Glossary

actin

a protein that is a major constituent of cell microfilaments.

adjuvant

a compound, injected as a mixture with an antigen, that serves to intensify the immune response.

AIDS

acquired immunodeficiency syndrome.

allele

one of two or more alternative forms taken by a gene that occupies corresponding sites on structurally similar (homologous) chromosomes. The allelic forms differ in DNA sequence.

allotypes

antigenic markers on immunoglobulin chains or other serum proteins that are not common to normal members of a species; the markers are controlled by allelic genes.

amino acid

protein subunits; there are 20 found universally in proteins.

anopheline

used when referring to Anopheles mosquitoes.

anthropophilic

attracted to humans as a source of food.

antibody

a protein produced by the immune system in response to the introduction into the body of a substance (an antigen) recognized as foreign by the body's immune system. The purpose of the antibody is to interact with other components of the immune system and render the antigen harmless, although for various reasons this may not always occur.

antigen

a molecule capable of eliciting an immune response.

antigenic diversity

the ability of an organism to change its antigenic makeup in response to environmental factors.



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MALARIA: Obstacles and Opportunities Glossary actin a protein that is a major constituent of cell microfilaments. adjuvant a compound, injected as a mixture with an antigen, that serves to intensify the immune response. AIDS acquired immunodeficiency syndrome. allele one of two or more alternative forms taken by a gene that occupies corresponding sites on structurally similar (homologous) chromosomes. The allelic forms differ in DNA sequence. allotypes antigenic markers on immunoglobulin chains or other serum proteins that are not common to normal members of a species; the markers are controlled by allelic genes. amino acid protein subunits; there are 20 found universally in proteins. anopheline used when referring to Anopheles mosquitoes. anthropophilic attracted to humans as a source of food. antibody a protein produced by the immune system in response to the introduction into the body of a substance (an antigen) recognized as foreign by the body's immune system. The purpose of the antibody is to interact with other components of the immune system and render the antigen harmless, although for various reasons this may not always occur. antigen a molecule capable of eliciting an immune response. antigenic diversity the ability of an organism to change its antigenic makeup in response to environmental factors.

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MALARIA: Obstacles and Opportunities antigenic variation see antigenic diversity. apical complex a group of organelles, thought to be involved in the red blood cell invasion process, at the apical (tip) end of the malaria parasite. asexual reproduction a stage in the life cycle of the malaria parasite in humans. biotinylated a process in which DNA probes are labeled with biotin. B lymphocyte same as B cell. One of two types of lymphocytes (white blood cells) involved in the humoral immune response in humans. When instructed to do so by T lymphocytes, B lymphocytes produce antibodies against specific antigens. buffy coat a layer, composed of white blood cells, that occurs upon centrifugation of whole blood under specific conditions. carrier protein an immunogenic molecule to which an incomplete antigen (one that cannot induce an immune response by itself) is attached, rendering the antigen capable of inducing an immune response. cDNA complementary or copy DNA, produced from an RNA template transcribed from the DNA that is being copied. cell-mediated immunity a type of immune response in which subpopulations of T cells (helper T cells and killer T cells) cooperate to destroy cells in the body that bear foreign antigens, such as parasite-infected red blood cells. chemoprophylaxis the use of drugs to prevent infection or progression of infection to illness. chromosome DNA-containing genetic material in the nucleus of a cell. Each organism has a specific number of chromosomes, each responsible for transmitting distinctive characteristics to the organism's progeny. circumsporozoite protein a protein located on the surface of the sporozoite that is thought to be important in host cell recognition and invasion. clone genetically engineered replicas of DNA sequences. congenic a situation in which two members of the same genus have an identical genetic makeup. conserved sequence an amino acid or nucleotide sequence that has not changed (or has changed only slightly) over a period of time. cytoadherence the ability of red blood cells, infected with Plasmodium falciparum, to adhere to the endothelial cell lining of brain capillaries. cytokine specific compounds that, when present, induce the proliferation of immune cells. cytotoxic T lymphocyte same as cytotoxic T cell. A lymphocyte that binds and kills foreign cells.

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MALARIA: Obstacles and Opportunities DDT 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane or chlorophenothane, a pesticide. DNA deoxyribonucleic acid, a carrier of genetic information (i.e., hereditary characteristics) found chiefly in the nucleus of cells. Duffy antigen blood group antigens on the surface of erythrocytes that serve as receptors for Plasmodium vivax, rendering individuals who are Duffy negative refractory to vivax malaria. Most peoples of African descent are Duffy negative. efflux the process in which an antimalarial drug is transported out of the parasite. EIR see entomological inoculation rate. electrophoresis the process by which substances, such as serum, are separated into their components by the application of an electrical field to a suspension containing the substance. An example is gel electrophoresis, in which the substance is suspended in a gel. ELISA enzyme-linked immunosorbent assay. An immunological technique used for the quantitation of antigen or antibody. In the assay, enzyme-labeled antigen or antibody is bound to a solid surface (such as beads, tubes, or microplate wells). After addition of the patient specimen and substrate, the presence of the desired antigen, antibody, or antigen-antibody complex is indicated by a color change based on an enzyme-substrate reaction. endemic the condition in which a disease is present in a community at all times. There are four subcategories of endemicity: holo-, hyper-, meso- and hypoendemic. endophilic associated with humans and their domestic environment. entomological inoculation rate (EIR) a measure of the number of infective bites each person receives per night. A direct measure of the risk of human exposure to the bites of infective mosquitoes. epidemic the condition in which a disease spreads rapidly through a community in which the disease is normally not present or is present at a low level. epidemiology study of the distribution and determinants of a disease within a given population. epitope a small segment (structural component) of an antigen responsible for specific interaction with antibody molecules elicited by the same or a related antigen. erythrocyte red blood cell; oxygen-carrying cell. Invaded by malaria merozoites during malaria infection. exchange transfusion the process by which the blood of a person is replaced with blood taken from others; used in cases of severe malaria where the parasite has caused such damage to the red blood cells that they are unable to carry sufficient oxygen to the individual's cells.

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MALARIA: Obstacles and Opportunities exflagellation the formation of microgametes by extrusion of nuclear material into peripheral processes of gametocyte cytoplasm. These processes resemble flagella. exoerythrocytic applies to stages of development of the malaria parasite that occur in cells other than red blood cells. Fab fragment either of two segments of an antibody molecule (IgG). Each Fab fragment remains capable of combining with the antigen that elicited its production. falciparum malaria malaria caused by the parasite Plasmodium falciparum. gamete mature germ cell. In malaria, there are two types, micro- and macrogametes. These develop from male and female gametocytes and fuse within the mosquito midgut to form a zygote. gametocyte the sexual-stage precursors of the malaria parasite. The micro- and macrogametocytes (male and female) develop within the human host and are picked up by the mosquito while in the act of biting. In the mosquito, the gametocytes develop further into micro- and macrogametes. gene the biological unit of heredity, located on chromosomes. gene-cloned vaccine see recombinant vaccine. genetic diversity differences in genetic makeup within a species. genomic library a random collection of fragments of the DNA of a given species inserted into a corresponding collection of vectors and cloned in a suitable host. Such a collection includes all the unique nucleotide sequences of the genome. genotype the genetic makeup of an organism, as distinguished from its physical appearance or phenotype. hepatocyte a liver cell invaded by the malaria sporozoite. heterologous a disparity in antigenic makeup between two or more antigens. HIV human immunodeficiency virus, the agent that causes AIDS. holoendemic the condition in which malaria is present in a community at all times and with a very high transmission rate, resulting in a population (particularly adults) that has considerable immunity to the disease. homologous corresponding in structure, such as homologous antigens. humoral immunity immunity based on the interaction of antibody with antigen. Involves both T and B cells and may be present in the company of cell-mediated immunity. hyperendemic the condition in which malaria is present in a community at all times and with a high incidence. hypnozoite latent sporozoite that undergoes a period of dormancy in the host 's liver, eventually giving rise to a relapse of the disease. hypoendemic the condition in which malaria is present in a community at

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MALARIA: Obstacles and Opportunities low levels, resulting in a population that generally has little or no immunity. hypoglycemia an abnormally low level of sugar in the blood, which may result in shaking, cold sweats, hypothermia, headache, and potentially convulsions and coma. IgA immunoglobulin A; a class of immunoglobulin found in external body secretions such as saliva, tears, and sweat, and on the surface of cell membranes. IgG immunoglobulin G; the predominant immunoglobulin involved in the secondary immune response. IgM immunoglobulin M; the predominant immunoglobulin found in the primary immune response. immune system a natural defense mechanism of the body, in which specialized cells and proteins in the blood and other body fluids interact to eliminate or neutralize infectious microorganisms and other foreign substances. immunodominant the central or dominant epitope on an antigen. immunogen a substance, or antigen, capable of eliciting an immune response. immunoglobulin antibody secreted by plasma cells (mature lymphoid cells). There are five classes of immunoglobulin: IgG, IgM, IgA, IgE, and IgD. incidence as used in epidemiology, the number of new cases of a disease that occur within a specified time period. in vitro biological processes that occur in isolation from the whole organism, such as in a test tube or in cell culture; in the laboratory. in vivo biological processes that occur within in the body of a living organism. kilodalton a unit of mass equal to one thousand daltons or approximately 1.65 × 10−21 grams. ligand a molecule (such as oxygen) that binds to a complementary site on a given structure (such as hemoglobin). loading dose the dose used at the initiation of therapy to rapidly establish the desired blood and tissue levels of the drug; also known as a priming dose. macrogametocyte see gametocyte. macrophage a large, phagocytic, mononuclear lymphocyte found in tissues but derived from blood monocytes. Depending on the tissue they are locating in, macrophages are called histiocytes (connective tissue macrophages), Kupffer's cells (liver macrophages), or alveolar macrophages (lungs). Involved in the immune response to antigens, the macrophages process antigens and present them to the lymphocytes. marginal benefit the extra benefit attributed to an extra unit of output.

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MALARIA: Obstacles and Opportunities marginal cost the extra cost incurred for an extra unit of output. merozoite the stage of the parasite, in the human host, that infects the red blood cells. mesoendemic the condition in which malaria is present in a community at low levels, with occasional epidemics resulting from the generally low level of immunity in the population. microgametocyte see gametocyte. monoclonal derived from a single clone of cells. monoclonal antibody immunoglobulins derived from a single clone of plasma cells. Monoclonal antibodies constitute a pure population, as they are produced by a single clone in vitro and are chemically and structurally identical. monocyte the largest lymphocyte found in the blood; they are phagocytic. nucleotide one of the compounds into which a nucleic acid is split by the action of a nuclease; nucleotides are composed of a base, a sugar, and a phosphate group. oligonucleotide a polymer composed of more than three nucleotides. oocyst the encysted or encapsulated ookinete in the wall of an infected mosquito's stomach. ookinete the fertilized form of the malaria parasite in the mosquito's body. parasitemia the level of parasites in the blood. parenteral a method in which a drug or vaccine is introduced into the body, other than by oral ingestion. passive protection disease-specific immunity produced by the injection of antibody-containing serum from a donor with active immunity to the disease. PCR polymerase chain reaction. A method of amplifying low levels of specific DNA sequences in a sample, thus allowing one to detect very low levels of antigen or antibody in the sample. phenotype the entire physical, biochemical, and physiological makeup of an organism as determined by both genetics and the environment. point mutation a mutation caused by the substitution of one nucleotide for another. polyclonal antibodies generated by more than one clone of B lymphocytes in response to an antigen; i.e., arising from more than one clone. prevalence as used in epidemiology, the total number of cases of a disease in existence at a specific time and within a well-defined area. reading frame alteration a change in a nucleotide sequence that results in the insertion or deletion of a nucleotide in newly formed DNA strands during replication. receptor a specific chemical grouping, on the surface of an immunologi-

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MALARIA: Obstacles and Opportunities cally competent cell, with the capability of combining with a specific antigen. Also may refer to a receptor for antibodies. recombinant vaccine a vaccine prepared by recombinant DNA technology in which a a host organism (expression vector) is directed to synthesize specific molecules as the result of insertion of DNA segments from another organism (such as the malaria parasite). In this manner, vaccines that are directed against specific antigens within the parasites can be made. recombination the formation of new combinations of genes as a result of crossing over (sharing of genes) between structurally similar chromosomes, resulting in progeny with different gene combinations than in the parents. recrudescence recurrence of a disease after a brief intermission. relapse recurrence of disease symptoms after a period of improvement. returns to scale the proportionate increase in output resulting from proportionate increases in all inputs. RIA radioimmunoassay. A highly sensitive assay for antigen in which the concentration of an unknown, unlabeled antigen is determined by comparing its inhibitory effect on the binding of radioactively labeled antigen to specific antibody with the inhibitory effect of known standards. schizogony the process in which sporozoites develop into merozoites within the liver hepatocytes. schizont a multinucleate parasite that reproduces by schizogony. sensitivity the ability of a test to detect small differences in the level of antigen or antibody in a sample. sequestration the situation in which the malaria parasite resides in and obstructs the capillaries of the brain, apparently causing cerebral malaria. seronegative negative result in a serological test; i.e., the inability to detect the antibodies being tested for. seropositive positive result in a serological test. serum the clear liquid remaining after blood has clotted. sexual reproduction refers to the stage of the parasite's life cycle that begins in the vertebrate host and is completed in the mosquito. specificity refers to the relative ability to differentiate among different organisms or strains of an organism. sporogony that portion of the sexual reproduction of the parasite that takes place in the mosquito. sporozoite a stage of the malaria parasite that is transmitted to humans by the mosquito. Sporozoites are released from oocysts on the mosquito 's stomach, travel to the salivary glands, and are transmitted when the mosquito bites. subunit vaccine a vaccine prepared from parts of a whole organism. The

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MALARIA: Obstacles and Opportunities concept is to use those portions of the organism that are immunogenic, leaving out those that produce pathologic manifestations. synthetic vaccine a vaccine manufactured by biochemical means, to simulate the immunogenic portions of the organism against which the vaccine is being prepared. tandem repeats duplications of tandem combinations. T lymphocyte same as T cell. An immunologically competent white blood cell that direct the production of antibody by B lymphocytes; are responsible for cell-mediated immunity and immunological memory. trophozoite the stage, between the ring stage and the schizont, that occurs in the red blood cell. tubulin a principal protein component of microtubules (which play key roles in cell division and morphogenesis). Alpha- and beta-tubulins have been described. vector the mosquito that transmits the malaria parasite from one host to another. vector competence refers to the relative ability of a vector (relative to another vector) to transmit a specific infective agent from one host to another, implying that a competent vector is one that takes in sufficient numbers of an agent to ensure infection, supports the development or multiplication of the agent, and is able to deliver a large enough inoculum to an appropriate site in a new host to ensure infection. vivax malaria malaria caused by the malaria parasite Plasmodium vivax. zoophilic prefer to feed on animals. zygote an organism produced by the union of two gametes.