The surveillance of the pollen content in the air is crucial for allergic patients and physicians. It helps these latter to determine the diagnosis of pollinosis, to adapt the treatments and to advise eviction measures during high-risk periods. The methodology that is currently used by the aerobiological surveillance networks relies on the identification of the pollen types by microscopy. However, this technique presents certain limitations among which the impossibility to distinguish the pollen of certain allergenic plants. This project aims to develop new alternative techniques that would allow the identification and quantification of the pollen based on its DNA.
The standard airborne pollen counting method consists of the manual identification of pollen grains by the visual recognition of specific morphologic characteristics by light microscopy, which is time-consuming and requires trained personnel. The errors due to this pollen counting procedure range from 10% to over 30%, depending on pollen abundance, sample size, and the experience of the human counter. Moreover, several pollen taxa from the same family are not distinguishable by this technique. This is the case for instance with grass pollen grains (from the Poaceae family) or with Parietaria spp. pollen grains which have the same morphological features than the Urtica spp. pollen grains (from the Urticaceae family).
Read more about the Allerpol project
Nowadays, the possibility of studying genomic DNA can help aerobiologists to overcome the limitations of the traditional approaches for the specific identification of pollen taxa at the level of the genus or of the species. With the advent of quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) and digital droplet PCR (ddPCR), the detection and quantification of specific target DNA can be elaborated in relatively rapid, sensitive, and accurate assays. Interestingly, digital droplet PCR offers highly precise and absolute quantification without requiring a calibration curve.
This project aims to evaluate the feasibility of these molecular techniques as an alternative for optical analysis for the detection and quantification of an enlarged allergenic pollen taxa set. In extension, this project is expected to deliver a complete and calibrated method for the detection of airborne Parietaria spp. pollen by both qRT-PCR and ddPCR techniques. Accuracy and cost-effectiveness of both PCR techniques will be compared and results will be described in a peer-reviewed publication. Overall, this method represents a proof-of-concept for further detection of other pollen taxa.
The global interest in developing new techniques for the genetic surveillance of the air content is to overcome the current limitations related to the microscopy-based aerobiological monitoring. For instance, this new tool would allow defining and characterizing the pollen season of the pellitory, which is considered as one of the most important aeroallergens in the Mediterranean area. The timing of its season is currently unknown in Belgium because of a masking effect due to the pollen season of the nettle. In terms of public health, the aerobiological surveillance of the pellitory would allow to evaluate the potential risk of developing respiratory allergy in several Belgian areas in which large populations of this plant were locally reported (in urban areas such as along the canals in Bruges, along the Meuse riverbanks in Namur, etc.).