Protein Microarray Analysis of Antibody Responses to Plasmodium falciparum in Western Kenyan Highland Sites with Differing Transmission Levels

Abstract

Malaria represents a major public health problem in Africa. In the East African highlands, the high-altitude areas were previously considered too cold to support vector population and parasite transmission, rendering the region particularly prone to epidemic malaria due to the lack of protective immunity of the population. Since the 1980’s, frequent malaria epidemics have been reported and these successive outbreaks may have generated some immunity against Plasmodium falciparum amongst the highland residents. Serological studies reveal indirect evidence of human exposure to the parasite, and can reliably assess prevalence of exposure and transmission intensity in an endemic area. However, the vast majority of serological studies of malaria have been, hereto, limited to a small number of the parasite’s antigens. We surveyed and compared the antibody response profiles of age-stratified sera from residents of two endemic areas in the western Kenyan highlands with differing malaria transmission intensities, during two distinct seasons, against 854 polypeptides of P. falciparum using high-throughput proteomic microarray technology. We identified 107 proteins as serum antibody targets, which were then characterized for their gene ontology biological process and cellular component of the parasite, and showed significant enrichment for categories related to immune evasion, pathogenesis and expression on the host’s cell and parasite’s surface. Additionally, we calculated age-fitted annual seroconversion rates for the immunogenic proteins, and contrasted the age-dependent antibody acquisition for those antigens between the two sampling sites. We observed highly immunogenic antigens that produce stable antibody responses from early age in both sites, as well as less immunogenic proteins that require repeated exposure for stable responses to develop and produce different seroconversion rates between sites. We propose that a combination of highly and less immunogenic proteins could be used in serological surveys to detect differences in malaria transmission levels, distinguishing sites of unstable and stable transmission.

Effect of transmission intensity and age on subclass antibody responses to Plasmodium falciparum pre-erythrocytic and blood-stage antigens

“…Yet the relative differences in antibodies detected across sites still likely reflects true differences since the method of analysis was the same for each site. A recent publication (Baum et al, 2013) using protein microarray to examine total IgG antibody response in other areas of western Kenya with high versus lower malaria transmission showed that antibodies to some antigens were acquired with much less exposure requirement than antibodies to other antigens, similar to the findings in this study. Assessment of subclass antibodies by high-throughput microarray might shed further light on differences in antibody acquisition and seroconversion in areas of differing transmission.…”

Novel serologic biomarkers provide accurate estimates of recent Plasmodium falciparum exposure for individuals and communities

“…The antigenic targets for such assays have been mostly limited to a small set of readily available recombinant proteins, generally selected for recognition by high titers of antibodies in immune individuals and not for their ability to provide quantitative information regarding exposure (73,74). Recent studies have evaluated responses to multiple antigens simultaneously, suggesting that certain responses may be more informative of exposure in particular settings (58,75,76). A fundamental distinction between prior efforts and the approach taken in this study is that, here, recent Pf exposure in individuals was used to identify the most informative antibody responses among hundreds of candidates.…”

“…Additionally, dynamics of antibody acquisition and maintenance vary based on exposure intensity and age; thus, the degree to which some serologic biomarkers predict exposure will likely vary in these contexts (39,57,75,79). Our study only evaluated participants ages 3-7 y old living in two areas of Uganda with moderate or high transmission and ages 2-7 y old living in an area with intense seasonal transmission in Mali.…”

An immunomics approach for the analysis of natural antibody responses to Plasmodium vivax infection

“…53 Proteome-wide microarray technology has been well documented for characterizing the antibody reactivity profiles of P. falciparum infection in recent years. 26,[54][55][56] In this study, a blood stage proteome-wide microarray composing 1936 polypeptides of P. vivax was used to characterize the immunomic profiles of P. vivax infection. Only a small amount of candidates overlap with previous immunogenic proteins from the P. vivax View Article Online blood-stage (e.g.…”