A research team at UCLA has developed a possible way to impart long-term relief from allergies by inducing an active state of immune tolerance, according to a press release from the university.
The technology uses a nanoparticle — a particle so small that it’s measured on the scale of billionths of a meter — to deliver proteins to specific cells in the liver. Those proteins may trigger an allergic response in other organs in the body, but in the liver, they cause the targeted cells to activate a tolerant immune response that switches the allergic response off.
A report on the research, published in ACS Nano, indicates that the platform is effective in preventing allergic reactions to an egg protein when ingested or inhaled. The UCLA researchers also showed that delivering a single piece of a protein that triggers allergies is sufficient to ameliorate the allergic reaction.
The liver is an immune-privileged organ, meaning that it is programmed not to respond to foreign proteins called antigens, which can cause allergic or anaphylactic responses elsewhere in the body. The platform developed by Nel and his colleagues spurs the liver to produce regulatory T cells, cells in the immune system that can go everywhere in the body, to calm allergic responses to food allergens.
In their test, the UCLA researchers pretreated groups of mice with two injections one week apart to compare the liver-targeting nanoparticles with several versions of the Harvard–MIT approach. The mice were then sensitized to an egg protein in a way that would cause it to trigger asthma-like symptoms under normal circumstances. Starting four weeks after the second injection, the mice were exposed to the allergen through inhalation.
The scientists found that the liver-targeting nanoparticle containing the egg allergen generated regulatory T cells that are programmed to suppress the allergic response to the egg protein — and that it was just as effective as the Harvard–MIT approach in reducing allergic inflammation in the lungs.
In a second experiment using mice, the team found that delivering certain fragments of the egg protein with the liver-targeting nanoparticle enhanced immune tolerance, and it did so better than targeted delivery of the entire protein.
A third experiment used a mouse model for anaphylaxis triggered by ingesting the same egg protein. The researchers compared mice with the food allergy that received no treatment, mice that were pretreated with injections of the nanoparticle containing the entire egg protein and allergic mice pretreated with injections of one particular fragment of the protein. Mice that received the nanoparticles containing the whole protein and those that received the nanoparticle containing the fragment displayed a dramatic reduction in life-threatening responses to the allergen, such as a collapse in blood circulation causing their body temperature to drop.
