Review on the identification and role of Toxoplasma gondii antigenic epitopes

In Silico Analysis and Characterization of the Immunogenicity of Toxoplasma gondii Rhoptry Protein 18

Rhoptry protein 18 (ROP18) is a key virulence factor secreted into host cells during the invasion of Toxoplasma gondii (T. gondii) and plays an important role in the pathogenesis of infection. Due to its potential as a vaccine candidate, this study aimed to characterize several properties of the T. gondii ROP18 (TgROP18) protein to support its inclusion in vaccine formulations. Using a range of bioinformatics tools, we investigated its T-cell and B-cell epitopes, physicochemical properties, subcellular localization, transmembrane domains, and tertiary and secondary structures. Our analysis revealed 48 post-translational modification sites in TgROP18. The secondary structure was composed of 4.87% beta-turns, 38.45% random coils, 42.42% alpha helices, and 14.26% extended strands. Several potential T- and B-cell epitopes were identified on ROP18. The Ramachandran plot of both crude and refined models showed that 85.8% and 95.3% of the amino acid residues, respectively, fell within favored regions, indicating energetically stable conformations. Allergenicity and antigenicity assessments indicated that TgROP18 is a nonallergenic, immunogenic protein. Predictions using the C-ImmSim server suggest that TgROP18 can stimulate humoral and cell-mediated immune responses, based on antibody titers and cytokine profiles following antigen administration. These findings provide baseline data for future investigations focused on the potential of TgROP18 in developing therapeutic strategies against toxoplasmosis.

Toxoplasma gondii (GRA10): A Closer Glance Into Immunogenic and Biochemical Characteristics Using In Silico Approach

Toxoplasma gondii, an obligate, intracellular, protozoan parasite, is known to infect a wide range of warm-blooded animals, including livestock, marine mammals and humans leading to the development of toxoplasmosis. The dense granule antigens (GRAs) have garnered crucial role in parasite survival, virulence and the formation of the parasitophorous vacuole. The study focusing on the GRA10 protein of T. gondii aims to elucidate its features further to support its potential inclusion in future vaccine formulations. The present study provided an exhaustive elucidation of the key characteristics of the GRA10 protein, encompassing its presence of a transmembrane domain, physico-chemical properties, subcellular localization, potential epitopes recognised by B-cells and T-cells, secondary and tertiary structures, as well as other significant attributes of this protein. The results indicated that the GRA10 protein possesses a total of 192 possible post-translational modification sites, with no transmembrane domains being detected within its structure. In terms of secondary structure, the GRA10 protein is composed of 27.74% alpha-helix, 13.53% extended strand and 58.72% random coil elements. Additionally, various potential B- and T-cell epitopes were pinpointed for the GRA10 protein, suggesting its immunogenic properties. The assessment of antigenicity and allergenicity further confirmed that GRA10 is immunogenic but non-allergenic, making it a promising candidate for further study. Furthermore, the induction of IFN-γ and IL-4 highlighted the ability of related MHC-II molecules to interact with GRA10, indicating its potential role in immune responses. These findings shed light on the multifaceted nature of the GRA10 protein and its significance in immunological processes. The study presented crucial fundamental and theoretical information regarding GRA10 in order to facilitate the creation of a potent vaccine against both acute and chronic toxoplasmosis, warranting additional in vivo examinations.

Structural Prediction and Antigenic Analysis of ROP18, MIC4, and SAG1 Proteins to Improve Vaccine Design against Toxoplasma gondii: An In silico Approach

BACKGROUND

Toxoplasmosis is a cosmopolitan infectious disease in warmblooded mammals that poses a serious worldwide threat due to the lack of effective medications and vaccines.

AIMS

The purpose of this study was to design a multi-epitope vaccine using several bioinformatics approaches against the antigens of Toxoplasma gondii (T. gondii).

METHODS

Three proteins of T. gondii, including ROP18, MIC4, and SAG1 were analyzed to predict the most dominant B- and T-cell epitopes. Finally, we designed a chimeric immunogen RMS (ROP18, MIC4, and SAG1) using some domains of ROP18 (N377-E546), MIC4 (D302-G471), and SAG1 (T130-L299) linked by rigid linker A (EAAAK) A. Physicochemical properties, secondary and tertiary structure, antigenicity, and allergenicity of RMS were predicted utilizing immunoinformatic tools and servers.

RESULTS

RMS protein had 545 amino acids with a molecular weight (MW) of 58,833.46 Da and a theoretical isoelectric point (IP) of 6.47. The secondary structure of RMS protein contained 21.28% alpha-helix, 24.59% extended strand, and 54.13% random coil. In addition, evaluation of antigenicity and allergenicity showed the protein to be an immunogen and nonallergen. The results of the Ramachandran plot indicated that 76.4%, 12.9%, and 10.7% of amino acid residues were incorporated in the favored, allowed, and outlier regions respectively. ΔG of the best-predicted mRNA secondary structure was -593.80 kcal/mol which indicates a stable loop is not formed at the 5' end.

CONCLUSION

Finally, the accuracy and precision of the in silico analysis must be confirmed by successful heterologous expression and experimental studies.

In silico analysis and structural vaccinology prediction of Toxoplasma gondii ROP41 gene via immunoinformatics methods as a vaccine candidate

INTRODUCTION

Toxoplasma gondii (T. gondii) infects all warm-blooded animals, including humans. Currently, no effective treatments exist to prevent the generation of chronic tissue cysts in infected hosts. Therefore, developing a vaccine to protect to deal with toxoplasmosis is a promising strategy, as a single immunization could provide lifelong protective immunity. Rhoptry proteins (ROPs) play a vital role for the parasite's survival within host cells and perform critical functions during different phases of parasite invasion. Little is known about ROP41 gene. Nevertheless, Understanding the characteristics of ROP41 will enhance diagnostic and vaccine research.

MATERIALS AND METHODS

The current article provides a comprehensive analysis of the essential components of the ROP41 protein, including its transmembrane domain, physico-chemical properties, subcellular location, tertiary and secondary structures, and potential T- and B-cell epitopes. These features were determined by many bioinformatics approaches to identify possible epitopes for developing a highly effective vaccine.

RESULTS

ROP41 protein showed 36 possible post-translational modification regions. The ROP41 protein secondary structure contains 17.35 % extended strand, 33.47 % alpha-helix, and 49.18 % random coil. Also, ROP41 showed many possible B- and T-cell epitopes. According to the Ramachandran plot, 90.78 % of amino acid residues had been placed in favored, 3.28 % in outlier, and 5.94 % in allowed areas. Also, the allergenicity and antigenicity evaluation indicated that ROP41 is non-allergenic and immunogenic.

CONCLUSION

The current study offered critical basic and conceptual information on ROP41 to increase a successful vaccine in opposition to continual and acute toxoplasmosis for in addition in vivo assessments. Further research is necessary for the development of vaccines utilizing ROP41 alone or combined with various antigens.

A new multi-epitope DNA vaccine against Helicobacter Pylori infection in a BALB/c mouse model

Background

Helicobacter Pylori (H. Pylori) is a pathogen that may invade the human stomach. This bacterial strain is now causing widespread concern and considerable health issues worldwide. In contrast to antibiotic treatment, which may lead to drug resistance, vaccination therapy is emerging as a possible immunotherapy option for H. Pylori. DNA vaccines are a potential option to traditional vaccines among vaccine research methods. Furthermore, the multiepitope DNA vaccination may induce a broader immune response to suppress H. Pylori infection.

Methods

Four target antigenic proteins (outer membrane beta-barrel, outer membrane beta, HofA, and hcp beta-lactamase-like protein) were used to identify epitopes. The best B and T cell epitopes were selected to induce humoral and cellular immune responses and were connected using the HEYGAEALERAG and GGGS linkers. The peptide's physicochemical characteristics, secondary and tertiary structures, antigenicity, and allergenicity were evaluated utilizing several bioinformatics tools. The multiepitope peptide was successfully inserted into the pcDNA3.1 expression vector. The immunological responses of both the vaccinated and control groups were evaluated by measuring cytokines and antibodies.

Results

Based on the data, the multiepitope peptide consists of 278 amino acid residues and has an average molecular weight (MW) of 28643.61 Da. The peptide residues were mainly situated within the preferred and permitted areas of the Ramachandran plot, accounting for 92.86 % of the total. The VaxiJen server has calculated that the multiepitope peptide has an antigenicity score of 1.0067. BALB/c mice vaccinated with the DNA vaccine produced significantly higher levels of specific IgG antibodies (p < 0.05). The vaccinated mice exhibited a TH1-type cellular immune response characterized by the generation of IFN-γ and a longer length of life compared to the control animals (p < 0.05). In addition, the vaccination group exhibited a substantial increase in the expression level of IFN-γ and IL-1β genes compared to the control group (p < 0.05).

Conclusions

The results demonstrated that the multiepitope DNA vaccine elicited significant humoral and cellular responses, and increased survival time in BALB/c mice, indicating that selecting potential epitopes may be a viable technique for developing multiepitope-based vaccines. This can help to introduce effective vaccines.

Completing the pieces of a puzzle: in-depth probing of Toxoplasma gondii rhoptry protein 4 as a promising target for vaccination using an in-silico approach

The present study aimed to evaluate the key characteristics of Toxoplasma gondii rhoptry protein 4 (TgROP4), including physicochemical parameters, structural features, immunogenic epitopes, and virtual immune simulation, using several bioinformatics-based servers and tools. Based on allergenicity and antigenicity outputs, the TgROP4 protein seemed to have an immunogenic and non-allergenic nature. The quality of the three-dimensional (3D) structure improved after refinement, according to the outcomes of the Ramachandran plot and the ProSA-web servers. ABCpred and SVMTriP web tools were used to predict linear B lymphocyte epitopes and found several promising epitopes. Acceptable antigenicity, hydrophilicity, beta-turn, Bepipred linear epitope 2.0, flexibility, and surface accessibility scores were obtained through the Immune Epitope Database (IEDB). Also, seven discontinuous B-cell epitopes ranging from scores 0.966 to 0.848 were found in the 3D model of TgROP4 via the ElliPro. The IEDB findings showed T-cell epitopes on TgROP4 protein are capable to strongly bind to the major histocompatibility complex classes. In silico immune simulation was performed using C-ImmSim server and showed three injections of TgROP4 protein at 4-week intervals is capable to elicit adequate humoral and cell-mediated immune responses.

In Silico Analysis of the ROP29 Protein as a Vaccine Candidate Against Toxoplasma gondii

The progression of Toxoplasma gondii (T. gondii) invasion is aided by rhoptry proteins (ROPs), which are also crucial for the parasite's survival in host cells. In this study, in silico analysis was performed to examine the various aspects of the ROP29 protein, such as physicochemical properties, potential T- and B-cell epitopes, and other significant features. The research revealed that there were 55 possible sites for posttranslational modification in the ROP29 protein. The secondary structure of the ROP29 protein consists of a random coil, an alpha-helix, and an extended strand, which account for 49.69%, 36.81%, and 13.50%, respectively. Moreover, a number of putative T- and B-cell epitopes for ROP29 were found. The Ramachandran plot showed that 88.91% (crude model) and 97.54% (refine model) of the amino acid residues were located in the favored regions. Also, the testing of this protein's antigenicity and allergenicity showed that it was nonallergenic and immunogenic. Our results suggested that employing in silico tools to apply structural and functional predictions to the ROP29 protein can lower the likelihood that laboratory investigations will fail. This research served as a crucial foundation for further research. More research is required in the future in suitable animal model employing ROP29 alone or in combination with other antigens.

Immunoinformatics studies and design of a novel multi-epitope peptide vaccine against Toxoplasma gondii based on calcium-dependent protein kinases antigens through an in-silico analysis

Purpose

Infection by the intracellular apicomplexan parasite Toxoplasma gondii has serious clinical consequences in humans and veterinarians around the world. Although about a third of the world's population is infected with T. gondii, there is still no effective vaccine against this disease. The aim of this study was to develop and evaluate a multimeric vaccine against T. gondii using the proteins calcium-dependent protein kinase (CDPK)1, CDPK2, CDPK3, and CDPK5.

Materials and Methods

Top-ranked major histocompatibility complex (MHC)-I and MHC-II binding as well as shared, immunodominant linear B-cell epitopes were predicted and linked using appropriate linkers. Moreover, the 50S ribosomal protein L7/L12 (adjuvant) was mixed with the construct's N-terminal to increase the immunogenicity. Then, the vaccine's physicochemical characteristics, antigenicity, allergenicity, secondary and tertiary structure were predicted.

Results

The finally-engineered chimeric vaccine had a length of 680 amino acids with a molecular weight of 74.66 kDa. Analyses of immunogenicity, allergenicity, and multiple physiochemical parameters indicated that the constructed vaccine candidate was soluble, non-allergenic, and immunogenic, making it compatible with humans and hence, a potentially viable and safe vaccine candidate against T. gondii parasite.

Conclusion

In silico, the vaccine construct was able to trigger primary immune responses. However, further laboratory studies are needed to confirm its effectiveness and safety.

Bioinformatics-based prediction and screening of immunogenic epitopes of Toxoplasma gondii rhoptry proteins 7, 21 and 22 as candidate vaccine target

INTRODUCTION

Toxoplasmosis is a well-known zoonotic disease caused by Toxoplasma gondii. The main causes of the disease range from eating undercooked or contaminated meat and shellfish to cleaning litter trays into which cats that excreted toxoplasma via faeces. This pathogen can live for a very long time, possibly a lifetime, within the bodies of humans and other animals.

AIMS AND OBJECTIVES

This study aimed to predict and analyse candidate immunogenic epitopes for vaccine development by evaluating the physio-chemical properties, multiple sequence alignment, secondary and tertiary structures, phosphorylation sites, transmembrane domains, and signal peptides, of T. gondii rhoptry proteins ROP7, ROP21, and ROP22 using bioinformatics tools.

METHODS

To find immunogenic epitopes of rhoptry proteins, numerous bioinformatics web servers were used containing multiple sequence alignment, physiochemical properties, antigenicity and allergenicity, post-translational modification sites (PTMs), signal peptides, transmembrane domains, secondary and tertiary structures, and screening of predicted epitopes. We evaluated immunogenic linear B-cell epitopes as candidate proteins for vaccine development.

RESULTS

Nine epitopes were identified for each protein, and analysis of immunogenicity, revealed three candidate epitopes for ROP7, one for ROP21, and four for ROP22. Among all candidate epitopes, ROP22 contained the most immunogenic epitopes with immunogenicity score of 0.50575.

CONCLUSION

We acquired detailed information on predicted immunogenic epitopes using in-silico methods. The results provide a foundation for further experimental analysis of toxoplasmosis, and potential vaccine development.

Preparation and Preliminary Application of Epitope Peptide-Based Antibody against Toxoplasma gondii GRA3

Toxoplasma gondii dense granule protein GRA3 has been shown to promote Toxoplasma gondii transmission and proliferation by interacting with the host cell endoplasmic reticulum (ER) through calcium-regulated cyclophilin ligands (CAMLG). Although many studies have focused on the interaction between the host cell endoplasmic reticulum and GRA3, no polyclonal antibodies (PcAbs) against GRA3 have been reported to date. According to the antigenicity prediction and exposure site analysis, three antigen peptide sequences were selected to prepare polyclonal antibodies targeting GRA3. Peptide scans revealed that the major antigenic epitope sequences were 125ELYDRTDRPGLK136, 202FFRRRPKDGGAG213, and 68NEAGESYSSATSG80, respectively. The GRA3 PcAb specifically recognized the GRA3 of T. gondii type Ⅱ ME49. The development of PcAbs against GRA3 is expected to elucidate the molecular mechanisms by which GRA3 regulates host cell function and contribute to the development of diagnostic and therapeutic strategies for toxoplasmosis.

Identification of Cytotoxic T lymphocyte (CTL) Epitope and design of an immunogenic multi-epitope of Bovine Ephemeral Fever Virus (BEFV) Glycoprotein G for Vaccine Development

Bovine ephemeral fever (BEF), a vector-borne disease of cattle and water buffalo, is enzootic in tropical and subtropical zones of Asia, Australia, and Africa. Since cytotoxic T lymphocytes (CTL) responses may play a key role in the control of bovine ephemeral fever virus (BEFV) infection, it is important to identify and characterize the CTL target epitopes of BEFV antigens. The current study has been designed to identify and characterize the potential CTL epitopes using the Immuno-informatics tools, and it helped find the potent vaccine candidates against BEF. Antigenicity, toxicity, allergenicity, and immunogenicity testing of predicted CTL epitopes was done. Total four CTL epitopes for BEFV G protein, have been identified as potential epitopes. Prediction of the 3D structure of multi-epitope (final structure) was performed using I-TASSER server. Model 1 was selected as the best model with C-Score: -3.71. The modeled G protein structure and multi-epitope structure were validated by the Ramachandran plots Prosa and Verify 3D server. Epitopic regions of 3D protein structure were identified by Chimera UCSF software. Physicochemical properties of the Multi epitope were evaluated using ProtParam server. This is the first report of CTL epitope in the G protein of BEFV. In this manner, they would play an important role in evoking the immune response as well as vaccine development. However, in vitro and in vivo experimental studies are required for suggested epitopes verification. The multi-epitope was designed from regions of the G protein sequence that lacked mutation and genomic diversity. Therefore, it can be introduced as a protein vaccine from all strains of BEFV as a vaccine candidate for design.

Immunoinformatic Analysis of Calcium-Dependent Protein Kinase 7 (CDPK7) Showed Potential Targets for Toxoplasma gondii Vaccine

Apicomplexan parasites, including Toxoplasma gondii (T. gondii), express different types of calcium-dependent protein kinases (CDPKs), which perform a variety of functions, including attacking and exiting the host cells. In the current bioinformatics study, we have used several web servers to predict the basic features and specifications of the CDPK7 protein. The findings showed that CDPK7 protein has 2133 amino acid residues with an average molecular weight (MW) of 219085.79 D. The aliphatic index with 68.78 and grand average of hydropathicity (GRAVY) with -0.331 score were estimated. The outcomes of current research showed that the CDPK7 protein included 502 alpha-helix, 1311 random coils, and 320 extended strands with GOR4 method. Considering the Ramachandran plot, the favored region contains more than 92% of the amino acid residues. In addition, evaluation of antigenicity and allergenicity showed that CDPK7 protein has immunogenic and nonallergenic nature. The present research provides key data for more animal-model study on the CDPK7 protein to design an efficient vaccine against toxoplasmosis in the future.

Multi-epitope vaccine expressed in Leishmania tarentolae confers protective immunity to Toxoplasma gondii in BALB/c mice

Current study deals with a novel multi-epitope vaccine designed in silico and its confirmation experiments for potential efficacy in BALB/c mice. Major histocompatibility complex (MHC)-binding and B-cell binding epitopes of five Toxoplasma antigens (SAG1, ROP16, GRA12, MIC4 and M2AP) were predicted. Selected epitopes were fused together using SAPGTP linker, and antigenicity, allergenicity, physico-chemical features, secondary and tertiary structures and validations were all performed via bioinformatics servers. Then, vaccine construct was cloned into pLEXSY-neo 2.1 vector. After Leishmania tarentolae transfection, live recombinant and wild parasites were subcutaneously injected into 6-8 week female BALB/c mice and immune responses were measured. Results showed that the peptide possessed 282 amino acid residues with average molecular weight of 28.06 kDa. About 90% of the peptide residues were incorporated in favored and allowed regions of the Ramachandran plot. Vaccinated mice showed remarkably elevated levels of specific antibodies (P < 0.05) with predominance of IgG2a production. Also, a Th₁ immune response with production of IFN-γ and relatively increased survival rate against intraperitoneal challenge with RH strain was demonstrated in immunized mice than control groups (P < 0.05). Also, very low levels of IL-4 were demonstrated, which showed statistically significant association with controls (P < 0.05). The findings clarified that multi-epitope vaccine expressed in Leishmania tarentolae induced significant immune responses against acute toxoplasmosis.

Bioinformatics analysis of calcium-dependent protein kinase 4 (CDPK4) as Toxoplasma gondii vaccine target

OBJECTIVES

Toxoplasma gondii (T. gondii), an obligate intracellular apicomplexan parasite, could affect numerous warm-blooded animals, such as humans. Calcium-dependent protein kinases (CDPKs) are essential Ca²⁺ signaling mediators and participate in parasite host cell egress, outer membrane motility, invasion, and cell division.

RESULTS

Several bioinformatics online servers were employed to analyze and predict the important properties of CDPK4 protein. The findings revealed that CDPK4 peptide has 1158 amino acid residues with average molecular weight (MW) of 126.331 KDa. The aliphatic index and GRAVY for this protein were estimated at 66.82 and - 0.650, respectively. The findings revealed that the CDPK4 protein comprised 30.14% and 34.97% alpha-helix, 59.84% and 53.54% random coils, and 10.02% and 11.49% extended strand with SOPMA and GOR4 tools, respectively. Ramachandran plot output showed 87.87%, 8.40%, and 3.73% of amino acid residues in the favored, allowed, and outlier regions, respectively. Also, several potential B and T-cell epitopes were predicted for CDPK4 protein through different bioinformatics tools. Also, antigenicity and allergenicity evaluation demonstrated that this protein has immunogenic and non-allergenic nature. This paper presents a basis for further studies, thereby provides a fundamental basis for the development of an effective vaccine against T. gondii infection.

Immunoinformatic analysis of immunogenic B- and T-cell epitopes of MIC4 protein to designing a vaccine candidate against Toxoplasma gondii through an in-silico approach

Purpose

Toxoplasmosis, transmitted by Toxoplasma gondii, is a worldwide parasitic disease that affects approximately one-third of the world's inhabitants. Today, there are no appropriate drugs to deter tissue cysts from developing in infected hosts. So, developing an effective vaccine would be valuable to avoid from toxoplasmosis. Considering the role of microneme antigens such as microneme protein 4 (MIC4) in T. gondii pathogenesis, it can be used as potential candidates for vaccine against T. gondii.

Materials and Methods

In this study several bioinformatics methods were used to assess the different aspects of MIC4 protein such as secondary and tertiary structure, physicochemical characteristics, the transmembrane domains, subcellular localization, B-cell, helper-T lymphocyte, cytotoxic-T lymphocyte epitopes, and other notable characteristic of this protein design a suitable vaccine against T. gondii.

Results

The studies revealed that MIC4 protein includes 59 potential post-translational modification sites without any transmembrane domains. Moreover, several probable epitopes of B- and T-cells were detected for MIC4. The secondary structure comprised 55.69% random coil, 5.86% beta-turn, 19.31% extended strand, and 19.14% alpha helix. According to the Ramachandran plot results, 87.42% of the amino acid residues were located in the favored, 9.44% in allowed, and 3.14% in outlier regions. The protein allergenicity and antigenicity revealed that it was non-allergenic and antigenic.

Conclusion

This study gives vital basic on MIC4 protein for further research and also established an effective vaccine with different techniques against acute and chronic toxoplasmosis.

In silico analysis and expression of a new chimeric antigen as a vaccine candidate against cutaneous leishmaniasis

Objective(s):

Since leishmaniasis is one of the health problems in many countries, the development of preventive vaccines against it is a top priority. Peptide vaccines may be a new way to fight the Leishmania infection. In this study, a silicon method was used to predict and analyze B and T cells to produce a vaccine against cutaneous leishmaniasis.

Materials and Methods:

Immunodominant epitope of Leishmania were selected from four TSA, LPG3, GP63, and Lmsti1 antigens and linked together using a flexible linker (SAPGTP). The antigenic and allergenic features, 2D and 3D structures, and physicochemical features of a chimeric protein were predicted. Finally, through bioinformatics methods, the mRNA structure was predicted and was produced chemically and cloned into the pLEXY-neo2 vector.

Results:

Results indicated, polytope had no allergenic properties, but its antigenicity was estimated to be 0.92%. The amino acids numbers, molecular weight as well as negative and positive charge residuals were estimated 390, ~41KDa, 41, and 30, respectively. The results showed that the designed polytope has 50 post-translationally modified sites. Also, the secondary structure of the protein is composed of 25.38% alpha-helix, 12.31% extended strand, and 62.31% random coil. The results of SDS-PAGE and Western blotting revealed the recombinant protein with ~ 41 kDa. The results of Ramachandran plot showed that 96%, 2.7%, and 1.3% of amino acid residues were located in the preferred, permitted, and outlier areas, respectively.

Conclusion:

It is expected that the TLGL polytope will produce a cellular immune response. Therefore, the polytope could be a good candidate for an anti-leishmanial vaccine.

In-depth computational analysis of calcium-dependent protein kinase 3 of Toxoplasma gondii provides promising targets for vaccination

Purpose

The Toxoplasma gondii calcium-dependent protein kinase-3 (CDPK3) is a key enzyme for parasite egress, control of calcium-dependent permeabilization in parasitophorous vacuole membrane and tissue cyst formation. In this study, we comprehensively explored the bioinformatics features of this protein to improve vaccine design against T. gondii.

Materials and Methods

Various web servers were employed for the analysis of physico-chemical properties, post-translational modifications, localization in the subcellular milieu, secondary and tertiary structures, as well as B-cell, major histocompatibility complex (MHC)-binding and cytotoxic T-lymphocyte (CTL) epitopes.

Results

This protein was a 537 amino acid antigenic and non-allergenic molecule with a molecular weight of 60.42 kDa, a grand average of hydropathicity score of −0.508, and aliphatic index of 79.50. There exists 46.74% alpha helix, 12.48% extended strand, and 40.78% random coil in the secondary structure. Ramachandran plot of the refined model demonstrated 99.3%, 0.7%, and 0.0% of residues in the favored, allowed and outlier areas, respectively. Besides, various potential B-cell (continuous and conformational), MHC-binding and CTL epitopes were predicted for Toxoplasma CDPK3 protein.

Conclusion

This article provides a foundation for further investigations, and laid a theoretical basis for the development of an appropriate vaccine against T. gondii infection.

Construction of A Synthetic Gene Encoding the Multi-Epitope of Toxoplasma gondii and Demonstration of the Relevant Recombinant Protein Production: A Vaccine Candidate

BACKGROUND

Toxoplasma gondii is a widely-distributed parasite all over the world whose attributed severe afflicting complications in human necessitate the development of serodiagnostic tests and vaccines for it. Immunological responses to monovalent vaccines and the application of diagnostic reagents including single antigens are not optimally effective. Bioinformatics approaches were used to introduce these epitopes, predict their immunogenicity and preliminarily evaluate their potential as an effective DNA vaccine and for serodiagnostic goals.

MATERIALS AND METHODS

A 3D structure of proteins was predicted by I-TASSER server, and linear and conformational B cell and T cell epitopes were predicted using the online servers. Then, the predicted epitopes were constructed and called Toxoeb, and their expression in the prokaryotic and eukaryotic cells was demonstrated using SDS-PAGE. In the next step, Western blotting with pooled sera of mice infected with T. gondii was done.

RESULTS

The current in silico analysis revealed that the B cell epitopes with high immunogenicity for GRA4 protein were located in the residues 34-71, and 230-266, for GRA14 in 308-387, for SAG1 in 182-195, 261-278, and for GRA7 in residues 101-120, 160-176. The T cell epitopes were selected in overlapping regions with the B cell epitopes. The immunogenic region for GRA4 are in the residues 245-253, 50-58, and 40-54, for GRA14 in 307-315, 351-359, and 308- 322, for SAG1 261-269, and 259-267, and for GRA7 in the residues 103-112, and 167-175. The results of the western blotting showed that the expressed protein had immunogenicity.

CONCLUSION

Our constructed multi-epitope of T. gondii could be considered as a candidate for diagnostic and vaccination purposes.

Bioinformatics analysis of NetF proteins for designing a multi-epitope vaccine against Clostridium perfringens infection

Clostridium perfringens is an important human and animal pathogen that is the primary causative agent of necrotizing enteritis and enterotoxemia in many types of animals. C. perfringens produces a variety of toxins, including NetF which may plays a crucial role in the pathogenesis of foal and canine necrotizing enteritis. In this study, we used several bioinformatics methods to analyze various aspects of the NetF proteins, including the physicochemical properties, secondary and tertiary structures, and the dominant B-cell and T-cell epitopes. The results showed that NetF protein was a stable and hydrophilic protein. The secondary structure of the NetF protein consisted of 2.62% alpha helixes, 6.56% beta turns, 38.69% extended strands and 52.13% random coils. Moreover, several potential B and T-cell epitopes were identified for NetF. In addition, the obtained findings from antigenicity and allergenicity evaluation remarked that this protein is immunogenic and non-allergen. Based on the results of Ramachandran plot, 94.22%, 5. 42%, and 0.36% of amino acid residues were incorporated in the favored, allowed, and outlier regions, respectively. This study provides a foundation for further investigations, and laid a theoretical basis for the development of an appropriate vaccine against C. perfringens infection.

Antigenic properties of dense granule antigen 12 protein using bioinformatics tools in order to improve vaccine design against Toxoplasma gondii

PURPOSE

Toxoplasma gondii is an opportunistic parasite infecting all warm-blooded animals including humans. The dense granule antigens (GRAs) play an important role in parasite survival and virulence and in forming the parasitophorous vacuole. Identification of protein characteristics increases our knowledge about them and leads to develop the vaccine and diagnostic studies.

MATERIALS AND METHODS

This paper gave a comprehensive definition of the important aspects of GRA12 protein, including physico-chemical features, a transmembrane domain, subcellular position, secondary and tertiary structure, potential epitopes of B-cells and T-cells, and other important features of this protein using different and reliable bioinformatics methods to determine potential epitopes for designing of a high-efficient vaccine.

RESULTS

The findings showed that GRA12 protein had 53 potential post-translational modification sites. Also, only one transmembrane domain was recognized for this protein. The secondary structure of GRA12 protein comprises 35.55% alpha-helix, 19.50% extended strand, and 44.95% random coil. Moreover, several potential B- and T-cell epitopes were identified for GRA12. Based on the results of the Ramachandran plot, 79.26% of amino acid residues were located in favored, 11.85% in allowed and 8.89% in outlier regions. Furthermore, the results of the antigenicity and allergenicity assessment noted that GRA12 is immunogenic and non-allergenic.

CONCLUSION

This research provided important basic and conceptual data on GRA12 to develop an effective vaccine against acute and chronic toxoplasmosis for further in vivo investigations. More studies are required on vaccine development using the GRA12 alone or combined with other antigens in the future.

Structural predication and antigenic analysis of ROP16 protein utilizing immunoinformatics methods in order to identification of a vaccine against Toxoplasma gondii: An in silico approach

Toxoplasmosis, caused by Toxoplasma gondii, is a common parasitic disease, affecting almost one-third of the world's population. Currently, there are no effective treatments for inhibiting the formation of chronic tissue cysts in infected hosts. Thus, the production of appropriate vaccines against this pathogen is an important goal to avoid toxoplasmosis. considering the role of rhoptry antigens like ROP16 in virulence and satisfactory immunogenicity, they can be used as promising vaccine candidates against T. gondii. In the present study, an in silico approach was used to analyze various aspects of the ROP16 protein, including physicochemical characteristics, the potential epitopes of B and T-cells, the secondary and tertiary structure, the subcellular localization, the transmembrane domain, and other important features of this protein using several bioinformatics tools to design a proper vaccine against T. gondii. The results showed that ROP16 protein includes 93 potential post-translational modification sites. The secondary structure of the ROP16 protein comprises 34.23% alpha-helix, 54.46% random coil, and 11.32% extended strand. Moreover, several potential B- and T-cell epitopes were identified for ROP16. Based on the results of Ramachandran plot, 84.64% of the amino acid residues were located in the favored, 10.34% in allowed, and 5.02% in outlier regions. Furthermore, the results of the antigenicity and allergenicity assessment noted that this protein was immunogenic and non-allergenic. Our findings suggested that structural and functional predictions applied to ROP16 protein using in silico tools can reduce the failure risk of the laboratory studies. This research provided an important basis for further studies and also developed an effective vaccine against acute and chronic toxoplasmosis by various strategies. Further studies are needed on the development of vaccines in vivo using ROP16 alone or in combination with other antigens in the future.

Rhomboid antigens are promising targets in the vaccine development against Toxoplasma gondii

Toxoplasma gondii (T. gondii) is an obligate intracellular parasite with worldwide distribution. It is estimated that near one-third of the people around the globe are latently seropositive for the parasite. Since the current common drugs are incapable in the elimination of parasites within tissue cysts, the development of an effective vaccine has high priority for researchers to limit the infection. During recent years, non-stop efforts of scientists have made great progress in the identification and development of T. gondii candidate vaccines. However, there is a lack of a commercially licensed vaccine for human application yet. Rhomboid proteases (ROMs) are a class of serine proteases that have an important role in the invasion of the parasites that can be considered as a new target for vaccine strategy. They also play critical roles in mitochondrial fusion and growth factor signaling, allowing the parasite to completely enter into the host cell. In the current review, we have summarized the recent progress regarding the development of ROM-based vaccines against acute and chronic T. gondii infection in animal models.

A systematic review on efficiency of microneme proteins to induce protective immunity against Toxoplasma gondii

Toxoplasma gondii is an intracellular parasite infecting almost all warm-blooded animals. Many studies on vaccination have been performed previously, and micronemal proteins (MICs) have crucial importance in this regard. The current review aims to reveal the efficiency of MICs as target antigen, adjuvants, animal models (species/strain), T. gondii strains for challenge infection, and routes of vaccine to prevent Toxoplasma infection. A comprehensive literature search was performed on April 18, 2018, in several known databases. Studies were included when evaluating vaccines based on MIC against T. gondii compared to that of a control group. Two independent researchers done the search process, study choice, and data extraction. A total of 28 articles published were selected for further analysis. Among them, 57.03% of the studies focused on MIC3 and its epitopes. SAG1 was further used in cocktail vaccines compared to other antigens. GM-CSF and Freund's complete were the predominant adjuvants used. BALB/c mice have been introduced as a proper model for lethal challenge. Virulent T. gondii (RH) was utilized more than other strains for challenge. Among MICs, the results of vaccination with MIC1-4, MIC6, and PLP1 demonstrated significantly strong humoral and cellular immunity, increased survival time, and reduced cyst burden in the mice. This review summarizes the latest results on MIC-based vaccines and presents that the most effective vaccination procedure is the administration of the cocktail vaccines. Our survey can serve as a basis for further studies to develop more efficient novel vaccines against T. gondii for animals and humans.

Plant Hsp90 is a novel adjuvant that elicits a strong humoral and cellular immune response against B- and T-cell epitopes of a Toxoplasma gondii SAG1 peptide

BACKGROUND

The 90-kDa heat-shock protein (Hsp90) from Nicotiana benthamiana (NbHsp90.3) is a promising adjuvant, especially for those vaccines that require a T cell-mediated immune response. Toxoplasma gondii SAG1 is considered one of the most important antigens for the development of effective subunit vaccines. Some epitopes located in the SAG1 C-terminus region have showed a strong humoral and cellular immune response. In the present study, we aimed to assess the efficacy of NbHsp90.3 as carrier/adjuvant of SAG1-derived peptide (SAG1HC) in a T. gondii infection murine model.

METHODS

In the present study, C57BL/6 mice were intraperitoneal immunized with the NbHsp90.3-SAG1HC fusion protein (NbHsp90.3-SAG1HC group), mature SAG1 (SAG1m group), NbHsp90.3 (NbHsp90.3 group) or PBS buffer 1× (PBS group). The levels of IgG antibodies and the cytokine profile were determined by ELISA. Two weeks after the last immunization, all mice were orally challenged with 20 cysts of T. gondii Me49 strain and the number of brain cysts was determined. In addition, both humoral and cellular immune responses were also evaluated during the acute and chronic phase of T. gondii infection by ELISA.

RESULTS

The characterization of the immune response generated after vaccination with NbHsp90.3 as an adjuvant showed that NbHsp90.3-SAG1HC-immunized mice produced antibodies that were able to recognize not only rSAG1m but also the native SAG1 present in the total lysate antigen extract (SAG1TLA) from T. gondii tachyzoites, while control groups did not. Furthermore, anti-rSAG1m IgG2a/2b antibodies were significantly induced. In addition, only the spleen cell cultures from NbHsp90.3-SAG1HC-immunized mice showed a significantly increased production of IFN-γ. During the chronic phase of T. gondii infection, the antibodies generated by the infection were unable to detect the recombinant protein, but they did react with TLA extract. In addition, splenocytes from all groups showed a high production of IFN-γ when stimulated with rGRA4, but only those from NbHsp90.3-SAG1HC group stimulated with rSAG1m showed high production of IFN-γ. Finally, NbHsp90.3-SAG1HC-immunized mice exhibited a significant reduction in the cyst load (56%) against T. gondii infection.

CONCLUSIONS

We demonstrated that NbHsp90.3 enhances the humoral and cell-mediated immune response through a Th1 type cytokine production. Mice vaccinated with NbHsp90.3-SAG1HC exhibited a partial protection against T. gondii infection and it was correlated with the induction of memory immune response. We developed and validated a vaccine formulation which, to our knowledge, for the first time includes the NbHsp90.3 protein covalently fused to a peptide from T. gondii SAG1 protein that contains T- and B-cell epitopes.

Rhoptry antigens as Toxoplasma gondii vaccine target

Toxoplasmosis is a cosmopolitan zoonotic infection, caused by a unicellular protozoan parasite known as Toxoplasma gondii that belongs to the phylum Apicomplexa. It is estimated that over one-third of the world's population has been exposed and are latently infected with the parasite. In humans, toxoplasmosis is predominantly asymptomatic in immunocompetent persons, while among immunocompromised individuals may be cause severe and progressive complications with poor prognosis. Moreover, seronegative pregnant mothers are other risk groups for acquiring the infection. The life cycle of T. gondii is very complex, indicating the presence of a plurality of antigenic epitopes. Despite of great advances, recognize and construct novel vaccines for prevent and control of toxoplasmosis in both humans and animals is still remains a great challenge for researchers to select potential protein sequences as the ideal antigens. Notably, in several past years, constant efforts of researchers have made considerable advances to elucidate the different aspects of the cell and molecular biology of T. gondii mainly on microneme antigens, dense granule antigens, surface antigens, and rhoptry proteins (ROP). These attempts thereby provided great impetus to the present focus on vaccine development, according to the defined subcellular components of the parasite. Although, currently there is no commercial vaccine for use in humans. Among the main identified T. gondii antigens, ROPs appear as a putative vaccine candidate that are vital for invasion procedure as well as survival within host cells. Overall, it is estimated that they occupy about 1%–30% of the total parasite cell volume. In this review, we have summarized the recent progress of ROP-based vaccine development through various strategies from DNA vaccines, epitope or multi epitope-based vaccines, recombinant protein vaccines to vaccines based on live-attenuated vectors and prime-boost strategies in different mouse models.

A systematic review of Toxoplasma gondii antigens to find the best vaccine candidates for immunization

At present, there is not any available accepted vaccine for prevention of Toxoplasma gondii (T. gondii) in human and animals. We conducted literature search through English (Google Scholar, PubMed, Science Direct, Scopus, EBSCO, ISI Web of Science) scientific paper databases to find the best vaccine candidates against toxoplasmosis among T. gondii antigens. Articles with information on infective stage, pathogenicity, immunogenicity and characterization of antigens were selected. We considered that the ideal and significant vaccines should include different antigens and been expressed in all infective stages of the parasite with a high pathogenicity and immunogenicity. Evaluation within this systematic review indicates that MIC 3, 4, 13, ROP 2, RON 5, GRA 1, 6, 8, 14 are expressed in all three infective stages and have pathogenicity and immunogenicity. MIC 5, ROM 4, GRA 2, 4, 15, ROP 5, 16, 17, 38, RON 4, MIC 1, GRA 10, 12, 16, SAG 3 are expressed in only tachyzoites and bradyzoites stages of T. gondii with pathogenicity/immunogenicity. Some antigens appeared to be expressed in a single stage (tachyzoites) but have high pathogenicity and induce immune response. They include enolase2 (ENO2), SAG 1, SAG5D, HSP 70, ROM 1, ROM 5, AMA 1, ROP 18, RON2 and GRA 24. In conclusion, current vaccination against T. gondii infection is not satisfactory, and with the increasing number of high-risk individuals, the development of an effective and safe specific vaccine is greatly valuable for toxoplasmosis prevention. This systematic review reveals prepare candidates for immunization studies.

Targeted Delivery of Toxoplasma gondii Antigens to Dendritic Cells Promote Immunogenicity and Protective Efficiency against Toxoplasmosis

Toxoplasmosis is a major public health problem and the development of a human vaccine is of high priority. Efficient vaccination against Toxoplasma gondii requires both a mucosal and systemic Th1 immune response. Moreover, dendritic cells play a critical role in orchestrating the innate immune functions and driving specific adaptive immunity to T. gondii. In this study, we explore an original vaccination strategy that combines administration via mucosal and systemic routes of fusion proteins able to target the major T. gondii surface antigen SAG1 to DCs using an antibody fragment single-chain fragment variable (scFv) directed against DEC205 endocytic receptor. Our results show that SAG1 targeting to DCs by scFv via intranasal and subcutaneous administration improved protection against chronic T. gondii infection. A marked reduction in brain parasite burden is observed when compared with the intranasal or the subcutaneous route alone. DC targeting improved both local and systemic humoral and cellular immune responses and potentiated more specifically the Th1 response profile by more efficient production of IFN-γ, interleukin-2, IgG2a, and nasal IgA. This study provides evidence of the potential of DC targeting for the development of new vaccines against a range of Apicomplexa parasites.

Calcium-dependent protein kinases are potential targets for Toxoplasma gondii vaccine

Toxoplasma gondii belongs to the Apicomplexa phylum that caused a widespread zoonotic infection in wide range of intermediate hosts. Over one-third of the world's population are latently infected with T. gondii and carry it. The complex life cycle of T. gondii indicates the presence of a plurality of antigenic epitopes. During the recent years, continuous efforts of scientists have made precious advances to elucidate the different aspects of the cell and molecular biology of T. gondii. Despite of great progresses, the development of vaccine candidates for preventing of T. gondii infection in men and animals is still remains a challenge. The calcium-dependent protein kinases (CDPKs) belongs to the superfamily of kinases, which restricted to the apicomplexans, ciliates, and plants. It has been documented that they contribute several functions in the life cycle of T. gondii such as gliding motility, cell invasion, and egress as well as some other critical developmental processes. In current paper, we reviewed the recent progress concerning the development of CDPK-based vaccines against acute and chronic T. gondii.

DNA Vaccines Encoding Toxoplasma gondii Cathepsin C 1 Induce Protection against Toxoplasmosis in Mice

Toxoplasma gondii cathepsin C proteases (TgCPC1, 2, and 3) are important for the growth and survival of T. gondii. In the present study, B-cell and T-cell epitopes of TgCPC1 were predicted using DNAstar and the Immune Epitope Database. A TgCPC1 DNA vaccine was constructed, and its ability to induce protective immune responses against toxoplasmosis in BALB/c mice was evaluated in the presence or absence of the adjuvant α-GalCer. As results, TgCPC1 DNA vaccine with or without adjuvant α-GalCer showed higher levels of IgG and IgG2a in the serum, as well as IL-2 and IFN-γ in the spleen compared to controls (PBS, pEGFP-C1, and α-Galcer). Upon challenge infection with tachyzoites of T. gondii (RH), pCPC1/α-Galcer immunized mice showed the longest survival among all the groups. Mice vaccinated with DNA vaccine without adjuvant (pCPC1) showed better protective immunity compared to other controls (PBS, pEGFP-C1, and α-Galcer). These results indicate that a DNA vaccine encoding TgCPC1 is a potential vaccine candidate against toxoplasmosis.

How Can Elispot Add Information to Improve Knowledge on Tropical Diseases?

Elispot has been used as an important tool for detecting immune cells' products and functions and has facilitated the understanding of host-pathogen interaction. Despite the incredible diversity of possibilities, two main approaches have been developed: the immunopathogenesis and diagnosis/prognosis of infectious diseases as well as cancer research. Much has been described on the topics of allergy, autoimmune diseases, and HIV-Aids, however, Elispot can also be applied to other infectious diseases, mainly leishmaniasis, malaria, some viruses, helminths and mycosis usually classified as tropical diseases. The comprehension of the function, concentration and diversity of the immune response in the infectious disease is pointed out as crucial to the development of infection or disease in humans and animals. In this review we will describe the knowledge already obtained using Elispot as a method for accessing the profile of immune response as well as the recent advances in information about host-pathogen interaction in order to better understand the clinical outcome of a group of tropical and neglected diseases.