Comparative infectivity of knobless and knobby clones of Plasmodium falciparum in splenectomized and intact Aotus trivirgatus monkeys.
In two experiments, two knobless (K-) and two knob-producing (K+) clone-cultures of Plasmodium falciparum, FCR-3/Gambia strain, were injected into four Aotus trivirgatus monkeys. The parasitemia in the K(-)-infected splenectomized (S-) monkey rose to a peak of 2.1% on the 16th day, while it reached only 0.7% at the same time in the K+ infected S- animal. Passage from these animals (karyotype VI) into two intact (S+), naive monkeys of karyotype III resulted in very light infections somewhat higher with K+ than with K-. This experiment was repeated with two different clones in two other S- monkeys of karyotype III. Again, the parasitemia of the K+ infected monkey was appreciably below that of the K- monkey. Transfer of parasites into S+ animals of karyotype II resulted in very light infection and, as before, the K+ did somewhat better. About 2 months after its initial infection, the K(+)-infected S- animal from the second experiment came down with a recurrent malaria infection. Electron-microscopic observations on blood from this monkey revealed that the previously K+ parasites had become knobless (K-). Transfer of this material into an S+, naive monkey, again, gave a barely detectable infection. After splenectomy a recrudescence occurred. The results strongly indicate that K- clones of P. falciparum are more infectious to S- Aotus monkeys than K+ clones, whereas in S+ monkeys the situation is reversed.
D000818:Animals; D000830:Animals, Laboratory; D001029:Aotus trivirgatus; D001769:Blood / Q000469:parasitology; D002427:Cebidae; D002999:Clone Cells; D014644:Genetic Variation; D008288:Malaria / Q000469:parasitology / Q000662:veterinary*; D008992:Monkey Diseases / Q000469:parasitology*; D010963:Plasmodium falciparum / Q000235:genetics / Q000472:pathogenicity* / Q000648:ultrastructure; D013154:Spleen / Q000276:immunology*; D013156:Splenectomy / Q000662:veterinary