Figure 1. Experimental design.

Eight mice per immunization protocol were equipped with telemetric transmitters for real-time, long-term recording of heart rate, interbeat interval, heart rate variability (standard deviation of interbeat interval), body core temperature and locomotor activity. Simultaneous clinical scoring included body weight measurements, as well as food and water consumption. Measurements were conducted over a period of four days (grey), the first of which served as individual baseline. Antibody responses were determined in serum samples collected two weeks after primary and booster immunization, respectively (triangles). Twenty-two mice without transmitter were treated analogously and were sacrificed for gross pathology of abdominal organs and blinded histological analysis of intestine, omentum, abdominal wall, and liver at three days after primary and booster immunization (arrows), respectively.