During the last few months, many new variants of the SARS-CoV-2 virus have emerged. The U.K. variant B.1.1.7, the South Africa variant B.1.351, the Brazil variant P.1, and the most recent Indian variant B.1.617 are specifically concerning due to their high prevalence.
A subset of the mutations detected in the RBD domain of the spike protein takes place in more than one strain. Such convergent mutations are of major interest because they could be responsible for causing increased transmissibility. Sino Biological has now introduced RBD and Spike proteins of these variants.
Furthermore, the mutations in these strains take place in the nucleocapsid protein, which is generally utilized as the biomarker in rapid antigen tests. It is crucial to evaluate whether the present commercial antigen tests could identify the mutated N proteins with the same level of specificity and sensitivity as their WT counterpart.
A panel of recombinant RBD or Spike and nucleocapsid protein variants designed by Sino Biological can now be used to assess the efficacy of the vaccination and antibodies.
B.1.617 (India*)
Table 1. Source: Sino Biological Inc.
| Lineage |
Catalogue |
Antigen |
Mutations |
Tag |
| B.1.617 |
40588-V07E16 |
N |
D377Y |
His |
| B.1.617 |
40589-V08B13
(under development) |
S1+S2
ECD |
D614G, E154K, E484Q, G142D,
H1101D, L452R, P681R, Q1071H |
His |
| B.1.617 |
40591-V08H19 |
S1 |
D614G, E154K, E484Q, L452R,
P681R |
His |
| B.1.617 |
40592-V08H28 |
RBD |
L452R |
His |
B.1.617 /
B.1.617.1 /
B.1.617.3 |
40592-V08H88 |
RBD |
L452R，E484Q |
His |
Epsilon | B.1.427/B.1.429 (U.S.A*)
Table 2. Source: Sino Biological Inc.
| Lineage |
Catalogue |
Antigen |
Mutations |
Tag |
| B.1.429/B.1.427 |
40591-V08H17 |
S1 |
W152C, L452R, D614G |
His |
| B.1.429/B.1.427 |
40588-V07E9 |
N |
T205I |
His |
Alpha | B.1.1.7 (U.K.*)
Table 3. Source: Sino Biological Inc.
| Lineage |
Catalogue |
Antigen |
Mutations |
Tag |
| B.1.1.7 |
40588-V07E1 |
N |
R203K, G204R |
His |
| B.1.1.7 |
40588-V07E17 |
N |
E378Q |
His |
| B.1.1.7 |
40588-V07E4 |
N |
I292T |
His |
| B.1.1.7 |
40589-V08B6 |
S1+S2
ECD |
H69del, V70del, Y144del, N501Y, A570D, D614G, P681H, T716I, S982A, D1118H |
His |
| B.1.1.7 |
40592-V08H18 |
RBD |
S494P |
His |
Beta | B.1.351 (South Africa*)
Table 4. Source: Sino Biological Inc.
| Lineage |
Catalogue |
Antigen |
Mutations |
Tag |
| B.1.351 |
40588-V07E9 |
N |
T205I |
His |
| B.1.351 |
40589-V08B11 |
S1+S2
ECD |
D80A, L242del, A243del, L244del, R246I,
E484K, K417N, N501Y, D614G, A701V |
His |
| B.1.351 |
40589-V08B7 |
S1+S2
ECD |
L18F, D80A, D215G, LAL242-244 deletion,
R246I, K417N, E484K, N501Y, D614G, A701V |
His |
| B.1.351 |
40591-V08H10 |
S1 |
K417N, E484K, N501Y, D614G |
His |
| B.1.351 |
40592-V08H85 |
RBD |
K417N, E484K, N501Y |
His |
| B.1.351 |
40592-V31H2 |
RBD |
E484K |
rFc |
Gamma | P.1 (Brazil*)
Table 5. Source: Sino Biological Inc.
| Lineage |
Catalogue |
Antigen |
Mutations |
Tag |
| P.1 |
40588-V07E11 |
N |
P80R |
His |
| P.1 |
40589-V08B10 |
S1+S2 ECD |
L18F, T20N, P26S, D138Y, R190S, K417T, E484K, N501Y, D614G, H655Y, T1027I, V1176F |
His |
| P.1 |
40591-V08H5 |
S1 |
T20N, D614G |
His |
| P.1 |
40592-V08H86 |
RBD |
K417T, E484K, N501Y |
His |
| P.1 |
40592-V31H5 |
RBD |
K417T, E484K, N501Y |
rFc |
Neutralization efficacy assay against SARS-CoV-2 variants
A few of the aforementioned mutations could have enabled the virus to evade the neutralizing antibodies. To define these variants, a new panel of monoclonal antibodies has been recently introduced.
Such antibodies reveal the differential neutralizing activities against various variants verified by Competitive ELISA Assay. Most significantly, the B.1.351 and P.1 variants appear to be impervious to a subset of the antibodies.
Table 6. Source: Sino Biological Inc.
Neutralizing
Antibodies |
WT RBD |
Recombinant RBD |
Recombinant S1 |
| B.1.1.7 |
B.1.351 |
P.1 |
B.1.617 |
B.1.617 |
B.1.429 |
| 40150-D001 |
++ |
+ |
++ |
++ |
++ |
++ |
++ |
| 40150-D002 |
++ |
+ |
+ |
++ |
++ |
++ |
++ |
| 40591-MM43 |
++ |
++ |
++ |
++ |
++ |
++ |
++ |
| 40592-MM57 |
+ |
+ |
- |
- |
+ |
+ |
+ |
| 40592-R001 |
+++ |
+++ |
- |
- |
+++ |
+++ |
+++ |
| 40592-R118 |
+++ |
+++ |
- |
- |
+ |
+ |
+ |
| 40592-R117 |
+++ |
+++ |
- |
- |
+++ |
+++ |
+++ |
+: Neutralizing capacity
The aforementioned recombinant RBD:
- WT: 40592-V08B
- B.1.1.7 | U.K. variant: 40592-V08H82 (N501Y)
- B.1.351 | South Africa variant: 40592-V08H85 (K417N, E484K, N501Y)
- P.1 | Brazil variant: 40592-V08H86 (K417T, E484K, N501Y)
- B.1.617 | India variant: 40592-V08H88 (L452R, E484Q)
The aforementioned recombinant S1 :
- B.1.617 | India Variant: 40591-V08H19 (E154K, E484Q, L452R, D614G, P681R)
B.1.429 | California Variant: 40591-V08H17 (W152C, L452R, D614G)
40150-D001. Image Credit: Sino Biological Inc.
40592-MM57. Image Credit: Sino Biological Inc.