Tanja C. Meyer

• Staphylococcus aureus (S. aureus) is a Gram-positive bacterium known to colonize parts of the human population persistently at various niches on the body surface, with the nares as main area of colonization [Wertheim 2004]. In a 19-month longitudinal study at the Statens Serum Institut in 1995, different modes of colonization were described: 14.4% of the 104 persons investigated were characterized as persistent carriers showing detectable amounts of S. aureus in over 90% of swabs, 16.3% as intermittent carriers (over 50% of swabs positive for S. aureus), 52.9% as occasional carriers (over 10% of swabs positive) and 16.3% as non-carriers with not a single culture-positive swab [Eriksen 1995]. With the introduction of more sensitive culture-independent detection technologies, the separation of groups was rephrased in 2009 by van Belkum et al.: only two groups, namely persistent colonization and intermittent carriage should remain due to similar responses of intermittent carriers and non-carriers to artificial inoculation [van Belkum 2009]. Colonization itself can remain unnoticed since no clinical symptoms are triggered, but due to the constant challenge with the bacterium, an increased risk of surgical site infections (SSIs) was described in persistent carriers [Kluytmans 1995]. Additionally, invasive events occur more often, when staphylococci are able to enter the organism e. g. via micro-lesions in the skin [Wertheim 2004]. Due to the persistent challenge in carriers, it was hypothesized that these individuals should reflect these circumstances with higher titers of anti-staphylococcal antibodies together with matching B- and T-cells primed to staphylococcal antigens [Wertheim 2004, Holtfreter 2006]. This idea was addressed in multiple small case-control studies [Verkaik 2009, Dryla 2005, Rigat 2019], but the bigger picture studying the general population was still missing. The work described in this dissertation focuses on the detection of specific antibodies against a set of 79 staphylococcal antigens in a multiplex bead-based assay format to describe the anti-staphylococcal antibody repertoire in a study population resembling the general population. To achieve this goal, a highly sensitive analysis strategy was designed which is described in the first publication of this thesis “Technical report: xMAPr - High-dynamic-range (HDR) quantification of antigen-specific antibody binding”. This report addresses the challenge of measuring over the wide dynamic range expected in the plasma samples of the Study of Health in Pomerania (SHIP), of which the SHIP-TREND cohort was used as a population-based cohort for the second publication “A Comprehensive View on the Human Antibody Repertoire Against Staphylococcus aureus Antigens in the General Population”. The resulting antibody dataset was added to the multi-factor analyses of the SHIP-TREND cohort allowing a correlation of the individual anti-staphylococcal antibody response to the genetic features of the study subjects in a genome-wide association study (GWAS). The findings concerning one of the included antigens “toxic shock syndrome toxin 1” (TSST-1) are described in the third publication “Toxin exposure and HLA alleles determine serum antibody binding to toxic shock syndrome toxin 1 (TSST-1) of Staphylococcus aureus”. The xMAPr assay setup can be applied to further fields of research where a quantitative antibody detection is needed, e. g. the induction of specific antibodies after vaccination as shown in the fourth publication “Intranasal Vaccination With Lipoproteins Confers Protection Against Pneumococcal Colonisation”, where mice were immunized with antigens derived from Streptococcus pneumoniae.