Kinetics of antibody response to Coxiella burnetii infection (Q fever): Estimation of the seroresponse onset from antibody levels

• The study provides insight into the dynamics of a Coxiella burnetii infection.
• Analysing antibody response kinetics enables estimation of the seroresponse onset.
• The time to onset seroresponse is extremely variable among individuals.
• Acute and past-resolved Q fever can be distinguished in post-epidemic/endemic areas.
• The tool can estimate the Q fever outbreak/epidemic onset based on serologic data.

BackgroundFrom 2007 to 2009, the Netherlands experienced a major Q fever epidemic. Long-term serological follow-up of acute Q fever patients enabled the investigation of longitudinal antibody responses and estimating the onset of the seroresponse in individual patients.MethodsAll available IgG and IgM phase I and II antibody measurements determined by immunofluorescence assay at month 3, 6, 12, and 48 from 2321 acute Q fever patients were retrospectively analyzed. Characteristic features of the antibody response were calculated. To model the seroresponse onset, serological data from patients diagnosed with a positive C. burnetii PCR test (n = 364), and therefore with a known time of infection, were used as reference.ResultsIn 9083 IgG samples and 3260 IgM samples large heterogeneity in shape and magnitude of antibody responses was observed. Phase II reached higher levels than phase I, and IgG antibodies were more persistent than IgM. The estimated seroresponse latency allowed for determining the time since start of the seroresponse from the concentrations of the different antibodies against C. burnetii.ConclusionsThe extraordinary large serological dataset provides new insight into the kinetics of the immunoglobulins against C. burnetii antigens. This knowledge is useful for seroprevalence studies and helps to better understand infection dynamics.