Hi,
Ok, der doofe Bhakdi hatte mit der Kreuzimmunität zu "Erkältungsviren" wohl doch irgendwie recht, besonders bei Kindern und jungen Menschen (young adults) ist sie extrem bis sehr stark und schwächt dann mit zunehmendem Alter immer weiter ab:
Zitat:
Boosted immunity to the common cold might protect children from COVID-19
Zitat:
The biological age of an individual is the primary risk factor associated with the clinical severity of SARS-CoV-2 infection1,2. Although comorbidities (for example, cardiovascular disease and obesity) accumulate with age and thereby increase the chances of severe illness or fatal disease, they cannot explain why increasing age is an independent risk factor, or why, notably, SARS-CoV-2 infection tends to be mild or even asymptomatic in children and young adults. A deeper characterization of these age-related differences could improve our understanding of immune responses to SARS-CoV-2 generally and identify a profile of SARS-CoV-2-specific responses in children following natural infection that might enable optimal vaccination strategies for the young. In this issue of Nature Immunology, Dowell et al.3 quantitatively profile the convalescent serological (antibody) and cellular (T cell) immune responses to SARS-CoV-2 in a cohort of 91 children and 154 adults — one of the largest cohorts examined to date — who had mild or asymptomatic disease in the United Kingdom during the latter half of 2020. The authors provide evidence that children mount exceptional immune responses, when compared to adults, with pre-existing immunity cross-reactive with pre-pandemic ‘common cold’ human coronaviruses (HCoVs) as well as SARS-CoV-2. Dowell et al.3 postulate that these enhanced immune responses derive from prior HCoV exposures and demonstrate that they are upregulated, or ‘back boosted’, by SARS-CoV-2 infection.
Zitat:
The importance of age as a risk factor is underscored by early estimates in 2020 that adults >65 years in age represented 80% of hospitalizations and had a 23-fold greater risk of death than those <65 years of age2. This trend has been maintained throughout the pandemic, and according to recent calculations, almost 76% of ~737,000 cumulative deaths in the United States (as of 27 October 2021) were of individuals aged ≥65 years4. Notably, the hospitalization or death rate in this age range is approximately 1,000–8,000 times higher than in the 0–17-year old reference group. In one landmark analysis, the infection fatality ratio was calculated to be the lowest among children (aged 5–9 years), with a log-linear increase by age among individuals older than 30 years1. These observations lead us to the question of how immune responses to SARS-CoV-2 might differ in children versus adults.
Zitat:
Compared with adults, children showed an intriguing yet statistically insignificant trend for overall higher spike-reactive antibody production. With regard to HCoV antibody levels, titers against HCoVs were evident in SARS-CoV-2 seropositive children and adults, which were boosted compared to their respective seronegative groups. Antibody levels against all four HCoVs were boosted most in the SARS-CoV-2 seropositive children and reached statistical significance for HKU-1 and OC43. Importantly, no significant change was detected in the antibody titers against unrelated respiratory viruses (that is, influenza A virus and respiratory syncytial virus), demonstrating that this effect was specific to HCoVs. These data indicate that SARS-CoV-2 infection in children specifically and significantly back boosts pre-existing immunity to OC43 and HKU-1. Moreover, the authors demonstrate quantitatively that the back-boosted OC43 and HKU1 plasma antibody in seropositive children is predominantly cross-reactive with the SARS-CoV-2 S2 domain, explaining the higher SARS-CoV-2-specific titer in children.
Zitat:
Aside from the humoral immune response, Dowell et al.3 compared T cell responses in children versus adults. Mirroring the antibody profiles, children also developed robust cellular immune responses to the spike protein following SARS-CoV-2 infection. Using an interferon-γ (IFN-γ) enzyme-linked immune absorbent spot (ELISpot) and overlapping peptide pools derived from the spike glycoprotein and a combination of nucleocapsid, membrane and envelope proteins, T cell responses were similarly frequent in SARS-CoV-2 seropositive children (33/37) and adults (51/64), but the number of spot-forming cells was twice as high in the children. A reduced number of cross-reactive T cells in adults could result in inadequate control of SARS-CoV-2 infection. Furthermore, using a multi-analyte bead assay and flow cytometry, it was shown that IL-2– TNF+ IFN-γ+ CD8+ T cells (where IL-2 is interleukin 2; and TNF is tumor necrosis factor) comprise the majority of the spike-specific T cell repertoire, and that IL-2 production is markedly reduced among virus-specific T cell responses in children. With a combination of SARS-CoV-2 seronegative volunteers and pre-pandemic negative volunteers, the authors have documented the increased presence of HCoV–SARS-CoV-2 spike cross-reactive T cell responses in a high proportion of children.
https://www.nature.com/articles/s41590-021-01094-x
Gruß
Alef
