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

https://doi.org/10.1016/j.micpath.2020.104646Get rights and content

Highlights

  • The epitopes of the 10 immunogenic proteins were predicted.

  • A multi-epitope vaccine was developed based on the predicted epitopes.

  • The most important features of the developed vaccine were evaluated .

  • The results showed that the developed vaccine is a proper candidate to apply.

Abstract

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.

Introduction

Toxoplasmosis is a parasitic, zoonotic and prevalent disease which is caused by toxoplasma gondii(T. gondii) [1,2]. T. gondii is known as an obligatory intracellular protozoan belonging to the phylum of Apicomplexa [3]. It has been reported, T. gondii is able to infect a wide variety of warm-blooded creatures including humans, livestock, wild animals and birds [4]. In both human and livestock, toxoplasmosis is known as one of the most important health threats which can cause huge economic damages [5]. In general, life cycle of T. gondii includes asexual and a sexual parts, the asexual cycle can be appeared in most hosts, whereas sexual cycle is mostly observed in cats [6]. Also, this parasite has three replication forms in hosts including; tachyzoites, bradyzoites (tissue cyst) and sporozoites (oocysts) [7], in humans, T. gondii is usually transmitted using consumption of raw foods contaminated with viable tissue cysts [1]. Toxoplasmosis in immunocompetent patients, shows no symptoms, whereas this disease in immunocompromised patients shows intensive symptoms such as nerve problems, eye problems and even death [[8], [9], [10]]. Despite the importance of toxoplasmosis, there is only one approved chemical vaccine (TOXOVAC) to prevent and treat this disease in animals. The reports have shown, application of this vaccine, owing to its severe side effects and low efficacy has been limited [[11], [12], [13]]. Therefore, identification of an effective method to prevent toxoplasmosis is vital for researchers who are studying in this field. So far, different strategies including live attenuated vaccine, inactivated vaccine and subunit vaccine have been employed to prevent toxoplasmosis [14]. Although these strategies have been able to lead to some effective results, it seems prevention of toxoplasmosis needs a more effective strategy. Today, the epitope-based vaccines applying different epitopes instead of whole antigens are suggested to prevent viral and bacterial infections [15]. As matter of fact, these vaccines using stimulation of both humoral and cellular immunities can lead to protective immunity against infections [16]. Consequently, identification and extraction of effective epitopes which can stimulate the immune system, are known as a vital step in designing epitope-based vaccines. Bioinformatics is a fast, precise and affordable science which merges different fields including computer and biology to analyze biological data. Nowadays, many online servers and tools have been generated using the bioinformatics science which can isolate the best MHCI, MHCII and B cell epitopes of antigenic proteins [15]. The current project was designed to engineer a novel poly-epitope vaccine against T. gondii infection. To do so, 10 protective antigens of T. gondii including BiP, GRA1, GRA2, GRA5, MIC8, MIC13, P30, PI1, SOD and Rop2 were extracted from VIOLIN database. Then, the best MHCI, MHCII and B cell epitopes of protective antigens were isolated by the most accurate bioinformatics tools, the predicted epitopes along with heparin-binding hemagglutinin (HBHA) of Mycobacterium tuberculosis (as a molecular adjuvant) were used to engineer a poly-epitope vaccine.

Section snippets

Collection of protein sequences

In the current project, the amino acid sequences of the antigenic proteins were collected from the UniProt database (https://www.uniprot.org/). The accession numbers of BiP, GRA1, GRA2, GRA5, MIC8, MIC13, P30, PI1, SOD and Rop2 antigens were A0A0F7V8D8, P13403, P13404, Q07828, Q9BIM7, B0LUH4, Q27000, B9QKZ5, Q0QWJ4 and Q27007, respectively.

B cell epitope prediction

To predict B cell epitopes of the antigenic proteins, different accurate online tools including IEBD (https://www.iedb.org/), Bcepred (//crdd.osdd.net/raghava/bcepred),%20BepiPred

Epitope prediction

In the current study, the most reliable online tools were applied for isolation of B cell epitopes. According to the results, the peptides including “73 TPSYVAFTDDDRKIGE 88”, “23 YAAEGGDNQSSAVSD 37”, “28 GVVNQGPVDVPFSGKP 43”, “23 GVAGSTRDVGSGGDDS 38”, “179 AGTCTRTDEGYKCDCP 194”, “209 GGEIECPGGRSETSGE 224”, “250 LTENPWQGNASSDKGAT 266”, “189 LNCGVDGVTYDNHCLR 204”, “123 GRTGGSDGGGEPPQTP 138” and “81 MKPPMSGGGGEPTGR 95” were identified as the best B cell epitopes of BiP, GRA1, GRA2, GRA5, MIC8,

Discussion

Nowadays, vaccination is known as one the most efficient medical strategies which has been able to decrease mortality rate in human societies [17]. Despite the importance and success of the conventional vaccination methods such as inactive and attenuated vaccine in prevention of the different diseases, these methods encounter serious limitations [18]. Hence, it seems modern approaches should be considered as substitution of the conventional vaccination methods. Bioinformatics is a part of the

Conclusion

The aim of the current study was designing an efficient poly-epitope vaccine using computational vaccinology. In this case, for the first time, 10 antigenic proteins of T. gondii including BiP, GRA1, GRA2, GRA5, MIC8, MIC13, P30, PI1, Rop2 and SOD were simultaneously applied for prediction of the best B cell, MHCI and MHCII epitopes. Then, to trigger, innate, humoral and cellular immunities, a vaccine was designed which contained HBHA, MHCI, B cell and MHCII segments, respectively. To

Author statement

All aspects of the project were done by Ali Forouharmehr.

Availability of data and materials

All materials and methods and obtained data from present work were reported in the article.

Ethics approval and consent to participate

Not applicable.

Consent of publication

Not applicable.

Funding

Not applicable.

Declaration of competing interest

The authors declare that there is no conflict of interest.

Acknowledgement

The author would like to thank faculty of agriculture of Lorsetan University because providing calm environment to research. The present project was done without funding support.

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