Bacteriophages are viruses infecting bacterial cells. Since there is a lack of specific receptors for bacteriophages on eukaryotic cells, these viruses were for a long time considered to be neutral to animals and humans. However, studies of recent years provided clear evidence that bacteriophages can interact with eukaryotic cells, significantly influencing the functions of tissues, organs, and systems of mammals, including humans. In this review article, we summarize and discuss recent discoveries in the field of interactions of phages with animal and human organisms. Possibilities of penetration of bacteriophages into eukaryotic cells, tissues, and organs are discussed, and evidence of the effects of phages on functions of the immune system, respiratory system, central nervous system, gastrointestinal system, urinary tract, and reproductive system are presented and discussed. Modulations of cancer cells by bacteriophages are indicated. Direct and indirect effects of virulent and temperate phages are discussed. We conclude that interactions of bacteriophages with animal and human organisms are robust, and they must be taken under consideration when using these viruses in medicine, especially in phage therapy, and in biotechnological applications.

BackgroundBacterial spores have been utilized as platforms for protein display. The best studied display systems are based on Bacillus subtilis spores in which several coat proteins have successfully been used as anchors for heterologous protein. Increasing knowledge about spore coat structure enables selection of new anchor proteins such as CotZ and CgeA. Here we describe a system of vectors for display of proteins on the surface of B. subtilis spores.ResultsWe have designed and constructed a set of 16 vectors for ectopic integration which can be used for spore surface display of heterologous proteins. There is a selection of five coat proteins: CotB, CotC, CotG, CotZ and CgeA which can be used for construction of fusions. Three of these (CotB, CotC and CotG) enable obtaining N-terminal and C-terminal fusions and other two (CotZ and CgeA) are designed to produce C-terminal fusions only. All the vectors enable introduction of an additional peptide linker between anchor and displayed protein to enhance surface display. As a selection marker trophic genes are used. Additionally we describe an example application of presented vector system to display CagA protein of Helicobacter pylori in fusion with CgeA spore coat protein.ConclusionsDescribed system of vectors is a versatile tool for display of heterologous proteins on the surface of B. subtilis spores. Such recombinant spores can be further used as for example biocatalysts or antigen-carriers in vaccine formulations. The lack of antibiotic resistance genes in the system makes such spores an interesting option for applications in which a possible release to the environment can occur.

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The endospores of Bacillus subtilis are now widely used as a platform for presentation of heterologous proteins and due to their safety record and high resistance to harsh environmental conditions can be considered as potential vehicles for oral vaccination. In this research we show that recombinant B. subtilis spores presenting a fragment of the Helicobacter acinonychis UreB protein and expressing the ureB gene under vegetative promoter elicit a strong cellular immune response in orally immunized mice when co-administered with spores presenting IL-2. We show for the first time the successful application of two types of recombinant spores, one carrying an antigen and the other an adjuvant, in a single oral immunization.

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Phage therapy is a promising alternative treatment of bacterial infections in human and animals. Nevertheless, despite the appearance of many bacterial strains resistant to antibiotics, these drugs still remain important therapeutics used in human and veterinary medicine. Although experimental phage therapy of infections caused by Salmonella enterica was described previously by many groups, those studies focused solely on effects caused by bacteriophages. Here, we compared the use of phage therapy (employing a cocktail composed of two previously isolated and characterized bacteriophages, vB_SenM-2 and vB_Sen-TO17) and antibiotics (enrofloxacin and colistin) in chickens infected experimentally with S. enterica serovar Typhimurium. We found that the efficacies of both types of therapies (i.e. the use of antibiotics and phage cocktail) were high and very similar to one another when the treatment was applied shortly (one day) after the infection. Under these conditions, S. Typhimurium was quickly eliminated from the gastrointestinal tract (GIT), to the amount not detectable by the used methods. However, later treatment (2 or 4 days after detection of S. Typhimurium in chicken feces) with the phage cocktail was significantly less effective. Bacteriophages remained in the GIT for up to 2-3 weeks, and then were absent in feces and cloaca swabs. Interestingly, both phages could be found in various organs of chickens though with a relatively low abundance. No development of resistance of S. Typhimurium to phages or antibiotics was detected during the experiment. Importantly, although antibiotics significantly changed the GIT microbiome of chickens in a long-term manner, analogous changes caused by phages were transient, and the microbiome normalized a few weeks after the treatment. In conclusion, phage therapy against S. Typhimurium infection in chickens appeared as effective as antibiotic therapy (with either enrofloxacin or colistin), and less invasive than the use the antibiotics as fewer changes in the microbiome were observed.

Current progress in research on vaccines against Helicobacter pylori emphasizes the significance of eliciting the Th1/Th17-polarized immune response. Such polarization can be achieved by selection of appropriate antigen and adjuvant. In this study, we wanted to check the polarization of the immune response elicited by UreB protein of Helicobacter acinonychis delivered by recombinant Bacillus subtilis spores upon oral immunization. B. subtilis spores presenting fragment of UreB protein and able to express entire UreB in vegetative cells after germination were orally administered to mice along with aluminum hydroxide or recombinant spores presenting IL-2 as an adjuvant. The pattern of cytokines secreted by sensitized splenocytes assessed by the cytometric bead array clearly indicated polarization of the immune response toward both Th1 and Th17 in mice immunized with the use of above-mentioned adjuvants. Obtained result is promising regarding the usage of recombinant spores in formulations of vaccines against H. pylori and line up with the current state of research emphasizing the key role of appropriate adjuvants.

IntroductionThe problem of antibiotic resistance is a global one, involving many industries and entailing huge financial outlays. Therefore, the search for alternative methods to combat drug-resistant bacteria has a priority status. Great potential is seen in bacteriophages which have the natural ability to kill bacterial cells. Bacteriophages also have several advantages over antibiotics. Firstly, they are considered ecologically safe (harmless to humans, plants and animals). Secondly, bacteriophages preparations are readily producible and easy to apply. However, before bacteriophages can be authorized for medical and veterinary use, they must be accurately characterized in vitro and in vivo to determinate safety.MethodsTherefore, the aim of this study was to verify for the first time the behavioral and immunological responses of both male and female mice (C57BL/6J) to bacteriophage cocktail, composed of two bacteriophages, and to two commonly used antibiotics, enrofloxacin and tetracycline. Animal behavior, the percentage of lymphocyte populations and subpopulations, cytokine concentrations, blood hematological parameters, gastrointestinal microbiome analysis and the size of internal organs, were evaluated.ResultsUnexpectedly, we observed a sex-dependent, negative effect of antibiotic therapy, which not only involved the functioning of the immune system, but could also significantly impaired the activity of the central nervous system, as manifested by disruption of the behavioral pattern, especially exacerbated in females. In contrast to antibiotics, complex behavioral and immunological analyses confirmed the lack of adverse effects during the bacteriophage cocktail administration.DiscussionThe mechanism of the differences between males and females in appearance of adverse effects, related to the behavioral and immune functions, in the response to antibiotic treatment remains to be elucidated. One might imagine that differences in hormones and/or different permeability of the blood-brain barrier can be important factors, however, extensive studies are required to find the real reason(s).