Laboratory methods for investigation of the immunological orchestra in response to pathogens

Abstract: Laboratory methods used for investigation of immune response often involve collection of whole blood and analysis of different biomarkers in blood components or generated from pathogen stimulation of whole blood or peripheral blood mononuclear cells (PBMC). Methods used to measure biomarkers are for example enzyme-linked immunosorbent assay (ELISA) which measures one biomarker at a time or multiplex assays for example x-unknown, multi-analyte profiling (xMAP) by Luminex or proximity extension assay (PEA), which can measure up to just over 3000 biomarkers at a time. Analysis of one biomarker at a time are time consuming, costly, and dependent of a large sample size to enable repeated measurements of different analytes. Therefore, multiplex assays that are time saving, more cost effective and measures multiple bi-omarkers at once in a small sample can be applied.   The aim of this thesis was to evaluate multiplex laboratory methods for investigation of the immunological orchestra in response to Borrelia infection and influenza immunisation and if possible, further characterize individuals with different clinical outcomes or serological response, respectively.  In our studies (paper I-III) we included 1113 blood donors of which 66 were found to previously have had a subclinical borreliosis (defined as presence of Borrelia-specific antibodies without recall of previous Lyme borreliosis), of the 66 individuals 60 were available for participation. We also included 22 patients previously diagnosed with Lyme neuroborreliosis (LNB). In paper IV we included in total 73 individuals consisting of healthcare workers and patients attending seasonal influenza vaccination. We applied whole blood, PBMC and plasma stimulations and measured a range of cytokines, chemokines and complement factors with ELISA, nephelometry, xMAP and PEA.   Our results show that subclinical Lyme borreliosis (SB) individuals display the following pattern, low age, male sex, low amount of secreted interleukin (IL)-17, CCL20 and higher secretion of IL-10 by PBMCs stimulated three days with Borrelia garinii compared to patients with previous Lyme neuroborreliosis (LNB). The subclinical individuals also show higher activation of the complement system in response to Borrelia afzelii.   We performed multiplex analysis of complement factors in attempt to further characterize our SB individuals and LNB patient but found the results to deviate largely from reference values retrieved with other standardized methods. This highlights the importance of critical review of generated results from all form of assays. To investigate immune responses after influenza immunisation and further characterize serological responders and nonresponders we included measurement of influenza-specific antibodies and total immunoglobulins (Ig) in blood serum, influenza-specific mucosal IgA (nasal-swabs) and cell-mediated immune response in supernatants from PBMCs stimulated with influenza vaccine using PEA. We found the serological responders to be characterised by lower levels of total IgM, Granzyme B (GZMB) and IL-12 together with higher levels of CXCL13 compared with nonresponders. To conclude, xMAP and PEA are two valuable methods that can be applied together with multivariate statistical methods in the investigation of both innate and adaptive immunity characteristics and association to clinical outcome or serological response after Borrelia infection and influenza immunisation, respectively.