Abstract
BackgroundHydrolyzed diets are used in companion animals for the diagnosis and treatment of adverse food reaction. Similarly, hydrolyzed formulas are used in human infants with severe inflammatory bowel disease or milk allergy, and these must meet the standard of hypoallergenicity through rigorous testing. Unfortunately, no standards are currently applied to hydrolyzed veterinary therapeutic diets, and data for the immunogenicity of feline diets is also not available. Therefore, the main aim of this pilot study was to determine if ex-vivo whole blood stimulation assays could be used to characterize the cytokine response to hydrolyzed commercial diets in a small number of individual healthy immunotolerant cats. This approach has also been used to investigate cytokine production in response to cow milk protein in humans and currently similar studies do not exist in companion animals. Nine healthy cats previously eating the same basal diet were divided into groups and fed one of three hydrolyzed diets exclusively for 6 weeks. Heparinized whole blood was collected from each cat before and after the feeding trial. Ex-vivo whole blood stimulation assays were performed using crude extracts of the basal diet as a positive control, as this diet contained the same proteins present in the hydrolyzed diet but were intact, saline as a negative control, and each cat’s respective hydrolyzed diet. Supernatants were collected and analyzed for tumor necrosis factor-alpha, interleukin-10 (IL-10), and interleukin-4 using enzyme-linked immunosorbant assay.ResultsSeven cats produced detectable amounts of the anti-inflammatory cytokine IL-10 upon stimulation with the basal diet. Two cats produced detectable amounts of IL-10 upon stimulation with a hydrolyzed soy-based diet and one cat produced a detectable amount of IL-10 upon stimulation with a hydrolyzed chicken-based diet (>125 pg/mL).ConclusionsResults from this pilot study suggest that in some healthy immunotolerant cats, some hydrolyzed diets may elicit a similar cytokine response compared to their basal diet, which contained the same proteins intact. Therefore, animals may be able to recognize and react to some hydrolyzed forms of tolerated proteins, and may also suggest IL-10 as a target for investigation as a potential marker for dietary tolerance in cats, however further studies would be necessary to corroborate this. Further studies are also needed to determine if this would also be the same in immunologically naïve, sensitized and clinically hypersensitized cats.
Highlights
Hydrolyzed diets are used in companion animals for the diagnosis and treatment of adverse food reaction
The two remaining cats that did not produce detectable levels of IL-10 following consumption of their respective hydrolyzed diet produced Tumor necrosis factor (TNF)-alpha when stimulated with 50 μg/mL of the basal diet (65.8 pg/mL and 34.4 pg/mL respectively), but not on stimulation with 500 μg/mL of the basal diet
Whole blood was used in the stimulation assays rather than peripheral blood mononuclear cells (PBMCs) in order to mimic the natural environment of the cells, to prevent phenotypic changes that may occur with isolation of cells, and to reduce the volume of blood needed
Summary
Hydrolyzed diets are used in companion animals for the diagnosis and treatment of adverse food reaction. The main aim of this pilot study was to determine if ex-vivo whole blood stimulation assays could be used to characterize the cytokine response to hydrolyzed commercial diets in a small number of individual healthy immunotolerant cats. This approach has been used to investigate cytokine production in response to cow milk protein in humans and currently similar studies do not exist in companion animals. Likewise, hydrolyzed baby formulas are used commonly in infants with severe inflammatory bowel disease or cow milk allergy [3] These formulas must meet the standard of hypoallergenicity through testing using in vitro and in vivo animal models as well as clinical assessment [4, 5]. Studies are needed to verify the immunological potential of these diets
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