Genetic diversity and phylogenetic analysis of EG95 sequences of Echinococcus granulosus: Implications for EG95 vaccine application

Wei Pan; De-Sheng Chen; Yun-Juan Lu; Hui-Wen Xu; Wen-Ting Hao; Ya-Wen Zhang; Su-Ping Qin; Kui-Yang Zheng; Ren-Xian Tang

doi:10.1016/j.apjtm.2017.05.011

Genetic diversity and phylogenetic analysis of EG95 sequences of Echinococcus granulosus: Implications for EG95 vaccine application

Asian Pac J Trop Med. 2017 May;10(5):524-527. doi: 10.1016/j.apjtm.2017.05.011. Epub 2017 May 18.

Authors

Wei Pan¹, De-Sheng Chen², Yun-Juan Lu², Hui-Wen Xu², Wen-Ting Hao¹, Ya-Wen Zhang², Su-Ping Qin¹, Kui-Yang Zheng¹, Ren-Xian Tang³

Affiliations

¹ Jiangsu Key Laboratory of Immunity and Metabolism, Department of Pathogenic Biology and Immunology, Laboratory of Infection and Immunity, Xuzhou Medical University, Xuzhou, Jiangsu Province, 221004, PR China.
² Jiangsu Key Laboratory of Immunity and Metabolism, Department of Pathogenic Biology and Immunology, Laboratory of Infection and Immunity, Xuzhou Medical University, Xuzhou, Jiangsu Province, 221004, PR China; Department of Clinical Medicine, Xuzhou Medical University, Xuzhou, Jiangsu Province, 221004, PR China.
³ Jiangsu Key Laboratory of Immunity and Metabolism, Department of Pathogenic Biology and Immunology, Laboratory of Infection and Immunity, Xuzhou Medical University, Xuzhou, Jiangsu Province, 221004, PR China. Electronic address: Tangrenxian-t@163.com.

PMID: 28647192
DOI: 10.1016/j.apjtm.2017.05.011

Abstract

Objective: To analyse the genetic variability of EG95 sequences and provide guidance for EG95 vaccine application against Echinococcus granulosus (E. granulosus).

Methods: We analysed EG95 polymorphism by collecting total 97 different E. granulosus isolates from 12 different host species that originated from 10 different countries. Multiple sequence alignments and the homology were performed by Lasergene 1 (DNASTAR Inc., Madison, WI), and the phylogenetic analysis was performed by using MEGA5.1 (CEMI, Tempe, AZ, USA). In addition, linear and conformational epitopes were analysed, including secondary structure, NXT/S glycosylation, fibronectin type III (FnIII) domain and glycosylphosphatidylinositol anchor signal (GPI-anchor). The secondary structure was predicted by PSIPRED method.

Results: Our results indicated that most isolates overall shared 72.6-100% identity in EG95 gene sequence with the published standard EG95 sequence, X90928. However, EG95 gene indeed has polymorphism in different isolates. Phylogenetic analysis showed that different isolates could be divided into three subgroups. Subgroup 1 contained 87 isolates while Subgroup 2 and Subgroup 3 consisted of 3 and 7 isolates, respectively. Four sequences cloned from oncosphere shared a high identity with the parental sequence of the current vaccine, X90928, and they belonged to Subgroup 1. However, in comparison to X90928, several amino acid mutations occurred in most isolates besides oncosphere, which potentially altered the immunodominant linear epitopes, glycosylation sites and secondary structures in EG95 genes. All these variations might change their previous antigenicity and thereby affecting the efficacy of current EG95 vaccine.

Conclusions: This study reveals the genetic variability of EG95 sequences in different E. granulosus isolates, and proposed that more vaccination trials would be needed to test the effectiveness of current EG95 vaccine against distinct isolates in different countries.

Keywords: Cystic echinococcosis; EG95; Echinococcus granulosus; Genetic diversity; Vaccine.