A bead-based multiplex assay covering all coronaviruses pathogenic for humans for sensitive and specific surveillance of SARS-CoV-2 humoral immunity

Serological assays measuring antibodies against SARS-CoV-2 are key to describe the epidemiology, pathobiology or induction of immunity after infection or vaccination. Of those, multiplex assays targeting multiple antigens are especially helpful as closely related coronaviruses or other antigens can be analysed simultaneously from small sample volumes, hereby shedding light on patterns in the immune response that would otherwise remain undetected. We established a bead-based 17-plex assay detecting antibodies targeting antigens from all coronaviruses pathogenic for humans: SARS-CoV-2, SARS-CoV, MERS-CoV, HCoV strains 229E, OC43, HKU1, and NL63. The assay was validated against five commercial serological immunoassays, a commercial surrogate virus neutralisation test, and a virus neutralisation assay, all targeting SARS-CoV-2. It was found to be highly versatile as shown by antibody detection from both serum and dried blot spots and as shown in three case studies. First, we followed seroconversion for all four endemic HCoV strains and SARS-CoV-2 in an outbreak study in day-care centres for children. Second, we were able to link a more severe clinical course to a stronger IgG response with this 17-plex-assay, which was IgG1 and IgG3 dominated. Finally, our assay was able to discriminate recent from previous SARS-CoV-2 infections by calculating the IgG/IgM ratio on the N antigen targeting antibodies. In conclusion, due to the comprehensive method comparison, thorough validation, and the proven versatility, our multiplex assay is a valuable tool for studies on coronavirus serology.

Seroepidemiological study on the spread of SARS-CoV-2 in Germany: Study protocol of the CORONA-MONITORING bundesweit' study (RKI-SOEP study)

The SARS-CoV-2 coronavirus has spread rapidly across Germany. Infections are likely to be under-recorded in the notification data from local health authorities on laboratory-confirmed cases since SARS-CoV-2 infections can proceed with few symptoms and then often remain undetected. Seroepidemiological studies allow the estimation of the proportion in the population that has been infected with SARS-CoV-2 (seroprevalence) as well as the extent of undetected infections. The ‘CORONA-MONITORING bundesweit’ study (RKI-SOEP study) collects biospecimens and interview data in a nationwide population sample drawn from the German Socio-Economic Panel (SOEP).

Participants are sent materials to self-collect a dry blood sample of capillary blood from their finger and a swab sample from their mouth and nose, as well as a questionnaire. The samples returned are tested for SARS-CoV-2 IgG antibodies and SARS-CoV-2 RNA to identify past or present infections.

The methods applied enable the identification of SARS-CoV-2 infections, including those that previously went undetected. In addition, by linking the data collected with available SOEP data, the study has the potential to investigate social and health-related differences in infection status. Thus, the study contributes to an improved understanding of the extent of the epidemic in Germany, as well as identification of target groups for infection protection.

Spot urine iodine levels below the WHO recommendation are not related to impaired thyroid function in healthy children and adolescents

PURPOSE

Iodine deficiency in childhood and adolescence may lead to later thyroid dysfunction, stunted growth and cognitive impairment. The World Health Organization (WHO) has issued recommended age-dependent urine iodine concentration targets, but a critical threshold beyond which clinical sequelae are to be expected remains undefined. Our study aimed to investigate spot urine iodine concentration in a typical Central European cohort of children and adolescents, and consider the implications of these values in regard to laboratory parameters for evaluating thyroid function.

METHODS

Using the Sandell-Kolthoff method, spot urine iodine concentration was measured cross-sectionally from 1802 healthy children and adolescent in the age range of 0.25-18 years within the LIFE-Child epidemiological study based in and around the city of Leipzig (Germany). Additionally, serum thyroid biomarkers of these subjects were measured and correlated to urine iodine levels.

RESULTS

In our cohort, 61.39% of boys and 65.91% of girls had an iodine level of < 100 µg/L (57%, 67%, 65% of the age groups 0-5, 6-12 and 13-18 years), the median iodine excretion was 86 µg/L in boys and 80 µg/L in girls. The iodine levels revealed no significant correlation with the thyroid biomarkers TSH, FT4 and FT3. Moreover, iodine values revealed no correlation with levels of antibodies against thyroid peroxidase or thyroglobulin.

CONCLUSION

In our cohort of children and adolescents, the relatively high number of iodine levels below the WHO recommendation appears not to be related to clinical or subclinical thyroid diseases in the respective participants.