Therefore, there is a need for developing and testing alternative potency assays. Importantly, the requirement of strain-specific reference antigen and anti-serum is a major limitation that might be a hindrance to a timed supply of the vaccine, as exemplified by the 2009 swine flu (H1N1) pandemic 9. Requirement of seasonal reference reagents further necessitates complex interactions among vaccine producers, surveillance laboratories, and regulatory agencies. As the only internationally accepted assay for potency and stability, SRID is labor-intensive, relatively insensitive, not amenable to automation, and therefore, time-consuming. The single radial immunodiffusion assay (SRID), based on the immunological reaction between antisera and test hemagglutinin (HA) antigen, has been used as a golden standard potency assay for seasonal vaccines since the 1970s 8. The WHO guidelines specify that the manufacturers determine the potency of the vaccines at the time of release 7. Furthermore, ‘universal’ vaccines that would provide protection against various drift or potential pandemic strains of viruses are being actively researched 4, 5, 6. In addition, the recombinant protein-based quadrivalent vaccine has also been licensed and distributed 3. Recently, a quadrivalent vaccine has been recommended to provide protection against two co-circulating lineages of IBV 2. The trivalent influenza vaccine containing two strains of influenza A virus (IAV) and one strain of influenza B virus (IBV) has been distributed since 1978 1. Since the first influenza vaccine was introduced in 1942 1, various types of vaccine formulations have been developed. This new assay could be extended to pandemic or pre-pandemic mock-up vaccines of H5 of group 1 and H7 virus of group 2, and novel HA stalk-based universal vaccines. The quantitative ELISA was validated for the potency assay of individual components of TIV- H1, H3, and IBV- with good correlation with the SRID method. The calibration curves were generated to assess the sensitivity, specificity, accuracy, and linear dynamic range. The group-specific ‘universal’ mAbs (uAbs) bound to various subtypes of HAs in the same group from recombinant hosts, embryonated eggs, and commercial vaccine lots. The consensus hemagglutinin (cHA) stalks for group 1 influenza A virus (IAV), group 2 IAV, and influenza B virus (IBV) were designed and produced in bacterial recombinant host in a soluble form, and monoclonal antibodies (mAbs) were generated. As an alternative to Single Radial Immunodiffusion (SRID), we report a new quantitative enzyme-linked immunosorbent assay (ELISA) for seasonal trivalent influenza vaccine (TIV). The assurance of vaccine potency is important for the timely release and distribution of influenza vaccines.
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