Background information
SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) was first detected in December 2019 in Wuhan, China. Since that time the virus kept mutating, leading to new virus variants. The B.1.617.2 lineage, also known as Delta variant, is a SARS-CoV-2 subvariant that was first discovered in India in December 2020. In June 2021, first evidence was reported from Nepal that a B.1.617.2 lineage (Delta variant) with additional mutations appeared. The distinguishing feature of this new subvariant is a K417N substitution in the receptor binding domain of the spike protein. It was assigned to the AY.1 lineage, belongs to VOC Delta G/478K.V1 (B.1.617.2+AY.1+AY.2) and is also called “Delta plus”. The mutations of this variant affect also immune-relevant parts of structural SARS-CoV-2 proteins and the respective sequences are available in GISAID, a genome data base. The mutations listed below are taken from sequence EPI_ISL_2645281. The AY.1 lineage (Delta plus variant) has been found to evade a pre-existing antibody response and appears to be more infectious than other variants.
In total there are 13 mutations in the surface or spike glycoprotein (“S”) of the AY.1 lineage (Delta plus variant) compared to the Wuhan variant (reference genome GenBank MN908947.3): T19R, T95I, G142D, E156G, deletion 157, deletion 158, W258L, K417N, L452R, T478K, D614G, P681R and D950N.
The PepTivator
® SARS-CoV-2 Prot_S AY.1 Mutation Pool covers selectively the mutated regions. It consists of 44 peptides of 15 aa length. The PepTivator® SARS-CoV-2 Prot_S AY.1 Mutation Pool can be used to supplement PepTivators covering the sequence of the wild-type spike glycoprotein (“S”) in order to detect immune responses towards both variants, Wuhan (wild-type) variant and AY.1 lineage (Delta plus variant). PepTivator Peptide pools spanning the sequence of the spike glycoprotein (“S”) of the Wuhan (wild-type) variant are PepTivator SARS-CoV-2 Prot_S (predicted immunodominant sequence domains), Prot_S1 (N-terminal S1 domain), Prot_S+ (part of the C-terminal S2 domain) and Prot_S Complete (all functional domains).
The PepTivator SARS-CoV-2 Prot_S AY.1 WT Reference Pool consists of the 44 homologous peptides of the Wuhan sequence and covers the positions T19, T95, G142, E156, F157, R158, W258, K417, L452, T478, D614, P681 and D950 of the Wuhan variant (reference genome GenBank MN908947.3).
PepTivator SARS-CoV-2 Prot_S AY.1 WT Reference Pool serves as a control for the SARS-CoV-2 Prot_S AY.1 Mutation Pool. Comparison of the T cell immune response upon stimulation with mutation and reference pool can be used to analyze mutationspecific T cell responses.
