That was the key finding of a study conducted after researchers were able to create transgenic rice which contained the entire molecules of major Japanese cedar pollen allergens.
The study, led by Kochi Medical School, tested the effect of the rice vaccine on mice that had been injected with Japanese cedar pollen and administered eye drops containing pollen.
The researchers found that the vaccine "suppressed established pollen-induced allergic conjunctivitis in mice”.
Compared to a previous study, where the prophylactic feeding of transgenic rice had a “protective effect against the development of allergic conjunctivitis in mice”, the oral immunotherapy used in this study led to more significant results.
These results have potentially positive implications for people in Asia, as rice is a staple food in most Asian countries and is therefore a “potential route for antigen delivery that could improve adherence to oral immunotherapy in this region of the world”.
Still, the study also noted that the “mechanisms of immune suppression by immunotherapy likely depend on various factors such as the duration, frequency, dose, and specificity of antigen administration”, and that further study is needed to establish "a clear immunologic or other effect as a marker of clinical efficacy for oral immunisation with transgenic rice”.
It further acknowledged that a disadvantage of oral therapy is the “degradation of antigen by enzymes in the gastrointestinal tract”. However, the transgenic rice seeds’ modified antigens are very resistant to enzymatic degradation thanks to their deposition in protein bodies, meaning the antigens are effectively delivered to the gut.
Another practical advantage of transgenic rice-based immunotherapy is that the antigens in the rice grains are non-toxic, edible, and stable at room temperature for several years.
The study concluded that since “oral administration of transgenic rice seeds expressing hypoallergenic allergens ameliorated allergic conjunctivitis…such a rice-based edible vaccine is potentially both safe and effective for oral immunotherapy in individuals with allergic conjunctivitis”.
Source: Allergology International
“Efficacy of oral immunotherapy with a rice-based edible vaccine containing hypoallergenic Japanese cedar pollen allergens for treatment of established allergic conjunctivitis in mice”
Authors: Ken Fukuda, et al.