Characterization of Innate Responses Induced by PLGA Encapsulated- and Soluble TLR Ligands In Vitro and In Vivo in Chickens

• Published in: PloS one Vol. 12; no. 1; p. e0169154
• Main Authors: Alkie, Tamiru N, Taha-Abdelaziz, Khaled, Barjesteh, Neda, Bavananthasivam, Jegarubee, Hodgins, Douglas C, Sharif, Shayan
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 03.01.2017; Public Library of Science (PLoS)
• Subjects: Adjuvants; Adjuvants, Immunologic - administration & dosage; Animals; Anti-Infective Agents - pharmacology; Antimicrobial agents; Biocompatible polymers; Biodegradability; Biodegradation; Biology and Life Sciences; Chickens; Chickens - immunology; Controlled release; CpG islands; Cytokines; Cytokines - metabolism; Dendritic cells; Drug delivery systems; Drug dosages; E coli; Encapsulation; Escherichia coli; Female; Gene expression; Gene Expression Profiling; Genetic aspects; Health aspects; IL-1β; Immune response; Immune system; Immunity, Innate; Inflammation; Interferon; Interferon-beta - metabolism; Interferon-gamma - metabolism; Lactic Acid - pharmacology; Ligands; Lipopolysaccharides; Macrophages; Macrophages - metabolism; Mammals; Medicine and Health Sciences; Nanoparticles; Nitric oxide; Nitric Oxide - chemistry; Oligodeoxyribonucleotides - genetics; Oligonucleotides; Poly I-C - pharmacology; Polyglycolic Acid - pharmacology; Polylactide-co-glycolide; Polyvinyl alcohol; Poultry; Proteins; Splenocytes; Testing; Toll-like receptors; Toll-Like Receptors - immunology; Vaccines; γ-Interferon
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0169154

Natural or synthetic Toll-like receptor (TLR) ligands trigger innate responses by interacting with distinct TLRs. TLR ligands can thus serve as vaccine adjuvants or stand-alone antimicrobial agents. One of the limitations of TLR ligands for clinical application is their short half-life and rapid clearance from the body. In the current study, encapsulation of selected TLR ligands in biodegradable poly(D,L-lactide-co-glycolide) polymer nanoparticles (PLGA NPs) was examined in vitro and in vivo as a means to prolong innate responses. MQ-NCSU cells (a chicken macrophage cell line) were treated with encapsulated or soluble forms of TLR ligands and the resulting innate responses were evaluated. In most cases, encapsulated forms of TLR ligands (CpG ODN 2007, lipopolysaccharide and Pam3CSK4) induced comparable or higher levels of nitric oxide and cytokine gene expression in macrophages, compared to the soluble forms. Encapsulated CpG ODN, in particular the higher dose, induced significantly higher expression of interferon (IFN)-γ and IFN-β until at least 18 hr post-treatment. Cytokine expression by splenocytes was also examined in chickens receiving encapsulated or soluble forms of lipopolysaccharide (a potent inflammatory cytokine inducer in chickens) by intramuscular injection. Encapsulated LPS induced more sustained innate responses characterized by higher expression of IFN-γ and IL-1β until up to 96 hr. The ability of TLR ligands encapsulated in polymeric nanoparticles to maintain prolonged innate responses indicates that this controlled-release system can extend the use of TLR ligands as vaccine adjuvants or as stand-alone prophylactic agents against pathogens.