Immunotherapeutic Potential of CpG Oligonucleotides in Chickens

Screening of Optimal CpG-Oligodeoxynucleotide for Anti-Inflammatory Responses in the Avian Macrophage Cell Line HD11

CpG-oligodeoxynucleotides (.

CpG-ODNs

) have been shown to possess immunostimulatory features in both mammals and birds. However, compared to their proinflammatory effects, little is known about the anti-inflammatory responses triggered by CpG-ODN in avian cells. Hence, in this study, the anti-inflammatory response in the chicken macrophage cell line HD11 was characterized under stimulation with five types of CpG-ODNs: CpG-A₁₅₈₅, CpG-A_D35, CpG-B₁₅₅₅, CpG-B_K3, and CpG-C₂₃₉₅. Single-stimulus of CpG-B₁₅₅₅, CpG-B_K3, or CpG-C₂₃₉₅ induced interleukin (IL)-10 expression without causing cell injury. The effects of pretreatment with CpG-ODNs before subsequent lipopolysaccharide stimulation were also evaluated. Interestingly, pretreatment with only CpG-C₂₃₉₅ resulted in high expression levels of IL-10 mRNA in the presence of lipopolysaccharide. Finally, gene expression analysis of inflammation-related cytokines and receptors revealed that pre-treatment with CpG-C₂₃₉₅ significantly reduced the mRNA expression of tumor necrosis factor-α, IL-1β, IL-6, and Toll-like receptor 4. Overall, these results shed light on the anti-inflammatory responses triggered by CpG-C₂₃₉₅ stimulation through a comparative analysis of five types of CpG-ODNs in chicken macrophages. These results also offer insights into the use of CpG-ODNs to suppress the expression of proinflammatory cytokines, which may be valuable in the prevention of avian infectious diseases in the poultry industry.

Carbon nanotubes significantly enhance the biological activity of CpG ODN in chickens

Synthetic unmethylated cytidine-phosphate-guanosine oligodeoxynucleotides (CpG ODN) is an effective immune stimulant in chicken. To be effective CpG dosage requirement is high. High dosage increases cost of treatment and introduces toxicity. A delivery system using multi-walled carbon nanotubes (MWCNT) is utilized in this study to aid in lowering the effective dose of the immune stimulant. CpG ODNs were attached non-covalently in different ways to multi-walled carbon nanotubes (MWCNT). We assessed and selected an appropriate linking method of CpG ODN with MWCNT followed by cellular uptake studies to establish that MWCNT-conjugated CpG ODNs were delivered better than free CpG ODNs into the cell. It was observed that MWCNT-conjugated CpG ODNs were equally effective in priming the cells in vitro at 1000-fold less concentration than free CpG ODN. In vivo studies revealed that a significantly lower dose of CpG ODN, when given subcutaneously, was enough to protect chickens from a lethal challenge of bacteria. The mechanism of immune stimulation was examined by in vivo cell recruitment and in vitro cytokine production studies. MWCNT-conjugated CpG ODNs are significantly more efficacious and less toxic than free CpG ODN to qualify as a potential immune stimulant.

CpG-ODNs induced changes in cytokine/chemokines genes expression associated with suppression of infectious bronchitis virus replication in chicken lungs

The process of virus replication in host cells is greatly influenced by the set of cytokines, chemokines and antiviral substances activated as a result of host–virus interaction. Alteration of cytokines profiles through manipulation of the innate immune system by innate immune stimulants may be helpful in inhibiting virus replication in otherwise permissive cells. The aim of present studies was to characterize innate immune responses capable of inhibiting infectious bronchitis virus (IBV) replication in chicken lungs after in ovo administration of CpG ODN. In our experiments, CpG ODN 2007 or PBS solution was injected on 18th embryonic day (ED) via the chorioallontoic route. CpG ODN and PBS inoculated embryos were challenged with virulent IBV on the 19th ED. Lung tissue samples from experimental chicks were analysed for cytokines/chemokines gene expression at 24 h, 48 h, and 72 h, post infection. Our data showed significant differential up-regulation of IFN-γ, IL-8 (CXCLi2) and MIP-1β genes and suppression of IL-6 gene expression being associated with inhibition of IBV replication in lungs tissue retrieved from embryos pre-treated with CpG ODN.

It is expected that understanding of the innate immune modulation of target tissues by the virus and innate immune stimulants will be helpful in identification of valuable targets for development of novel, safe, effective and economical control strategies against IBV infection in chickens.

Effects of estrogen on estrogen receptor expression in the bursal cells of chick embryos and steroidogenic enzymes gene expression in the bursa: relevance of estrogen receptor and estrogen synthesis in the bursa of chick embryos

Estrogen has been reported to act on B cell genesis in the bursa of Fabricius of chick embryos. In this study, we attempted to demonstrate the hypothesis that B cell genesis is controlled by estrogen receptor (ER) in the bursal cells and steroidogenic enzymes synthesized in the bursa. We previously reported the presence of estrogen receptor α (ERα) in the bursa during the late stage of embryogenesis and an increase in the expression of ERα messenger RNA (mRNA) between the 13th day and 16th day. The number of ER-positive cells was maximal on the 16th day. In the present study, ER-positive cells in the bursa during the late stage of embryogenesis increased 4 h after β-estradiol treatment on the 14th to 18th day. The concentration of β-estradiol in the embryonic bursa increased. These results suggest that this stage of embryogenesis is critical in B cell development in the bursa in connection with the effect of estrogen treatment. Our findings also showed that the mRNA expression of five steroidogenic enzymes occurred in the bursa of chick embryos. These results suggest that estrogen is synthesized in the embryonic bursa and estrogen acts on the bursal cells in a paracrine fashion.

TLR9 agonists: immune mechanisms and therapeutic potential in domestic animals

Toll like receptors (TLRs) are transmembrane glycoproteins that recognize conserved microbial molecules. Engagement of TLRs activates innate and adaptive immunity. TLR-mediated activation of immune cells results in upregulation of cytokines, chemokines and costimulatory molecules. These early innate responses control pathogen spread and initiates adaptive immune responses. Synthetic CpG oligodeoxynucleotides (ODN), agonists for TLR9, had shown great promise as immunotherapeutic agents and vaccine adjuvants in laboratory animal models of infectious disease, allergy and cancer. However, it has become apparent that CpG ODN are less potent immune activators in domestic animals and humans. The disparity in immune responses between rodents and mammals has been mainly attributed to differences in cellular expression of TLR9 in the various species. In this article, our current understanding of the immune mechanisms, as well as the potential applications of CpG ODN will be reviewed, with particular emphasis on domestic animals.

Evaluation of beta defensin 2 production by chicken heterophils using direct MALDI mass spectrometry

Beta defensins (BD) are cysteine rich, cationic antimicrobial peptides (AMP) produced mainly by epithelial and myeloid cells such as neutrophils. In birds, the neutrophil equivalent heterophils produce avian beta defensins (AvBD) of which AvBD2 is the major isoform. Heterophils recognize pathogens or their derived products through a series of pattern recognition receptors called toll-like receptors (TLR) leading to their antimicrobial activities. This work is the first report of TLR modulation of AvBD2 expression in chickens. To measure the effect of TLR activation on AvBD2 production, the heterophils were cultured with different TLR agonists for 6h. Modulation of AvBD2 levels by TLR activation was measured using direct MALDI mass spectrometry without stable isotopic labeling or chromatographic separation. Chemical modification of the conditioned media was performed using reduction/alkylation with dithiothreitol/iodoacetamide to distinguish TLR treated AvBD2 (reduced/alkylated) from controls (non-reduced). Changes in corrected ion intensity ratios were assumed to reflect AvBD2 modulation in heterophils upon activation with different TLR agonists. In general, TLR agonists increased AvBD2 production with LPS showing the greatest induction and CpG-ODN showing little or no effect. These data show that the direct MALDI-MS coupled with reduction/alkylation may provide a rapid relative quantitative approach to the measurement of agonist-induced differential expression of AvBD2.