Dramatic changes in gene expression in adherent C. fasciculata reveal potential mechanisms for insect-specific adhesion of kinetoplastid parasites

Kinetoplastids are a group of parasite species, several of which cause important diseases in human and livestock. Nearly all of these pathogenic species are transmitted by insect vectors, in which the parasites undergo a specific developmental program. One shared event undergone by multiple species is adherence to insect tissue. This adhesion occurs by means of a hemidesmosome-like structure that is thus far uncharacterized. We have used the monoxenous parasite Crithidia fasciculata, which exclusively infects mosquitoes, to study this process of parasite adhesion in the insect. We have transcriptionally profiled adherent and swimming forms of the parasite that have been generated in vitro, and compared these profiles to the adhesive form in the mosquito. Using a dual-RNAseq approach, we have also identified several genes that are differentially regulated in infected versus uninfected mosquitoes, including several immune genes. This indicates that the mosquito is responding to the presence of the parasites. Overall design: We isolated RNA from three flasks containing exclusively swimming C. fasciculata, and from three flasks containing exclusively adherent C. fasciculata. One of the replicates of adherent cells was excluded for technical reasons. We also infected three separate generations of mosquitoes with C. fasciculata, isolated RNA, and compared them RNA from age-matched uninfected controls.