Inclusion of S-sepharose beads in the culture medium significantly improves recovery of secreted rBPI(21) from transfected CHO-K1 cells

Optimized expression of the antimicrobial protein Gloverin from Galleria mellonella using stably transformed Drosophila melanogaster S2 cells

Antimicrobial proteins and peptides (AMPs) are valuable as leads in the pharmaceutical industry for the development of novel anti-infective drugs. Here we describe the efficient heterologous expression and basic characterization of a Gloverin-family AMP derived from the greater wax moth Galleria mellonella. Highly productive single-cell clones prepared by limiting dilution achieved a 100% increase in productivity compared to the original polyclonal Drosophila melanogaster S2 cell line. Comprehensive screening for suitable expression conditions using statistical experimental designs revealed that optimal induction was achieved using 600 µM CuSO4 at the mid-exponential growth phase. Under these conditions, 25 mg/L of the AMP was expressed at the 1-L bioreactor scale, with optimal induction and harvest times ensured by dielectric spectroscopy and the online measurement of optical density. Gloverin was purified from the supernatant by immobilized metal ion affinity chromatography followed by dialysis. In growth assays, the purified protein showed specific antimicrobial activity against two different strains of Escherichia coli.

rBPI(10—193) is secreted by CHO cells and retains the activity of rBPI21

rBPI23, a recombinant N-terminal fragment of human bactericidal/permeability-increasing protein (BPI), kills Gram-negative bacteria and neutralizes endotoxin. rBPI 21, a variant in which cysteine 132 is changed to alanine, retains the activities of rBPI23. Analysis of certain purified rBPI 21 preparations revealed that some of the molecules had lost nine amino acids from the amino terminus. To explore the effect of this modification on structure and activity, we cloned and expressed a variant of rBPI 21, designated rBPI(10-193), which lacks the first nine amino acids. A monoclonal antibody believed to recognize the amino terminus of rBPI 21 cross-reacted with rBPI21, but not with rBPI(10-193) or full length recombinant BPI (rBPI). These results demonstrated that the antibody recognizes the first nine amino acids of rBPI21 and that this region of the holoprotein (rBPI) is inaccessible to the antibody (as suggested by the known 3-D structure). Purified rBPI(10193) and rBPI 21 were similarly potent in in vitro assays measuring bactericidal, endotoxin binding and neutralization activities. In a mouse model of lethal bacteremia, rBPI(10-193) and rBPI21 were similarly potent whereas in a mouse endotoxin challenge model, rBPI(10-193) appeared to be at least 2-fold more potent than rBPI21. In conscious rats, a rapid bolus dose of 40 mg/kg of rBPI21 caused a significant transient decrease in blood pressure while the same dose of rBPI(10-193) caused no blood pressure decrease. We conclude from these studies that the first nine amino acids of rBPI21 are not essential for the anti-infective and endotoxin-neutralizing activities of BPI.

DUF538 protein super family is predicted to be the potential homologue of bactericidal/permeability-increasing protein in plant system

DUF538 protein super family includes a number of plant proteins that their role is not yet clear. These proteins have been frequently reported to be expressed in plants under various stressful stimuli such as bacteria and elicitors. In order to further understand about this protein family we utilized bioinformatics tools to analyze its structure in details. As a result, plants DUF538 was predicted to be the partial structural homologue of BPI (bactericidal/permeability increasing) proteins in mammalian innate immune system that provides the first line of defense against different pathogens including bacteria, fungi, viruses and parasites. Moreover, on the base of the experimental data, it was identified that exogenously applied purified fused product of Celosia DUF538 affects the bacterial growth more possibly similar to BPI through the binding to the bacterial membranes. In conclusion, as the first ever time report, we nominated DUF538 protein family as the potential structural and functional homologue of BPI protein in plants, providing a basis to study the novel functions of this protein family in the biological systems in the future.

rBPI(21) promotes lipopolysaccharide aggregation and exerts its antimicrobial effects by (hemi)fusion of PG-containing membranes

Antimicrobial peptides (AMPs) are important potential alternatives to conventional therapies against bacterial infections. rBPI(21) is a 21 kDa peptide based on the N-terminal region of the neutrophil bactericidal/permeability-increasing protein (BPI). This AMP possesses highly selective bactericidal effects on Gram-negative bacteria and have affinity for lipopolysaccharide (LPS) which is believed to be at the origin of its neutralizing effect of the LPS segregated into the bloodstream. We aim at understanding the molecular bases of rBPI(21) bactericidal and LPS neutralization actions, using biomembrane model systems. Using dynamic light scattering spectroscopy we demonstrate that rBPI(21) promotes aggregation of negatively charged large unilamellar vesicles (LUV), even in the absence of LPS, and LPS aggregates, while for zwitterionic phosphatidylcholine (POPC) LUV the size remains unchanged. The peptide also promotes the fusion (or hemifusion) of membranes containing phosphatidylglycerol (POPG). The aggregation and fusion of negatively charged LUV are peptide concentration-dependent until massive aggregation is reached, followed by sample flocculation/precipitation. Concomitantly, there is a progressive change in the zeta-potential of the LUV systems and LPS aggregates. LUV systems composed of phosphatidylglycerol (POPG) and lipid mixtures with POPG have higher zeta-potential variations than in the absence of POPG. The interaction of rBPI(21) with lipid vesicles is followed by leakage, with higher effect in POPG-containing membranes. LPS aggregation can be related with a decreased toxicity, possibly by facilitating its clearance by macrophage phagocytosis and/or blocking of LPS specific receptor recognition. Our data indicate that rBPI(21) mechanism of action at the molecular level involves the interaction with the LPS of the outer membrane of Gram-negative bacteria, followed by internalization and leakage induction through the (hemi)fusion of the bacterial outer and inner membranes, both enriched in phosphatidylglycerol.

Stable expression in a Chinese hamster ovary (CHO) cell line of bioactive recombinant chelonianin, which plays an important role in protecting fish against pathogenic infection

Chelonianin, originally isolated from the shrimp (Penaeus monodon), exhibits antimicrobial effects in vitro and in vivo and is used to treat infectious fish diseases. Herein, we report that the recombinant chelonianin protein fused to a fluorescent protein (rcf protein) was expressed from a stably transfected Chinese hamster ovary (CHO) cells. The in vitro experiments showed that the rcf protein exhibited antimicrobial activity against several bacteria, while the recombinant fluorescent protein alone did not. In addition, pretreatment and post-treatment with the rcf protein were both effective in promoting a significant decrease in fish mortality and decreasing the number of infectious bacteria. We utilized the quantitative reverse-transcriptase polymerase chain reaction technique to survey the levels of gene expressions of tumor necrosis factor-alpha (TNF-alpha) and nitric oxide synthase 1 induced in response to bacterial infection in experiments with tilapia (Oreochromis mossambicus). Our results indicated that the rescue of fish treated with the rcf protein may involve regulation of TNF-alpha expression. Collectively, chelonianin inhibited the production of an inflammatory mediator and reduced mortality in fish during bacterial challenge, suggesting that it has potential as a therapeutic or prophylactic drug for use against bacterial infectious diseases.