Serological responses and biomarker evaluation in mice and pigs exposed to tsetse fly bites.
BACKGROUND
Tsetse flies are obligate blood-feeding insects that transmit African trypanosomes responsible for human sleeping sickness and nagana in livestock. The tsetse salivary proteome contains a highly immunogenic family of the endonuclease-like Tsal proteins. In this study, a recombinant version of Tsal1 (rTsal1) was evaluated in an indirect ELISA to quantify the contact with total Glossina morsitans morsitans saliva, and thus the tsetse fly bite exposure.


RESULTS
Mice and pigs were experimentally exposed to different G. m. morsitans exposure regimens, followed by a long-term follow-up of the specific antibody responses against total tsetse fly saliva and rTsal1. In mice, a single tsetse fly bite was sufficient to induce detectable IgG antibody responses with an estimated half-life of 36-40 days. Specific antibody responses could be detected for more than a year after initial exposure, and a single bite was sufficient to boost anti-saliva immunity. Also, plasmas collected from tsetse-exposed pigs displayed increased anti-rTsal1 and anti-saliva IgG levels that correlated with the exposure intensity. A strong correlation between the detection of anti-rTsal1 and anti-saliva responses was recorded. The ELISA test performance and intra-laboratory repeatability was adequate in the two tested animal models. Cross-reactivity of the mouse IgGs induced by exposure to different Glossina species (G. m. morsitans, G. pallidipes, G. palpalis gambiensis and G. fuscipes) and other hematophagous insects (Stomoxys calcitrans and Tabanus yao) was evaluated.


CONCLUSIONS
This study illustrates the potential use of rTsal1 from G. m. morsitans as a sensitive biomarker of exposure to a broad range of Glossina species. We propose that the detection of anti-rTsal1 IgGs could be a promising serological indicator of tsetse fly presence that will be a valuable tool to monitor the impact of tsetse control efforts on the African continent.
Unit of Veterinary Protozoology, Department of Biomedical Sciences, Institute of Tropical Medicine Antwerp (ITM), Antwerp, Belgium; Unit of Cellular and Molecular Immunology, Vrije Universiteit Brussel (VUB), Brussels, Belgium; Laboratory of Myeloid Cell Immunology, Vlaams Instituut voor Biotechnologie (VIB), Brussels, Belgium.
Guy
G
Caljon
Faculty of Veterinary Medicine, Addis Ababa University, Debre Zeit, Ethiopia.
Reta
R
Duguma
Unit Veterinary Entomology, Department of Biomedical Sciences, Institute of Tropical Medicine Antwerp (ITM), Antwerp, Belgium.
Reginald
R
De Deken
Department of Surgery and Anaesthesia of Domestic Animals, Faculty of Veterinary Medicine, Ghent University (UGent), Ghent, Belgium.
Stijn
S
Schauvliege
Department of Surgery and Anaesthesia of Domestic Animals, Faculty of Veterinary Medicine, Ghent University (UGent), Ghent, Belgium.
Frank
F
Gasthuys
Department of Comparative Physiology and Biometrics, Faculty of Veterinary Medicine, Ghent University (UGent), Ghent, Belgium.
Luc
L
Duchateau
Unit of Veterinary Protozoology, Department of Biomedical Sciences, Institute of Tropical Medicine Antwerp (ITM), Antwerp, Belgium; Laboratory of Zoophysiology, Department of Physiology, Ghent University (UGent), Ghent, Belgium.
Jan
J
Van Den Abbeele
D000818:Animals; D015415:Biomarkers / Q000097:blood; D001733:Bites and Stings / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D007074:Immunoglobulin G / Q000097:blood*; D019476:Insect Proteins / Q000097:blood* / Q000276:immunology; D051379:Mice; D011994:Recombinant Proteins / Q000276:immunology; D012463:Saliva / Q000276:immunology; D013552:Swine; D014370:Tsetse Flies
D015415:Biomarkers; D007074:Immunoglobulin G; D019476:Insect Proteins; D011994:Recombinant Proteins; C428613:Tsal1 protein, Glossina morsitans morsitans