Expression analysis and biological characterization of Babesia sp. BQ1 (Lintan) (Babesia motasi-like) rhoptry-associated protein 1 and its potential use in serodiagnosis via ELISA.

Qingli Niu,Emmanuelle Moreau,Peifa Yu,Zhijie Liu,Yuping Pan,Bintao Zhai,Guiquan Guan,Jifei Yang,Hong Yin,Jianxun Luo

doi:10.1186/s13071-016-1573-7

Qingli Niu, Emmanuelle Moreau + Show 8 more

Open Access

https://doi.org/10.1186/s13071-016-1573-7

Copy DOI

Abstract

BackgroundIn China, ovine babesiosis is one of the most important tick-borne haemoparasitic diseases of small ruminants. It has a significant economic impact, and several Babesia motasi-like isolates have been recently shown to be responsible for ovine babesiosis in this country.MethodsFull-length and C-terminal-truncated forms of the rap-1a61-1 gene of Babesia sp. BQ1 (Lintan) were cloned into the pET-30a plasmid and subsequently expressed as His-fusion proteins. The resulting recombinant RAP-1a proteins (rRAP-1a61-1 and rRAP-1a61-1/CT) were purified and evaluated as diagnostic antigens using Western blot analysis and ELISA. The native Babesia sp. BQ1 (Lintan) RAP-1 protein was recognized using Western blots and IFAT by antibodies that were raised in rabbits against rRAP-1a61-1/CT. The specificity, sensitivity and positive threshold values for rRAP-1a61-1/CT in ELISA were evaluated.ResultsCross-reactivity was observed between rRAP-1a61-1/CT and positive sera for Babesia sp. BQ1 (Lintan), Babesia sp. BQ1 (Ningxian) and Babesia sp. Tianzhu isolates obtained from infected sheep. At one week post-inoculation, a significant increase was observed in the amount of antibodies produced against RAP-1a, and high levels of antibodies against RAP-1a were observed for 3 months (at 84 days p.i.). A total of 3198 serum samples were collected from small ruminants in 54 different regions in 23 provinces of China. These samples were tested using ELISA based on the rRAP-1a61-1/CT protein. The results indicated that the average positive rate was 36.02 %.ConclusionsThe present study suggests that rRAP-1a61-1/CT might be a potential diagnostic antigen for detecting several isolates of B. motasi-like parasites infection.

Highlights

In China, ovine babesiosis is one of the most important tick-borne haemoparasitic diseases of small ruminants
A phylogenetic tree based on the sequence of the 18S rRNA gene showed that Babesia species belonging to the following four groups are responsible for babesiosis in small ruminants: B. ovis, B. motasi which are a European and a Chinese clade (B. motasi-like), and the Babesia sp
The results indicated that cross-reactivity was observed only between three B. motasi-like isolates (Lintan, Tianzhu and Ningxian) and that no cross-reactivity was observed with the sera against Babesia sp

Summary

Introduction

In China, ovine babesiosis is one of the most important tick-borne haemoparasitic diseases of small ruminants. It has a significant economic impact, and several Babesia motasi-like isolates have been recently shown to be responsible for ovine babesiosis in this country. Liaoning) have been recently reported in the Gansu, Hebei and Liaoning provinces of China. These isolates can be classified into one or more sub-groups according to their phylogenetic relationships, which have been reconstructed based on several (18S rRNA, ITS, 28S, rap-1) phylogenetic markers [7,8,9,10,11,12]

Methods

Results

Discussion

Conclusion