Fig 4.
iPCR using recombinant antigens OspC and BmpA provided enhanced sensitivity for detection of both IgG and IgM isotypes in a murine model of infection. Magnetic beads coated with either purified recombinant GST-OspC (A) or GST-BmpA (B) protein were used to capture host response antibodies from preimmune (pre) or postimmune mouse sera collected over a time period of 21 days. IgM- and IgG-specific reporter antibody-DNA conjugates detected anti-B. burgdorferi antibodies captured by each set of antigen-coated beads. The IgM and IgG response to each antigen was determined for each mouse by multiplex quantitative PCR using distinct probes specific for the IgM- and IgG-specific DNA reporter molecules. The mean Cq background signal, determined using uninfected sera, plus 3 standard deviations was designated the call threshold for a positive detection event and indicated here as a ΔCq of 0. Data are shown as the Cq value for each sample minus the mean background Cq plus 3 standard deviations (ΔCq). Each data point represents the average of two mice, and the standard deviation between samples is shown.