Long-term follow-up of nasal immunotherapy to Parietaria: clinical and local immunological effects

Summary Background Local nasal immunotherapy (LNIT) with extracts in powder has been detnonstrated clinically effective and devoid of side-effects in several controlled trials; nevertheless, no data concerning the long-term effects of LNIT are presently available. Methods In a recent double-blind, placebo-controlled study of LNIT to Parietaria pollen we observed, by means of specific nasal provocation test (SNPT) that LNIT is able to modify the local allergic inflammatory response. In the present study we followed up the same patients in open fashion for 2 further years. Results The results confirmed the clinical efficacy of LNIT and showed that it is strictly dependent on pre-seasonal administration: in fact, after LNIT discontinuation a clinical relapse was observed. A certain long-lasting protective effect on SNPT parameters (nasal symptoms and neutrophils infiltration) was also observed, whereas an increase of eosinophils count and ICAM-1 expression on nasal epithelial cells appeared as possible markers of clinical relapse. Conclusion The present study suggests that pre-seasonal LNIT can be taken in consideration in selected subjects as prophylactic treatment for pollen-induced rhinitis. In addition, the results obtained provide informations about the duration of clinical efficacy and add data about the local allergic inflammation and its modulation.