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Historical records, some >3,000 years old, attest to the antiquity of the disease malaria. Using a light microscope, Alphonse Laveran noticed some crescent-shaped bodies among the red blood cells that were almost entirely transparent, save for some pigment inclusions. He recognized that these bodies were alive, and that he was looking at an animal parasite, not a bacterium or a fungus. Subsequently, he examined blood samples from 192 malaria patients: in 148 of these, he found the telltale crescents. Where there were no crescents, there were no symptoms of malaria. He named the parasite Oscillaria malariae and communicated his findings to the Societe Medicale des Hopitaux on 24 December 1880. Although malaria can be induced in a host by the introduction of parasites (called sporozoites) through the bite of an infectious female mosquito, the parasites do not immediately appear in the blood. This was surprising in view of the fact that in 1903 Fritz Schaudinn claimed to have seen sporozoites directly invade erythrocytes. All human malarial agents (Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae) are transmitted through the bite of an infected female anopheline mosquito when she injects sporozoites from her salivary glands during blood feeding. Investigations at the molecular level of enzyme structure, gene sequences, chromosomal arrangements, and transcriptional control will permit an uncovering of the adhesive molecules that mediate cell-cell interactions, determine the mechanisms of protein trafficking, and identify putative drug targets and vaccine candidates.

Malaria-parasitized erythrocytes have increased endothelial adherence due to exposure of previously buried intramembranous sites of band 3. Because sickle erythrocytes also show increased adhesiveness and because the membrane portion of band 3 is aggregated in both types of cells, we examined the role of band 3 in sickle cell adhesiveness. Synthetic peptides derived from the second and third exofacial, interhelical regions of band 3 completely inhibited the abnormal adherence of sickle cells to an endothelial monolayer in a static assay. This effect was observed independently of plasma factors, required micromolar levels of peptide, was sequence-specific, and was found with both L- and D-isomers. The active peptides also inhibited the increased adherence induced by low-dose calcium loading of normal red blood cells. Finally, a monoclonal antibody against an active peptide specifically immunostained a fraction of sickle cells. These findings implicate a role for band 3 in at least one type of sickle cell adhesiveness via the exposure of normally cryptic membrane sites.

The attachment of erythrocytes infected with Plasmodium falciparum to the microvessels of the brain leads to a pathological condition known as cerebral malaria. There are no effective therapeutic means for alleviating this. In this review, Kirkwood Land, Irwin Sherman, Jurg Gysin and Ian Crandall discuss the potential of anti-adhesive peptides and antibodies as a means of treating cerebral malaria. Adhesin proteins on the surface of the parasite-infected red blood cell as well as target cell ligand molecules are discussed in the context of anti-adhesion therapy.

A monoclonal antibody generated against synthetic peptides patterned on amino acids 542-555 of human band 3, designated 1F4, specifically immunostained Plasmodium falciparum-infected erythrocytes and inhibited the cytoadherence of P. falciparum-infected erythrocytes to C32 amelanotic melanoma cells. 1F4 did not recognize intact band 3 protein on immunoblots, however it was reactive towards proteolytic fragments of band 3. The binding region of another murine monoclonal antibody previously reported to recognize the membrane spanning domain of human band 3, designated B6, was found to also recognize residues 542-555, however its properties differed from 1F4. Mab B6 recognized both infected and uninfected red cells, and reacted only with intact band 3 on immunoblots. Mab B6 was without effect on cytoadherence. These results demonstrate that monoclonal antibodies reactive against a common peptide sequence may bind to different conformations of the peptide sequence and suggest that the adherent competency of P. falciparum-infected erythrocytes may result from a change in the surface topography of human band 3 protein.

The cytoadherence of Plasmodium falciparum-infected erythrocytes (FCR-3 line) to human brain capillary endothelial cells (HBEC), C32 amelanotic melanoma cells, and human umbilical vein endothelial cells (HUVEC) was studied. The adhesion of infected red cells was HBEC > amelanotic melanoma > HUVEC. The presence or absence of the adhesive ligands ICAM-1 (CD54 or intercellular adhesion molecule 1), ICAM-2, and CD36 (= glycoprotein IV) was determined for each of these cells by indirect immunofluorescence using the monoclonal antibodies RR1/1, 6D5, and OKM 5/OKM 8, respectively. It appeared that a major ligand for the FCR-3 line of P. falciparum with amelanotic melanoma cells and HBECs was CD36. Binding to HUVECs was very low, presumably due to their lack of expression of CD36. HBECs, because of their ease of in vitro propagation, long-term maintenance of cytoadherent properties, and their high degree of adhesiveness, will be useful for in vitro studies of adherence.

Plasmodium falciparum (human malaria) infections are characterized by the attachment of erythrocytes infected with mature stage parasites to endothelial cells lining the post-capillary venules, a phenomenon known as sequestration. In the human body, the microvessels of the heart, lungs, kidneys, small intestine, and liver are the principal sites of sequestration. Sequestered cells that clog the brain capillaries may reduce blood flow sufficiently so that there is confusion, lethargy, and unarousable coma—cerebral malaria. This review considers what is known about the molecular characteristics of the surface proteins, that is, the red cell receptors and the endothelial cell ligands, involved in sequestration. Recent work from our laboratory on the characterization of the adhesive proteins on the surface of the P falciparum-infected red cell, and the ligands to which they bind on human brain endothelial cells is also discussed. Finally, consideration is given to the multifactor processes involved in sequestration and cerebral malaria, as well as the possible role of ‘anti-adhesion therapy’ in the management of severe malaria.

Publisher Summary This chapter discusses bubonic plague which is a devastating bacterial disease most commonly transmitted by fleas. Fleas are bloodsucking insects, and when a flea bites a plague-infected host, it ingests the rod-shaped bacteria; these multiply in the blood clot in the proventriculus (foregut) of the fl ea. This bacteria-laden clot obstructs the flea's bloodsucking apparatus and, as a consequence, the flea is unable to pump blood into the midgut, where normally it would be digested. The flea becomes hungrier, and in this ravenous state, bites the host repeatedly; with each bite, it regurgitates plague bacteria into the wound. In this way, infection is initiated. Y. pestis can also be pathogenic for the flea, and fleas with their foregut blocked rapidly starve to death. If the mammalian host dies, its body cools down, and fleas respond by moving off the corpse to seek another live warm-blooded host. Although human disease is rare, a feverish patient who has been exposed to rodents or flea bites in plague endemic areas should be considered to be a possible plague victim. A variety of antibiotics including gentamycin, streptomycin, sulfonamides, doxycycline, and ciprofloxacin are effective against bubonic plague. Tetracycline can be used prophylactically, and chloramphenicol is used to treat plague meningitis. No antibiotic resistance has been reported.

Publisher Summary This chapter discusses the use of in vivo and in vitro models in malarial research. Short-term in vitro growth of Plasmodium falciparum and Plasmodium vivax was reported as early as 1912 by Bass and Johns; however, attempts to reproduce this system met with failure. Because of the limitations in the use of in vivo models, attempts were made to carry out studies of EE stages in vitro. In vitro cultures of mammalian malarias initiated from sporozoites were reported as early as 1976. Today, the ability to produce mature and infectious gametocytes of P. falciparum in vitro has allowed for the possibility of producing “large” amounts of sporozoites by membrane feeding to susceptible mosquitoes. Although there are at least 66 different anopheline vector species for P. falciparum, for laboratory studies the most commonly used species are Anopheles stephensi, An. Freeborni, and An. gambiae. A simple in vitro system (for sporogonic stages) could be an indispensable tool in the development of transmission-blocking antibodies as well as antisporozoite vaccines. In vitro development of sporogonic stages has been achieved; however, the system remains far from simple and many of the factors required remain to be identified. It is emphasized that there is still a need to achieve reproducibility and consistency in the in vitro models used.

Publisher Summary This chapter provides an overview of the research conducted on malaria pigment. Hemozoin, the brown–black pigment found within organs, such as the spleen and the liver, as well as in erythrocytes of those infected with malaria, has long been a source of fascination for the students of the disease. Laveran's finding of pigmented bodies in the blood of a soldier suffering with fever that led to his discovery of the malarial parasite is discussed. Brown's findings that intravenous injections of hematin produced a malaria-like paroxysm are described. The role of hemozoin is analyzed and it is suggested that hemozoin (in the form of α- and β-hematin) suppresses erythropoiesis. After endothelial cell ingestion suppresses ICAM-1 and PECAM-1 expression, as well as production of interleukin (IL)-6 and it can lyse red blood cells by incorporation into the membrane. Coban's (2005) work on β-hematin and hemozoin is briefly outlined. Parroche's finding that β-hematin is immunologically inert, whereas natural hemozoin activates the TLR is also discussed.

Publisher Summary This chapter discusses the early years of research and development of malaria parasites in biochemistry. The search for the mode of action of atabrine stimulated the earliest biochemical studies on malaria parasites. The first such study was conducted at the London School of Hygiene and Tropical Medicine, by Christophers and Fulton (1938) using Plasmodium knowlesi, discovered in 1932 in a Malayan kra monkey that had been sent to the Calcutta School of Tropical Medicine via Singapore. In 1898, Sir Rickard Christophers (1873-1978) was appointed to study the relationship of quinine therapy to blackwater fever; his long career in malaria continued with Colonel H. E. Shortt in India (1904-1932). James D. Fulton (1899-1974), trained in chemistry and medicine (1934), worked on antiprotozoan chemotherapy with Warrington Yorke at the Liverpool School of Tropical Medicine. During this same period, work on the biochemistry of malaria was initiated at several universities in the United States including Harvard, Johns Hopkins, and the University of Chicago. Studies in the United States with bird and monkey malarias also used the then current techniques of manometry, photometry supplemented by spectrophotometry.

Publisher Summary This chapter discusses the early history of the research on malarial parasites. Charles Alphonse Laveran, while examining a drop of blood from a feverish artilleryman in 1880, saw several transparent mobile filaments emerging from a clear spherical body. He examined blood samples from 192 malaria patients. In 148 of these, he found the tell-tale crescents. He named the parasite Oscillaria malariae. In 1886, using thin smears of fresh blood, Camillo Golgi discovered that the parasites reproduced asexually by multiple fission. In 1891, Dimitri Romanowsky prepared heat-fixed thin blood films, and used a combination of methylene blue and eosin to stain the nucleus and cytoplasm of the parasite differentially. Ronald Ross, a surgeon–major in the Indian Medical Service, showed how “bad air” could cause malaria. In 1948, Shortt, Garnham, and their colleagues in England inoculated rhesus monkeys with a syringe of sporozoites. This experiment demonstrated that when an infected female anopheline mosquito feeds it injects sporozoites that go first to the liver, where they live and multiply for several weeks, and subsequently they move on to the blood stream, where they reproduce asexually in the red blood cells or they differentiate into male or female gametocytes.

Publisher Summary This chapter analyzes the role of vitamins and antioxidants in malaria infections. Mammalian and avian hosts salvage vitamin B1 (thiamin) from their diet. Plasmodium falciparum is able to synthesize this vitamin, and the cultivation of the parasite in minimal medium is dependent on the provision of 4-amino-5-hydroxymethy-2-methylpyrimidine (HMP) or thiamin but not 5-(2-hydroxyethyl)-4-methylthiazole (THZ) suggesting that HMP, and thiamin are transported into the parasite. The evidence for an active vitamin B6 biosynthetic pathway in P. falciparum is shown by metabolic labeling experiments and a sequence analysis of the parasite genome reveals the presence of three genes: pdx1, pdx2, and pdxK. Pantothenol, a pro-vitamin of pantothenic acid, is found to significantly reduce the parasitemia of mice infected with Plasmodium vinckei and the pantothenate analog CJ-15, 801 inhibit the in vitro growth of P. falciparum. In addition to de novo synthesis of folates, malaria parasites are also able to salvage folate. Both have comparable activity provided the salvage pathway is provided with reduced folate, both of which can be converted to THF. The role of vitamin A, C, D, E, and riboflavin are also analyzed in the chapter. An overview of antioxidant defenses is presented as well in the chapter.

Publisher Summary This chapter discusses how funding from different agencies has helped in advancing malarial research and boosting efforts toward eradication of the disease. Experiences during the Korean War (1950-1953) led the United States Armed Forces Epidemiologic Board (AFEB) to establish a permanent Commission of Parasitic Diseases. Because malaria had exacted a heavy toll on the United States troops during both World Wars as well as the Korean conflict, the Department of Defense, and in particular the Naval Medical Research Institute (NMRI) and the Walter Reed Army Institute of Research (WRAIR) established and maintained active malaria research programs dedicated to protecting the health of the United States military personnel. In 1965, the funding for the WRAIR malaria drug program amounted to $3.3 million, and in 1967, it peaked at $13 million with most funding going into extramural research and drug synthesis. From the mid-1960s onward, the WHO also had a small grants program ($100,000-$150,000 per annum) with the purpose of encouraging research activities in the fields of parasite biology, chemotherapy, and immunology. Prior to the 1990s, the bulk of USAID malaria research funding was devoted to malaria vaccine development. During 2004-2006, USAID contributed more than $6 million to malaria vaccine development annually and in 2006, a total of $10 million was allocated for malaria research.

The Power of Plagues is now available on Wiley.comMembers, use the code ASM20 at check out to receive your 20% discount. How pathogenic microorganisms have shaped human civilization The Power of Plagues presents a rogues' gallery of epidemic-causing microorganisms placed in the context of world history. Author Irwin W. Sherman introduces the microbes that caused these epidemics and the people who sought (and still seek) to understand how diseases and epidemics are managed. What makes this book especially fascinating are the many threads that Sherman weaves together as he explains how plagues past and present have shaped the outcome of wars and altered the course of medicine, religion, education, feudalism, and science. Cholera gave birth to the field of epidemiology. The bubonic plague epidemic that began in 1346 led to the formation of universities in cities far from the major centers of learning (and hot spots of the Black Death) at that time. And the Anopheles mosquito and malaria aided General George Washington during the American Revolution. Sadly, when microbes have inflicted death and suffering, people have sometimes responded by invoking discrimination, scapegoating, and quarantine, often unfairly, against races or classes of people presumed to be the cause of the epidemic. Pathogens are not the only stars of this book. Many scientists and physicians who toiled to understand, treat, and prevent these plagues are also featured. Sherman tells engaging tales of the development of vaccines, anesthesia, antiseptics, and antibiotics. This arsenal has dramatically reduced the suffering and death caused by infectious diseases, but these plague protectors are imperfect, due to their side effects or attenuation and because microbes almost invariably develop resistance to antimicrobial drugs. The Power of Plagues provides a sobering reminder that plagues are not a thing of the past. Along with the persistence of tuberculosis, malaria, river blindness, and AIDS, emerging and remerging epidemics continue to confound global and national public health efforts. West Nile virus, Lyme disease, and Ebola and Zika viruses are just some of the newest rogues to plague humans. The argument that civilization has been shaped to a significant degree by the power of plagues is compelling, and The Power of Plagues makes the case in an engaging and informative way that will be satisfying to scientists and non-scientists alike. Paperback, 494 pages, full-color illustrations.

Table of Contents Introduction 1. The Life of Plasmodium: an Overview, Irwin W. Sherman 2. PlasmoDB: the Plasmodium Genome Resource, Patricia L. Whetzel, Shailesh V. Date, Kobby Essien, Martin J. Fraunholz, Bindu Gajria, Gregory R. Grant, John Iodice, Jessical C. Kissinger, Philip T. Labo, Arthur J. Milgram, Christian J. Stoeckert, Jr., and David Roos 3. Making a Home for Plasmodium Post-Genomics: Ultrastructural Organization of the Blood Stages, Lawrence H. Bannister, Gabriele Margos, and John M. Hopkins 4. Genetic Manipulation of Plasmodium falciparum, Alan F. Cowman and Brendan S. Crabb 5. The Transcriptome of the Malaria Parasite Plasmodium falciparum, Karine Le Roch and Elizabeth Winzeler 6. The Plasmodium Proteome, Jeffrey R. Johnson and John R. Yates III 7. Evolutionary History and Population Genetics of Human Malaria Parasites, Martine Zilversmit and Daniel L. Hartl Invasion and Gamete Formation 8. A Mechanistic Approach to Merozoite Invasion of Red Blood Cells: Merozoite Biogenesis, Rupture, and Invasion of Erythrocytes, Mary R. Galinski, Anton R. Dluzewski, and John W. Barnwell 9. The Sporozoite, R. E. Sinden and K. Matuschewski 10. Gametocytes and Gametes, Pietro Alano and Oliver Billker Growth and Metabolism 11. Molecular Approaches to Malaria: Glycolysis in Asexual-Stage Parasites, Charles J. Woodrow and Sanjeev Krishna 12. The Mitochondrion, Akhil B. Vaidya 13. Trafficking and the Tubulovesicular Membrane Network, Kasturi Haldar, Narla Mohandas, Souvik Bhattacharjee, Travis Harrison, N. Luisa Hiller, Konstantinos Liolios, Sean Murphy, Pamela Tamez, and Christiaan van Ooij 14. The Apicoplast, Stuart A. Ralph 15. Protein Kinases Regulating Plasmodium Proliferation and Development, Christian Doerig 16. Proteases and Hemoglobin Degradation, Philip J. Rosenthal 17. Plasmodium Lipids: Metabolism and Function, Henri J. Vial and Choukri Ben Mamoun 18. Plasmodium Ribosomes and Opportunities for Drug Intervention, Indu Sharma and Thomas F.. McCutchan 19. Oxidative Stress and Antioxidant Defense in Malarial Parasites, Katja Becker, Sasa Koncarevic, and Nicolas H. Hunt 20. New Permeation Pathways, Serge L. Thomas and Stephanie Egee Immune Evasion 21. Molecular Aspects of Antigenic Variation in Plasmodium falciparum, Paul Horrocks, Susan A. Kyes, Peter C. Bull, and Kirk W. Deitsch 22. Rosetting, J. Alexandra Rowe Protection 23. Mechanisms of Antimalarial Drug Action and Resistance, Anne-Catrin Uhlemann, Yongyuth Ythavong, and David A. Fidock 24. Host Genetic Factors in Resistance and Susceptibility to Malaria, Dominic P. Kwiatkowski and Gaia Luoni 25. Progress in Development of a Vaccine To Aid Malaria Control, Vasee S. Moorthy and Filip Dubovsky Vector 26. The Anopheles gambiae Genome, Frank H. Collins and Catherine A. Hill 27. The Transcriptome of Human Malaria Vectors, Osvaldo Marinotti and Anthony A. James

Sequestration in the microvessels of the deep tissues is a signal characteristic of the human malaria Plasmodium falciparum. The adhesion of P. falciparum-infected cells to the post-capillary endothelial cells in various tissues contributes to both the pathology of the disease (i.e. organ infarcts and coma) and parasite survival (i.e. the microaerophilic environment favors plasmodial growth while avoiding passage through and destruction in the spleen). This report identifies a conformational change in a region of band 3 protein involved in the enhanced adhesiveness of P. falciparum-infected erythrocytes.

A knobless (K-) line of the FCR-3 isolate of Plasmodium falciparum was obtained by gelatin flotation. Immunofluorescent staining and immunoblots indicated that both the K- line and the K+ (knobby) line from which it was derived contained similar forms of potentially adhesive modified band 3 protein. When the K+ and K- lines were assayed for their cytoadherent and rosetting abilities the K+ line showed a high level of CD36 dependent cytoadherence, whereas the K- line demonstrated a marked pH dependent increase in rosetting. Rosetting was inhibited by the addition of peptides based on band 3 motifs, suggesting that cytoadherence and rosetting involve the same adhesin but that the presence of knobs affects whether the adherent preference of the infected erythrocyte is uninfected red cells or endothelial/C32 amelanotic melanoma cells.

Cytoadherence of Plasmodium falciparum-infected erythrocytes to amelanotic melanoma cells was pH dependent; increased adherence was observed in the pH range of 6.1 to 6.8 and was greatest between pH 6.6 and 6.8. Ca2+ promoted Cytoadherence, but at higher concentrations (40–50 mM) than is usually the case for cell-cell adhesion. The effects of pH and Ca2+ were interdependent—the pH optimum of Cytoadherence was altered by the Ca2+ concentration in the medium. The adherent properties of several P. falciparum lines (including a knobless cytoadherent line) under varying pH and Ca2+ concentrations were similar.

SUMMARYA reproducible and standardized assay for measuring the cytoadherence of knobbyPlasmodium falciparum-infected red cells to amelanotic melanoma cells was developed. Adhesion was dependent on temperature, haematocrit, and parasitaemia. Addition of EDTA to the binding medium reduced adhesion. Removal of protease-sensitive molecules on the surface of the infected cell abolished cytoadherence, whereas removal of carbohydrate residues by treatment of cells with neuraminidase or galactosidase promoted adhesion. Calcium, magnesium, fibrinogen or fibronectin in the medium had no effect on adhesion nor was there any enhancement of adhesion by pre-loading infected cells with calcium. Serum was essential for good adhesion. Adhesion was species specific for target cells; human endothelial or amelanotic melanoma cells were suitable target cells whereas bovine cells were not. The amelanotic melanoma cell could be formalin-fixed and still retain its adhesion properties. The binding properties of formalin-fixed amelanotic melanoma cells were not identical to those of endothelial or unfixed target cells.

SUMMARYAccording to the World Health Organization the global estimate of malaria is over 200 million infections, the majority of which are caused by the most life-threatening species,Plasmodium falciparum(Report of the Steering Committees of the Scientific Working Groups on Malaria, World Health Organization, June 1983). The causative agent of the disease, the malarial parasite, requires two hosts: a blood-sucking mosquito and a blood-containing vertebrate. Commonly, infection of the vertebrate begins when an infected mosquito bites a suitable vertebrate and injects minute sporozoites into the bloodstream. Within 30 mm the introduced sporozoites leave the bloodstream and enter parenchymal cells of the liver (mammals) or endothelial cells (birds). In these sites the parasite undergoes asexual multiplication (= exo-erythrocytic schizogony) producing daughter progeny called merozoites. The exo-erythrocytic merozoites are released from the tissues into the circulation where they invade red blood cells. Within an erythrocyte the merozoite undergoes asexual multiplication (= erythrocytic schizogony) producing a substantial number of merozoites. The erythrocyte lyses, merozoites are released, and invasion of another erythrocyte may then take place. The synchronous rupture of the red cell and merozoite release is marked by the periodic fever–chill cycles so characteristic of the malarial infection. Some merozoites continue to reinvade other erythrocytes and multiply by asexual means, whereas others enter erythrocytes and differentiate into sexual stages, male or female gametocytes. When a suitable mosquito feeds on an infected vertebrate gametocytes are ingested and the sexual cycle of development is initiated. In the mosquito stomach the gametocytes transform into gametes, fertilization takes place, the resultant worm-like zygote penetrates the cells of the mosquito gut and comes to lie on the outer surface of the stomach. Here each zygote forms a cyst-like body, the oocyst, within which thousands of sporozoites are produced by asexual multiplication. When the swollen oocysts burst, sporozoites are freed and these make their way to the salivary gland. At the next blood feeding the mosquito injects the infective sporozoites and the life-cycle is completed.

1. 1. The avian malaria. Plasmodium lophurae, malaria-infected erythrocytes, and normal duck erythrocytes suspended in a protein-free medium resembling the in vivo environmental milieu showed 4 patterns of accumulation of radioactive amino-acids. 2. 2. In vitro, malaria parasites were capable of utilizing exogenously supplied amino-acids for the synthesis of parasite proteins. The protein synthetic activity found for the malariainfected cell could, in general, be represented as the sum of the activities of the uninfected cell and that of the free parasite. 3. 3. A hypothesis is presented which proposes that the rate of amino-acid incorporation by the parasite depends on three factors: (a) the free amino-acid levels, (e) the rate of amino-acid entry, and (c) the abundance of the amino-acid in the protein being synthesized.

SYNOPSIS. The use of saponin hemolysis, buffer washings and deoxyribonuclease yields quantities of erythrocyte-free plasmodia sufficiently pure for physico-chemical studies. The pigment produced by Plasmodium lophurae, unlike the pigments of the simian and human malarias, is of such low solubility in buffer solutions that urea is necessary as an additive to the buffer for adequate solubilization. On the basis of spectral and electrophoretic qualities, the pigment is a protein-porphyrin complex closely resembling methemoglobin but clearly distinct from hematin. Extraction of the pigment in solvents which degrade hemoglobin, e.g. phenol, 0.1 N NaOH, cannot be used to ascertain the properties of hemozoin, for the pigment in such solvents shows a spectrum identical to hemoglobin. The soluble parasite proteins which constitute approximately 55% of the totaI volume of the parasite as revealed by electrophoretic and ultracentrifugal analysis appear to be homogeneous. They show a marked similarity to the host hemoglobin, but differ sufficiently to verify their integrity and individuality.

SYNOPSIS. Plasmodium lophurae hemozoin (malaria pigment) is a heme-containing protein which is distinctly different from hemoglobin and hematin by immunologic, spectrophotometric, fingerprint, heme-iron, gel filtration, and starch gel electrophoretic analyses. The calculated average molecular weight of P. lophurae hemozoin is ca. 40,000. Hemozoin contains at least 3 antigenic components and shows some indication of cross-reaction with hemoglobin.

1. 1. During the course of infection of Plasmodium lophurae (avian malaria) in white Pekin ducklings the red blood cell sodium concentration was significantly elevated in parasitized animals (14·0±1·32 mM; mean ± S.E.M.) as compared to normal animals (8·8 ± 0·72 mM); the plasma potassium level was also significantly increased in malarious ducklings (5·4 ± 0·29 mM) when compared to normal ducklings (2·9 ± 0·18 mM). 2. 2. Cation concentrations of P. lophurae more closely resembled those of the duck erythrocyte than of duck plasma.

Lactic dehydrogenase activity increased in direct proportion to the degree of parasitization in synchronous infections of duck erythrocytes. Deviations from this linearity could be accounted for on the basis of the developmental stage of the parasite. Erythrocyte-free P. lophurae showed activities which averaged 3 times that of uninfected erythrocytes, whereas infected erythrocytes had intermediate values. In addition, a patent infection was generally reflected by an increase in the lactic dehydrogenase activity in the plasma, but no direct correlation with parasitemia was established. Molecular heterogeneity of the enzyme was determined on the basis of kinetic data and electrophoretic isolation on a starch block. The uninfected red blood cell showed a major anodal and a minor cathodal peak of lactic dehydrogenase activity, and was further characterized by a kinetic constant representing a high pH optimum with low concentrations of substrate. Isolated P. lophurae had a single, cathodal peak of activity dissimilar from that of the uninfected erythrocyte, and a kinetic constant describing a low pH optimum with a high concentration of substrate. Infected erythrocytes showed a combination of these electrophoretic entities and an intermediate range of kinetic constants. The data indicate that the avian malaria parasite P. lophurae contains a lactic dehydrogenase qualitatively dissimilar from that of its host cell, and the increased enzymatic activity of infected erythrocytes is a result of the enzyme content of the growing parasite added to that of the red blood cell. It is suggested that the LDH of the parasite has a physiological advantage under those conditions which prevail inside the red blood cell.

SYNOPSIS. A study by means of paper electrophoresis of the scrum.proteins and lipoproteins during the course of infection of chicks with Plasmodium lophurae, reveals a qualitative change in the gamma-globulin and demonstrates: a significant crisis period depression of the albumin; no alteration of the alpha-globulin or alpha-lipoprotein; a significant crisis period rise in the beta- and gamma-g'obuiins with the former persisting in higher amounts well after the crisis of the infection. The significance of such changes with reference to previous work and the induced pathology is discussed.

1. 1. The avian malarjal parasite. Plasmodium lophurae , was grown in vivo through one asexual cycle m duck erythrocytes containing radioactive haemoglobin. 2. 2. Radioactivity was recovered in the parasite proteins (uncontaminated by host cell haemoglobin or malaria pigment), thus demonstrating the in vivo utilization of host cell haemoglobin by the malaria parasite for synthesis of plasmodial proteins.