Abstract
Tsetse are vectors of pathogenic trypanosomes, agents of human and animal trypanosomiasis in Africa. Components of tsetse saliva (sialome) are introduced into the mammalian host bite site during the blood feeding process and are important for tsetse’s ability to feed efficiently, but can also influence disease transmission and serve as biomarkers for host exposure. We compared the sialome components from four tsetse species in two subgenera: subgenus Morsitans: Glossina morsitans morsitans (Gmm) and Glossina pallidipes (Gpd), and subgenus Palpalis: Glossina palpalis gambiensis (Gpg) and Glossina fuscipes fuscipes (Gff), and evaluated their immunogenicity and serological cross reactivity by an immunoblot approach utilizing antibodies from experimental mice challenged with uninfected flies. The protein and immune profiles of sialome components varied with fly species in the same subgenus displaying greater similarity and cross reactivity. Sera obtained from cattle from disease endemic areas of Africa displayed an immunogenicity profile reflective of tsetse species distribution. We analyzed the sialome fractions of Gmm by LC-MS/MS, and identified TAg5, Tsal1/Tsal2, and Sgp3 as major immunogenic proteins, and the 5'-nucleotidase family as well as four members of the Adenosine Deaminase Growth Factor (ADGF) family as the major non-immunogenic proteins. Within the ADGF family, we identified four closely related proteins (TSGF-1, TSGF-2, ADGF-3 and ADGF-4), all of which are expressed in tsetse salivary glands. We describe the tsetse species-specific expression profiles and genomic localization of these proteins. Using a passive-immunity approach, we evaluated the effects of rec-TSGF (TSGF-1 and TSGF-2) polyclonal antibodies on tsetse fitness parameters. Limited exposure of tsetse to mice with circulating anti-TSGF antibodies resulted in a slight detriment to their blood feeding ability as reflected by compromised digestion, lower weight gain and less total lipid reserves although these results were not statistically significant. Long-term exposure studies of tsetse flies to antibodies corresponding to the ADGF family of proteins are warranted to evaluate the role of this conserved family in fly biology.
Highlights
Tsetse flies are vectors of pathogenic trypanosomes, which cause Human African Trypanosomiasis (HAT), known as Sleeping Sickness
We show that one member of the Adenosine Deaminase Growth Factor (ADGF) family with adenosine deaminase motifs, TSGF-2, is nonimmunogenic in Glossina morsitans in mice, while the same protein from Glossina fuscipes is highly immunogenic
We show that short-term exposure of G. morsitans to mice passively immunized by anti-TSGF antibodies leads to slight but not statistically significant negative fitness effects
Summary
Tsetse flies are vectors of pathogenic trypanosomes, which cause Human African Trypanosomiasis (HAT), known as Sleeping Sickness. Many HAT endemic countries, including Central African Republic, Chad, Congo, Côte d’Ivoire, Uganda and Sudan, with disease occurring in remote areas, have limited access to surveillance, treatment and control measures [4]. In countries such as Guinea, the first country affected by HAT epidemics in West Africa, surveillance activities were eliminated especially in the context of the EBOLA epidemic. In addition to HAT, nagana or Animal African Trypanosomosis (AAT), caused by Trypanosoma brucei brucei and the related parasites, Trypanosoma congolense and Trypanosoma vivax, limits effective cattle rearing across ten million square kilometers of Africa [5] and has wide implications for land use, agricultural practices and nutrition [6]
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