[Effect of rhDNase on the respiratory function and nutritional status of children and adolescents with mucoviscidosis]. / Effects de la rhDNase sur la fonction respiratoire et le statut nutritionnel de l'enfant et de l'adolescent atteints de mucoviscidose.

BACKGROUND: In 1994 we started recombinant human deoxyribonuclease (rhDNase) in every cystic fibrosis (CF) patient whatever his (her) clinical condition, provided they were aged more than 5 years and forced vital capacity (FVC) was > or = 40%. POPULATION AND METHODS: We reviewed retrospectively the effects of rhDNase in 69 CF children and adolescents during a 2-year follow-up. Patients (35 boys, 34 girls) received 2.5 mg of rhDNase once daily from a mean age of 8.5 years (range 5-16.4). Baseline spirometric values (% predicted) and nutritional status were as followed: FVC = 84.8 +/- 21.7; forced expiratory volume in 1 second (FEV1) = 80.8 +/- 22.2; peak flow = 89.7 +/- 34.2, forced expiratory fraction 25-75% (FEF 25-75) = 71.8 +/- 32.8; Z score weight/height = -0.41 +/- 1.14; Z score weight/age = -0.48 +/- 1.25, body mass index = 15.4 +/- 1.8; caloric intake = 107 +/- 25% of recommended dietary allowances (RDA). Patients had a Shwachman-Kulczycki's score of 87 +/- 9. Spirometric and nutritional data were analysed after 1, 3, 6, 12, 18 and 24 months of treatment and compared to baseline values (changes evaluated as percent change from mean baseline for spirometric data). Shwachman-Kulczycki's score was calculated after 24 months of rhDNase. RESULTS: An improvement of FVC (+10.7%, P < 0.001) and FEV1 (+12%, P < 0.01) was noted after one month of treatment and was maintained throughout the following 2 years around 8.7% (6.4-11.4) for FVC and 8.2% (7.3-9.1) for FEV1, P < or = 0.01. This was particularly observed in children aged 5 to 10 years, in boys and in patients with a baseline FVC under 70% predicted. There was no significant change in FEF 25-75. We observed an improvement of daily caloric intake from the third month (P < 0.05) and of body mass index from the sixth month (P = 0.02). This was particularly noted in girls. Z score weight/age was improved only during the first 3 months of treatment while Z score weight/height increased only after a 2 year follow-up. There was no significant change in Shwachman-Kulczycki's score after 24 months of rhDNase. CONCLUSION: rhDNase in CF children in effective on lung function as well as on nutritional status and the response to this treatment can be evaluated after the first 3 months.

N-terminal characterization of the Bordetella pertussis filamentous haemagglutinin.

The major adhesin of Bordetella pertussis, filamentous haemagglutinin (FHA), is produced and secreted at high levels by the bacterium. Mature FHA derives from a large precursor, FhaB, that undergoes several post-translational maturations. In this work, we demonstrate by site-directed mutagenesis that the N-terminal signal peptide of FHA is composed of 71 amino acids, including a 22-residue-long 'N-terminal extension' sequence. This sequence, although highly conserved in various other secretory proteins, does not appear to play an essential part in FHA secretion, as shown by deletion mutagenesis. The entire N-terminal signal region of FhaB is removed in the course of secretion by proteolytic cleavage at a site that corresponds to a Lep signal peptidase recognition sequence. After this maturation, the N-terminal glutamine residue is modified to a pyroglutamate residue. This modification is not crucial for heparin binding, haemagglutination or secretion. Interestingly, however, the modification is absent from Escherichia coli secreted FHA derivatives. In addition, it is dependent in B. pertussis on the presence of all three cysteines contained in the signal peptide of FhaB. These observations suggest that it does not occur spontaneously but perhaps requires a specific enzymatic machinery.

Lack of functional complementation between Bordetella pertussis filamentous hemagglutinin and Proteus mirabilis HpmA hemolysin secretion machineries.

The gram-negative bacterium Bordetella pertussis has adapted specific secretion machineries for each of its major secretory proteins. In particular, the highly efficient secretion of filamentous hemagglutinin (FHA) is mediated by the accessory protein FhaC. FhaC belongs to a family of outer membrane proteins which are involved in the secretion of large adhesins or in the activation and secretion of Ca2+-independent hemolysins by several gram-negative bacteria. FHA shares with these hemolysins a 115-residue-long amino-proximal region essential for its secretion. To compare the secretory pathways of these hemolysins and FHA, we attempted functional transcomplementation between FhaC and the Proteus mirabilis hemolysin accessory protein HpmB. HpmB could not promote the secretion of FHA derivatives. Likewise, FhaC proved to be unable to mediate secretion and activation of HpmA, the cognate secretory partner of HpmB. In contrast, ShlB, the accessory protein of the closely related Serratia marcescens hemolysin, was able to activate and secrete HpmA. Two invariant asparagine residues lying in the region of homology shared by secretory proteins and shown to be essential for the secretion and activation of the hemolysins were replaced in FHA by site-directed mutagenesis. Replacements of these residues indicated that both are involved in, but only the first one is crucial to, FHA secretion. This slight discrepancy together with the lack of functional complementation demonstrates major differences between the hemolysins and FHA secretion machineries.

Amino-terminal maturation of the Bordetella pertussis filamentous haemagglutinin.

The 220 kDa filamentous haemagglutinin (FHA) is a major adhesin of Bordetella pertussis and is produced from a large precursor designated FhaB. Although partly surface associated, it is also very efficiently secreted into the extracellular milieu. Its secretion depends on the outer membrane accessory protein FhaC. An 80 kDa N-terminal derivative of FHA, named Fha44, can also be very efficiently secreted in a FhaC-dependent manner, indicating that all necessary secretion signals are localized in the N-terminal region of FhaB. A comparison of predicted and apparent sizes of FHA derivatives, in addition to immunoblot analyses of cell-associated and secreted FHA polypeptides, indicated that FhaB undergoes N-terminal maturation by the cleavage of an 8-9 kDa segment. However, phenotypic analyses of translational lacZ and phoA fusions showed that this segment does not function as a typical signal peptide. Co-expression of the Fha44-encoding gene with fhaC also did not allow for secretion of Fha44 in Escherichia coli. High levels of secretion could, however, be observed when the OmpA signal peptide was fused to the N-terminal end of Fha44. Regardless of the OmpA signal peptide-Fha44 fusion point, the E. coli-secreted Fha44 had the same M(r) as that secreted by B. pertussis, indicating that the N-terminal proteolytic maturation does not require a B. pertussis-specific factor. Similar to FHA, the B. pertussis-secreted Fha44 contains an as yet uncharacterized modification at its N-terminus. This modification did not occur in E. coli and is therefore not required for secretion. The N-terminus of Fha44 secreted by E. coli was determined and found to correspond to the 72nd residue after the first in-frame methionine of FhaB. The N-terminal modification was also found not to be required for haemagglutination or interaction with sulphated glycoconjugates.