Anti-CAMP1 IgG promotes macrophage phagocytosis of Cutibacterium acnes type II.

Among 5 types of the Christie-Atkins-Munch-Petersen factor (CAMP) of Cutibacterium acnes, CAMP1 is highly expressed in phylotype II as well as IB, and thought to be a virulence factor of opportunistic but fatal blood, soft tissue, and implant-related infections. The target of a human single-chain variable antibody fragment (scFv), recently isolated from a phage display library, has been identified as CAMP1 of phylotype II, using immunoprecipitation followed by mass spectrometry, phage display peptide biopanning, 3D-modelling, and ELISA. The IgG1 format of the antibody could enhance phagocytosis of C. acnes DMST 14916 by THP-1 human monocytes. Our results suggest that the antibody-dependent phagocytosis process is mediated by the caveolae membrane system and involves the induction of IL-1ß. This is the first report on the study of a human antibody against CAMP1 of C. acnes phylotype II, of which a potential use as therapeutic antibody against virulence C. acnes infection is postulated.

Production and applications of fluorobody from redox-engineered Escherichia coli.

Efficient selection and production of antibody fragments in microbial systems remain to be a challenging process. To optimize microbial production of single-chain variable fragments (scFvs), we have chosen five model targets, 1) a hapten, Zearalenone (ZEN) mycotoxin, along with infectious agents 2) rabies virus, 3) Propionibacterium acnes, 4) Pseudomonas aeruginosa, and a cancer cell 5) acute myeloid leukemia cell line (HL-60). The scFv binders were affinity selected from a non-immunized human phage display scFv antibody library and genetically fused to the N-terminus of emerald green fluorescent protein (EmGFP). The scFv-EmGFP fusion constructs were subcloned into an expression vector, under the control of T7 promoter, C-terminally tagged with hexa-histidine and expressed in different Escherichia coli (E. coli) hosts. This enabled the detection of cells that expressed the correct scFv-EmGFP fusion, termed fluorobody, via bright fluorescent signal in the cytoplasm. Among the three E. coli hosts tested, an engineered E. coli B strain called SHuffle B that promotes disulfide bond formation in the cytoplasm appeared to be the most appropriate host. The recombinant fluorobodies were well expressed (2-8 mg/L), possessed the fluorescence property of EmGFP, and retained the ability to bind to their cognate targets. Their specific bindings were demonstrated by ELISA, fluorescence-linked immunosorbent assay (FLISA), flow cytometry, and fluorescent microscope imaging. The fluorobody expression platform in this study could be further adopted as a one-step immunostaining technique based on scFv, isolated from phage display library to numerous desired targets. KEY POINTS: • E. coli SHuffle express T7 is a suitable expression host for scFv-EmGFP (fluorobody) • Only the clones harboring scFv-EmGFP plasmid will show bright fluorescent signal • This platform can be used to produce fluorobodies for numerous purposes.

Human Hexa-Histidine-Tagged Single-Chain Variable Fragments for Bioimaging of Bacterial Infections.

The single-chain variable fragment (scFv) of monoclonal antibodies is a promising recombinant nanostructure for various medical applications, including bioimaging and targeted therapy. While numerous scFv antibodies against eukaryotic cell surface proteins (especially cancer biomarkers) have been generated and engineered to suit various purposes, only a few specific scFv against bacterial cell surfaces have been developed, especially those of human origin. Recent incidents of emerging multidrug-resistant pathogenic bacteria and the realization of the importance of a balanced microbiota on the health of the host has led to more interests in the development of recombinant antibacterial antibodies as a detection probe or targeted therapy for bacterial infections. This study reports the generation of two specific human antibacterial scFv using phage display antibody technology. The recombinant scFv fragments of about 30 kDa and a diameter of 5 nm were produced and purified from engineered Escherichia coli that can enhance cytosolic disulfide bond formation. As a proof of principle, Propionibacterium acnes and Pseudomonas aeruginosa were used as model Gram-positive and Gram-negative bacteria, respectively. Specificity at the strain and species level to both planktonic and biofilm forms of these bacteria were demonstrated in various assay formats, namely, ELISA, flow cytometry, western blot, immunofluorescence, and electron microscopy via the hexa-histidine tag. This recombinant scFv generation platform can be applied for other bacteria, and since the scFv obtained has a benefit of being a human origin, it could be conveniently engineered for various therapeutic or theranostic applications with minimized adverse immunoreaction.