Fig. 4: Protective capacity of the 1968 A(H3N2) pandemic N2 antibody against subtype A(H9N2) AIV infection. | Nature Communications

Fig. 4: Protective capacity of the 1968 A(H3N2) pandemic N2 antibody against subtype A(H9N2) AIV infection.

From: A(H2N2) and A(H3N2) influenza pandemics elicited durable cross-reactive and protective antibodies against avian N2 neuraminidases

Fig. 4

a Experimental schema of (i) prime-challenge and (ii) passive transfer experiment. Groups of mice (for i; n = 11/group, for (ii); n = 14/group for immunization, n = 10/group, except n = 8 for rgH6N2-SG16 group, for challenge) were immunized with two-doses of recombinant H6Nx viruses bearing the NA from A/Aichi/2/1968 (H3N2) (AI68), A/Singapore/INFIMH160019/2016 (H3N2) (SG16), or A/Michigan/45/2015 (H1N1) (MI15), or wild-type (wt) A/chicken/Zhejiang/198/2019 (H9N2) (ZJ19). From experiment (i), b hemagglutination-inhibition (HI) and neuraminidase inhibition (NI) antibody profiles at Day 42 post-immunization against priming strain. c NI antibody profiles and d its associated fold change against priming viruses before and after challenge with ZJ19 at Day 72. From experiment (ii), e weight loss and f survival of mice that received pooled immune sera after being challenged with ZJ19. NI-antibody was detected by enzyme-linked lectin assay (ELLA) using recombinant viruses bearing the target NA with a HA gene from A/teal/Hong Kong/W312/1997 (H6N1) and the internal genes of A/Puerto Rico/8/1934 (H1N1) (PR8). Dotted lines in (b) and (c) indicate limits of detection. The bar graphs indicate the geometric mean antibody titer with 95% confidence intervals. Statistical significance in (b) was calculated using two-sided one-way ANOVA using rgH6N2-AI68 group as reference, adjusted with Dunnett’s multiple comparison test (in HI assay, ****p < 0.0001 for H9N2-ZJ19; in NI assay, ****p < 0.0001 for rgH6N1-MI15). Statistical significance in (c) was analyzed using two-sided paired t-test (**p = 0.0086 for H9N2-ZJ19, ***p = 0.0006 for rgH6N2-AI68). Weight loss in (e) was expressed as mean ± standard deviation, with statistical difference compared to the PBS group using two-sided, adjusted with Dunnett’s multiple comparison test from days 0 to 7 post-inoculation (days 2 *p = 0.0047 for rgH6N2-AI68; days 3 *p = 0.0106 for H9N2-ZJ19, **p = 0.0026 for rgH6N2-AI68; days 4, *p = 0.0467 for rgH6N2-AI68, ****p < 0.0001 for H9N2-ZJ19; days 5 *p = 0.0411 for rgH6N2-SG16, *p = 0.0239 rgH6N1-MI15, ****p < 0.0001 for H9N2-ZJ19; days 6, ****p < 0.0001 for H9N2-ZJ19; days 7, *p = 0.0213 for rgH6N1-MI15, ****p < 0.0001 for H9N2-ZJ19). Survival rate in (f) was compared to PBS group using two-sided Gehan-Breslow-Wilcoxon test (*p = 0.0128 for rgH6N2-AI68, *p = 0.0411 for rgH6N1-MI15, ***p = 0.0005 for H9N2-ZJ19). Figure 4a created with BioRender.com released under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International license.

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