Studies described so far suggest that human β-defensin 2 is an important protein of innate immune response which provides protection for the human organism against invading pathogens of bacterial, viral, fungal, as well as parasitical origin. Its pivotal role in enhancing immunity was proved in infants. It may also be considered a marker of inflammation. Its therapeutic administration has been suggested for maintenance of the balance of systemic homeostasis based on the appropriate composition of the microbiota. It has been suggested that it may be an important therapeutic tool for modulating the response of the immune system in many inflammatory diseases, offering new treatment modalities. For this reason, its properties and role in the human body discussed in this review should be studied in more detail.

Acinetobacter baumannii are bacteria that belong to the critical priority group due to their carbapenems and third generation cephalosporins resistance, which are last-chance antibiotics. The growing multi-drug resistance and the ability of these bacteria to form biofilms makes it difficult to treat infections caused by this species, which often affects people with immunodeficiency or intensive care unit patients. In addition, most of the infections are associated with catheterization of patients. These bacteria are causative agents, inter alia, of urinary tract infections (UTI) which can cause serious medical and social problems, because of treatment difficulties as well as the possibility of recurrence and thus severely decrease patients’ quality of life. Therefore, a promising alternative to standard antibiotic therapy can be bacteriophage therapy, which will generate lower costs and will be safer for the treated patients and has real potential to be much more effective. The aim of the review is to outline the important role of drug-resistant A. baumannii in the pathogenesis of UTI and highlight the potential for fighting these infections with bacteriophage therapy. Further studies on the use of bacteriophages in the treatment of UTIs in animal models may lead to the use of bacteriophage therapy in human urinary tract infections caused by A. baumannii in the future.

The authors emphasize how extremely important it is to highlight the role played by animal models in an attempt to determine possible phage interactions with the organism into which it was introduced as well as to determine the safety and effectiveness of phage therapy in vivo taking into account the individual conditions of a given organism and its physiology. Animal models in which phages are used make it possible, among other things, to evaluate the effective therapeutic dose and to choose the possible route of phage administration depending on the type of infection developed. These results cannot be applied in detail to the human body, but the knowledge gained from animal experiments is invaluable and very helpful. We would like to highlight how useful animal models may be for the possible effectiveness evaluation of phage therapy in the case of infections caused by gram-negative bacteria from the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter species) group of pathogens. In this review, we focus specifically on the data from the last few years.

At present, extracellular vesicles (EVs) are considered key candidates for cell-free therapies, including treatment of allergic and autoimmune diseases. However, their therapeutic effectiveness, dependent on proper targeting to the desired cells, is significantly limited due to the reduced bioavailability resulting from their rapid clearance by the cells of the mononuclear phagocyte system (MPS). Thus, developing strategies to avoid EV elimination is essential when applying them in clinical practice. On the other hand, malfunctioning MPS contributes to various immune-related pathologies. Therapeutic reversal of these effects with EVs would be beneficial and could be achieved, for example, by modulating the macrophage phenotype or regulating antigen presentation by dendritic cells. Additionally, intended targeting of EVs to MPS macrophages for replication and repackaging of their molecules into new vesicle subtype can allow for their specific targeting to appropriate populations of acceptor cells. Herein, we briefly discuss the under-explored aspects of the MPS-EV interactions that undoubtedly require further research in order to accelerate the therapeutic use of EVs.

Bacteriophages are natural biological entities that limit the growth and amplification of bacteria. They are important stimulators of evolutionary variability in bacteria, and currently are considered a weapon against antibiotic resistance of bacteria. Nevertheless, apart from their antibacterial activity, phages may act as modulators of mammalian immune responses. In this paper, we focus on temperate phages able to execute the lysogenic development, which may shape animal or human immune response by influencing various processes, including phagocytosis of bacterial invaders and immune modulation of mammalian host cells.

In an era of antibiotic therapy crisis caused by spreading antimicrobial resistance, and when recurrent urinary tract infections constitute a serious social and medical problem, the isolation and complex characterization of phages with a potential therapeutic application represents a promising solution. It is an inevitable, and even a necessary direction in the development of current phage research. In this paper, we present two newly isolated myoviruses that show lytic activity against multidrug-resistant clinical isolates of Enterobacter spp. (E. cloacae, E. hormaechei, and E. kobei), the genomes of which belong to a poorly represented phage group. Both phages were classified as part of the Tevenvirinae subfamily (Entb_43 was recognized as Karamvirus and Entb_45 as Kanagawavirus). Phage lytic spectra ranging from 40 to 60% were obtained. The most effective phage-to-bacteria ratios (MOI = 0.01 and MOI = 0.001) for both the phage amplification and their lytic activity against planktonic bacteria were also estimated. Complete adsorption to host cells were obtained after about 20 min for Entb_43 and 10 min for Entb_45. The phage lysates retained their initial titers even during six months of storage at both −70 °C and 4 °C, whereas storage at 37 °C caused a complete loss in their activity. We showed that phages retained their activity after incubation with solutions of silver and copper nanoparticles, which may indicate possible synergistic antibacterial activity. Moreover, a significant reduction in phage titers was observed after incubation with a disinfectant containing octenidinum dihydrochloridum and phenoxyethanol, as well as with 70% ethanol. The observed maintenance of phage activity during incubation in a urine sample, along with other described properties, may suggest a therapeutic potential of phages at the infection site after intravesical administration.