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Relapse in Malaria: P.G. Shute’s “X Body”

May 15, 2018 - 22:20 -- Miles Markus

Was P.G. Shute’s “X Body” the same plasmodial stage that is now called a “hypnozoite”? The short answer is “No”. The malariologist who has just put this question to me has suggested that the whole reply (see below) be made available in the MalariaWorld Newsletter, considering the current topicality of the enigmatic hypnozoite; particularly in regard to the concept of malaria eradication.

When researchers in the early 1980s equated Shute’s “X Body” with hypnozoites, this was incorrect, strictly speaking. What originally happened was that in 1946, Shute used the wording “x bodies” (in lower case and in the plural); and only once in his paper. (See explanation and cited reference here [Click]). At that time, neither hepatic schizonts in primates nor hypnozoites had yet been discovered. Shute was referring to, in his words: “... the hypothetical stage of the parasite between the sporozoite and the erythrocytic parasite.” Thirty years later, in a 1976 publication of which Shute was first author (the link given above will lead to the article details), there was mention, once, of cell “X”. However, it was a host cell that was being referred to in this instance, not a stage in the plasmodial life cycle.

In summary, Shute never used the term “X Body” as restricted to (i.e. specifically for) the equivalent of what has become known as the “hypnozoite” form of the parasite, despite what has been stated in the literature by some other authors. “X Body” did, nonetheless, cover (include) the dormant sporozoite possibility.