Research press release


Nature Medicine

Immunology: Neutralizing antibodies may be much less effective against the B.1.351 SARS-CoV-2 variant

新型コロナウイルス感染症(COVID-19)の回復期にある患者やワクチン接種を受けた人に由来する抗体は、重症急性呼吸器症候群コロナウイルス2(SARS-CoV-2)のB.1.1.7変異株(英国で最初に見つかった変異株)は中和できるが、B.1.351変異株(南アフリカで最初に見つかった変異株)に対しては、参照用のD614G株と比較した場合、中和できないか、もしくは中和効率が低い可能性があることが分かった。研究室での実験に基づくこの結果が、Nature Medicine に掲載される。この知見は、ワクチン接種完了者や感染から回復した患者では、B.1.1.7変異株に対しては抗体による防御がある程度働くものの、B.1.351変異株への感染リスクには抗体の影響がないことを示している。ただし、ワクチンを2回接種すると、これらの変異株に対する中和抗体応答は増強される。


O Schwartzたちは、感染性を持つB.1.1.7変異株とB.1.351変異株を感染者から単離し、抗体に対するこれらの変異株の応答を調べた。抗体は、ファイザー社ワクチンの初回接種から6週間以内の19人と、これらの変異株より前に出現したウイルス株への感染・発症後9か月以内のワクチン未接種者58人から採取された。



Antibodies from people convalescing from or vaccinated against COVID-19 can neutralize the B.1.1.7 SARS-CoV-2 variant (first identified in the UK), but they may be either unable or less able to neutralize the B.1.351 variant (first identified in South Africa) when compared to the reference strain D614G. The study, based on laboratory experiments, is published in Nature Medicine. The findings indicate that vaccinated and convalescent people have some antibody protection against the B.1.1.7 variant but may still be at risk of infection with the B.1.351 strain. Nevertheless, two doses of the vaccine do boost neutralizing antibody responses to these variants.

New SARS-CoV-2 variants, including the B.1.351 and B.1.1.7 strains, have spread to different countries, which has raised concerns about their ability to evade vaccines.

Olivier Schwartz and colleagues isolated infectious B.1.1.7 and B.1.351 strains from infected people. They then tested the strains’ responses to antibodies collected from 19 vaccinated people up to 6 weeks after the first dose of the Pfizer vaccine, and from 58 unvaccinated people who had been infected with an earlier strain of the virus up to 9 months after symptoms first began.

The authors found that antibodies from convalescent patients were able to neutralize the B.1.1.7 strain, but were much less effective against the B.1.351 strain. There was a six-fold reduction in neutralizing activity, and 40% of the samples lacked any activity at all against the South African strain. Similarly, antibodies from vaccinated people were able to neutralize the B.1.1.7 strain, but had less of an effect against the B.1.351 strain. Although neutralizing activity increased after the second dose of vaccine, it remained 14 times lower against B.1.351 than against the D614G strain.

The study is of particular value because it used authentic viral strains rather than lab-engineered proxies. The authors argue that although the findings warrant further investigation, antibodies are just part of the immune system’s response to infectious viruses. Other elements of the immune system, such as the ability of T cells to attack infected cells, may be more cross-reactive against these faster-spreading variants.

The full paper is available at:

doi: 10.1038/s41591-021-01318-5


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