Dynamic Palmitoylation of Red Cell Membrane Proteins Governs Susceptibility to Invasion by the Malaria Parasite, Plasmodium falciparum

An immuno-inflammatory profiling of asymptomatic individuals in a malaria endemic area in Uganda

Malaria caused by Plasmodium falciparum leads to the destruction of red blood cells (RBCs). A better understanding of how naturally immune individuals control infections should be valuable for future vaccine studies. Antibodies against RBCs and RBC surface antigens were measured together with different inflammatory markers in healthy adults living in a malaria endemic area of Uganda and compared to Swedish healthy adults. Antibodies binding to RBCs were clearly elevated in Ugandans compared to Swedish samples, and for RBC surface antigens the Ugandans had higher levels of antibodies against JMH, but not against Cromer or Kell. Twenty-eight percent of the Ugandans were PCR-positive for P. falciparum, and these had higher levels of IgG against parasite extract and more inhibition in functional growth/invasion assays, but levels of antibodies against RBC, RBC surface antigens, results from Direct Antiglobulin Tests (DAT) and indirect antiglobulin tests were similar when compared with PCR-negative individuals. When inflammatory markers (α-1-antitrypsin, haptoglobin, orosomucoid/α-1-acid glycoprotein, CRP, IgG, IgA and IgM) were measured there were in general almost no signs of inflammation except for clearly elevated levels of IgG. Some had low levels of haptoglobin and for orosomucoid more than half of the individuals had clearly reduced levels. There was no correlation between the inflammatory markers and PCR-positivity, antibodies against RBCs or parasites. In conclusion, for healthy adults living in a malaria endemic area, there was a clear presence of antibodies against RBCs in parallel with high levels of IgG and almost no signs of inflammation, even though many individuals were carrying parasites.

Identification of a De Novo Peptide against Palmitoyl Acyltransferase 6 to Block Survivability and Infectivity of Leishmania donovani

Palmitoylation is an essential post-translational modification in Leishmania donovani, catalyzed by enzymes called palmitoyl acyl transferases (PATs) and has an essential role in virulence. Due to the toxicity and promiscuity of known PAT inhibitors, identification of new molecules is needed. Herein, we identified a specific novel de novo peptide inhibitor, PS1, against the PAT6 Leishmania donovani palmitoyl acyl transferase (LdPAT6). To demonstrate specific inhibition of LdPAT6 by PS1, we employed a bacterial orthologue system and metabolic labeling-coupled click chemistry where both LdPAT6 and PS1 were coexpressed and displayed palmitoylation suppression. Furthermore, strong binding of the LdPAT6-DHHC domain with PS1 was observed through analysis using microscale thermophoresis, ELISA, and dot blot assay. PS1 specific to LdPAT6 showed significant growth inhibition in promastigotes and amastigotes by expressing low cytokines levels and invasion. This study reveals discovery of a novel de novo peptide against LdPAT6-DHHC which has potential to block survivability and infectivity of L. donovani.

Generation of red blood cells from stem cells: Achievements, opportunities and perspectives for malaria research

Parasites of the genus Plasmodium that cause malaria survive within humans by invasion of, and proliferation within, the most abundant cell type in the body, the red blood cell. As obligate, intracellular parasites, interactions between parasite and host red blood cell components are crucial to multiple aspects of the blood stage malaria parasite lifecycle. The requirement for, and involvement of, an array of red blood cell proteins in parasite invasion and intracellular development is well established. Nevertheless, detailed mechanistic understanding of host cell protein contributions to these processes are hampered by the genetic intractability of the anucleate red blood cell. The advent of stem cell technology and more specifically development of methods that recapitulate in vitro the process of red blood cell development known as erythropoiesis has enabled the generation of erythroid cell stages previously inaccessible in large numbers for malaria studies. What is more, the capacity for genetic manipulation of nucleated erythroid precursors that can be differentiated to generate modified red blood cells has opened new horizons for malaria research. This review summarises current methodologies that harness in vitro erythroid differentiation of stem cells for generation of cells that are susceptible to malaria parasite invasion; discusses existing and emerging approaches to generate novel red blood cell phenotypes and explores the exciting potential of in vitro derived red blood cells for improved understanding the broad role of host red blood cell proteins in malaria pathogenesis.

S NM, Ahmad S, Pati S, Singh S. Studying the Rationale of Fire Ant Sting Therapy Usage by the Tribal Natives of Bastar Revealed Ant Venom-Derived Peptides with Promising Anti-Malarial Activity

Prevailing drug resistance in malaria imposes the major roadblock for the existing interventions necessitating the timely need to search for alternative therapies. Ants in Solenopsis spp, termed 'Fire ants', are well known for their aggressive behavior, which leads to the release of toxic venom. Notably, the tribal natives of the malaria-laden densely forested Bastar region, Chhattisgarh, India, use fire ant sting-based therapy to cure malaria-like high fever. Inspired by this, we have collected the fire ants from the forest of Bastar and extracted peptide and alkaloid fractions from ant venom using HPLC and analyzed them by LC/MS-based applications. Evaluation of the anti-malarial efficacy of these peptide fractions demonstrated a significant reduction in the growth of Plasmodium falciparum (Pf 3D7) in vitro, whereas the alkaloid fraction showed a negligible effect. in vitro hemolytic activity confirmed the venom peptide fraction to be non-hemolytic. Additionally, the venom peptide fraction is purely non-toxic to HepG2 cells. Anti-malarial efficiency of the same in Plasmodium berghei ANKA infected mice models showed a drastic reduction in parasitemia representing promising anti-malarial activity. Overall, our study has unraveled the scientific rationale underlying fire ant sting therapy used as a tribal naturotherapy for curing malaria-like fever, thus, introducing a way forward to develop nature-inspired anti-malarial chemotherapeutics.