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Rapid Test Targets for COVID-19, Flu A/B and RSV
Rapid tests can be designed to target different analytes, but generally target viral antigens and antibodies (IgG or IgM). They can detect analytes in blood, urine, saliva or vaginal swabs, with sampling protocols (sample collection, buffers, incubation time) varying by disease, sample matrix and analyte.
SARS-CoV-2 The nucleocapsid (N protein) is the main protein targeted in SARS-CoV-2 for rapid antigen testing as it is also the most abundant protein present on the surface of the virus and can easily be detected at low viral loads. Meridian’s highly sensitive antibody pair to SARS-CoV-2 Nucleocapsid Protein (Catalog 9548 and 9547) is proven to detect all of the WHO Variants of Concern (Alpha B.1.1.7, Beta B.1.351, Gamma P.1/P.2, Delta B.1.617.2 and Omicron B.1.1.529) and is used in FDA and CE-marked commercial rapid antigen tests around the world. The antibodies detect a conserved region N protein and they do not exhibit any cross-reactivity to influenza A/B, RSV or seasonal coronavirus strains. Influenza A & B For influenza, immunoassay testing typically detects the main circulating seasonal strains of both influenza type A and B. Influenza viruses are RNA viruses that are prone to antigenic drift and reassortment, which enables new strains of the virus to emerge each year. Rapid assays for influenza typically detect the nucleoprotein (NP) which is one of the more conserved proteins in the influenza virus and subsequently less likely to undergo mutations that lead to antigenic drift (which in turn can cause the functional components of an assay to not recognize a current influenza strain) 7 . Meridian offers several high performing antibody pairs for both influenza A and B that are ideal for rapid diagnostic testing and that do not cross-react with RSV or SARS-CoV-2 antigens.
SARS-COV-2 virus structure
Influenza virus structure
Subtype/ lineage
Titer (TCID 50 /mL)
PCR ct value*
Antibody
Strains
H1N1pdm A/Mexico/4108/09
1.51x10 3
28.1002
RSV virus structure
MAb to Flu A (BN1069-BN1070)
H3N2
A/Brisbane/10/07
7.44x10 2
31.4854
Yamagata lineage
B/Florida/04/06
3.56x10 3
22.7323
MAb to Flu B (BN1224 - BN1223)
Victoria lineage
B/Malaysia/2506/04 9.08x10 2
24.1907
Figure. 8 Limit of detection of RDTs using Meridian antibodies. *PCR: cobas 6800/8000 SARS-Cov-2/Flu 384T detection kit.
Figure 7. Virus structures and their major immunogenic proteins
www.meridianbioscience.com/lifescience
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