In Silico Identification of a Candidate Synthetic Peptide (Tsgf118–43) to Monitor Human Exposure to Tsetse Flies in West Africa

Abstract

BackgroundThe analysis of humoral responses directed against the saliva of blood-sucking arthropods was shown to provide epidemiological biomarkers of human exposure to vector-borne diseases. However, the use of whole saliva as antigen presents several limitations such as problems of mass production, reproducibility and specificity. The aim of this study was to design a specific biomarker of exposure to tsetse flies based on the in silico analysis of three Glossina salivary proteins (Ada, Ag5 and Tsgf1) previously shown to be specifically recognized by plasma from exposed individuals.Methodology/Principal FindingsSynthetic peptides were designed by combining several linear epitope prediction methods and Blast analysis. The most specific peptides were then tested by indirect ELISA on a bank of 160 plasma samples from tsetse infested areas and tsetse free areas. Anti-Tsgf118–43 specific IgG levels were low in all three control populations (from rural Africa, urban Africa and Europe) and were significantly higher (p<0.0001) in the two populations exposed to tsetse flies (Guinean HAT foci, and South West Burkina Faso). A positive correlation was also found between Anti-Tsgf118–43 IgG levels and the risk of being infected by Trypanosoma brucei gambiense in the sleeping sickness foci of Guinea.Conclusion/SignificanceThe Tsgf118–43 peptide is a suitable and promising candidate to develop a standardize immunoassay allowing large scale monitoring of human exposure to tsetse flies in West Africa. This could provide a new surveillance indicator for tsetse control interventions by HAT control programs.

Serological Responses and Biomarker Evaluation in Mice and Pigs Exposed to Tsetse Fly Bites

“…Similar results were obtained with a peptide derived from the adenosine deaminase-related protein TSGF1, although obtained ELISA signals seemed very low [21]. In both the cattle and human ELISA tests, large inter-individual differences were observed [15], [19], [20], [21]. It should be noted that in our study the individual variation in antibody titers in the different exposure groups also varied significantly.…”

Description of a Nanobody-based Competitive Immunoassay to Detect Tsetse Fly Exposure

“…The concept of exploiting salivary components as specific biomarkers of exposure of vertebrate host to bites of medically important arthropods has been proposed for a number of species of sand flies [ 24 – 26 ], triatomine bugs [ 27 , 28 ], mosquitoes [ 29 – 31 ] and also tsetse flies [ 7 , 8 , 10 – 12 , 17 , 18 ]. The main added value of such approach is that relatively simple serological tests could indicate actual exposure to the bites of disease vectors without the requirement of conducting strenuous entomological surveys.…”

“…morsitans saliva are suitable antigenic targets for specific pan-tsetse species exposure detection. Moreover, the detection of responses against a specific diagnostic epitope on the Tsal proteins in the competitive assay strongly reduces the possibility of unspecific reactions, a principle that is also aimed at by immunoassays that use synthetic peptides [ 17 ]. The use of total saliva as crude antigen in this assay might be a drawback for two main reasons: ( i ) the production and ( ii ) possible issues with specificity.…”

“…morsitans salivary gland proteins sgp1 , sgp2 and sgp3 [ 16 ]. A number of potential candidates were proposed as individual exposure biomarkers in the form of recombinant proteins or peptides corresponding to predicted B cell epitopes [ 17 , 18 ]. The TSGF1 18–43 peptide was shown in West Africa to detect human antibody levels that correlated with the anticipated levels of tsetse exposure [ 17 ].…”

“…A number of potential candidates were proposed as individual exposure biomarkers in the form of recombinant proteins or peptides corresponding to predicted B cell epitopes [ 17 , 18 ]. The TSGF1 18–43 peptide was shown in West Africa to detect human antibody levels that correlated with the anticipated levels of tsetse exposure [ 17 ]. Especially the 43–45 kDa tsetse salivary gland (Tsal) protein family, encoded by 3 tsal genes that colocalize to a 10-kb locus in the tsetse fly genome [ 19 ], was found to be highly immunogenic with immunoglobulin responses detected in humans living in Uganda [ 7 ], Democratic Republic of Congo [ 10 ] and Guinea [ 8 ].…”