José A Stoute

• Faculty Member at Penn State Hershey Medical Center and Penn State College of Medicine

Malaria, which infected more than 240 million people and killed around six hundred thousand only in 2021, has reclaimed territory after the SARS-CoV-2 pandemic. Together with parasite resistance and a not-yet-optimal vaccine, the need for new approaches has become critical. While earlier, limited, studies have suggested that malaria parasites are a...

Plasmodium falciparum malaria killed 451,000 people in 2017. Merozoites, the stage of the parasite that invades RBCs, are a logical target for vaccine development. Treatment with the protease inhibitor E64 followed by filtration through a 1.2 μm filter is being used to purify merozoites for immunologic assays. However, there have been no studies to...

The complement system consists of a complex cascade of zymogens that leads to the formation of opsonins (predominantly C3b and C4b) that promote phagocytosis and the insertion of the membrane attack complex into the membranes, resulting in lysis. It constitutes one of the first lines of defense against pathogens as it does not require prior maturat...

The role of complement in the immunity against malaria has been severely understudied. As a result, we know very little about this subject. Antibodies play an important role in suppressing parasitemia and could work by any or a combination of several mechanisms: inhibition of sporozoite invasion of hepatocytes, by blocking merozoite invasion of red...

Activation of the classical pathway of complement, mediated by immune complexes, is very well-documented in malaria. In addition, several of the breakdown products that are produced upon rupture of malaria-infected erythrocytes, including hemin and the digestive vacuole, activate the alternative pathway of complement. Evidence for complement activa...

Plasmodium falciparum is responsible for the deaths of hundreds of thousands of children every year. Most of these deaths are the result of complications such as severe malarial anemia (SMA). There are now considerable data that suggest that complement plays a role in the development of anemia during malaria infection by opsonization of uninfected...

The extensive redundancy in the use of invasion ligands by Plasmodium falciparum, and its unique ability to switch between invasion pathways have hampered vaccine development. P. falciparum strains Dd2 and W2mef have been shown to change from sialic acid (SA)-dependent to SA-independent phenotypes when selected on neuraminidase-treated erythrocytes...

Plasmodium falciparum malaria is responsible for the deaths of nearly 500,000 people each year. Much attention has been paid to antibody and cellular mechanisms of immunity against this pathogen. By contrast, the role that the complement system plays in immunity and pathogenesis in this infection is not very well recognized or understood. Based on...

One of the largest single sources of epilepsy in the world is produced as a neurological sequela in survivors of cerebral malaria. Nevertheless, the pathophysiological mechanisms of such epileptogenesis remain unknown and no adjunctive therapy during cerebral malaria has been shown to reduce the rate of subsequent epilepsy. There is no existing ani...

The development of resistance to insecticides by the vector of malaria and the increasingly faster appearance of resistance to antimalarial drugs by the parasite can dangerously hamper efforts to control and eradicate the disease. Alternative ways to treat this disease are urgently needed. Here we evaluate the in vitro effect of direct current (DC)...

Stability of the Power Source EC105. (TIF)

Standardization of the voltage to be applied. Infected erythrocytes were exposed to different voltages of DC electric fields and their growth assesed 24 hours later. (TIFF)

Characterization of the five output voltage levels of the resistive voltage divider at different input voltages. (TIF)

Standardization of time of exposure. Infected erythrocytes were exposed to 25 V DC electric fields for different times and their growth assesed 24 hours later. (TIFF)

Fold change of growth in the second cell cycle of the different electrically stimulated groups of parasites with the use of different signal transduction inhibitors. The fold change in growth from 24 to 48 hours was calculated as the parasitemia after 24 h divided by the initial parasitemia at the time of plating. Data represented are the mean ± SE...

A model of antibody and complement-mediated enhancement of RBC invasion by Plasmodium merozoites, see discussion. 1) In the absence of complement, such as via heat inactivation of serum, the merozoites depend on interactions between the RBC receptors and the parasite ligands. Antibody (Ab) directed against merozoites may have inhibitory effect, and...

Plasmodium falciparum malaria is a deadly pathogen. The invasion of red blood cells (RBCs) by merozoites is a target for vaccine development. Although anti-merozoite antibodies can block invasion in vitro, there is no efficacy in vivo. To explain this discrepancy we hypothesized that complement activation could enhance RBC invasion by binding to th...

Plasmodium falciparum infects approximately 500 million individuals each year. A small but significant number of infections lead to complications such as cerebral malaria (CM). CM is associated with myelin damage and neurological deficits in survivors, and iron status is thought to impact the outcome of infection. We evaluated whether a mouse model...

ABSTRACT Background. Plasmodium falciparum invades human erythrocytes using an array of ligands which interact with several receptors including sialic acid (SA), complement receptor 1 (CR1), and basigin. We hypothesized that in malaria-endemic areas, parasites vary invasion pathways under immune pressure. Therefore, invasion mechanisms of clinical...

Aims: Immune-mediated mechanism, such as deposition of complement (C3b) on erythrocytes leading to enhanced receptor-mediated uptake by macrophages has been proposed to contribute partly to the destruction of non-infected cells leading to anaemia. The extent of complement deposition on RBC (red blood cells) may therefore influence an individual's r...

Plasmodium falciparum invades human erythrocytes using an array of ligands which interact with several receptors including sialic acid (SA), complement receptor 1 (CR1), and basigin. We hypothesized that in malaria-endemic areas, parasites vary invasion pathways under immune pressure. Therefore, invasion mechanisms of clinical isolates collected fr...

Malaria is responsible for close to1 million deaths each year, mostly among African children. Red blood cells (RBCs) of children with severe malarial anemia show loss of complement regulatory proteins such as complement receptor 1 (CR1). We carried out this study to identify socio-economic, environmental, and biological factors associated with the...

A computer controlled microwave exposure system and specialized applicators were constructed for facilitating accurate observations of microwave radiation effects on uninfected and infected biological tissue in vitro and in vivo under different electromagnetic modalities and exposure configurations. Modeling of these new applicator designs was done...

A new strategy was developed to synthesize 1,2-disubstituted 4-quinolones in good yield starting from 1,3-bisaryl-monothio-1,3-diketone substrates. The synthesized compounds were evaluated for antimalarial activity using Plasmodium falciparum strains. All compounds, except two, showed good activity. Of these, seven compounds exhibited excellent ant...

Complement is activated during malaria infection, but there is little evidence that it benefits the host. On the contrary, growing evidence points to the central role of complement activation in the pathogenesis of complicated malaria. Recent evidence suggests a critical role for C5a and the membrane attack complex in the pathogenesis of cerebral m...

Clinical manifestations of Plasmodium falciparum infection are caused by invasion of erythrocytes by the malaria parasite, a process which is mediated by multiple receptor-ligand interactions. Antibodies against some parasite ligands have been shown to significantly inhibit parasite growth in vitro, demonstrating that these interactions may be good...

Aims: Erythrocyte complement regulatory proteins, complement receptor 1 (CR1) and decay accelerating factor (CD55) protect red blood cells (RBCs) from complement mediated damage by controlling complement activation cascade and potentially protect RBCs from complement mediated damage that may occur when immune complexes are Research Article Internat...

Objective: Internet-based telemedicine has the potential to alleviate the problem of limited access to healthcare in developing countries. The Mashavu project aims to deploy kiosks that transmit health data and pictures from patients in underdeveloped countries who have no immediate access to healthcare to clinics for analysis by trained personnel...

Invited Commentary on ‘Efficacy of preerythrocytic and blood-stage malaria vaccines can be assessed in small sporozoite challenge trials in human volunteers’, Roestenberg et al. Journal of Infectious Diseases 2012. For decades a small group of laboratories have been quietly but steadily testing experimental malaria vaccines in human volunteers and...

Lack of an adequate animal model of Plasmodium falciparum severe malarial anemia (SMA) has hampered the understanding of this highly lethal condition. We developed a model of SMA by infecting C57BL/6 mice with P. chabaudi followed after recovery by P. berghei infection. P. chabaudi/P. berghei-infected mice had an initial 9- to 10-day phase of relat...

In February 2011, a rare case of congenital Plasmodium vivax malaria was diagnosed in a temperate region of Central China. An infant developed intermittent fever 20 days after delivery. Since this occurred during the non-transmission winter season in a low malaria endemic region and the infant's mother did not have a clear malaria history or showed...

Given the ability of erythrocytes to bind immune complexes (ICs), we postulated that they can serve a dual role during inflammatory or infectious processes. Erythrocytes could restrict stimulation of macrophages by free ICs by binding C3b-opsonized ICs via their complement receptor 1 (CR1). Conversely, IC-loaded erythrocytes could stimulate macroph...

Plasmodium falciparum malaria is an intracellular parasite that is transmitted by Anopheles mosquitoes. It is responsible for approximately 1 million deaths per year. Most deaths occur as a result of complications such as severe anaemia or cerebral malaria (coma). The complement receptor 1 is a key complement regulator found on the surface of red c...

A majority of Plasmodium falciparum strains invade erythrocytes through interactions with sialic acid (SA) on glycophorins. However, we recently reported that complement receptor 1 (CR1) is a SA-independent invasion receptor of many laboratory strains of P. falciparum. To determine the role of CR1 in erythrocyte invasion among P. falciparum field i...

Fc gamma receptor IIIA (CD16/FcRIIIA) on monocytes/macrophages may play an important role in the pathogenesis of severe malarial anemia (SMA) by promoting phagocytosis of IgG-coated uninfected red cells and by allowing the production of tumor necrosis factor alpha (TNF-) upon cross-linking by immune complexes (ICs). However, not much is known about...

Speckled pattern of CR1 in intact red cells is eliminated by treatment with trypsin. (A) Cross-section of intact red cells, (B) Cross-section of trypsinized red cells. (0.28 MB DOC)

Merozoite (blue) attached to the surface of a neuraminidase-treated red cell with aggregation of CR1 (green) around the merozoite. This video corresponds to supplementary Figure S1B. (0.63 MB MOV)

Merozoite (blue) on the surface of an untreated red cell with increased CR1 (green) intensity at one end of the merozoite. This video corresponds to supplementary Figure S1C. (0.52 MB MOV)

Invasion inhibition by anti-CR1 and sCR1 remains stable over a wide range of parasitemia. Enriched trophozoites/schizonts were added to 2% hematocrit culture at varying concentrations in duplicate wells of a 96-well plate while maintaining the concentrations of inhibitors constant. Invasion rate in the presence of inhibitors (shown on the y axis on...

Effect of Anti-CR1 and sCR1 on invasion of P. falciparum wild strains. (0.04 MB DOC)

Merozoite (blue) attached to the surface of a neuraminidase-treated red cell with aggregation of CR1 (green)between the merozoite and the red cell. This video corresponds to supplementary Figure S1A. (2.04 MB MOV)

More representative examples of interaction between merozoites and CR1 on the surface of treated and untreated (control) red cells. Merozoites (blue), CR1 (green), and glycophorin A (red). DIC = Differential interference contrast. (1.96 MB DOC)

Merozoite (blue) attached to CR1 (green) on the surface of a red cell. This video corresponds to control in Figure 4, main text. (1.15 MB MOV)

Merozoite (blue)on the surface of a neuraminidase-treated red cell with aggregation of CR1 (green) around the merozoite. This video corresponds to neuraminidase-treated panel in Figure 4 of the main text. (1.30 MB MOV)

Merozoite (blue) on the surface of an untreated red cell with increased CR1 (green) intensity around the merozoite. This video corresponds to supplementary Figure S1D. (1.20 MB MOV)

Plasmodium falciparum is a highly lethal malaria parasite of humans. A major portion of its life cycle is dedicated to invading and multiplying inside erythrocytes. The molecular mechanisms of erythrocyte invasion are incompletely understood. P. falciparum depends heavily on sialic acid present on glycophorins to invade erythrocytes. However, a sig...

Fc gamma receptor IIIA (CD16/Fc gamma RIIIA) on monocytes/macrophages may play an important role in the pathogenesis of severe malarial anemia (SMA) by promoting phagocytosis of IgG-coated uninfected red cells and by allowing the production of tumor necrosis factor alpha (TNF-alpha) upon cross-linking by immune complexes (ICs). However, not much is...

Complement Regulatory Protein Levels, Immune Complex Binding Capacity, and Complement Susceptibility of Red Cells from Children with Sickle Cell Trait or Normal Adult Hemoglobin in a Malaria Endemic Area of Western Kenya Walter Otieno1,2, Joash R. Aluoch4, Benson Estambale2 & José A. Stoute3 1. The US Army Medical Research Unit and the Kenya Med...

Background Severe anemia due to Plasmodium falciparum malaria is a major cause of mortality among young children in western Kenya. The factors that lead to the age-specific incidence of this anemia are unknown. Previous studies have shown an age-related expression of red cell complement regulatory proteins, which protect erythrocytes from autologou...

Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is a potentially important family of immune targets, encoded by an extremely diverse gene family called var. Understanding of the genetic organization of var genes is hampered by sequence mosaicism that results from a long history of non-homologous recombination. Here we have used softwa...

Plasmodium falciparum infection can lead to deadly complications such as severe malaria-associated anaemia (SMA) and cerebral malaria (CM). Children with severe malaria have elevated levels of circulating immune complexes (ICs). To further investigate the quantitative differences in antibody class/subclass components of ICs in SMA and CM, we enroll...

Plasmodium falciparum malaria causes 1-2 million deaths per year. Most deaths occur as a result of complications such as severe anemia and cerebral malaria (CM) (coma). Red cells of children with severe malaria-associated anemia (SMA) have acquired deficiencies in the complement regulatory proteins complement receptor 1 (CR1, CD35) and decay accele...

We report the first trial of candidate malaria vaccine antigen FMP1, a 42kDa fragment from the C-terminus of merozoite surface protein-1 (MSP-1) from the 3D7 strain of Plasmodium falciparum, in an endemic area. Forty adult male and female residents of western Kenya were enrolled to receive 3 doses of either FMP1/AS02A or Imovax rabies vaccine by in...

We present evidence that a parasite with characteristics of Plasmodium vivax is being transmitted among Duffy blood group-negative inhabitants of Kenya. Thirty-two of 4,901 Anopheles gambiae and An. funestus (0.65%) collected in Nyanza Province were ELISA positive for the P. vivax circumsporozoite protein VK 247. All positives were found late in th...

We conducted a phase 1 trial of candidate malaria vaccine RTS,S/AS02A in western Kenya to determine its safety and immunogenicity in healthy adults in an area hyperendemic for malaria. Twenty adults were enrolled and received RTS,S/AS02A (50 microg of RTS,S in 0.5 mL of AS02A) by intramuscular injection on a 0-, 28-, and 178-day schedule. All 60 sc...

Our aim was to evaluate the safety, reactogenicity, and immunogenicity of an investigational malaria vaccine. This was an age-stratified phase Ib, double-blind, randomized, controlled, dose-escalation trial. Children were recruited into one of three cohorts (dosage groups) and randomized in 2:1 fashion to receive either the test product or a compar...

Malaria infection leads to the formation of circulating immune complexes. However, it is unclear whether these complexes play a role in the pathogenesis of complicated Plasmodium falciparum malaria. This study aimed at determining if there are differences in the levels of immune complexes between children with severe malaria-associated anemia and c...

Data from several laboratories suggest that erythrocyte complement-regulatory proteins, in particular complement receptor 1 (CR1), are important in the pathogenesis of severe malaria. Additional studies suggest that the levels of expression of CR1 and the complement regulator CD55 on erythrocytes vary with age, being low in young children and incre...

Malaria infection leads to the formation of circulating immune complexes. However, it is unclear whether these complexes play a role in the pathogenesis of complicated Plasmodium falciparum malaria. This study aimed at determining if there are differences in the levels of immune complexes between children with severe malaria-associated anemia and c...

It has been hypothesized that the African alleles Sl2 and McCb of the Swain-Langley (Sl) and McCoy (McC) blood group antigens of the complement receptor 1 (CR1) may confer a survival advantage in the setting of Plasmodium falciparum malaria, but this has not been demonstrated. To test this hypothesis, children in western Kenya with severe malaria-a...

Severe malaria-associated anemia and cerebral malaria are life-threatening complications of Plasmodium falciparum infection. Red blood cell (RBC) complement regulatory proteins (CRPs) have been implicated in the pathogenesis of both. We sought to determine whether there are age-related changes in the expression of CRPs that could explain the suscep...

Region II of the 175-kDa erythrocyte-binding antigen (EBA-175RII) of Plasmodium falciparum is functionally important in sialic acid-dependent erythrocyte invasion and is considered a prime target for an invasion-blocking vaccine. The objectives of this study were to (i) determine the prevalence of anti-EBA-175RII antibodies in a naturally exposed p...

The Plasmodium falciparum circumsporozoite (CS) protein-based pre-erythrocytic stage vaccine, RTS,S, induces a high level of protection against experimental sporozoite challenge. The immune mechanisms that constitute protection are only partially understood, but are presumed to rely on Abs and T cell responses. In the present study we compared CS p...

Recently conducted trials involving the Plasmodium falciparum circumsporozoite (CS) protein-based RTS,S malaria vaccine yielded unprecedented protection against a challenge with infectious sporozoites (spzs). The RTS,S vaccine induced high titres of CS protein-specific antibodies (Abs) in many of the protected volunteers, but the contribution of th...

Severe anemia is one of the most lethal complications of Plasmodium falciparum malaria. Red blood cells (RBCs) from children with severe malarial anemia are deficient in complement regulatory proteins (CR1 and CD55). A case-control, age- and sex-matched study was carried out to determine whether these deficiencies are acquired or inherited and the...

During 1989–1999, 11 volunteers were immunized by the bites of 1001–2927 irradiated mosquitoes harboring infectious sporozoites of Plasmodium falciparum (Pf) strain NF54 or clone 3D7/NF54. Ten volunteers were first challenged by the bites of Pf-infected mosquitoes 2–9 weeks after the last immunization, and all were protected. A volunteer challenged...

Severe anemia is one of the most lethal complications in children infected with Plasmodium falciparum. The pathogenesis of this anemia is not completely understood. Experimental data from malaria-infected humans and animal models suggest that uninfected red cells have a shortened life span. This study looked for changes in the red cell surfaces of...

A safe and effective malaria vaccine will greatly facilitate efforts to control the global spread of malaria. This paper discusses the conceptual framework for developing malaria vaccines and some of the difficulties that the various approaches face. It emphasizes the role of pre-erythrocytic malaria vaccines, which are designed to protect against...

The malaria sporozoite vaccine candidate RTS,S, formulated with an oil-in-water emulsion plus the immunostimulants monophosphoryl lipid A and the saponin derivative QS21 (vaccine 3), recently showed superior efficacy over two other experimental formulations. Immunized volunteers were followed to determine the duration of protective immune responses...

A vaccine against Plasmodium falciparum malaria is needed now more than ever due the resurgence of the parasite and the increase in drug resistance. However, success in developing an effective malaria vaccine has been elusive. Among pre-erythrocytic antigens, the major antigen coating the surface of the sporozoite, the circumsporozoite protein (CS)...

Candidate malaria vaccines have failed to elicit consistently protective immune responses against challenge with Plasmodium falciparum. NYVAC-Pf7, a highly attenuated vaccinia virus with 7 P. falciparum genes inserted into its genome, was tested in a phase I/IIa safety, immunogenicity, and efficacy vaccine trial in human volunteers. Malaria genes i...

Dr Krotoski could be thanked for reminding those in the readership who are unfamiliar with the life cycle of malaria that relapses due to Plasmodium vivax infection are indeed a consequence of hypnozoites, and not cycling of liver stage parasites per se. However, his comments have no bearing on the immunological issues discussed under either Rajan'...

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The candidate vaccines against malaria are poorly immunogenic and thus have been ineffective in preventing infection. We developed a vaccine based on the circumsporozoite protein of Plasmodium falciparum that incorporates adjuvants selected to enhance the immune response. The antigen consists of a hybrid in which the circumsporozoite protein fused...

The mouse monoclonal antibody 2A10 (immunoglobulin G), which recognizes the (NANP)n repeat of Plasmodium falciparum circumsporozoite surface protein, was used to screen a filamentous phage epitope library expressing random amino acid hexamers. The sequences obtained were TNRNPQ, SNRNPQ, NND-NPQ, SNYNPQ, and QNDNPQ (single-letter amino acid designat...

This article discusses the current organization and doctrine for a medical platoon in an armour-heavy task force in light of experience gained in Operations Desert Shield and Desert Storm. The organization of and doctrine for the use of the platoon is covered first. This is followed by a discussion of how doctrine was modified based on field exerci...