デルタ株の感染能力とワクチン中和能力の評価

2019年12月から今までの
新型コロナウィルス系統、株の勢力を追跡すると、
増殖率の高い系統、株が支配的になっています。
初めはイギリスで勢力を広げたB.1.1.7(アルファ株)でした。
その後、インドで広がりを見せたB.1.617.2(デルタ株)が
今年の4月くらいから一気に広がりを見せています。
参考文献(1)のFig.1aを見る限り
今までで最大の広がりとなっています。
デルタ株は従来の株よりも1200倍、
ウィルス量が多い事が示されていました。
Petra Mlcochova氏らが試験管によるVERO細胞を使った
培養環境によると同様に1000倍近い増加が
デルタ株で見られています(アルファ株に対して)(1)。
デルタ株は細胞内に取り込まれる際に
膜融合する合胞体形成の効率が高いことが一つ挙げられています。
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ここで考えないといけないのが
今、世界的に接種が進められているワクチンの効果と
今後生じるかもしれない、
さらに感染性の高い変異が起こるかどうか？です。
ワクチンは今、普及しているものは
デルタ株に合わせて設計されたものではないからです。
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デルタ株に対するワクチンの中和能力に関しては
アルファ株に対して2倍程度効果が下がることが示されています。
また、ワクチンの種類において
アストラゼネカのChAdOx-1は
中和能力がファイザー/ビオンテック社のBNT162b2よりも
中央値は低いという結果になっています(Fig.1e)(1)。
またアストラゼネカのアデノウィルスワクチンは
個人差がファイザーのmRNAワクチンよりも大きくなっています。
ただし、この差が予防効果、中-重症への発展において
どのように疫学的に反映されるかはわかりません。
ワクチン接種が進んでいる世界の感染状況を見ても、
ある程度はブレークスルー感染は生じるかもしれません。
その際、中等症、重症、後遺症が
どのようになるかについては
日本においては1か月、2か月後くらいにはわかってくると思います。
感染には様々なデータから波があるという特徴があります。
日本が今経験している第5波が落ち着いて、
第6波がどのようになるか？
というところで若い人も含めて統計的にわかってくると思います。
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もう一つの懸念は
今後、デルタ株よりもさらに強力な変異が生じるかどうか？です。
デルタ株は通常のACE2のエピトープの親和性だけではなく
その後のへき開、膜融合の所に変異が生じています。
このようなウィルスの複数の段階を経たライフサイクルにおいて
それとは別の経路で変異が生じる可能性もあります。
例えば、細胞内に入った後、増殖率が上がるような変異が
デルタ株の特徴を持ち合わせた上で入る可能性も0ではありません。
基本的にデルタ株よりも感染力が弱い
ワイルドタイプやアルファ株がワクチンによって
感染が落ち着いた後に再度、勢力を増すことはない
と考えています。
基本的に社会において主要となる株は
感染力が一番高い株であると考えています。
今は、それは1000倍以上の差があるデルタ株です。
従って、デルタ株が今後どのように変異するかというのは
注視する必要があると考えています。

(参考文献)
(1)
Petra Mlcochova, Steven Kemp, Mahesh Shanker Dhar, Guido Papa, Bo Meng, Isabella A. T. M. Ferreira, Rawlings Datir, Dami A. Collier, Anna Albecka, Sujeet Singh, Rajesh Pandey, Jonathan Brown, Jie Zhou, Niluka Goonawardane, Swapnil Mishra, Charles Whittaker, Thomas Mellan, Robin Marwal, Meena Datta, Shantanu Sengupta, Kalaiarasan Ponnusamy, Venkatraman Srinivasan Radhakrishnan, Adam Abdullahi, Oscar Charles, Partha Chattopadhyay, Priti Devi, Daniela Caputo, Tom Peacock, Dr Chand Wattal, Neeraj Goel, Ambrish Satwik, Raju Vaishya, Meenakshi Agarwal, The Indian SARS-CoV-2 Genomics Consortium (INSACOG), The Genotype to Phenotype Japan (G2P-Japan) Consortium, The CITIID-NIHR BioResource COVID-19 Collaboration, Antranik Mavousian, Joo Hyeon Lee, Jessica Bassi, Chiara Silacci-Fegni, Christian Saliba, Dora Pinto, Takashi Irie, Isao Yoshida, William L. Hamilton, Kei Sato, Samir Bhatt, Seth Flaxman, Leo C. James, Davide Corti, Luca Piccoli, Wendy S. Barclay, Partha Rakshit, Anurag Agrawal & Ravindra K. Gupta
SARS-CoV-2 B.1.617.2 Delta variant replication and immune evasion
Nature (2021)
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Author information
/Author notes/
These authors contributed equally: Petra Mlcochova, Steven Kemp, Mahesh Shanker Dhar, Partha Rakshit, Anurag Agrawal and Ravindra K. Gupta
/Affiliations/
Cambridge Institute of Therapeutic Immunology & Infectious Disease (CITIID), Cambridge, UK
Petra Mlcochova, Steven Kemp, Bo Meng, Isabella A. T. M. Ferreira, Rawlings Datir, Adam Abdullahi, Stephen Baker, Gordon Dougan, Paul J. Lehner, Paul A. Lyons, Nicholas J. Matheson, Ben Bullman & Ravindra K. Gupta
Department of Medicine, University of Cambridge, Cambridge, UK
Petra Mlcochova, Steven Kemp, Bo Meng, Isabella A. T. M. Ferreira, Rawlings Datir, Dami A. Collier, Adam Abdullahi, Stephen Baker, Gordon Dougan, Christoph Hess, Paul J. Lehner, Paul A. Lyons, Nicholas J. Matheson, Charlotte Summers, James E. D. Thaventhiran, Mark Toshner, Michael P. Weekes, Benjamin J. Dunmore, Stefan Gräf, Kelvin Hunter, Ekaterina Legchenko, Cecilia Matara, Jennifer Martin, Federica Mescia, Ciara O’Donnell, Linda Pointon, Nicole Pond, Joy Shih, Rachel Sutcliffe, Tobias Tilly, Carmen Treacy, Zhen Tong, Jennifer Wood, Marta Wylot, Laura Bergamaschi, Ariana Betancourt, Georgie Bower, Chiara Cossetti, Aloka De Sa, Madeline Epping, Stuart Fawke, Nick Gleadall, Richard Grenfell, Andrew Hinch, Sarah Jackson, Isobel Jarvis, Ben Krishna, Ommar Omarjee, Marianne Perera, Martin Potts, Nathan Richoz, Veronika Romashova, Luca Stefanucci, Mateusz Strezlecki, Lori Turner, Eckart M. D. D. De Bie, Katherine Bunclark, Masa Josipovic, Michael Mackay, William L. Hamilton & Ravindra K. Gupta
University College London, London, UK
Steven Kemp, Dami A. Collier, Oscar Charles & Georgina Okecha
National Centre for Disease Control, Delhi, India
Mahesh Shanker Dhar, Sujeet Singh, Robin Marwal, Meena Datta, Kalaiarasan Ponnusamy, Venkatraman Srinivasan Radhakrishnan, Himanshu Chauhan, Tanzin Dikid, Hema Gogia, Hemlata Lall, Kaptan Verma, Mahesh S. Dhar, Manoj K. Singh, Namita Soni, Namonarayan Meena, Preeti Madan, Priyanka Singh, Ramesh Sharma, Rajeev Sharma, Sandhya Kabra, Sattender Kumar, Swati Kumari, Uma Sharma, Urmila Chaudhary, Josh Hodgson, Christopher Huang, Daniel Lewis, Joe Marsden, Natalia Savinykh Yarkoni, Rahul Sharma, Mayurun Selvan, Samir Bhatt & Partha Rakshit
MRC – Laboratory of Molecular Biology, Cambridge, UK
Guido Papa, Anna Albecka & Leo C. James
CSIR Institute of Genomics and Integrative Biology, Delhi, India
Rajesh Pandey, Sridhar Sivasubbu & Vinod Scaria
Department of Infectious Diseases, Imperial College London, London, UK
Jonathan Brown, Jie Zhou, Niluka Goonawardane, Shantanu Sengupta, Partha Chattopadhyay, Priti Devi & Anurag Agrawal
Medical Research Council (MRC) Centre for Global Infectious Disease Analysis, Jameel Institute, School of Public Health, Imperial College London, London, UK
Swapnil Mishra, Charles Whittaker, Thomas Mellan, Tom Peacock & Wendy S. Barclay
NIHR Bioresource, Cambridge, UK
Daniela Caputo, Nathalie Kingston, John Allison, Helen Butcher, Daniela Caputo, Debbie Clapham-Riley, Eleanor Dewhurst, Anita Furlong, Barbara Graves, Jennifer Gray, Tasmin Ivers, Mary Kasanicki, Emma Le Gresley, Rachel Linger, Sarah Meloy, Francesca Muldoon, Nigel Ovington, Sofia Papadia, Isabel Phelan, Hannah Stark & Jennifer Webster
Sri Ganga Ram Hospital, New Delhi, India
Dr Chand Wattal, Neeraj Goel, Ambrish Satwik, Chand Wattal, J. K. Oberoi, Reena Raveendran & S. Datta
Indraprastha Apollo Hospital, New Delhi, India
Raju Vaishya
Northern Railway Central Hospital, New Delhi, India
Meenakshi Agarwal & Kathleen E. Stirrups
Wellcome-MRC Cambridge Stem Cell Institute, Cambridge, UK
Antranik Mavousian & Joo Hyeon Lee
Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
Joo Hyeon Lee
Humabs Biomed SA, a subsidiary of Vir Biotechnology, 6500, Bellinzona, Switzerland
Sarah Spencer, Jessica Bassi, Chiara Silacci-Fegni, Christian Saliba, Dora Pinto, Davide Corti & Luca Piccoli
Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, 7348551, Japan
Ryoko Kawabata, Nanami Morizako & Takashi Irie
Tokyo Metropolitan Institute of Public Health, Tokyo, 1690073, Japan
Kenji Sadamasu, Hiroyuki Asakura, Mami Nagashima, Kazuhisa Yoshimura & Isao Yoshida
Division of Systems Virology, The Institute of Medical Science, The University of Tokyo, Tokyo, 1088639, Japan
Jumpei Ito, Izumi Kimura, Keiya Uriu, Yusuke Kosugi, Mai Suganami, Akiko Oide, Miyabishara Yokoyama, Mika Chiba & Kei Sato
CREST, Japan Science and Technology Agency, Saitama, 3220012, Japan
Kei Sato
Section of Epidemiology, Department of Public Health, University of Copenhagen, Copenhagen, Denmark
Samir Bhatt
Department of Mathematics, Imperial College London, London, UK
Caroline Saunders & Seth Flaxman
Africa Health Research Institute, Durban, South Africa
Willem H. Owehand, Jonathan Stephens, Kathleen E. Stirrups & Ravindra K. Gupta
National Institute of Biomedical Genomics, Kalyani, West Bengal, India
Saumitra Das, Arindam Maitra, Sreedhar Chinnaswamy & Nidhan Kumar Biswas
Institute of Life Sciences (ILS), Bhubaneswar, India
Ajay Parida, Sunil K. Raghav & Punit Prasad
InSTEM/ NCBS, Bangalore, India
Apurva Sarin, Satyajit Mayor, Uma Ramakrishnan, Dasaradhi Palakodeti & Aswin Sai Narain Seshasayee
Centre for DNA Fingerprinting and Diagnostics, Hyderabad, India
K. Thangaraj, Murali Dharan Bashyam & Ashwin Dalal
National Centre for Cell Science, Pune, India
Manoj Bhat, Yogesh Shouche & Ajay Pillai
National Institute of Virology, Pune, India
Priya Abraham, Potdar Varsha Atul & Sarah S. Cherian
National Institute of Mental Health and Neuroscience, Bangalore, India
Anita Sudhir Desai, Chitra Pattabiraman, M. V. Manjunatha, Reeta S. Mani & Gautam Arunachal Udupi
Centre for Cellular and Molecular Biology, Hyderabad, India
Vinay Nandicoori, Karthik Bharadwaj,  Tallapaka, Divya Tej Sowpati & Mary Kasanicki
University of Miyazaki, Miyazaki, Japan
Akatsuki Saito, Erika P. Butlertanaka, Yuri L. Tanaka & Emma Jones
Kumamoto University, Kumamoto, Japan
Terumasa Ikeda, Chihiro Motozono, Hesham Nasser, Ryo Shimizu, Yue Yuan, Kazuko Kitazato & Haruyo Hasebe
Tokai University, Tokyo, Japan
So Nakagawa, Jiaqi Wu & Miyoko Takahashi
Hokkaido University, Sapporo, Japan
Takasuke Fukuhara, Kenta Shimizu, Kana Tsushima & Haruko Kubo
Kyoto University, Kyoto, Japan
Kotaro Shirakawa, Yasuhiro Kazuma, Ryosuke Nomura, Yoshihito Horisawa & Akifumi Takaori-Kondo
National Institute of Infectious Diseases, Tokyo, Japan
Kenzo Tokunaga & Seiya Ozono
Cambridge University Hospitals NHS Trust, Cambridge, UK
Patrick Maxwell, Ashley Shaw, Alice Michael, Sabrina Rossi & Cissy Yong
Cambridge Clinical Research Centre, NIHR Clinical Research Facility, Cambridge University Hospitals NHS Foundation Trust, Addenbrooke’s Hospital, Cambridge, CB2 0QQ, UK
Ashlea Bucke, Jo Calder, Laura Canna, Jason Domingo, Anne Elmer, Stewart Fuller, Julie Harris, Sarah Hewitt, Jane Kennet, Sherly Jose, Jenny Kourampa, Anne Meadows, Criona O’Brien, Jane Price, Cherry Publico, Rebecca Rastall, Carla Ribeiro, Jane Rowlands, Valentina Ruffolo & Hugo Tordesillas
Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QW, UK
Stuart Fawke & Oisin Huhn
University of Cambridge, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK
Francesca Nice, Helen Butcher, Daniela Caputo, Debbie Clapham-Riley, Eleanor Dewhurst, Anita Furlong, Barbara Graves, Jennifer Gray, Tasmin Ivers, Emma Le Gresley, Rachel Linger, Sarah Meloy, Francesca Muldoon, Sofia Papadia, Isabel Phelan, Hannah Stark, Paul Townsend, Neil Walker, Jennifer Webster, Ingrid Scholtes, Sabine Hein & Rebecca King
/Consortia/
The Indian SARS-CoV-2 Genomics Consortium (INSACOG)
Himanshu Chauhan, Tanzin Dikid, Hema Gogia, Hemlata Lall, Kalaiarasan Ponnusamy, Kaptan Verma, Mahesh S. Dhar, Manoj K. Singh, Meena Datta, Namita Soni, Namonarayan Meena, Preeti Madan, Priyanka Singh, Ramesh Sharma, Rajeev Sharma, Sandhya Kabra, Sattender Kumar, Swati Kumari, Uma Sharma, Urmila Chaudhary, Sridhar Sivasubbu, Vinod Scaria, Chand Wattal, J. K. Oberoi, Reena Raveendran, S. Datta, Saumitra Das, Arindam Maitra, Sreedhar Chinnaswamy, Nidhan Kumar Biswas, Ajay Parida, Sunil K. Raghav, Punit Prasad, Apurva Sarin, Satyajit Mayor, Uma Ramakrishnan, Dasaradhi Palakodeti, Aswin Sai Narain Seshasayee, K. Thangaraj, Murali Dharan Bashyam, Ashwin Dalal, Manoj Bhat, Yogesh Shouche, Ajay Pillai, Priya Abraham, Potdar Varsha Atul, Sarah S. Cherian, Anita Sudhir Desai, Chitra Pattabiraman, M. V. Manjunatha, Reeta S. Mani, Gautam Arunachal Udupi, Vinay Nandicoori, Karthik Bharadwaj,  Tallapaka & Divya Tej Sowpati
The Genotype to Phenotype Japan (G2P-Japan) Consortium
Ryoko Kawabata, Nanami Morizako, Kenji Sadamasu, Hiroyuki Asakura, Mami Nagashima, Kazuhisa Yoshimura, Jumpei Ito, Izumi Kimura, Keiya Uriu, Yusuke Kosugi, Mai Suganami, Akiko Oide, Miyabishara Yokoyama, Mika Chiba, Akatsuki Saito, Erika P. Butlertanaka, Yuri L. Tanaka, Terumasa Ikeda, Chihiro Motozono, Hesham Nasser, Ryo Shimizu, Yue Yuan, Kazuko Kitazato, Haruyo Hasebe, So Nakagawa, Jiaqi Wu, Miyoko Takahashi, Takasuke Fukuhara, Kenta Shimizu, Kana Tsushima, Haruko Kubo, Kotaro Shirakawa, Yasuhiro Kazuma, Ryosuke Nomura, Yoshihito Horisawa, Akifumi Takaori-Kondo, Kenzo Tokunaga & Seiya Ozono
The CITIID-NIHR BioResource COVID-19 Collaboration
Stephen Baker, Gordon Dougan, Christoph Hess, Nathalie Kingston, Paul J. Lehner, Paul A. Lyons, Nicholas J. Matheson, Willem H. Owehand, Caroline Saunders, Charlotte Summers, James E. D. Thaventhiran, Mark Toshner, Michael P. Weekes, Patrick Maxwell, Ashley Shaw, Ashlea Bucke, Jo Calder, Laura Canna, Jason Domingo, Anne Elmer, Stewart Fuller, Julie Harris, Sarah Hewitt, Jane Kennet, Sherly Jose, Jenny Kourampa, Anne Meadows, Criona O’Brien, Jane Price, Cherry Publico, Rebecca Rastall, Carla Ribeiro, Jane Rowlands, Valentina Ruffolo, Hugo Tordesillas, Ben Bullman, Benjamin J. Dunmore, Stuart Fawke, Stefan Gräf, Josh Hodgson, Christopher Huang, Kelvin Hunter, Emma Jones, Ekaterina Legchenko, Cecilia Matara, Jennifer Martin, Federica Mescia, Ciara O’Donnell, Linda Pointon, Nicole Pond, Joy Shih, Rachel Sutcliffe, Tobias Tilly, Carmen Treacy, Zhen Tong, Jennifer Wood, Marta Wylot, Laura Bergamaschi, Ariana Betancourt, Georgie Bower, Chiara Cossetti, Aloka De Sa, Madeline Epping, Stuart Fawke, Nick Gleadall, Richard Grenfell, Andrew Hinch, Oisin Huhn, Sarah Jackson, Isobel Jarvis, Ben Krishna, Daniel Lewis, Joe Marsden, Francesca Nice, Georgina Okecha, Ommar Omarjee, Marianne Perera, Martin Potts, Nathan Richoz, Veronika Romashova, Natalia Savinykh Yarkoni, Rahul Sharma, Luca Stefanucci, Jonathan Stephens, Mateusz Strezlecki, Lori Turner, Eckart M. D. D. De Bie, Katherine Bunclark, Masa Josipovic, Michael Mackay, Federica Mescia, Alice Michael, Sabrina Rossi, Mayurun Selvan, Sarah Spencer, Cissy Yong, John Allison, Helen Butcher, Daniela Caputo, Debbie Clapham-Riley, Eleanor Dewhurst, Anita Furlong, Barbara Graves, Jennifer Gray, Tasmin Ivers, Mary Kasanicki, Emma Le Gresley, Rachel Linger, Sarah Meloy, Francesca Muldoon, Nigel Ovington, Sofia Papadia, Isabel Phelan, Hannah Stark, Kathleen E. Stirrups, Paul Townsend, Neil Walker, Jennifer Webster, Ingrid Scholtes, Sabine Hein & Rebecca King