Deepak Gaur

International Centre for Genetic Engineering and Biotechnology & Jawaharlal Nehru University · Malaria (ICGEB) & School of Biotechnology

Introduction Bacillus anthracis is the causative agent for the lethal disease anthrax, primarily affecting animals and humans in close contact with an infected host. The pathogenicity of B. anthracis is attributed to the secreted exotoxins and their outer capsule. The host cell-binding exotoxin component “protective antigen” (PA) is reported to be...

Plasmodium falciparum Cysteine-Rich Protective Antigen (CyRPA) is a conserved component of an essential erythrocyte invasion complex (RH5/Ripr/CyRPA) and a target of potent cross-strain parasite-neutralizing antibodies. While, naturally acquired human RH5 antibodies have been functionally characterized, there are no similar reports on CyRPA. Thus,...

Coinfection with Plasmodium falciparum and helminths may impact the immune response to these parasites because they induce different immune profiles. We compared the antibody profile between groups of Mozambican individuals defined by P. falciparum and helminth previous exposure and/or current infection.

Plasmodium falciparum, the parasite responsible for severe malaria, develops within erythrocytes. Merozoite invasion and subsequent egress of intraerythrocytic parasites are essential for this erythrocytic cycle, parasite survival and pathogenesis. In the present study, we report the essential role of a novel protein, P. falciparum Merozoite Surfac...

Coinfection with Plasmodium falciparum and helminths may impact the immune response to these parasites since they induce different immune profiles. We studied the effects of coinfections on the antibody profile in a cohort of 715 Mozambican children and adults using the Luminex technology with a panel of 16 antigens from P. falciparum and 11 antige...

The RTS,S/AS01E vaccine has shown consistent but partial vaccine efficacy in a pediatric phase 3 clinical trial using a 3-dose immunization schedule. A fourth-dose 18 months after the primary vaccination was shown to restore the waning efficacy. However, only total IgG against the immunodominant malaria vaccine epitope has been analyzed following t...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Background The evaluation of immune responses to RTS,S/AS01 has traditionally focused on immunoglobulin (Ig) G antibodies that are only moderately associated with protection. The role of other antibody isotypes that could also contribute to vaccine efficacy remains unclear. Here we investigated whether RTS,S/AS01E elicits antigen-specific serum IgA...

Background: Targeting multiple key antigens that mediate distinct P. falciparum erythrocyte invasion pathways is an attractive approach for the development of blood-stage malaria vaccines. However, the challenge is to identify antigen cocktails that elicit potent strain-transcending parasite-neutralizing antibodies efficacious at low IgG concentra...

Plasmodium invasion of red blood cells involves malaria proteins, such as reticulocyte-binding protein homolog 5 (RH5), RH5 interacting protein (RIPR), cysteine-rich protective antigen (CyRPA), apical membrane antigen 1 (AMA1) and rhoptry neck protein 2 (RON2), all of which are blood-stage malaria vaccine candidates. So far, vaccines containing AMA...

Human pathogens need to overcome an elaborate network of host defense mechanisms in order to establish their infection, colonization, proliferation and eventual dissemination. The interaction of pathogens with different effector molecules of the immune system results in their neutralization and elimination from the host. The complement system is on...

Erythrocyte invasion by Plasmodium falciparum is an indispensable step for its blood-stage life cycle and maintenance of its successful transmission to new human hosts. The invasion process is mediated by multiple ligand-receptor interactions and is an attractive step to identify critical invasion ligands that could be developed as malaria vaccine...

Background: Vaccination and naturally acquired immunity against microbial pathogens may have complex interactions that influence disease outcomes. To date, only vaccine-specific immune responses have routinely been investigated in malaria vaccine trials conducted in endemic areas. We hypothesized that RTS,S/A01E immunization affects acquisition of...

Naturally acquired immunity (NAI) to Plasmodium falciparum malaria is mainly mediated by IgG antibodies but the subclasses, epitope targets and effector functions have not been unequivocally defined. Dissecting the type and specificity of antibody responses mediating NAI is a key step toward developing more effective vaccines to control the disease...

Reducing variability of quantitative suspension array assays is key for multi-center and large sero-epidemiological studies. To maximize precision and robustness of an in-house IgG multiplex assay, we analyzed the effect of several conditions on variability to find the best combination. The following assay conditions were studied through a fraction...

Antigen-specific log10MFI levels of positive control serial dilutions for all assay conditions and antigens analyzed. Spaghetti plots represent examples of positive control serial dilution MFIs against different antigens and in different assay conditions: Antigen-bead coupling (stock vs. several), sample predilution (stock vs. daily), temperature o...

Median absolute deviation (MAD) of log10MFI of positive control serial dilutions for each assay condition and antigen. Conditions analyzed were: Antigen-bead coupling (stock vs. several), sample predilution (stock vs. daily), temperature of incubation of samples with antigen-beads (22°C vs. 37°C), plate washing (automatic vs. manual) and operator e...

Bland-Altman plots representing the differences of positive control replicates against its mean for all antigens. Dashed blue lines show the 95% confidence interval of the differences. (PDF)

Example of plate design. Each plate included nine subject samples in 4 serial dilutions with duplicates in alternate positions (M1-M9, in blue), a positive control in 8 serial dilutions, with replicates in alternate positions (PosCtrl, in red), and three blanks with multiplex antigen-coupled beads (Blanks, in yellow). (PDF)

Fractional factorial design of the qSAT experiments. The assay conditions analyzed were coupling of the antigens to beads (stock vs. several), sample predilution (stock, vs. daily), temperature of incubation of samples with antigen-beads (22°C vs. 37°C), plate washing (manual vs. automatic) and operator expertise (expert vs. apprentice). (XLSX)

Study dataset. Data file with the variables described as follows: plate; type, multiplex (mp) or singleplex (sp); antigen, the antigen analysed; Sample Type, Blank, Positive (positive controls), Standard (singleplex) or Subject; Sample Dil, number of sample dilution for each sample type; well, well on each plate; Dilution, dilution factor; Bead, co...

Background: The quantitative suspension array technology (qSAT) is a useful platform for malaria immune marker discovery. However, a major challenge for large sero-epidemiological and malaria vaccine studies is the comparability across laboratories, which requires the access to standardized control reagents for assay optimization, to monitor perfo...

Human APOBEC3B (A3B), like other APOBEC3 members, is a cytosine deaminase which causes hypermutation of single stranded genome. Recent studies have shown that A3B is predominantly elevated in multiple cancer tissues and cell lines such as the bladder, cervix, lung, head and neck, and breast. Upregulation and activation of A3B in developing tumors c...

Background: A main criterion to identify malaria vaccine candidates is the proof that acquired immunity against them is associated with protection from disease. The age of the studied individuals, heterogeneous malaria exposure, and assumption of the maintenance of a baseline immune response can confound these associations. Methods: Immunoglobul...

Plasmodium falciparum proteins involved in erythrocyte invasion are main targets of acquired immunity and important vaccine candidates. We hypothesized that anti-parasite immunity acquired upon exposure would limit invasion-related gene (IRG) expression and affect the clinical impact of the infection. 11 IRG transcript levels were measured in P. fa...

Nucleosome assembly in P. falciparum could be the key process in maintaining its genomic integrity as DNA replicates more than once per cell cycle during several stages of its life cycle. Here, we report the functional characterization of P. falciparum chromatin assembly factor 1 (CAF1), which interacts with several proteins namely PfCAF2, Histones...

Epstein–Barr virus (EBV) is a necessary cause of endemic Burkitt lymphoma (eBL), while the role of Plasmodium falciparum in eBL remains uncertain. This study aimed to generate new hypotheses on the interplay between both infections in the development of eBL by investigating the IgG and IgM profiles against several EBV and P. falciparum antigens. Se...

Background & objectives: Balaghat district in Central India is a highly malarious district where both Plasmodium falciparum and P. vivax are prevalent. In this district, the persistence of malaria was on an increase and not responsive to intervention measures even though there was no drug resistance. This study was undertaken by conducting mass sc...

Background: Crucial gaps in our understanding of P. vivax reticulocyte invasion and protective immunity have hampered development of vivax vaccines. P. vivax exclusively invades reticulocytes that is mediated by the P. vivax reticulocyte binding proteins (PvRBPs) specifically PvRBP2c and PvRBP1a. Vivax infections in Duffy-null individuals have sug...

This chapter reviews the current status of efforts to develop vaccines against malaria parasites and discusses the challenges and potential ways forward. Mortality due to malaria is primarily attributed to P. falciparum infections and occurs mainly in children residing in malaria-endemic regions of Africa. Pregnant women are also uniquely susceptib...

This chapter focuses primarily on the erythrocyte-invasive properties of the two human malaria parasites, P. falciparum and P. vivax. Invasion of erythrocytes by Plasmodium merozoites is an intricate biological process that is interwoven between different physiological steps and requires a cascade of specific ligand–receptor interactions at the par...

Erythrocyte invasion by Plasmodium falciparum merozoites is central to blood-stage infection and malaria pathogenesis. This intricate process is coordinated by multiple parasite adhesins that bind erythrocyte receptors and mediate invasion through several alternate pathways. P. falciparum expresses 2700 genes during the blood-stages, of which the i...

Eukaryotic Armadillo (ARM) repeat proteins are multifaceted with prominent roles in cell-cell adhesion, cytoskeletal regulation and intracellular signaling among many others. One such ARM repeat containing protein, ARM Repeats Only (ARO), has recently been demonstrated in both Toxoplasma (TgARO) and Plasmodium (PfARO) parasites to be targeted to th...

PfARO antibodies do not exhibit invasion inhibitory activity. (TIF)

Description of supplementary methods and figure legends (S1 Fig, S2 Fig, S3 Fig). (DOC)

PfARO does not exhibit erythrocyte binding activity. (TIF)

List of Unique Peptides generated from the Mass Spectrometric analysis (LC-MS) of the trypsin digested recombinant PfARO protein (monomeric band and dimeric band). (XLS)

Mass spectrometric identification of native PfARO from immunoprecipitation elutes using specific antibodies. (XLS)

Specificity of antibodies raised against recombinant rPfARO. (TIF)

Plasmodium falciparum is the causative organism for the most severe form of malaria among humans. The clinical symptoms are accredited to the asexual stage of parasite life cycle, involving merozoite invasion of erythrocyte, development and re-invasion into the new erythrocyte. Interaction of parasite proteins present on the surface or secreted fro...

Significance Plasmodium falciparum reticulocyte binding-like homologous protein 5 (PfRH5) is a leading blood-stage malaria vaccine candidate that elicits potent strain-transcending invasion inhibitory antibodies. However, it lacks both transmembrane domains and a GPI-anchor and is thus anchored to the merozoite surface through an unknown mechanism....

Plasmodium falciparum reticulocyte binding-like homologous protein 5 (PfRH5) is an essential merozoite ligand that binds with its erythrocyte receptor, Basigin. PfRH5 is an attractive malaria vaccine candidate as it is expressed by a wide number of P. falciparum strains, cannot be genetically disrupted and exhibits limited sequence polymorphisms. V...

A Plasmodium falciparum chimeric protein, PfMSP-Fu24, was constructed by genetically coupling immunodominant, conserved regions of two merozoite surface proteins, the 19-kDa region C-terminal region of merozoite surface protein 1 (PfMSP-119) and an 11-kDa conserved region of merozoite surface protein 3 (PfMSP-311), to augment the immunogenicity pot...

Malaria remains a major health problem worldwide. All clinical symptoms of malaria are attributed to the asexual blood stages of the parasite life cycle. Proteins resident in apical organelles and present on the surface of P. falciparum merozoites are considered promising candidates for the development of blood stage malaria vaccines. In the presen...

Host cell invasion by Plasmodium falciparum requires multiple molecular interactions between host receptors and parasite ligands. A family of parasite proteins, which contain the conserved thrombospondin structural repeat motif (TSR),has been implicated in receptor binding during invasion. In this study we have characterized the functional role of...

Blood-stage malaria vaccines that target single Plasmodium falciparum antigens involved in erythrocyte invasion have not induced optimal protection in field trials. Blood-stage malaria vaccine development has faced two major hurdles, antigenic polymorphisms and molecular redundancy, which have led to an inability to demonstrate potent, strain-trans...

Invasion of erythrocytes by Plasmodium merozoites is a complex process that is mediated by specific molecular interactions. Here, we review recent studies on interactions between erythrocyte binding antigens (EBA) and PfRH proteins from the parasite and erythrocyte receptors involved in invasion. The timely release of these parasite ligands from in...

The ligands that pathogens use to invade their target cells have often proven to be good targets for vaccine development. However, Plasmodium falciparum has redundant ligands that mediate invasion of erythrocytes. The first requirement for the development of a successful ligand-blocking malaria vaccine is the demonstration that antibodies induced t...

Erythrocyte invasion by Plasmodium merozoites is a complex, multistep process that is mediated by a number of parasite ligand-erythrocyte receptor interactions. One such family of parasite ligands includes the P. falciparum reticulocyte binding homologue (PfRH) proteins that are homologous with the P. vivax reticulocyte binding proteins and have be...

Malaria is a global health problem and the need for a vaccine that could prevent millions of deaths annually cannot be further justified. A number of strategies have been adopted in the pursuit of making a successful malaria vaccine including the use of blood stage antigens which would primarily target the merozoite and prevent its replication thro...

Plasmodium falciparum can invade erythrocytes by redundant receptors, some of which have variable expression. A P. falciparum clone Dd2 requiring erythrocyte sialic acid for invasion can be switched to a sialic acid-independent progeny clone Dd2NM by growing the Dd2 clone with neuraminidase-treated erythrocytes. The RH4 gene is transcriptionally up...

Some human malaria Plasmodium falciparum parasites, but not others, also cause disease in Aotus monkeys. To identify the basis for this variation, we crossed two clones that differ in Aotus nancymaae virulence and mapped inherited traits of infectivity to erythrocyte invasion by linkage analysis. A major pathway of invasion was linked to polymorphi...

Compartmentalization of proteins into subcellular organelles in eukaryotic cells is a fundamental mechanism of regulating complex cellular functions. Many proteins of Plasmodium falciparum merozoites involved in invasion are compartmentalized into apical organelles. We have identified a new merozoite organelle that contains P. falciparum rhomboid-1...

Plasmodium falciparum invasion of human erythrocytes involves several parasite and erythrocyte receptors that enable parasite invasion by multiple redundant pathways. A key challenge to the development of effective vaccines that block parasite infection of erythrocytes is identifying the players in these pathways and determining their function. Inv...

The Plasmodium falciparum clone, Dd2, that requires sialic acid for invasion can switch to a sialic acid independent pathway, Dd2(NM). To elucidate the molecular basis of the switch in invasion phenotype of Dd2 to Dd2(NM), we performed expression profiling of the parasites using an oligonucleotide microarray and real-time RT-PCR. We found that four...

Proteins containing the DHHC motif have been shown to function as palmitoyl transferases. The palmitoylation of proteins has been shown to play an important role in the trafficking of proteins to the proper subcellular location. Herein, we describe a protein containing both ankyrin domains and a DHHC domain that is present in the Golgi of late schi...

Bovine pancreatic ribonuclease (RNase A) is one of the most well studied enzymes of the ribonuclease family, unlike its human counterpart, the human pancreatic ribonuclease (HPR), whose physiological role in the body is not clearly understood. Human pancreatic ribonuclease consists of 128 amino acids and the main residues located in the active site...

Malaria parasites must recognise and invade different cells during their life cycle. The efficiency with which Plasmodium falciparum invades erythrocytes of all ages is an important virulence factor, since the ability of the parasite to reach high levels of parasitemia is often associated with severe pathology and morbidity. The merozoite invasion...

Plasmodium falciparum invades erythrocytes through multiple ligand-receptor interactions, with redundancies in each pathway. One such alternate pathway is the trypsin-resistant pathway that enables P. falciparum to invade trypsin-treated erythrocytes. Previous studies have shown that this trypsin-resistant pathway is dependent on glycophorin B, as...

Human pancreatic ribonuclease (HPR) and bovine seminal ribonuclease (BS-RNase) exhibit significantly higher activity against double stranded RNA (dsRNA), compared to RNase A. The high dsRNA cleavage activity of BS-RNase, in part, has been attributed to glycine residues at positions 38 and 111. HPR possesses a glycine residue at position 38, whereas...

Restrictocin, a member of the fungal ribotoxin family, specifically cleaves a single phosphodiester bond in the 28S rRNA and potently inhibits eukaryotic protein synthesis. Residues Tyr47, His49, Glu95, Phe96, Pro97, Arg120, and His136 have been predicted to form the active site of restrictocin. In this study, we have individually mutated these ami...

Mammalian ribonucleases interact very strongly with the intracellular ribonuclease inhibitor (RI). Eukaryotic cells exposed to mammalian ribonucleases are protected from their cytotoxic action by the intracellular inhibition of ribonucleases by RI. Human pancreatic ribonuclease (HPR) is structurally and functionally very similar to bovine RNase A a...