Molecular characterization and expression analysis of annexin B3 and B38 as secretory proteins in Echinococcus granulosus

Hongyu Song,Yue Xie,Ran He,Xiaobin Gu,Xue He,Xiaodi Du,Guangyou Yang,Jing Xu,Xuerong Peng,Ruiqi Hua

doi:10.1186/s13071-021-04596-7

Abstract

BackgroundCystic echinococcosis is a parasitic zoonotic disease, which poses a threat to public health and animal husbandry, and causes significant economic losses. Annexins are a family of phospholipid-binding proteins with calcium ion-binding activity, which have many functions.MethodsTwo annexin protein family genes [Echinococcus granulosus annexin B3 (EgAnxB3) and EgAnxB38] were cloned and molecularly characterized using bioinformatic analysis. The immunoreactivity of recombinant EgAnxB3 (rEgAnxB3) and rEgAnxB38 was investigated using western blotting. The distribution of EgAnxB3 and EgAnxB38 in protoscoleces (PSCs), the germinal layer, 18-day strobilated worms and 45-day adult worms was analyzed by immunofluorescence localization, and their secretory characteristics were analyzed preliminarily; in addition, quantitative real-time reverse transcription polymerase chain reaction was used to analyze their transcript levels in PSCs and 28-day strobilated worms stages. The phospholipid-binding activities of rEgAnxB3 and rEgAnxB38 were also analyzed.ResultsEgAnxB3 and EgAnxB38 are conserved and contain calcium-binding sites. Both rEgAnxB3 and rEgAnxB38 could be specifically recognized by the serum samples from E. granulosus-infected sheep, indicating that they had strong immunoreactivity. EgAnxB3 and EgAnxB38 were distributed in all stages of E. granulosus, and their transcript levels were high in the 28-day strobilated worms. They were found in liver tissues near the cysts. In addition, rEgAnxB3 has Ca2+-dependent phospholipid-binding properties.ConclusionsEgAnxB3 and EgAnxB38 contain calcium-binding sites, and rEgAnxB3 has Ca2+-dependent phospholipid-binding properties. EgAnxB3 and EgAnxB38 were transcribed in PSCs and 28-day strobilated worms. They were expressed in all stages of E. granulosus, and distributed in the liver tissues near the hydatid cyst, indicating that they are secreted proteins that play a crucial role in the development of E. granulosus.Graphical

Highlights

Cystic echinococcosis is a parasitic zoonotic disease, which poses a threat to public health and animal husbandry, and causes significant economic losses
We found that EgAnxB3 had high similarity with T. solium annexin B3 via sequence alignment, so we named it “EgAnxB3.”
The parasite communicates with the host through the tegument, and molecules distributed in the tegument participate in the host-parasite interaction, which includes excretion, nutrient absorption, and interaction with the host immune system [37, 38]. Both EgAnxB3 and EgAnxB38 were found to be located in the tegument and parenchyma of immature and gravid proglottids on the basis of immunofluorescence localization analysis, but EgAnxB38 had a wider distribution and stronger fluorescence intensity. These results indicate that both these proteins might have a paramount role in the process of PSC invasion of the definitive host and development of the parasite, but that EgAnxB38 may possibly play a larger role than EgAnxB3 in this process

Summary

Introduction

Cystic echinococcosis is a parasitic zoonotic disease, which poses a threat to public health and animal husbandry, and causes significant economic losses. Annexins are a family of phospholipid-binding proteins with calcium ion-binding activity, which have many functions. CE seriously threatens public health and impedes the development of animal husbandry, resulting in approximately US $ 3 billion losses to the livestock. Song et al Parasites Vectors (2021) 14:103 industry each year [3]. It has been listed as one of the neglected tropical diseases by the World Health Organization [4, 5]. Annexins are a family of phospholipid-binding proteins with calcium ionbinding activity, which function in calcium signaling, and are widely distributed in eukaryotic cells [9]. Annexins have multiple functions, such as cell anti-inflammatory activity, membrane repair and membrane transport, and probably participate in cell proliferation, differentiation, and apoptosis [11,12,13,14,15]

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