Determination of immunodominant scaffolds of Com1 and OmpH antigens of Coxiella burnetii

Overview of the Q fever vaccine development: current status and future prospects

Coxiella burnetii, the causative agent of Q fever, is responsible for a globally significant zoonotic disease, characterized by flu-like symptoms. The primary reservoirs of C. burnetii are ruminant livestock, particularly goats, sheep, and cattle, which shed the bacterium through birth products, such as the placenta, amniotic fluid, and other secretions. Human infections typically occur via the inhalation of contaminated aerosols during direct or indirect contact with infected animals or their birthing materials. Consequently, individuals living in or working near livestock environments are at elevated risk, making Q fever both a location- and occupation-related disease. Owing to its remarkable environmental resilience and extremely low infectious dose, C. burnetii is classified as a Category B bioterrorism agent by the U.S. Centers for Disease Control and Prevention (CDC). These characteristics significantly complicate efforts to eradicate the bacterium and position vaccination as a key strategy for preventing human transmission. Although whole-cell vaccines (WCVs) are currently licensed for use in Australia, their widespread implementation has been hindered by their strong reactogenic responses in individuals with prior exposure to C. burnetii. This review provides an overview of past and current efforts to develop non-reactogenic C. burnetii vaccines and discusses possible approaches to enhance the efficiency and safety of these vaccines.

Whole proteome screening to develop a potent epitope-based vaccine against Coxiella burnetii: a reverse vaccinology approach

Coxiellosis is known as a threat to human health. This study aimed to develop an epitope-based vaccine against coxiellosis using a whole proteome investigation. In this case, the whole proteome of Coxiella burnetii was collected from the database, then different assessments were performed to select immunogenic proteins. The selected proteins were used for epitopes prediction. The epitope-based vaccine was made using the best-selected epitopes and HBHA protein. The physical and chemical features, as well as secondary and tertiary structures of the developed vaccine were analyzed. The interaction between the developed vaccine and TLR4/MD2 receptor was examined using molecular docking and molecular dynamic simulation. Finally, in silico cloning, codon optimization, and immune response simulation for the developed vaccine were performed. The findings supported a stable, hydrophilic, antigenic and non-allergenic vaccine with a molecular weight equal to 59.261 kDa and 542 amino acid residues in length. The findings showed that the developed vaccine not only could dock to TRL4/MD2 receptor with an affinity of -20.9 kcal/mol and 15 hydrogen bonds, but also the protein-protein complex was stable during molecular dynamic simulation with the binding free energy of -57.9 ± 6.9 kcal/mol. Furthermore, the optimized sequence of the developed vaccine with a CAI value of 0.97, could be cloned into the pET-21a (+) vector. Finally, The results confirmed that the developed vaccine could strongly trigger primary and secondary immune responses. Evidently, the developed vaccine can be an interesting candidate to apply.

Characterization of Three New Outer Membrane Adhesion Proteins in Fusobacterium necrophorum

Fusobacterium necrophorum, an anaerobic Gram-negative pathogen, causes necrotic cattle infections, impacting livestock health and the US feedlot industry. Antibiotic administration is the mainstay for treating F. necrophorum infections, although resistance hampers their effectiveness. Vaccination, especially targeting outer membrane proteins (OMPs) due to their antigenic properties and host specificity, offers an alternative to antibiotics. This study identified high-binding-affinity adhesion proteins from F. necrophorum using binding and pull-down assays with bovine adrenal gland endothelial cells (EJG). Four OMP candidates (17.5 kDa/OmpH, 22.7 kDa/OmpA, 66.3 kDa/cell surface protein (CSP), and a previously characterized 43 kDa OMP) were expressed as recombinant proteins and purified. Rabbit polyclonal antibodies to recombinant OMPs were generated, and their ability to inhibit bacterial binding in vitro was assessed. The results show that treatment with individual polyclonal antibodies against 43 kDa significantly inhibited bacterial adhesion, while other antibodies were less potent. However, combinations of two or more antibodies showed a more prominent inhibitory effect on host-cell adhesion. Thus, our findings suggest that the identified OMPs are involved in fusobacterial attachment to host cells and may have the potential to be leveraged in combination for vaccine development. Future in vivo studies are needed to validate their roles and test the feasibility of an OMP-based subunit vaccine against fusobacterial infections.

Multivalent vaccines demonstrate immunogenicity and protect against Coxiella burnetii aerosol challenge

Vaccines are among the most cost-effective public health measures for controlling infectious diseases. Coxiella burnetii is the etiological agent of Q fever, a disease with a wide clinical spectrum that ranges from mild symptoms, such as fever and fatigue, to more severe disease, such as pneumonia and endocarditis. The formalin-inactivated whole-cell vaccine Q-VAX® contains hundreds of antigens and confers lifelong protection in humans, but prior sensitization from infection or vaccination can result in deleterious reactogenic responses to vaccination. Consequently, there is great interest in developing non-reactogenic alternatives based on adjuvanted recombinant proteins. In this study, we aimed to develop a multivalent vaccine that conferred protection with reduced reactogenicity. We hypothesized that a multivalent vaccine consisting of multiple antigens would be more immunogenic and protective than a monovalent vaccine owing to the large number of potential protective antigens in the C. burnetii proteome. To address this, we identified immunogenic T and B cell antigens, and selected proteins were purified to evaluate with a combination adjuvant (IVAX-1), with or without C. burnetii lipopolysaccharide (LPS) in immunogenicity studies in vivo in mice and in a Hartley guinea pig intratracheal aerosol challenge model using C. burnetii strain NMI RSA 493. The data showed that multivalent vaccines are more immunogenic than monovalent vaccines and more closely emulate the protection achieved by Q-VAX. Although six antigens were the most immunogenic, we also discovered that multiplexing beyond four antigens introduces detectable reactogenicity, indicating that there is an upper limit to the number of antigens that can be safely included in a multivalent Q-fever vaccine. C. burnetii LPS also demonstrates efficacy as a vaccine antigen in conferring protection in an otherwise monovalent vaccine formulation, suggesting that its addition in multivalent vaccines, as demonstrated by a quadrivalent formulation, would improve protective responses.

Identification of peptides presented through the MHC-II of dendritic cells stimulated with Mycobacterium avium

Mycobacterium avium (M. avium) represents a species of concern, because of its ability to modulate the host's innate immune response, and therefore influence trajectory of adaptative immunity. Since eradicative response against mycobacteria, and M. tuberculosis/M. avium, relies on peptides actively presented on a Major Histocompatibility complex-II (MHC-II) context, we assessed paradoxical stimulation of Dendritic Cell resulting on immature immunophenotype characterized by membrane minor increase of MHC-II and CD40 despite of high expression of the pro-inflammatory tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) in supernatants. Identification of M. avium leucine rich peptides forming short α-helices shutting down Type 1T helper (Th1), contribute to the understanding of immune evasion of an increasingly prevalent pathogen, and may provide a basis for future immunotherapy to infectious and non-infectious disease.

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.

Development of a Novel Multi-Epitope Vaccine Candidate against Streptococcus Iniae Infection in Fish: An Immunoinformatics Study

Streptococcus Iniae infection is recognized as a disease with substantial economic losses, infecting a wide range of fish species. The limitations of current vaccines and strategies have led to the identification of new methods to control this disease. Multi-epitope vaccines which employ various immunogenic proteins can be promising. The current research project aimed to design an efficient multi-epitope vaccine against Streptococcus Iniae infection in fish. To this end, six immunogenic proteins of Streptococcus Iniae, including FBA, ENO, Sip11, GAPDH, MtsB, and SCPI proteins, were applied for epitope prediction. The best B cell, T cell, and IFNγ epitopes of the immunogenic proteins, as well as interleukin-8, were used to construct a multi-epitope vaccine. Thereafter, different parameters of the designed vaccine, including physicochemical features, antigenicity, secondary structure, and tertiary structure, were evaluated. Moreover, the interaction of the interleukin-8 domain of the designed vaccine and its receptor was investigated by molecular docking strategy. Finally, nucleotide sequence of the vaccine was adapted to express in Escherichia coli. The results of the present study pointed out that the designed vaccine was a stable vaccine with molecular weight and antigenicity score of 45 kDa and 0.936, respectively. Furthermore, the structure analysis results revealed that the designed vaccine contained 23.49% alpha helix, with 90.5% residues in favored region. Finally, it was demonstrated that the interleukin-8 domain of the designed vaccine could be successfully docked to its receptor with the lowest energy of -1020.9. Based on the obtained results, it seems that the designed vaccine can be an efficient candidate to prevent Streptococcus Iniae infection in fish.

In Silico Design of a New Multi-Epitope Peptide-Based Vaccine Candidate Against Q Fever

Novel types of the vaccines with high immunogenicity and low risks, including epitope-based vaccines, are sought. Among zoonotic disease, Q fever caused by Coxiella burnetii is an important target due to numerous outbreaks and the pandemic potential. Here we present a synthetic multi-epitope vaccine against Coxiella burnetii. This vaccine was developed using immunoinformatics approach. Antigenic proteins were studied, and five T cell epitopes were selected. Antigenicity, allergenicity, and toxicity of the selected epitopes were evaluated using the VaxiJen 2.0, AllerTOP, and ToxinPred servers, respectively. Selected epitopes were joined in a peptide sequence, with the cholera toxin B subunit (CTXB) as an adjuvant. The affinity of the proposed vaccine to MHC I and II molecules was measured in a molecular docking study. Resultant vaccine has high antigenicity, stability, and a half-life compatible with utilization in vaccination programs. In conclusion, the validated epitope sequences may be used as a potential vaccine to ensure protection against Q fever agent.

Identification of Immunogenic Linear B-Cell Epitopes in C. burnetii Outer Membrane Proteins Using Immunoinformatics Approaches Reveals Potential Targets of Persistent Infections

Coxiella burnetii is a global, highly infectious intracellular bacterium, able to infect a wide range of hosts and to persist for months in the environment. It is the etiological agent of Q fever—a zoonosis of global priority. Currently, there are no national surveillance data on C. burnetii’s seroprevalence for any South American country, reinforcing the necessity of developing novel and inexpensive serological tools to monitor the prevalence of infections among humans and animals—especially cattle, goats, and sheep. In this study, we used immunoinformatics and computational biology tools to predict specific linear B-cell epitopes in three C. burnetii outer membrane proteins: OMP-H (CBU_0612), Com-1 (CBU_1910), and OMP-P1 (CBU_0311). Furthermore, predicted epitopes were tested by ELISA, as synthetic peptides, against samples of patients reactive to C. burnetii in indirect immunofluorescence assay, in order to evaluate their natural immunogenicity. In this way, two linear B-cell epitopes were identified in each studied protein (OMP-H_(51–59), OMP-H_(91–106), Com-1_(57–76), Com-1_(191–206), OMP-P1_(197–209), and OMP-P1_(215–227)); all of them were confirmed as naturally immunogenic by the presence of specific antibodies in 77% of studied patients against at least one of the identified epitopes. Remarkably, a higher frequency of endocarditis cases was observed among patients who presented an intense humoral response to OMP-H and Com-1 epitopes. These data confirm that immunoinformatics applied to the identification of specific B-cell epitopes can be an effective strategy to improve and accelerate the development of surveillance tools against neglected diseases.

Proteome-wide analysis of Coxiella burnetii for conserved T-cell epitopes with presentation across multiple host species

Background

Coxiella burnetii is the Gram-negative bacterium responsible for Q fever in humans and coxiellosis in domesticated agricultural animals. Previous vaccination efforts with whole cell inactivated bacteria or surface isolated proteins confer protection but can produce a reactogenic immune responses. Thereby a protective vaccine that does not cause aberrant immune reactions is required. The critical role of T-cell immunity in control of C. burnetii has been made clear, since either CD8⁺ or CD4⁺ T cells can empower clearance. The purpose of this study was to identify C. burnetii proteins bearing epitopes that interact with major histocompatibility complexes (MHC) from multiple host species (human, mouse, and cattle).

Results

Of the annotated 1815 proteins from the Nine Mile Phase I (RSA 493) assembly, 402 proteins were removed from analysis due to a lack of inter-isolate conservation. An additional 391 proteins were eliminated from assessment to avoid potential autoimmune responses due to the presence of host homology. We analyzed the remaining 1022 proteins for their ability to produce peptides that bind MHCI or MHCII. MHCI and MHCII predicted epitopes were filtered and compared between species yielding 777 MHCI epitopes and 453 MHCII epitopes. These epitopes were further examined for presentation by both MHCI and MHCII, and for proteins that contained multiple epitopes. There were 31 epitopes that overlapped positionally between MHCI and MHCII across host species. Of these, there were 9 epitopes represented within proteins containing ≥ 5 total epitopes, where an additional 24 proteins were also epitope dense. In all, 55 proteins were found to contain high scoring T-cell epitopes. Besides the well-studied protein Com1, most identified proteins were novel when compared to previously studied vaccine candidates.

Conclusion

These data represent the first proteome-wide evaluation of C. burnetii peptide epitopes. Furthermore, the inclusion of human, mouse, and bovine data capture a range of hosts for this zoonotic pathogen plus an important model organism. This work provides new vaccine targets for future vaccination efforts and enhances opportunities for selecting multiple T-cell epitope types to include within a vaccine.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-021-04181-w.

Engineering an efficient poly-epitope vaccine against Toxoplasma gondii infection: A computational vaccinology study

Toxoplasmosis is a zoonotic disease caused by Toxoplasma gondii. Despite the importance of toxoplasmosis, there is no comprehensive strategy to control this disease. Hence, applying the new methods such as the poly-epitope vaccine can be successful. In the current project, to engineer a potent poly-epitope vaccine, 10 antigenic proteins including BiP, GRA1, GRA2, GRA5, MIC8, MIC13, P30, PI1, SOD and Rop2 were selected based on the database. Then, B cell, MHCI and MHCII epitopes of the selected antigenic proteins were isolated by the most accurate servers. The best predicted epitopes along with a molecular adjuvant were employed to engineer a poly-epitope vaccine. After engineering, different physicochemical features, secondary and tertiary structures, molecular docking of the designed vaccine were assessed. The results of this project revealed that the designed vaccine with 730 amino acids in length and molecular weight of 77.67 kDa was a soluble protein which could bind to its receptor with an energy of 6223.43. According to the achievements of this study, it seems the designed vaccine can be an appropriate candidate to apply.

Computational design of a novel multi-epitope vaccine against Coxiella burnetii

Query fever is a zoonotic disease caused by Coxiella burnetii. There is no universal method for the prevention of this disease. Recombinant vaccine is a potent strategy that can be utilized for this purpose. The current study was conducted to develop a multi-epitope vaccine against Coxiella burnetii. Hence, OmpA, Tuf2, GroEL, Mip and sucB antigens were used for the prediction of epitopes. Then, a multi-epitope vaccine was developed based on a molecular adjuvant and fragments that contained the best MHCI, B cell, MHCII and IFN-γ epitopes. The features of the developed vaccine including physicochemical parameters, antigenicity and protein structures were assessed. Also, interaction between the developed vaccine and TLR4/MD2 receptor along with molecular dynamics of the ligand-receptor complex were investigated. Finally, the codon adaptation and cloning were conducted for the developed vaccine. According to the results, molecular weight, instability index, antigenicity and random coil percentage of the developed vaccine were 54.4 kDa, 32.84, 1.1936 and 34.92%, respectively. Besides, residues distribution in core region of the refined model was 85%. The results demonstrated that the developed vaccine could dock to its receptor with the lowest energy of -976.7 as well as RMSD value of the complex was between 0.15 and 0.22 nm. Also, the results showed that CIA index of the codon adapted sequence was 0.95. Finally, cloning results revealed that nucleotide sequence of the developed vaccine could be successfully cloned into pET-21a (+). Based on these results, it seems that the developed vaccine can be a suitable candidate to prevent Coxiella burnetii.