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Rapid Test Targets for COVID-19, Flu A/B and RSV continued.
RSV is recognized as one of the most common causes of childhood illness and can lead to serious illnesses such as bronchiolitis and pneumonia in infants and older adults. In fact, almost two out of every one hundred children younger than six months of age with an RSV infection are at risk for hospitalization 8 . Structurally, RSV virus consists of three main proteins and the fusion protein (which is responsible for fusion to the host membrane) is the current leading target for diagnostic assays and the majority of vaccines and immunotherapies under development. This is due to the protein’s unique aspects in that it is only one of only two antigens that induce an RSV-neutralizing antibody response, it has a high degree of sequence conservation among RSV strains (>90%) 9 and it is highly immunogenic. Meridian offers several antibody pairs targeting the fusion protein which do not cross-react with SARS-CoV-2 or influenza and are for rapid antigen testing solutions. While immunoassay multiplexing offers numerous efficiency advantages, it also introduces several technical challenges that make assay design more complicated. One of the biggest challenges is controlling for interference between the various antibodies and proteins in the assay. Sample dilution can help with limiting interference caused by proteins and other substances present in complex sample types. However, in order to remove potentially interfering particles including endogenous antibodies such as heterophilic antibodies (HA) (e.g. HAMA) and rheumatoid factor (RF), it is important to incorporate immunoassay blockers into the assay design. Double
mouse monoclonal assays such as those for rapid respiratory antigen tests, are specifically prone to HAMA and RF interference and require a specialized blocker to ensure the assay’s accuracy. Meridian manufactures multikilogram scales of passive blockers such as Mouse IgG and animal serums as well a proprietary active blocker, TRU Block ™ , which contains specific binders directed against all types of heterophilic interference including HAMA and RF. Once bound to the interfering antibodies, TRU Block ™ prevents further binding of HA to other assay components through steric hindrance. Active blockers can typically be used in lower concentrations than passive blocking reagents, which minimizes the reduction in assay signal commonly associated with passive blockers. Overall, immunoassay multiplexing calls for carefully chosen reagents that allow the antibodies to work together to produce an accurate, meaningful result. Interfering factors must be minimized to prevent a false positive or a false negative error.
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