Fig. 1. Functional and neutralizing antibody responses.

Haemagglutination inhibition, neuraminidase inhibition, and virus neutralization antibody titers detected during the course of the study in serum of ferrets that received either the split vaccines alone (45 µg HA—blue circles, 15 µg HA—red triangles) or the SWE-adjuvanted split vaccines (15 µg HA—green open circles, 7.5 µg HA—purple diamonds). HI-Titers were measured against four haemagglutinating units H7N9 (A/Anhui/1/2013) using a concentration of 1% horse erythrocytes. NI-titers were determined using an H6N9 (RN19/13-human reassortant strain) dilution with a neuraminidase activity resulting in an ~OD 1 after 1 hour incubation at 37 °C. Inhibition of neuraminidase was considered at an OD of less than three times standard deviation below the maximal OD. VN-titers were measured against 100 TCID₅₀ of H7N9 and 50% Virus neutralization was calculated according to Reed and Muench⁷⁰. Presented are the individual titers and a line connecting the geometric means. *p < 0.05; **p < 0.01, by the WMW test. Horizontal dotted line: detection limit. Vertical dotted lines indicate: a. 1st vaccination; b. blood collection; c. 2nd vaccination; d. challenge.