Reagent Solutions for Molecular and Immunological SARS-CoV-2 Diagnostic Assays COVID-19

The key to fighting the COVID-19 pandemic is through diagnostic testing. By identifying infectious individuals, it is possible to trace the pathogen’s spread and stop the chain of transmission. Research labs are racing to develop innovative testing methods to overcome the bottlenecks which are creating challenges to conducting widespread testing.

Viral tests for COVID-19 that diagnose an acute infection rely on the detection SARS-CoV-2 nucleic acid or antigen using nasopharyngeal swabs. Assays that could use alternative sample types such as saliva or nasal swabs and could be collected by an individual, are highly sought after as they would be simpler and quicker to use as well as being safer for healthcare workers. Overall challenges such as shortages in the reagents required for RNA extraction have created bottlenecks and many labs are searching solutions that provide flexibility in the face of these shortages such as the development of extraction-free assays. Antigen detection assays should help expand COVID-19 testing capacity and more rapid, point-of-care assays are expected to be launched into the market to help quickly scale up the testing of millions of individuals.

Spike (S) protein

Soluble ACE-2

Anti-ACE-2 antibody

SARS Virus

Cell membrane

Transmembrane ACE-2


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Molecular Reagents Optimized RT-qPCR Mixes

Meridian’s portfolio of RT-qPCR master mixes have been designed to simplify the development of SARS-CoV-2 molecular assays and enable new features such as extraction-free amplification. Each master mix contains a hot-start polymerase, dNTPs, buffer and other components optimized for each particular application (e.g. lyophilization). Only primers and probes are required to complete the assay formula. SARS-CoV-2 requires an RNA extraction step which is time limiting step and can result in RNA being lost during the extraction process reducing the performance of the assay. However, extraction is typically required to remove inhibitors which would otherwise impact an assay’s sensitivity and accuracy. In order to address this challenge, Meridian has developed an Inhibitor-Tolerant RT-qPCR Mix capable of delivering sensitive multiplex detection, even in the presence of difficult inhibitors found in sputum, saliva and stool specimens. This new mix offers a novel alternative to nucleic acids extraction, saving both time and labor which are vitally important in viral screening assays that require rapid detection for infection control.

No need for RNA/DNA Extraction with Meridian’s Inhibitor-Tolerant Mix

Crude Lysate 4x

Crude Lysate

Master Mix



Primers Probes


5 min

Requires RNA/DNA Extraction

Primers Probes

Master Mix







Extracted DNA or RNA


20 - 60 min

Product Data

Inhibitor-Tolerant RT-qPCR Mix exhibits a high tolerance to PCR inhibitors from clinical samples

SPUTUM SPECIMENS Amplification profile of inactivated influenza virus spiked into samples containing 5% sputum or no sputum. The data illustrates that the performance of Inhibitor-Tolerant RT-qPCR Mix (MDX016) in the presence of 5% artificial sputum ( red ) is the same Fast One-Step RT-qPCR Mix (MDX032) with no sputum ( blue ). In contrast, the sensitivity and performance of Fast One-Step RT-qPCR Mix (MDX032) significantly decreases in the presence of 5% artificial sputum ( black ) compared to no sputum or compared to Inhibitor-Tolerant RT-qPCR Mix (MDX016) with sputum.

SALIVA SPECIMENS MDX016 ( red ) and MDX032 ( black ) amplification traces of Influenza A spike in presence of saliva swabs (COPAN ESwab 359C) at 10% (left) and 20% (right) final concentration. With earlier Ct (approx. 4 Ct) and higher fluorescence (approx. +50%), the results demonstrate the superiority of Inhibitor-Tolerant RT-qPCR Mix (MDX016) against a standard RT-qPCR Mix (MDX032) for the detection of viral RNA in presence of saliva swab resuspension in UTM.

10% Saliva

20% Saliva

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Product Selection Chart

Inhibitor-Tolerant Mixes Optimized for extraction- free assays from crude clinical specimens (sputum, saliva and stool)

Fast Mixes Ideal for multiplex assays on fast, automated high- throughput systems

Lyo-ready Mixes Pre-formulated with lyo-excipients for lyophilization into beads or cakes

Air-Dryable Mixes Ready-to-use mix

compatible with a range of air-drying protocols to produce an ambient temperature stable assay


MDX021 MDX023 MDX024 2x

MDX082 MDX092 MDX095 4x

MDX013 MDX016

MDX020 MDX032





Master Mix






Ambient- Temperature Assays



Multiplex Reactions

RNA/DNA Extraction-Free Protocols







RT-qPCR Extraction Control • Monitors assay inhibition

VLP RNA Extraction Control

• Closely mimics the test sample • Undergoes the same processing from lysis and extraction to detection • Compatible with lyophilization for creating freeze-dried mixes

• Suitable for use with inhibitor-rich samples

MDX068 (Red, Cy5) MDX069 (Orange, HEX) MDX071 (Custom)

MDX028 (Red, Quasar 670) MDX029 (Orange, Cal Fluor Orange)


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SARS-CoV-2 High Sensitivity Antibodies

Rapid antigen tests can provide a result in minutes and can be produced at a lower cost in large scales. However, the performance of a rapid antigen test is limited by the sensitivity of the antibodies used. Meridian’s monoclonal antibodies are highly sensitive for the detection of SARS-CoV-2 and they do not cross-react with seasonal coronavirus strains. They are ideal for developing reliable and sensitive rapid lateral flow antigen assays for the detection of active COVID-19 infections. For Rapid Antigen Detection Assays NUCLEOCAPSID ANTIBODIES

Highly sensitive antibody pairs currently used in commercial diagnostic kits worldwide Cat# 9548/9547 achieves an LOD of 0.25 TCID 50 /mL and detects variant strains Alpha B.1.1.7, Beta B.1.351, Gamma P.1/P.2 and Delta B.1.617.2 Manufactured in multigram quantities weekly No cross-reaction with other respiratory pathogens, e.g., MERS-Coronavirus, Human Coronavirus (NL63, 229E and OC43), Influenza A, Influenza B, Respiratory Syncytial Virus (RSV) (A and B), Streptococcus A, Mycoplasma, Human Adenovirus (Types 1, 3, 5, 7, 8, 11, 18, and 23), Human Parainfluenza Virus (Types 1, 2, 3 and 4), Human Rhinovirus (Types 1, 14 and 42) and Human Metapneumovirus

Capture Antibody:


MAb to SARS-CoV-2 NP

*pairs with both detection antibodies 9547 and 9549

Detection Antibody:


MAb to SARS-CoV-2 NP


MAb to SARS-CoV-2 NP

Cat# 9548/9547 detects variant strains Alpha B.1.1.7, Beta B.1.351, Gamma P.1/P.2 and Delta B.1.617.2


Capture Antibody:

For use in lateral flow antigen detection COVID-19 assays with a trimetric spike recombinant antigen as control (e.g: Cat# 9566) Designed to work on saliva samples (no lysis required) Novel antibody pair to the trimeric form of the Spike 1 surface glycoprotein, recognizes both the G614 and D614G strains Using a mixture of detection antibodies Cat# 9565 and #9551 in a 1:1 ratio creates a synergistic effect that increases assay sensitivity in ELISA Recognizes a linear epitope - binding is not conformation-dependent Sensitivity of approx. 300 pg/mL in ELISA Does not cross-react with SARS-CoV, HCoV-229E, HCoV-HKU1, HCoV-NL63 and HCoV-OC43


MAb to SARS-CoV-2 S1 (Trimeric)

Detection Antibody:


MAb to SARS-CoV-2 S1 (Trimeric)


MAb to SARS-CoV-2 S1 (Trimeric)

*9551 and 9565 can be used together in a 1:1 ratio to increase assay sensitivity in ELISA

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For Serology Antibody Assays SARS-CoV-2 Recombinant Antigens

Serologic tests are an important tool for monitoring the evolution of an outbreak. Specifically, IgG/IgM antibody tests are essential for identifying previously undiagnosed infections in the asymptomatic population. Meridian’s recombinant antigens are expressed in human mammalian cells and insect cells using proprietary expression and purification technologies. Expression in either human or insect cells provides for post-translational modifications such as glycosylation and phosphorylation which can offer significant performance advantages over E. coli expressed formats.

Wild-type SARS-CoV-2

Mutant SARS-CoV-2 Spike, S1 RBD

Trimeric Spike, S1 Protein (His-Tag) Represents amino acids 14 - 683 of SARS-CoV-2 plus the synthetic trimeric domain Spike Protein, S1 Subunit (His-Tag) Represents amino acids 14 - 683 of the SARS-CoV-2 S1 subunit Spike Protein, N-terminal Domain (NTD) S1 Subunit (His-Tag) Represents amino acids 16 - 305 of the SARS-CoV-2 N-terminal domain Spike Protein, S1 Subunit RBD (His-Tag) Represents amino acids 330 - 521 of the SARS-CoV-2 S1 subunit, RBD domain

N501Y mutant (His-Tag) Represents B.1.1.7 strain, (Alpha variant) a.a. 319 - 541 K417N, E484K and N501Y mutant (His-Tag) Represents B.1.351 strain, (Beta variant) a.a. 319 - 541 K417T, E484K and N501Y mutant (His-Tag) Represents P.1 strain, (Gamma variant) a.a. 319 - 541







L452R mutant (His-Tag) Represents Epsilon variant, a.a. 319 - 541



L452R and E484Q mutant (His-Tag) Represents B.1.167 strain (Kappa variant), a.a. 319-541



Nucleocapsid Protein (His-Tag)

Related products


Spike Protein, S1 Subunit RBD (His-Tag)


Human ACE2 Protein (Fc1 Tag)

All mutants work with MAb to SARS-CoV-2 Trimeric S1 (Cat#9550) as a control in neutralization assays.

Insect-cell Expressed |

HEK293 Expressed | RBD = Receptor Binding Domain

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