A trivalent vaccine consisting of "flagellin A+B and pilin" protects against Pseudomonas aeruginosa infection in a murine burn model

Pseudomonas aeruginosa in chronic lung disease: untangling the dysregulated host immune response

Pseudomonas aeruginosa is a highly adaptable opportunistic pathogen capable of exploiting barriers and immune defects to cause chronic lung infections in conditions such as cystic fibrosis. In these contexts, host immune responses are ineffective at clearing persistent bacterial infection, instead driving a cycle of inflammatory lung damage. This review outlines key components of the host immune response to chronic P. aeruginosa infection within the lung, beginning with initial pathogen recognition, followed by a robust yet maladaptive innate immune response, and an ineffective adaptive immune response that propagates lung damage while permitting bacterial persistence. Untangling the interplay between host immunity and chronic P. aeruginosa infection will allow for the development and refinement of strategies to modulate immune-associated lung damage and potentiate the immune system to combat chronic infection more effectively.

Recombinant Pseudomonas aeruginosa flagellin delivered using ferritin nanoparticles provides enhanced cross-protection against lung infection in mice

Increasing prevalence of multidrug- and pan-drug-resistant Pseudomonas aeruginosa (PA) strains has created an urgent need for an effective vaccine. Flagellin is an essential vaccine target because of its contribution to bacterial motility and other pathogenic processes. However, flagellin-based vaccines have not been successful thus far, probably due to a lack of efficient adjuvants or delivery systems. In this study, we genetically fused an A-type flagellin (FliC) to the self-assembled nanocarrier ferritin to construct the nanoparticle vaccine, reFliC-ferritin (reFliC-FN). reFliC-FN formed homogenous nanoparticles and induced a quick T helper 1 (Th1)-predominant immune response, which was quite different from that induced by recombinant FliC alone. In addition, reFliC-FN provided enhanced protection against PA strains carrying the A-type and heterogeneous B-type flagellins. Preliminary safety assays revealed the good biocompatibility and biosafety of reFliC-FN. Therefore, our data highlight the potential of ferritin as an ideal delivery system and suggest reFliC-FN as a promising PA vaccine candidate.

A chimeric vaccine targeting Pseudomonas aeruginosa virulence factors protects mice against lethal infection

Pseudomonas aeruginosa is an important and hazardous nosocomial pathogen in respiratory tract infections and rapidly achieves antibiotic resistance, so it is necessary to develop an effective vaccine to combat the infection. The Type III secretion system (T3SS) protein P. aeruginosa V-antigen (PcrV), outer membrane protein F (OprF), and two kinds of flagellins (FlaA and FlaB) all play important roles in the pathogenesis of P. aeruginosa lung infection and its spread into deeper tissues. In a mouse acute pneumonia model, the protective effects of a chimer vaccine including PcrV, FlaA, FlaB, and OprF (PABF) protein were investigated. PABF immunization prompted robust opsonophagocytic titer of IgG antibodies and decreased bacterial burden, and improved survival afterward intranasal challenge with ten times 50% lethal doses (LD50) of P. aeruginosa strains, indicating its broad-spectrum immunity. Moreover, these findings showed a promise chimeric vaccine candidate to treat and control P. aeruginosa infections.

Immune responses and protective efficacy of a trivalent combination DNA vaccine based on oprL, oprF and flgE genes of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an infectious pathogenic bacteria infecting many different species of animals. Currently, it lacks a commercial vaccine. In this study, three monovalent DNA vaccines (poprL, poprF, and pflgE), three bivalent combination DNA vaccines (poprL+poprF, poprL+pflgE, poprF+pflgE), and a trivalent DNA vaccine (poprL+poprF+pflgE) were constructed. Consequently, we immunised chickens with these DNA vaccines and used inactivated vaccines as the positive controls. Then, the immune efficacy was evaluated through serum antibody detection, a lymphocyte proliferation assay, and cytokine concentration determination. Lastly, we assessed the protection rate through a challenge experiment. Following vaccination, the serum antibody levels induced using these DNA vaccines were different due to the different coating antigens. In the trivalent combination DNA vaccine group, we established that the lymphocyte proliferation (SI values), IFN-γ, IL-2, and IL-4 levels were significantly higher than those of the other six DNA vaccine groups and the inactivated vaccine group. However, the protection provided was slightly lower than that of the inactivated vaccine and higher than those of other DNA vaccines. The protection rate of poprL, poprF, pflgE, poprL+poprF, poprL+pflgE, poprF+pflgE, poprL+poprF+pflgE, and the inactivated vaccine were 50, 45, 60, 75, 80, 80, 90, and 95%, respectively. The results of this study indicated the trivalent DNA vaccine based on oprL, oprF and flgE genes represents a promising approach for the prevention of Pseudomonas aeruginosa infections.

Metallacarborane Derivatives Effective against Pseudomonas aeruginosa and Yersinia enterocolitica

Pseudomonas aeruginosa is an opportunistic human pathogen that has become a nosocomial health problem worldwide. The pathogen has multiple drug removal and virulence secretion systems, is resistant to many antibiotics, and there is no commercial vaccine against it. Yersinia pestis is a zoonotic pathogen that is on the Select Agents list. The bacterium is the deadliest pathogen known to humans and antibiotic-resistant strains are appearing naturally. There is no commercial vaccine against the pathogen, either. In the current work, novel compounds based on metallacarborane cage were studied on strains of Pseudomonas aeruginosa and a Yersinia pestis substitute, Yersinia enterocolitica. The representative compounds had IC₅₀ values below 10 µM against Y. enterocolitica and values of 20–50 μM against P. aeruginosa. Artificial generation of compound-resistant Y. enterocolitica suggested a common mechanism for drug resistance, the first reported in the literature, and suggested N-linked metallacarboranes as impervious to cellular mechanisms of resistance generation. SEM analysis of the compound-resistant strains showed that the compounds had a predominantly bacteriostatic effect and blocked bacterial cell division in Y. enterocolitica. The compounds could be a starting point towards novel anti-Yersinia drugs and the strategy presented here proposes a mechanism to bypass any future drug resistance in bacteria.

Secretory System Components as Potential Prophylactic Targets for Bacterial Pathogens

Bacterial secretory systems are essential for virulence in human pathogens. The systems have become a target of alternative antibacterial strategies based on small molecules and antibodies. Strategies to use components of the systems to design prophylactics have been less publicized despite vaccines being the preferred solution to dealing with bacterial infections. In the current review, strategies to design vaccines against selected pathogens are presented and connected to the biology of the system. The examples are given for Y. pestis, S. enterica, B. anthracis, S. flexneri, and other human pathogens, and discussed in terms of effectiveness and long-term protection.

Evaluation of the immunogenicity and protective ability of a pili subunit, SBP2', of Streptococcus suis serotype 2

Streptococcus suis is an important zoonotic pathogen that leads to huge economic losses in the swine industry. Because of the enormous genetic and phenotypic diversity within S. suis, it is necessary to develop effective vaccines to control this zoonotic pathogen. SBP2' is a major pili subunit in S. suis that belongs to an srtBCD pili cluster and has already been reported to be associated with the pathogenesis of this bacterium. In this study, we aimed to evaluate the immunogenicity and protective ability of SBP2'. The rSBP2' protein was expressed by an Escherichia coli expression system and emulsified with Montanide ISA 201 adjuvant to prepare the subunit vaccine. Through active immune assays, the results showed that rSBP2' exhibited good immunogenicity and could protect mice from a lethal dose challenge. Additionally, the qRT-PCR data showed that the transcription levels of cytokines associated with systemic symptoms caused by S. suis were decreased, indicating that immunization with rSBP2' could protect the host from cytokine storms caused by S. suis. Furthermore, the passive immune assay showed that the humoral immunity induced by rSBP2' played an important role against S. suis infection. Taken together, SBP2' could provide proper immune protection against S. suis challenge and could be a candidate for S. suis subunit vaccine. The results of this study could provide new ideas for the development of effective vaccines against S. suis.

Vaccines for multidrug resistant Gram negative bacteria: lessons from the past for guiding future success

Antimicrobial resistance is a major threat to global public health. Vaccination is an effective approach for preventing bacterial infections, however it has not been successfully applied to infections caused by some of the most problematic multidrug resistant pathogens. In this review, the potential for vaccines to contribute to reducing the burden of disease of infections caused by multidrug resistant Gram negative bacteria is presented. Technical, logistical and societal hurdles that have limited successful vaccine development for these infections in the past are identified, and recent advances that can contribute to overcoming these challenges are assessed. A synthesis of vaccine technologies that have been employed in the development of vaccines for key multidrug resistant Gram negative bacteria is included, and emerging technologies that may contribute to future successes are discussed. Finally, a comprehensive review of vaccine development efforts over the last 40 years for three of the most worrisome multidrug resistant Gram negative pathogens, Acinetobacter baumannii, Klebsiella pneumoniae and Pseudomonas aeruginosa is presented, with a focus on recent and ongoing studies. Finally, future directions for the vaccine development field are highlighted.

Interplay between ESKAPE Pathogens and Immunity in Skin Infections: An Overview of the Major Determinants of Virulence and Antibiotic Resistance

The skin is the largest organ in the human body, acting as a physical and immunological barrier against pathogenic microorganisms. The cutaneous lesions constitute a gateway for microbial contamination that can lead to chronic wounds and other invasive infections. Chronic wounds are considered as serious public health problems due the related social, psychological and economic consequences. The group of bacteria known as ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter sp.) are among the most prevalent bacteria in cutaneous infections. These pathogens have a high level of incidence in hospital environments and several strains present phenotypes of multidrug resistance. In this review, we discuss some important aspects of skin immunology and the involvement of ESKAPE in wound infections. First, we introduce some fundamental aspects of skin physiology and immunology related to cutaneous infections. Following this, the major virulence factors involved in colonization and tissue damage are highlighted, as well as the most frequently detected antimicrobial resistance genes. ESKAPE pathogens express several virulence determinants that overcome the skin's physical and immunological barriers, enabling them to cause severe wound infections. The high ability these bacteria to acquire resistance is alarming, particularly in the hospital settings where immunocompromised individuals are exposed to these pathogens. Knowledge about the virulence and resistance markers of these species is important in order to develop new strategies to detect and treat their associated infections.

Understanding Pseudomonas aeruginosa-Host Interactions: The Ongoing Quest for an Efficacious Vaccine

Pseudomonas aeruginosa is a leading cause of chronic respiratory infections in people with cystic fibrosis (CF), bronchiectasis or chronic obstructive pulmonary disease (COPD), and acute infections in immunocompromised individuals. The adaptability of this opportunistic pathogen has hampered the development of antimicrobial therapies, and consequently, it remains a major threat to public health. Due to its antimicrobial resistance, vaccines represent an alternative strategy to tackle the pathogen, yet despite over 50 years of research on anti-Pseudomonas vaccines, no vaccine has been licensed. Nevertheless, there have been many advances in this field, including a better understanding of the host immune response and the biology of P. aeruginosa. Multiple antigens and adjuvants have been investigated with varying results. Although the most effective protective response remains to be established, it is clear that a polarised Th2 response is sub-optimal, and a mixed Th1/Th2 or Th1/Th17 response appears beneficial. This comprehensive review collates the current understanding of the complexities of P. aeruginosa-host interactions and its implication in vaccine design, with a view to understanding the current state of Pseudomonal vaccine development and the direction of future efforts. It highlights the importance of the incorporation of appropriate adjuvants to the protective antigen to yield optimal protection.