Proteome Analysis of Plasmodium falciparum Extracellular Secretory Antigens at Asexual Blood Stages Reveals a Cohort of Proteins with Possible Roles in Immune Modulation and Signaling

Abstract

The highly co-evolved relationship of parasites and their hosts appears to include modulation of host immune signals, although the molecular mechanisms involved in the host-parasite interplay remain poorly understood. Characterization of these key genes and their cognate proteins related to the host-parasite interplay should lead to a better understanding of this intriguing biological phenomenon. The malaria agent Plasmodium falciparum is predicted to export a cohort of several hundred proteins to remodel the host erythrocyte. However, proteins actively exported by the asexual intracellular parasite beyond the host red blood cell membrane (before merozoite egress) have been poorly investigated so far. Here we used two complementary methodologies, two-dimensional gel electrophoresis/MS and LC-MS/MS, to examine the extracellular secreted antigens at asexual blood stages of P. falciparum. We identified 27 novel antigens exported by P. falciparum in the culture medium of which some showed clustering with highly polymorphic genes on chromosomes, suggesting that they may encode putative antigenic determinants of the parasite. Immunolocalization of four novel secreted proteins confirmed their export beyond the infected red blood cell membrane. Of these, preliminary functional characterization of two novel (Sel1 repeat-containing) parasite proteins, PfSEL1 and PfSEL2 revealed that they down-regulate expression of cell surface Notch signaling molecules in host cells. Also a novel protein kinase (PfEK) and a novel protein phosphatase (PfEP) were found to, respectively, phosphorylate/dephosphorylate parasite-specific proteins in the extracellular culture supernatant. Our study thus sheds new light on malaria parasite extracellular secreted antigens of which some may be essential for parasite development and could constitute promising new drug targets. Molecular & Cellular Proteomics 8:2102-2118, 2009.

Identification of microsporidia host-exposed proteins reveals a repertoire of rapidly evolving proteins

“…Several studies have addressed this problem by identifying proteins secreted from pathogens into culture media1011. However, such studies potentially miss proteins that are only present in the native context.…”

Characterization ofPlasmodium falciparumProteome at Asexual Blood Stages for Screening of Effective Vaccine Candidates: An Immunoinformatics Approach

“…[36][37][38][39] The results of the reactivity studies on antibodies carried out by Singh et al 16 also showed that many of the selected parasite extracellular/secreted antigens elicit an immune response during natural infection; however, the specificity and efficacy were not reported. The present study covers a panel of 32 asexual blood-stage proteins (Table 1) reported in the proteomic data of Singh et al 16 for evaluating their potential as an antigen/vaccine candidate and their immunogenicity analysis. Out of 32 proteins, 31 were predicted as probable antigens (except no.…”

“…The proteome analysis of P. falciparum asexual blood stages reveals a set of 33 proteins with possible roles in immune modulation to potential antigens. 16 Since the accession number of the highly variable malarial adhesion protein (pfEMP 1) was not provided, it is excluded from the present study. The panel of the selected 32 proteins, of which 27 were novel extracellular antigens, was retrieved from the PlasmoDB7.2 database (http:// plasmodb.org/plasmo/) using the sequence retrieval tools associated with the database (Table 1).…”

Proteomics in India: the clinical aspect

“…Proteomics of clinical isolates of malarial parasites is undertaken by institutes such as IISc, Bangalore; ICGEB, New Delhi and IIT Powai, Mumbai. These efforts are providing insights into its physiology whereas proteomic analysis of serum from infected individuals gives preliminary information concerning potential biomarkers [26–29]. Several studies have also been conducted on clinical isolates of wild type and drug resistant varieties of Leishmania across different institutes of the country like NCCS, Pune; JNU, New Delhi; CDRI, Lucknow; IOB, Bangalore; AIIMS, New Delhi; NIPER, Mohali; BHU, Varanasi and IICB, Kolkata [30–44].…”