Fig. 3
Systemic IL-27p28 induces local IL-27 expression and ameliorates soft tissue infection at the surgical site and osteolysis during S. aureus implant-associated osteomyelitis. a Schematic illustration of the experimental design in which 8-week-old female C57BL/6 WT and IL-27Rα−/− mice (C57BL/6J background) received an injection of rAAV-IL-27p28 or rAAV-GFP in the quadriceps 1 week prior to challenge with a MRSA (5 × 105 CFU of USA300 LAC::lux)-contaminated transtibial implant. The time points for the various outcome measures are also indicated. b WT mice were infected with 0.5 × 1012 genome copies/mouse rAAV-IL-27p28 (n = 3) or rAAV-GFP (control, n = 5) via intramuscular injection, and serum samples were collected longitudinally to assess IL-27 levels via ELISA. The exogenous IL-27p28 levels in serum are presented as the means ± SDs. c–f A separate cohort of mice were infected with rAAV-IL-27p28 or rAAV-GFP via injection and subjected to transtibial implant challenge (n = 16). The longitudinal BLI (c) and total body weight (d) values are presented as the means ± SDs (*P < 0.05 on Day 3, ***P < 0.001 on Day 10 and 14, two-way ANOVA). e Photographs of representative infected tibiae obtained on Day 14 are presented to show the large vs. small draining abscesses observed in rAAV-GFP- vs. rAAV-IL-27p28-treated mice. The mice were euthanized on Day 14, and the infected tibiae were harvested for CFU (f) and micro-CT (g) analyses. CFUs in the implant, soft tissue and tibia were quantified, and the data for each tibia are presented with the mean ± SD for the group (n = 10, ****P < 0.000 1, t-test). Representative 3D renderings of extensive peri-implant osteolysis and reactive bone formation in rAAV-GFP- vs. rAAV-IL-27p28-treated tibiae are shown with volumetric bone loss in infected tibiae. Data are presented for each tibia with the mean ± SD for the group (n = 6, *P < 0.05, t-test). h Total RNA was extracted from infected tibiae (n = 3) at different time points, and IL-27 mRNA levels were measured by bulk RNA sequencing. The expression data are presented as the normalized read counts with the mean ± SD for the group (****P < 0.000 1 on Days 1 and 3, ***P < 0.001 on Days 7 and 14)
