COVID-19関連追加(2021630-2mRNAワクチンについてその20

mRNAワクチンによる胚中心反応)

SARS-CoV-2 mRNAワクチンは持続的なヒト胚中心反応を引き起こす】

Turner, J.S., O’Halloran, J.A., Kalaidina, E. et al. SARS-CoV-2 mRNA vaccines induce persistent human germinal centre responses. Nature (2021).

https://doi.org/10.1038/s41586-021-03738-2.

Abstract

SARS-CoV-2 mRNAワクチンは,COVID-19の予防に約95%の効果がある.しかし,これらのワクチンによって誘導される,ヒトにおける,抗体を分泌するプラズマブラスト(PB: plasmablasts胚中心(GC: germinal centreB細胞の動態は明らかではない.我々は,SARS-CoV-2スパイク(S)遺伝子を完全にエンコードしたmRNAワクチンであるBNT162b22回接種した14人の末梢血(n= 41)および流入領域リンパ節(DLNs: draining lymph nodes)における抗原特異的B細胞反応を調べたSタンパク質を標的としたIgGおよびIgAを分泌する血中PBsは,2回目接種から1週間後にピークに達した後,減少し,3週間後には検出されなくなった.これらのPB反応は,初期に流通していたSARS-CoV-2株および新たに出現した変異株に対する血清抗S結合抗体および中和抗体の最大レベルに先行して現れ,特にSARS-CoV-2感染歴がある人では,最も強固な血清反応が得られた.腋窩リンパ節の細針吸引(FNAs: fine needle aspirates)を調べたところ,プライム免疫後に採取したすべての被験者において,Sタンパク質と結合するGC B細胞を同定した.驚くべきことに,Sタンパク質に結合するGC B細胞とPBの高い頻度は,ブースター免疫後の少なくとも12週間,これらの流入領域リンパ節で維持されたS結合GC B細胞由来のモノクローナル抗体は,主にSタンパク質の受容体結合ドメイン(RBD)を標的としており,N末端ドメイン(NTD)や,ヒトベータコロナウイルスOC43およびHKU1Sタンパク質と共通するエピトープに結合するクローンは少なかった後者の交差反応性B細胞クローンは,SARS-CoV-2Sタンパク質のみを認識するクローンに比べて体細胞超変異(somatic hypermutation)のレベルが高く,メモリーB細胞由来であることが示唆された今回の研究では,SARS-CoV-2 mRNAワクチンをヒトに接種すると,持続的なGC B細胞反応が誘導され,強固な液性免疫の生成が可能になることが示された

 

 

Figure 1: Plasmablast and antibody response to SARS-CoV-2 immunization.

a, Study design. Forty-one healthy adult volunteers (ages

28–73, 8 with history of SARS-CoV-2 infection) were enrolled and received

BNT162b2 mRNA SARS-CoV-2 vaccine. Blood was collected pre-immunization,

and 3, 4, 5, 7, and 15 weeks after immunization. For 14 participants (ages 28–52,

none with history of SARS-CoV-2 infection), fine needle aspirates (FNAs) of

ipsilateral axillary lymph nodes (LNs) were collected 3, 4, 5, 7, and 15 weeks after

immunization. b, c, ELISpot quantification of S-binding IgG- (b) and IgA- (c)

secreting plasmablasts (PBs) in blood at baseline, 3, 4, 5, and 7 weeks

post-immunization in participants without (red) and with (black) history of

SARS-CoV-2 infection. d, Plasma IgG titers against SARS-CoV-2 spike protein (S)

(left) and the receptor binding domain (RBD) of S (right) measured by ELISA in

participants without (red) and with (black) history of SARS-CoV-2 infection at

baseline, 3, 4, 5, 7, and 15 weeks post-immunization. Dotted lines indicate limits

of detection. Symbols at each timepoint in b–d represent one sample (n= 41).

Results are from one experiment performed in duplicate.

 

 

Figure 2: Germinal centre B cell response to SARS-CoV-2 immunization.

a, Representative color Doppler ultrasound image of two draining LNs “1”, and “2” adjacent to the axillary vein “LAX V” 5 weeks after immunization. b, c, Representative flow cytometry plots of Bcl6 and CD38 staining on IgDlo CD19+  CD3–  live singlet lymphocytes in FNA samples (b) and S staining on Bcl6+ CD38int GC B cells in tonsil and FNA samples (c) at the indicated times after immunization. d, e, Kinetics of total (blue) and S+  (white) GC B cells as gated in b and c (d) and S-binding percent of GC B cells (e) from FNA of draining lymph nodes. Symbols at each timepoint represent one FNA sample; square symbols denote second LN sampled (n = 14). Horizontal lines indicate the median.

 

 

Figure 3: Clonal analysis of GC response to SARS-CoV-2 immunization.

a, Binding of mAbs generated from GC B cells to SARS-CoV-2 S, N-terminal domain of S, RBD, or spike proteins of betacoronavirus OC43 or HKU1 measured by ELISA. Results are from one experiment performed in duplicate. Baseline for area under the curve was set to the mean + three times the standard deviation of background binding to bovine serum albumin. b, Clonal relationship of sequences from S-binding GC mAbs (cyan) to sequences from bulk repertoire analysis of PBs from PBMCs (red) and GC B cells (blue) sorted 4 weeks after immunization. Each clone is visualized as a network in which each node represents a sequence and sequences are linked as a minimum spanning tree of the network. Symbol shape indicates sequence isotype: IgG (circle), IgA (star), and IgM (square); symbol size corresponds to sequence count. c, d, Comparison of nucleotide mutation frequency in immunoglobulin heavy chain variable region (IGHV) genes of naïve B cells sorted from influenza vaccinees19 (grey) to clonal relatives of S-binding mAbs among PBs sorted from PBMCs and GC B cells 4 weeks after immunization (green) in indicated participants (c) and between clonal relatives of S-binding mAbs cross-reactive (purple) or not (teal) to seasonal coronavirus spike proteins among PBs sorted from PBMCs and GC B cells 4 weeks after immunization (d). Horizontal lines and error bars indicate the median and interquartile range. Sequence counts were 2,553 (naive), 199 (participant 07), 6 (participant 20), 240 (participant 22), 54 (cross-reactive), and 391 (not cross-reactive). P values from two-sided Kruskal–Wallis test with Dunn’s post-test between naïve B cells and S-binding clones (c) or two-sided Mann–Whitney U test (d).