Figure 3
Serum NAI antibody titers after vaccinations in mice. Immunologically naïve DBA/2J mice were vaccinated intramuscularly (i.m.) three times at four-week intervals with quadrivalent (green) or heptavalent (blue) formulations of COBRA recombinant HA and NA proteins, with AddaVax™ as adjuvant. Sera collected two weeks after final vaccination were used for NAI assay against (a, b) N1 and (c, d) N2. Sera were diluted two-fold from starting dilution of 1:20 to quantify NAI titer (a, c). Non-linear regression was conducted from these results to obtain reciprocal titer that inhibited 50% of the NA activity (b, d). Statistical differences between NAI50 titers were analyzed by unpaired t-tests by GraphPad Prism 9 software (GraphPad, San Diego, CA, USA). A p value of less than 0.05 was defined as statistically significant (*, p < 0.05; **, p < 0.01; ***, p < 0.001; ****, p < 0.0001).
