Allergenicity of Camel Milk

BACKGROUND

Food allergy is a disease which prevalence is increasing over time. There are eight main allergens responsible for food allergy and this are: peanuts, tree nuts, egg, fish, shellfish, cow’s milk, soya and wheat. Cow’s milk is the main allergen affecting infants and small children. Cow’s milk allergy (CMA) affects 0.5-3.8% of all infants and small children and while some outgrow CMA over time,others keep it lifelong. Breastfeeding should always be the first choice for infants feeding.However, sometimes it is not possible or not chosen as a feeding option. When an infant suffers from CMA and cannot be exclusively breastfed, there is a need to use hypoallergenic infant formula.

In this PhD project a literature review was first performed in order to gain an overview on the present and potential, future infant formulas for CMA management and prevention (Manuscript I). Alternative sources of proteins in infant formula production are needed due to the climate change and growing population. Plant based proteins gained an interest mainly due to their vegan status and potential lower allergenicity. Mammalian milks such as goat, sheep, donkey, horse and camel have drawn an attention due to their potential of low cross-reactivity with cow’s milk proteins. Camel milk is one of mammalian milk gaining an interest for its usability as a protein source in the production of infant formula for CMA management and prevention due to the lack of β-lactoglobulin (BLG) one of the major allergen in cow’s milk and also due to the low homology with cow’s milk proteins. Yet, there is still a lack of solid scientific evidences on how camel milk is tolerated by cow’s milk allergic individuals, how processing such as enzyme hydrolysis and heat treatment influence camel milk proteins immunogenicity, sensitising capacity and cross-reactivity with cow’s milk proteins as well as whether camel milk proteins could drive tolerance to cow’s milk proteins.

AIMS AND METHODS

The aims of this project were to evaluate (1) immunogenicity, sensitising capacity and cross-reactivity of intact cow’s and camel milk (Manuscript II*), (2) how processing such as enzymehydrolysis and heat treatment influence cow’s and camel milk proteins physicochemical characteristics (Manuscript III) and (3) further immunogenicity, sensitising capacity and cross-reactivity of cow’s and camel milk processed products (Manuscript IV), (4) whether intact camel milk could prevent CMA as well as whether intact cow’s milk could prevent camel milk allergy (Manuscript V). Finally, the aim of this project was to evaluate (5) how children with CMA reacted towards intact and processed cow’s and camel milk (Manuscript VI).

Cow’s and camel milk proteins physicochemical characteristics before and after processing were evaluated and compared my means of different analytical methods such as electrophoresis and chromatography. Evaluation of immunogenicity, sensitising capacity, cross-reactivity as well as preventive capacity of cow’s and camel milk products were evaluated in Brown Norway rat models and further analysed by means of humoral and cellular immune responses. Reactivity towards cow’s and camel milk products in children with confirmed CMA was evaluated by assessing the level antibodies in their serum/plasma samples.

*Manuscript II includes the results from the animal experiment performed before the beginning of this PhD project. The animal experiment was part of Natalia’s master project and most of the samples were analysed during master project duration. However, some analysis were performed and finalised at the beginning of this PhD project. Moreover, whole manuscript was written, submitted and accepted during this PhD project.

RESULTS

Results presented in Manuscript II showed that the inherent immunogenicity and sensitising capacity of intact cow’s and camel milk was similar. Yet, they showed a low cross-reactivity, being lower between caseins in comparison to whey proteins.

Results presented in Manuscript III showed that cow’s and camel milk behaved differently under enzyme hydrolysis and heat treatment. For both processing methods differences in protein and other components composition and lack of BLG in camel milk played an important role in inducing distinct modifications between cow’s and camel milk.

Results presented in Manuscript IV showed that heat treatment and enzyme hydrolysis influenced cow’s and camel milk immunogenicity, sensitising capacity, reactivity and its specificity in different ways. In addition heat treatment and enzyme hydrolysis showed to further decrease cross-reactivity between cow’s and camel milk proteins.

Results presented in Manuscript V showed that camel milk could not prevent CMA while cow’s milk showed to have a low and transient capacity to prevent camel milk allergy. Low cross-tolerogenic capacity between cow’s and camel milk proteins was suggested to be due to their low protein homology.

Results presented in Manuscript VI were in line with results obtained based on animal study in Manuscript IV and showed that cow’s and camel milk had a low cross-reactivity in children with CMA which could be even decreased by processing methods such as enzyme hydrolysis and perhaps heat treatment.

CONCLUSIONS AND PERSPECTIVES

In conclusion, the results showed that camel milk is a promising source of proteins in infant formula for CMA management. Processing such as enzyme hydrolysis and heat treatment showed to be efficient methods to improve usefulness of camel milk in CMA management.However, the results showed that camel milk is not a good candidate for CMA prevention, due to the lack of cross-tolerance, indicating that if one product is sufficient for CMA management, it would probably not be for CMA prevention.