/2021

Durability of mRNA-1273 vaccine–induced antibodies against #SARS-CoV-2 #variants | Science
▻https://science.sciencemag.org/content/early/2021/08/11/science.abj4176.full

https://science.sciencemag.org/content/early/2021/08/11/science.abj4176/F1.large.jpg

SARS-CoV-2 #mutations may diminish vaccine-induced protective immune responses, particularly as antibody titers wane over time. Here, we assess the impact of SARS-CoV-2 variants B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma), B.1.429 (Epsilon), B.1.526 (Iota), and B.1.617.2 (Delta) on binding, neutralizing, and ACE2-competing antibodies elicited by the vaccine mRNA-1273 over seven months. Cross-reactive neutralizing responses were rare after a single dose. At the peak of response to the second vaccine dose, all individuals had responses to all variants. Binding and functional antibodies against variants persisted in most subjects, albeit at low levels, for 6-months after the primary series of the mRNA-1273 vaccine. Across all assays, B.1.351 had the lowest antibody recognition. These data complement ongoing studies to inform the potential need for additional boost vaccinations.

#immunité #vaccins #vaccination

Our immune systems blanket the #SARS-CoV-2 spike protein with antibodies | EurekAlert! Science News
▻https://www.eurekalert.org/pub_releases/2021-05/uota-ois050321.php

https://www.eurekalert.org/multimedia/pub/web/263793_web.jpg

Previous research focused on one group of antibodies that target the most obvious part of the coronavirus’s spike protein, called the receptor-binding domain (RBD). Because the RBD is the part of the spike that attaches directly to human cells and enables the virus to infect them, it was rightly assumed to be a primary target of the immune system. But, testing blood plasma samples from four people who recovered from SARS-CoV-2 infections, the researchers found that most of the antibodies circulating in the blood — on average, about 84% — target areas of the viral spike protein outside the RBD — and, apparently, for good reason.

“We found these antibodies are painting the entire spike, both the arc and the stalk of the spike protein, which looks a bit like an umbrella,” [...] “The immune system sees the entire spike and tries to neutralize it.”

Many of these non-RBD-directed antibodies the team identified act as a potent weapon against the virus by targeting a region in a part of the spike protein located in what would be the umbrella’s canopy called the N-terminal domain (NTD). These antibodies neutralize the virus in cell cultures and were shown to prevent a lethal mouse-adapted version of the virus from infecting mice.

The NTD is also a part of the viral spike protein that mutates frequently, especially in several variants of concern. This suggests that one reason these #variants are so effective at evading our immune systems is that they can mutate around one of the most common and potent types of antibody in our arsenals.

[...]

Despite these maneuvers by SARS-CoV-2, the researchers said about 40% of the circulating antibodies target the stalk of the spike protein, called the S2 subunit, which is also a part that the virus does not seem able to change easily.

“That’s reassuring,” Ippolito said. “That’s an advantage our immune system has. It also means our current vaccines are eliciting antibodies targeting that S2 subunit, which are likely providing another layer of protection against the virus.”

#anticorps

Source: Prevalent, protective, and convergent IgG recognition of SARS-CoV-2 non-RBD spike epitopes | Science
▻https://science.sciencemag.org/content/early/2021/05/03/science.abg5268.full

#COVID-19 : Le #variant brésilien capable d’échappement immunitaire | santé log
▻https://www.santelog.com/actualites/covid-19-le-variant-bresilien-capable-dechappement-immunitaire

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Sur la base d’un modèle épidémiologique pour estimer son degré de transmissibilité, les chercheurs estiment que P.1 est susceptible d’être entre 1,7 et 2,4 fois plus transmissible que les lignées non-P1 du coronavirus.

Enfin, ils concluent également que P.1 est susceptible de pouvoir échapper à entre 10 et 46% de l’#immunité acquise par une infection par un coronavirus non-P.1.
 
Des résultats qui appellent à une surveillance accrue des infections et des différentes souches du virus absolument indispensable pour parvenir à maîtriser la pandémie.

Source :
Genomics and epidemiology of the P.1 #SARS-CoV-2 lineage in #Manaus, Brazil | Science
▻https://science.sciencemag.org/content/early/2021/04/13/science.abh2644.full

Prospective mapping of viral mutations that escape antibodies used to treat COVID-19 | Science
▻https://science.sciencemag.org/content/early/2021/01/22/science.abf9302.full

https://science.sciencemag.org/content/early/2021/01/22/science.abf9302/F1.large.jpg

Of course, our maps still do not answer the most pressing question: will SARS-CoV-2 evolve widespread resistance to these antibodies? But certainly, it is concerning that so many escape mutations impose little cost on RBD folding or receptor affinity, and that some are already present at low levels among circulating viruses. Ultimately, it will be necessary to wait and see what mutations spread as #SARS-CoV-2 circulates in the human population. Our work will help with the “seeing,” by enabling immediate interpretation of the effects of the mutations cataloged by viral genomic surveillance.

#variants #vaccins

Est-ce que, vu que ça fait un an que ça dure, on a une théorie un peu sérieuse sur l’effet de l’arrivée de l’été sur le virus ?

Parce que de ce que je vois, la situation est mauvaise en ce moment au Brésil, où c’est l’été.

Je vous dis ce que je crains ? Si on continue avec ces pseudo-confinements qui se contentent de bloquer la progression, sans réellement d’effet à la baisse, on va se maintenir à des niveaux très élevés de circulation du virus, et je ne vois pas dans ce cas comment on pourrait rouvrir quoi que ce soit de restauration, de bistrots et de culturel pour l’été.

À moins que le pari est que d’ici là, on aura vacciné au moins la population la plus fragile, et que donc on pourra laisser s’ébattre le virus dans la population, avec un taux de mortalité bien plus faible et donc sans saturer les réas. Ce qui me semble un choix excessivement risqué.

Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection | Science
▻https://science.sciencemag.org/content/early/2021/01/06/science.abf4063.full

#COVID-19 : De bonnes nouvelles sur le front de l’immunité | santé log
▻https://www.santelog.com/actualites/covid-19-de-bonnes-nouvelles-sur-le-front-de-limmunite

https://www.santelog.com/sites/santelog.com/www.santelog.com/files/images/accroche/adobestock_330189630_covid_m_0.jpeg

L’équipe de Jennifer M Dan du Center for Infectious Disease and Vaccine Research du La Jolla Institute for Immunology (Californie) a donc recruté plus de 180 hommes et femmes rétablis du COVID-19. 7% de ces participants avaient été hospitalisés mais la majorité avait développé une forme légère de la maladie. La plupart des participants ont fourni un échantillon de sang dès le 6è à 8è jour après l’apparition des symptômes. Les chercheurs ont pu suivre ainsi dans 254 échantillons au total, provenant de 188 cas de COVID-19, les anticorps, les cellules B (qui produisent les anticorps) et deux types de cellules T (qui tuent les cellules infectées). Ce suivi montre que :
les anticorps, dont les anticorps dirigés contre les composants de la protéine de pointe, ne présentent que des baisses modestes 6 à 8 mois après l’apparition des symptômes ; les cellules T, ne montrent qu’une légère « décomposition » au fil du temps, les cellules B ont augmenté en nombre dans certains cas.

Protective immunity against #SARS-CoV-2 could last eight months or more | EurekAlert! Science News
▻https://www.eurekalert.org/pub_releases/2021-01/ljif-pia010621.php

The team cautions that protective immunity does vary dramatically from person to person. In fact, the researchers saw a 100-fold range in the magnitude of immune memory. People with a weak immune memory may be vulnerable to a case of recurrent COVID-19 in the future, or they may be more likely to infect others.

“There are some people that are way down at the bottom of how much immune memory they have, and maybe those people are a lot more susceptible to reinfection,” says Crotty.

#immunité #anticorps