Mapping The Kinetics And Diversity Of Adaptive Immune Responses In Children Over The Course Of An Acute Plasmodium Falciparum Infection
| dc.contributor.author | Nyakoe, N.K. | |
| dc.date.accessioned | 2024-06-06T10:46:49Z | |
| dc.date.available | 2024-06-06T10:46:49Z | |
| dc.date.issued | 2021-07 | |
| dc.description | PhD. Molecular Cell Biology of Infectious Diseases | en_US |
| dc.description.abstract | Naturally acquired immunity to malaria is Plasmodium species strain- and variant- specific. It is non-sterile and short-lived therefore requiring repeated exposure. These protective immune responses are directed against pre-erythrocytic parasites, blood-stage merozoites, or Plasmodium antigens on the surface of infected red blood cells and can be humoral or cellular. The importance of the various immune response components during malaria episodes in exposed populations remains unknown, as conclusive interpretation of data from previous studies has been limited by sampling design, disease definition, patient selection and approaches in natural infections. Long-term malaria protection in humans is likely to be determined by the cumulative effect of multiple low-level immune responses to various antigens, with each person having a unique "protective signature" based on their genetic background. Differences in transmission intensity observed in malaria-endemic areas significantly influence the acquisition of natural immunity to malaria. Antibody and cytokine responses, which contribute to malaria protective immunity, are exposure-dependent; hence, are significantly influenced by transmission intensity. Cytokine levels change rapidly upon exposure to malaria and often dictate the extent of clinical disease, whereas antibodies increase gradually and are long-lasting, and act to control and eliminate parasites. A variety of molecular mechanisms are involved in regulating these immune responses; however, it is still unclear what combination of immune features is essential for protection. Characterization of these host immune responses is important in understanding the bidirectional host-parasite interactions which will aid in effective vaccine development and eventual malaria control and elimination. This study employed a systems immunological approach to profile changes in the cellular, humoral, and molecular components of the immune system during acute P. falciparum infection and after treatment to identify immune signatures associated with varying malaria transmission intensity. Methods: Samples were collected from children of ages 5-14 years in two regions in Ghana with distinct malaria transmission intensities: Accra (low transmission) and Kintampo (high transmission). Whole blood samples were collected and a portion separated to obtain plasma from the participants when they present at the hospital with confirmed P. falciparum infection (Day 0), and convalescent phases (Day 7 and Day 21). Levels of 25 plasma cytokines were determined using a multiplex Luminex human magnetic 25-plex bead array kit. A custom-made protein microarray was used to detect IgG responses to 190 antigenic targets for blood-stage, pre-erythrocytic, and gametocyte stage parasite proteins. Antibodies and cytokine levels from the 2 sites were compared during infection and convalescent phases. Additionally, whole-blood transcriptomes were profiled by RNA-sequencing and differential gene expression compared during infection and convalescent in the study participants. Correlation and machine-learning classifier approaches were used to model immune responses to identify predictive responses correlating with distinct transmission intensities. Gene ontology modules associated with changes in immune responses in the two transmission areas were identified using gene set enrichment analysis. Results: Acute P. falciparum infection was associated with pro-inflammatory cytokines IL-6, IFN-γ, IFN-α, MIG, MCP-1, and IP-10, as well as an immunomodulatory profile mediated by IL-10, IL-2R and IL-1RA. In children from low transmission areas, they were significantly higher than in children in the high transmission areas, whereas, IFN-α, IL-6, IL-1RA, and MCP-1 were significantly associated with parasitemia. In addition, analysis of the correlation network revealed a distinctive signature between individuals from the low and high transmission areas. Of interest, is a subset of children from the high transmission area with detectable parasitemia at day 21 (D21) after treatment, with a unique cytokine signature dominated by IL-10 and IL-1RA. This was associated with asymptomatic parasitemia. Of the 190 Plasmodium antigens tested, 118 had antibody reactivity in more than 80% of the children in our study cohorts. Though overall breadth and magnitude of antibody responses was similar, the composition of these responses was different between individuals from high and low transmission areas. Hierarchical clustering revealed IgG response clusters to antigens associated with different malaria endemicity, with 48/118 antigens including EBA140, ETRAMP5, GLURP, MSP1 and MSP6 associated to low transmission area and 30/118 antigens associated to high transmission area, including Rh5.1, EBA181, VAR2CSA, ACS5, HSP40, MSP2, MSP3, MSP4, and MSP7. Machine-learning and feature selection approaches further predicted 17 antibody signatures (MSP4, MSP2 3D7, MSP1-19 2A, Etramp 5 Ag1 His var 3, MSP1-19 2B, Etramp 5 Ag1 His var 2, MSP2 [15-46b], MSP2 [5-36A], ACS5 Ag 3, PfMSP1_19, MSP3 FVO, Var2CSA, SE36/SERA 5 (T), HSP40 Ag 3, GLURP R2, Rh4.2_2030, and MSP2 CH150/9) that distinguish individuals from these two regions. Multivariable linear regression models predicted age and transmission intensity as factors that highly affect antibody reactivity to most antigens in our panel. Gene expression levels differ with transmission intensity More genes were differentially expressed during infection (D0) compared to convalesces (D7 and D21). Comparison of the DEGs between the two sites show that more genes were highly expressed in low transmission area compared to the high transmission area at D0. In the high transmission area, the DEGs enriched in gene ontology (GO) modules related to B cell and surface signature, T cell development and activation, platelet activation-actin binding, enriched cell cycle, and regulation of transcription and transcription factor modules, were up-regulated. In the low transmission area, there was DEGs in modules associated with cell cycle and transcription, immune activation- generic cluster, E2F1 targets, plasma cell surface signature, immunoglobulins, enriched monocytes, enriched NK cells, platelet activation, enriched neutrophils, enriched activated dendritic cells, NK cell surface signature, chemokine and inflammatory molecules in myeloid cells, Golgi membrane and TBA modules, were up-regulated. Cellular deconvolution revealed an increased proportion of neutrophils cell type in both high and low transmission areas, with decreased CD4 naïve, CD8, B-cells and T-follicular cells, during infection compared to convalescence in both high and low transmission. Our data identified transcription patterns that are distinguish by malaria transmission intensity, where most genes highly expressed in the high transmission area are those involved in adaptive immune response. While genes highly expressed in the low transmission area are those involve in the innate immune response. These data provide insight into molecular and cellular immune response kinetics in natural infection. Conclusion: The findings show that cytokine responses during active malaria infection varies significantly between individuals with differing levels of prior exposure, with individuals from low transmission settings having higher levels of pro-inflammatory cytokines. However, these differences are transient and do not persist during recovery. Whereas antibodies levels remained relatively stable across the timepoints for most antigens in our panel. We show that models trained to capture distinct antibody response patterns predicted 17 antibody responses that are key in distinguishing between individuals from different intensities. Given the important role that exposure plays in the acquisition of immunity these could be useful antigens as possible targets of protective immunity and provides clues for potential vaccine candidates that can be prioritized in evaluation. Transcriptomic analysis of whole blood over the course of infection revealed molecular signatures that can provide insights into the protective immune responses against P. falciparum infection. We identified genes whose expression patterns can help differentiate changes during acute P. falciparum infection and convalesces in varying transmission intensity. Taken together, this study predicts humoral and cellular signatures associated with the acquisition of naturally acquired immunity that can fairly distinguish individuals from two distinct transmission areas based on their immune profile | en_US |
| dc.identifier.uri | http://ugspace.ug.edu.gh:8080/handle/123456789/42150 | |
| dc.language.iso | en | en_US |
| dc.publisher | University Of Ghana | en_US |
| dc.subject | Kinetics | en_US |
| dc.subject | Diversity | en_US |
| dc.subject | Immune | en_US |
| dc.subject | Acute | en_US |
| dc.subject | Plasmodium | en_US |
| dc.subject | Falciparum | en_US |
| dc.title | Mapping The Kinetics And Diversity Of Adaptive Immune Responses In Children Over The Course Of An Acute Plasmodium Falciparum Infection | en_US |
| dc.type | Thesis | en_US |