Protozoan parasites are the most challenging and complex organisms that humans cells are forced to interact with. Although the infection by prokaryotes and viruses might also be complex and even disastrous for the cell, the relationship with eukaryotic parasites, especially protozoa, can be of a more troublesome nature. For more than a century we have been assisting the success story of protozoan parasites, e. g., Trypanosoma cruzi, Trypanosoma brucei gambiense, Leishmania braziliensis, Leishmania donovani and Plasmodium falciparum in their dispute with humans. Their infectious capacity has eluded our immune defences and defied all the therapeutic approaches tested so far, including powerful drugs and smart vaccine strategies. None of the methods used has proved to be effective for the goal of complete parasite elimination from the human environment. The parasites continuously undermine and challenge both our public health policy and the scientific efforts to understand them. Will we one day be able to grasp all the knowledge about them? Well, one of the most remarkable scientists of the XX century, the physicist and Nobel prize winner Richard Feynman, once said in his famous talk that opened the doors of nanotechnology in 1959: “There is Plenty of Room at the Bottom'' - not just “There is Room at the Bottom'' (its.caltech.edu/~feynman/plenty.html). Going a bit far from the context of this talk, Feynman’s metaphor might be valid to our current knowledge of host parasite relationships in biochemical terms: we have not reached the bottom, there is much to unveil, there is much ground to be explored.
From the both sides of the host parasite equation there comes news about biochemical interplay: there are host enzymes and biomolecules that help parasite survival inside and outside the host cell. In the April 2015 [110(2)] issue of Memórias do Instituto Oswaldo Cruz, two papers report more evidence that help delineate the biochemical pathway that two protozoan parasites follow to improve their odds of survival: (i) Role of cyclooxygenase-2 in Trypanosoma cruzi survival in the early stages of parasite host-cell interaction (Moraes et al. 2015) and (ii) Iron from haemoglobin and haemin modulates nucleotide hydrolysis in Trichomonas vaginalis (Vieira et al. 2015). These two protozoan parasites, being ancient eukaryotes, share many molecular and genomic features but diverge in their parasitic lifestyle: one has an intracellular stage (T. cruzi) and the other is an obligate extracellular (T. vaginalis). They also have different environments, different reactions to invasion and different strategies to negotiate survival with their hosts. The biochemical evidences reported by these research groups remind us that regardless of the pathway the parasite selects for entry into the host, it will always be favoured by chance. Humans produce thousands of biomolecules, have a complex metabolism and statistically there is at least one biomolecule whose interaction with a parasite counterpart will by chance unlock one of the hundreds of molecular gateways the human cells use to control their interactions with the environment.
Archimedes of Syracuse, the great mathematician of antiquity once said: “Give me a place to stand and with a lever I will move the whole world.” (math.nyu.edu/~crorres/Archimedes/Lever/LeverQuotes.html). If one more metaphor is allowed here, a translation for the parasitic world might mean: “give me time and mutations and with some molecular tricks I will elude the biochemical gatekeepers of my hosts!”.
Adeilton Alves Brandão | Editor
Moraes KCM, Diniz LF, Bahia MT 2015. Role of cyclooxygenase-2 in Trypanosoma cruzi survival in the early stages of parasite host-cell interaction. Mem Inst Oswaldo Cruz 110: 181-191.
Vieira PB, Silva NLF, Kist LW, de Oliveira GMT, Bogo MR, De Carli GA, Macedo AJ, Tasca T 2015. Iron from haemoglobin and haemin modulates nucleotide hydrolysis in Trichomonas vaginalis. Mem Inst Oswaldo Cruz 110: 201-208.