| dc.description.abstract | African trypanosome, Trypanosoma congolense parasite transmitted by tsetse flies (Glossina spp) cause
Animal African Trypanosomiasis in (AAT or Nagana) in animals. The parasite undergo cyclical ( development in the tsetse vector and transform to become metacyclics which .are forms infective to
animals. The molecular events underpinning this development process and tsetse responses to infection in
cardia and proboscis is underexplored due to challenges of obtaining enough biological materials, access to
tsetse colony and analysis complexes of such studies. This study characterized differentially expressed
genes during Glossina morsitans morsitans and T. congolense interactions in the cardia and proboscis of
tsetse fly to shed light on the molecular cross-talks between the parasite and the vector during infections in
these organs. This study was a laboratory-based and involved use and infection oflaboratory adapted tsetse
flies and parasites. Ribonucleic acid was extracted from T.congolense infected male G.. m. morsitans
cardia or proboscis (PB) and sequenced in high throughput Illumina Next Generation Sequencing (NGS)
platform. EdgeR and CLC-genomics was used to determine differentially expressed transcripts in tsetse
and trypanosomes, and functional analysis done using blast2GO, profcom, KEGG, WebGestalt and
TrypanoCyc. Reverse genetics (RNAi silencing) was used to functionally characterize the roles of selected
peritrophic matrix (PM) peritrophin (Per) 12 and/or 108in the cardia. Immunofluorescent and confocal
microscope was used to localize expression of selected parasite protein. Statistical analysis was performed
either using R-statistic or GraphPad prism version 7. Cardia-enriched transcripts (n=422) encoded putative
proteins functionally associated with peritrophic matrix structure. Upon infection of the cardia,
88transcripts were suppressed while62 were induced. The suppressed transcripts were functionally
associated with transport and metabolic process while induced ones with immunity, suggesting enhanced
defense mechanism in the cardia against trypanosomes. The RNAi significantly suppressed (51-81%)
expression of per transcripts and resulted in significantly higher number of tsetse flies being infected by
trypanosome but impeded proliferation of Serratia bacteria (in GmmPer12). Proboscis enriched transcripts
(n=668) were predominately associated with muscle tissue, chemo-sensation, chitin-cuticle development as
well as mechanoreceptors that monitor blood flow during tsetse feeding and interaction with trypanosomes.
Cellular structures associated with muscles and cells in the proboscis were evident by microscopy. Like
cardia, more transcripts were suppressed (n= 88) than induced (n=38) by the infection in the proboscis. The
induced genes were associated with cell division while those suppressed were associated with metabolic
processes, extracellular matrix, ATP-binding and immunity suggesting increased cell and tissue renewal
process of host. Oxidative phosphorylation and amino acid metabolism appears to be a major source of
energy for the parasite. in both organs. More transcripts were induced (n= 1261) in parasite infecting the
cardia than those infecting the proboscis (n=870). Product of cardia induced parasite transcripts were
associated with cell signaling, quorum sensing and several transport activities suggesting that the parasites
in the cardia scavenge for nutrients and also exhibit social behavior. The parasites in the cardia were
putatively covered by Fam50 'GARP', 'iii' and 'i' proteins. The product of proboscis-induced parasite
transcripts were associated with nucleosomes, cytoplasm and membrane-bound organelles suggesting
increased cell division. Overall, these findings suggest that cardia is immunologically active organ with
cells that produce PM proteins that also play critical role in modulating trypanosome infection outcome.
The parasites also express genes encoding putative cell surface proteins and proteins associated with
parasite differentiations that may regulate T. congolense developmental processes in tsetse fly. The
proboscis is a muscular organ with chemosensory and mechanosensory capabilities. This study provides
insight into vector-parasite interactions and points to potential molecular targets that can be exploited in
downstream search for disease transmission control initiative. | en_US |
