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The occurrence of four parasitic species of zoonotic potential, Entamoeba coli , Entamoeba histolytica / dispar , Trichuris sp. and hookworm was investigated in the toque macaque, grey langur and the purple-faced langur at 32 sites across Sri Lanka. The study was carried out during the rainy season months of February - March in both 2007 and in 2009 and in December of 2010. 93 faecal samples were collected from 49 monkey troops at representative locations in altitudinal /climatic zones across the country where toque macaques (58 samples), grey langurs (21 samples) and purple-faced langurs (14 samples) naturally occur. Overall, the most common parasitic species found in all three primates were Trichuris sp. (28 %) and E. coli (25 %). Notably, hookworms were present in 23 % of the grey langur samples and 33 % of the toque macaque samples but absent in the purple-faced langur samples collected. Statistically significant variability in the prevalence levels across altitudinal/climatic zones was noted for toque macaques. Overall, group prevalence values in toque macaques decreased with increasing altitude; the highest values were found in the intermediate to arid lowland zones, and were lowest in the upland wet zone. Only Trichuris sp. and hookworm were found (13 %, 7 %, respectively) in the highland/ wet zone. Molecular analysis will be necessary to genetically type the parasite species before drawing firm conclusions about the status of zoonotic transmission between humans and non-human primates in the country. However this study highlights the need to systematically survey the human parasite population in areas where primates are commonly found to harbour these parasite species. J.Natn.Sci.Foundation Sri Lanka 2013 41 (4):319-326 DOI: http://dx.doi.org/10.4038/jnsfsr.v41i4.6246

BACKGROUND:Antigenic variation by malaria parasites was first described in Plasmodium knowlesi, which infects humans and macaque monkeys, and subsequently in P. falciparum, the most virulent human parasite. The schizont-infected cell agglutination (SICA) variant proteins encoded by the SICAvar multigene family in P. knowlesi, and Erythrocyte Membrane Protein-1 (EMP-1) antigens encoded by the var multigene family in P. falciparum, are expressed at the surface of infected erythrocytes, are associated with virulence, and serve as determinants of naturally acquired immunity. A parental P. knowlesi clone, Pk1(A+), and a related progeny clone, Pk1(B+)1+, derived by an in vivo induced variant antigen switch, were defined by the expression of distinct SICA variant protein doublets of 210/190 and 205/200 kDa, respectively. Passage of SICA[+] infected erythrocytes through splenectomized rhesus monkeys results in the SICA[-] phenotype, defined by the lack of surface expression and agglutination with variant specific antisera. PRINCIPAL FINDINGS:We have investigated SICAvar RNA and protein expression in Pk1(A+), Pk1(B+)1+, and SICA[-] parasites. The Pk1(A+) and Pk1(B+)1+ parasites express different distinct SICAvar transcript and protein repertoires. By comparison, SICA[-] parasites are characterized by a vast reduction in SICAvar RNA expression, the lack of full-length SICAvar transcript signals on northern blots, and correspondingly, the absence of any SICA protein detected by mass spectrometry. SIGNIFICANCE:SICA protein expression may be under transcriptional as well as post-transcriptional control, and we show for the first time that the spleen, an organ central to blood-stage immunity in malaria, exerts an influence on these processes. Furthermore, proteomics has enabled the first in-depth characterization of SICA[+] protein phenotypes and we show that the in vivo switch from Pk1(A+) to Pk1(B+)1+ parasites resulted in a complete change in SICA profiles. These results emphasize the importance of studying antigenic variation in the context of the host environment.

Paramyosin, a 97 kDa myofibrillar protein, is a candidate vaccine antigen for prevention of infection with the human parasite Schistosoma mansoni. To determine if paramyosin would also induce protection against Schistosoma japonicum, paramyosin was biochemically purified from S. japonicum adult worms. SDS-PAGE demonstrated a single protein with a molecular weight of 97 kDa. In four separate experiments, vaccination of mice with S. japonicum paramyosin without adjuvant induced significant resistance (62%-86%, P < 0.001) against cercarial challenge as compared to controls. These data suggest that S. japonicum paramyosin may represent a candidate vaccine for immunization against schistosomiasis japonica.

We have analyzed the conserved regions of the gene coding for the circumsporozoite protein (CSP) in 12 species of Plasmodium, the malaria parasite. The closest evolutionary relative of P. falciparum, the agent of malignant human malaria, is P. reichenowi, a chimpanzee parasite. This is consistent with the hypothesis that P. falciparum is an ancient human parasite, associated with humans since the divergence of the hominids from their closest hominoid relatives. Three other human Plasmodium species are each genetically indistinguishable from species parasitic to nonhuman primates; that is, for the DNA sequences included in our analysis, the differences between species are not greater than the differences between strains of the human species. The human P. malariae is indistinguishable from P. brasilianum, and P. vivax is indistinguishable from P. simium; P. brasilianum and P. simium are parasitic to New World monkeys. The human P. vivax-like is indistinguishable from P. simiovale, a parasite of Old World macaques. We conjecture that P. malariae, P. vivax, and P. vivax-like are evolutionarily recent human parasites, the first two at least acquired only within the last several thousand years, and perhaps within the last few hundred years, after the expansion of human populations in South America following the European colonizations. We estimate the rate of evolution of the conserved regions of the CSP gene as 2.46 x 10(-9) per site per year. The divergence between the P. falciparum and P. reichenowi lineages is accordingly dated 8.9 Myr ago. The divergence between the three lineages leading to the human parasites is very ancient, about 100 Myr old between P. malariae and P. vivax (and P. vivax-like) and about 165 Myr old between P. falciparum and the other two.

The anaerobic protist Giardia intestinalis, the most common protozoan intestinal parasite worldwide, infects the fairly oxygenated human small intestine, where it has to cope with O2 and NO stress. Based on genomic studies, although lacking common antioxidant enzymes (like superoxide dismutase and catalase), Giardia is the only pathogenic protist as yet identified encoding a flavohemoglobin (flavoHb) and among the very few eukaryotes encoding a superoxide reductase (SOR) and a flavodiiron protein (FDP). While the FDP was suggested to be involved in O2 detoxification, we found that the recombinant Giardia flavoHb aerobically metabolizes NO with high efficacy (Vmax = 116 ± 10 s−1 at 1 μM NO, K M, O 2 = 22 ± 7 μ M , T = 37 °C). The parasitic cells express this microbial globin at low levels and, accordingly, metabolize NO with low efficacy. In response to nitrosative stress, however, flavoHb expression is enhanced and the parasite thereby becomes able to aerobically metabolize NO efficiently. In collaboration with M. Teixeira and L.M. Saraiva (New University of Lisbon, Portugal) and D.E. Cabelli (Brookhaven National Laboratory, New York, USA), more recently the recombinant Giardia SOR was also purified and characterized. The protein, immunodetected in Giardia cells, shows negligible superoxide dismutase activity, but in the reduced state is highly reactive with superoxide anion, as shown by pulse radiolysis and stopped-flow spectrophotometry. It is suggested that flavoHb and SOR in vivo contribute to protect Giardia from nitrosative stress, thus promoting parasite pathogenicity.

Malaria is a devastating global disease with several hundred million clinical cases and just under 1 million deaths each year (http://www.who.int/topics/malaria/). It is caused by protozoan parasites of the genus Plasmodium, which have a complex life cycle in a vertebrate host and a mosquito vector. Malaria parasites are haploid throughout most of this life cycle, replicating by asexual multiplication twice in a mammalian host: in liver hepatocytes (pre-erythrocytic schizogony) and within red blood cells (blood stage schizogony), and once in the mosquito (sporogony). The essential sexual stage occurs at the transmission from vertebrate to insect. Some asexual blood stage parasites develop into either male or female gametocytes (the precursor sex cells) and following ingestion in a mosquito blood meal differentiate further into gametes in the lumen of the mosquito's gut, where fertilization takes place. The core processes of gametocytogenesis, gamete activation, exflagellation, fertilization, and zygote formation are conserved across the species from the human parasite Plasmodium falciparum to the rodent parasite Plasmodium berghei, which is an attractive laboratory model, in part because of its ease of genetic manipulation and the shorter time for the maturation and differentiation of the sexual stages. Here, we focus largely on recent functional studies using reverse genetics that have uncovered many aspects of the parasite's sexual development.

Maintenance of adult male worms of the bovine filarial parasite Onchocerca gibsoni in vitro , in the presence of radioactive precursors, resulted in the time-dependent excretion-secretion of radiolabelled parasite macromolecules (ES). Molecules labelled with amino acids ([ 35 S] methionine, pH] leucine) covered a wide range of molecular weights, whereas labelling with [ 3 H] glucosamine produced predominantly molecules of high molecular weight. Many of the products were recognized by antibodies in two serum pools from humans infected with Onchocerca volvulus . O. gibsoni ES may therefore provide a substitute source of material for studies on the ES of the less readily available human parasite.

Malaria caused by several species of Plasmodium is major parasitic disease of humans, causing 1-3 million deaths worldwide annually. The widespread resistance of the human parasite to current drug therapies is of major concern making the identification of new drug targets urgent. While the parasite grows and multiplies inside the host erythrocyte it degrades the host cell hemoglobin and utilizes the released amino acids to synthesize its own proteins. The P. falciparum malarial M1 alanyl-aminopeptidase (PfA-M1) is an enzyme involved in the terminal stages of hemoglobin digestion and the generation of an amino acid pool within the parasite. The enzyme has been validated as a potential drug target since inhibitors of the enzyme block parasite growth in vitro and in vivo. In order to gain further understanding of this enzyme, molecular dynamics simulations using data from a recent crystal structure of PfA-M1 were performed. The results elucidate the pentahedral coordination of the catalytic Zn in these metallo-proteases and provide new insights into the roles of this cation and important active site residues in ligand binding and in the hydrolysis of the peptide bond. Based on the data, we propose a two-step catalytic mechanism, in which the conformation of the active site is altered between the Michaelis complex and the transition state. In addition, the simulations identify global changes in the protein in which conformational transitions in the catalytic domain are transmitted at the opening of the N-terminal 8 Å-long channel and at the opening of the 30 Å-long C-terminal internal chamber that facilitates entry of peptides to the active site and exit of released amino acids. The possible implications of these global changes with regard to enzyme function are discussed. © 2011 Jones et al.

Protozoa in the phylum Apicomplexa are a large group of obligate intracellular parasites. Toxoplasma gondii and other apicomplexan parasites, such as Plasmodium falciparum, cause diseases by reiterating their lytic cycle, comprising host cell invasion, parasite replication, and parasite egress. The successful completion of the lytic cycle requires that the parasite senses changes in its environment and switches between the non-motile (for intracellular replication) and motile (for invasion and egress) states appropriately. Although the signaling pathway that regulates the motile state switch is critical to the pathogenesis of the diseases caused by these parasites, it is not well understood. Here we report a previously unknown mechanism of regulating the motility activation in Toxoplasma, mediated by a protein lysine methyltransferase, AKMT (for Apical complex lysine (K) methyltransferase). AKMT depletion greatly inhibits activation of motility, compromises parasite invasion and egress, and thus severely impairs the lytic cycle. Interestingly, AKMT redistributes from the apical complex to the parasite body rapidly in the presence of egress-stimulating signals that increase [Ca2+] in the parasite cytoplasm, suggesting that AKMT regulation of parasite motility might be accomplished by the precise temporal control of its localization in response to environmental changes., Author Summary Toxoplasma gondii is one of the most successful human parasites, infecting ∼20% of the total world population. It is the most common cause of congenital neurological defects in humans, and an agent for devastating opportunistic infections in immunocompromised patients. To cause diseases, Toxoplasma gondii and other related parasites, such as Plasmodium falciparum, must reiterate their lytic cycle, comprising host cell infection, intracellular replication and parasite egress. At each step of the lytic cycle, the parasite tightly regulates its motility, being completely immotile while intracellular, and becoming highly motile as it leaves the host cell. Changes in local ionic conditions are known to trigger this rapid transition from immotile to motile. In this study, we report a previously unknown mechanism of regulating the motility activation in Toxoplasma, mediated by a novel protein lysine methyltransferase, AKMT (for Apical complex lysine (K) methyltransferase). The depletion of this protein greatly inhibits the parasite's ability to invade into and egress from the host cell due to impaired motility activation. Interestingly, the localization of AKMT in the parasite is sensitive to egress-stimulating signals, suggesting that AKMT regulation of parasite motility might be accomplished by the precise temporal control of its localization in response to environmental changes.

Knowledge of the biology and pathogenesis of the human parasite Entamoeba histolytica has been limited by the lack of efficient procedures to induce axenic encystation in the laboratory. However, such methods have been developed for E. invadens, a reptilian parasite, for which encystation can be induced by mechanisms that are as yet poorly defined. This has allowed the analysis of some morphological, physiological and biochemical events that accompany differentiation into cysts. Elucidation of these changes will lead to a better understanding of the process and therefore to the possibility of controlling it. Here, Everardo Lopez-Romero and Julio Cezar Villagomez-Castro emphasize the metabolism of cyst-wall polymers as a potential target to inhibit cyst formation with specific drugs that would be in principle, harmless to the host.

Yang W. , Waine G. J. , Sculley D. G. , Liu X. and McManus D. P. 1992. Cloning and partial nucleotide sequence of Schistosoma japonicum paramyosin: a potential vaccine candidate against schistosomiasis. International Journal for Parasitology 22 : 1187–1191. Paramyosin from the blood fluke, Schistosoma mansoni , has shown promise as a vaccine candidate for schistosomiasis mansoni . Here we report the cloning and partial nucleotide sequence of a cDNA encoding paramyosin from the related human parasite, Schistosoma japonicum . Affinity purified antibodies to this clone recognized a S. japonicum antigen of molecular weight 97 kDa, equivalent to the reported size of S. mansoni paramyosin. Alignment of the cDNA sequence with that of S. mansoni paramyosin revealed 90% identity. Comparison of the predicted amino acid sequences revealed 95% identity. Although these two parasites differ in many characteristics, the substantial homology demonstrated here between S. mansoni and S. japonicum paramyosin could have important implications for the development of a S. japonicum vaccine.

Schistosomiasis, which is caused by the intravascular helminth Schistosoma mansoni, is a major human parasite infection affecting a number of subtropical countries [1]. The interface between host and parasite has been extensively studied with the aim of identifying targets for vaccine-induced immunological attacks. Three reports have identified major targets of immunity on the surface of the parasite as enzymes, namely a glutathione Stransferase (GST) [2], a triose phosphate isomerase (TPI) [3,4] and a glyceraldehyde-3phosphate dehydrogenase (GAPDH), a 37-kDa antigen the cDNA of which has been cloned [5]. S. rnansoni GAPDH has been characterized as a major antigen for antibodies in the sera of the most resistant subjects to schistosomiasis [6] and has been detected on intact living schistosomula by immunofluorescence [5].

Suramin is one of the first synthetic chemotherapeutic agents to be discovered that was clinically effective against a human parasite. The road to its discovery began in 1899 when Paul Ehrlich was appointed director of the Institute for Experimental Therapy in Frankfurt, a time in which the German chemical industry was synthesizing many compounds, including a large number of synthetic dyes. One such dye, trypan red, was shown to cure trypanosomiasis in mice in 1904, the first time a parasitic infection was cured with a chemotherapeutic agent. Trypanosomes that excluded the dye were resistant [1].

Human infection by Dicrocoelium dendriticum, a zoonotic liver fluke, is uncommon and soft tissue manifestation is extremely rare. The infection has no specific clinical signs or symptoms and diagnosis may be missed completely, thus treatment may be delayed. Diagnosis in humans is by identification of the eggs in the stool, while a living or dead fluke is rarely seen. The present report concerns the case of a 7-year-old child who presented with recurrent right flank subcutaneous nodules containing a live fluke on excision, and tissue histology showed characteristic brown operculated ova of D dendriticum. This is the first extraintestinal soft tissue presentation in such a setting. It is important to know the life cycle and natural habitat of this rare human parasite in order to make a correct diagnosis and institute early treatment in patients who have become infected.

Background The Plasmodium falciparum genome (3D7 strain) published in 2002, revealed ~5,400 genes, mostly based on in silico predictions. Experimental data is therefore required for structural and functional assessments of P. falciparum genes and expression, and polymorphic data are further necessary to exploit genomic information to further qualify therapeutic target candidates. Here, we undertook a large scale analysis of a P. falciparum FcB1-schizont-EST library previously constructed by suppression subtractive hybridization (SSH) to study genes expressed during merozoite morphogenesis, with the aim of: 1) obtaining an exhaustive collection of schizont specific ESTs, 2) experimentally validating or correcting P. falciparum gene models and 3) pinpointing genes displaying protein polymorphism between the FcB1 and 3D7 strains. Results A total of 22,125 clones randomly picked from the SSH library were sequenced, yielding 21,805 usable ESTs that were then clustered on the P. falciparum genome. This allowed identification of 243 protein coding genes, including 121 previously annotated as hypothetical. Statistical analysis of GO terms, when available, indicated significant enrichment in genes involved in "entry into host-cells" and "actin cytoskeleton". Although most ESTs do not span full-length gene reading frames, detailed sequence comparison of FcB1-ESTs versus 3D7 genomic sequences allowed the confirmation of exon/intron boundaries in 29 genes, the detection of new boundaries in 14 genes and identification of protein polymorphism for 21 genes. In addition, a large number of non-protein coding ESTs were identified, mainly matching with the two A-type rRNA units (on chromosomes 5 and 7) and to a lower extent, two atypical rRNA loci (on chromosomes 1 and 8), TARE subtelomeric regions (several chromosomes) and the recently described telomerase RNA gene (chromosome 9). Conclusion This FcB1-schizont-EST analysis confirmed the actual expression of 243 protein coding genes, allowing the correction of structural annotations for a quarter of these sequences. In addition, this analysis demonstrated the actual transcription of several remarkable non-protein coding loci: 2 atypical rRNA, TARE region and telomerase RNA gene. Together with other collections of P. falciparum ESTs, usually generated from mixed parasite stages, this collection of FcB1-schizont-ESTs provides valuable data to gain further insight into the P. falciparum gene structure, polymorphism and expression.

To evaluate the factors which determine the transmission level of falciparum malaria, entomological and parasitological surveys were conducted from October 1988 to February 1990 in Manarintsoa in the central highland plateaux of Madagascar. Mosquitoes were collected for 928 man-nights in pit shelters and indoor resting sites. Malaria vectors were Anopheles arabiensis and An. funestus, with no evidence of the presence of An. gambiae sensu stricto. Vectors were mainly exophilic and zoophilic. The index of stability was < 1.5. The sporozoite rate was 0.11 for An. gambiae sensu lato and 0.47 for An. funestus. The transmission level was low, with an inoculation rate of 0.91 infective bites/person/year and an infection risk of 0.62. Malaria transmission occurs 7 months of the year in this area, from November to May. Human parasite rates fluctuated from 29% in October to 53% in May.

Groups of ferrets inoculated with Dracunculus insignis were treated with various anthelminthic compounds to evaluate the potential use of drugs in controlling the human parasite D. medinensis. The three primary compounds tested were diethylcarbamazine (DEC), albendazole (ALBZ), and ivermectin (IVER); they were administered in dosages of 60 mg/kg, 10 mg/kg, and 1 mg/kg, respectively. Groups of animals received treatment either once at 60 days after inoculation, once at 60 and 90 days, or for 3 days at either 60 or 90 days postinoculation. The most marked decrease occurred in the animals that received treatment once at 60 and at 90 days after inoculation. This was observed for all three drugs tested. Increased dosages, i.e., 3 days of treatment at 60 or 90 days did not result in decreased worm burdens. In no group was there a statistically significant reduction in worm burden when compared with controls. Two other compounds, metrifonate and CGP 6140, were tested in a more limited manner, but again the worm recovery rates were comparable with those in control groups. It would appear that existing drugs commonly used to treat helminthic infections are poor candidates for use in the campaign to eradicate guinea worm disease.

Clonorchis sinensis is a liver fluke and it is the most prevalent human parasite in Korea at present. The parasite infection induces immune responses, characteristically an increased production of parasite-specific IgE in the host. Major IgE-reacting C. sinensis antigens in infected humans have been protein bands with MWs of 15, 28, 37, 45, 51, 56, 62, 66, 74, 97 and 160 KD identified by immunoblot analysis. Individual variations of the IgE binding pattern to C. sinensis antigens have also been documented. Using immune BALB/c mouse sera, IgE-reacting protein bands have been visualized with MWs of 28, 74, 86, 160 and several > 200 KD. One of the most strongly reacted C. sinensis antigenic proteins with a molecular weight of 28 KD was purified by gel filtration and preparative electrophoresis. Using a monoclonal antibody produced against the antigenic protein, the protein was localized in the parasite's intestine, and also found to be contained in excretory-secretory antigens.

A new coccidian parasite has been found in stool specimens of humans with and without diarrhea. The oocyst of this parasite measures 8.6 microns in diameter (7.7-9.9 microns), with ovoid sporocysts 4.0 x 6.3 (3.3-4.4 x 5.5-7.1) microns. Each oocyst has 2 sporocysts and each sporocyst contains 2 sporozoites. Based on these characteristics and the structures observed by electron microscopy, this parasite has been classified in the genus Cyclospora. We propose the name Cyclospora cayetanensis n. sp. for this new human parasite.

The merthiolate-iodine-formalin (MIF) technique to detect human intestinal parasites in feces was inefficient for the detection of hookworm and Trichuris trichiura eggs. Addition of a saturated-brine flotation step increased recovery of hookworm eggs by 77% and Trichuris trichiura eggs by 87%. Recovery of Ascaris lumbricoides also was increased by 71%. This was a significant improvement in the sensitivity of the MIF technique for these 3 kinds of human parasite.

Anopheles albimanus mosquitoes were collected from August 1984 to November 1987 on intra- and peridomicile human bait in Rancheria El Gancho, Chiapas, Mexico. The mosquitoes were desiccated and stored in silicon chambers from 3 mo to 3 yr post-collection prior to being assayed using a direct enzyme-linked immunosorbent assay to detect Plasmodium vivax predominant-type sporozoite protein. Peridomicile-collected mosquitoes had a 10-fold higher sporozoite rate than those collected indoors, but only the latter correlate significantly with the seasonal human parasite index. Mosquito sporozoite burden was also significantly higher in the peridomicile-collected population.

Onchocerca volvulus is an obligate human parasite, and its study has been difficult due to an inability to maintain it outside the human host. We report the successful transplantation of onchocercomata containing living adult O. volvulus worms into immunodeficient C.B.-17.scid/scid (scid) mice or athymic rnu/rnu (nude) rats. Living, motile worms containing viable microfilariae were present in onchocercomata recovered from scid mice or nude rats for up to 20 wk, establishing a novel animal model for future investigation of O. volvulus.

Malarial parasites infecting mammalian hosts are considered to be homolactate fermentors at their asexual intraerythrocytic developmental stage; however, existing ultrastructural and biochemical evidence suggest that their acristate mitochondria could be involved in energy metabolism. In the present study, inhibitors of mitochondrial function including compounds which act on NADH and succinate dehydrogenases, electron transport and mitochondrial ATPase, as well as uncouplers, were found to inhibit the growth and propagation of the human parasite Plasmodium falciparum in in vitro cultures at concentrations that specifically affect mitochondrial functions. Direct measurement of parasite protein and nucleic acid synthesis in synchronized cultures showed that throughout the parasite life cycle both processes were inhibited, the latter process being more sensitive. These results strongly suggest that intraerythrocytic malarial parasites require mitochondrial energy production.

The insect moulting hormones, ecdysone and 20 hydroxyecdysone, were detected by the combined use of radioimmunoassay and high performance liquid chromatography in the human parasite Schistosoma mansoni. On day 11 after infection only the ecdysone form is present, but, on day 40 after infection the ratio between ecdysone and 20 hydroxyecdysone changes with anatomic localization of the adult worms in mammalian host. In the eggs, the ratio of these two hormones is identical to the ratio found in sexually mature worms located in mesenteric veins. These data demonstrate for the first time that S. mansoni synthesizes the steroid hormones ecdysone and 20 OH ecdysone which are potent molecules in stimulating growth and vitello-genesis of this gonochoric trematode.

In sera from patients with fascioliasis the enzyme-linked immunosorbent assay (ELISA) was used to detect antibody using excretory-secretory products (ES) from Fasciola hepatica adult worms. The specificity of ES-ELISA (with OD values greater than 0.38) allowed the differentiation among fascioliasis, schistosomiasis, clonorchiasis, and other human parasite infections.

We have used a sporozoite neutralization assay to define the biological relevance of the cross-reactivity of two monoclonal antibodies, raised against sporozoites of the human parasite Plasmodium malariae (Uganda 1/CDC), with sporozoites of the simian parasite Plasmodium brasilianum (Colombian). In vitro incubation of each of these two monoclonal antibodies with sporozoites of P. brasilianum totally abolished the infectivity of these parasites for Saimiri sciureus. Using Western blot analysis and one of the P. malariae monoclonal antibodies, we identified two sporozoite proteins characteristic of the Colombian isolate of P. brasilianum with apparent molecular weights of 56,000 and 66,000. The same monoclonal antibody identified two proteins in an extract of the Peruvian isolate of P. brasilianum with apparent molecular weights of 59,000 and 69,000.

Mouse red blood cells (RBCs) infected with the malaria parasite Plasmodium yoelii nigeriensis were shown to synthesize a histidine-rich protein (His-RP) in vitro. The existence of this protein was demonstrated by comparing fluorograms of infected red blood cells (IRBCs) labelled with either [14C]histidine or [14C]leucine. The molecular weight of this His-RP was estimated to be 43,500, which compares well with the values reported for the avian parasite P. lophurae (45,000) and for the human parasite P. falciparum (42,000). This result supports the idea that such a protein may play an important role in the biology of all plasmodium species.

1. 1. DNA from various rodent Plasmodium species and strains and from P. falciparum , the human parasite, were analysed by agarose gel electrophoresis following digestion with restriction endonucleases EcoRI, Hind III and Bam H1. Complex patterns of ethidium-stained bands were obtained, which showed similarity but reproducible differences among the various parasite species ( P. chabaudi, P. yoelii, P. berghei and P. falciparum ). 2. 2. No differences could be discerned among two cloned strains of P. yoelii (33X, and YM) and among pyrimethamine-resistant (pyrimethamine + chloroquine)-resistant and the drug-sensitive P. chabaudi clone from which the resistant clones were derived. 3. 3. From the known complexity of Plasmodium DNA it could be concluded that the visible bands were derived from repetitive DNA fractions.

Summary In this work, Trypanosoma ariarii, n. sp., has been described. This human parasite, found in the River Ariari Valley, Colombia, is characterized by an average size of 31 microns (in blood films), a nucleus anterior to the equator of the body, and a round, small, subterminal kinetoplast. T. ariarii shows division stages in the peripheral blood. Until now we have not found evolutionary forms in the viscera or tissues of experimental animals. Cebus fatuellus and the domestic dog have also been found naturally infected with T. ariarii. R. prolixus is experimentally infected quite easily with this protozoon. Also T. ariarii is cultivated in vitro without difficulty. So far, using parasites grown in cultures, we have only succeeded in infecting a few baby mice, two opossums (Didelphys paraguayensis paraguayensis), one rhesus monkey and human volunteers. During the period of observation (11 and 15 months) the experimental infection followed an asymptomatic course in the two volunteers in whom the infection was established. The frequency of human cases infected with T. ariarii in the Ariari Valley seems to be high. Out of 183 persons examined by blood cultures, 67 showed trypanosomes. It was possible to study completely the parasites isolated from 27 of these 67 infected people. The results were: 1 case with a mixed infection of both T. cruzi and T. ariarii, and 26 cases with single T. ariarii infections.

Summary 1. The authors experimentally infected themselves with the sparganum larva of Spirometra mansonoides on November 26, 1938, by introducing the heads of three larvae beneath the skin of the left arm over the biceps muscle, two into Mueller, one into Coulston. These heads measured at most 2 mm. in length. 2. On February 2, 1939 a sparganum 50 mm. in length, representing a growth of 48 mm., was removed from Coulston's arm after it had migrated from the site of injection to the region of the axilla, a distance of about 12 cm., where it was found under the deep fascia. 3. On February 3, 1939 a sparganum 60 mm. long, representing a growth of about 58 mm., was removed from the biceps muscle of Mueller under local anesthetic. Only a fragment of the tail end of the other worm, about 10 mm. long, could be found at this time. 4. On March 4, 1939, a second sparganum about 60 mm. long was removed from Mueller. 5. This last sparganum was fed to an ova-free, known unin-fected cat, and produced a normal adult worm 50 inches in length. Ova of this worm were cultured and the procercoids found infective for rhesus monkeys demonstrating that the worm had not suffered any loss of vigor by human passage. 6. Symptoms associated with infection were local induration at the site of the worm, periodic giant urticaria, edema, and erythema. These periodic symptoms appeared to coincide with movements of the worm which from time to time broke out of the surrounding reaction zone, presumably liberating into the circulation walled off toxins. These periodic local reactions were attended by chills and fever and feelings of profound depression and malaise. 7. Eosinophilia appeared, rising to 10 per cent in Mueller on the 32nd day, and to 9 per cent in Coulston on the 23rd to the 27th day. 8. A positive skin reaction was elicited to scratch tests or intradermal tests with antigens prepared from Spirometra mansonoides adult and sparganum, T. crassicollis adult and cysticercus, T. pisiformis adult and cysticercus, and T. serrata. Also with the substance of a plerocercoid found in Great Lakes ciscoes. Antigens for intradermal use were prepared by Dr. J. T. Culbertson of Columbia University. They were not lipid free. 9. While the subjects were still infected skin testing did not elicit any immediate reaction, only delayed reaction after about 10 or 12 hours. 10. After removal of the worms the subjects developed an immediate reaction to skin tests, while retaining the delayed reaction. The delayed reaction in the case of the scratch tests is recurrent several times at 10 to 12 hour intervals. 11. In over 60 control skin tests on volunteers only one “false positive” was obtained, and that in the case of a student who gave a history suggesting that he may at one time have been infected with a sparganum. 12. The two authors still show strongly positive reactions to skin tests at the present writing (January 8, 1941), almost 20 months after removal of the worms. 13. Complement fixation tests were unsatisfactory on the two experimentally infected humans, possibly because of the employment of too weak an antigen, or more probably because the serum was kept for too long a time before performing the tests. 14. Pathological changes were extensive and in the nature of chronic inflammatory reaction, with local necrotic areas surrounding the worm. 15. In both subjects the spargana exhibited migration, in one case penetrating and forming a gallery in the biceps muscle, in the other passing to the region of the axilla. Encapsulation though extensive was not sufficient to wall off the spargana. 16. With the establishment of Spirometra mansonoides as a potential human parasite physicians throughout the geographic range of the worm should be informed of its nature and educated to watch out for it. The use of antigens of tapeworm substance for diagnosis is recommended. 17. It further appears that this parasite may constitute another potential waterborn disease throughout its range in the eastern United States, and render swimming in certain natural bodies of water carrying the copepod intermediate host, or the use of shallow well or spring water, etc., dangerous. 18. Such antigens as we used are not specific, since they retain the lipid fraction. Spirometra antigens elicited positive reactions in hydatid disease patients. It is probable that a more specific antigen can be prepared by preliminary removal of the lipids before extraction.

(1924). A Pig Nematode, Gnathostoma Hispidum, Fedchenko, as a Human Parasite. Annals of Tropical Medicine & Parasitology: Vol. 18, No. 1, pp. 23-26.

Thirty species of helminths were found in material from Alberta rodents and lagomorphs. It was shown that Capillaria hepatica, a potential human parasite of high pathogenicity, occurs in Peromyscus maniculatus (a new host record) and in Thomomys talpoides, and is common throughout the entire province of Alberta.

Papio cynocephalus from French Guinea frequently harbours Loa papionis n.sp. The intermediate host is unknown. The larvae, in contradistinction to those of the human parasite Loa loa, show no diurnal periodicity.The occurrence of bacterial disease in adult L. papionis would seem to be a novelty; at any rate I could find no mention of diseased filariae in the literature.In so far as the biology of Microloa loa is concerned, I am inclined to doubt the correctness of the opinions expressed by Rodenwalt and Fülleborn concerning the structures they term “executory and genital cells”: the current hypotheses concerning the significance of these structures and of the “central viscus,” clearly need revision. Manson's “buccal apparatus” would seem to be nothing more than an optical illusion, while the “neck” or “shoulder” described by the older observers as existing in adult L. loa after fixation, was evidently due to imperfect technique.I have drawn attention to the desirability of standardising the technicalities which are such essential preliminaries to the accurate mensuration of micro-filariae, and have suggested a method which has certain advantages over those at present in use.Concerning the pathology of Loa infection, evidence both of the traumatic and toxic action of L. papionis on baboons, was obtained; moreover these parasites seemed definitely toxic for guineapigs, although the single experiment performed needs confirmation. The available evidence favours the supposition that adult baboons from an infected area possess a high degree of immunity both against L. papionis toxaemia and against reinfection by these parasites; but whether their serum is of therapeutic value for human beings infected with L. loa, requires further investigation.

Interactions between Trypanosoma cruzi and the extracellular matrix play an important role in cellular invasion. Here we show that T. cruzi increases the levels of thrombospondin-1 (TSP-1) expression in host cells during early infection. Stable RNA interference of host cell TSP-1 knocks down the levels of TSP-1 transcripts and protein expression in mammalian cells causing inhibition of T. cruzi infection. Addition of TSP-1 to these cells restores infection. Thus, host TSP-1, regulated by the parasite, plays a crucial role in early infection. This is the first report showing that a human parasite modulates TSP-1 expression to facilitate infection.

The accumulation of knowledge on the cellular immunology of host parasite relationships can be very rapid when infection of mice with a human parasite causes a disease resembling that seen in man. This is so of Old World cutaneous leishmaniasis (‘oriental sore'). As must be the case in all chronic infectious diseases, manifestations of the clinical disease spectrum in cutaneous leishmaniosis reflect both host and parasite factors. In this article Graham Mitchell describes how this spectrum can be exploited in inbred mice injected with isolates of Leishmania trop ica major ( L. major ) for detailed analysis of interactions between host and parasite.

The human parasite Trypanosoma brucei gambiense grew continuously at 37 degrees C in primary cultures of murine bone marrow. Cultured parasites remained virulent for mice. Rapid parasite growth coincided with the appearance of adherent adipocyte-epitheloid cell aggregates that also promoted hematopoiesis. This culture system should permit studies of host cell control of trypanosome proliferation, pathogenic effects of trypanosomes on blood cell development, and the relative trypanocidal and marrow suppressive activities of drugs.

Out of 643 collections of the brown dog tick, Rhipicephalus sanguineus (Latreille), from the United States only 13 were from humans and only 4 of these were biting records. A host-preference study for this species of tick showed 3.5% of the larvae tested, 2% of the nymphs, and 5% of the adults were induced to attach to humans after 24 hours. These figures are in contrast to 25% of the larvae, 57.7% of the nymphs, and 59.5% of the adults that attached to guinea pigs and 21.3% of the larvae, 61.1% of the nymphs, and 38.1% of the adults that attached to dogs over the same period of time. These observations indicate that R. sanguineus is not a major human parasite.

Since the discovery of the parasite Kala Azar by Lt.-Col. Leishman, R.A.M.C., a number of investigators have endeavoured to reproduce the disease in the lower animals but without success. The recent discovery of Nicolle that dogs are susceptible to an allied human parasite (Herpetomonas infantum) has added a fresh stimulus to work along these lines, and in order to see whether the dog can be infected with H. donovani I carried out some inovulation experiments, which I propose recording in this paper.

The structure of ribosomal DNA (rDNA) clone pBmr7 from microfilariae of the human parasite Brugia malayi has been examined in detail by Southern blot analysis and S-1 mapping techniques. The results demonstrate that this clone contains regions homologous to 28S, 18S and 5.8S rDNAs. A noncoding or ‘spacer’ region lies between the 3′ end of 28S rDNA and the 5′ end of 18S rDNA. An AceI-Sau3AI fragment of approximately 900 bp from this spacer region cross-hybridizes to genomic DNA fragments of different sizes from Brugia pahangi and Dirofilaria immitis. The differences observed in hybridization suggest that this rDNA fragment can be used to differentiate between various filariid species.

Vaccination against cutaneous leishmaniasis has long been practiced. Accounts in the literature suggest that from as early as the 19th Century children in Baghdad had been vaccinated against “Oriental Sore”, by inoculating material from active human lesions into the skin of the arm or thigh (Wenyon, 1911). In this way long-lasting immunity could be induced and the likelihood of developing disfiguring facial scars avoided. To my knowledge there has been only one vaccination study on human visceral leishmaniasis caused by L. donovani. Manson-Bahr (1961) reported that inoculation with a non-visceralising ground squirrel strain of L. donovani protected against challenge with the human parasite. The ground squirrel parasite has, in fact, been identified as L. major using biochemical and serological methods (Chance et al., 1978). However, the use of live material is subject to obvious drawbacks, scarring is inevitable at the site of inoculation and there is always the possibility of a particularly susceptible recipient developing a chronic or severe infection. The problems inherent in the use of virulent vaccines have stimulated trials using attenuated parasites or parasite fractions. Although these have proved disappointing with regard to Old World cutaneous leishmaniasis, recent field trials in South America have produced encouraging results. Using a vaccine consisting of equal parts heat-killed and sonicated promastigotes from five different parasite isolates, Mayrink et al (1985) successfully and significantly protected from infection 70% of the participants that became skin-test positive following vaccination.

Leishmania donovani, the etiological agent of human visceral leishmaniasis, was grown in hamster peritoneal macrophages in vitro. By electron microscopy, using a lysosomal marker, these parasitic protozoa were seen to multiply within host cell phagolysosomes. The survival mechanism of this intracellular parasite is based apparently upon resistance to macrophage lysosomal enzymic digestion.

Little is known about the mechanisms that control transformations during the life cycle of Schistosoma mansoni. To enable isolation of DNA sequences encoding developmentally regulated antigens a cDNA expression library in the vector lambda gt11 amp3 was constructed from adult mRNA and immunologically screened with sera from infected individuals. We report here on the properties of three recombinant clones that derive from developmentally regulated genes. Clone 10-3 encoded a beta-galactosidase fusion protein present in high abundance in infected Escherichia coli. Clones 7-2 and 8-2 also produced immunologically recognized proteins; however, the peptides did not appear to be beta-galactosidase fusion proteins. The expression of mRNAs hybridizing to these cDNAs was examined in the different stages of the parasite life cycle. Messenger RNA corresponding to clone 10-3, approximately equal to 1000 bases in length, was present in higher abundance in male worms than in females but was not detected in schistosome eggs. A 900-base mRNA hybridizing to clone 7-2 was observed in adult worms and eggs. Both clone 10-3 and clone 7-2 hybridized to smaller mRNAs in cercariae and freshly transformed schistosomula than in adult worms. Clone 8-2 contained tandem cDNA inserts. One cDNA hybridized to a 1700-base mRNA present in all stages, while the second hybridized to an 800-base mRNA specific to adult female worms.

Publisher Summary This chapter analyzes the interrelationships between Epstein-Barr herpes virus (EBV) and primates other than man. It also discusses the aspects of the discovery of the virus, its association with Burkitt lymphoma, infectious mononucleosis, and nasopharyngeal carcinoma, and its biologic properties studied in vitro . The studies of EBV in nonhuman primates have been useful in many respects. They have provided clues about the evolution of this highly adapted human parasite. Infection of nonhuman primate cells in vitro has yielded a regular source of cell-free virus for laboratory studies and has also clearly demonstrated the importance of host-specified control mechanisms in the regulation of the expression of viral information in transformed cells. The experimental infection of primates was successful once adequate amounts of transforming virus were available and once the virus host range was better defined by the means of in vitro transformation. Subsequent study allowed a direct demonstration of the capacity of EBV to cause lymphoreticuloproliferative disease. The identification of susceptible primate hosts now offers promise of the detailed analysis of the pathogenesis of EBV-induced disease and of the comparison of the pathogenic properties of different EBV-related viruses.