A look at human papillomavirus and Staphylococcus aureus vaccine studies by the numbers
As the majority of novel vaccines are now combination or multivalent, precise characterization of the individual components with minimal or no interference from other antigens is becoming increasingly challenging. Accurately characterizing the polyclonal response to vaccination is critical, particularly monitoring type-specific neutralizing antibodies that mediate protective immunity.
In contrast to running multiple singleplex tests, many vaccine developers have developed custom xMAP®-based immunoassays. Multiplex assays widely support epidemiologic studies and clinical trials investigating the efficacy, immunogenicity, and duration of investigational and on-market vaccines.
Multiplexed immunoassays supported the development of Merck’s Gardasil®, the original 4 and later 9 antigen human papillomavirus (HPV) vaccine, as well as Pfizer’s SA4Ag, a 4-antigen Staphylococcus aureus investigational vaccine which is currently being evaluated in phase 2b study.
Both vaccine programs used competitive assays, where type-specific phycoerythrin (PE)-labeled, neutralizing monoclonal antibodies (mAbs) compete with an individual’s serum antibodies for binding to conformationally sensitive, neutralizing epitopes on the virus-like particles (VLPs). The fluorescent signals from bound, type-specific mAbs-PE are inversely proportional to the patients’ neutralizing antibody titers.
The rationale for developing a multiplexed competitive immunoassay, rather than a capture assay, was that capture assays measures a combination of antibodies to both neutralizing and non-neutralizing epitopes. Other advantages of the competitive assay format are that the serum sample does not need to be diluted and the assay measures antibodies specific to antigen type-specific neutralizing epitopes. These factors enabled the assay to demonstrate seroconversion and to link seroconversion to protective immunity in response to vaccination.
Check out these infographics for a more in-depth look at the development of these two vaccines.
Resources
- Getting Started with xMAP® Technology [Video]
- Browse 1,200+ Partner Kits with xMAP® Kit Finder [Online Tool]
- xMAP® Cookbook to Design Your Own Assays [Download]
- View the latest xMAP® Insights Newsletter [Online & Download]
