Fig. 3.

The addition of Matrix-M™ induces HAI responses against a heterologous influenza B strain but not against heterologous H1N1 and H3N2 strains. a Mice (n = 7-8/group) were immunized with TVV (−) containing 3μg HA per strain or TVV + MM (+). Three weeks later, serum samples were obtained and tested for HAI responses against H1N1 A/Brisbane/59/07 and H3N2 A/Hong Kong/1/68 and B/Florida/04/06 (B/Yamagata lineage). Black bars indicate medians of log₂ transformed titers (*p < 0.05, **p < 0.01, ***p < 0.001 compared to the vehicle control group (PBS) using Wilcoxon’s rank-sum test adjusted for multiple comparisons). Comparisons between one and two immunizations and between immunizations with TVV and TVV + MM are summarized in Additional file 1: Table S1. b Numbers indicate HA homology as percentages of amino acid similarity (difference indicated in red) of the HA head region and of the whole HA sequence between vaccine strains and the assay virus strains (alignment of full length HA’s in Additional file 4: Figure S3, Additional file 5: Figure S4, Additional file 6: Figure S5). H1/Cal = A/California/07/09. H1/Bris = A/Brisbane/59/07. H3/Vic = A/Victoria/210/09. H3/HK = A/Hong Kong/1/68. B/Bris = B/Brisbane/60/08. B/Florida = B/Florida/04/06