Bactericidal permeability increasing protein gene polymorphism is associated with inflammatory bowel diseases in the Turkish population

BPI23-Fcγ alleviates lethal multi-drug-resistant Acinetobacter baumannii infection by enhancing bactericidal activity and orchestrating neutrophil function

Antibiotic resistance has become a major threat, contributing significantly to morbidity and mortality globally. Administering non-antibiotic therapy, such as antimicrobial peptides, is one potential strategy for effective treatment of multi-drug-resistant Gram-negative bacterial infections. Bactericidal/permeability-increasing protein (BPI) derived from neutrophils has bactericidal and endotoxin-neutralizing activity. However, the protective roles and mechanisms of BPI in multi-drug-resistant bacterial infections have not been fully elucidated. In this study, a chimeric BPI23-Fcγ recombined protein comprising the functional N terminus of BPI and Fcγ was constructed and expressed by adenovirus vector 5 (Ad5). Ad5-BPI23-Fcγ or recombinant BPI23-Fcγ protein significantly improved the survival of mice with pneumonia induced by a minimal lethal dose of multi-drug-resistant Acinetobacter baumannii or Klebsiella pneumoniae by ameliorating lung pathology and reducing pro-inflammatory cytokines. Transfection with Ad5-BPI23-Fcγ significantly decreased the bacterial load and endotoxaemia, which was associated with enhanced bactericidal ability and elevated the phagocytic activity of neutrophils in vitro and in vivo. In addition, Ad5-BPI23-Fcγ transfection significantly increased the recruitment of neutrophils to lung, increased the proportion and number of neutrophils in peripheral blood, and promoted the maturation of bone marrow (BM) neutrophils after drug-resistant A. baumannii infection. BPI23-Fcγ and neutrophils synergistically enhanced bactericidal activity and decreased pro-inflammatory cytokines. These results demonstrated that the chimeric BPI23-Fcγ protein protected mice from pneumonia induced by multi-drug-resistant A. baumannii infection by direct bactericidal effects and promotion of neutrophil recruitment, phagocytosis and maturation. Chimeric BPI23-Fcγ may be a promising candidate as a non-antibiotic biological agent for multi-drug-resistant A. baumannii infection.

Killing three birds with one BPI: Bactericidal, opsonic, and anti-inflammatory functions

Bactericidal/permeability-increasing protein (BPI) is an anti-microbial protein predominantly expressed in azurophilic granules of neutrophils. BPI has been shown to mediate cytocidal and opsonic activity against Gram-negative bacteria, while also blunting inflammatory activity of lipopolysaccharide (LPS). Despite awareness of these functions in vitro, the magnitude of the contribution of BPI to innate immunity remains unclear, and the nature of the functional role of BPI in vivo has been submitted to limited investigation. Understanding this role takes on particular interest with the recognition that autoimmunity to BPI is tightly linked to a specific infectious trigger like Pseudomonas aeruginosa in chronic lung infection. This has led to the notion that anti-BPI autoantibodies compromise the activity of BPI in innate immunity against P. aeruginosa, which is primarily mediated by neutrophils. In this review, we explore the three main mechanisms in bactericidal, opsonic, and anti-inflammatory of BPI. We address the etiology and the effects of BPI autoreactivity on BPI function. We explore BPI polymorphism and its link to multiple diseases. We summarize BPI therapeutic potential in both animal models and human studies, as well as offer therapeutic approaches to designing a sustainable and promising BPI molecule.

Bactericidal Permeability Increasing Protein Deficiency Aggravates Acute Colitis in Mice by Increasing the Serum Levels of Lipopolysaccharide

Objective

The objective of this study was to understand the role of bactericidal permeability increasing protein (BPI) in the pathogenesis of experimental murine colitis.

Methods

We used the Cre-LoxP system to generate BPI knockout (BPI KO) mice. Acute colitis was induced in BPI KO mice and wild-type (WT) mice by subjecting the mice to 5% dextran sulfate sodium (DSS). Mice were observed for symptoms of experimental colitis. The survival of BPI KO mice to infection with Acinetobacter baumannii, a gram-negative bacterium, was also assessed.

Results

Southern blot, RT-PCR, and western blot results showed that the 2nd and 3rd exons of the murine Bpi gene were knocked out systemically, confirming successful construction of the BPI KO mouse. BPI KO mice subjected to DSS showed increased symptoms of experimental colitis, increased colonic mucosal damage, increased epithelial permeability, elevated levels of serum LPS, and a disrupted fecal microbiome as compared with WT mice. Furthermore, BPI KO mice challenged intraperitoneally with A. baumannii died sooner than WT mice, and the total number of bacteria in the abdominal cavity, spleen, and liver was increased in BPI KO mice as compared to WT mice.

Conclusions

We successfully generated BPI KO mice. The BPI KO mice developed worse colitis than WT mice by increased colitis symptoms and colonic mucosal damage, elevated levels of serum LPS, and a disrupted microbiome. BPI could be a potential target for treatment of ulcerative colitis in humans.

Bactericidal/permeability increasing protein gene polymorphism and inflammatory bowel diseases: meta-analysis of five case-control studies

OBJECTIVE

Bactericidal/permeability increasing protein (BPI) gene polymorphisms have been extensively investigated in terms of their associations with inflammatory bowel disease (IBD), with contradictory results. The aim of this meta-analysis was to evaluate associations between BPI gene polymorphisms and the risk of IBD, Crohn's disease (CD), and ulcerative colitis (UC).

METHODS

Eligible studies from PubMed, Embase, and Cochrane library databases were identified.

RESULTS

Ten studies (five CD and five UC) published in five papers were included in this meta-analysis. G645A polymorphism was associated with a decreased risk of UC in allele model, dominant model, and homozygous model.

CONCLUSIONS

Our data suggested that BPI G645A polymorphism was associated with a decreased risk of UC; the BPI G645A polymorphism was not associated with the risk of CD.

Long-term anti-endotoxin/E. coli efficacy in mice transfected with AAV2/1-muBPI25 -muFcγ1

Bactericidal/permeability increasing (BPI) is an antibiotic protein which kills Gram-negative bacteria and neutralizes endotoxin. We have previously developed a recombinant adeno-associated virus which contains human BPI amino acid residues 1-199 and Fc fragment of human IgG1 gene (AAV-hBPI-Fc) and shown that the recombinant virus can protect mice from lethal endotoxemia. However, whether AAV-hBPI-Fc can be used in vivo for the long term remains unclear. To address this, we established an adeno-associated virus-containing mouse BPI and Fc fragment genes (muBPI-Fc) and compared antigenicity of these recombinant proteins in murine models. Immunohistochemistry showed the expression of both fusion proteins at injected sites. ELISA and Western blotting showed that the muBPI-Fc protein was detected in serum up to 8 weeks after injection, without generation of autoantibodies against muBPI-Fc. In contrast, expressed hBPI-Fc protein was only detected on the 2nd week, whereas the autoantibody against hBPI-Fc protein occurred in serum from the 4th week to the end of study. muBPI-Fc also reduced production of proinflammatory cytokines and protected mice from endotoxemia and bacteremia. Our data showed that AAV-muBPI-Fc has potential long-term efficacy as an anti-endotoxin and has anti-bacterial activity in mice, suggesting the potential clinical application of AAV-hBPI-Fc, such as in endotoxin shock.