Synthetic CpG-ODN rapidly enriches immune compartments in neonatal chicks to induce protective immunity against bacterial infections

Immunization of turkeys with Clostridium septicum alpha toxin-based recombinant subunit proteins can confer protection against experimental Clostridial dermatitis

Clostridial dermatitis (CD), caused by Clostridium septicum, is an emerging disease of increasing economic importance in turkeys. Currently, there are no effective vaccines for CD control. Here, two non-toxic domains of C. septicum alpha toxin, namely ntATX-D1 and ntATX-D2, were identified, cloned, and expressed in Escherichia coli as recombinant subunit proteins to investigate their use as potential vaccine candidates. Experimental groups consisted of a Negative control (NCx) that did not receive C. septicum challenge, while the adjuvant-only Positive control (PCx), ntATX-D1 immunization (D1) and ntATX-D2 immunization (D2) groups received C. septicum challenge. Turkeys were immunized subcutaneously with 100 μg of protein at 7, 8 and 9 weeks of age along with an oil-in-water nano-emulsion adjuvant, followed by C. septicum challenge at 11 weeks of age. Results showed that while 46.2% of birds in the PCx group died post-challenge, the rate of mortality in D1- or D2-immunization groups was 13.3%. The gross and histopathological lesions in the skin, muscle and spleen showed that the disease severity was highest in PCx group, while the D2-immunized birds had significantly lower lesion scores when compared to PCx. Gene expression analysis revealed that PCx birds had significantly higher expression of pro-inflammatory cytokine genes in the skin, muscle and spleen than the NCx group, while the D2 group had significantly lower expression of these genes compared to PCx. Peripheral blood cellular analysis showed increased frequencies of activated CD4+ and/or CD8+ cells in the D1 and D2-immunized groups. Additionally, the immunized turkeys developed antigen-specific serum IgY antibodies. Collectively, these findings indicate that ntATX proteins, specifically the ntATX-D2 can be a promising vaccine candidate for protecting turkeys against CD and that the protection mechanisms may include downregulation of C. septicum-induced inflammation and increased CD4+ and CD8+ cellular activation.

A systematic review and meta-analysis on the efficacy of vaccination against colibacillosis in broiler production

Colibacillosis, a disease caused by Escherichia coli in broiler chickens has serious implications on food safety, security, and economic sustainability. Antibiotics are required for treating the disease, while vaccination and biosecurity are used for its prevention. This systematic review and meta-analysis, conducted under the COST Action CA18217-European Network for Optimization of Veterinary Antimicrobial Treatment (ENOVAT), aimed to assess the efficacy of E. coli vaccination in broiler production and provide evidence-based recommendations. A comprehensive search of bibliographic databases, including, PubMed, CAB Abstracts, Web of Science and Agricola, yielded 2,722 articles. Following a defined protocol, 39 studies were selected for data extraction. Most of the studies were experimental infection trials, with only three field studies identified, underscoring the need for more field-based research. The selected studies reported various types of vaccines, including killed (n = 5), subunit (n = 8), outer membrane vesicles/protein-based (n = 4), live/live-attenuated (n = 16), and CpG oligodeoxynucleotides (ODN) (n = 6) vaccines. The risk of bias assessment revealed that a significant proportion of studies reporting mortality (92.3%) or feed conversion ratio (94.8%) as outcomes, had "unclear" regarding bias. The meta-analysis, focused on live-attenuated and CpG ODN vaccines, demonstrated a significant trend favoring both vaccination types in reducing mortality. However, the review also highlighted the challenges in reproducing colibacillosis in experimental setups, due to considerable variation in challenge models involving different routes of infection, predisposing factors, and challenge doses. This highlights the need for standardizing the challenge model to facilitate comparisons between studies and ensure consistent evaluation of vaccine candidates. While progress has been made in the development of E. coli vaccines for broilers, further research is needed to address concerns such as limited heterologous protection, practicability for application, evaluation of efficacy in field conditions and adoption of novel approaches.

Evaluation of Adjuvant Effect of Cytosine-Guanosine-Oligodeoxynucleotide in Meat-Type Chickens Coadministered In Ovo with Herpesvirus of Turkey Vaccine

Herpesvirus of turkey (HVT) increases activation of T cells in 1-day-old chickens when administered in ovo. This study evaluated whether adding cytosine-guanosine oligodeoxynucleotides (CpG ODNs) to the HVT vaccine could enhance the adjuvant effect of HVT. We used a CpG ODN dose of 10 μg per egg. The experimental groups were (1) diluent-only control (sham), (2) HVT, (3) HVT+CpG ODN, (4) HVT+non-CpG ODN, (5) CpG ODN, and (6) non-CpG ODN control. Cellular response evaluation included measuring the frequencies of macrophages (KUL01+MHC-II+), gamma delta T cells (γδTCR+MHC-II+), CD4+, and CD8+ T cell subsets, including double-positive (DP) cells. In addition, CD4+ and CD8+ T cell activation was evaluated by measuring the cellular expression of major histocompatibility complex class II (MHC-II), CD44 or CD28 costimulatory molecules. An adjuvant effect was considered when HVT+CpG ODN, but not HVT+non CpG ODN, or CpG ODN, or non-CpG ODN, induced significantly increased effects on any of the immune parameters examined when compared with HVT. The findings showed that (1) HVT vaccination induced significantly higher frequencies of γδ+MHC-II+ and CD4+CD28+ T cells when compared with sham chickens. Frequencies of DP and CD4+CD28+ T cells in HVT-administered birds were significantly higher than those observed in the non-CpG ODN group. (2) Groups receiving HVT+CpG ODN or CpG ODN alone were found to have significantly increased frequencies of activated CD4+ and CD8+ T cells, when compared with HVT. Our results show that CpG ODN administration in ovo with or without HVT significantly increased frequencies of activated CD4+ and CD8+ T cells.

A novel CpG ODN compound adjuvant enhances immune response to spike subunit vaccines of porcine epidemic diarrhea virus

CpG oligodeoxynucleotides (CpG ODNs) boost the humoral and cellular immune responses to antigens through interaction with Toll-like receptor 9 (TLR9). These CpG ODNs have been extensively utilized in human vaccines. In our study, we evaluated five B-type CpG ODNs that have stimulatory effects on pigs by measuring the proliferation of porcine peripheral blood mononuclear cells (PBMCs) and assessing interferon gamma (IFN-γ) secretion. Furthermore, this study examined the immunoenhancing effects of the MF59 and CpG ODNs compound adjuvant in mouse and piglet models of porcine epidemic diarrhea virus (PEDV) subunit vaccine administration. The in vitro screening revealed that the CpG ODN named CpG5 significantly stimulated the proliferation of porcine PBMCs and elevated IFN-γ secretion levels. In the mouse vaccination model, CpG5 compound adjuvant significantly bolstered the humoral and cellular immune responses to the PEDV subunit vaccines, leading to Th1 immune responses characterized by increased IFN-γ and IgG2a levels. In piglets, the neutralizing antibody titer was significantly enhanced with CpG5 compound adjuvant, alongside a considerable increase in CD8+ T lymphocytes proportion. The combination of MF59 adjuvant and CpG5 exhibits a synergistic effect, resulting in an earlier, more intense, and long-lasting immune response in subunit vaccines for PEDV. This combination holds significant promise as a robust candidate for the development of vaccine adjuvant.

In Ovo Vaccination with Recombinant Herpes Virus of the Turkey-Laryngotracheitis Vaccine Adjuvanted with CpG-Oligonucleotide Provides Protection against a Viral Challenge in Broiler Chickens

Infectious laryngotracheitis (ILT) is an economically important disease in chickens. We previously showed that an in ovo adjuvantation of recombinant herpesvirus of the turkey-Laryngotracheitis (rHVT-LT) vaccine with CpG-oligonucleotides (ODN) can boost vaccine-induced responses in one-day-old broiler chickens. Here, we evaluated the protective efficacy of in ovo administered rHVT-LT + CpG-ODN vaccination against a wild-type ILT virus (ILTV) challenge at 28 days of age and assessed splenic immune gene expression as well as cellular responses. A chicken-embryo-origin (CEO)-ILT vaccine administered in water at 14 days of age was also used as a comparative control for the protection assessment. The results showed that the rHVT-LT + CpG-ODN or the CEO vaccinations provided significant protection against the ILTV challenge and that the level of protection induced by both the vaccines was statistically similar. The protected birds had a significantly upregulated expression of interferon (IFN)γ or interleukin (IL)-12 cytokine genes. Furthermore, the chickens vaccinated with the rHVT-LT + CpG-ODN or CEO vaccine had a significantly higher frequency of γδ T cells and activated CD4+ or CD8+ T cells, compared to the unvaccinated-ILTV challenge control. Collectively, our findings suggest that CpG-ODN can be used as an effective adjuvant for rHVT-LT in ovo vaccination to induce protective immunity against ILT in broiler chickens.

Emerging in ovo technologies in poultry production and the re-discovered chicken model in preclinical research

Prenatal programming is a concept based on assumptions that the events occurring in critical points of embryonic development may pose epigenetic changes resulting from chemical rearrangements on the DNA structure. Epigenetic changes may pose life lasting phenotypic effects in the animal, or can be heritable, like gene silencing associated with methylation in gene promoters regions. The technical advancements in biotechnology, bioinformatics, molecular techniques and robotization have brought to new technological applications in poultry production. Intentional stimulation of embryonic development and determination of the future health of the hatched organism is possible by in ovo application of natural antioxidants and prebiotics, gut stabilizers like probiotics and other immunological enhancements, including vaccines. In parallel, the fine-tuned and generally accessible techniques of chicken embryo incubation along with the novel tissue engineering tools have led to focus the attention of scientists on chicken embryo as the alternative animal model for some pre-clinical approaches, in the context of reducing and replacing the experiments on animals. In this chapter, some key highlights are provided on current achievements in poultry embryonic applications, with the attention put to the emerging in ovo technologies (in ovo feeding, immunological stimulation and in ovo oncological tools), that address the societal challenges in food production and health management.

Comparative study of the impact of dietary supplementation with different types of CpG oligodeoxynucleotides (CpG ODNs) on enhancing intestinal microbiota diversity, antioxidant capacity, and immune-related gene expression profiles in Pacific white shrimp (Litopenaeus vannamei)

The CpG oligodeoxynucleotides (CpG ODNs) reportedly possess the capacity to strengthen immunity in mammals. This experiment was conducted to evaluate the impact of dietary supplementation with 17 types of CpG ODNs on intestinal microbiota diversity, antioxidant capacity, and immune-related gene expression profiles of the shrimp Litopenaeus vannamei. Diets including 50 mg kg^-1 CpG ODNs wrapped in egg whites were prepared and divided into 17 different groups, with 2 control groups (normal feed and feed with egg whites). These CpG ODNs supplemented diets and the control diets were fed to L. vannamei (5.15 ± 0.54 g) three times daily at 5%-8% shrimp body weight for three weeks. The results of consecutive detection of intestinal microbiota by 16S rDNA sequencing indicated that 11 of the 17 types of CpG ODNs significantly enhanced intestinal microbiota diversity, increased the populations of several probiotic bacteria, and activated possible mechanisms relevant to diseases. The immune-related genes expression and antioxidant capacity in hepatopancreas further demonstrated that the 11 types of CpG ODNs effectively improved the innate immunity of shrimp. Additionally, histology results showed that the CpG ODNs in the experiment did not damage the tissue structure of hepatopancreas. The results suggest that CpG ODNs could be used as a trace supplement to improve the intestinal health and immunity of shrimp.

LACpG10-HL Functions Effectively in Antibiotic-Free and Healthy Husbandry by Improving the Innate Immunity

Antibiotics are broadly restricted in modern husbandry farming, necessitating the need for efficient and low-cost immunomodulatory preparations in antibiotic-free and healthful farming. As is known to all, CpG oligonucleotides (CpG-ODNs, an effective innate immunostimulatory agent) recognized by TLR9 in mammals (while TLR21 in avians) could collaborate with some united agent to induce stronger immune responses, but the cost is prohibitively expensive for farmers. Here, considering the coordination between TLR2 and TLR9/TLR21, we firstly proposed the idea that the well-fermented Lactococcus lactis could be utilized as a CpG-plasmid carrier (LACpG10) to enhance the host’s innate immunity against pathogenic invasion. In the present study, after obtaining LACpG10-HL from homogenized and lyophilized recombinant strain LACpG10, we treated primary chicken lymphocytes, two cell lines (HD11 and IPEC-J2), and chickens with LACpG10-HL, CpG plasmids (pNZ8148-CpG10), and other stimulants, and respectively confirmed the effects by conducting qRT-PCR, bacterial infection assays, and a zoological experiment. Our data showed that LACpG10-HL could induce excellent innate immunity by regulating autophagy reactions, cytokine expression, and motivating PRRs. Interestingly, despite having no direct antiseptic effect, LACpG10-HL improved the antibacterial capacities of lymphocytes and enterocytes at the first line of defense. Most importantly, water-supplied LACpG10-HL treatment reduced the average adverse event rates, demonstrating that LACpG10-HL maintained its excellent immunostimulatory and protective properties under farming conditions. Our research not only contributes to revealing the satisfactory effects of LACpG10-HL but also sheds new light on a cost-effective solution with optimal immune effects in green, antibiotic-free, and healthful husbandry farming.

Enhancement of protective efficacy of innate immunostimulant based formulations against yolk sac infection in young chicks

This study was conducted to characterize and compare the protective effects of various innate immune stimulants against yolk sac infection (YSI) caused by an avian pathogenic Escherichia coli in young chicks. The immune stimulants were administered alone or in various combinations of unmethylated CpG oligodeoxynucleotides (CpG), polyinosinic:polycytidylic acid (Poly I:C), and avian antimicrobial peptides (AMPs). Routes included in ovo or in ovo followed by a subcutaneous (S/C) injection. CpG alone and in combination with Poly I:C, truncated avian cathelicidin (CATH)-1(6-26), avian beta defensin (AvBD)1, and CATH-1(6-26) + AvBD1, were administered in ovo to 18-day-old embryonated eggs for gene expression and challenge studies. Next, CpG alone and the potentially effective formulation of CpG + Poly I:C, were administrated via the in ovo route using 40 embryonated eggs. At 1 day post-hatch, half of each group also received their respective treatments via the S/C route. Four hours later, all chicks were challenged using E. coli strain EC317 and mortalities were recorded for 14 d. The first challenge study revealed that amongst the single use and combinations of CpG with different innate immune stimulants, a higher protection and a lower clinical score were offered by the combination of CpG + Poly I:C. The second challenge study showed that this combination (CpG + Poly I:C) provides an even higher level of protection when a second dose is administered via the S/C route at 1 day post-hatch. The current research highlights the efficacy of a combination of CpG + Poly I:C administered either in ovo or in ovo along with a S/C injection and its potential use as an alternative to antibiotics against yolk sac infection in young chicks.

Comparison of Therapeutic Antibiotics, Probiotics, and Synthetic CpG-ODNs for Protective Efficacy Against Escherichia coli Lethal Infection and Impact on the Immune System in Neonatal Broiler Chickens

The poultry industry needs alternatives to antibiotics, as there are growing public concerns about the emergence of antimicrobial resistance owing to antimicrobial use in animal production. We have reported that the administration of neonatal chicks with synthetic DNA oligodeoxynucleotides containing unmethylated cytosine guanine dinucleotide (CpG) motifs (CpG-ODN) can protect against bacterial pathogens in chickens. The objective of this study was to compare the immunoprotective effects of CpG-ODN and probiotics against Escherichia coli infection vs. commonly used therapeutic antibiotics. Day-old broiler chicks were divided into five groups (n = 35/group; 30 for the challenge experiment and 5 for the flow cytometry analysis). The chicks in Group 1 received a single dose of CpG-ODN by the intramuscular route on day 4 (D4) posthatch (PH), and Group 2 received drinking water (DW) with a probiotic product (D1-D15 PH, DW). The Group 3 chicks received tetracycline antibiotics during D9-D13 in DW; the Group 4 chicks got sodium sulfamethazine on D9, D10, and D15 PH in DW; and the Group 5 chicks were administered intramuscular (IM) saline D4 PH, DW. We challenged all the groups (n = 30/group) with E. coli (1 × 10⁵ or 1 × 10⁶ colony-forming units/bird) on D8 PH through the subcutaneous route. Our data demonstrated that the CpG-ODNs, but not the probiotics, could protect neonatal broiler chickens against lethal E. coli septicemia, as would the tetracycline or sodium sulfamethazine. The flow cytometry analysis (n = 5/group) revealed enrichment of immune cells in the CpG-ODN group and a marked decrease in macrophages and T-cell numbers in antibiotics-treated groups, indicating immunosuppressive effects. Our data showed that, like therapeutic antibiotics, CpG-ODNs reduced clinical signs, decreased bacterial loads, and induced protection in chicks against E. coli septicemia. Unlike therapeutic antibiotics-induced immunosuppressive effects, CpG-ODN caused immune enrichment by increasing chicken immune cells recruitment. Furthermore, this study highlights that, although therapeutic antibiotics can treat bacterial infections, the ensuing immunosuppressive effects may negatively impact the overall chicken health.

The Immunomodulatory Functions of Various CpG Oligodeoxynucleotideson CEF Cells and H9N2 Subtype Avian Influenza Virus Vaccination

CpG oligodeoxynucleotides (CpG ODN) present adjuvant activities for antigen proteins, which can induce humoral and cellular immune responses to antigens. However, the immunomodulatory functions of CpG ODNs with different sequences are very different. In this paper, six CpG ODNs with different sequences were designed based on CpG2007 as a template. Through the screening of CEF cells in vitro, the stimulating activity of CpG ODNs was determined. Then, two selected CpG ODN sequence backbones were modified by substituting the oxygen with sulfur (S-CpG) and verifying the immune activity. Next, to prove the feasibility of S-CpG as an immune potentiator, two immune models with or without white oil adjuvant were prepared in 20-day-old chicken vaccinations. The screening experiment in vitro showed that the inducing roles of CpG ODN 4 and 5 could strongly stimulate various immune-related molecular expressions. Additionally, CpG ODN 4 and 5 with sulfation modification significantly induced various cytokines’ expressions. Furthermore, CpG ODN 4 and 5 induced the strongly humoral and cellular immune responses during vaccination, in which white oil, as an adjuvant, could significantly improve the immune effect of CpG ODN. These results provide an important experimental basis for exploring the structural characteristics and vaccine immunity of CpG ODN.

In ovo Feeding as a Tool for Improving Performance and Gut Health of Poultry: A Review

Early growth and development of the gastrointestinal tract are of critical importance to enhance nutrients' utilization and optimize the growth of poultry. In the current production system, chicks do not have access to feed for about 48-72 h during transportation between hatchery and production farms. This lag time affects early nutrient intake, natural exposure to the microbiome, and the initiation of beneficial stimulation of the immune system of chicks. In ovo feeding can provide early nutrients and additives to embryos, stimulate gut microflora, and mitigate the adverse effects of starvation during pre-and post-hatch periods. Depending on the interests, the compounds are delivered to the embryo either around day 12 or 17 to 18 of incubation and via air sac or amnion. In ovo applications of bioactive compounds like vaccines, nutrients, antibiotics, prebiotics, probiotics, synbiotics, creatine, follistatin, L-carnitine, CpG oligodeoxynucleotide, growth hormone, polyclonal antimyostatin antibody, peptide YY, and insulin-like growth factor-1 have been studied. These compounds affect hatchability, body weight at hatch, physiological functions, immune responses, gut morphology, gut microbiome, production performance, and overall health of birds. However, the route, dose, method, and time of in ovo injection and host factors can cause variation, and thereby inconsistencies in results. Studies using this method have manifested the benefits of injection of different single bioactive compounds. But for excelling in poultry production, researchers should precisely know the proper route and time of injection, optimum dose, and effective combination of different compounds. This review paper will provide an insight into current practices and available findings related to in ovo feeding on performance and health parameters of poultry, along with challenges and future perspectives of this technique.

Chitosan nanoparticles fabricated through host-guest interaction for enhancing the immunostimulatory effect of CpG oligodeoxynucleotide

CpG oligodeoxynucleotides (CpG ODNs) which can induce innate immune responses and promote adaptive immune responses, are powerful tools in defeating diseases. Here, a novel chitosan nanoparticle (CS-NPs) based on host-guest interaction has been designed for encapsulation and delivery of CpG ODNs for the first time. The CS-NPs exhibited high encapsulation efficiency (98.3%) of CpG ODNs and remained stable in storage under room temperature for at least 7 days. CS-NPs can also prevent CpG ODN diffusion at pH 7. The results of confocal laser scanning microscope images and flow cytometry show that CS-NPs can also be efficiently delivered into living cells. Furthermore, CpG@CS-NPs can increase the immunostimulatory activity of CpG ODNs. Raw 264.7 cells treated with CpG@CS-NPs demonstrated upregulation of both TNF-α and IL-6 cytokines by 13% and 40%, respectively. The newly developed CpG@CS-NPs were thus identified as an efficient system to deliver CpG-ODNs to treat various diseases.

CpG-ODN induced antimicrobial immunity in neonatal chicks involves a substantial shift in serum metabolic profiles

Synthetic CpG-ODNs can promote antimicrobial immunity in neonatal chicks by enriching immune compartments and activating immune cells. Activated immune cells undergo profound metabolic changes to meet cellular biosynthesis and energy demands and facilitate the signaling processes. We hypothesize that CpG-ODNs induced immune activation can change the host’s metabolic demands in neonatal chicks. Here, we used NMR-based metabolomics to explore the potential of immuno-metabolic interactions in the orchestration of CpG-ODN-induced antimicrobial immunity. We administered CpG-ODNs to day-old broiler chicks via intrapulmonary (IPL) and intramuscular (IM) routes. A negative control group was administered IPL distilled water (DW). In each group (n = 60), chicks (n = 40) were challenged with a lethal dose of Escherichia coli, two days post-CpG-ODN administration. CpG-ODN administered chicks had significantly higher survival (P < 0.05), significantly lower cumulative clinical scores (P < 0.05), and lower bacterial loads (P < 0.05) compared to the DW control group. In parallel experiments, we compared NMR-based serum metabolomic profiles in neonatal chicks (n = 20/group, 24 h post-treatment) treated with IM versus IPL CpG-ODNs or distilled water (DW) control. Serum metabolomics revealed that IM administration of CpG-ODN resulted in a highly significant and consistent decrease in amino acids, purines, betaine, choline, acetate, and a slight decrease in glucose. IPL CpG-ODN treatment resulted in a similar decrease in purines and choline but less extensive decrease in amino acids, a stronger decrease in acetate, and a considerable increase in 2-hydroxybutyrate, 3-hydroxybutyrate, formic acid and a mild increase in TCA cycle intermediates (all P < 0.05 after FDR adjustment). These perturbations in pathways associated with energy production, amino acid metabolism and nucleotide synthesis, most probably reflect increased uptake of nutrients to the cells, to support cell proliferation triggered by the innate immune response. Our study revealed for the first time that CpG-ODNs change the metabolomic landscape to establish antimicrobial immunity in neonatal chicks. The metabolites highlighted in the present study can help future targeted studies to better understand immunometabolic interactions and pinpoint the key molecules or pathways contributing to immunity.

Polymeric antigen BLSOmp31 formulated with class B CpG-ODN in a nanostructure (BLSOmp31/CpG-ODN/Coa-ASC16) administered by parenteral or mucosal routes confers protection against Brucella ovis in Balb/c mice

Previously, we demonstrated that the chimera BLSOmp31 formulated in chitosan microspheres or Poloxamer407-Chitosan administered via the nasal and the ocular mucosa conferred partial protection in sheep against B. ovis. In this work, we tested a new delivery system for mucosal immunization with BLSOmp31 in the murine model to improve the efficacy of previously used formulations. First, we evaluated the protective efficacy against B. ovis induced by BLSOmp31 administered by the subcutaneous route using either BLSOmp31 alone, co-administered with immunostimulatory synthetic oligodeoxynucleotides containing unmethylated cytosine-guanine motifs (CpG-ODN) or with CpG-ODN in a nanostructure called Coa-ASC16 compared with BLSOmp31 emulsified in Incomplete Freund Adjuvant. Then, we evaluated the protection conferred by the best performing formulation (BLSOmp31/CpG-ODN/Coa-ASC16) administered by both subcutaneous and ocular routes. BLSOmp31/CpG-ODN/Coa-ASC16 injected subcutaneously did not induce higher IgG antibody levels compared to BLSOmp31 alone or BLSOmp31/CpG-ODN but it did stimulate a mixed immune Th1-Th2 response with the highest levels of IFN-ɣ and conferred significant protection against the B. ovis challenge. Although ocular instillation of BLSOmp31/CpG-ODN/Coa-ASC16 showed a similar degree of protection compared to the parenteral route (3.66 and 3.60 logs of protection, respectively), it induced lower levels in serum of specific IgG (with mixed IgG1/IgG2a) and IgA antibodies and, less IFN-ɣ and IL-4 than the subcutaneous route. No antibodies were detected in vaginal lavages or saliva. Fecal antigen-specific IgA was slightly higher in mice immunized with BLSOmp31/CpG-ODN/Coa-ASC16 subcutaneously compared with the ocular route. These results indicate that BLSOmp31/CpG-ODN/Coa-ASC16 was a safe and effective vaccine against B. ovis in mice.

Avian antimicrobial peptides: in vitro and in ovo characterization and protection from early chick mortality caused by yolk sac infection

Increasing antibiotic resistance is a matter of grave concern for consumers, public health authorities, farmers, and researchers. Antimicrobial peptides (AMPs) are emerging as novel and effective non-antibiotic tools to combat infectious diseases in poultry. In this study, we evaluated six avian AMPs including 2 truncated cathelicidins, [CATH-1(6-26) and CATH-2(1-15)], and 4 avian β-defensins (ABD1, 2, 6 and 9) for their bactericidal and immunomodulatory activities. Our findings have shown CATH-1(6-26) and ABD1 being the two most potent avian AMPs effective against Gram-positive and Gram-negative bacteria investigated in these studies. Moreover, CATH-1(6-26) inhibited LPS-induced NO production and exhibited dose-dependent cytotoxicity to HD11 cells. While, ABD1 blocked LPS-induced IL-1β gene induction and was non-toxic to HD11 cells. Importantly, in ovo administration of these AMPs demonstrated that ABD1 can offer significant protection from early chick mortality (44% less mortality in ABD1 treated group versus the control group) due to the experimental yolk sac infection caused by avian pathogenic Escherichia coli. Our data suggest that in ovo administration of ABD1 has immunomodulatory and anti-infection activity comparable with CpG ODN. Thus, ABD1 can be a significant addition to potential alternatives to antibiotics for the control of bacterial infections in young chicks.

Aerosol delivery of synthetic DNA containing CpG motifs in broiler chicks at hatch under field conditions using a commercial-scale prototype nebulizer provided protection against lethal Escherichia coli septicemia

Synthetic DNA containing CpG motifs (CpG-ODN) are potent innate immune stimulators in neonatal and adult broiler chickens against bacterial septicemia. We have recently demonstrated that intrapulmonary (IPL) delivery of CpG-ODN as microdroplets under laboratory conditions can protect neonatal chickens against lethal Escherichia coli septicemia. The objectives of this study were to develop a commercial-scale poultry nebulizer (CSPN) that can deliver CpG-ODN as microdroplets in neonatal broiler chicks in the hatcheries and study the efficacy of CSPN in inducing immune-protective effects under different environmental conditions in 2 geographical locations in Canada. Three field experiments were conducted in commercial poultry hatcheries during different seasons of the year in Saskatchewan and British Columbia, Canada. Neonatal broiler chicks (n = 8,000/experiment) received CpG-ODN by the IPL route in the CSPN chamber for 30 min, and control chicks received distilled water (DW) for 30 min. Broiler chicks (CpG-ODN—240 chicks/experiment and DW—40 chicks/experiment) were randomly sampled from all locations of the CSPN after nebulization and challenged with a lethal dose of E. coli to examine the CpG-ODN nebulization induced protection. We found a significant level (P < 0.05) of protection in broiler chicks against E. coli challenge, suggesting that the newly built CSPN successfully delivered CpG-ODN via the IPL route. We found that when the CSPN was maintained at humidex 28°C or below and relative humidity (RH) between 40 and 60%, neonatal birds were significantly (P < 0.05) protected against E. coli septicemia after IPL delivery of CpG-ODN. By contrast, protection in chicks was adversely affected when the CSPN was maintained at the humidex of 29°C or higher and RH of 70%. Overall, the present study successfully built a CSPN for CpG-ODN delivery in chicks at the hatchery and revealed that the temperature, humidity, and humidex were critical parameters in CSPN for efficient delivery of CpG-ODN.

Identification of RBP4 from bighead carp (Hypophthalmichthys nobilis) / silver carp (Hypophthalmichthys molitrix) and effects of CpG ODN on RBP4 expression under A. hydrophila challenge

Retinol-binding protein 4 (RBP4) is known as a highly conserved adipokine for immune activation. Aeromonas hydrophila (A. hydrophila) is the most common zoonotic pathogen in aquaculture, which causes serious economic losses to aquaculture, especially to bighead carp (Hypophthalmichthys nobilis, H. nobilis) and silver carp (Hypophthalmichthys molitrix, H. molitrix). Recent studies along with our previous findings have shown that synthetic oligodeoxynucleotides containing CpG motifs (CpG ODN) can play a good role in aquatic animals against infection. In order to clarify the relationship between CpG ODN and RBP4 under A. hydrophila infection, firstly, full-length RBP4 cDNAs from H. nobilis and H. molitrix were cloned. And characteristics of RBP4, including sequence and structure, tissue distribution and genetic evolution were analyzed. In addition, mRNA expression levels of RBP4, cytokine, toll-like receptors (TLRs), morbidity and survival rates of H. nobilis and H. molitrix were observed post CpG ODN immunization or following challenge. The results indicated that hn/hm_RBP4 (RBP4 genes obtained from H. nobilis and H. molitrix) had the highest homology with Megalobrama amblycephala. Distribution data showed that the expression level of hn_RBP4 mRNA was higher than that of hm_RBP4. After CpG ODN immunization followed by A.hydrophila challenge, significantly higher survival was observed in both carps, together with up-regulated RBP4 expression. Meanwhile, hn/hm_IL-1β level was relatively flat (and decreased), hn/hm_IFN-γ, hn/hm_TLR4 and hn/hm_TLR9 levels increased significantly, but hn/hm_STRA6 showed no significant change, compared with control. Moreover, CpG ODN immunization could induce stronger immune protective responses (higher IFN-γ/gentle IL-1β level and lower morbidity/higher survival rate) against A. hydrophila in H. nobilis, along with higher RBP4 level, when compared with that in H. molitrix. These results demonstrated that RBP4 was well involved in the immune protection of CpG ODN. Based on the results, we speculated that in the case of A. hydrophila infection, TLR9 signaling pathway was activated by CpG ODN. Subsequently, CpG ODN up-regulated RBP4, and RBP4 activated TLR4 signaling pathway. Then TLR4 and TLR9 synergistically improved the anti-infection responses. Our findings have good significance for improving resistance to pathogen infection in freshwater fish.

Mucosal delivery of CpG-ODN mimicking bacterial DNA via the intrapulmonary route induces systemic antimicrobial immune responses in neonatal chicks

The transition to antibiotic-free poultry production in the face of pathogenic threats is a very challenging task. We recently demonstrated that mucosal delivery of CpG-ODN alone by the intrapulmonary route (IPL) has potential as an effective alternative to antibiotics in neonatal chicks against Escherichia coli septicemia. How exactly mucosal delivery of CpG-ODN elicits, protective antibacterial immunity remained poorly understood. In this study, CpG-ODN or saline was delivered via the intrapulmonary route to day-old chicks (n = 80/group) using a compressor nebulizer in an acrylic chamber (1 mg/mL CpG-ODN for 15 minutes). In the first part of the study, two days after mucosal CpG-ODN delivery, 40 chicks from each group were challenged subcutaneously with 1 × 10⁵ cfu (n = 20) or 1 × 10⁶ cfu (n = 20) of E. coli and the mortality pattern was monitored for seven days. We found significantly higher survival, better clinical conditions and lower bacterial loads in chicks that received mucosal CpG-ODN. To explore the mechanisms behind this protective immunity, we first looked at the kinetics of the cytokine gene expression (three birds/ group/ time for 10 time-points) in the lungs and spleens. Multiplex gene analysis demonstrated a significant elevation of pro-inflammatory cytokine genes mRNA in the CpG-ODN group. Interleukin (IL)-1β robustly upregulated many folds in the lung after CpG-ODN delivery. Lipopolysaccharide-induced tumor necrosis factor (LITAF) and IL-18 showed expression for an extended period in the lungs. Anti-inflammatory cytokine IL-10 was upregulated in both lungs and spleen, whereas IL-4 showed upregulation in the lungs. To investigate the kinetics of immune enrichment in the lungs and spleens, we performed flow cytometry, histology, and immunohistochemistry at 24, 48 and 72 hrs after CpG-ODN delivery. CpG-ODN treated lungs showed a significant enrichment with monocytes/macrophages and CD4⁺ and CD8⁺ T-cell subsets. Macrophages in CpG-ODN treated group demonstrated mature phenotypes (higher CD40 and MHCII expression). Importantly, mucosal delivery of CpG-ODN via the intrapulmonary route significantly enriched immune compartment in the spleen as well, suggesting a systemic effect in neonatal chicks. Altogether, intrapulmonary delivery of aerosolized CpG-ODN orchestrates protective immunity against E. coli septicemia by not only enhancing mucosal immunity but also the systemic immune responses.

CpG-ODN Induces a Dose-Dependent Enrichment of Immunological Niches in the Spleen and Lungs of Neonatal Chicks That Correlates with the Protective Immunity against Escherichia coli

Immunoprotective function of oligodeoxynucleotides containing CpG motifs (CpG-ODN) has been demonstrated in neonatal chickens against common bacterial pathogens such as E.coli and Salmonella sp. Our recent study reported that CpG-ODN administration enriches immune compartments in neonatal chicks. However, a causal relationship between CpG-ODN-induced immune enrichment and protective mechanisms remains unestablished. In this study, we investigated in ovo administered CpG-ODN-mediated immune cell recruitment in the immunological niches in lymphoid (spleen) and nonlymphoid (lungs) organs using various doses of CpG-ODN and examined whether the immunological profiles have any correlation with immunoprotection against E.coli infection. Eighteen-day-old embryonated eggs were injected with either 5, 10, 25, and 50 μg of CpG-ODN or saline (n = ~40 per group). On the day of hatch (72 hr after CpG-ODN treatment), we collected the spleen and lungs (n = 3‐4 per group) and examined the recruitment of macrophages/monocytes, their expression of MHCII and CD40, and the number of CD4⁺ and CD8⁺ T-cell subsets in the immunological niches in the spleen and lungs using flow cytometry. We observed the dose-dependent recruitment of immune cells, wherein 25 μg and 50 μg of CpG-ODN induced significant enrichment of immunological niches in both the spleen and the lungs. Four days after the CpG-ODN treatment (1-day after hatch), chicks were challenged with a virulent strain of E. coli (1 × 10⁴ or 1 × 10⁵ cfu, subcutaneously). Clinical outcome and mortality were monitored for 8 days postchallenge. We found that both 25 μg and 50 μg of CpG-ODN provided significant protection and reduced clinical scores compared to saline controls against E. coli infection. Overall, the present study revealed that CpG-ODNs orchestrate immunological niches in neonatal chickens in a dose-dependent manner that resulted in differential protection against E. coli infection, thus supporting a cause and effect relationship between CpG-ODN-induced immune enrichment and the antibacterial immunity.

Development of innate immunity in chicken embryos and newly hatched chicks: a disease control perspective

Newly hatched chickens are confronted by a wide array of pathogenic microbes because their adaptive immune defences have limited capabilities to control these pathogens. In such circumstances, and within this age group, innate responses provide a degree of protection. Moreover, as the adaptive immune system is relatively naïve to foreign antigens, synergy with innate defences is critical. This review presents knowledge on the ontogeny of innate immunity in chickens pre-hatch and early post-hatch and provides insights into possible interventions to modulate innate responses early in the life of the bird. As in other vertebrate species, the chicken innate immune system which include cellular mediators, cytokine and chemokine repertoires and molecules involved in antigen detection, develop early in life. Comparison of innate immune systems in newly hatched chickens and mature birds has revealed differences in magnitude and quality, but responses in younger chickens can be boosted using innate immune system modulators. Functional expression of pattern recognition receptors and several defence molecules by innate immune system cells of embryos and newly hatched chicks suggests that innate responses can be modulated at this stage of development to combat pathogens. Improved understanding of innate immune system ontogeny and functionality in chickens is critical for the implementation of sound and safe interventions to provide long-term protection against pathogens. Next-generation tools for studying genetic and epigenetic regulation of genes, functional metagenomics and gene knockouts can be used in the future to explore and dissect the contributions of signalling pathways of innate immunity and to devise more efficacious disease control strategies.

The immunostimulator Victrio activates chicken toll-like receptor 21

The immunostimulator Victrio consists of bacterial plasmid DNA encased in cationic liposomes and protects embryonated chicken eggs and newly hatched chickens against Escherichia coli induced mortality. It is demonstrated that Victrio specifically and potently activates recombinant chicken toll-like receptor 21 (TLR21) in a nuclear factor kappa B reporter gene assay. This TLR21 stimulatory activity is dependent on the presence of nonmethylated CpG and requires liposomal formulation of the DNA, as naked plasmid DNA proves to be inactive. Nitric oxide production is induced by Victrio in HD11 chicken macrophages that express TLR21 naturally, supporting the proposal that chicken TLR21 is a component of the molecular mode of action of Victrio.

Immunomodulatory Potential of Tinospora cordifolia and CpG ODN (TLR21 Agonist) against the Very Virulent, Infectious Bursal Disease Virus in SPF Chicks

Infectious bursal disease (IBD), caused by infectious bursal disease virus (IBDV), is characterized by severe immunosuppression in young chicks of 3 to 6 week age group. Although vaccines are available to prevent IBD, outbreaks of disease are still noticed in the field among vaccinated flocks. Further, the birds surviving IBD become susceptible to secondary infections caused by various viral and bacterial agents. This study assessed the immunoprophylactic potential of Cytosine-guanosinedeoxynucleotide (CpG) oligodeoxynucleotides (ODN) and Tinospora cordifolia stem aqueous extract in the specific pathogen free (SPF) chicks, experimentally infected with very virulent IBDV (vvIBDV). Both of these agents (CpG ODN and herbal extract) showed significant increase in the IFN-γ, IL-2, IL-4, and IL-1 levels in the peripheral blood mononuclear cells (PBMCs) (p < 0.05) of chickens in the treatment groups following IBD infection.Further we found significant reduction in mortality rate in vvIBDV infected chicks treated with either, or in combination, compared with the birds of control group. Additionally, the adjuvant or immune enhancing potential of these two immunomodulatory agents with the commercially available IBDV vaccine was determined in chicks. The augmentation of vaccine response in terms of an enhanced antibody titer after vaccination, along with either or a combination of the two agents was noticed. The findings provide a way forward to counter the menace of IBDV in the poultry sector through use of these herbal or synthetic immunomodulatory supplements.