Campylobacter-derived ligands induce cytokine and chemokine expression in chicken macrophages and cecal tonsil mononuclear cells

Safety and efficacy of toll-like receptor agonists as therapeutic agents and vaccine adjuvants for infectious diseases in animals: a systematic review

Introduction

Strengthening global health security relies on adequate protection against infectious diseases through vaccination and treatment. Toll-like receptor (TLR) agonists exhibit properties that can enhance immune responses, making them potential therapeutic agents or vaccine adjuvants.

Methods

We conducted an extensive systematic review to assess the efficacy of TLR agonists as therapeutic agents or vaccine adjuvants for infectious diseases and their safety profile in animals, excluding rodents and cold-blooded animals. We collected qualitative and available quantitative data on the efficacy and safety outcomes of TLR agonists and employed descriptive analysis to summarize the outcomes.

Results

Among 653 screened studies, 51 met the inclusion criteria. In this review, 82% (42/51) of the studies used TLR agonists as adjuvants, while 18% (9/51) applied TLR agonist as therapeutic agents. The predominant TLR agonists utilized in animals against infectious diseases was CpG ODN, acting as a TLR9 agonist in mammals, and TLR21 agonists in chickens. In 90% (46/51) of the studies, TLR agonists were found effective in stimulating specific and robust humoral and cellular immune responses, thereby enhancing the efficacy of vaccines or therapeutics against infectious diseases in animals. Safety outcomes were assessed in 8% (4/51) of the studies, with one reporting adverse effects.

Discussion

Although TLR agonists are efficacious in enhancing immune responses and the protective efficacy of vaccines or therapeutic agents against infectious diseases in animals, a thorough evaluation of their safety is imperative to in-form future clinical applications in animal studies.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=323122.

Comparative Effectiveness of Various Multi-Antigen Vaccines in Controlling Campylobacter jejuni in Broiler Chickens

This study was undertaken to evaluate and compare the efficacy of different multi-antigen vaccines, including heat-inactivated, whole lysate, and subunit (outer membrane proteins [OMPs]) C. jejuni vaccines along with the immunostimulant CpG ODN in controlling Campylobacter colonization in chickens. In the first trial, 125 μg of C. jejuni OMPs and 50 μg of CpG ODN were administered individually or in combination, either in ovo to chick embryos or subcutaneously (SC) to one-day-old chicks. In the second trial, different concentrations of C. jejuni antigens (heat-killed, whole lysate, and OMPs) were administered SC to one-day-old chicks. The results of the first trial revealed that SC immunization with the combination of CpG ODN and C. jejuni OMPs elevated interferon (IFN)-γ, interleukin (IL)-1β, and IL-13 gene expression in the spleen, significantly increased serum IgM and IgY antibody levels, and reduced cecal C. jejuni counts by approximately 1.2 log10. In contrast, in ovo immunization did not elicit immune responses or confer protection against Campylobacter. The results of the second trial showed that SC immunization with C. jejuni whole lysate or 200 μg OMPs reduced C. jejuni counts by approximately 1.4 and 1.1 log10, respectively. In conclusion, C. jejuni lysate and OMPs are promising vaccine antigens for reducing Campylobacter colonization in chickens.

Effect of the polysaccharide capsule and its heptose on the resistance of Campylobacter jejuni to innate immune defenses

Campylobacter jejuni is a commensal in many animals but causes diarrhea in humans. Its polysaccharide capsule contributes to host colonization and virulence in a strain- and model-specific manner. We investigated if the capsule and its heptose are important for interactions of strain NCTC 11168 with various hosts and their innate immune defenses. We determined that they support bacterial survival in Drosophila melanogaster and enhance virulence in Galleria mellonella. We showed that the capsule had limited antiphagocytic activity in human and chicken macrophages, decreased adherence to chicken macrophages, and decreased intracellular survival in both macrophages. In contrast, the heptose increased uptake by chicken macrophages and supported adherence to human macrophages and survival within them. While the capsule triggered nitric oxide production in chicken macrophages, the heptose mitigated this and protected against nitrosative assault. Finally, the C. jejuni strain NCTC 11168 elicited strong cytokine production in both macrophages but quenched ROS production independently from capsule and heptose, and while the capsule and heptose did not protect against oxidative assault, they favored growth in biofilms under oxidative stress. This study shows that the wild-type capsule with its heptose is optimized to resist innate defenses in strain NCTC 11168 often via antagonistic effects of the capsule and its heptose.

Advances in Poultry Vaccines: Leveraging Biotechnology for Improving Vaccine Development, Stability, and Delivery

With the rapidly increasing demand for poultry products and the current challenges facing the poultry industry, the application of biotechnology to enhance poultry production has gained growing significance. Biotechnology encompasses all forms of technology that can be harnessed to improve poultry health and production efficiency. Notably, biotechnology-based approaches have fueled rapid advances in biological research, including (a) genetic manipulation in poultry breeding to improve the growth and egg production traits and disease resistance, (b) rapid identification of infectious agents using DNA-based approaches, (c) inclusion of natural and synthetic feed additives to poultry diets to enhance their nutritional value and maximize feed utilization by birds, and (d) production of biological products such as vaccines and various types of immunostimulants to increase the defensive activity of the immune system against pathogenic infection. Indeed, managing both existing and newly emerging infectious diseases presents a challenge for poultry production. However, recent strides in vaccine technology are demonstrating significant promise for disease prevention and control. This review focuses on the evolving applications of biotechnology aimed at enhancing vaccine immunogenicity, efficacy, stability, and delivery.

Tracheal cellular immune response in chickens inoculated with Mycoplasma synoviae vaccine, MS-H or its parent strain 86079/7NS

Mycoplasma synoviae causes respiratory tract disease in chickens characterised by mild to moderate lymphoplasmacytic infiltration of the tracheal mucosa. MS-H (Vaxsafe1 MS, Bioproperties Pty Ltd.) is an effective live attenuated vaccine for M. synoviae, but the immunological basis for its mechanism of protection has not been investigated, and the phenotypes of lymphocytes and associated cytokines involved in the local adaptive immune response have not been described previously. In this study, specific-pathogen-free chickens were inoculated intra-ocularly at 3 weeks of age with either M. synoviae vaccine strain MS-H or vaccine parent strain 86079/7NS (7NS), or remained uninoculated. At 2-, 7- and 21 days post-inoculation (dpi), tracheal mucosal pathology, infiltrating lymphocytes subsets and transcription levels of mRNA encoding 8 cytokines were assessed using light microscopy, indirect immunofluorescent staining and RT-qPCR, respectively. After inoculation, tracheal mucosal thickness, tracheal mucosal lesions, and numbers of infiltrating CD4⁺CD25^- cells, B-cells, and macrophages were greater in MS-H- and 7NS-inoculated chickens compared with non-inoculated. Inoculation with 7NS induced up-regulation of IFN-γ, while vaccination with MS-H induced up-regulation of IL-17A, when compared with non-inoculated birds. Both inoculated groups had a moderate infiltrate of CD4⁺CD25⁺ T cells in the tracheal mucosa. These findings reveal that the tracheal local cellular response after MS-H inoculation is dominated by a Th-17 response, while that of 7NS-inoculated chickens is dominated by a Th-1 type response.

The Acute Host-Response of Turkeys Colonized With Campylobacter coli

Consumption of contaminated poultry products is one of the main sources of human campylobacteriosis, of which Campylobacter jejuni subsp. jejuni (C. jejuni) and C. coli are responsible for ~98% of the cases. In turkeys, the ceca are an important anatomical site where Campylobacter asymptomatically colonizes. We previously demonstrated that commercial turkey poults colonized by C. jejuni showed acute changes in cytokine gene expression profiles, and histological intestinal lesions at 2 days post-inoculation (dpi). Cecal tonsils (CT) are an important part of the gastrointestinal-associated lymphoid tissue that surveil material passing in and out of the ceca, and generate immune responses against intestinal pathogens. The CT immune response toward Campylobacter remains unknown. In this study, we generated a kanamycin-resistant C. coli construct (CcK) to facilitate its enumeration from cecal contents after experimental challenge. In vitro analysis of CcK demonstrated no changes in motility when compared to the parent isolate. Poults were inoculated by oral gavage with CcK (5 × 107 colony forming units) or sterile-media (mock-colonized), and euthanized at 1 and 3 dpi. At both time points, CcK was recovered from cecal contents, but not from the mock-colonized group. As a marker of acute inflammation, serum alpha-1 acid glycoprotein was significantly elevated at 3 dpi in CcK inoculated poults compared to mock-infected samples. Significant histological lesions were detected in cecal and CT tissues of CcK colonized poults at 1 and 3 dpi, respectively. RNAseq analysis identified 250 differentially expressed genes (DEG) in CT from CcK colonized poults at 3 dpi, of which 194 were upregulated and 56 were downregulated. From the DEG, 9 significantly enriched biological pathways were identified, including platelet aggregation, response to oxidative stress and negative regulation of oxidative stress-induced intrinsic apoptotic signaling pathway. These data suggest that C. coli induced an acute inflammatory response in the intestinal tract of poults, and that platelet aggregation and oxidative stress in the CT may affect the turkey's ability to resist Campylobacter colonization. These findings will help to develop and test Campylobacter mitigation strategies to promote food safety in commercial turkeys.

From Species to Regional and Local Specialization of Intestinal Macrophages

Initially intended for nutrient uptake, phagocytosis represents a central mechanism of debris removal and host defense against invading pathogens through the entire animal kingdom. In vertebrates and also many invertebrates, macrophages (MFs) and MF-like cells (e.g., coelomocytes and hemocytes) are professional phagocytic cells that seed tissues to maintain homeostasis through pathogen killing, efferocytosis and tissue shaping, repair, and remodeling. Some MF functions are common to all species and tissues, whereas others are specific to their homing tissue. Indeed, shaped by their microenvironment, MFs become adapted to perform particular functions, highlighting their great plasticity and giving rise to high population diversity. Interestingly, the gut displays several anatomic and functional compartments with large pools of strikingly diversified MF populations. This review focuses on recent advances on intestinal MFs in several species, which have allowed to infer their specificity and functions.

The effects of dietary supplementation with lotus leaf extract on the immune response and intestinal microbiota composition of broiler chickens

This study aimed to assess the effect of lotus leaf extract (LLE) on the immune response and intestinal microbiota composition of broiler chickens. One-day-old birds were assigned to 7 treatments. Two maize-based control diets were each given with or without 50 mg/kg chlortetracycline (antibiotics and blank control groups, respectively). Five experimental diets were each given with 1.0, 2.5, 5.0, 7.5, or 10.0 g/kg LLE. Average daily weight gain (ADG) was assessed, and the immune organ index was calculated. Serum cytokine and immunoglobulin levels were determined, and intestinal microbiota composition was analyzed via high-throughput sequencing of the 16S rRNA gene. Results showed that in the LLE5 group, ADG was higher than that of the antibiotics and blank control groups (P < 0.05) from d 7 to 21, the thymus index at d14, spleen index at d 21, and bursa index at d 14 and 21 were increased markedly (P < 0.05). In the LLE5 and LLE7.5 groups, serum total IgG and sIgA concentrations were higher than those of the antibiotics and blank control groups (P < 0.05) at d 7 and higher than those of the antibiotics group (P < 0.05) at d 14. No significant effect was observed for interferon-gamma concentrations between the antibiotics and LLE5 or LLE7.5 groups; compared with the antibiotics group, IL2 concentrations were increased in the LLE5 group at d 7 and in the LLE7.5 group at d 21 (P < 0.05). 16s rRNA sequencing analysis revealed that there were 1,704, 232, and 4,814 operational taxonomic unit in the blank control group, antibiotics group, and LLE groups, respectively. The intestinal microbiota consisted mainly of Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes (>95%) at the phylum level; at the family level, the abundance of Clostridiaceae and Bacteroidales S24-7 was increased, whereas that of Peptostreptococcaceae was reduced in LLE5 group (P < 0.05). These findings suggest that LLE may be a good source of prebiotics, helping to modulate the immune response and boost the levels of beneficial bacteria.