August 1, 2018

Researcher suggests stimulating animal immune system as alternative to antibiotic use

A research associate from Utrecht University in The Netherlands has highlighted a "promising approach" to improve an animal's innate immune system and thus raise the threshold above which infections occur, as a way of reducing reliance on antibiotics.
 

According to Dr. Albert van Dijk of the Faculty of Veterinary Medicine, the immune stimulants employed to enhance the immune system "do not directly kill the bacteria," and so will not result in resistance development.

"The potential of using immunoglobulins and host defense peptides to boost the immune system of livestock was presented by us and others during the second International Symposium on Alternatives to Antibiotics in Paris (2016) and extensively described in a recent review in Veterinary Research," Dr. van Dijk writes in a piece featured in BioMed Central.    

"Immunoglobulins (Igs) are antibodies that 'label' foreign bacteria for uptake and digestion (phagocytosis) by immune cells. Besides natural transfer and protection via breast milk, Igs can be used for passive immunisation of livestock. Licensed Ig-based products are already used to protect against bacterial infections, bacterial toxins and, for instance, West Nile virus in horses."

Dr. van Dijk then goes on to describe host defense peptides (HDPs), which are "small" - "<100 amino acids often positively charged peptides that act via multiple antimicrobial mechanisms and therefore have a low risk of inducing antimicrobial resistance."

"In addition to broad-spectrum antimicrobial activities (bacteria, fungi, parasites and viruses), HDPs have a capacity to modulate immune cells," Dr. van Dijk explains. Claiming that HDPs can be "used in different ways," he points out that feed additives - like short-chain fatty acids or probiotics - and breed selection or "transgene approaches" can help stimulate and improve "endogenous HDP expression."

"In addition, HDPs can be used as templates for development of new antimicrobials and immunomodulators, as vaccine adjuvants or as an adjunct to antibiotic therapies," he says.

Dr. van Dijk identifies the "in ovo immunomodulation in poultry" as an example of the "prophylactic use of HDPs in livestock to prevent infections."

"In chicken, in ovo HDP treatment was shown to reduce the mortality, the number of sick birds and the severity of illness caused by a bacterial infection. Postnatal prevention with HDP-derived 'IDRs' (Immune Defense Regulators) were effective against invasive and systemic bacterial infections in animal models," he elaborates.

"As an adjunct to antibiotic therapy, HDPs were shown to improve the clinical outcome in mouse models of tuberculosis, cerebral malaria and systemic bacterial infection."

Dr. van Dijk also states that his team's work has received "several patents."

"We continue to study the mechanisms of action of HDPs as immunomodulators and as vaccine adjuvants. In conclusion, innate host defense mechanisms offer new strategies to treat and prevent microbial infections and disease in animal husbandry," he says.

- BioMed Central