Trevani While, Chorny A, Salamone G, et al. immune-mediated safety. values less than 0.05 were considered statistically significant. RESULTS Reduction in vaccine-enhanced RSV disease is dependent on CAL-101 (GS-1101, Idelalisib) TLR specificity and timing of administration Mice were immunized with FI-RSV comprising CpG, TLR7/8 agonist, or both Statistically significant improvements in excess weight loss were observed when CpG was present during FI-RSV immunization, with either CpG only (Number 1A, p 0.05 relative to FI-RSV only settings on days 7-10 post-infection) or in combination with TLR7/8 agonist (days 5-10 post-infection). In contrast, TLR7/8 agonist alone had minimal effect. Administration of TLR agonists during RSV challenge of FI-RSV-immunized mice improved weight loss (Number 1B, p 0.05 CpG or TLR7/8 agonist alone relative to PBS-treated FI-RSV-immunized mice at days 3 and 4). Open in a separate window Number 1 Weight Loss Following RSV Challenge in FI-RSV-Immunized Mice Treated with TLR AgonistsPanel A C BALB/c mice CAL-101 (GS-1101, Idelalisib) were treated with the indicated TLR agonists during FI-RSV immunization. Six weeks later on the mice were challenged CAL-101 (GS-1101, Idelalisib) IN with live RSV and weighed days 0-12 after challenge. PML Data are displayed as the percentage of excess weight (in grams) relative to the base excess weight at day time 0 for n=6 mice per group inside a representative experiment (of 2). Panel B C BALB/c mice were immunized with FI-RSV IM and, six weeks later on, challenged with live RSV. Two days after challenge, the mice were treated with the indicated TLR agonist. Data symbolize base excess weight for n=6 mice per group from a single experiment. Panel C C Mice of the indicated strains were infected with live RSV IN. Two days after primary illness, the mice were treated with the indicated TLR agonist. Data symbolize base excess weight for n=5 mice per group from a single experiment CpG and TLR7/8 agonist were administered during main RSV illness of BALB/c mice and of FVB and A/J mice, models with increased susceptibility to lung pathology (FVB, our unpublished data) and reactive airways CAL-101 (GS-1101, Idelalisib) disease (A/J) [35], to determine whether immunity could be enhanced or disease reduced. CpG treatment resulted in a significant enhancement of weight loss early in illness, spanning days 3-6 (Number 1C, p 0.05 relative to PBS-treated mice of the same strain). Even though magnitude of improved illness was related with 15-20% excess weight loss from day time 0, the period of the effect was different between strains, with the effect in BALB/c mice becoming most prolonged. TLR7/8 agonist enhanced RSV-induced weight loss, but the timing of the effect varied (Number 1C). In both A/J and FVB mice TLR7/8 agonist induced an early peak of excess weight loss that reached statistical significance in FVB mice at days 3 and 4 post-infection while excess weight loss in BALB/c mice did not peak until day time 7 post-infection. Interestingly, in A/J mice administration of TLR7/8 agonist resulted in a second wave of weight loss very late after illness (days 10-12) with statistically significant variations observed at day time 11 post-infection. Only FVB mice evidenced an advantage from TLR treatments with more quick recovery of excess weight loss (p 0.05 days 7-8 relative to PBS-treated A/J mice). Therefore, TLR activation offers differential impact on RSV disease severity depending upon TLR specificity, sponsor genetics, and time of administration relative to live RSV illness. Only CpG administration during FI-RSV immunization raises safety against RSV challenge Mice immunized with FI-RSV and treated with CpG, only or in.