Epitope Mapping of Streptococcus agalactiae Elongation Factor Tu Protein Recognized by Human Sera

Development of a prototypic, field-usable diagnostic tool for the detection of gram-positive cocci-induced mastitis in cattle

BACKGROUND

Bovine mastitis is one of the most widespread diseases affecting cattle, leading to significant losses for the dairy industry. Currently, the so-called gold standard in mastitis diagnosis involves determining the somatic cell count (SCC). Apart from a number of advantages, this method has one serious flaw: It does not identify the etiological factor causing a particular infection, making it impossible to introduce targeted antimicrobial therapy. This can contribute to multidrug-resistance in bacterial species. The diagnostic market lacks a test that has the advantages of SCC and also recognizes the species of pathogen causing the inflammation. Therefore, the aim of our study was to develop a lateral flow immunoassay (LFIA) based on elongation factor Tu for identifying most prevalent Gram-positive cocci responsible for causing mastitis including Streptococcus uberis, Streptococcus agalactiae and Staphylococcus aureus.

RESULTS

As a result, we showed that the assay for S. uberis detection demonstrated a specificity of 89.02%, a sensitivity of 43.59%, and an accuracy of 80.3%. In turn, the second variant - assay for Gram-positive cocci reached a specificity of 95.59%, a sensitivity of 43.28%, and an accuracy of 78.33%.

CONCLUSIONS

Our study shows that EF-Tu is a promising target for LFIA and we have delivered evidence that further evaluation could improve test parameters and fill the gap in the mastitis diagnostics market.

Immunorecognition of Streptococcus mutans secreted proteins protects against caries by limiting tooth adhesion

INTRODUCTION

Childhood caries, a prevalent chronic disease, affects 60-90 % of children in industrialized regions, leading to lesions in both primary and permanent teeth. This condition precipitates hospital admissions, emergency room visits, elevated treatment costs, and missed school days, thereby impeding the child's academic engagement and increasing the likelihood of caries into adulthood. Despite multiple identified risk factors, significant interpersonal variability remains unexplained. The immune system generates a unique antibody repertoire, essential for maintaining a balanced and healthy oral microbiome. Streptococcus mutans is a primary contributor to the development of caries.

METHODS

Employing mass spectrometry, we investigated the S. mutans proteins targeted by antibodies in children both with and without caries, delineating a fundamental suite of proteins discernible by the immune systems of a majority of individuals. Notably, this suite was enriched with proteins pivotal for bacterial adhesion. To ascertain the physiological implications of these discoveries, we evaluated the efficacy of saliva in thwarting S. mutans adherence to dental surfaces.

RESULTS

Antibodies in most children recognized a core set of ten S. mutans proteins, with additional proteins identified in some individuals. There was no significant difference in the proteins identified by children with or without caries, but there was variation in antibody binding intensity to some proteins. Functionally, saliva from caries-free individuals, but not children with caries, was found to hinder the binding of S. mutans to teeth. These findings delineate the S. mutans proteome targeted by the immune system and suggest that the inhibition of bacterial adherence to teeth is a primary mechanism employed by the immune system to maintain oral balance and prevent caries formation.

CONCLUSIONS

These findings enhance our knowledge of the immune system's function in oral health maintenance and caries prevention, shedding light on how immunoglobulins interact with S. mutans proteins.

CLINICAL SIGNIFICANCE

Targeting S. mutans proteins implicated in bacterial adhesion could be a promising strategy for preventing childhood caries.

Combinations but Not a Single PlpE Epitope Induces Host Protective Immunity against Pasteurella multocida

Pasteurella multocida is the causative agent of a wide range of diseases (pasteurellosis) and a zoonotic pathogen in humans. Recombinant subunit vaccines are hot spots in recent pasteurellosis vaccine development. A chimeric vaccine is also constructed for rabbit hemorrhagic disease virus (RHDV) protective antigen VP60 chimeric with fragments of Pasteurella multocida protective antigen PlpE. The protective efficacy of the chimeric vaccine against P. multocida is not as high as that of PlpE, and the reason is not well known. In this study, we analyzed the linear B-cell epitopes of PlpE and then assessed the protective efficacy of these epitopes and their combinations. It was found that the immunodominant region of PlpE was mainly located in the region between the 21st to the 185th amino acids from the N terminus. Overlapping peptide scanning results demonstrated that this region contained six nonoverlapping epitopes, and epitope E was the predominant epitope. Chimeric protein antigens were constructed of single nonoverlapping PlpE epitopes or their combinations chimeric with the RHDV VP60 P domain. Immunization with recombinant antigen chimeric with a single PlpE epitope exhibited poor immunoprotection, whereas immunization with recombinant antigen chimeric with PlpE epitope combinations (epitopes A and E; epitopes C and E; epitopes A, C, and E; and epitopes B, D, and F) exhibited significant immunoprotection. In a word, P. multocida protective antigen PlpE contained six nonoverlapping linear B-cell epitopes, and combinations but not a single epitope induced host protective immunity. Our work will give help for future chimeric vaccine design.

Detection of immunoreactive proteins of Escherichia coli, Streptococcus uberis, and Streptococcus agalactiae isolated from cows with diagnosed mastitis

Introduction

Mastitis is a widespread mammary gland disease of dairy cows that causes severe economic losses to dairy farms. Mastitis can be caused by bacteria, fungi, and algae. The most common species isolated from infected milk are, among others, Streptococcus spp., and Escherichia coli. The aim of our study was protein detection based on both in silico and in vitro methods, which allowed the identification of immunoreactive proteins representative of the following species: Streptococcus uberis, Streptococcus agalactiae, and Escherichia coli.

Methods

The study group included 22 milk samples and 13 serum samples obtained from cows with diagnosed mastitis, whereas the control group constituted 12 milk samples and 12 serum samples isolated from healthy animals. Detection of immunoreactive proteins was done by immunoblotting, while amino acid sequences from investigated proteins were determined by MALDI-TOF. Then, bioinformatic analyses were performed on detected species specific proteins in order to investigate their immunoreactivity.

Results

As a result, we identified 13 proteins: 3 (molybdenum cofactor biosynthesis protein B, aldehyde reductase YahK, outer membrane protein A) for E. coli, 4 (elongation factor Tu, tRNA uridine 5-carboxymethylaminomethyl modification enzyme MnmG, GTPase Obg, glyceraldehyde-3-phosphate dehydrogenase) for S. uberis, and 6 (aspartate carbamoyltransferase, elongation factor Tu, 60 kDa chaperonin, elongation factor G, galactose-6-phosphate isomerase subunit LacA, adenosine deaminase) for S. agalactiae, which demonstrated immunoreactivity to antibodies present in serum from cows with diagnosed mastitis.

Discussion

Due to the confirmed immunoreactivity, specificity and localization in the bacterial cell, these proteins can be considered considered potential targets in innovative rapid immunodiagnostic assays for bovine mastitis, however due to the limited number of examined samples, further examination is needed.

Molecular Characteristic, Antibiotic Resistance, and Detection of Highly Immunoreactive Proteins of Group B Streptococcus Strains Isolated From Urinary Tract Infections in Polish Adults

Group B streptococcus (GBS) is one of the uropathogens that causes urinary tract infections (UTIs). The aims of this article were molecular characterization, an analysis of antimicrobial susceptibility profiles, adherence to bladder endothelial cells, and the detection of immunoreactive proteins of 94 clinical strains of GBS isolated from adult Polish patients with UTI. Antibiotic susceptibilities were determined by disk diffusion. Serotyping and Alp family genes detection were studied using multiplex PCR. Genetic profiles were determined by pulsed-field gel electrophoresis. The adherence ability of the studied strains was estimated by incubation on human bladder microvascular endothelial cell line. Immunoreactive proteins were studied by immunoblotting. Antibiotic susceptibility investigation revealed that 22% of GBS strains were resistant to erythromycin, whereas 18% demonstrated resistance to clindamycin. cMLS_B was present in 76% of the resistant strains, M phenotype was detected in 14%, whereas iMLS_B was present for 10%. The most common serotype was serotype III (31%), followed by serotype V (27%), and serotype Ia (17%). The genes that dominated among other Alp genes were: epsilon (29%), alp2 (27%), and rib (23%). The most common co-occurring serotypes and Alp genes were: Ia and epsilon, III and rib, III and alp2, V and alp2, and V and alp3 (p < 0.001). The PFGE method showed high clonality for serotype V and cMLS_B (p < 001). The PFGE method showed high clonality for serotype V. Furthermore, this serotype was significantly associated with the cMLS_B phenotype (p < 0.001). The most common immunoreactive proteins demonstrated masses of 50 kDa and 45–47 kDa. Although examined GBS isolates showed high genetic diversity, immunoreactive proteins were common for most of the studied GBS isolates, which may indicate their conservation, and allows to consider them as potential immunodiagnostic markers. Although the examined GBS isolates showed high genetic diversity, immunoreactive proteins were shared by most of the studied GBS isolates. It may indicate their conservation, thus allowing to consider them as potential immunodiagnostic markers.

Immunogenic Proteins of Group B Streptococcus-Potential Antigens in Immunodiagnostic Assay for GBS Detection

Streptococcus agalactiae (Group B Streptococcus, GBS) is an opportunistic pathogen, which asymptomatically colonizes the gastrointestinal and genitourinary tract of up to one third of healthy adults. Nevertheless, GBS carriage in pregnant women may lead to several health issues in newborns causing life threatening infection, such as sepsis, pneumonia or meningitis. Recommended GBS screening in pregnant women significantly reduced morbidity and mortality in infants. Nevertheless, intrapartum antibiotic prophylaxis, recommended following the detection of carriage or in case of lack of a carriage test result for pregnant women who demonstrate certain risk factors, led to the expansion of the adverse phenomenon of bacterial resistance to antibiotics. In our paper, we reviewed some immunogenic GBS proteins, i.e., Alp family proteins, β protein, Lmb, Sip, BibA, FsbA, ScpB, enolase, elongation factor Tu, IMPDH, and GroEL, which possess features characteristic of good candidates for immunodiagnostic assays for GBS carriage detection, such as immunoreactivity and specificity. We assume that they can be used as an alternative diagnostic method to the presently recommended bacteriological cultivation and MALDI.

Computational tools for modern vaccine development

Vaccines play an essential role in controlling the rates of fatality and morbidity. Vaccines not only arrest the beginning of different diseases but also assign a gateway for its elimination and reduce toxicity. This review gives an overview of the possible uses of computational tools for vaccine design. Moreover, we have described the initiatives of utilizing the diverse computational resources by exploring the immunological databases for developing epitope-based vaccines, peptide-based drugs, and other resources of immunotherapeutics. Finally, the applications of multi-graft and multivalent scaffolding, codon optimization and antibodyomics tools in identifying and designing in silico vaccine candidates are described.

Mapping Epitopes of a Novel Peptidoglycan Cross-Linking Enzyme Cwp22 Recognized by Human Sera Obtained from Patients with Clostridioides difficile Infection and Cord Blood

Clostridioides difficile (CD) cause a severe diarrhea which can lead to pseudomembranous colitis and even patient death. CD infection (CDI) is connected mainly with changes in intestinal microbiota as a consequence of antibiotic treatment. The growing resistance to antibiotics, justifies the search for new methods of combating CD. Despite of ongoing research on the immunity against the pathogen, there is still lack of any reliable vaccine. Most recently, Cwp22, that is a cross-linking enzyme involved in the production of CD peptidoglycan, seems to be a promising target to prevent CDI in high-risk patients. In this paper, the Cwp22 protein polypeptide-specific epitopes were mapped in silico and using PEPSCAN procedure. They were recognized not only by antibodies from CDI patients’ but also by umbilical cord blood sera. We identified three epitopes ⁵⁴EFRVAT⁵⁹, ²⁰¹KVNGKM²⁰⁶ and ²⁶⁸WQEKNGKKYY²⁷⁷ of Cwp22 protein. Since Cwp22 protein has key functionality and the described above epitopes are also recognized by umbilical cord blood serum, we postulate that they could have important protective properties. In this paper, we propose Cwp22 protein as a good antigen candidate for CDI preventive vaccine. Our results open the possibility to use ⁵⁴EFRVAT⁵⁹, ²⁰¹KVNGKM²⁰⁶ and ²⁶⁸WQEKNGKKYY²⁷⁷, epitopes as suitable anti-CD vaccine antigens.

Anti-EF-Tu IgG titers increase with age and may contribute to protection against the respiratory pathogen Haemophilus influenzae

Non‐typeable Haemophilus influenzae (NTHi) is a pathogen that commonly colonizes the nasopharynx of preschool children, causing opportunistic infections including acute otitis media (AOM). Patients suffering from chronic obstructive pulmonary disease (COPD) are persistently colonized with NTHi and occasionally suffer from exacerbations by the bacterium leading to increased morbidity. Elongation‐factor thermo unstable (EF‐Tu), a protein critical for bacterial protein synthesis, has been found to moonlight on the surface of several bacteria. Here, we show that antibodies against NTHi EF‐Tu were present in children already at 18 months of age, and that the IgG antibody titers increased with age. Children harboring NTHi in the nasopharynx also displayed significantly higher IgG concentrations. Interestingly, children suffering from AOM had significantly higher anti‐EF‐Tu IgG levels when NTHi was the causative agent. Human sera recognized mainly the central and C‐terminal part of the EF‐Tu molecule and peptide‐based epitope mapping confirmed similar binding patterns for sera from humans and immunized mice. Immunization of BALB/c and otitis‐prone Junbo (C3H/HeH) mice promoted lower infection rates in the nasopharynx and middle ear, respectively. In conclusion, our results suggest that IgG directed against NTHi EF‐Tu may play an important role in the host immune response against NTHi.

EF-Tu From Non-typeable Haemophilus influenzae Is an Immunogenic Surface-Exposed Protein Targeted by Bactericidal Antibodies

Non-typeable Haemophilus influenzae (NTHi), a commensal organism in pre-school children, is an opportunistic pathogen causing respiratory tract infections including acute otitis media. Adults suffering from chronic obstructive pulmonary disease (COPD) are persistently colonized by NTHi. Previous research has suggested that, in some bacterial species, the intracellular elongation factor thermo-unstable (EF-Tu) can moonlight as a surface protein upon host encounter. The aim of this study was to determine whether EF-Tu localizes to the surface of H. influenzae, and if such surface-associated EF-Tu is a target for bactericidal antibodies. Using flow cytometry, transmission immunoelectron microscopy, and epitope mapping, we demonstrated that EF-Tu is exposed at the surface of NTHi, and identified immunodominant epitopes of this protein. Rabbits immunized with whole-cell NTHi produced significantly more immunoglobulin G (IgG) directed against EF-Tu than against the NTHi outer membrane proteins D and F as revealed by enzyme-linked immunosorbent assays. Chemical cleavage of NTHi EF-Tu by cyanogen bromide (CNBr) followed by immunoblotting showed that the immunodominant epitopes were located within the central and C-terminal regions of the protein. Peptide epitope mapping by dot blot analysis further revealed four different immunodominant peptide sequences; EF-Tu⁴¹⁻⁶⁵, EF-Tu^161−185, EF-Tu^221−245, and EF-Tu^281−305. These epitopes were confirmed to be surface-exposed and accessible by peptide-specific antibodies in flow cytometry. We also analyzed whether antibodies raised against NTHi EF-Tu cross-react with other respiratory tract pathogens. Anti-EF-Tu IgG significantly detected EF-Tu on unencapsulated bacteria, including the Gram-negative H. parainfluenzae, H. haemolyticus, Moraxella catarrhalis and various Gram-positive Streptococci of the oral microbiome. In contrast, considerably less EF-Tu was observed at the surface of encapsulated bacteria including H. influenzae serotype b (Hib) and Streptococcus pneumoniae (e.g., serotype 3 and 4). Removal of the capsule, as exemplified by Hib RM804, resulted in increased EF-Tu surface density. Finally, anti-NTHi EF-Tu IgG promoted complement-dependent bacterial killing of NTHi and other unencapsulated Gram-negative bacteria as well as opsonophagocytosis of Gram-positive bacteria. In conclusion, our data demonstrate that NTHi EF-Tu is surface-exposed and recognized by antibodies mediating host innate immunity against NTHi in addition to other unencapsulated respiratory tract bacteria.

Epitopes of Immunoreactive Proteins of Streptococcus Agalactiae: Enolase, Inosine 5'-Monophosphate Dehydrogenase and Molecular Chaperone GroEL

Three Streptococcus agalactiae (group B streptococci, GBS) immunoreactive proteins: enolase (47.4 kDa), inosine 5'-monophosphate dehydrogenase (IMPDH) (53 kDa) and molecular chaperone GroEL (57 kDa) were subjected to investigation. Enolase protein was described in our previous paper, whereas IMPDH and GroEL were presented for the first time. The aim of our paper was to provide mapping of specific epitopes, highly reactive with umbilical cord blood serum. Bioinformatic analyses allowed to select 32 most likely epitopes for enolase, 36 peptides for IMPDH and 41 immunoreactive peptides for molecular chaperone GroEL, which were synthesized by PEPSCAN. Ten peptides: two in enolase, one in IMPDH and seven in molecular chaperone GroEL have been identified as potentially highly selective epitopes that can be used as markers in rapid immunological diagnostic tests or constitute a component of an innovative vaccine against GBS infections.