High mobility group box (HMGB) proteins of Plasmodium falciparum:: DNA binding proteins with pro-inflammatory activity

High mobility group box chromosomal protein I (HMGB I), known as an abundant, non-histone architectural chromosomal protein, is highly conserved across different species. Homologues of HMGB I were identified and cloned from malaria parasite, Plasmodium falciparum. Sequence analyses showed that the P.Falciparum HMGB 1 (PfHMGB 1) exhibits 45, 23 and 18%, while PfHMGB2 shares 42, 21 and 17% homology with Saccharomyces cerevisiae, human and mouse HMG box proteins respectively. Parasite PfHMGB I and PfHMGB2 proteins contain one HMG Box domain similar to B-Box of mammalian HMGB1. Electrophoretic Mobility Shift Assay (EMSA) showed that recombinant PfHMGB 1 and PfHMGB2 bind to DNA. Immunofluorescence Assay using specific antibodies revealed that these proteins are expressed abundantly in the ring stage nuclei. Significant levels of PfHMGB 1 and PfHMGB2 were also present in the parasite cytosol at trophozoite and schizont stages. Both, PfHMGB I and PfHMGB2 were found to be potent inducers of pro-inflammatory cytokines such as TNF alpha. from mouse peritoneal macrophages as analyzed by both reverse transcription PCR and by ELISA. These results suggest that secreted PfHMGB I and PtHMGB2 may be responsible for eliciting/ triggering host inflammatory immune responses associated with malaria infection. (c) 2007 Elsevier Ireland Ltd. All rights reserved.