Natural and induced antibodies against phages in humans: induction kinetics and immunogenicity for structural proteins of PB1-related phages

Background: Bacteriophages may induce specific antibodies after natural exposure to phages or after phage therapy. As such, phage-specific antibodies might impact phage bioavailability in vivo, although limited non-neutralizing or insignificant effects have also been reported. Materials and Methods: Here, we report antibody induction against PB1-related phages (Pseudomonas viruses LMA2, F8, DP1) in mice over an 80-day period, for a healthy population of humans, and in patients undergoing phage therapy (oral and/or topical treatment). Results: All phages effectively induced specific immunoglobulin M and immunoglobulin G in mice. Phage-specific antibodies were observed in humans, whereas recombinant virion proteins (PB1 gp22, gp29) did not induce phage-neutralizing antibodies, either in mice or in humans. The healthy human population was differentiated for frequency of phage-neutralizing antibodies. Conclusions: These data can hold key considerations for phage therapy cocktail design, as highly similar phages can still be highly complementary in cases where specific immune response hinders therapeutic use of phages.This work was supported by the National Science Centre in Poland grant no. UMO-2012/05/E/NZ6/03314 (granted to K.D.). S.M.S. acknowledges the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 713640.info:eu-repo/semantics/publishedVersio

Real-Time qPCR as a Method for Detection of Antibody-Neutralized Phage Particles

The most common method for phage quantitation is the plaque assay, which relies on phage ability to infect bacteria. However, non-infective phage particles may preserve other biological properties; specifically, they may enter interactions with the immune system of animals and humans. Here, we demonstrate real-time quantitative polymerase chain reaction (qPCR) detection of bacteriophages as an alternative to the plaque assay. The closely related staphylococcal bacteriophages A3R and 676Z and the coliphage T4 were used as model phages. They were tested in vivo in mice, ex vivo in human sera, and on plastic surfaces designed for ELISAs. T4 phage was injected intravenously into pre-immunized mice. The phage was completely neutralized by specific antibodies within 5 h (0 pfu/ml of serum, as determined by the plaque assay), but it was still detected by qPCR in the amount of approximately 107 pfu/ml of serum. This demonstrates a substantial timelapse between “microbiological disappearance” and true clearance of phage particles from the circulation. In human sera ex vivo, qPCR was also able to detect neutralized phage particles that were not detected by the standard plaque assay. The investigated bacteriophages differed considerably in their ability to immobilize on plastic surfaces: this difference was greater than one order of magnitude, as shown by qPCR of phage recovered from plastic plates. The ELISA did not detect differences in phage binding to plates. Major limitations of qPCR are possible inhibitors of the PCR reaction or free phage DNA, which need to be considered in procedures of phage sample preparation for qPCR testing. We propose that phage pharmacokinetic and pharmacodynamic studies should not rely merely on detection of antibacterial activity of a phage. Real-time qPCR can be an alternative for phage detection, especially in immunological studies of bacteriophages. It can also be useful for studies of phage-based drug nanocarriers or biosensors

Two novel temperate bacteriophages infecting Streptococcus pyogenes: Their genomes, morphology and stability.

Only 3% of phage genomes in NCBI nucleotide database represent phages that are active against Streptococcus sp. With the aim to increase general awareness of phage diversity, we isolated two bacteriophages, Str01 and Str03, active against health-threatening Group A Streptococcus (GAS). Both phages are members of the Siphoviridae, but their analysis revealed that Str01 and Str03 do not belong to any known genus. We identified their structural proteins based on LC-ESI29 MS/MS and list their basic thermal stability and physico-chemical features including optimum pH. Annotated genomic sequences of the phages are deposited in GenBank (NCBI accession numbers KY349816 and KY363359, respectively)

T4 Phage Tail Adhesin Gp12 Counteracts LPS-induced Inflammation In Vivo

Bacteriophages that infect Gram-negative bacteria often bind to the bacterial surface by interaction of specific proteins with lipopolysaccharide (LPS). Short tail fiber proteins (tail adhesin, gp12) mediate adsorption of T4-like bacteriophages to Escherichia coli, binding surface proteins or LPS. Produced as a recombined protein, gp12 retains its ability to bind LPS. Since LPS is able to exert a major impact on the immune response in animals and in humans, we have tested LPS-binding phage protein gp12 as a potential modulator of the LPS-induced immune response. We have produced tail adhesin gp12 in a bacterial expression system and confirmed its ability to form trimers and to bind lipopolysaccharide in vitro by dynamic light scattering. This product had no negative effect on mammalian cell proliferation in vitro. Further, no harmful effects of this protein were observed in mice. Thus, gp12 was used in combination with LPS in a murine model, and it decreased the inflammatory response to LPS in vivo, as assessed by serum levels of cytokines IL-1 alpha and IL-6 and by histopathological analysis of spleen, liver, kidney and lungs. Thus, in future studies gp12 may be considered as a potential tool for modulation and specifically for counteracting LPS-related physiological effects in vivo

Oral Application of T4 Phage Induces Weak Antibody Production in the Gut and in the Blood

A specific humoral response to bacteriophages may follow phage application for medical purposes, and it may further determine the success or failure of the approach itself. We present a long-term study of antibody induction in mice by T4 phage applied per os: 100 days of phage treatment followed by 112 days without the phage, and subsequent second application of phage up to day 240. Serum and gut antibodies (IgM, IgG, secretory IgA) were analyzed in relation to microbiological status of the animals. T4 phage applied orally induced anti-phage antibodies when the exposure was long enough (IgG day 36, IgA day 79); the effect was related to high dosage. Termination of phage treatment resulted in a decrease of IgA again to insignificant levels. Second administration of phage induces secretory IgA sooner than that induced by the first administrations. Increased IgA level antagonized gut transit of active phage. Phage resistant E. coli dominated gut flora very late, on day 92. Thus, the immunological response emerges as a major factor determining phage survival in the gut. Phage proteins Hoc and gp12 were identified as highly immunogenic. A low response to exemplary foreign antigens (from Ebola virus) presented on Hoc was observed, which suggests that phage platforms can be used in oral vaccine design

Safety Studies of Pneumococcal Endolysins Cpl-1 and Pal

Bacteriophage-derived endolysins have gained increasing attention as potent antimicrobial agents and numerous publications document the in vivo efficacy of these enzymes in various rodent models. However, little has been documented about their safety and toxicity profiles. Here, we present preclinical safety and toxicity data for two pneumococcal endolysins, Pal and Cpl-1. Microarray, and gene profiling was performed on human macrophages and pharyngeal cells exposed to 0.5 µM of each endolysin for six hours and no change in gene expression was noted. Likewise, in mice injected with 15 mg/kg of each endolysin, no physical or behavioral changes were noted, pro-inflammatory cytokine levels remained constant, and there were no significant changes in the fecal microbiome. Neither endolysin caused complement activation via the classic pathway, the alternative pathway, or the mannose-binding lectin pathway. In cellular response assays, IgG levels in mice exposed to Pal or Cpl-1 gradually increased for the first 30 days post exposure, but IgE levels never rose above baseline, suggesting that hypersensitivity or allergic reaction is unlikely. Collectively, the safety and toxicity profiles of Pal and Cpl-1 support further preclinical studies