Abstract:
The Coronavirus disease 19 (COVID-19) pandemic has kept the world on tenter- hooks for over a year. At the beginning of our work (by March 2020), very little was known about the new virus. No commercial antibody screening test was available yet. The aim of this doctoral thesis was to establish a Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) antibody test at the In- stitute for Tropical Medicine in Tübingen, which was then used to explore, whether there is a correlation of symptoms and antibody levels and which factors additional to a RT-PCR positive test predict antibody positivity.
For this purpose, an immunoglobulin G (IgG) and an immunoglobulin A (IgA) SARS-CoV2-RBD ELISA were developed and evaluated by comparing it to com- mercial tests. For the statistical analysis of IgG antibody levels, blood was drawn from 131 subjects with COVID-19 disease and a Case Report Form was admin- istered.
The IgG ELISA outperformed commercial tests in comparison with a sensitivity of 84.3% and a specificity of 100% related to 83 RT-PCR-positive samples of the TüCoV study and 66 negative samples. The IgA ELISA reached 47.6% and 96.8% in sensitivity and specificity respectively. We have found that the symp- toms of fever and loss of taste correlated positively with the level of antibody titers. Moreover, we found taste loss to be a factor additionally to RT-PCR posi- tivity that increased the probability of seroconversion 4.3-fold, as about one quar- ter of the RT-PCR-confirmed infected test persons did not develop detectable antibodies at all. Thus, fever and especially loss of taste may be predictors for a stable immunity.
It would be interesting to verify in further studies whether the results regarding the combination of RT-PCR positivity and taste disturbance as a predictor for seropositivity can be reproduced in other cohorts with more subjects. Regarding the developed assays, further testing, such as measuring samples with known concentrations of specific antibodies, would be useful to verify the accuracy of the measured concentrations.
