Rapid generation of durable B cell memory to #SARS-CoV-2 spike and nucleocapsid proteins in COVID-19 and convalescence | Science Immunology
▻https://immunology.sciencemag.org/content/5/54/eabf8891.full
[...] antibodies are detectable from approximately 6 days after PCR confirmation of infection, and those directed against spike receptor binding domain (RBD) show neutralizing capacity and hence, can prevent infection. However, the rapid decline of anti-SARS-CoV-2 serum IgG levels beyond 20 days post-diagnosis and the transient presence of circulating plasmablasts have led to questions about the longevity of immunity. In contrast, antigen-specific memory T cells and memory B (#Bmem) cells can be detected in convalescence. As these memory cells are programmed to respond rapidly upon subsequent antigen encounter, it is reasonable to hypothesize that these long-lived memory cells provide durable long-term immunity (4, 25). However, detailed insight into the nature and longevity of the Bmem cell compartment specific to SARS-CoV-2 is currently still unresolved.
We extensively characterized the SARS-CoV-2-specific Bmem cell compartment using unique sets of fluorescently-labeled recombinant tetramers of the SARS-CoV-2 RBD and NCP antigens in combination with an extensive flow cytometry panel. The SARS-CoV-2-specific Bmem cells were quantified and characterized in 36 samples from 25 patients with COVID-19 or in convalescence. Circulating RBD- and NCP-specific Bmem cell subsets were detected early after infection and persisted over 242 days post-symptom onset. Early after infection, antigen-specific Bmem cells predominantly expressed IgM, followed over time by a predominance of IgG1. RBD-specific Bmem cell numbers were found to positively correlate with circulating TFH cell numbers suggesting prolonged germinal center (GC) activity. These analyses highlight that a decline in serum antibodies in convalescence may not reflect waning of immunity, but rather a contraction of the immune response with the development and persistence of B cell memory.
#Covid-19 : une réponse immunitaire qui persiste au moins huit mois après les premiers symptômes
▻https://www.lemonde.fr/sciences/article/2020/12/24/covid-19-une-reponse-immunitaire-qui-persiste-au-moins-huit-mois-apres-les-p
Une étude australienne, publiée mardi 22 décembre dans la revue Science Immunology, offre un nouvel éclairage. Elle montre, chez 25 patients atteints du Covid-19 à des degrés variables puis convalescents, la présence d’une #immunité durable – au moins huit mois – qui mobilise des cellules B « mémoires », c’est-à-dire spécialisées contre ce virus.
Ce résultat s’ajoute à ceux de quatre autres publications, qui toutes parviennent à une conclusion analogue. « Après une infection naturelle, ce virus peut déclencher la production de #cellules_mémoires spécifiques qui persistent un certain temps dans l’organisme. Cela laisse espérer que la #vaccination saura mobiliser ces mêmes cellules d’une manière au moins aussi efficace », estime Simon Fillatreau, professeur d’immunologie à l’Institut Necker - Enfants malades (AP-HP, Inserm, CNRS, Université de Paris).