Caljon Guy, Duguma Reta, De Deken Reginald, Schauvliege Stijn, Gasthuys Frank, Duchateau Luc, Van Den Abbeele Jan
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.
Faculty of Veterinary Medicine, Addis Ababa University, Debre Zeit, Ethiopia.
PLoS Negl Trop Dis. 2014 May 22;8(5):e2911. doi: 10.1371/journal.pntd.0002911. eCollection 2014 May.
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.
METHODOLOGY/PRINCIPAL FINDINGS: 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.
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.
采采蝇是专性吸血昆虫，可传播导致人类昏睡病和家畜那加那病的非洲锥虫。采采蝇唾液蛋白质组包含一个具有高度免疫原性的类核酸内切酶Tsal蛋白家族。在本研究中，对重组Tsal1（rTsal1）进行了间接酶联免疫吸附测定（ELISA）评估，以量化与冈比亚采采蝇总唾液的接触情况，从而确定采采蝇叮咬暴露程度。
方法/主要发现：将小鼠和猪通过实验暴露于不同的冈比亚采采蝇暴露方案，随后对针对采采蝇总唾液和rTsal1的特异性抗体反应进行长期随访。在小鼠中，单次采采蝇叮咬足以诱导可检测到的IgG抗体反应，估计半衰期为36 - 40天。初次暴露后一年多仍可检测到特异性抗体反应，单次叮咬足以增强抗唾液免疫。此外，从暴露于采采蝇的猪身上采集的血浆显示抗rTsal1和抗唾液IgG水平升高，且与暴露强度相关。记录到抗rTsal1和抗唾液反应检测之间存在强相关性。ELISA检测性能和实验室内重复性在两种测试动物模型中均足够。评估了暴露于不同采采蝇物种（冈比亚采采蝇、淡黄采采蝇、冈比亚须舌蝇和fuscipes采采蝇）以及其他吸血昆虫（厩螫蝇和yao虻）诱导的小鼠IgG的交叉反应性。
本研究说明了来自冈比亚采采蝇的rTsal1作为广泛采采蝇物种暴露的敏感生物标志物的潜在用途。我们提出，抗rTsal1 IgG的检测可能是采采蝇存在的一种有前景的血清学指标，将成为监测非洲大陆采采蝇控制努力影响的有价值工具。
