Abstract
Sodalis glossinidius, a vertically transmitted microbial symbiont of the tsetse fly, is currently considered as a potential delivery system for anti-trypanosomal components that reduce or eliminate the capability of the tsetse fly host to transmit parasitic trypanosomes, an approach also known as paratransgenesis. An essential step in developing paratransgenic tsetse is the stable colonization of adult flies and their progeny with recombinant Sodalis bacteria, expressing trypanocidal effector molecules in tissues where the parasite resides. In this study, Sodalis was tested for its ability to deliver functional anti-trypanosome nanobodies (Nbs) in Glossina morsitans morsitans. We characterized the in vitro and in vivo stability of recombinant Sodalis (recSodalis) expressing a potent trypanolytic nanobody, i.e. Nb_An46. We show that recSodalis is competitive with WT Sodalis in in vivo conditions and that tsetse flies transiently cleared of their endogenous WT Sodalis population can be successfully repopulated with recSodalis at high densities. In addition, vertical transmission to the offspring was observed. Finally, we demonstrated that recSodalis expressed significant levels (ng range) of functional Nb_An46 in different tsetse fly tissues, including the midgut where an important developmental stage of the trypanosome parasite occurs. We demonstrated the proof-of-concept that the Sodalis symbiont can be genetically engineered to express and release significant amounts of functional anti-trypanosome Nbs in different tissues of the tsetse fly. The application of this innovative concept of using pathogen-targeting nanobodies delivered by insect symbiotic bacteria could be extended to other vector-pathogen systems.
Highlights
Sodalis glossinidius, a vertically transmitted microbial symbiont of the tsetse fly, is currently considered as a potential delivery system for anti-trypanosomal components that reduce or eliminate the capability of the tsetse fly host to transmit parasitic trypanosomes, an approach known as paratransgenesis
The tsetse fly harbors a natural commensal bacterium i.e. Sodalis glossinidius, which is ideally suited as a paratransgenic platform organism since it i) resides in different tsetse tissues that are in close proximity to pathogenic trypanosomes [6]; ii) can be cultured and genetically modified in vitro
We show that recSodalis expressing a potent trypanolytic nanobody, i.e. Nb_An46, was stably maintained in vivo only when the WT Sodalis population was significantly reduced (>95% of the normal population) prior to recSodalis introduction
Summary
A vertically transmitted microbial symbiont of the tsetse fly, is currently considered as a potential delivery system for anti-trypanosomal components that reduce or eliminate the capability of the tsetse fly host to transmit parasitic trypanosomes, an approach known as paratransgenesis. The tsetse fly harbors a natural commensal bacterium i.e. Sodalis glossinidius, which is ideally suited as a paratransgenic platform organism since it i) resides in different tsetse tissues that are in close proximity to pathogenic trypanosomes (e.g. midgut) [6]; ii) can be cultured and genetically modified in vitro [7,8]; iii) is maternally transmitted to the offspring [9] and iv) is restricted to the tsetse host niche ensuring that this symbiont is a safe candidate for use in the paratransgenic strategy [10]. We developed recombinant Sodalis (recSodalis) strains expressing functional anti-trypanosome nanobodies These strains were shown to release considerable amounts of functional anti-trypanosome Nbs to the extracellular culture environment and to have no negative effects on the bacterium in an in vitro context [14]
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