• 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

    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

    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

    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.

    • L’immunité de troupeau naturelle à partir d’une vague initiale n’existe pas (#Manaus). Les seuls « vaccins » (in)disponibles ont des effets dont on ne sait pas à quel point ils sont limités. Le pari : compter sur des mutations nombreuses pour obtenir une immunité de troupeau naturelle, à moyen terme....

      Immunological characteristics govern the transition of COVID-19 to endemicity - View ORCID ProfileJennie S. Lavine1,*, View ORCID ProfileOttar N. Bjornstad2, View ORCID ProfileRustom Antia1
      https://science.sciencemag.org/content/early/2021/01/11/science.abe6522

      We are currently faced with the question of how the CoV-2 severity may change in the years ahead. Our analysis of immunological and epidemiological data on endemic human coronaviruses (HCoVs) shows that infection-blocking immunity wanes rapidly, but disease-reducing immunity is long-lived. Our model, incorporating these components of immunity, recapitulates both the current severity of CoV-2 and the benign nature of HCoVs, suggesting that once the endemic phase is reached and primary exposure is in childhood, CoV-2 may be no more virulent than the common cold. We predict a different outcome for an emergent coronavirus that causes severe disease in children. These results reinforce the importance of behavioral containment during pandemic vaccine rollout, while prompting us to evaluate scenarios for continuing vaccination in the endemic phase.

      #gouvernerlapandémie

    • Ah, Christian Drosten aborde très exactement ces deux points (effet de l’été, laisser filer l’épidémie une fois les personnes fragiles vaccinées) dans son interview de la semaine :
      https://www.spiegel.de/international/germany/interview-with-virologist-christian-drosten-i-am-quite-apprehensive-about-wh

      Drosten: Once the elderly and maybe part of the risk groups have been vaccinated, there will be immense economic, social, political and perhaps also legal pressure to end the corona measures. And then, huge numbers of people will become infected within just a short amount of time, more than we can even imagine at the moment. We won’t have 20,000 or 30,000 new cases a day, but up to 100,000 in a worst-case scenario. It will, of course, be primarily younger people who are less likely than older people to have severe symptoms, but when a huge number of younger people get infected, then the intensive care units will fill up anyway and a lot of people will die. Just that it will be younger people. We can cushion this terrible scenario somewhat by pushing the numbers way down now.

      DER SPIEGEL: Can we be confident that case numbers will begin to drop in spring as temperatures rise?

      Drosten: I don’t think so. The fact that we had such a relaxed summer in 2020 likely had to do with the fact that our case numbers remained below a critical threshold in the spring. But that’s not the case any longer. I am afraid that it will be more like in Spain, where case numbers climbed rapidly again after the lockdown was lifted, even though it was quite hot. In South Africa, too, where it is currently summer, case numbers are at a high level.

  • 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

    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