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

Abstract

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.

Antiviral responses against chicken respiratory infections: Focus on avian influenza virus and infectious bronchitis virus

“…The encapsulated TLR ligands in biodegradable poly (D,L-lactide-coglycolide) polymer nanoparticles (PLGA NPs) have the ability to conserve prolonged innate responses through up-regulation of IFN-γ and IL-1β [76]. Consequently, stimulation of the innate immune system with a slow release of TLR ligands from the polymers can enhance antigen-specific immune responses and may be applied as a vaccine or antimicrobial agent in the future [76].…”

Toll-like receptor ligand-dependent inflammatory responses in chick skeletal muscle myoblasts

“…Ligand-binding to chick TLRs, except TLR3, is considered to activate the adaptor molecule, MyD88, for signal transduction (Keestra et al, 2013). In chickens, Pam3CSK4, FSL-1, or LPS induces the expression of inflammatory cytokines such as interleukin (IL)-1β, IL-6, IL-8, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α in the bursa of Fabricius (Cheng et al, 2014), spleen (Alkie et al, 2017;Li et al, 2017), primary-cultured splenocytes (St. Paul et al, 2013), heterophils (Kogut et al, 2006), thrombocytes (Ferdous and Scott, 2015;Winkler et al, 2017), cecal tonsil cells (Taha-abdelaziz et al, 2016), and the macrophage cell line MQ-NCSU (Barjesteh et al, 2014;Alkie et al, 2017). LPS also induces nuclear factor (NF)-κB, a transcription factor for regulating immune responses, in the bursa of Fabricius (Cheng et al, 2014) but not in thrombocytes (Winkler et al, 2017).…”

Characterization of immunogenicity of avian influenza antigens encapsulated in PLGA nanoparticles following mucosal and subcutaneous delivery in chickens

“…AIV and CpG ODN-loaded PLGA NPs were prepared as described previously [ 11 , 41 ]. Briefly, CpG ODN (class B CpG ODN 2007, phosphorothioate backbone modified, ) and polyethylenimine (branched, 25 kD) complex was made as described [ 42 ].…”

“…The size and surface charge of PLGA NPs, and encapsulation efficiency of CpG ODN were determined as described in our previous work [ 41 ]. The encapsulation efficiency of AIV antigen was determined as described in a previous work [ 46 ].…”