%0 Generic
%A Beyer, Konrad
%D 2017
%F heidok:23561
%R 10.11588/heidok.00023561
%T Collective motion and adhesin dynamics of Plasmodium sporozoites
%U https://archiv.ub.uni-heidelberg.de/volltextserver/23561/
%X To fulfill its complex life cycle Plasmodium needs to cross various tissue barriers and invade specific cell types. Its journey inside the mosquito involves active invasion of sporozoites into salivary glands from where these motile forms can be transmitted to the host. To perform active movement inside the mosquito as well as the skin and liver of the host, sporozoites possess an uncommon form of locomotion termed “gliding motility”. Force required for motility is generated by an actin ‐ myosin motor complex and currently thought to be transduced to the sporozoite environment via surface adhesins belonging to the TRAP family. Sporozoites are curved and highly polarized cells capable of active circular movement in vitro. For the first time, our group has observed collective motion of sporozoites within infected salivary glands of Anopheles stephensi mosquitoes following preparation. Most interestingly we observed them to form circling formations, which we termed “vortices” containing up to a hundred sporozoites as well as “swarms” of two to seven sporozoites gliding closely associated to each other.   The first part of my thesis was to reach a deeper understanding of these collective migration phenomenons. Here, I show that vortices and swarms emerge from “resting” stacks of sporozoites that redistribute from the central gland cavity to the gland periphery during the preparation process and actively start to migrate individually at the basal membrane surrounding the gland. I further observed vortices to form over several minutes and be stable for hours whereas swarms form in the range of seconds and are stable for up to several minutes. Analysis of basic physical parameters of vortices (e.g. size, speed, angular speed and curvature) helped to broaden our understanding of their characteristics. Most interestingly, we observed vortices to consist of one up to several layers. Investigation of two mutant parasite lines revealed that sporozoites lacking the actin bundling protein coronin are still able to form vortices as well as swarms besides showing aberrant gliding on glass. In contrast, sporozoites lacking the chaperone HSP20 completely fail to form vortices and swarms.  In the second part of my thesis I focused on the interplay of the three known sporozoite adhesins (TRAP, S6 and TLP), which have already been characterized independently throughout various studies and are known to play a major role in invasion and gliding motility of sporozoites. As a first step, I used double homologous recombination to create the double knockouts (ΔTRAP/ΔS6, ΔTLP/ΔTRAP and ΔTLP/ΔS6), two independent triple knockout lines (ΔTRAP/ΔTLP/ΔS6) as well as the TRAP complemented ΔTLP/ΔS6 line. Characterization of the generated lines confirmed the dominating TRAP and S6 phenotype blocking and strongly reducing sporozoite salivary gland invasion, respectively. I further demonstrate that once inside the salivary gland, TLP/S6 knockout sporozoites are still capable to undergo natural transmission via mosquito bites. Astonishingly, triple knockout sporozoites in the mosquito hemolymph can still attach and show the so-called patch gliding behavior, a limited form of gliding, indicating the existence of at least one further surface adhesin involved in gliding motility.  Taken together, this study provides fundamental insights into the previously undescribed collective motion of Plasmodium sporozoites which might serve as model system for future studies and broadened our understanding of the interplay of sporozoite surface adhesins.