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New Product | “Mu” Variant of COVID-19 Classified as VOI

The World Health Organization (WHO) designates SARS-CoV-2 variants as Variant of Concern (VOC) or Variant of Interest (VOI) based on their transmissibility and virulence. The former means the variant can decrease the effectiveness of public health measures, vaccines or therapeutics; the latter means the variant has genetic changes that can affect transmissibility, disease severity and immune escape.

In its weekly pandemic bulletin on September 1st, WHO designated “Mu”(B.1.621), first identified in Colombia, as a variant of interest. As the variant may be highly resistant to vaccines and may evade the immunity people have developed from past infection or vaccination, it will receive further monitoring from WHO.

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Figure 1. Five Variants Designated as VOI by WHO

The “Mu” variant has the P681H mutation (first reported in the Alpha variant), which is associated with increased transmissibility. E484K and K417N mutations are seen in the Beta variant, which are considered to be linked to immune escape. In addition, several other mutations, including R346K and Y144T, are seen in the “Mu” variant, but no studies have reported the biological significance of these mutations. The “Mu” variant ranks second only to the Delta variant in terms of immune escape / breakthrough infection, and it has been reported that the serum of patients recovered from the Delta variant does not show strong neutralizing effect with the “Mu” variant. This may be one of the reasons for the rapid increase in the prevalence of the “Mu” variant, but more research is needed to further understand its clinical characteristics.

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Table 1. Frequency Ranking of Spike Protein Mutations of VOC/VOI

(The table comes from CoVariants.org, click for more details)

For virus mutant research, Vazyme has been working against the clock for a series of new mutant pseudoviruses (see the table below for details). In addition, we provide a library of more than 50 wild-type and pseudovirus mutants to assist researchers in quickly obtaining neutralizing antibodies against mutant strains and evaluating the clinical efficacy of vaccines.

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Table 2. Mutation Information of Vazyme’s “Mu” Variant

Vazyme’s Solutions for SARS-CoV-2 Neutralizing Activity Assay
Pseudoviruses: expressing wild-type and mutant Spike proteins of SARS-CoV-2 (see Ordering Information for available mutants).
Cell Line: HEK293-ACE2 stable cell line.
Assay procedure: Use serum-free cell culture medium to dilute the samples to be tested in a 3-fold concentration gradient, and incubate 60 μl of each sample with an equal volume of pseudovirus at 37 ℃ for 1 h; add the sample-virus incubation solution to the ACE2-expressing cell line and incubate at 37 ℃ for 20-24 h; change the cell culture medium and continue to incubate at 37 ℃ for 24 h and add Bio-liteTM Luciferase Assay System (DD1201, Vazyme) to detect the luminescence intensity. Then plot a fitted curve with Graphpad Prism, and calculate the IC50.
Deliverables: Project report, 8 concentration points and 3 replicate wells per sample to be tested.
Sample requirements: >100 μg antibody or 100 μl inactivated serum.
Service period: 2-3 weeks after the program is determined.

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New Product  “Mu” Variant of COVID-19 Classified as VOI
Citation: Emma B.Hodcroft. 2021."CoVariants: SARS-CoV-2 Mutations and Variants of Interest." https://covariants.org/