Development of multiplex serological assay for the detection of human African trypanosomiasis

A multifaceted strategy to improve recombinant expression and structural characterisation of a Trypanosoma invariant surface protein

Identification of a protein minimal fragment amenable to crystallisation can be time- and labour intensive especially if large amounts are required and the protein has a complex fold and functionally important post-translational modifications. In addition, a lack of homologues and structural information can further complicate the design of a minimal expression construct. Recombinant expression in E. coli promises high yields, low costs and fast turnover times, but falls short for many extracellular, eukaryotic proteins. Eukaryotic expression systems provide an alternative but are costly, slow and require special handling and equipment. Using a member of a structurally uncharacterized, eukaryotic receptor family as an example we employ hydrogen–deuterium exchange mass spectrometry (HDX-MS) guided construct design in conjunction with truncation scanning and targeted expression host switching to identify a minimal expression construct that can be produced with high yields and moderate costs.

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

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.

Rapid diagnosis of parasitic diseases: current scenario and future needs

BACKGROUND

Parasitic diseases are one of the world's most devastating and prevalent infections, causing millions of morbidities and mortalities annually. In the past, many of these infections have been linked predominantly to tropical or subtropical areas. Nowadays, however, climatic and vector ecology changes, a significant increase in international travel, armed conflicts, and migration of humans and animals have influenced the transmission of some parasitic diseases from 'book pages' to reality in developed countries. It has also been noted that many patients who have never travelled to endemic areas suffer from blood-borne infections caused by protozoa. In the light of existing knowledge, this new trend can be explained by the fact that in the process of migration a large number of asymptomatic carriers become a part of the blood bank donor and transplant donor populations. Accurate and rapid diagnosis represents the crucial weapon in the fight against parasitic infections.

AIMS

To review old and new approaches for rapid diagnosis of parasitic infections.

SOURCES

Data for this review were obtained through searches of PubMed using combinations of the following terms: parasitological diagnostics, microscopy, lateral flow assays, immunochromatographic assays, multiplex-PCR, and transplantation.

CONTENT

In this review, we provide a brief account of the advantages and limitations of rapid methods for diagnosis of parasitic diseases and focus our attention on current and future research in this area. The approximate costs associated with the use of different techniques and their applicability in endemic and non-endemic areas are also discussed.

IMPLICATIONS

Microscopy remains the cornerstone of parasitological diagnostics, especially in the field and low-resource settings, and provides epidemiological assessment of parasite burden. However, increased use and availability of point-of-care tests and molecular assays in modern era allow more rapid and accurate diagnoses and increased sensitivity in the identification of parasitic infections.

Detection of Natural Antibodies and Serological Diagnosis of Pneumococcal Pneumonia Using a Bead-Based High-Throughput Assay

Surface-exposed proteins of pathogenic bacteria play a critical role during infections . The vast majority of these molecules are able to trigger strong immune responses. Measuring the humoral immune response against pathogenic bacteria through less-time consuming tests is necessary to reduce the window time for the diagnosis of diseases that may be associated with high morbidity and mortality rates. Due to the multiplex setup, Luminex xMAP^® technology allows analysis of immune responses against many antigens in a single assay. Therefore, less volumes of sera samples are needed and inter assay coefficient of variation is much lower in comparison with other immunoassays. With this methodology, the carboxyl groups on the surface of the polystyrene microspheres must first be activated with a carbodiimide derivative prior to coupling antigens . After the antigen is coupled to a microsphere , different microspheres (all having a unique color) can be combined whereafter the presence of specific antibodies directed against the different antigens in sera can be determined simultaneously. The platform here described can also be useful for epidemiological surveillance programs and vaccine studies.

Evaluation of Antigens for Development of a Serological Test for Human African Trypanosomiasis

Background

Control and elimination of human African trypanosomiasis (HAT) can be accelerated through the use of diagnostic tests that are more accurate and easier to deploy. The goal of this work was to evaluate the immuno-reactivity of antigens and identify candidates to be considered for development of a simple serological test for the detection of Trypanosoma brucei gambiense or T. b. rhodesiense infections, ideally both.

Methodology/Principal Findings

The reactivity of 35 antigens was independently evaluated by slot blot and ELISA against sera from both T. b. gambiense and T. b. rhodesiense infected patients and controls. The antigens that were most reactive by both tests to T. b. gambiense sera were the membrane proteins VSG LiTat 1.3, VSG LiTat 1.5 and ISG64. Reactivity to T. b. rhodesiense sera was highest with VSG LiTat 1.3, VSG LiTat 1.5 and SRA, although much lower than with T. b. gambiense samples. The reactivity of all possible combinations of antigens was also calculated. When the slot blot results of 2 antigens were paired, a VSG LiTat 1.3- ISG75 combination performed best on T. b. gambiense sera, while a VSG LiTat 1.3-VSG LiTat 1.5 combination was the most reactive using ELISA. A combination of SRA and either VSG LiTat 1.3 or VSG LiTat 1.5 had the highest reactivity on T. b. rhodesiense sera according to slot blot, while in ELISA, pairing SRA with either GM6 or VSG LiTat 1.3 yielded the best results.

Conclusions

This study identified antigens that were highly reactive to T. b. gambiense sera, which could be considered for developing a serological test for gambiense HAT, either individually or in combination. Antigens with potential for inclusion in a test for T. b. rhodesiense HAT were also identified, but because their reactivity was comparatively lower, a search for additional antigens would be required before developing a test for this form of the disease.