The 30th Annual Congress of the European Society and College of Veterinary Dermatology was held at the end of September in Dubrovnik, Croatia. Over 800 delegates working in the field attended and provided some interesting presentations and discussions on veterinary, and human, dermatology advances in diagnoses and treatments.
The congress was held over three days and each day was split into three streams; the Practical Programme, the Advanced Programme and the Cutting Edge Programme. This allowed delegates to select from a variety of subject areas and also at a level relevant to their interests. Canine, feline and equine topics were explored, as well as fascinating insights into the latest thoughts on human atopic dermatitis.
Avacta Animal Health were honoured to be chosen to present two short communications in the Cutting Edge Programme. These represented advances in understanding of both our environmental allergy panel and our food allergy panel. The presentation of cross-reactive carbohydrate determinants won the Dechra award for best laboratory study with an independent investigator at the congress.
Inhibition of canine serum IgE binding to cross-reactive carbohydrate determinants in environmental allergens – J.T. Bexley, N.J.Kingswell, R.E.Halliwell, T. Nuttall
What is the problem?
Cross-reactive carbohydrate determinants (CCDs) are glycoproteins found in pollens, insects and some molluscs, but not mammals, therefore are likely to be a source of immunogenicity. Antibodies to (CCDs) have been found in 30% of humans diagnosed with atopy. Human studies show that serology tests can be susceptible to the presence of anti-CCD antibodies creating a ‘false positive’ reaction and masking the true IgE hypersensitivity reactions. It is important to note that the clinical significance of anti-CCD antibodies has not yet been determined and they are thought to be non-pathogenic.
What we did?
Prevalence – are they present it dogs?
We selected 95 dogs that had shown a positive reaction to environmental allergens using the SensiTest assay and screened for antibodies to 3 CCD allergens; ascorbic acid from squashes, bromelain from pineapple and horseradish peroxidase. 73% of the samples showed anti-CCD IgE antibodies. 80% of the grass-pollen positive dogs were reactive to multiple pollen allergens (two or more) and 84% of these multi-pollen reactive dogs were also reactive to CCD allergens. Could this multi-pollen reactivity be due to the presence of anti-CCD antibodies?
Inhibition – can we block it in dogs?
We created a CCD-inhibiting solution and incubated dog serum samples with and without this blocking solution. We then looked at binding to CCD or grass-pollen allergens. Use of the CCD blocker removed all binding to the CCD allergens, reduced binding to bluegrass allergen by 80%, reduced binding to timothy grass allergens by 33%, but only reduced binding to mugwort allergen by 10% and had minimal impact on binding to house dust mite allergen.
This means that the presence of anti-CCD IgE antibodies could be the source of multi-pollen reactivity in dog serology tests and the use of a CCD-inhibitor solution could improve the specificity of testing. This would allow greater knowledge for avoidance or selection of immunotherapy for allergy to environmental allergens. Further work is now needed to establish the clinical relevance of this work.
IgE cross-reactivity in fish and chicken meats in dogs – J.T.Bexley, N.J.Kingswell, T. Olivry
What is the problem?
There is a growing interest in the evolutionary conservation of proteins in closely related or unrelated species. Thirty percent of humans with allergy to chicken are also allergic to fish. This is thought to be due to the presence of beta-enolase, aldolase and parvalbumin proteins found in both meats. This immunological cross-reactivity has not been previously shown in dogs.
What we did?
Initially we examined 1500 SensiTest results and performed two-by-two correlation analysis to look at cross-reactivity between chicken and white fish, chicken and salmon, and white fish and salmon. The results showed that all were highly significant meaning cross-reactivity or co-sensitisation.
We then selected dog serum samples with antibodies to at least one of chicken, white fish or salmon and showed that 49% had antibodies to all three allergens. We were able to inhibit this binding by incubating the sera with chicken, white fish or salmon extracts prior to repeating the ELISA analysis.
We ran the chicken, white fish and salmon extracts on a SDS gel and transferred onto a membrane. We then incubated this membrane with positive serum or negative serum. Positive serum revealed binding to 9 proteins in the chicken extract, 8 proteins in the white fish extract and 7 proteins in the salmon extract. There was no binding in the negative serum.
We cut out these proteins from the gel and performed mass-spectrometry analysis to show the proteins identity. This revealed that most of the proteins had cross-reactivity between the extracts and highly-conserved sequence identity. Most of the proteins identified are involved in glycolysis and have been shown to be allergens in humans.
We identified novel allergenic proteins present in chicken, white fish and salmon extracts that elicited IgE responses in dogs. Some of these are also allergens in food for humans. Whether any of these newly-identified IgE cross-reactive allergens are the cause of clinical allergy needs to be determined in dogs. This could impact upon diets and food preparations in dogs with food allergy and allow for more personalised allergy profiling.
‘Hot topics’ of the congress included; the effects of Staphylococcus on atopic dermatitis and possible future therapies, cross-reactivity in allergens, and potential new areas for therapeutic developments. There was a particular emphasis on best practice in general practice to ensure the correct diagnosis and best outcome for the patient.
In summary, the content of the seminars was varied enough to offer something for everyone and provided practical, straightforward guidance that could immediately be implemented in general practice to advance dermatology case work-ups. The atmosphere of the congress was extremely welcoming and there were social events that gave the opportunity to meet and mingle with the great and the good of the dermatology world. I would highly recommend attendance for anyone with an interest in dermatology and I hope to see some of you in Liverpool in September 2019!
Written by Nicola Kingswell– Head of Laboratory Operations
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