A critical role has been proposed for cytophilic IgOl and IgOJ subclass antibodies and monocytes and
macrophages in antimalarial immunity. Here we compared lhe isotype composition and avidity of naturally acquired
antibodies, as measured by enzyme immunoassay against a detergent-soluble extract of Plasmodium falciparum schizonts, in clinically immune Senegalese adults (n = 33) and semi-immune, adult Amazonian patients (n = 25). Plasma
were collected during an acute symptomatic P. falciparum attack and two months later, and in the absence of recrudescence or reinfection. Specific IgO, IgM, IgA, and IgO subclass antibodies were assessed. The results are summarized as follows: 1) high-avidity cytophilic antibodies predorninated in clinically immune Senegalese subjects; 2)
acutely ill Amazonian patients produced high levels of low-avidity cytophilic antibody; 3) such a response was shonlived, since two months later, the concentrations of cytophilic antibodies were significantly lower; 4) however, affinity
maturation of IgO antibodies was observed in Amazonian patients two months after the acute malaria attack. A
considerable proponion (35-46%) of anti-P. falciparum IgOI antibodies produced by African and Amazonian patients
was shown to recognize periodate-sensitive carbohydrate epitopes. The potential impact of these findings on the
design and evaluation of antimalarial vaccines is discussed.
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