Age-related impairment of adaptive immune response to CHIKV.

<p>(A) Popliteal LNs collected and quantified from either naïve or CHIKV-infected A and O mice at day 3, 7, or 9 post-infection. The LN draining from the CHIKV-inoculated foot is indicated as dLN and from the non-inoculated foot as ndLN. Table under graph indicates the average fold-increase from naïve for each age in either the dLN or ndLN (<i>n</i> = 6–8 per group). Horizontal lines indicate the median. Statistical significance determined by student’s <i>t</i>-test. (B-C) Lymphocytes from popliteal LNs on d7 post-infection were stimulated with CHIKV peptides in the presence of protein transport inhibitor. Total number of IFNγ⁺ CD4 T cells (B) and frequency (C) for each age. Data are mean ± SEM (<i>n</i> = 10 per group). Statistical significance determined by unpaired Student’s <i>t</i>-test. (D) CHIKV-specific IgM and (E) IgG2c in serum determined by ELISA at the indicated day post-infection. Data are mean (<i>n</i> = 4–24 per group). Statistical significance was determined by two-way ANOVA with Bonferroni post-test. (F) Plaque reduction neutralizing test on serum from days 9 and 60 post-infection. Data are mean + SEM (<i>n</i> = 12 per group). Statistical significance was determined by two-way ANOVA with Bonferroni post-test. (G) Serum samples collected from patients experiencing acute CHIKV-disease were evaluated by plaque reduction neutralizing test. Data are mean + SEM (<i>n</i> = 24 young and 15 aged). Statistical significance was evaluated by unpaired student’s <i>t</i>-test. In all panels black indicates A, red indicates O; * <i>P</i>< 0.05; ** <i>P</i>< 0.01; *** <i>P</i>< 0.001.