First published May 1, 2008 - More info
In this study we investigated why bloodstream forms of Trypanosoma brucei gambiense cross human brain microvascular endothelial cells (BMECs), a human blood-brain barrier (BBB) model system, at much greater efficiency than do T. b. brucei. After noting that T. b. gambiense displayed higher levels of cathepsin L–like cysteine proteases, we investigated whether these enzymes contribute to parasite crossing. First, we found that T. b. gambiense crossing of human BMECs was abrogated by N-methylpiperazine-urea-Phe-homopheylalanine-vinylsulfone-benzene (K11777), an irreversible inhibitor of cathepsin L–like cysteine proteases. Affinity labeling and immunochemical studies characterized brucipain as the K11777-sensitive cysteine protease expressed at higher levels by T. b. gambiense. K11777-treated T. b. gambiense failed to elicit calcium fluxes in BMECs, suggesting that generation of activation signals for the BBB is critically dependant on brucipain activity. Strikingly, crossing of T. b. brucei across the BBB was enhanced upon incubation with brucipain-rich supernatants derived from T. b. gambiense. The effects of the conditioned medium, which correlated with ability to evoke calcium fluxes, were canceled by K11777, but not by the cathepsin B inhibitor CA074. Collectively, these in vitro studies implicate brucipain as a critical driver of T. b. gambiense transendothelial migration of the human BBB.
Olga V. Nikolskaia, Ana Paula C. de A. Lima, Yuri V. Kim, John D. Lonsdale-Eccles, Toshihide Fukuma, Julio Scharfstein, Dennis J. Grab
Original citation: J. Clin. Invest.116:2739–2747 (2006). doi:10.1172/JCI27798.
Citation for this erratum: J. Clin. Invest.118:1974 (2008). doi:10.1172/JCI27798C1.
The Trypanosoma species used in this study included a clinically relevant human CSF isolate and bloodstream form (BSF) from a patient with sleeping sickness. A cloned derivative from this parasite termed “IL1852” was originally identified as a T.b. gambiense and was denoted accordingly in the manuscript.
However, the authors recently discovered that IL1852 contains the SRA gene, a characteristic only encountered in T.b. rhodesiense (1). Therefore, because ILRI T.b. gambiense IL2343, a clone derivative of STIB386AA that was derived from TH144/78E(020), was later reclassified as a T.b. rhodesiense (2), the authors have reclassified IL1852 as a T.b. rhodesiense to maintain accuracy.
While the reclassification affects certain aspects of the conclusions of this work, it does not invalidate the key finding of a difference in the BBB traversal between human and animal trypanosomes that correlates with the greater incidence of CNS infection in human compared with animal parasites.