Antimalarial Activity of Human Group IIA Secreted Phospholipase A in Relation to Enzymatic Hydrolysis of Oxidized Lipoproteins.

The level of human group IIA secreted phospholipase A (hGIIA sPLA) is increased in the plasma of malaria patients, but its role is unknown. In parasite culture with normal plasma, hGIIA is inactive against , contrasting with hGIIF, hGV, and hGX sPLAs, which readily hydrolyze plasma lipoproteins, release nonesterified fatty acids (NEFAs), and inhibit parasite growth. Here, we revisited the anti- activity of hGIIA under conditions closer to those of malaria physiopathology where lipoproteins are oxidized. In parasite culture containing oxidized lipoproteins, hGIIA sPLA was inhibitory, with a 50% inhibitory concentration value of 150.0 ± 40.8 nM, in accordance with its capacity to release NEFAs from oxidized particles. With oxidized lipoproteins, hGIIF, hGV, and hGX sPLAs were also more potent, by 4.6-, 2.1-, and 1.9-fold, respectively. Using specific immunoassays, we found that hGIIA sPLA is increased in plasma from 41 patients with malaria over levels for healthy donors (median [interquartile range], 1.6 [0.7 to 3.4] nM versus 0.0 [0.0 to 0.1] nM, respectively; < 0.0001). Other sPLAs were not detected. Malaria plasma, but not normal plasma, contains oxidized lipoproteins and was inhibitory to when spiked with hGIIA sPLA Injection of recombinant hGIIA into mice infected with reduced the peak of parasitemia, and this was effective only when the level of plasma peroxidation was increased during infection. In conclusion, we propose that malaria-induced oxidation of lipoproteins converts these into a preferential substrate for hGIIA sPLA, promoting its parasite-killing effect. This mechanism may contribute to host defense against in malaria where high levels of hGIIA are observed.