Development of a microsphere-based immunoassay for the serological diagnosis of equine trypanosomosis

Mylène Verney,Morgane Gautron,Aymeric Hans,Alain Rincé,Charlène Lemans,Laurent Hébert

doi:10.1038/s41598-022-05356-y

Mylène Verney, Morgane Gautron + Show 4 more

Open Access

https://doi.org/10.1038/s41598-022-05356-y

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Abstract

Trypanozoon infections in equids are caused by three parasite species in the Trypanozoon subgenus: Trypanosoma equiperdum, T. brucei and T. evansi. They are respectively responsible for infectious diseases dourine, nagana and surra. Due to the threat that Trypanozoon infection represents for international horse trading, accurate diagnostic tests are crucial. Current tests suffer from poor sensitivity and specificity, due in the first case to the transient presence of parasites in the blood and in the second, to antigenic cross-reactivity among Trypanozoon subspecies. This study was designed to develop a microsphere‐based immunoassay for diagnosing equine trypanosomosis. We tested beads coated with eight Trypanosoma spp. recombinant antigens: enolase, GM6, PFR1, PFR2, ISG65, VSGat, RoTat1.2 and JN2118HU. Of these, GM6 was identified as the best candidate for the serological diagnosis of Trypanozoon infections in equids. Using a receiver operating characteristic (ROC) analysis on 349 equine sera, anti-GM6 antibodies were detected with an AUC value of 0.994 offering a sensitivity of 97.9% and a specificity of 96.0%. Our findings show that the GM6 antigen is a good target for diagnosing equine trypanosomosis using a microsphere‐based immunoassay. This promising assay could be a useful alternative to the official diagnostic tool for equine trypanosomosis.

Highlights

Trypanozoon infections in equids are caused by three parasite species in the Trypanozoon subgenus: Trypanosoma equiperdum, T. brucei and T. evansi
Five out of eight antigens were common to the Trypanozoon subspecies: i) enolase (XP_822542), found in the secretome of trypanosomes and reactive to nanobodies; ii) GM6 (Tbg972.11.1200), a flagellar associated protein; iii) PFR1 (XP_844021.1) and iv) PFR2 (ACP74157.1), both involved in the paraflagellar rod structure; and v) the invariant surface glycoprotein ISG65 (XP_011771746), found in the antigen coat of Trypanozoon parasites
In order to potentially differentiate between Trypanozoon infections, three variable surface glycoproteins (VSGs) described as specific to one clade were included in the study: the RoTat1.2 VSG (AEL79575.1) specific to T. evansi type A, the JN21118HU VSG (AJ870487) specific to T. evansi type B and an atypical VSG (VSGat-SCU70408) described as specific to T. equiperdum parasites without detailing whether it is specific to T. equiperdum type BoTat or T. equiperdum type Onderstepoort Veterinary Institute (OVI) clades

Summary

Introduction

Trypanozoon infections in equids are caused by three parasite species in the Trypanozoon subgenus: Trypanosoma equiperdum, T. brucei and T. evansi They are respectively responsible for infectious diseases dourine, nagana and surra. Equids have important socioeconomic roles either for their agricultural production, transport and traction activities, or for equestrian businesses with international exchanges including sales, reproduction and sporting events[2] In this context, it is necessary to prevent the spread of equine infectious diseases to maintain horse trading worldwide[3,4,5]. They share a similar course of infection, with non-pathognomonic clinical s igns[6] Their main causative agents are parasites of the Trypanozoon subgenus, including Trypanosoma (T.) brucei for nagana, T. equiperdum for dourine and T. evansi for s urra[6]. Our results showed that detecting anti-GM6 antibodies using xMAP® technology is a suitably sensitive and specific diagnostic tool for Trypanozoon infections in equids

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