Study: NCT05042830

Intervention type: PROCEDURE
Group type: PLACEBO_COMPARATOR
Intervention: Blood sampling
Description: Blood samples will be taken by puncture of the antecubital vein for peripheral blood mononuclear cells (PBMCs) isolation, cytokines measurement, and flow cytometry analysis

Intervention type: PROCEDURE
Group type: ACTIVE_COMPARATOR
Intervention: Nasal biopsies
Description: Nasal biopsies will be taken from the lower fringe of the inferior turbinate, approximately 1-2cm from the anterior curved edge for RNA sequencing and confocal microscopy staining

Intervention type: PROCEDURE
Group type: PLACEBO_COMPARATOR
Intervention: Nasal biopsies
Description: Nasal biopsies will be taken from the lower fringe of the inferior turbinate, approximately 1-2cm from the anterior curved edge for RNA sequencing and confocal microscopy staining

Intervention type: BIOLOGICAL
Group type: ACTIVE_COMPARATOR
Intervention: Nasal specimen collection
Description: Nasal specimen collection will be conducted. Nasosorption FXi/PU (containing a synthetic absorptive matrix (SAM)) will be obtained.

Intervention type: BIOLOGICAL
Group type: PLACEBO_COMPARATOR
Intervention: Nasal specimen collection
Description: Nasal specimen collection will be conducted. Nasosorption FXi/PU (containing a synthetic absorptive matrix (SAM)) will be obtained.

Intervention type: PROCEDURE
Group type: ACTIVE_COMPARATOR
Intervention: Mucosal RNA sampling
Description: A 10 cm nasal curette will be used (Rhino-Probe, Arlington Scientific, USA). The curette is brought to lie against the mid-inferior portion of the inferior turbinate under direct visualisation. The curette is rubbed against the mucosal surface, going outwards. To ensure successful sample acquisition, this motion will be repeated 2-3 times

Intervention type: PROCEDURE
Group type: PLACEBO_COMPARATOR
Intervention: Mucosal RNA sampling
Description: A 10 cm nasal curette will be used (Rhino-Probe, Arlington Scientific, USA). The curette is brought to lie against the mid-inferior portion of the inferior turbinate under direct visualisation. The curette is rubbed against the mucosal surface, going outwards. To ensure successful sample acquisition, this motion will be repeated 2-3 times

Intervention type: PROCEDURE
Group type: ACTIVE_COMPARATOR
Intervention: Intranasal challenge
Description: The extract of birch pollen (Allergopharma, Vienna, Austria) will be freshly diluted in a 0.9 percent sterile sodium chloride solution and administered by means of a metered pump. The allergen will be administered supplying 15 μl per puff to both nostrils. Azelastine nasal spray or desloratadine 5mg will be given if the patient suffers from nasal or eye symptoms after the challenge. Equivalent amount of saline without allergens will be given to the control group.

Intervention type: PROCEDURE
Group type: PLACEBO_COMPARATOR
Intervention: Intranasal challenge
Description: The extract of birch pollen (Allergopharma, Vienna, Austria) will be freshly diluted in a 0.9 percent sterile sodium chloride solution and administered by means of a metered pump. The allergen will be administered supplying 15 μl per puff to both nostrils. Azelastine nasal spray or desloratadine 5mg will be given if the patient suffers from nasal or eye symptoms after the challenge. Equivalent amount of saline without allergens will be given to the control group.

Intervention type: PROCEDURE
Group type: ACTIVE_COMPARATOR
Intervention: Skin prick test
Description: In order to evaluate the patient's sensitization profile at the screening visit, a regular skin prick test will be conducted with commercial birch pollen extract and a panel of allergens used in routine diagnosis in the allergy clinic of the ear, nose, and throat (ENT) department.~Titrated skin prick test: Titrated skin prick test (SPT) to birch pollen extract is conducted by using increasing dilutions up to 1:100 000. As a result, it is possible to determine the lowest concentration that leads in a skin reaction.

Intervention type: PROCEDURE
Group type: PLACEBO_COMPARATOR
Intervention: Skin prick test
Description: In order to evaluate the patient's sensitization profile at the screening visit, a regular skin prick test will be conducted with commercial birch pollen extract and a panel of allergens used in routine diagnosis in the allergy clinic of the ear, nose, and throat (ENT) department.~Titrated skin prick test: Titrated skin prick test (SPT) to birch pollen extract is conducted by using increasing dilutions up to 1:100 000. As a result, it is possible to determine the lowest concentration that leads in a skin reaction.

Intervention type: PROCEDURE
Group type: ACTIVE_COMPARATOR
Intervention: Peak Nasal Inspiratory Flow (PNIF)
Description: The functionality and convenience of the PNIF presents a rare opportunity to rapidly obtain objective measurements of nasal peak inspiratory flow. It was also validated during other nasal allergen challenge as a study tool

Intervention type: PROCEDURE
Group type: PLACEBO_COMPARATOR
Intervention: Peak Nasal Inspiratory Flow (PNIF)
Description: The functionality and convenience of the PNIF presents a rare opportunity to rapidly obtain objective measurements of nasal peak inspiratory flow. It was also validated during other nasal allergen challenge as a study tool

Intervention type: BIOLOGICAL
Group type: ACTIVE_COMPARATOR
Intervention: Pregnancy test
Description: In female patients, a regular urine pregnancy test will rule out pregnancy. The test will be conducted at the screening visit before the first skin prick test and then once a month afterwards.

Intervention type: BIOLOGICAL
Group type: PLACEBO_COMPARATOR
Intervention: Pregnancy test
Description: In female patients, a regular urine pregnancy test will rule out pregnancy. The test will be conducted at the screening visit before the first skin prick test and then once a month afterwards.