NO2 air pollution increases allergenicity in ragweed pollen

Pollen of the common ragweed (Ambrosia artemisiifolia) has higher concentrations of allergen when the plant is exposed to NO2 exhaust gases, according to findings of scientists of Helmholtz Zentrum München. In addition, the study published in the journal Plant, Cell & Environment indicates the presence of a possible new allergen in the plant.

Together with the Research Unit Protein Science and the Institute for Environmental Medicine of Technische Universität München as well as the research consortium UNIKA-T and the Christine Kühne - Center for Allergy Research and Education, researchers of the Institute of Biochemical Plant Pathology (BIOP) studied how nitrogen oxides affect the pollen of the plant. Specifically, they fumigated the plants with various concentrations of NO2, which e.g. is generated during combustion processes of fuel. "Our data showed that the stress on the plant caused by NO2 modulated the protein composition of the pollen," said first author Dr. Feng Zhao. "Different isoforms of the known allergen Amb a 1 were significantly elevated." In addition, the scientists observed that the pollen from NO2 treated plants have a significantly increased binding capacity to specific IgE antibodies of individuals allergic to Ambrosia. This is often the beginning of an allergic reaction in humans.

Previously unknown allergen in Ambrosia

The plant researchers made another striking discovery in the pollen of the fumigated plants: During their investigations they identified a protein that was present in particular when NO2 levels were elevated. This protein was not previously known to be an allergen in Ambrosia, and it has a strong similarity with a protein from a rubber tree. In this context, it was previously described as an allergen whose effect was also known in fungi and other plants. Further experiments related to this topic are currently being planned.

Stress makes pollen aggressive

"Ultimately, it can be expected that the already aggressive Ambrosia pollen will become even more allergenic in the future due to air pollution," said study leader Dr. Ulrike Frank, summarizing the results. She and her team at BIOP have long been conducting research on the plant, which probably once came to Europe in imported birdseed. Now it is widely dispersed here due to climate change. Ragweed pollen is very aggressive; in the U.S. it is now the main cause of hay fever and other allergies. Since Ambrosia does not bloom until late summer, it thus lengthens the "season" for allergy sufferers.

"After studies have already shown that Ambrosia growing along highways is clearly more allergenic than Ambrosia plants growing away from road traffic, we could provide a reason for this," said Frank. "Since in nature and along roads hundreds of parameters could play a role, until now the situation was not entirely clear." In future studies in collaboration with UNIKA-T and the Christine Kühne - Center for Allergy Research and Education, the scientists want to show that pollen only treated with NO2 can also elicit stronger in vivo reactions.