Immunogenic characteristics of the outer membrane phosphoporin as a vaccine candidate against Klebsiella pneumoniae

Zeolitic Imidazole Framework-8 Nanoparticles as an Alternative to Freund's Adjuvant for Klebsiella pneumoniae Recombinant Protein Vaccine

Vaccination represents a promising approach to combat resistant Klebsiella pneumoniae (KP). However, there is currently no licensed vaccine in the veterinary field. Outer membrane proteins have been proven to possess good immunogenicity, but Freund's adjuvant, which is commonly used to administer protein vaccines, has limitations such as a complicated formulation process as well as a tendency to cause pain and inflammation in animals. Here, we prepared a nano-vaccine based on zeolitic imidazolate framework-8 (ZIF-8)-encapsulated outer membrane protein PhoE and evaluated its efficiency in enhancing humoral and cellular immune responses in BALB/c mice. ZIF-8 nanoparticles rapidly delivered the protein antigen into dendritic cells and successfully activated them. In addition, significantly higher IgG antibody titers, cytokine levels, and splenocyte proliferation indices were founded in mice subcutaneously immunized with PhoE@ZIF-8 than in those receiving free PhoE alone. In a BALB/c mouse model, PhoE@ZIF-8 elicited a strong immune response with improved prophylactic efficacy against KP that was similar to the Freund's adjuvant-formulated vaccine. Based on the superiority of this nano-vaccine with good biocompatibility, inexpensive preparation and higher efficiency of delivering antigen into cells, ZIF-8 can serve as a promising replacement for Freund's adjuvant in research, with a prospective usage for vaccines against bacterial pathogens in the veterinary field.

Antimicrobial resistance and vaccines in Enterobacteriaceae including extraintestinal pathogenic Escherichia coli and Klebsiella pneumoniae

Antimicrobial-resistant Enterobacteriaceae are increasingly a clinical challenge. In particular, extraintestinal pathogenic Escherichia coli and Klebsiella pneumoniae threaten public health. Vaccination presents a long-term strategy to reduce both drug-susceptible and resistant infections while maintaining current clinical therapies. The review aims to emphasize the need for vaccines targeting extraintestinal pathogenic E. coli and K. pneumoniae by providing an overview of disease burden, antimicrobial resistance, therapeutics, and vaccine development.

Sensitive and specific LAMP and multiplex qRT-PCR assays for detection of hypervirulent Klebsiella pneumoniae

Hypervirulent Klebsiella pneumoniae (hvKP) pose significant challenges to clinical anti-infective treatment and has emerged as a major threat to global public health. In this study, we employed the loop-mediated isothermal amplification (LAMP) assays with OTG (orange to green) visual dye and multiplex quantitative real-time PCR (qRT-PCR) assay to rapidly detect hvKP. We determined the detection limits of the LAMP methods for K. pneumoniae, iroB, and iucA genes and the qRT-PCR assay for iroB, iucA, rmpA and rmpA2. Additionally, we assessed the sensitivity and specificity (both over 95 %) of the LAMP and qRT-PCR methods. The LAMP and qRT-PCR methods established in this study have been proven to be simpler and more reliable than traditional PCR methods, making them an improved choice for laboratory diagnosis.

Refolding dynamics and immunoinformatic insights into Vibrio cholerae OmpA, OmpK, and OmpV for vaccine applications

OmpA, OmpK, and OmpV are crucial for the pathogenesis of Vibrio cholerae, functioning within the bacterium's outer membrane; they present significant potential as candidates for vaccine development. Due to their intrinsic β-sheet richness, these OMPs tend to form inclusion bodies whenever overexpression is attempted. To achieve a native-like structure, detergents can be utilized during the refolding of OMPs from inclusion bodies. The impact of different detergents is examined on the renaturation of these OMPs, specifically non-ionic and zwitterionic detergents. The findings provide valuable insights into detergent selection, with LDAO and DDM emerging as the best protein refolding agents, facilitating successful structural and functional studies of these OMPs. Furthermore, using immunoinformatics it is established that OmpA, OmpK, and OmpV carry B- and T-cell epitopes in their exposed extracellular regions. The presence of immunodominant regions makes it easier to employ these proteins as vaccine candidates as they are stable, non-allergenic, and likely to stimulate successful innate and active immune responses. Overall, with all three OMPs harboring numerous immunogenic epitopes, they can be employed in subunit vaccines against Vibrio spp. and contribute to the development of diagnostic tools for effective disease mitigation.

In silico and in vivo Investigations of the Immunoreactivity of Klebsiella pneumoniae OmpA Protein as a Vaccine Candidate

Background

The growing threat of antibiotic resistance and Klebsiella pneumoniae infection in healthcare settings highlights the urgent need for innovative solutions, such as vaccines, to address these challenges. This study sought to assess the potential of using K. pneumoniae outer membrane protein A (OmpA) as a vaccine candidate through both in silico and in vivo analyses.

Methods

The study examined the OmpA protein sequence for subcellular localization, antigenicity, allergenicity, similarity to the human proteome, physicochemical properties, B-cell epitopes, MHC binding sites, tertiary structure predictions, molecular docking, and immune response simulations. The ompA gene was cloned into the pET-28a (+) vector, expressed, purified and confirmed using Western blotting analysis. IgG levels in the serum of the immunized mice were measured using ELISA with dilutions ranging from 1:100 to 1:6400, targeting recombinant outer membrane protein A (rOmpA) and K. pneumoniae ATCC 13883. The sensitivity and specificity of the ELISA method were also assessed.

Results

The bioinformatics analysis identified rOmpA as a promising vaccine candidate. The immunized group demonstrated significant production of specific total IgG antibodies against rOmpA and K. pneumoniae ATCC1 13883, as compared to the control group (p < 0.0001). The titers of antibodies produced in response to bacterial exposure did not show any significant difference when compared to the anti-rOmpA antibodies (p > 0.05). The ELISA test sensitivity was 1:3200, and the antibodies in the serum could accurately recognize K. pneumoniae cells.

Conclusion

This study is a significant advancement in the development of a potential vaccine against K. pneumoniae that relies on OmpA. Nevertheless, additional experimental analyses are required.

A validated pangenome-scale metabolic model for the Klebsiella pneumoniae species complex

The Klebsiella pneumoniae species complex (KpSC) is a major source of nosocomial infections globally with high rates of resistance to antimicrobials. Consequently, there is growing interest in understanding virulence factors and their association with cellular metabolic processes for developing novel anti-KpSC therapeutics. Phenotypic assays have revealed metabolic diversity within the KpSC, but metabolism research has been neglected due to experiments being difficult and cost-intensive. Genome-scale metabolic models (GSMMs) represent a rapid and scalable in silico approach for exploring metabolic diversity, which compile genomic and biochemical data to reconstruct the metabolic network of an organism. Here we use a diverse collection of 507 KpSC isolates, including representatives of globally distributed clinically relevant lineages, to construct the most comprehensive KpSC pan-metabolic model to date, KpSC pan v2. Candidate metabolic reactions were identified using gene orthology to known metabolic genes, prior to manual curation via extensive literature and database searches. The final model comprised a total of 3550 reactions, 2403 genes and can simulate growth on 360 unique substrates. We used KpSC pan v2 as a reference to derive strain-specific GSMMs for all 507 KpSC isolates, and compared these to GSMMs generated using a prior KpSC pan-reference (KpSC pan v1) and two single-strain references. We show that KpSC pan v2 includes a greater proportion of accessory reactions (8.8 %) than KpSC pan v1 (2.5 %). GSMMs derived from KpSC pan v2 also generate more accurate growth predictions, with high median accuracies of 95.4 % (aerobic, n=37 isolates) and 78.8 % (anaerobic, n=36 isolates) for 124 matched carbon substrates. KpSC pan v2 is freely available at https://github.com/kelwyres/KpSC-pan-metabolic-model, representing a valuable resource for the scientific community, both as a source of curated metabolic information and as a reference to derive accurate strain-specific GSMMs. The latter can be used to investigate the relationship between KpSC metabolism and traits of interest, such as reservoirs, epidemiology, drug resistance or virulence, and ultimately to inform novel KpSC control strategies.

Klebsiella pneumoniae: adaptive immune landscapes and vaccine horizons

Klebsiella pneumoniae is among the most common antibiotic-resistant pathogens causing nosocomial infections. Additionally, it is a leading cause of neonatal sepsis and childhood mortality across the globe. Despite its clinical importance, we are only beginning to understand how the mammalian adaptive immune system responds to this pathogen. Further, many studies investigating potential K. pneumoniae vaccine candidates or alternative therapies have been launched in recent years. Here, we review the current state of knowledge on the adaptive immune response to K. pneumoniae infections and progress towards developing vaccines and other therapies to combat these infections.

In-silico identification of linear B-cell epitopes in specific proteins of Bartonella bacilliformis for the serological diagnosis of Carrion's disease

Carrion´s disease is caused by Bartonella bacilliformis, it is a Gram-negative pleomorphic bacterium. B. bacilliformis is transmitted by Lutzomyia verrucarum in endemic areas of the Peruvian Inter-Andean valleys. Additionally, the pathogenicity of B. bacilliformis involves an initial infection of erythrocytes and the further infection of endothelial cells, which mainly affects children and expectant women from extreme poverty rural areas. Therefore, the implementation of serological diagnostic methods and the development of candidate vaccines for the control of CD could be facilitated by the prediction of linear b-cell epitopes in specific proteins of B. bacilliformis by bioinformatics analysis. In this study, We used an in-silico analysis employing six web servers for the identification of epitopes in proteins of B. bacilliformis. The selection of B. bacilliformis-specific proteins and their analysis to identify epitopes allowed the selection of seven protein candidates that are expected to have high antigenic activity.

KbvR mutant of Klebsiella pneumoniae affects the synthesis of type 1 fimbriae and provides protection to mice as a live attenuated vaccine

Klebsiella pneumoniae is a leading cause of severe infections in humans and animals, and the emergence of multidrug-resistant strains highlights the need to develop effective vaccines for preventing such infections. Live attenuated vaccines are attractive vaccine candidates available in the veterinary field. We recently characterized that the K. pneumoniae kbvR (Klebsiella biofilm and virulence regulator) mutant was a highly attenuated strain in the mice model. In the present study, the characterization, safety, and protective efficacy of ΔkbvR strain as a live attenuated vaccine were evaluated. The synthesis and activity of type 1 fimbriae were increased in the ΔkbvR strain. All mice inoculated by the subcutaneous route with 105, 106, and 107 colony-forming units (CFU) doses of the ΔkbvR strain survived. Subcutaneous immunization with two doses of 105 or 107 CFU ΔkbvR elicited a robust humoral immune response, and provided protection against the following K. pneumoniae intraperitoneal infection. The antisera of mice immunized with 105 CFU dose improved the opsonophagocytic ability and complement-mediated lysis not only to the same serotype strain but also to the different serotype strain. The passive transfer of antisera from 105 CFU dose-immunized mice provided protection against K. pneumoniae infection. Overall, our results suggest the great potential of the ΔkbvR strain as a novel vaccine candidate against K. pneumoniae infections in herds or humans.