Malaria Pathogenesis in young children and vaccine discovery

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications, trials & patents

Abstract

In FY2022, we reported human and animal studies to investigate malaria immunology and pathogenesis, and malaria vaccine development. Highlighted in this years summary are results from our publications. 1. Zhu D, Dai W, Srinivasan P, McClellan H, Braden D, Allee-Munoz A, Gonzales-Hurtado PA, Miller LH, Duffy PE. Characterization of AMA1-RON2L complex with native gel electrophoresis and capillary isoelectric focusing. 2021. Electrophoresis. Oct 22. AMA1-RON2L (L is referred to as the loop region of RON2 peptide) complex is a promising blood stage malaria vaccine candidate, as preclinical studies with Freund's adjuvant have indicated complete protection against lethal challenge in mice and superior protection against virulent infection in Aotus monkeys. To prepare for clinical trials of the AMA1-RON2L complex, identity and integrity of the candidate vaccine must be assessed, and characterization methods must be carefully designed to not dissociate the delicate complex during evaluation. In this study, we developed a native Tris-glycine gel method to separate and identify the AMA1-RON2L complex, which was further identified and confirmed by Western blotting using anti-AMA1 monoclonal antibodies (mAbs 4G2 and 2C2) and anti-RON2L polyclonal Ab coupled with mass spectrometry. The formation of complex was also confirmed by Capillary Isoelectric Focusing (cIEF). A short-term (48 h and 72 h at 4C) stability study of AMA1-RON2L complex was also performed. Results indicated the complex was stable for 72 h at 4C. Native Tris-glycine gel separation/Western blotting coupled with mass spectrometry and cIEF can fully characterize the identity and integrity of the AMA1RON2L complex, and provide useful quality control data for subsequent clinical trials. 2. Gonalves BP, Prez-Caballero R, Barry A, Gaoussou S, Lewin A, Issiaka D, Keita S, Diarra BS, Mahamar A, Attaher O, Narum DL, Kurtis JD, Dicko A, Duffy PE, Fried M. Natural history of malaria infections during early childhood in twins. 2022. Journal of Infectious Diseases. Jul 18. The frequency and clinical presentation of malaria infections show marked heterogeneity in epidemiological studies. However, deeper understanding of this variability is hampered by the difficulty in quantifying all relevant factors. We reported the history of malaria infections in twins, who are exposed to the same in utero milieu, share genetic factors and are similarly exposed to vectors. Data were obtained from a Malian longitudinal birth cohort. Samples from 25 twin pairs were examined for malaria infection and antibody responses. Bayesian models were developed on the number of infections during follow-up. In 16/25 pairs, both children were infected and often developed symptoms. In 8/25 pairs, only one twin was infected, but usually only once or twice. Statistical models suggest this pattern is not inconsistent with twin siblings having the same underlying infection rate. In a pair with discordant hemoglobin genotype, parasite densities were consistently lower in the child with hemoglobin AS, but antibody levels were similar. By using a novel design, we described residual variation in malaria phenotypes in naturally-matched children and confirm the important role of environmental factors, as suggested by the between twin pair heterogeneity in malaria history. 3. Mahamar A, Gonzales-Hurtado PA, Morrison R, Boone R, Attaher O, Diarra BS, Gaossou S, Issiaka D, Dicko A, Duffy PE, Fried M. Plasma biomarkers of hemoglobin loss in Plasmodium falciparum-infected children identified by quantitative proteomics. 2021. Blood. Dec 6. Anemia is common among young children infected with Plasmodium falciparum and severe malarial anemia (SMA) is a major cause of their mortality. Two major mechanisms cause malarial anemia: hemolysis of uninfected as well as infected erythrocytes and insufficient erythropoiesis. In a longitudinal birth cohort in Mali, we commonly observed marked hemoglobin reductions during P. falciparum infections with a small proportion that progressed to SMA. We sought biomarkers of these processes using quantitative proteomic analysis on plasma samples from 9 P. falciparum-infected children, comparing those with reduced hemoglobin (with or without SMA) versus those with stable hemoglobin. We identified higher plasma levels of circulating 20S proteasome and lower insulin-like growth factor-1 (IGF-1) levels in children with reduced hemoglobin. We confirmed these findings in independent ELISA-based validation studies of subsets of children from the same cohort (20S proteasome, N = 71; IGF-1, N = 78). We speculate that circulating 20S proteasome plays a role in digesting erythrocyte membrane proteins modified by oxidative stress, resulting in hemolysis, whereas decreased IGF-1, a critical factor for erythroid maturation, might contribute to insufficient erythropoiesis. Quantitative plasma proteomics identified soluble mediators that may contribute to the major mechanisms underlying malarial anemia.