In the lungs of
cystic fibrosis (CF) patients, Pseudomonas aeruginosa commonly causes
chronic infections. It has been shown that the P. aeruginosa quorum sensing (QS) system controls the expression of
virulence factors during invasion and
infection to host cells. PvdQ is an
acyl-homoserine lactone (AHL)
acylase able to degrade the signal molecule of P. aeruginosa QS. The role of PvdQ in inhibiting the QS and its successive virulence determinants has been established in in vitro as well as in in vivo, the latter in a Caenorabdhitis elegans model. For the treatment of pulmonary P. aeruginosa
infections, we propose that PvdQ can be best administered directly to the lungs of the patients as a dry
powder because this is expected to give specific advantages in delivery as compared to nebulizing. Therefore in this study we investigated the production of a PvdQ
powder by spray-freeze drying using
mannitol,
trehalose and
inulin as
excipient. The activity of PvdQ in the
powder was determined immediately after production and after subsequent storage during 4 weeks at 20°C and 55°C. We found that the enzymatic activity of PvdQ is fully maintained during spray-freeze drying using
mannitol,
trehalose or
inulin as
excipient. However,
mannitol was not able to stabilize the
protein during storage, while PvdQ incorporated in
trehalose or
inulin was fully stabilized even during storage at 55°C for at least 4 weeks. The poor stabilizing capacities of
mannitol during storage could be related to its crystalline nature while the excellent stabilizing capacities of
trehalose and
inulin during storage could be related to their amorphous nature. The
trehalose and
inulin-based particles consisted of porous spheres with a volume average aerodynamical diameter of ∼1.8 μm implying that they are suitable for pulmonary delivery. This is the first study in which an AHL-degrading
enzyme is processed into spray-freeze-dried
powder suitable for inhalation.