How prevalent are lactoferrin receptors in Gram-negative bacteria?

Surface receptors in Gram-negative bacteria that bind and extract iron from the host glycoproteins transferrin (Tf) or lactoferrin (Lf) was discovered 35 years ago in pathogenic species and subsequently was discovered in other pathogens of humans and food production animals. These bacterial species reside exclusively on the mucosal surfaces of the respiratory or genitourinary tract of their mammalian host and rely on their host specific Tf and Lf receptors to acquire iron for survival. Since the specificity of the bacterial Tf receptors was shown to be due to selective pressures on the host Tf, their presence in bacteria that reside in both mammals and birds indicates that they arose over 320 million years ago.

Rational selection of TbpB variants elucidates a bivalent vaccine formulation with broad spectrum coverage against .

is the causative agent of gonorrhea, an on-going public health problem due in part to the lack of success with efforts to develop an efficacious vaccine to prevent this sexually transmitted infection. An attractive candidate vaccine antigen because of its essential function and surface exposure, the gonococcal transferrin binding protein B (TbpB) exhibits high levels of antigenic variability which poses a significant obstacle in evoking a broadly protective vaccine composition. Here, we utilize phylogenetic information to rationally select TbpB variants for inclusion into a potential gonococcal vaccine and identify two TbpB variants that when formulated together elicit a highly cross-reactive antibody response in both rabbits and mice against a diverse panel of TbpB variants and clinically relevant gonococcal strains.

Human transferrin and lactoferrin cooperatively support colonization in the murine nasopharynx.

is a human-restricted bacteria that is a normal nasopharyngeal resident, yet it can also disseminate, causing invasive meningococcal disease. Meningococci are highly adapted to life in humans, with human-specific virulence factors contributing to bacterial adhesion, nutrient acquisition and immune evasion. While these factors have been explored in isolation, their relative contribution during infection has not been considered due to their absence in small animal models and their expression by different human cell types not readily combined in either or systems.

A secreted bacterial protein protects bacteria from cationic antimicrobial peptides by entrapment in phase-separated droplets.

Mammalian hosts combat bacterial infections through the production of defensive cationic antimicrobial peptides (CAPs). These immune factors are capable of directly killing bacterial invaders; however, many pathogens have evolved resistance evasion mechanisms such as cell surface modification, CAP sequestration, degradation, or efflux. We have discovered that several pathogenic and commensal proteobacteria, including the urgent human threat , secrete a protein (lactoferrin-binding protein B, LbpB) that contains a low-complexity anionic domain capable of inhibiting the antimicrobial activity of host CAPs.

Use of Epivolve phage display to generate a monoclonal antibody with opsonic activity directed against a subdominant epitope on extracellular loop 4 of BamA (TP0326).

Introduction: Syphilis, a sexually transmitted infection caused by the spirochete (), is resurging globally. 's repertoire of outer membrane proteins (OMPs) includes BamA (β-barrel assembly machinery subunit A/TP0326), a bipartite protein consisting of a 16-stranded β-barrel with nine extracellular loops (ECLs) and five periplasmic POTRA (polypeptide transport-associated) domains. BamA ECL4 antisera promotes internalization of by rabbit peritoneal macrophages.

Reverse vaccinology-based identification of a novel surface lipoprotein that is an effective vaccine antigen against bovine infections caused by Pasteurella multocida.

Pasteurella multocida can infect a multitude of wild and domesticated animals, with infections in cattle resulting in hemorrhagic septicemia (HS) or contributing to bovine respiratory disease (BRD) complex. Current cattle vaccines against P. multocida consist of inactivated bacteria, which only offer limited and serogroup specific protection.

Insights from targeting transferrin receptors to develop vaccines for pathogens of humans and food production animals.

While developing vaccines targeting surface transferrin receptor proteins in Gram-negative pathogens of humans and food production animals, the common features derived from their evolutionary origins has provided us with insights on how improvements could be implemented in the various stages of research and vaccine development. These pathogens are adapted to live exclusively on the mucosal surfaces of the upper respiratory or genitourinary tract of their host and rely on their receptors to acquire iron from transferrin for survival, indicating that there likely are common mechanisms for delivering transferrin to the mucosal surfaces that should be explored. The modern-day receptors are derived from those present in bacteria that lived over 320 million years ago.

TbpB-based vaccine is safe in pregnant sows and induces high titers of maternal derived antibodies that reduce Glaesserella parasuis colonization in piglets.

Glässer's disease is one of the main diseases affecting young piglets, particularly during the nursery phase, that can significantly impact pork production. Vaccination of sows has the potential to prevent Glaesserella parasuis infection during the first weeks of life that is to a substantial degree due to the transfer of maternal derived antibodies (MDA) in colostrum. In this study we compare the antibody response to two vaccines administered to pregnant sows.

Structural and functional insights into iron acquisition from lactoferrin and transferrin in Gram-negative bacterial pathogens.

Iron is an essential element for various lifeforms but is largely insoluble due to the oxygenation of Earth's atmosphere and oceans during the Proterozoic era. Metazoans evolved iron transport glycoproteins, like transferrin (Tf) and lactoferrin (Lf), to keep iron in a non-toxic, usable form, while maintaining a low free iron concentration in the body that is unable to sustain bacterial growth. To survive on the mucosal surfaces of the human respiratory tract where it exclusively resides, the Gram-negative bacterial pathogen Moraxella catarrhalis utilizes surface receptors for acquiring iron directly from human Tf and Lf.

Hybrid antigens expressing surface loops of BauA from are capable of inducing protection against infection.

is a human bacterial pathogen of increasing concern in clinical settings due to the emergence of antibiotic resistant strains and the lack of effective therapeutics. Researchers have been exploring new treatment options such as novel drug candidates and vaccines to prevent severe infections and mortality. Bacterial surface antigens that are essential to for acquiring micronutrients (e.

TbpB-Based Vaccine Can Protect Pigs against Glässer's Disease Triggered by SV7 Expressing TbpB Cluster I.

is the etiological agent of Glässer's disease (GD), one of the most important diseases afflicting pigs in the nursery phase. We analyzed the genetic and immunological properties of the TbpB protein naturally expressed by 27 different clinical isolates of that were typed as serovar 7 and isolated from pigs suffering from GD. All the strains were classified as virulent by LS-PCR.

Immunogenicity of loop 3 of Omp34 from A. Baumannii in loopless C-lobe of TbpB of N. meningitidis.

Acinetobacter baumannii is a common causative agent of nosocomial infections, with a mortality rate of 43% in infected patients. Due to the emergence of multidrug-resistant (MDR) strains, vaccine development has become necessary. Since the 34 kDa outer membrane protein Omp34 has been identified as a potential vaccine target, we implemented a hybrid antigen approach to target its extracellular loops.

BauA and Omp34 surface loops trigger protective antibodies against Acinetobacter baumannii in a murine sepsis model.

The complexity of treating Acinetobacter baumannii infections with the newly developed resistant strains has led researchers to confront this pathogen by developing vaccines. In this study, we used two important virulence factors of A. baumannii to elicit immunity against the A.

Targeting bacterial transferrin and lactoferrin receptors for vaccines.

A substantial disease burden in vertebrates is due to Gram-negative bacteria that exclusively inhabit the upper respiratory or genitourinary tracts of their hosts and rely on directly acquiring iron from the host iron-binding glycoproteins through surface receptor proteins. The receptors enable these bacteria to proliferate independently from their neighbors on the mucosal surface and during invasive infection of the host. The diversity in these receptors evolved over millions of years of evolution, which thus bodes well for long-lasting vaccine coverage.

Design and Production of Hybrid Antigens for Targeting Integral Outer Membrane Proteins in Gram-Negative Bacteria.

Metal ion transporters in the outer membrane of gram-negative bacteria that are responsible for acquiring iron and zinc are attractive vaccine targets due to their essential function. The core function is mediated by an integral outer membrane TonB-dependent transporter (TBDT) that mediates the transport of the metal ion across the outer membrane. Some TBDTs also have a surface lipoprotein (SLP) that assists in the efficient capture of the metal ion-containing host protein from which the metal ion is extracted.

The Role of the CopB Protein in Facilitating Iron Acquisition From Human Transferrin and Lactoferrin.

is a Gram-negative bacterium that is responsible for a substantial proportion of upper respiratory infections in children and lower respiratory infections in the elderly. resides exclusively on the mucosal surfaces of the upper respiratory tract of humans and is capable of directly acquiring iron for growth from the host glycoproteins human transferrin (hTf) and human lactoferrin (hLf). The iron-bound form of these glycoproteins is initially captured by the surface lipoproteins Tf or Lf binding protein B (TbpB or LbpB) and delivered to the integral outer membrane TonB-dependent transport (TBDT) proteins, Tf binding protein A (TbpA) or Lf binding protein A (LbpA).

Development of a non-biased, high-throughput ELISA for the rapid evaluation of immunogenicity and cross-reactivity.

Traditional ELISA-based protein analysis has been predicated on the assumption that proteins bind randomly to the solid surface of the ELISA plate polymer (polystyrene or polyvinyl chloride). Random adherence to the plate ensures equal access to all faces of the protein, an important consideration when evaluating immunogenicity of polyclonal serum samples as well as when examining the cross-reactivity of immune serum against different antigenic variants of a protein. In this study we demonstrate that the soluble form of the surface lipoprotein transferrin binding protein B (TbpB) from three different bacterial pathogens (Neisseria meningitidis, Actinobacillus pleuropneumoniae, and Mannheimia haemolytica) bind the ELISA plate in a manner that consistently obscures the transferrin binding face of the proteins' N-lobe.

Lactoferrin receptors in Gram-negative bacteria: an evolutionary perspective.

In this short review, we outline the major events that led to the development of iron acquisition systems in Gram-negative bacteria and mammals since the beginning of life on earth. Naturally, the interaction between these organisms led to the development of a wonderfully complex set of protein systems used for competition over a once prevalent (but no longer) biocatalytic cofactor. These events led to the appearance of the lactoferrin gene, which has since been exploited into adopting countless new functions, including the provision of highly bactericidal degradation products.

Proof of Concept for Prevention of Natural Colonization by Oral Needle-Free Administration of a Microparticle Vaccine.

There has been substantial interest in the development of needle-free vaccine administration that has led to a variety of approaches for delivery through the skin for induction of a systemic immune response. The mucosal administration of vaccines has inherently been needle-free, but the simple application of vaccines on the mucosal surface by itself does not lead to mucosal immunity. Since many important bacterial infections develop after initial colonization of the upper respiratory tract of the host, prevention of colonization could not only prevent infection but also eliminate the reservoir of pathogens that reside exclusively in that ecologic niche.

New Pathological Lesions Developed in Pigs by a "Non-virulent" Strain of .

is a Gram-negative bacterium that causes Glässer's disease, a common pathology found in young pigs characterized by polyarthritis, polyserositis, and meningitis. The bacterium has 15 known serovars that have been classified by virulence. Serovars 1, 4, 5, and 12 are considered highly virulent and used in most studies.

Hybrid Antigens Expressing Surface Loops of ZnuD From Is Capable of Inducing Protection Against Infection.

is an important human pathogen causing substantial mortality in hospitalized patients for which treatment with antibiotics has become problematic due to growing antibiotic resistance. In an attempt to develop alternative strategies for dealing with these serious infections surface antigens are being considered as targets for vaccines or immunotherapy. The surface receptor proteins required for zinc acquisition in Gram-negative bacterial pathogens have been proposed as vaccine targets due to their crucial role for growth in the human host.

Molecular serotyping of clinical strains of brings new insights regarding Glässer's disease outbreaks in Brazil.

Glässer's disease (GD) is an important infectious disease of swine caused by . Vaccination with inactivated whole cell vaccines is the major approach for prevention of infection worldwide, but the immunity induced is predominantly against the specific polysaccharide capsule. As a consequence, the available vaccines may not induce adequate protection against the field strains, when the capsules present in the vaccine strains are different from those in strains isolated from the farms.

Utility of Hybrid Transferrin Binding Protein Antigens for Protection Against Pathogenic Neisseria Species.

The surface transferrin receptor proteins from have been recognized as ideal vaccine targets due to their critical role in survival in the human male genitourinary tract. Recombinant forms of the surface lipoprotein component of the receptor, transferrin binding protein B (TbpB), can be readily produced at high levels in the cytoplasm and is suitable for commercial vaccine production. In contrast, the integral outer membrane protein, transferrin binding protein A (TbpA), is produced at relatively low levels in the outer membrane and requires detergents for solubilization and stabilization, processes not favorable for commercial applications.

Photo-Cross-Linking Mass Spectrometry and Integrative Modeling Enables Rapid Screening of Antigen Interactions Involving Bacterial Transferrin Receptors.

Structure-based approaches to the delineation of immunogens for vaccine development have a throughput requirement that is difficult to meet in practice with conventional methods of structure determination. Here we present a strategy for rapid and accurate structure generation in support of antigen engineering programs. The approach is developed around the modeling of interactions between host transferrin (Tf) and the bacterial vaccine target transferrin binding protein B (TbpB) from Gram-negative pathogens such as Neisseria meningitidis.