Abstract: Lyme disease (LD) leads to lifelong health problems if standard antibiotic therapy is not initiated during the first 2-3 weeks after infection. Diagnosis for LD currently relies on seroconversion and is unreliable during acute disease. Cases of suspected acute LD should be confirmed using clinical diagnostic assays. N- linked glycosylation is one of the most abundant post-translational modifications of serum proteins. While it is dynamic in nature, it is also highly consistent in a healthy state. N-linked glycosylation of serum immunoglobulins (Igs) are known to change in a disease specific manner and can direct the host immune response toward a pro- or an anti-inflammatory response. We previously observed that Ig N-glycans produced during acute LD contain specific alterations in the abidance of galactose and sialic acid. We hypothesize that these Ig alterations are antigen-specific, and that the glycosylation patterns present will negatively impact downstream immune responses. This hypothesis is based on our preliminary data, known LD B-cell perturbations, and reports of IgG N-glycans altering the immune response to COVID-19, tuberculosis, multiple sclerosis, and HIV. This proposal is novel and unique because it is the only study that examines the role of glycosylation during the human immune response to LD. This proposal is built on our preliminary work where we identified aberrant glycosylation on the total serum IgG and IgM in acute LD patients prior to seroconversion. In this proposal, we examine the glycosylation of Igs specific to LD antigens and determine if acute LD infection will alter B-cell responses to produce antigen specific Igs with the same unique glycosylation changes seen in our preliminary data. Additionally, we examine how the glycosylation pattern on antigen specific Igs effect the immune response to LD. In Aim 1, we isolate Igs specific to the LD antigen VlsE and establish the IgG and IgM N-glycan profiles. The result will determine if antigen specific Igs contain the same aberrant glycosylation found in the total Ig population of acute LD patients. In Aim 2, we quantify the impact of LD antigen-specific IgG glycosylation on the promotion of ADCC and complement deposition. The result will determine if there is a link between IgG glycosylation and the inability of the patients to clear the Borrelia burgdorferi spirochete that causes LD. In Aim 3, we quantify the impact of antigen-specific IgM glycosylation on the complement deposition rate. Complement deposition leads to rapid clearance of Lyme disease pathogens. Altered glycosylation of IgM could impair complement deposition and impede the ability of the human host to clear the infection. This work will establish a new mechanism of Borrelial immune evasion, characterize the host-response to LD pathogenesis in humans. Additionally, the results will potentiate the use of Ig N-glycans to serve as multiplexed biomarkers in a novel Lyme disease diagnostic assay and ...