Fig. 2: Intranasal immunization with NVT-adjuvanted H3N2 confers cross-protection against lethal heterosubtypic influenza virus challenge. | Nature Communications

Fig. 2: Intranasal immunization with NVT-adjuvanted H3N2 confers cross-protection against lethal heterosubtypic influenza virus challenge.

From: A vaccine platform targeting lung-resident memory CD4+ T-cells provides protection against heterosubtypic influenza infections in mice and ferrets

Fig. 2

a Experimental design. BALB/c mice (n = 25 per group) were immunized i.m. with H3N2 or i.n. with H3N2 + NVT twice at two-week intervals. Two weeks after the last immunization, immune response analysis (n = 5 per group) (b, c) and H1N1 virus (A/Korea/2785/2009) challenge (n = 20 per group) (d–f) were performed. Schematic image was created in BioRender. Han, S. (2024) BioRender.com/b04n737. b HAI antibody titers against H3N2 or H1N1 in serum, nasal wash, and BALF were measured via HAI assay. An HAI antibody titer of 1:40 (red dotted line) was considered protective against influenza infection. The data are expressed as dot plots, with horizontal lines representing the medians. c After stimulating lung and spleen cells with H1N1 or H3N2, the IFN-γ+CD4+ T-cell response was determined by flow cytometry. d–f The vaccinated mice were infected i.n. with 4 LD50 of H1N1 virus. d Body weight and survival (n = 5 per group) were monitored daily. Weight-loss data are shown as mean value ± SD. Survival data are represented as Kaplan‒Meier survival curves, and the significant differences in survival rates were calculated by the log-rank test. e On days 3 and 6 after the challenge, lung viral loads were assessed using a plaque assay (n = 5 per group). f On day 6 after the challenge, lung tissues from mice (n = 5 per group) were collected, and histological sections of vaccinated and control (naïve) mice were stained with hematoxylin and eosin. Acute lung injury (ALI) scores of sectioned lungs. A score of zero indicates healthy lungs, whereas a score of one signifies severe acute lung injury. c, e, f Box and whisker plots show the median (center), 25th and 75th percentiles (box), and lowest and highest values (whiskers). b–f Statistical analyses were performed using one-way ANOVA with Tukey’s multiple comparisons test or two-sided Mann–Whitney U test. This study was performed independently at least three times, and one representative set is shown. BW body weight, N.D. not detected, ns not significant, NT non-treated. Source data are provided as a Source Data file.

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