Innovative epitope-based ELISA assay for detecting Group B Streptococcus carriage in pregnant women

Three epitopes of Streptococcus agalactiae, ⁴¹KAFGSPLITN⁵⁰ from molecular chaperone GroEL (PEP2), ⁹¹MIALDGTPNKG¹⁰¹ from enolase (PEP5), and ²⁸LTAAITTVLARRLP⁴¹ from EF-Tu (PEP11), were studied as ELISA components for immunodiagnostic detection of infection caused by Streptococcus agalactiae (Group B Streptococcus; GBS) and GBS carriage in pregnant women using IgG, IgM, and IgA antibodies. The current gold standard in GBS detection based on culturing is time-consuming and sometimes yields results that are difficult to interpret. Therefore, the aim of this study was to develop an alternative immunoassay based on strictly defined synthetic epitopes. The study included 143 serum samples divided into a study group (GBS+) and a control group (GBS-). The experiments showed that all peptides (single used and mixed) significantly distinguished between GBS+ and GBS- sera. The best individual candidates were PEP5 and PEP11, as they required lower peptide concentrations and demonstrated higher mean absorbance values measured for the GBS+ samples. In turn, epitopes mixing in all combinations significantly improved immunoreactivity. The results are very promising-and to our best knowledge, pioneering-as there is no similar test on the diagnostic market. We believe that our prototype may constitute a promising alternative to the classic diagnostic methods. KEY POINTS: • Three synthetic GBS epitopes (from GroEL, enolase, EF-Tu) enable accurate immunodiagnosis of infection. • PEP5 (91MIALDGTPNKG101) and PEP11 (28LTAAITTVLARRLP41) showed highest immunoreactivity with IgG, IgM, and IgA detection. • Combining epitopes significantly improves immunoreactivity and diagnostic potential.