Predicting Antidisease Immunity Using Proteome Arrays and Sera from Children Naturally Exposed to Malaria

Abstract

Malaria remains one of the most prevalent and lethal human infectious diseases worldwide. A comprehensive characterization of antibody responses to blood stage malaria is essential to support the development of future vaccines, sero-diagnostic tests, and sero-surveillance methods. We constructed a proteome array containing 4441 recombinant proteins expressed by the blood stages of the two most common human malaria parasites, P. falciparum (Pf) and P. vivax (Pv), and used this array to screen sera of Papua New Guinea children infected with Pf, Pv, or both (Pf/Pv) that were either symptomatic (febrile), or asymptomatic but had parasitemia detectable via microscopy or PCR. We hypothesized that asymptomatic children would develop antigen-specific antibody profiles associated with antidisease immunity, as compared with symptomatic children. The sera from these children recognized hundreds of the arrayed recombinant Pf and Pv proteins. In general, responses in asymptomatic children were highest in those with high parasitemia, suggesting that antibody levels are associated with parasite burden. In contrast, symptomatic children carried fewer antibodies than asymptomatic children with infections detectable by microscopy, particularly in Pv and Pf/Pv groups, suggesting that antibody production may be impaired during symptomatic infections. We used machine-learning algorithms to investigate the relationship between antibody responses and symptoms, and we identified antibody responses to sets of Plasmodium proteins that could predict clinical status of the donors. Several of these antibody responses were identified by multiple comparisons, including those against members of the serine enriched repeat antigen family and merozoite protein 4. Interestingly, both P. falciparum serine enriched repeat antigen-5 and merozoite protein 4 have been previously investigated for use in vaccines. This machine learning approach, never previously applied to proteome arrays, can be used to generate a list of potential seroprotective and/or diagnostic antigens candidates that can be further evaluated in longitudinal studies. Molecular & Cellular

Severe adult malaria is associated with specific PfEMP1 adhesion types and high parasite biomass

“…This methodology generates a multitude of decision trees and measures the mean decrease in classifier accuracy (MDCA) when a particular feature (e.g., transcript level detected by a var primer) is removed from the model. Recent advances in computational techniques have made it possible to associate P values with features ranked in this manner (40,41). First, we used a RF (39) with 1,000,000 trees to select parasite features that could be used to accurately predict patient hospitalization and disease severity.…”

Genome-Scale Protein Microarray Comparison of Human Antibody Responses in Plasmodium vivax Relapse and Reinfection

“…Furthermore 1,949 P. vivax recombinant proteins (87%) were expressed with at least one tag suggesting that these recombinant proteins were at least partially expressed. 22 Microarray data analysis. A reactive protein was defined as a protein that had a signal intensity values > 2-fold the mean of the "no DNA" intensity values for the same sample (i.e., column on the matrix) in at least 10% of the samples in the Pv-infected group, Pv reinfected group or the Pv relapse group.…”

“…A proteome array was designed containing 2,233 P. vivax recombinant proteins, representing 1,936 predicted P. vivax asexual blood-stage proteins and comprised as recently described. 22 Proteins predicted to be secreted or present on the parasite surface, on the basis of the presence of a secretory signal peptide or transmembrane domains, were annotated as such in PlasmoDB 34,35 and preferentially included. Additional selection for expression of P. vivax genes included expression microarray evidence for blood-stage expression.…”

“…21 Recent work from Papua New Guinea-where all four major Plasmodium spp. circulate at intense level-has led to the development of focused protein microarrays 22 composed of both P. falciparum and P. vivax recombinant proteins. Because P. vivax samples from humans have low parasitemia, and only in limited quantities from non-human primates, seroepidemiology studies using *Address correspondence to Joseph M. Vinetz, Department of Medicine, Division of Infectious Diseases, University of California San Diego, 9500 Gilman Drive 0760, Biomedical Research Facility-2 Room 4A16, La Jolla, CA 92093.…”

Malaria in India: The Need for New Targets for Diagnosis and Detection of Plasmodium vivax

“…[42] Finally, a protein microarray with 1963 P. vivax proteins expressed in a cell-free Escherichia coli in vitro transcription–translation system were used to study host responses in symptomatic children and asymptomatic children who were diagnosed as positive for P. vivax but were not febrile. [43] This report suggested that a wider range of serological responses to P. vivax proteins in asymptomatic children could perhaps provide protection. A recent report that used 515 P. vivax proteins to probe 353 plasma samples from Indian patients also identified immunogenic antigens.…”