Figure 5.

Vaccine elicited HA and NA specific antibodies predict in vivo protection after challenge. (A, B) Hemagglutination inhibition antibodies (HI titer, far left), HA specific neutralizing antibodies (PN titer, central left), total HA stalk specific antibodies (HA stalk IgG, central right), and neuraminidase enzymatic activity inhibiting antibodies (NI titer, far right) significantly and inversely correlate with the maximum body weight loss (A) and lung viral load (B) in mice after NIBRG-14 virus challenge. Each symbol represents one mouse (A, B). The linear fitting curve is plotted as line. Pearson r and P values are noted in each correlation. (C, D) Antibody parameters including HI titer, PN titer, HA stalk IgG and NI titer results were used to predict mice maximum body weight loss (C) and lung viral load (D) in uni- and multiple linear regression models. Adjusted R square (left half) and Standard Error of the Estimate (right half) are shown to indicate the goodness of different models explaining dependent variables. In each model, predictors contributing significantly are noted. *P < 0.05, **P < 0.01. For detailed model summary and coefficients, see Supplementary Tables 2–3 . Antibody parameters from each individual subject in clinical trial were put together in silico the same way as sera were combined to make group-and-time-point-wise pooled human sera for mice passive transfer. Geometric mean of antibody parameter was calculated, Ln transformed and centered before being used as independent variables. Maximum body weight loss and Ln-transformed lung viral load were used as dependent variables in regression analyses in SPSS 25.