Sera from Lupus Patients Inhibit Growth of P. <i>Falciparum</i> in Culture

Abstract

A large number of malaria immune persons from Eastern India were found to possess antibodies to the ribosomal phosphoprotein P0 (PfP0) of the human malarial parasite Plasmodium falciparum. The characterization of PfP0 has been reported recently, and it has been shown that antibodies against PfP0 inhibit P. falciparum in vitro. About 10-15% of the patients suffering from the autoimmune disorder Systemic Lupus Erythematosus (SLE) possess autoantibodies to the human ribosomal P proteins. In order to test the cross-reactivity of the human and Plasmodium falciparum P0 proteins and to compare the SLE patients' and malaria immune persons' response, sera from 41 Indian SLE patients were tested against the P. falciparum PfP0 by Western blot analysis. Four of these samples (9.75%) were found to be cross-reactive to the carboxy-terminal domain of PfP0, but not to the amino-terminal domain of PfP0. The PfP0 reactive SLE sera inhibited the growth of Plasmodiumfalciparum in vitro. IgG purified from one such cross-reactive serum sample inhibited the growth of P. falciparum. Depletion of anti-P0 antibodies from this IgG preparation resulted in the removal of growth inhibition. Sera samples were collected from one of the PfP0 positive SLE patient from Mumbai, India, at different stages of the disease progression, and screened for the presence of anti-PfP0 antibodies. This patient's serum inhibited the parasite growth in vitro only during the phase in which anti-PfP0 antibodies were detected.