Cellular and humoral systemic and mucosal immune responses stimulated in volunteers by an oral polybacterial immunomodulator "Dentavax"

Decoding virulence and resistance in Klebsiella pneumoniae: Pharmacological insights, immunological dynamics, and in silico therapeutic strategies

Klebsiella pneumoniae (K. pneumoniae) has become a serious global health concern due to its rising virulence and antibiotic resistance. As one of the leading members of ESKAPE pathogens, it plays a major role in a wide range of infections that cause pneumonia, urinary tract infections, and bacteremia, especially in immunocompromised and hospitalized patients. The recent increase in multidrug-resistant (MDR) and hypervirulent (hvKP) strains due to the production of extended-spectrum beta-lactamases (ESBLs) and carbapenemases, has greatly limited therapeutic options that highlights the need for novel approaches to combat the pathogen. This review outlines the virulence mechanisms, profiles of antibiotic resistance, and immune evasion strategies in K. pneumoniae. Also, it points out the role of capsular polysaccharides, lipopolysaccharides, and fimbriae in host colonization and immune evasion. Additionally, the review discusses the emerging therapeutic strategies of vaccine development, computational drug discovery, and the use of artificial intelligence (AI). The progress achieved in reverse vaccinology and structural biology enables the identification of new drug and vaccine targets, whereas AI and machine learning (ML) stand out as powerful candidates for high-throughput screening and drug design. However, challenges with antigenic variability, safety, and the need to collaborate globally still exist. This review focuses on the need for interdisciplinary approaches involving molecular biology and immunology with computational sciences to address K. pneumoniae infections and provide appropriate therapies in the era of antibiotic resistance.

A Narrative Review of Periodontal Vaccines: Hope or Hype?

Globally, periodontal diseases, mainly driven by polymicrobial biofilms, are a widespread concern of social medicine due to their considerable incidence and tie-up to systemic disorders like diabetes, cardiovascular diseases, and complications during pregnancy. Traditional treatments focus on mechanical debridement and antimicrobial therapies, but these approaches have limitations, including recurrence and antibiotic resistance. Periodontal vaccines offer a promising alternative by targeting the immunological mechanisms underlying periodontal disease. This review explores the current state of periodontal vaccine development, highlighting key antigens, vaccine delivery systems, and preclinical and clinical advancements. Special emphasis is placed on antigen selection, host variability, immune tolerance, and future directions to overcome these barriers. This article highlights the advancements and challenges in periodontal vaccine research, offering insights into the capability of immunoprophylaxis as a groundbreaking way to manage periodontal diseases.

Computational strategies in Klebsiella pneumoniae vaccine design: navigating the landscape of in silico insights

The emergence of multidrug-resistant Klebsiella pneumoniae poses a grave threat to global public health, necessitating urgent strategies for vaccine development. In this context, computational tools have emerged as indispensable assets, offering unprecedented insights into klebsiellal biology and facilitating the design of effective vaccines. Here, a review of the application of computational methods in the development of K. pneumoniae vaccines is presented, elucidating the transformative impact of in silico approaches. Through a systematic exploration of bioinformatics, structural biology, and immunoinformatics techniques, the complex landscape of K. pneumoniae pathogenesis and antigenicity was unravelled. Key insights into virulence factors, antigen discovery, and immune response mechanisms are discussed, highlighting the pivotal role of computational tools in accelerating vaccine development efforts. Advancements in epitope prediction, antigen selection, and vaccine design optimisation are examined, highlighting the potential of in silico approaches to update vaccine development pipelines. Furthermore, challenges and future directions in leveraging computational tools to combat K. pneumoniae are discussed, emphasizing the importance of multidisciplinary collaboration and data integration. This review provides a comprehensive overview of the current state of computational contributions to K. pneumoniae vaccine development, offering insights into innovative strategies for addressing this urgent global health challenge.

Klebsiella pneumoniae Lipopolysaccharide as a Vaccine Target and the Role of Antibodies in Protection from Disease

Klebsiella pneumoniae is well recognized as a serious cause of infection in healthcare-associated settings and immunocompromised individuals; however, accumulating evidence from resource-limited nations documents an alarming rise in community-acquired K. pneumoniae infections, manifesting as bacteremia and pneumonia as well as neonatal sepsis. The emergence of hypervirulent and antibiotic-resistant K. pneumoniae strains threatens treatment options for clinicians. Effective vaccination strategies could represent a viable alternative that would both preempt the need for antibiotics to treat K. pneumoniae infections and reduce the burden of K. pneumoniae disease globally. There are currently no approved K. pneumoniae vaccines. We review the evidence for K. pneumoniae lipopolysaccharide (LPS) as a vaccine and immunotherapeutic target and discuss the role of antibodies specific for the core or O-antigen determinants within LPS in protection against Klebsiella spp. disease. We expand on the known role of the Klebsiella spp. capsule and O-antigen modifications in antibody surface accessibility to LPS as well as the in vitro and in vivo effector functions reported for LPS-specific antibodies. We summarize key hypotheses stemming from these studies, review the role of humoral immunity against K. pneumoniae O-antigen for protection, and identify areas requiring further research.

Exploring the journey: A comprehensive review of vaccine development against Klebsiella pneumoniae

Klebsiella pneumoniae, a prominent nosocomial pathogen, poses a critical global health threat due to its multidrug-resistant (MDR) and hypervirulent strains. This comprehensive review focuses into the complex approaches undertaken in the development of vaccines against K. pneumoniae. Traditional methods, such as whole-cell and ribosomal-based vaccines, are compared with modern strategies, including DNA and mRNA vaccines, and extracellular vesicles (EVs), among others. Each method presents unique advantages and challenges, emphasising the complexity of developing an effective vaccine against this pathogen. Significant advancements in computational tools and artificial intelligence (AI) have revolutionised antigen identification and vaccine design, enhancing the precision and efficiency of developing multiepitope-based vaccines. The review also highlights the potential of glycomics and immunoinformatics in identifying key antigenic components and elucidating immune evasion mechanisms employed by K. pneumoniae. Despite progress, challenges remain in ensuring the safety, efficacy, and manufacturability of these vaccines. Notably, EVs demonstrate promise due to their intrinsic adjuvant properties and ability to elicit robust immune responses, although concerns regarding inflammation and antigen variability persist. This review provides a critical overview of the current landscape of K. pneumoniae vaccine development, stressing the need for continued innovation and interdisciplinary collaboration to address this pressing public health issue. The integration of advanced computational methods and AI holds the potential to accelerate the development of effective immunotherapies, paving the way for novel vaccines against MDR K. pneumoniae.

Human vaccine candidates for infections caused by Klebsiella pneumoniae: A systematic review

Background and Aims

There are many difficulties in treating Klebsiella pneumoniae, necessitating the creation of more preventative/therapeutic measures like vaccinations. However, after numerous attempts, there is still no authorized and widely accessible vaccine. The present study aimed to systematically review published studies on K. pneumoniae vaccines in human subjects/samples.

Methods

To find published studies, several electronic databases, including Scopus, PubMed, Web of Science, ClinicalKey, ClinicalTrials.gov, and Cochrane Library were searched without time limitation using the appropriate keywords. Studies were scrutinized, and the information from those that met our inclusion criteria was gathered and analyzed.

Results

In total, 691 studies were found, of which 14 articles were included for systematic review. Bacterial lysate containing K. pneumoniae was the most studied vaccine candidate. As the main indicator of human immune responses to K. pneumoniae, antibody responses were determined by most studies. The antigen amount, the route of immunization, and the immunization schedule were varying in the studies and were chosen based on several factors such as the disease model, the vaccine type, the vaccination setting (prophylactic or therapeutic), and so on.

Conclusion

The majority of studies asserted that their vaccination was efficient and safe, which was demonstrated by a decrease in the rate of infections and the induction of protective antibody, cell-dependent, and/or cytokine responses. Altogether, the information provided here will help researchers examine the K. pneumoniae vaccine candidates more closely and take future actions that will be more consistently successful.

Low rate of asymptomatic carriage and salivary immunoglobulin A response to Group A Streptococci in the healthy adult population in Finland

Streptococcus pyogenes, also called group A streptococcus (GAS), is a human pathogen causing a wide range of infections ranging from mild tonsillitis to severe, life threatening conditions such as bacteraemia, necrotizing fasciitis, and streptococcal toxic shock syndrome. GAS may also colonise the oropharynx without causing any signs of disease which is known as asymptomatic carriage. This study aims to investigate IgA responses against GAS and oral streptococci from saliva samples collected from healthy Finnish adults. In addition, asymptomatic throat GAS carriage was studied. The study participants consisted of healthy adult volunteers who provided one saliva sample, a throat swab, and a background questionnaire. Total salivary IgA, and GAS specific IgA were analysed from the saliva samples using enzyme-linked immunosorbent assays (ELISA) and the results were compared to oral streptococci specific IgA levels. Asymptomatic GAS throat carriers were identified by bacterial culture, and the isolates were emm typed. Samples from a total of 182 individuals were analysed. The median salivary IgA concentration was 62.9 µg/ml (range 17.3–649.9 µg/ml), and median GAS and oral streptococcal specific IgA concentrations 2.7 and 3.3 arbitrary units (AU, range 1.4–7.4 AU and 1.6–12.0 AU), respectively. Three individuals with asymptomatic GAS throat carriage were identified.

Computational design and characterization of a multiepitope vaccine against carbapenemase-producing Klebsiella pneumoniae strains, derived from antigens identified through reverse vaccinology

Klebsiella pneumoniae is a Gram-negative pathogen of clinical relevance, which can provoke serious urinary and blood infections and pneumonia. This bacterium is a major public health threat due to its resistance to several antibiotic classes. Using a reverse vaccinology approach, 7 potential antigens were identified, of which 4 were present in most of the sequences of Italian carbapenem-resistant K. pneumoniae clinical isolates. Bioinformatics tools demonstrated the antigenic potential of these bacterial proteins and allowed for the identification of T and B cell epitopes. This led to a rational design and in silico characterization of a multiepitope vaccine against carbapenem-resistant K. pneumoniae strains. As adjuvant, the mycobacterial heparin-binding hemagglutinin adhesin (HBHA), which is a Toll-like receptor 4 (TLR-4) agonist, was included, to increase the immunogenicity of the construct. The multiepitope vaccine candidate was analyzed by bioinformatics tools to assess its antigenicity, solubility, allergenicity, toxicity, physical and chemical parameters, and secondary and tertiary structures. Molecular docking binding energies to TLR-2 and TLR-4, two important innate immunity receptors involved in the immune response against K. pneumoniae infections, and molecular dynamics simulations of such complexes supported active interactions. A codon optimized multiepitope sequence cloning strategy is proposed, for production of recombinant vaccine in classical bacterial vectors. Finally, a 3 dose-immunization simulation with the multiepitope construct induced both cellular and humoral immune responses. These results suggest that this multiepitope construct has potential as a vaccination strategy against carbapenem-resistant K. pneumoniae and deserves further validation.

Current Stage in the Development of Klebsiella pneumoniae Vaccines

Klebsiella pneumoniae is a bacterium capable of colonizing mucous membranes, causing serious infections. Widespread antibiotic resistance in K. pneumoniae—either through intrinsic mechanisms or via acquisition from different species, especially in hospital environments—limits the therapeutic options against this pathogen, further aggravating the disease burden. To date, there are no vaccines available against K. pneumoniae infection. Although formulations based on capsular polysaccharides have been proposed, the high variability in capsular serotypes limits vaccine coverage. Recombinant vaccines based on surface exposed bacterial antigens are a promising alternative owing to their conservation among different serotypes and accessibility to the immune system. Many vaccine candidates have been proposed, some of which have reached clinical trials. The present review summarizes the current status of K. pneumoniae vaccine development. Different strategies including whole cell vaccines, outer membrane vesicles (OMVs), ribosome, polysaccharide, lipopolysaccharide (LPS), and protein-based formulations are discussed. The contribution of antibody and cell-mediated responses is also presented. In summary, K. pneumoniae vaccines are feasible and a promising strategy to prevent infections and to reduce the antimicrobial resistance burden worldwide.

Progress towards the development of Klebsiella vaccines

Introduction: Klebsiella pneumoniae (KP) are a leading cause of healthcare-associated infections. The dramatic increase in microbial resistance to third-generation cephalosporin and carbapenem 'front line' antimicrobial agents and the paucity of new antimicrobials have left clinicians with few therapeutic options and resulted in increased morbidity and mortality. Vaccines may reduce the incidence of infections thereby reducing the necessity for antimicrobials and are not subject to antimicrobial resistance mechanisms. Areas covered: We review whole cell, subunit, capsular polysaccharide (CPS), O polysaccharide (OPS) and conjugate vaccines against KP infection, as well as alternative KP vaccine platforms. Expert opinion: Vaccine-induced antibodies to KP CPS have been protective in preclinical studies, but the number of CPS types (>77) makes vaccines against this virulence factor less feasible. Since four OPS serotypes account of ~80% of invasive KP infections and anti-OPS antibodies are also protective in preclinical studies, both OPS-based conjugate and multiple antigen presenting system (MAPS) vaccines are in active development. Vaccines based on other KP virulence factors, such as outer membrane proteins, type 3 fimbriae (MrkA) and siderophores are at earlier stages of development. Novel strategies for the clinical testing of KP vaccines need to be developed.

Agglutination by anti-capsular polysaccharide antibody is associated with protection against experimental human pneumococcal carriage

The ability of pneumococcal conjugate vaccine (PCV) to decrease transmission by blocking the acquisition of colonization has been attributed to herd immunity. We describe the role of mucosal immunoglobulin G (IgG) to capsular polysaccharide (CPS) in mediating protection from carriage, translating our findings from a murine model to humans. We used a flow cytometric assay to quantify antibody-mediated agglutination demonstrating that hyperimmune sera generated against an unencapsulated mutant was poorly agglutinating. Passive immunization with this antiserum was ineffective to block acquisition of colonization compared to agglutinating antisera raised against the encapsulated parent strain. In the human challenge model, samples were collected from PCV and control-vaccinated adults. In PCV-vaccinated subjects, IgG levels to CPS were increased in serum and nasal wash (NW). IgG to the inoculated strain CPS dropped in NW samples after inoculation suggesting its sequestration by colonizing pneumococci. In post-vaccination NW samples pneumococci were heavily agglutinated compared with pre-vaccination samples in subjects protected against carriage. Our results indicate that pneumococcal agglutination mediated by CPS-specific antibodies is a key mechanism of protection against acquisition of carriage. Capsule may be the only vaccine target that can elicit strong agglutinating antibody responses, leading to protection against carriage acquisition and generation of herd immunity.

[Correlation of the microbiota and intestinal mucosa in the pathophysiology and treatment of irritable bowel, irritable eye, and irritable mind syndrome]

Accumulating clinical evidence supports co-morbidity of irritable bowel, irritable eye and irritable mind symptoms. Furthermore, perturbation of the microbiota-host symbiosis (dysbiosis) is considered a common pathogenic mechanism connecting gastrointestinal, ocular and neuropsychiatric symptoms. Consequently, maintaining or restoring microbiota-host symbiosis represents a new approach to treat these symptoms or to prevent their relapses. Current treatment approach assigned a primary role to live probiotics alone or in combination with prebiotics to enhance colonization of beneficial bacteria and to strengthen the symbiosis. However, several papers showed major benefits of heat-killed probiotics as compared to their live counterparts on both intestinal and systemic symptoms. Recently, in addition to killing probiotics, in a proof of concept study lysates (fragments) of probiotics in combination with vitamins A, B, D and omega 3 fatty acids were successfully tested. These findings suggested a conceptual change in the approach addressed to both the microbiota and host as targets for intervention.

Irritable eye syndrome: neuroimmune mechanisms and benefits of selected nutrients

Previous studies showed comorbidity of some ocular, enteral, and affective symptoms comprising irritable eye syndrome. Aims of the present study were to learn more about the pathogenic mechanisms of this syndrome and to evaluate benefits of food supplements on these disorders. In in vitro assay, Lactobacillus acidophilus lysate inhibited interleukin (IL)-1β and tumor necrosis factor (TNF)-α generation of lipopolysaccharide (LPS)-stimulated macrophages in dose- and size-dependent manner. For a prospective, open-label phase I/II controlled clinical trial, 40 subjects affected by ocular dysesthesia and hyperesthesia and comorbid enteral and anxiety-depression symptoms were randomly assigned either into the treated group, which received a composition containing probiotic lysate, vitamins A, B, and D and omega 3 fatty acids, or into the control group, which received vitamins and omega 3 fatty acids. For reference, 20 age- and sex-matched healthy subjects were also selected. White blood count (WBC) and lymphocyte and monocyte counts, as well as IL-6 and TNF-α levels, were significantly above the reference levels in both treated and control groups. After 8 weeks, WBC and lymphocyte and monocyte counts, and cytokine levels significantly decreased, and ocular, enteral, and anxiety-depression symptoms significantly improved in the treated group as compared to the control group. This proof-of-concept study suggested that subclinical inflammation may be a common mechanism connecting ocular, enteral, and anxiety/depression symptoms, and supplements affecting dysbiosis may be a new approach to treating this syndrome.

Oral intake of Lactobacillus pentosus strain b240 accelerates salivary immunoglobulin A secretion in the elderly: A randomized, placebo-controlled, double-blind trial

Background

Immunoglobulin A (IgA) secretion in saliva decreases with age and may be the cause of increased vulnerability of the elderly to respiratory infections. The effect of oral intake of lactic acid bacteria on salivary secretory IgA (SIgA) in the elderly has not been reported. The objective of this study was to demonstrate the acceleration of salivary SIgA secretion by oral intake of Lactobacillus pentosus strain b240 (b240) in the elderly.

Results

A total of 80 healthy elderly individuals were randomly allocated to either an intervention (i.e., b240) or a control (i.e., placebo) group. The elderly individuals in the b240 group were given a sterile water beverage (125 mL) containing heat-killed b240 (4 × 10⁹ cells), while those in the placebo group were given only a sterile water beverage (125 mL); both groups received their respective beverages once daily for 12 weeks. Saliva was collected before initiation of the study and every 2 weeks thereafter. Saliva flow rate and SIgA concentration were determined, and the SIgA secretion rate was calculated. The mean salivary SIgA secretion rate in the b240 group steadily increased until week 4 (exhibiting a 20% elevation relative to that at week 0), and then remained stable until week 12. Changes in SIgA secretion rate over the intervention period were significantly greater in the b240 group than in the placebo group. The treatment groups exhibited no significant differences in adverse events.

Conclusions

Oral intake of L. pentosus strain b240 for 12 weeks significantly accelerated salivary SIgA secretion, thereby indicating its potential utility in the improvement of mucosal immunity and resistance against infection in the elderly.

Response of subgingival bacteria to smoking cessation

It has been demonstrated that smoking cessation alters the subgingival microbial profile; however, the response of individual bacteria within this ecosystem has not been well studied. The aim of this investigation, therefore, was to longitudinally examine the effect of smoking cessation on the prevalence and levels of selected subgingival bacteria using molecular approaches for bacterial identification and enumeration. Subgingival plaque was collected from 22 smokers at the baseline and 12 months following periodontal nonsurgical management and smoking cessation counseling. The prevalence and abundance of selected organisms were examined using nested PCR and multiplexed bead-based flow cytometry. Eleven subjects successfully quit smoking over 12 months (quitters), while 11 continued to smoke throughout (smokers). Smoking cessation led to a decrease in the prevalence of Porphyromonas endodontalis and Dialister pneumosintes at 12 months and in the levels of Parvimonas micra, Filifactor alocis, and Treponema denticola. Smoking cessation also led to an increase in the levels of Veillonella parvula. Following nonsurgical periodontal therapy and smoking cessation, the subgingival microbiome is recolonized by a greater number of health-associated species and there are a significantly lower prevalence and abundance of putative periodontal pathogens. The results indicate a critical role for smoking cessation counseling in periodontal therapy for smokers in order to effectively alter the subgingival microbiome.

An electron microscopy study of the diversity of Streptococcus sanguinis cells induced by lysozyme in vitro

Bacterial virulence could be altered by the antimicrobial agents of the host. Our aim was to identify the damage and survival of Streptococcus sanguinis induced by lysozymes in vitro and to analyse the potential of oral microorganisms to shirk host defences, which cause infective endocarditis. S. sanguinis ATCC 10556 received lysozyme at concentrations of 12.5, 25, 50 and 100 microg/ml. Cells were examined by electron microscopy. The survival was assessed by colony counting and construction of a growth curve. Challenged by lysozymes, cells mainly exhibited cell wall damage, which seemed to increase with increasing lysozyme concentration and longer incubation period in the presence of ions. Cells with little as well as apparent lesion were observed under the same treatment set, and anomalous stick and huge rotund bodies were occasionally observed. After the removal of the lysozyme, some damaged cells could be reverted to its original form with brain heart infusion (BHI), and their growth curve was similar to the control cells. After further incubation in BHI containing lysozyme, S. sanguinis cell damage stopped progressing, and their growth curve was also similar to the control cells. The results suggested that the S. sanguinis lesions caused by the lysozyme in the oral cavity may be nonhomogeneous and that some damaged cells could self-repair and survive. It also indicated that S. sanguinis with damaged cell walls may survive and be transmitted in the bloodstream.

Defect of cell wall construction may shield oral bacteria's survival in bloodstream and cause infective endocarditis

Infective endocarditis (IE) is a rare but life-threatening infection. Bacteremia with organisms known to cause IE occurs commonly in association with invasive dental origin. Despite daily oral activities as well as professional dental treatments inducing bacteremia and the dental bacteremia as a risk factor of IE, the details of dental bacteria in the pathogenesis of IE are far from elucidation to date. How do a few microorganisms survive host defenses or escape from antibiotic attacking to seed target organs and cause distant infections? Why are Gram-positive bacteria more frequently detected than Gram-negative bacteria in IE? Cell wall-deficient bacteria (CWDB) were traditionally defined as bacteria with altered morphology and consistent with damaged or absent cell wall structures identified by EM. A number of case reports and laboratory studies suggest that CWDB may be found in the peripheral blood of patients with IE, and may also be demonstrated in vegetations on the valves of patients with IE. CWDB, in vitro, are resistant to antibiotics that act on cell wall biosynthesis. Recent studies indicate that the Streptococcus mutans (S. mutans) strains, the major cariogenic bacterium, isolated from the infected valve were deficient in some wall-associated proteins which are main cariogenic virulence of S. mutans, and the deficient stains exhibited less susceptible to antibiotics that act on cell wall biosynthesis. Further, the cloned deficient mutans were less susceptible to phagocytosis by human polymorphonuclear leukocytes but to possess higher platelet aggregation properties than their parent strains. As outlined above, we hypothesize that defect of cell wall construction may shield oral bacteria's survival in bloodstream and cause IE.

Microbiology of odontogenic bacteremia: beyond endocarditis

SUMMARY

The human gingival niche is a unique microbial habitat. In this habitat, biofilm organisms exist in harmony, attached to either enamel or cemental surfaces of the tooth as well as to the crevicular epithelium, subjacent to a rich vascular plexus underneath. Due to this extraordinary anatomical juxtaposition, plaque biofilm bacteria have a ready portal of ingress into the systemic circulation in both health and disease. Yet the frequency, magnitude, and etiology of bacteremias due to oral origin and the consequent end organ infections are not clear and have not recently been evaluated. In this comprehensive review, we address the available literature on triggering events, incidence, and diversity of odontogenic bacteremias. The nature of the infective agents and end organ infections (other than endocarditis) is also described, with an emphasis on the challenge of establishing the link between odontogenic infections and related systemic, focal infections.

2D-QSAR and HQSAR of the inhibition of calcineurin-NFAT signaling by blocking protein-protein interaction with N-(4-oxo-1(4H)-naphthalenylidene)benzenesulfonamide analogues

The inhibition of calcineurin-NFAT signaling by blocking protein-protein interaction with N-(4-oxo-1(4H)-naphthalenylidene)benzenesulfonamide analogues was studied in order to obtain mechanistic information about the effects of structural modification and molecular design of immunomodulation agents. The study was carried out by quantitative structure-activity relationship (QSAR) analysis using 2D-QSAR and hologram QSAR (HQSAR) methods. The statistical results of the two models showed the best prediction and fitness (r2 > 0.900) for the inhibition activities. The inhibitory activities from the 2D-QSAR models were dependent upon the electronic affinity of electron acceptor and optimum dipole moment (DM opt = 4.491 Debye). In addition, the HQSAR model provided information about which structural distinctions could be significant contributors the inhibition.