Developing a novel multiplex assay using Luminex xMAP technology

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The identification of serotype-independent cellular and humoral correlates of protection against pneumococcal infection will accelerate development of vaccines with broad protection. The Experimental Human Pneumococcal Challenge (EHPC) model biobank of samples and a large library of purified pneumococcal proteins were used to develop a multiplex assay to measure systemic humoral protein-specific responses against pneumococcus (Spn). A multiplex Luminex xMAP assay was developed and optimised. Serum samples from EHPC volunteers intranasally inoculated with Spn6B and Spn15B were used for assay validation and humoral response to 74 pneumococcal protein antigens in volunteers experimentally challenged with the bacteria was measured. Median fluorescence intensity values were used to report anti-protein IgG levels. Volunteers susceptible to experimental colonisation with Spn6B elicited increased antibody levels to various antigens 29 days post-challenge compared to pre-challenge. This trend was not detected in volunteers who were protected against colonisation. Minimal difference was identified between susceptible and protected cohorts at baseline. Humoral response following experimental colonisation with Spn15B was reduced in comparison to response induced by Spn6B, suggesting limited immunogenicity of Spn15B. A novel multiplex assay has thus been developed allowing rapid, cost-effective determination of protein-specific antibody responses to a large library of pneumococcal vaccine candidates.