Quality control of Hemophilus Influenzae type b (Hib) conjugate vaccines is mainly dependent on physicochemical methods. Overcoming sample matrix interference when using physicochemical tests is very challenging, these tests are therefore only used to test purified samples of polysaccharide, protein, bulk conjugate, and final product. For successful development of a Hib conjugate vaccine, several ELISA (enzyme-linked immunosorbent assay) methods were needed as an additional tool to enable testing of in process (IP) samples. In this paper, three of the ELISA's that have been very valuable during the process development, implementation and scaling up are highlighted. The PRP-ELISA, was a very efficient tool in testing in process (IP) samples generated during the development of the cultivation and purification process of the Hib-polysaccharide. The antigenicity ELISA, was used to confirm the covalent linkage of PRP and TTd in the conjugate. The anti-PRP IgG ELISA was developed as part of the immunogenicity test, used to demonstrate the ability of the Hib conjugate vaccine to elicit a T-cell dependent immune response in mice. ELISA methods are relatively cheap and easy to implement and therefore very useful during the development of polysaccharide conjugate vaccines.
Keywords: ADH, adipic acid dihydrazide; BSA, bovine serum albumin; ELISA; ELISA, enzyme-linked immuno sorbent assay; EP, European Pharmacopeia; HPSEC, high performance size exclusion chromatography; Haemophilus Influenzae type b vaccine; Hib, Haemophilus Influenzae type b; IPC, in process control; IgG, immunoglobulin G; Intravacc, Institute for Translational Vaccinology; Mn, number-average molecular weight; Mr, molecular weight; Mw, weight-average molecular weight; NIBSC, National Institute for Biological Standards and Control (UK); NIH, National Institutes of Health; NMR, nuclear magnetic resonance; NVI, Netherlands Vaccine Institute; PBS, phosphate buffered saline; PRP; PRP, poly-ribosylribitol phosphate (Hib capsular polysaccharide); PRP-T, Hib vaccine (PRP conjugated to tetanus toxoid); QC, quality control; RI, refractive index; RIVM, The National Institute for Public Health and the Environment (Rijksinstituut voor Volksgezondheid en Milieu); TMB, tetramethyl benzidine; TTd, tetanus toxoid; UV, ultraviolet; WHO, World Health Organization; antigenicity; characterization; conjugate; cultivation; immunogenicity; kDa, kilo dalton; polysaccharide; purification; tR, retention time.