Degree of immunoglobulin kappa light chain glycosylation of anti-spike SARS CoV-2 antibodies correlates with COVID-19 severity

Abstract

Glycosylation of antibodies and the effects this has on inflammatory responses has concentrated predominately on the study of glycosylation moieties found in the Fc region of heavy chains. Light chain glycosylation and their ratios are relatively understudied. Nevertheless, variable glycosylation and ratio of κ and λ light chains have been associated with worse prognosis in myeloma and in tissue deposition – amyloidosis.The κ & λ light chains, of antibodies binding to SARS-CoV2 nucleocapsid and spike protein were analysed, using MALDI-ToF MS, in respect to their intensity, ratios, glycosylation patterns and any pattern changes correlating with COVID-19 severity. The molecular masses and signal intensity of κ and λ glycosylated and non-glycosylated light chains were measured for immunoglobulins isolated from plasma of sero-positive and sero-negative health care workers (HCW), and convalescent patients who had suffered from acute respiratory distress syndrome (ARDS).Overall, there was no significant changes in κ to λ ratio of total IgG (via protein G capture) antibodies between the groups. A non-statistically significant trend towards λ light chains was found in antibodies against SARS CoV-2 Nucleocapsid and Spike proteins. However, detailed analysis of the molecular forms found a significant increase and bias towards un-glycosylated light chains and in particular un-glycosylated κ light chains, in antibodies against SAR-CoV-2 spike protein, from convalescent COVID-ARDS patients.Here we have demonstrated a bias towards un-glycosylated κ chains in anti-spike antibodies in those who suffered from ARDS as a result of SARS-CoV2 infection 3 months after recovery. How this relates to the immunopathology of COVID-19 requires further study.

The COVID-19 antibody responses, isotypes and glycosylation: Why SARS-CoV-2 Spike protein complex binding of IgG3 is potentiated in some and immuno-pathologies manifest

“…We have previous reported our findings concerning the mass spectral analysis of heavy chain and light chain of anti SARS CoV-2 nucleocapsid and Spike antibodies; and also the unusual finding of AGE glycated human serum albumin (HSA) binding by Spike protein [13][14][15][16][17] Here the complete mass spectral data of light and heavy chain analysis is presented together on the same samples and cross correlated. Patients (n = 38 samples) [34].…”

“…To reconcile this disparity my research team and collaborators, have been looking at the molecular composition of the antibody response in people who did suffer COVID-19 ARDS and those who did not develop COVID-19, despite being at high risk of exposure, or developed only mild symptoms post infection. This was achieved by coupling SARS-CoV-2 nucleocapsid and prefusion conformation Spike proteins to magnetic beads, capturing any bound antibodies and characterising them by MALDI-ToF mass spectrometry (14,15,17).…”

“…Fortunately, the majority of immunoglobulin chains have different molecular masses and we were able to identify and characterise these form a minimal patient sample in a single analysis by highly sensitive MALDI-ToF Mass spectrometry [13,14,15,16,17].…”

“…We have previous reported our findings concerning the mass spectral analysis of heavy chain and light chain of anti SARS CoV-2 nucleocapsid and Spike antibodies; and also the unusual finding of AGE glycated human serum albumin (HSA) binding by Spike protein [13-17]…”

“…57,500m/z, Igα2 at 55,500-56,100m/z, Igε at 63,400-63,700 and Igμ at 74,200-75,100m/z[13][14][15][16][17].After deconvolution of doubly charged peak masses, contaminating human serum albumin were identified and had been characterised previously as a higher molecular mass glycated AGE (advanced glycation End products) form, strongly binding to Spike protein. Peaks arising from HSA were not considered in this reported data analysis of immunoglobulins.…”