High Affinity Antibodies against Influenza Characterize the Plasmablast Response in SLE Patients After Vaccination
(A) Monoclonal antibodies generated from plasmablasts isolated from subjects were tested for virus binding by ELISA. Binding avidities (KD) were estimated by Scatchard plot analyses of ELISA data. KD values of pooled antibodies are shown. Medians were compared using Mann-Whitney test. (B) The distribution of KD values is shown by subject. Each bar graph represents the median of the avidities of antibodies (represented by symbol) for each subject. The red dotted line represents the global median avidity of all SLE and control influenza-positive antibodies. (C) Avidities of 53 influenza-positive antibodies from SLE patients and 27 from controls were measured by SPR. Correlation between approximated KD values from virus ELISA data and KD values measured by SPR is shown. Black symbols are antibodies from SLE patients while blue are those from controls. Correlation was determined by Spearman’s correlation test. (D-E) Influenza-positive antibodies were serially diluted and tested in the standard HAI assay (D) and microneutralization (E) for functional capability. Medians were compared using Mann-Whitney test. (D) Minimum antibody concentration effective at inhibiting hemagglutination is plotted for each HAI-positive antibody. (E) Same as (D), except for microneutralization. Results are representative of at least three independent replicates.