate vaccines were less immunogenic, with 12 (30%) adults not achieving an adequate antibody response when only PCV serotypes were used for interpretation. Our diagnostic laboratory has verified the interpretation criteria used for an automated multi-serotype pneumococcal ELISA method. Clinical Trial Registration: ANZCTR registration number ACTRN12618000822280.

Immune surveillance for vaccine-preventable diseases

INTRODUCTION

Immunesurveillance is an important tool to monitor the protection of the population against vaccine-preventable diseases, which is currently mostly based on the detection of specific serum antibodies. However, the landscape of immune surveillance is changing, driven by emerging and evolving pathogens, changes in the age distribution of the population and scientific understanding of protective immunity, necessitating a comprehensive review.

AREAS COVERED

To anticipate these changes, reliable and high-throughput detection of antibody levels is desired to enable screening in larger population settings. Antibody levels alone do not always equate with protection and may require additional functional testing of the antibodies or immune cell-based assays. In addition, the location (systemic or locally mucosal) of the infection and whether the antibodies are induced through infection or vaccination have implications for both immune protection and assessing immune status.

EXPERT COMMENTARY

In order to perform multicenter studies on many samples for multiple antigens, more validated reference materials and wider adoption of high-throughput techniques are needed. The field of serosurveillance will also benefit from better correlates of protection and understanding of (local) mechanisms of protection. Here we give an overview of the current state-of-the-art of serosurveillance and how the field could move forward.