Protection of mice from lethal Escherichia coli infection by chimeric human bactericidal/permeability-increasing protein and immunoglobulin G1 Fc gene delivery

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.

In-vivo toxicity and therapeutic efficacy of Paeonia emodi-mediated zinc oxide nanoparticles: In-vitro study

This study was planned to explore the in-vitro and in-vivo therapeutic significance of Paeonia emodi-mediated zinc oxide nanoparticles (ZnO NPs) against the Staphylococcus aureus and Escherichia coli. The texture parameters were derived from nitrogen adsorption-desorption data using Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods, and the surface area (S_BET ) was found to be 214 m² /g with a pore size of 2.3 nm. The crystallographic parameters were investigated through X-ray diffraction analysis, and the calculated crystallite size is 29.13 nm. The microstructure was examined through transmission and scanning electron microscopies (TEM and SEM, respectively), and the average particle size estimated from a TEM image is 44.40 nm. The chemical composition and attached function groups were identified through energy-dispersive X-ray and Fourier transform infrared spectroscopies. The in-vitro minimum inhibitory concentration (MIC) for both bacterial species results was found less than 2 μg/ml. The tolerance limit of mouse models was evaluated by the inoculation of different concentrations of ZnO suspension where the concentration above 23 ppm was proved lethal. The maximum infection was caused in mouse models by inoculation of 3 × 10⁷ CFUs (Colony forming unit) of the both bacterial species. The concentration higher than 3 × 10⁷ CFUs led to the ultimate death of the mice. The histopathological and hematological studies reveal that the after simultaneous inoculation of both ZnO NPs and bacterial suspensions (tolerated amount), no/negligible infection was found in the mice model.

In-Vitro and In-Vivo Tolerance and Therapeutic Investigations of Phyto-Fabricated Iron Oxide Nanoparticles against Selected Pathogens

The Paeonia emodi (P. emodi)-mediated iron oxide nanoparticles (Fe₂O₃ NPs) were screened for in-vitro and in-vivo antibacterial activity against the Staphylococcus aureus (S. aureus) (ATCC #: 6538) and Escherichia coli (E. coli) (ATCC #:15224). The synthesized Fe₂O₃ NPs were characterized via nitrogen adsorption-desorption process, X-ray diffractometer (XRD), transmission and scanning electron microscopies (TEM and SEM), energy dispersive X-ray (EDX) and Fourier transform infrared (FTIR) spectroscopies. The S_BET was found to be 94.65 m²/g with pore size of 2.99 nm, whereas the average crystallite and particles size are 23 and 27.64 nm, respectively. The 4 μg/mL is the MIC that inhibits the growth of E. coli, whereas those for S. aureus are below the detection limit (<1.76 μg/mL). The tolerance limit of the mice model was inspected by injecting different concentration of Fe₂O₃ NPs and bacteria suspensions. The 14 ppm suspension was the tolerated dose and the concentration above were proved lethal. The most severe infection was induced in mice with injection of 3 × 10⁷ CFUs of both bacteria, while the inoculation of higher concentrations of bacterial suspensions resulted in the mice's death. The histopathological and hematological studies reveals that the no/negligible infection was found in the mice exposed to the simultaneous inoculation of Fe₂O₃ NPs (14 ppm) and bacterial suspensions (3 × 10⁷ CFUs).

Antimicrobial and immunomodulatory activity induced by loperamide in mycobacterial infections

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Loperamide modulates macrophages immune responses towards mycobacteria.

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Loperamide is an immunoregulator of inflammation during mycobacterial infection.

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Loperamide induces immunomodulatory responses and bactericidal mechanisms.

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The activation of opioid receptors by loperamide is involved in its immunomodulatory activity.

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.

Bactericidal/permeability-increasing protein (rBPI21) and fluoroquinolone mitigate radiation-induced bone marrow aplasia and death

Identification of safe, effective treatments to mitigate toxicity after extensive radiation exposure has proven challenging. Only a limited number of candidate approaches have emerged, and the U.S. Food and Drug Administration has yet to approve any agent for a mass-casualty radiation disaster. Because patients undergoing hematopoietic stem cell transplantation undergo radiation treatment that produces toxicities similar to radiation-disaster exposure, we studied patients early after such treatment to identify new approaches to this problem. Patients rapidly developed endotoxemia and reduced plasma bactericidal/permeability-increasing protein (BPI), a potent endotoxin-neutralizing protein, in association with neutropenia. We hypothesized that a treatment supplying similar endotoxin-neutralizing activity might replace the BPI deficit and mitigate radiation toxicity and tested this idea in mice. A single 7-Gy radiation dose, which killed 95% of the mice by 30 days, was followed 24 hours later by twice-daily, subcutaneous injections of the recombinant BPI fragment rBPI21 or vehicle alone for 14 or 30 days, with or without an oral fluoroquinolone antibiotic with broad-spectrum antibacterial activity, including that against endotoxin-bearing Gram-negative bacteria. Compared to either fluoroquinolone alone or vehicle plus fluoroquinolone, the combined rBPI21 plus fluoroquinolone treatment improved survival, accelerated hematopoietic recovery, and promoted expansion of stem and progenitor cells. The observed efficacy of rBPI21 plus fluoroquinolone initiated 24 hours after lethal irradiation, combined with their established favorable bioactivity and safety profiles in critically ill humans, suggests the potential clinical use of this radiation mitigation strategy and supports its further evaluation.

Infecting mice with recombinant Ad5-BPI₂₃-Fcγ1 virus protects against systemic Escherichia coli challenge

Infections caused by Gram-negative bacteria (GNB) are increasingly common and can result in significant mortality rates due to the development of sepsis. To examine the potential usage of a recombinant Ad5-BPI(23)-Fcγ1 virus as a biological treatment against systemic infection by GNB, a construct containing the human bactericidal/permeability increasing protein (BPI) gene, encoding the functional N terminus (amino acid residues 1-199) of human BPI, and the Fcγ1 gene, encoding the Fc segment of human immunoglobulin G1, was inserted into an adenovirus serotype 5 (Ad5) chromosome to produce a recombinant Ad5-BPI(23)-Fcγ1 virus. Human A549 cells in culture and BALB/c mice were infected with the recombinant Ad5-BPI(23)-Fcγ1 virus and BPI(23)-Fcγ1 expression was confirmed by Western blot analysis and ELISA. The concentrations of BPI(23)-Fcγ1 protein were 5.59 µg ml(-1) in vitro and 21.37 ng ml(-1) in vivo and it was observed that these concentrations were sufficient to decrease endotoxin concentrations while enhancing bactericidal activity. In addition, mice treated with the recombinant Ad5-BPI(23)-Fcγ1 virus had decreased levels of IL-1β and TNF-α and were protected from an E. coli O111 : B4 challenge. Our data support the concept that Ad5-mediated BPI(23)-Fcγ1 gene delivery could be used as an ancillary biological treatment in the management of infection caused by GNB.

The bactericidal/permeability-increasing protein (BPI) in the innate defence of the lower airways

The human BPI (bactericidal/permeability-increasing protein), stored in primary azurophilic granula of neutrophil granulocytes and produced by mucosal epithelia, has been known for decades to bind LPS (lipopolysaccharide) with very high affinity and to efficiently kill Gram-negative bacteria. Thus BPI potentially represents a central component of the innate immune system to directly combat microbes and modulate subsequent adaptive immune responses. Especially in the lungs, which are frequently exposed to a variety of inhaled pathogens, antimicrobial innate defence molecules such as BPI, are of exceptional relevance. In the present review, we highlight possible functions of BPI during acute pneumonia and CF (cystic fibrosis)-associated chronic infections in the lung.