P. Druilhe et al., IN-VIVO VERITAS - LESSONS FROM IMMUNOGLOBULIN-TRANSFER EXPERIMENTS INMALARIA PATIENTS, Annals of tropical medicine and parasitology, 91, 1997, pp. 37-53
In most fields of medicine, experimentation starts with studies in vit
ro, moves to animal models and eventually proceeds to research on huma
ns. Malaria provides a good example of the limits of this progression.
The most important malarial parasite of man, Plasmodium falciparum, o
nly infects man. The specificity of this relationship accounts for the
many differences which exist between artificial models of falciparum
malaria and natural infections. Ultimately, human infections appear to
be the sole, relevant 'model' for the study of human-Plasmodium inter
actions. Immunoglobulin-transfer experiments, for example, clearly ind
icated that antibodies mediated the state of acquired immunity called
premunition. However, further studies in vitro or in animal models led
to conflicting results about how the antibodies acted. Transfer exper
iments in human volunteers, appropriately coupled to in-vitro studies,
seemed the only way to help solve this issue. The design of these inv
estigations, with its technical and ethical aspects, is reviewed here,
along with the main published and unpublished results. The identifica
tion of a monocyte-mediated, antibody-dependent (ADCI) mechanism led t
o a new merozoite-surface antigen (MSP-3) being identified and provide
d an explanation for the long delay in the acquisition of protection.
It appears that experiments in humans not only help to confirm indicat
ions obtained using animal models, but can also have a truly explorato
ry role, since they can both raise completely new issues and provide a
nswers to them.