This observational study will be prospectively conducted in the CRCM of Montpellier University Hospital. The main objective of this study is to evaluate the effectiveness of immunological assays based on the enumeration of T lymphocyte directed against Aspergillus fumigatus to identify cases of aspergillus infection/bronchitis in cystic fibrosis outpatients.
One hundred twenty patients over 15 years will be included during a 12 months period. Patients will be tested for A. fumigatus carriage and immunization based on recommended biological assays and clinical signs (culture, anti-aspergillus IgG, total and specific IgE) and tests recently proposed (PCR et ELISA galactomannan on sputum samples, Baxter et al, J Allergy Clin Immunol. 2013). T-lymphocytes directed against A. fumigatus antigens will be enumerated by using ELISpot assays developed in our laboratory. Cut-off values offering the the best sensitivity/specificity ratio will be established using ROC-curve analysis. This ROC curve will be established regarding the Aspergillus infection/bronchitis group (positive for culture or PCR and galactomannan) versus the negative groupe (negative for IgG or IgE and negative for A. fumigatus in the sputum). The potential input of Baxter et al classification will be also evaluated on clinical, functional respiratory, biological and imagery characteristics in regard to the clinical conclusion.
Analysis of the anti-aspergillus T-effector response in blood evidences the adaptive cellular response due to antigen exposure at time of collection and should be view as a snapshot of the immune response. This immune cellular response will provide a strong evidence of the infectious process caused by A. fumigatus in patients with cystic fibrosis. By contrast, the detection of moisture components into sputum (by PCR and galactomannans ELISA) or the level of anti-aspergillus antibodies in blood (IgG or anti-aspergillus IgE) may be the consequence to colonization or a previous immunization, respectively.
Anti-aspergillus T lymphocyte assays may be useful to identify Aspergillus infection/bronchitis group in cystic fibrosis patients. We expect a strong anti-aspergillus T-cells response in the aspergillus infection/bronchitis group and a weak response in the negative group and during a colonization, previous immunization or allergy without infection.
Commercials assays used for the diagnosis of Aspergillus infection/bronchitis suffer from an insufficient sensitivity and specificity to provide a clear indication for initiation of anti-fungal treatment in cystic fibrosis patients.
The validation of biological tests and cut-off values in patients with cystic fibrosis is necessary for further therapeutic studies. The combination of immunological and mycological tests, including a test based on anti-aspergillus T-cell response, will need to be evaluated for medical and economic benefits in a future multicentric, prospective and randomized study.