COVID-19 Research in Brief: 4 April to 10 April, 2020
A study surveying levels of neutralizing antibodies (NAbs) to the SARS-CoV-2 spike protein in the plasma of 175 patients who had recovered from COVID-19 in one health center in Shanghai, China, published on medRxiv, [en cours d’évaluation par les pairs] shed some light on the development of natural immunity to the virus. These results have not yet been peer-reviewed. Though patients in this study were classified as mild cases, antibody levels correlated positively with C-reactive protein and inversely with lymphocyte counts (NAb levels also tended to be higher in older subjects). A troublesome finding of the study was that approximately 30% of recovered patients showed low NAb titers, including 10 patients with NAbs below the detection limit of the assay.
En dehors du cas de la #vaccination, l’#immunité de groupe est atteignable dans certaines conditions sans qu’il est besoin d’avoir 60% de la population contaminée du fait que le virus atteint d’abord les personnes les plus exposées donc les plus propagatrices ; ce n’est cependant pas pour demain la veille conclue l’auteur.
Étude de la réponse immunitaire dans les COVID-19 ne nécessitant pas une hospitalisation et recherche d’une immunité croisée chez les sujets (a priori ?) non exposés au sars-cov2.
Antibodies — protective proteins made in response to an infection — may last only two to three months, especially in people who never showed symptoms while they were infected.
Humoral and cellular immunity:
a brief re-introduction
The initial host response to infection depends on cells of the innate immune system, such as macrophages and neutrophils. Subsequent to this, the antigen-specific T and B cells of the adaptive immune system are activated and differentiate in response to the pathogen. B cells are responsible for the production of antibodies to pathogen-specific antigens, including viral structural proteins such as the spike (S) protein in the case of SARS-CoV-2. T cells comprise various subtypes that include CD4+ T lymphocytes (T helper cells, or Th cells) and CD8+ T lymphocytes (cytotoxic T cells, or Tc cells). CD8+ T lymphocytes are so-called cytotoxic T cells because they directly kill cells expressing viral antigens, whereas CD4+ lymphocytes classically secrete various cytokines that “help” stimulate other immune cells (see Figure 1 below).
[“Cytotoxic T lymphocytes (CTLs) are generated by immune activation of cytotoxic T cells (Tc cells).“]
In conclusion, it is now established that SARS-CoV-2 pre-existing immune reactivity exists to some degree in the general population. It is hypothesized, but not yet proven, that this might be due to immunity to CCCs [‘common cold’ coronaviruses].