Innate Immunomodulation in Food Animals: Evidence for Trained Immunity?

Antimicrobial resistance (AMR) is a significant problem in health care, animal health, and food safety. To limit AMR, there is a need for alternatives to antibiotics to enhance disease resistance and support judicious antibiotic usage in animals and humans. Immunomodulation is a promising strategy to enhance disease resistance without antibiotics in food animals. One rapidly evolving field of immunomodulation is innate memory in which innate immune cells undergo epigenetic changes of chromatin remodeling and metabolic reprogramming upon a priming event that results in either enhanced or suppressed responsiveness to secondary stimuli (training or tolerance, respectively). Exposure to live agents such as bacille Calmette-Guerin (BCG) or microbe-derived products such as LPS or yeast cell wall ß-glucans can reprogram or "train" the innate immune system. Over the last decade, significant advancements increased our understanding of innate training in humans and rodent models, and strategies are being developed to specifically target or regulate innate memory. In veterinary species, the concept of enhancing the innate immune system is not new; however, there are few available studies which have purposefully investigated innate training as it has been defined in human literature. The development of targeted approaches to engage innate training in food animals, with the practical goal of enhancing the capacity to limit disease without the use of antibiotics, is an area which deserves attention. In this review, we provide an overview of innate immunomodulation and memory, and the mechanisms which regulate this long-term functional reprogramming in other animals (e.g., humans, rodents). We focus on studies describing innate training, or similar phenomenon (often referred to as heterologous or non-specific protection), in cattle, sheep, goats, swine, poultry, and fish species; and discuss the potential benefits and shortcomings of engaging innate training for enhancing disease resistance.

Modulation of post-hatch growth and immunity through in ovo supplemented nutrients in broiler chickens

BACKGROUND

Early post-hatch growth and immunity were assessed through in ovo supplementation of nutrients: amino acids (AA), trace elements (TE), fatty acids and vitamins (FAV) grouped under humoral immunity (HI) or cell-mediated immunity (CMI) on the 18th day of incubation at the broad end of the egg using a 25 mm needle.

RESULTS

Hatchability in AA groups was better than TE and FAV groups. CMI groups had better hatchability than HI groups. AA and TE groups had higher chick-to-egg weight ratio (P < 0.01) than the FAV group. At 3 weeks of age, a higher body weight (P < 0.01) was recorded in AA for CMI, TE for HI and FAV for HI groups. FAV-injected chicks had a higher bursa weight at hatch, but TE chicks had higher thymus weight at the 3rd week of age. Humoral immune response was not different in in ovo injected chicks compared to control. CMI was higher (P < 0.01) in AA for CMI, TE for CMI and FAV for CMI or HI nutrient-injected chicks.

CONCLUSIONS

In ovo injection of AA for CMI and TE for HI may accelerate growth of broiler chickens. In ovo injection of AA, TE or FAV may modulate CMI in chicks.