FIG 3.

Induction of IgG antibodies and protective efficacy are dependent upon MyD88 expression in bone marrow-derived and radioresistant cells. (A) BM chimeric mice, including Myd88^{WT BM} (n = 23), WT^{Myd88 BM} (n = 21), WT^{WT BM} (n = 24), and Myd88^{Myd88 BM} (n = 10) mice, were immunized with 1V270/1Z105-adjuvanted rPR/8 HA protein at days 0 and 14 and bled on day 35; sera were assayed for total IgG in an ELISA with PR/8 virus substrate. The data shown are pooled from two independent experiments. Bone marrow chimeric mice were challenged with 10 mLD₅₀ of PR/8 virus on day 36 after the first immunization and assayed for morbidity (B), measured by body weight loss, and mortality (C) for each of the following BM chimeric groups: Myd88^{WT BM} (n = 9), WT^{Myd88 BM} (n = 8), WT^{WT BM} (n = 15), and Myd88^{Myd88 BM} (n = 5). Significant differences in body weights compared to the WT^{WT BM} mice are indicated by the asterisk colors. (D) The IgG endpoint titer was plotted against the minimum percentage of initial body weight lost for each animal, and the Pearson correlation coefficient (r) and linear regression line are included. Statistical significance for IgG endpoint titers was assessed by the Kruskal-Wallis test. Statistical significance of weight loss was assessed by t tests adjusted for multiple comparisons. Statistical significance of survival was assessed by the Mantel-Cox test to compare WT mice receiving adjuvanted immunizations, as indicated. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.