Induction of protective T-helper 1 immune responses against Echinococcus granulosus in mice by a multi-T-cell epitope antigen based on five proteins

Identification of B‐cell dominant epitopes in the recombinant protein P29 from Echinococcus granulosus

Introduction

Echinococcus granulosus (E. granulosus) causes a hazardous zoonotic parasitic disease. This parasite can occupy the liver and several areas of the body, causing incurable damage. Our previous studies have provided evidence that the recombinant protein P29 (rEg.P29) exhibit immune protection in sheep and mice against pathological damage induced by E. granulosus, showing its potential as candidate for vaccine development. However, information on the B‐cell epitopes of rEg.P29 has not yet been reported.

Methods

Immunological model was established in mice with rEg.P29. SDS‐PAGE and Western blot were used to identify protein. Screening for B‐cell dominant epitope peptides of rEg.P29 by enzyme‐linked immunosorbent assay (ELISA) and immune serum. Dominant epitopes were validated using ELISA and flow cytometry. Multiple sequence alignment analysis was performed using BLAST and UniProt.

Results

Immunization with rEg.P29 induced intense and persistent antibody responses, and the epitope of the dominant antigen of B cells are identified as rEg.P29_166–185 (LKNAKTAEQKAKWEAEVRKD). Anti‐rEg.P29_166–185‐specific antibodies lack epitopes against IgA, IgE, and IgG3, compared to anti‐rEg.P29‐specific antibodies. However, anti‐rEg.P29_166–185 IgG showed comparatively higher titers, as determined among those peptides by endpoint titration. In addition, rEg.P29 and rEg.P29_166–185 promote B‐cell activation and proliferation in vitro. The dominant epitopes are relatively conserved in different subtypes of the rEg.P29 sequence.

Conclusion

rEg.P29_166–185 can act as a dominant B‐cell epitope for rEg.P29 and promote cell activation and proliferation in the same way as rEg.P29.

An Overview of Current Uses and Future Opportunities for Computer-Assisted Design of Vaccines for Neglected Tropical Diseases

Neglected tropical diseases are infectious diseases that impose high morbidity and mortality rates over 1.5 billion people worldwide. Originally restricted to tropical and subtropical regions, changing climate conditions have increased their potential to emerge elsewhere. Control of their impact suffers from shortages like poor epidemiological surveillance or irregular drug distribution, and some NTDs still lack of appropriate diagnostics and/or efficient therapeutics. For these, availability of vaccines to prevent new infections, or the worsening of those already established, would mean a major breakthrough. However, only dengue and rabies count with approved vaccines at present. Herein, we review the state-of-the-art of vaccination strategies for NTDs, setting the focus on third generation vaccines and the concept of reverse vaccinology. Its capability to address pathogens´ biological complexity, likely contributing to save developmental costs is discussed. The use of computational tools is a fundamental aid to analyze increasingly large datasets aimed at designing vaccine candidates with the highest, possibly, opportunities to succeed. Ultimately, we identify and analyze those studies that took an in silico approach to find vaccine candidates, and experimentally assessed their immunogenicity and/or protection capabilities.

Prediction and Identification of Epitopes in the Emy162 Antigen of Echinococcus multilocularis

INTRODUCTION

Alveolar echinococcosis (AE) is a zoonotic disease caused by the parasitism of Echinococcus multilocularis larvae in the intermediate host or the final host. This study aims to identify and analyze the B-cell and T-cell (Th1, Th2 and Th17) epitopes of E. multilocularis antigen Emy162.

METHODS

(1) The secondary structural characteristics of the Emy162 protein were predicted by bioinformatics software to further predict the potential T- and B-cell epitopes. (2) The dominant antigen epitopes were detected by ELISA through the reaction of patient serum with small B-cell antigen peptide and assessing the proliferation of splenic lymphocytes of mice immunized with Emy162. (3) The expression of cytokines in splenic lymphocytes of mice stimulated by small T-cell antigen peptides was detected by ELISA, ELISpot and flow cytometry to enable the identification of the T-cell epitopes.

RESULTS

(1) The high-scored T-cell epitopes were located at positions E7-13, E36-41, E80-89, E87-96, E97-106 and E129-139, while B-cell epitopes were located at positions E7-13, E19-27, E28-36, E37-48, E78-83, E101-109, E112-121 and E129-139. (2) The three advanced antigen epitopes of Emy162 were E19-27, E112-121 and E129-139. (3) The four Th1 advanced antigen epitopes of Emy162 were E7-13, E36-41, E80-89 and E129-139. The three Th2 advanced antigen epitopes were E36-41, E87-96 and E97-106. The three Th17 advanced antigen epitopes were E36-41, E87-96 and E97-106.

CONCLUSION

(1) The Emy162 protein has advanced antigenicity and numerous potential epitopes. Six T-cell and eight B-cell dominant epitopes were revealed using bioinformatics methods. (2) There are three dominant B-cell epitopes, four dominant Th1 epitopes, three dominant Th2 epitopes, and three dominant Th17 epitopes in the Emy162 antigen.

Taenia solium glutathione transferase fraction activates macrophages and favors the development of Th1-type response

Glutathione (GSH) transferase (GST) is an essential enzyme in cestodes for the detoxification of xenobiotics. In Taenia solium, two GSTs (Ts25GST and Ts26GST kDa) were isolated as a fraction (SGSTF) by GSH-Sepharose-4B. Both are located on the tegument. Immunization assays with SGSTF reduced up to 90% of the parasitic load in a murine model of cysticercosis. It prompted us to investigate how SGSTF induces this protective immune response. To test it, we exposed peritoneal macrophages to SGSTF for 24 h; such exposure favored the production of IL-12, TNF, and IL-10 as well as the expression of nitric oxide synthase 2 inducible (Nos2) and CD86, but did not induce the expression of chitinase-like 3 (Chil3). Confocal microscopy showed that the macrophages internalize the SGSTF which co-localized after 1 h with MHC-II in their plasma membranes. Macrophages exposed to SGSTF and co-cultured with anti-CD3 pre-activated T CD4⁺ cells, enhanced the proliferation of CD4⁺ cells, induced high interferon-γ (IFN-γ) secretion, and elevated the expression of CD25 and CD69, molecules associated with cell activation. Similar assay using T CD4⁺ cells from DO11.10 mice and ovalbumin (OVA) peptide+SGSTF as stimuli, showed enhanced cell proliferation and OVA-specific IFN-γ secretion. These data are in-line with those indicating that the P1, P5, and P6 peptides of Schistosoma japonicum 28GST highly promote T-cell proliferation and Th1 response in vitro. We found that such peptides are also present on Ts25GST and Ts26GST. It suggests that SGSTF activates peritoneal macrophages to a classically activated-like phenotype, and that these macrophages induce the differentiation of T CD4⁺ cells toward a Th1-type response.

Immunization of sheep against Echinococcus granulosus with protoscolex tegumental surface antigens

AIM

Cystic echinococcosis (CE) has potential economic effects to both animal products and human health. A vaccine to protect livestock against CE can be effective in reducing economic costs and increasing the livestock products. Protoscolex tegumental surface antigens (PSTSA) used to induce the production of specific antibodies against Echinococcus granulosus in sheep. The tegumental antigens were extracted from viable protoscolices by solubilization in sterile phosphate-buffered saline containing decanoyl-N-methylglucamine.

MATERIALS AND METHODS

Ten lambs which were infected with CE (positive control), 10 negative control, and 10 test groups of sheep were included in the study. 300 µg emulsion of purified-PSTSA was injected intramuscularly in a two-step immunization on the first and 30 days. Sera were collected immediately before immunization and 6 times with 10-day intervals until 60 days post immunization. Thereafter, the sera were tested for antibodies by indirect hemagglutination test in microtiter plate.

RESULTS

After two immunizations, all the infected animals in test group showed substantial increases in antibody titer. Statistical analysis showed a significant difference between the titer obtained in the test and negative control groups in both phases of immunization (p<0.05).

CONCLUSION

The results showed that the PSTSA is a promising immunogenic compound for immunization of sheep against CE.

Immunology of Alveolar and Cystic Echinococcosis (AE and CE)

Cystic and alveolar echinococcosis are severe chronic helminthic diseases caused by the cystic growth or the intrahepatic tumour-like growth of the metacestode of Echinococcus granulosus or Echinococcus multilocularis, respectively. Both parasites have evolved sophisticated strategies to escape host immune responses, mainly by manipulating and directing this immune response towards anergy and/or tolerance. Recent research studies have revealed a number of respective immunoregulatory mechanisms related to macrophages and dendritic cell as well as T cell activities (regulatory T cells, Tregs). A better understanding of this complex parasite-host relationship, and the elucidation of specific crucial events that lead to disease, represents targets towards the development of novel treatment strategies and options.