High Titers of Low Affinity Antibodies in COVID-19 Patients Are Associated With Disease Severity.

Background: Almost 2 years from the beginning of the coronavirus disease 2019 (COVID-19) pandemic, there is still a lot unknown how the humoral response affects disease progression. In this study, we investigated humoral antibody responses against specific SARS-CoV2 proteins, their strength of binding, and their relationship with COVID severity and clinical information. Furthermore, we studied the interactions of the specific receptor-binding domain (RBD) in more depth by characterizing specific antibody response to a peptide library. Materials and Methods: We measured specific antibodies of isotypes IgM, IgG, and IgA, as well as their binding strength against the SARS-CoV2 antigens RBD, NCP, S1, and S1S2 in sera of 76 COVID-19 patients using surface plasmon resonance imaging. In addition, these samples were analyzed using a peptide epitope mapping assay, which consists of a library of peptides originating from the RBD. Results: A positive association was observed between disease severity and IgG antibody titers against all SARS-CoV2 proteins and additionally for IgM and IgA antibodies directed against RBD. Interestingly, in contrast to the titer of antibodies, the binding strength went down with increasing disease severity. Within the critically ill patient group, a positive association with pulmonary embolism, d-dimer, and antibody titers was observed. Conclusion: In critically ill patients, antibody production is high, but affinity is low, and maturation is impaired. This may play a role in disease exacerbation and could be valuable as a prognostic marker for predicting severity.

Cumulative Incidence of SARS-CoV-2 in Healthcare Workers at a General Hospital in Germany during the Pandemic-A Longitudinal Analysis.

Health workers (HW) are at increased risk for SARS-CoV-2 infection. In order to monitor the infection dynamic on the basis of contact with patients, HW at the St. Antonius Hospital (SAH) were tested four times in one year by PCR and serology. The cumulative incidence of infection in HW was calculated. Swab and blood tests were simultaneously performed between April 2020 and April 2021. Risk factors and demographic information were assessed at the beginning of the study. The response rate was above 75% in all rounds of testing. The study comprised 1506 HW, 165 (10.6%) of which tested positive for SARS-CoV-2 infection. Working in an ICU or on wards with patient contact were risk factors (OR 4.4, 95% CI 1.73-13.6 and OR 2.9, 95% CI 1.27-8.49). At the end of the study, the majority of HW (810 of 1363 (59.4%)) had been vaccinated at least once. A total of 29.1% of unvaccinated HW and 5.3% of vaccinated HW showed an immune response typical for natural SARS-CoV-2 infection. Of the 73 HW who provided information on the course of the disease, 31.5% reported that their quality of life continued to be impaired. The cumulative incidence of infection was low in these HW, which may be attributed to vaccination and good hygiene. Nevertheless, a work-related infection risk was identified, highlighting the need to improve protection against infection. A high risk of developing long COVID was found after the infection has subsided. Special rehabilitation programs should be provided and HW should be compensated for reduced work capacity in the case that rehabilitation fails or takes a long time.

[Prevalence of SARS-CoV-2 in employees of a general hospital in Northrhine-Westphalia, Germany]. / Prävalenz von SARS-CoV-2 bei Mitarbeitern eines Krankenhauses der Regel-/Schwerpunktversorgung in Nordrhein-Westfalen.

BACKGROUND: We assessed the prevalence of SARS-CoV-2 in the staff of a general hospital in North-Rhine-Westphalia in a cross-sectional study. METHOD: Employees (n = 1363) were offered a nasopharyngeal swab and serology for SARS-CoV-2. Additionally, employees completed a questionnaire about preexisting conditions, contacts with SARS-CoV-2-positive individuals and COVID-19-specific symptoms. RESULTS: 1212 employees participated. 19 of 1363 (1.4 %) employees tested positive by PCR (3 within and 16 before the study). 40 (3.3 %) and 105 (8.6 %) had IgG and IgA, respectively, 32 (2.6 %) both IgG and IgA. Overall, 47 employees tested positive. In this group, most frequently reported symptoms were headache (56 %), fatigue (49 %), sore throat (49 %), and cough (46 %); fever was reported by 33 %. SARS-CoV-2-positive employees reported more frequently contact with COVID-19 cases (60.5 % vs. 37.3 %, p = 0.006). Employees testing positive only for IgA reported less symptoms. CONCLUSION: Between 27.04. and 20.05.2020, 3.9 % of the employees working in a general hospital were tested positive for SARS-CoV-2. This proportion was lower than expected; possible explanations are the low level of endemic infection and the extensive, uniform in-house preventative measures.