Furthermore, Acanthamoeba granulomatous encephalitis is mostly limited to immunocompromised populations, and insects have an entirely innate immune defence system, suggesting that it is realistic to use locusts as a tractable model in which to study the pathogenesis of Acanthamoeba granulomatous encephalitis. Although Acanthamoeba spread to many tissues and were found in the haemolymph throughout the course of the infection, none of the isolates (T1 and T4 genotype) were ever found in locust faeces (unpublished observations).

For the first time, histological sectioning revealed the occasional presence of some amoebae MLN2238 mouse in the lumen of the locust foregut, but no damage to the wall of the foregut was evident in any of the locusts subjected to microscopic examination. Indeed, the apical surfaces BI 2536 in vitro of the cells lining the foregut have a cuticle, which could represent a barrier to penetration by Acanthamoeba. Unfortunately, infected locusts destined for histological examination were not kept isolated from one another (as was the general case), and food replenishment and removal of dead animals took place only once every 24 h, so cannibalism was possible if locusts died shortly after this daily routine. It is likely therefore that amoebae observed occasionally in the lumen of foregut were simply there because they were

consumed by cannibalism of a dead infected locust. This is a novel finding and it is strengthened by the fact that the histological sections never revealed evidence of damage to the wall of the foregut and suggest that amoebae do not infect locusts via the oral route, a finding that is consistent with infection in EX 527 datasheet vertebrates. Another significant finding was the entry of amoebae into the

locust CNS, which appeared to be associated with disruption of the neural lamella and the perineurium/glial cell complex that constitutes the locust blood-brain barrier [29–31]. This is consistent with the studies in vitro showing that amoebae cross human brain microvascular endothelial cells, which constitute the blood-brain barrier, by affecting the integrity of the cell monolayer [32]. At present, the basis Interleukin-2 receptor of the damage to the locust blood-brain barrier is not clear, i.e., amoeba and/or host inflammatory response. Recent studies in vitro show that serine proteases secreted by Acanthamoeba play an important role in affecting the integrity of the human brain microvascular endothelial cell monolayers [32], and the role of proteases and additional virulence determinants will be addressed in future studies in vivo using locusts. In addition, there is a need for a comparative study to test several additional Acanthamoeba isolates of various genotypes in locusts versus mice.