Existing antibacterial vaccines

Biomimetic cell membrane-coated poly(lactic-co-glycolic acid) nanoparticles for biomedical applications

Poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) are commonly used for drug delivery because of their favored biocompatibility and suitability for sustained and controlled drug release. To prolong NP circulation time, enable target-specific drug delivery and overcome physiological barriers, NPs camouflaged in cell membranes have been developed and evaluated to improve drug delivery. Here, we discuss recent advances in cell membrane-coated PLGA NPs, their preparation methods, and their application to cancer therapy, management of inflammation, treatment of cardiovascular disease and control of infection. We address the current challenges and highlight future research directions needed for effective use of cell membrane-camouflaged NPs.

MDR Pumps as Crossroads of Resistance: Antibiotics and Bacteriophages

At present, antibiotic resistance represents a global problem in modern medicine. In the near future, humanity may face a situation where medicine will be powerless against resistant bacteria and a post-antibiotic era will come. The development of new antibiotics is either very expensive or ineffective due to rapidly developing bacterial resistance. The need to develop alternative approaches to the treatment of bacterial infections, such as phage therapy, is beyond doubt. The cornerstone of bacterial defense against antibiotics are multidrug resistance (MDR) pumps, which are involved in antibiotic resistance, toxin export, biofilm, and persister cell formation. MDR pumps are the primary non-specific defense of bacteria against antibiotics, while drug target modification, drug inactivation, target switching, and target sequestration are the second, specific line of their defense. All bacteria have MDR pumps, and bacteriophages have evolved along with them and use the bacteria’s need for MDR pumps to bind and penetrate into bacterial cells. The study and understanding of the mechanisms of the pumps and their contribution to the overall resistance and to the sensitivity to bacteriophages will allow us to either seriously delay the onset of the post-antibiotic era or even prevent it altogether due to phage-antibiotic synergy.

Immunopeptidomics for next-generation bacterial vaccine development

Antimicrobial resistance is an increasing global threat and alternative treatments substituting failing antibiotics are urgently needed. Vaccines are recognized as highly effective tools to mitigate antimicrobial resistance; however, the selection of bacterial antigens as vaccine candidates remains challenging. In recent years, advances in mass spectrometry-based proteomics have led to the development of so-called immunopeptidomics approaches that allow the untargeted discovery of bacterial epitopes that are presented on the surface of infected cells. Especially for intracellular bacterial pathogens, immunopeptidomics holds great promise to uncover antigens that can be encoded in viral vector- or nucleic acid-based vaccines. This review provides an overview of immunopeptidomics studies on intracellular bacterial pathogens and considers future directions and challenges in advancing towards next-generation vaccines.

Antimicrobial Nanogels with Nanoinjection Capabilities for Delivery of the Hydrophobic Antibacterial Agent Triclosan

With the ever-growing problem of antibiotic resistance, developing antimicrobial strategies is urgently needed. Herein, a hydrophobic drug delivery nanocarrier is developed for combating planktonic bacteria that enhances the efficiency of the hydrophobic antimicrobial agent, Triclosan, up to a 1000 times. The poly(N-isopropylacrylamide-co-N-[3-(dimethylamino)propyl]methacrylamide), p(NIPAM-co-DMAPMA), based nanogel is prepared via a one-pot precipitation polymerization, followed by quaternization with 1-bromododecane to form hydrophobic domains inside the nanogel network through intraparticle self-assembly of the aliphatic chains (C12). Triclosan, as the model hydrophobic antimicrobial drug, is loaded within the hydrophobic domains inside the nanogel. The nanogel can adhere to the bacterial cell wall via electrostatic interactions and induce membrane destruction via the insertion of the aliphatic chains into the cell membrane. The hydrophobic antimicrobial Triclosan can be actively injected into the cell through the destroyed membrane. This approach dramatically increases the effective concentration of Triclosan at the bacterial site. Both the minimal inhibitory concentration and minimal bactericidal concentration against the Gram-positive bacteria S. aureus and S. epidermidis decreased 3 orders of magnitude, compared to free Triclosan. The synergy of physical destruction and active nanoinjection significantly enhances the antimicrobial efficacy, and the designed nanoinjection delivery system holds great promise for combating antimicrobial resistance as well as the applications of hydrophobic drugs delivery for many other possible applications.

Predicting the future distribution of antibiotic resistance using time series forecasting and geospatial modelling

Background: Increasing antibiotic resistance in a location may be mitigated by changes in treatment policy, or interventions to limit transmission of resistant bacteria. Therefore, accurate forecasting of the distribution of antibiotic resistance could be advantageous. Two previously published studies addressed this, but neither study compared alternative forecasting algorithms or considered spatial patterns of resistance spread. Methods: We analysed data describing the annual prevalence of antibiotic resistance per country in Europe from 2012 – 2016, and the quarterly prevalence of antibiotic resistance per clinical commissioning group in England from 2015 – 2018. We combined these with data on rates of possible covariates of resistance. These data were used to compare the previously published forecasting models, with other commonly used forecasting models, including one geospatial model. Covariates were incorporated into the geospatial model to assess their relationship with antibiotic resistance. Results: For the European data, which was recorded on a coarse spatiotemporal scale, a naïve forecasting model was consistently the most accurate of any of the forecasting models tested. The geospatial model did not improve on this accuracy. However, it did provide some evidence that antibiotic consumption can partially explain the distribution of resistance. The English data were aggregated at a finer scale, and expected-trend-seasonal (ETS) forecasts were the most accurate. The geospatial model did not significantly improve upon the median accuracy of the ETS model, but it appeared to be less sensitive to noise in the data, and provided evidence that rates of antibiotic prescription and bacteraemia are correlated with resistance. Conclusion: Annual, national-level surveillance data appears to be insufficient for fitting accurate antibiotic resistance forecasting models, but there is evidence that data collected at a finer spatiotemporal scale could be used to improve forecast accuracy. Additionally, incorporating antibiotic prescription or consumption data into the model could improve the predictive accuracy.

Safeguarding intestine cells against enteropathogenic Escherichia coli by intracellular protein reaction, a preventive antibacterial mechanism

A critical problem in the fight against bacterial infection is the rising rates of resistance and the lack of new antibiotics. The discovery of new targets or new antibacterial mechanisms is a potential solution but is becoming more difficult. Here we report an antibacterial mechanism that safeguards intestine cells from enteropathogenic Escherichia coli (EPEC) by shutting down an infection-responsive signal of the host intestine cell. A key step in EPEC infection of intestinal cells involves Tir-induced actin reorganization. Nck mediates this event by binding with Tir through its SH2 domain (Nck-SH2) and with WIP through its second SH3 domain (Nck-SH3.2). Here we report the design of a synthetic peptide that reacts precisely with a unique cysteine of the Nck-SH3.2 domain, blocks the binding site of the Nck protein, and prevents EPEC infection of Caco-2 cells. Oral update of this nontoxic peptide before EPEC administration safeguards mice from EPEC infection and diarrhea. This study demonstrates domain-specific blockage of an SH3 domain of a multidomain adaptor protein inside cells and the inhibition of Tir-induced rearrangement of the host actin cytoskeleton as a previously unknown antibacterial mechanism.

Multiantigenic Nanotoxoids for Antivirulence Vaccination against Antibiotic-Resistant Gram-Negative Bacteria

Infections caused by multidrug-resistant Gram-negative bacteria have emerged as a major threat to public health worldwide. The high mortality and prevalence, along with the slow pace of new antibiotic discovery, highlight the necessity for new disease management paradigms. Here, we report on the development of a multiantigenic nanotoxoid vaccine based on macrophage membrane-coated nanoparticles for eliciting potent immunity against pathogenic Pseudomonas aeruginosa. The design of this biomimetic nanovaccine leverages the specific role of macrophages in clearing pathogens and their natural affinity for various virulence factors secreted by the bacteria. It is demonstrated that the macrophage nanotoxoid is able to display a wide range of P. aeruginosa antigens, and the safety of the formulation is confirmed both in vitro and in vivo. When used to vaccinate mice via different administration routes, the nanotoxoid is capable of eliciting strong humoral immune responses that translate into enhanced protection against live bacterial infection in a pneumonia model. Overall, the work presented here provides new insights into the design of safe, multiantigenic antivirulence vaccines using biomimetic nanotechnology and the application of these nanovaccines toward the prevention of difficult-to-treat Gram-negative infections.

Biomimetic Nanoparticle Vaccines for Cancer Therapy

It is currently understood that, in order for a tumor to successfully grow, it must evolve means of evading immune surveillance. In the past several decades, researchers have leveraged increases in our knowledge of tumor immunology to develop therapies capable of augmenting endogenous immunity and eliciting strong antitumor responses. In particular, the goal of anticancer vaccination is to train the immune system to properly utilize its own resources in the fight against cancer. Although attractive in principle, there are currently only limited examples of anticancer vaccines that have been successfully translated to the clinic. Recently, there has been a significant push towards the use of nanotechnology for designing vaccine candidates that exhibit enhanced potency and specificity. In this progress report, we discuss recent developments in the field of anticancer nanovaccines. By taking advantage of the flexibility offered by nanomedicine to purposefully program immune responses, this new generation of vaccines has the potential to address many of the hurdles facing traditional platforms. A specific emphasis is placed on the emergence of cell membrane-coated nanoparticles, a novel biomimetic platform that can be used to generate personalized nanovaccines that elicit strong, multi-antigenic antitumor responses.

Toxoid Vaccination against Bacterial Infection Using Cell Membrane-Coated Nanoparticles

As nanoparticles exhibit unique properties attractive for vaccine development, they have been progressively implemented as antigen delivery platforms and immune potentiators. Recently, cell membrane-coated nanoparticles have provided a novel approach for intercepting and neutralizing bacterial toxins by leveraging their natural affinity to cellular membranes. Such toxin-nanoparticle assemblies, termed nanotoxoids, allow rapid loading of different types of toxins and have been investigated for their ability to effectively confer protection against bacterial infection. This topical review will cover the current progress in antibacterial vaccine nanoformulations and highlight the nanotoxoid platform as a novel class of nanoparticulate vaccine. We aim to provide insights into the potential of nanotoxoids as a platform that is facile to implement and can be broadly applied to help address the rising threat of super pathogens.

Cell Membrane-Coated Nanoparticles As an Emerging Antibacterial Vaccine Platform

Nanoparticles have demonstrated unique advantages in enhancing immunotherapy potency and have drawn increasing interest in developing safe and effective vaccine formulations. Recent technological advancement has led to the discovery and development of cell membrane-coated nanoparticles, which combine the rich functionalities of cellular membranes and the engineering flexibility of synthetic nanomaterials. This new class of biomimetic nanoparticles has inspired novel vaccine design strategies with strong potential for modulating antibacterial immunity. This article will review recent progress on using cell membrane-coated nanoparticles for antibacterial vaccination. Specifically, two major development strategies will be discussed, namely (i) vaccination against virulence factors through bacterial toxin sequestration; and (ii) vaccination against pathogens through mimicking bacterial antigen presentation.

Antimicrobial Activities of a Plethora of Medicinal Plant Extracts and Hydrolates against Human Pathogens and Their Potential to Reverse Antibiotic Resistance

Microbial infections till date remain a scourge of humanity due to lack of vaccine against some infections, emergence of drug resistant phenotypes, and the resurgence of infections amongst others. Continuous quest for novel therapeutic approaches remains imperative. Here we (i) assessed the effects of extracts/hydrolates of some medicinal plants on pathogenic microorganisms and (ii) evaluated the inhibitory potential of the most active ones in combination with antibiotics. Extract E03 had the highest DZI (25 mm). Extracts E05 and E06 were active against all microorganisms tested. The MICs and MBCs of the methanol extracts ranged from 16.667 × 10³  μg/mL to 2 μg/mL and hydrolates from 0.028 to 333333 ppm. Extract E30 had the highest activity especially against S. saprophyticus (MIC of 6 ppm) and E. coli (MIC of 17 ppm). Combination with conventional antibiotics was shown to overcome resistance especially with E30. Analyses of the extracts revealed the presence of alkaloids, flavonoids, triterpenes, steroids, phenols, and saponins. These results justify the use of these plants in traditional medicine and the practice of supplementing decoctions/concoctions with conventional antibiotics. Nauclea pobeguinii (E30), the most active and synergistic of all these extracts, and some hydrolates with antimicrobial activity need further exploration for the development of novel antimicrobials.

Modulating antibacterial immunity via bacterial membrane-coated nanoparticles

Synthetic nanoparticles coated with cellular membranes have been increasingly explored to harness natural cell functions toward the development of novel therapeutic strategies. Herein, we report on a unique bacterial membrane-coated nanoparticle system as a new and exciting antibacterial vaccine. Using Escherichia coli as a model pathogen, we collect bacterial outer membrane vesicles (OMVs) and successfully coat them onto small gold nanoparticles (AuNPs) with a diameter of 30 nm. The resulting bacterial membrane-coated AuNPs (BM-AuNPs) show markedly enhanced stability in biological buffer solutions. When injected subcutaneously, the BM-AuNPs induce rapid activation and maturation of dendritic cells in the lymph nodes of the vaccinated mice. In addition, vaccination with BM-AuNPs generates antibody responses that are durable and of higher avidity than those elicited by OMVs only. The BM-AuNPs also induce an elevated production of interferon gamma (INFγ) and interleukin-17 (IL-17), but not interleukin-4 (IL-4), indicating its capability of generating strong Th1 and Th17 biased cell responses against the source bacteria. These observed results demonstrate that using natural bacterial membranes to coat synthetic nanoparticles holds great promise for designing effective antibacterial vaccines.