Fig 4. Spike-specific Ig levels in the saliva of newly positive, asymptomatic individuals at the time of PCR testing.
Saliva samples from individuals who were newly positive (NewPOS, PCR positive for the first time ever) for either the CoV2US (n = 16), CoV2Alpha (n = 15), CoV2Gamma (n = 21), or CoV2Delta (n = 36) lineage were used to measure the concentrations of (A) IgMSpike, (B) IgASpike and (C) IgGSpike. The CoV2Anc Spike was used as the capture antigen in each case, and concentrations are expressed as World Health Organization (WHO) binding antibody units (BAU) per mL. PCRNEG saliva collected in early 2020, from healthy individuals living in the US with no COVID history, was tested in the same manner used to estimate “pre-pandemic” levels of IgMSpike, IgASpike and IgGSpike binding, which are represented by the dashed lines on each graph. X, values that were considered outliers but are nevertheless shown for completeness and are included in all statistical group comparisons. * p≤ 0.05, as determined by unpaired Wilcoxon tests with Benjamini-Hochberg adjustment. The dilution adjusted lower limit of quantification for each isotype were as follows (LLOQ values in WHO BAU/mL): IgMSpike, 0.026691; IgASpike, 0.38378; IgGSpike, 0.044149.