Given that dogs are widely regarded as ‘man’s best friend’, it makes sense that we are constantly striving to find ways to improve canine health. One method that has been – and is still being – explored is the use of immunotherapy, which uses a dog’s own immune system to fight health issues, such as allergies and cancer.
Although immunotherapy for dogs is still lagging slightly behind compared to human immunotherapy, it is still a major topic of interest within veterinary medicine and is an area that is very much advancing, with a number of research studies being conducted around dog immunotherapy, particularly with regards to treating cancer.
And it’s not just studies that are being conducted; there are already a few established immunotherapies that are commonly used by veterinarians, such as allergy shots to tackle environmental allergies in dogs, and even vaccines to treat certain types of canine cancers.
Battling allergies in dogs with immunotherapy
The idea of using immunotherapy in order to tackle allergies is not only reserved to humans. Immunotherapy for dogs has been around for several decades, and it is generally considered a very successful method, with around 75% of dogs showing an improvement in symptoms, and some even being completely cured by the treatment.
Dog allergies generally fall into one of three categories: flea allergies, food allergies or environmental allergies. Flea and food allergies, once identified, are fairly straightforward to treat; if your dog has fleas, then you need to use a flea treatment to get rid of the fleas, and if your dog has a food allergy, you need to try and avoid the food that is causing the flare-ups.
Environmental allergies, however – affecting between 10% and 20% of dogs – are more difficult to deal with because they involve a reaction to outside factors such as grasses, pollens and insects, most of which cannot be removed from a dog’s natural environment.
This is where immunotherapy can be extremely helpful, and can help to relieve your dog’s symptoms, the most common of which is very itchy skin that is either localized or generalized.
The treatment is given to dogs in the form of ‘allergy shots’ – officially called allergen-specific immunotherapy – whereby small portions of the identified allergen that is causing the reaction is administered to the dog on a regular basis, with a gradual increase in dose over time, until the dog’s immune system eventually stops overreacting to that allergen.
Although the frequency of shots can vary in each case, they are generally given every other day initially, before being decreased to once or twice weekly, and it can take several months before your dog feels the benefits of the shots.
Fighting canine cancer: Vaccines and CAR-T cell therapy
As well as being used to treat allergies, immunotherapy can also be used to treat cancer in dogs, just as in humans.
“Immunotherapy to treat allergic diseases in dogs has been around for several decades now, but there has been a surge of interest and research aimed at harnessing the power of the immune system to treat cancer in dogs,” commented Kelly Diehl, veterinarian and senior director of science communication at Morris Animal Foundation.
This is significant because cancer is common in dogs, and it is thought that more than 50% of dogs over the age of ten will develop some form of cancer. The most common cancers are melanomas and mast cell tumors – types of skin cancers, lymphomas, and bone cancers.
According to Jethro Forbes, assistant clinical professor of emergency and critical care at the Cornell University College of Veterinary Medicine, immunotherapy is already currently being used to treat at least two different cancers in dogs. These have been effective, showing longer survival times compared to standard treatments.
One of these immunotherapies is for the treatment of osteosarcoma – a malignant tumor of the bone – and comes in the form of a cancer vaccine.
“Osteosarcoma tumor cells from the individual canine patient are harvested and made into a vaccine to stimulate the dog’s immune production of T-cells. The T-cells are then harvested and expanded ex vivo for administration to the dog. Other osteosarcoma treatment with a listeria derived vaccine is also well established,” explained Forbes.
There is also a vaccine available for oral melanoma, which works by alerting the immune system to the presence of melanoma proteins to help it fight the cancer cells. It is intended to be used in combination with surgery and radiation to treat the initial tumor.
Furthermore, after the success it has had in humans, CAR-T cell therapy is also being explored in veterinary medicine, and, although not yet approved as a treatment option, there are several clinical investigations underway, particularly for blood-based cancers, such as B-cell lymphoma and B-cell leukemia.
Limitations of using immunotherapy to treat cancer in dogs
Despite the established cancer vaccines and research around CAR-T cell therapy, there are some limitations when it comes to using immunotherapy to treat cancer in dogs.
One of these is that much of the information on immunotherapy in dogs has been taken from human studies, meaning the canine immune system itself has perhaps not been as extensively studied as it needs to be in order to develop more successful canine immunotherapies.
For example, lymphocytes – a type of white blood cell that helps the body’s immune system to fight off cancer and foreign viruses and bacteria – in the canine immune system have not yet been fully characterized, making it more difficult to predict which dogs and which cancers are most likely to respond to immunotherapy treatment.
And, because cancers in dogs have not been as extensively identified as human cancers in terms of appearance and genetics, it also makes it difficult to create unique, personalized immunotherapies that would be appropriate for an individual dog’s tumor.
Targeting autoimmune diseases
Although not as extensive, there is also research being conducted around using immunotherapy for dogs to treat certain autoimmune diseases.
“One of the many exciting immunotherapy techniques in canine medicine involves the removal of the effectors of immune destruction of the patient’s own red blood cells, a disease called Immune Mediated Hemolytic Anemia. This autoimmune disease is primarily treated with medication to suppress the immune system. However, some cases are severe or refractory to treatments and the medications take time to work,” said Forbes.
“Through the use of an extracorporeal (outside the body) therapy called therapeutic plasmapheresis (or plasma exchange), we can actually remove the autoantibodies responsible for destruction of red blood cells through blood purification. We then return the blood to the patient.”
Forbes said that they currently offer this therapy at Cornell University College of Veterinary Medicine, and that it could also be used to treat other immune mediated conditions, such as myasthenia gravis.
More progress to come
In recent years, immunotherapy for dogs has come a few steps closer to immunotherapy in humans in terms of research, but a lot more still needs to be done to catch up.
As Forbes pointed out, the cost of development for dog treatments is not as robustly funded as in human medicine, and the cost of actually being able to receive treatment is a major issue, as many dogs do not have insurance.
Having said that, it seems like more money is slowly being poured into research around immunotherapy for dogs. For example, as Diehl pointed out, in 2018, Morris Animal Foundation took the step of awarding a $775,000 grant to Dr. Nicola Mason at the University of Pennsylvania’s School of Veterinary Medicine to test a vaccine that could improve longevity and quality of life for dogs with osteosarcoma.
“I think we’re going to see a lot more immunotherapy-based treatments in dogs over the next decade. Partly, this is due to more veterinary scientists simply interested in this topic and partly because, I think, that as dogs are recognized as good study models for some human diseases, more financial support and interest in studying therapies that have translational potential for people will result in more funding for veterinary scientists,” said Diehl.
