High levels of complement-activation capacity in sera from patients with cystic fibrosis correlate with high levels of IgG3 antibodies to Pseudomonas aeruginosa antigens and poor lung function

Systems serology in cystic fibrosis: Anti-Pseudomonas IgG1 responses and reduced lung function

Nearly one-half of patients with cystic fibrosis (CF) carry the homozygous F508del mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene but exhibit variable lung function phenotypes. How adaptive immunity influences their lung function remains unclear, particularly the serological antibody responses to antigens from mucoid Pseudomonas in sera from patients with CF with varying lung function. Sera from patients with CF with reduced lung function show higher anti-outer membrane protein I (OprI) immunoglobulin G1 (IgG1) titers and greater antibody-mediated complement deposition. Induction of anti-OprI antibody isotypes with complement activity enhances lung inflammation in preclinical mouse models. This enhanced inflammation is absent in immunized Rag2-/- mice and is transferrable to unimmunized mice through sera. In a CF cohort undergoing treatment with elexacaftor-tezacaftor-ivacaftor, the declination in anti-OprI IgG1 titers is associated with lung function improvement and reduced hospitalizations. These findings suggest that antibody responses to specific Pseudomonas aeruginosa (PA) antigens worsen lung function in patients with CF.

Mechanisms of humoral immune response against Pseudomonas aeruginosa biofilm infection in cystic fibrosis

P. aeruginosa chronic lung infection is the major cause of morbidity and mortality in patients with cystic fibrosis (CF), and is characterized by a biofilm mode of growth, increased levels of specific IgG antibodies and immune complex formation. However, despite being designed to combat this infection, such elevated humoral response is not associated with clinical improvement, pointing to a lack of anti-pseudomonas effectiveness. The mode of action of specific antibodies, as well as their structural features, and even the background involving B-cell production, stimulation and differentiation into antibody-producing cells in the CF airways are poorly understood. Thus, the aim of this review is to discuss studies that have addressed the intrinsic features of the humoral immune response and provide new insights regarding its insufficiency in the CF context.

Complement Effectors of Inflammation in Cystic Fibrosis Lung Fluid Correlate with Clinical Measures of Disease

In cystic fibrosis (CF), lung damage is mediated by a cycle of obstruction, infection, and inflammation. Here we explored complement inflammatory effectors in CF lung fluid. In this study soluble fractions (sols) from sputum samples of 15 CF patients were assayed for complement effectors and analyzed with clinical measurements. The pro-inflammatory peptide C5a was increased 4.8-fold (P = 0.04) in CF sols compared with controls. Incubation of CF sols with P. aeruginosa or S. aureus increased C5a concentration 2.3-fold (P = 0.02). A peptide inhibitor of complement C1 (PIC1) completely blocked the increase in C5a concentration from P. aeruginosa in CF sol in vitro (P = 0.001). C5a concentration in CF sol correlated inversely with body mass index (BMI) percentile in children (r = -0.77, P = 0.04). C3a, which has anti-inflammatory effects, correlated positively with FEV1% predicted (r_s = 0.63, P = 0.02). These results suggest that complement effectors may significantly impact inflammation in CF lung fluid.

Neonatal infections in Saudi Arabia: association with C-reactive protein, CRP -286 (C>T>A) gene polymorphism and IgG antibodies

Background

C-reactive protein (CRP) is a nonspecific, acute-phase protein that rises in response to infectious and non-infectious inflammatory processes. Infections are the single largest cause of neonatal deaths globally.

The primary aim of this study is to examine the association between CRP gene polymorphism and serum levels of CRP in correlation with early onset sepsis (EOS) infection in newborns living in Taif city, Saudi Arabia. The second aim is to examine the relationship between specific IgG/IgG subclasses and early onset sepsis (EOS) infection among these newborns.

Methods

Staphylococcus aureus (S. aureus) is one of the most common organisms related to sepsis infection in the newborn at King Abdel Aziz Specialist Hospital (KAASH). This study was conducted in Taif city, at KAASH’s neonatal intensive care unit between March and August 2012. Neonates were consecutively enrolled onto the study having met our inclusion criteria (as per our research protocol).

The CRP concentration level was analysed using NycoCard® CRP Single Test. CRP -286 (C>T>A) A polymorphisms were analyzed using Pyrosequencing technology for CRP genotyping. IgG subclasses were analysed in the study population using ELISA.

Result

Logistic regression analyses showed that the AA and AC genotypes were negatively associated amongst EOS neonates compared to suspected neonates. The frequency of CC and CT were significantly associated with the EOS neonates compared to the suspected group. The levels of specific IgG1, IgG2 and IgG3 antibodies were significantly lower amongst EOS compared to the suspected group.

Conclusions

Taken together, the CRP-286 (C>T>A) A genotype polymorphism and specific IgG antibodies isotype levels can contribute to a reduced risk of EOS. Furthermore, CRP has a potential use in detecting EOS in neonates, which may mean earlier detection and management of EOS and subsequently better clinical outcome.

Usefulness of serum IgG4 in the diagnosis and follow up of autoimmune pancreatitis: A systematic literature review and meta-analysis

High circulating serum immunoglobulin G4 (IgG4) levels have been proposed as a marker of autoimmune pancreatitis (AIP). The aim of the present study was to review the data existing in the English literature on the usefulness of the IgG4 serum levels in the diagnosis and follow up of patients with AIP. A total of 159 patients with AIP and 1099 controls were described in seven selected papers reporting the usefulness of serum IgG4 in diagnosing AIP. In total, 304 controls had pancreatic cancer, 96 had autoimmune diseases, and the remaining 699 had other conditions. The summary receiver-operating characteristic curve analysis was carried out by means of Meta-DiSc open-access software. Serum IgG4 showed good accuracy in distinguishing between AIP and the overall controls, pancreatic cancer and other autoimmune diseases (area under the curve [+/- SE]: 0.920 +/- 0.073, 0.914 +/- 0.191, and 0.949 +/- 0.024, respectively). The studies analyzed showed significantly heterogeneous specificity values in each of the three analyses performed. The analysis of the four studies comparing AIP and pancreatic cancers also showed significantly heterogeneous values of sensitivities and odds ratios. Regarding the usefulness of IgG4 as a marker of efficacy of steroid treatment, a decrease in the serum concentrations of IgG4 was found in the four available studies. The serum IgG4 subclass is a good marker of AIP, and its determination should be included in the diagnostic workup of this disease. However, the heterogeneity of the studies published until now means that more studies are necessary in order to better evaluate the true accuracy of IgG4 in discriminating AIP versus other autoimmune diseases.

Anti-neutrophil cytoplasmatic antibodies and lung disease in cystic fibrosis

BACKGROUND

Bactericidal-permeability-increasing protein (BPI) is a potent anti-microbial protein produced by neutrophil granulocytes. Anti-neutrophil cytoplasmatic antibodies (ANCA) directed against BPI have been detected in up to 91% in patients with cystic fibrosis (CF). We aimed to evaluate the prevalence of BPI-ANCA in our CF patients and to determine whether presence of BPI-ANCA is correlated with organ damage.

METHODS

Twenty-four patients performed respiratory function testing and pulmonary high-resolution computed tomography (HRCT). HRCT was scored by using a modified Bhalla method. Serum samples were analysed by direct binding enzyme-linked immunosorbent assay for BPI-ANCA.

RESULTS

The prevalence of anti-BPI-IgG was 71% and anti-BPI-IgA 33%. Twenty-nine percent of our patients were positive for both BPI-ANCA isotypes. Mean HRCT score was 8.0 ranging from 0 to 22, bronchiectasis presented the most common finding (79%). There was a significant correlation between BPI-ANCA and both HRCT score and FEV(1) (p < 0.01). High levels of BPI-ANCA were correlated to chronic Pseudomonas aeruginosa lung infection (p < 0.01).

CONCLUSIONS

BPI-ANCA was common in our study group. Highly significant correlations between BPI-ANCA and parameters to evaluate lung disease in CF may be a consequence of the inflammation process, or it may indicate a pathogenic role of BPI-ANCA levels in the development of lung disease. More research is needed and the clinical significance of our findings needs further evaluation.

Binding of Pseudomonas aeruginosa AlgZ to sites upstream of the algZ promoter leads to repression of transcription

Mucoid variants of the opportunistic pathogen Pseudomonas aeruginosa produce the exopolysaccharide alginate and colonize the respiratory tracts of cystic fibrosis patients. The genes encoding the alginate biosynthetic enzymes are clustered in a single operon, which is under tight transcriptional control. One essential activator of the alginate operon is AlgZ, a proposed ribbon-helix-helix DNA binding protein that shares 30% amino acid identity with the Mnt repressor of Salmonella enterica serovar Typhimurium bacteriophage P22. In the current study, we examined the role of AlgZ as an autoregulator. Using single-copy algZ-lacZ transcription fusions, an increase in algZ transcription was observed in an algZ mutant compared to the isogenic wild-type strain, suggesting that AlgZ may have an additional role as a repressor. To identify the AlgZ binding site, overlapping regions upstream of algZ were incubated with AlgZ and analyzed by electrophoretic mobility shift assays. Specific binding activity was localized to a region spanning from 66 to 185 base pairs upstream of the algZ transcriptional start site. Two AlgZ binding sites were defined using copper-phenanthroline footprinting and deletion analyses, with one site centered at 93 base pairs and the other centered at 161 base pairs upstream of the algZ promoter. Deletion of both binding sites resulted in the loss of AlgZ binding. These results indicate that AlgZ represses algZ transcription, and this activity is mediated by multiple AlgZ-DNA interactions.

Ecto-ADP-ribosyltransferase activity of Pseudomonas aeruginosa exoenzyme S

Pseudomonas aeruginosa produces two ADP-ribosyltransferases, exotoxin A and exoenzyme S (ExoS). Although the physiological target protein remains to be defined, ExoS has been shown to ADP-ribosylate several eukaryotic proteins in vitro, including vimentin and members of the family of low-molecular-weight GTP-binding proteins. Recently, ExoS ADP-ribosyltransferase activity has been detected in the pleural fluid of rabbits infected with P. aeruginosa. This observation prompted an examination of the potential for ExoS to function as an ecto-ADP-ribosyltransferase. We have observed that ExoS preferentially ADP-ribosylated two extracellular serum proteins with molecular masses of 150 and 27 kDa. The ADP-ribosylation of these serum proteins by ExoS was stimulated by, but not dependent upon, exogenous FAS (for factor activating exoenzyme S), which indicated that serum contained endogenous FAS activity. Biochemical analysis showed that the 150-kDa ADP-ribosylated protein was immunoglobulin of the immunoglobulin G (IgG) and IgA classes. Subtyping showed that ExoS preferentially ADP-ribosylated human IgG3 and that ADP-ribosylation occurred within its Fc region. The 27-kDa protein ADP-ribosylated by ExoS was determined to be apolipoprotein A1. These data demonstrate ecto-ADP-ribosyltransferase activity by ExoS. This may extend the potential physiological consequences of ExoS during infection by P. aeruginosa beyond the implicated type III secretion-mediated intracellular delivery of ExoS into sensitive eukaryotic cells.