Bacterial biofilms pose a major threat to public health, as they are associated with at least two thirds of all infections. They are highly resilient and render conventional antibiotics inefficient. As a part of the innate immune system, antimicrobial peptides have drawn attention within the last decades, as some of them are able to eradicate biofilms at sub-minimum inhibitory concentration (MIC) levels. However, peptides possess a number of disadvantages, such as susceptibility to proteolytic degradation, pH and/or salinity-dependent activity and loss of activity due to binding to serum proteins. Hence, proteolytically stable peptidomimetics were designed to overcome these drawbacks. This paper summarizes the current peptide and peptidomimetic strategies for combating bacteria-associated biofilm infections, both in respect to soluble and surface-functionalized solutions.

Among non-mammalian infection model organisms, the larvae of the greater wax moth Galleria mellonella have seen increasing popularity in recent years. Unlike other invertebrate models, these larvae can be incubated at 37 °C and can be dosed relatively precisely. Despite the increasing number of publications describing the use of this model organism, there is a high variability with regard to how the model is produced in different laboratories, with respect to larva size, age, origin, storage, and rest periods, as well as dosing for infection and treatment. Here, we provide suggestions regarding how some of these factors can be approached, to facilitate the comparability of studies between different laboratories. We introduce a linear regression curve correlating the total larva weight to the liquid volume in order to estimate the in vivo concentration of pathogens and the administered drug concentration. Finally, we discuss several other aspects, including in vivo antibiotic stability in larvae, the infection doses for different pathogens and suggest guidelines for larvae selection.

Antimicrobial peptides can have a dual role with both antimicrobial activity against a broad range of bacteria and immunomodulatory effect, making them attractive as therapeutic treatment of difficult wounds. Nisin A is widely known for its antimicrobial activity, and a preliminary study demonstrated that it increased wound closure, but the mechanism behind its effect is unknown. The aim of this study is to elucidate the wound healing potential of Nisin A and the mechanism behind. First, an epithelial and endothelial cell line, human keratinocyte (HaCaT) and human umbilical vein endothelial cell, were used to demonstrate migration and proliferation effects in vitro. From HaCaT cells and peripheral blood mononuclear cell, changes in cytokine levels were shown by quantitative polymerase chain reaction and enzyme‐linked immunosorbent assay. Second, the ex vivo porcine wound healing model was used to investigate the re‐epithelization potential of Nisin A. Finally, the model Galleria mellonella was used to confirm antimicrobial activity and to investigate potential immunomodulatory effects in vivo. Here, we demonstrated that Nisin A affected migration significantly of both human umbilical vein endothelial cell and HaCaT cells (p < 0.05) but not proliferation, potentially by decreasing the levels of proinflammatory cytokines tumor necrosis factor‐α, interleukin‐6, and interleukin‐8 (p < 0.001). Furthermore, Nisin A treatment diminished lipopolysaccharide‐induced tumor necrosis factor‐α levels from peripheral blood mononuclear cells and monocyte chemoattractant protein‐1 from HaCaT cells (p < 0.001). Furthermore, Nisin A did not affect proliferation ex vivo either but increased re‐epithelization of the porcine skin. Nisin A improved survival of G. mellonella significantly from Staphylococcus epidermidis (p < 0.001) but not from Escherichia coli, indicating that Nisin A did not help the larvae to survive the infection in a different than direct antimicrobial way. All together this makes Nisin A a potential treatment to use in wound healing, as it increases the mobility of skin cells, dampens the effect of lipopolysaccharide and proinflammatory cytokines, and decreases bacterial growth.

There is a need for the rational design of safe and effective vaccines to protect against chronic bacterial pathogens such as Mycobacterium tuberculosis and Mycobacterium avium subsp. paratuberculosis in a number of species. One of the main challenges for vaccine development is the lack of safe adjuvants that induce protective immune responses. Cationic Adjuvant Formulation 01 (CAF01)—an adjuvant based on trehalose dibehenate (TDB) and targeting the Mincle receptor—has entered human trials based on promising pre-clinical results in a number of species. However, in cattle CAF01 only induces weak systemic immune responses. In this study, we tested the ability of three pattern recognition receptors, either alone or in combination, to activate bovine monocytes and macrophages. We found that addition of the TLR3 agonist, polyinosinic:polycytidylic acid (Poly(I:C)) to either one of the Mincle receptor agonists, TDB or monomycoloyl glycerol (MMG), enhanced monocyte activation, and calves vaccinated with CAF09 containing MMG and Poly(I:C) had increased cell-mediated and humoral immune response compared to CAF01 vaccinated animals. In contrast to the highly reactogenic Montanide ISA 61 VG, CAF09-primed T cells maintained a higher frequency of polyfunctional CD4+ T cells (IFN-γ+ TNF-α+ IL-2+). In conclusion, CAF09 supports the development of antibodies along with a high-quality cell-mediated immune response and is a promising alternative to oil-in-water adjuvant in cattle and other ruminants.

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