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Ursprungligen postat av
lisett
Det är inga "larm" det är obekräftade rykten. Man vet inte om det beror på dåliga tester, falska testresultat eller faktisk återaktivering. Lär dröja innan vi får svar på det. Troligaste förklaringen är testproblem.
Nu gissar du. Det är inget obekräftat rykte.
Här är ett utdrag ur "preprinten" till en Kinesisk studie som pekar på att immunitet efter en Covid-19 infektion inte är ett självklart antagande.
https://www.medrxiv.org/content/10.1101/2020.03.30.20047365v1.full.pdf
Neutralizing antibody responses to SARS-CoV-2 in a COVID-19 recovered patient cohort and their implications
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Discussion
Spread of the COVID-19 global pandemic highlights the urgent need to develop effective treatments or vaccines against SARS-CoV-2 infection. NAbs have been considered as an effective drug to treat or prevent virus infection. Here we evaluated the level of NAbs in recovered patients of COVID-19 by using a PsVs neutralization assay, which has been extensively used for the evaluation of NAbs for many highly pathogenic viruses, including Ebola, 13 highly pathogenic influenza virus, 14,15 SARS-
CoV, 16 and MERS-CoV. 17 The PsVs neutralization assay was also used for the evaluation of NAbs for SARS-CoV-2 in some recent reports, 11,18,19 generating consistent results compared with traditional plaque reduction neutralization assay. 18
We found that most COVID-19 patients developed SARS-CoV-2-specific NAbs at the convalescent phase of infection. The titers of NAbs reached their peak at 10 to 15 days after disease onset and remained stable thereafter in patients. Antibodies targeting on different domains of S protein, including S1, RBD and S2, may all contribute to the neutralization.
Conserved epitopes may exist between SARS-CoV-2 and SARS-CoV since they share 77.2% identical amino acids in their spike proteins.
Few reports have demonstrated that SARS-CoV-specific monoclonal NAbs could cross-neutralize SARS-CoV-2 PsV infection, 3,11,18 Even though plasma from COVID-19 patients showed cross-binding to SARS-Cov, they did not neutralize SARS-CoV, indicating that the antigenicity of SARS-CoV-2 is different from that of SARS-CoV. Evidence deduced from this study only suggested that cross-neutralizing antibodies targeted the conserved epitopes of SARS-CoV and SARS-CoV-2 may not be easily elicited during the infection of COVID-19, making this a potential line of advanced study. It is also noteworthy that the levels of NAbs in patients were variable.
About 30% of patients failed to develop high titers of NAbs after COVID-19 infection. However, the disease duration of these patients compared to others was similar. Notably, there were ten recovered patients whose NAb titers were very low, under the detectable level of this study (ID50: <40), suggesting that other immune responses, including T cells or cytokines, may contribute to the recovery of these patients. Whether these patients were at high risk of rebound or reinfection should be explored in further studies. On the other hand, two patients had very high titer of NAbs, which were over ID50: 15989 and 21567 respectively, but did not show any antibody-related adverse reactions.
The NAbs titers in patients were also observed to be correlated with the age of the patients. Elderly patients had significantly higher titers of NAbs than younger patients. Age has been reported as an important predictor of adverse disease outcome after infection with coronavirus, including SARS-CoV 20 , MERS-CoV 21 and SARS-CoV2 12. Previous studies in SARS-CoV-infected macaques revealed that aged macaques induced elevated innate immune response, resulting in more severe pathology than young adult macaques 22.
The elderly patients in this cohort also had higher blood CRP level and lower lymphocyte counts at the time of admission, indicating the induction of stronger innate immune response than younger patients. High level of NAbs may be a result of strong immune response in these elderly patients. Whether the high level of NAbs protect these patients from progression into severe and critical conditions is worthy of comprehensive evaluation. Further study of the immunological characteristics of COVID-19 patients may reveal key determinants in the generation of NAbs and effective cell-mediated immune responses, which is important for the development of an effective vaccine against SARS-CoV-2 virus.
This study is preliminary and has several limitations. First, viral RNA was not detectable in patients’ blood. Owing to the lack of respiratory specimens, informationabout the kinetics of viral loads was not available. Second, patients in severe and critical condition were excluded from the study because they received passive antibody treatment before sample collection. Thus, we were not able to directly evaluate the effect of NAbs on virus clearance or disease progression of COVID-19 patients in this study. A further comprehensive study should be made to address the question.
To the best of our knowledge, this is the first report about NAbs drawn from the plasma of a COVID-19 recovered patient cohort, potentially providing useful information for passive antibody therapy and vaccine development against SARS-CoV-2 virus. The highly variable levels of NAbs in the patients of COVID-19 indicated that convalescent plasma and serum from recovered donors should be titrated before use in passive antibody therapy, an easy task that can be performed using the PsV neutralization assay. Correlation of NAbs titers with the age, lymphocyte counts and blood CRP levels ofpatients also lays the groundwork for further study to explore the mechanism of NAbs development in COVID-19 patients"
