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PubMed1997

Protective monoclonal antibody defines a circumsporozoite-like glycoprotein exoantigen of Cryptosporidium parvum sporozoites and merozoites.

The apicomplexan protozoan parasite Cryptosporidium parvum causes a diarrheal disease in humans and other mammals for which specific therapy and immunoprophylaxis are unavailable. Passive immunization with Abs against whole C. parvum organisms has variable efficacy in immunocompromised or neonatal hosts. Because apical and surface-exposed zoite Ags of the Apicomplexa are critical to infectivity and targets of protective immunity, we examined the ability of mAbs generated against such Ags in C. parvum sporozoites to passively protect against infection and identify biologically relevant parasite molecules. A panel of mAbs was produced against affinity-purified native Ags using sporozoite apical- and surface-reactive mAb C4A1 as binding ligand. One resulting mAb, designated 3E2, elicited prominent morphologic changes in sporozoites and merozoites characterized by rapid and progressive formation, posterior movement, and release of membranous Ag-mAb precipitates. These changes had a striking resemblance to the malarial circumsporozoite precipitate (CSP) reaction. Sporozoite infectivity was completely neutralized after in vitro exposure to 3E2 and the CSP-like reaction. Furthermore, orally administered 3E2 completely prevented or markedly reduced infection in neonatal BALB/c mice. 3E2 bound to apical complex and surface molecules of zoites and was demonstrated in membranous precipitates by immunoelectron microscopy. In Western blots, 3E2 recognized multiple 46 to approximately 770 kDa sporozoite Ags and an approximately 1300-kDa Ag designated CSL, also expressed by merozoites. CSL was characterized as a soluble glycoprotein exoantigen released by infectious sporozoites. Further, CSL was determined to be the molecular species mechanistically involved in the CSP-like reaction by its identification in SDS-PAGE gels and Western blots of purified membranous precipitates. These findings indicate that CSL has a functional role in sporozoite infectivity and is a candidate molecular target for passive or active immunization against cryptosporidiosis.

Animals↗
PubMed1996

[Experimental infection of mice with Babesia microti: characterization of parasitemia].

The apicomplexa parasites of the genus Babesia, the etiologic agents of the disease not only in domestic and wild mammals but also in humans, live and reproduce in erythrocytes of the host. Transmission of Babesia species is by tick (Ixodidae) bite. In natural conditions, trans-stadial and trans-ovarian passage occurs in Ixodes ricinus infected with some species of Babesia, e.g. B. divergens. However, there is apparently trans-stadial passage of B. microti in Ixodes sp. only from larvae to nymphs, but trans-stadial passage from nymphs to adults or trans-ovarian passage has not been reported. The present study was undertaken to compare the parasitemia of B. microti infection in BALB/c and F1 (B10 x CBA) mice by two different methods: intraperitoneal injection of parasites or infection by the oral route. In both groups, experimental mice were inoculated with 5 x 10(7) infected erythrocytes in 100 microliters of blood. Babesia infection was acquired by all mice infected intraperitoneally with maximum 57% of parasitemia on day 6 post infection (pi) in F1 (B10 x CBA) mice and 40% of parasitemia on day 8 and 10 pi in BALB/c mice. Ten of 27 (37%) BALB/c mice infected by oral route showed low parasitemia (9%) during first two weeks pi. In this group of mice the pick of parasitemia (26%) was observed on day 22 pi. In both groups of infected mice the period of prepatency ended between days 35 and 40 pi. Experiments have confirmed that the maintenance of babesiosis may be continued in the absence of a tick vector. Demonstration, under experimental conditions, of infection of Babesia by oral route may suggest that in nature cannibalism of rodents, occurring under certain circumstances, can be considered as a natural way of oral transmission of B. microti.

Animals↗
PubMed1997

A guideline for the preparation of species descriptions in the Eimeriidae.

Members of the suborder Eimeriina (phylum Apicomplexa: class Sporozoea: order Eucoccidiorida) have complex 1 or 2 host life cycles that involve endogenous development in the tissues of vertebrates or invertebrates and exogenous development in an oocyst, usually outside the host(s). Because tissue stages are logistically difficult or even impossible to obtain in natural (wild) host-parasite systems, the vast majority (> 98%) of species in this parasite complex are known only from the structure of their sporulated oocyst. Unfortunately, the quality of these species descriptions is uneven because no guidelines are available for workers in the field to follow. Here we propose a specific set of guidelines for the preparation of species descriptions of coccidia based predominently on the structure of the sporulated oocyst, because the oocyst is the most readily available stage in the life cycle. In addition, we emphasize that ancillary data be incorporated whenever possible with the species description; these data may include, but are not limited to, ecological parameters, prevalence, seasonal data, and the deposition of both host symbiotypes and parasite hepantotypes (= phototypes) into accredited musecums so that accurate identification of both host and parasite material can be assured in perpetuity. And finally, if oocysts are collected in pure suspension, that is, if only one coccidian species (morphotype) is present in the sample, then some oocysts should be saved in 70% ethanol and archived in an accredited museum in the event that future workers might wish to amplify and, later, sequence the parasite's DNA.

Animals↗
PubMed1997

Pulmonary disease in selected protozoal infections.

Protozoa of the phylum Apicomplexa, including the genera Plasmodium, Babesia, Toxoplasmosis, and Cryptosporidium, are a group of closely related organisms that seldom cause pulmonary disease. All but Babesia are members of the subclass Coccidiasina ("Coccidians"). (The fungal organism Coccidioides immitis, a frequent cause of pulmonary disease in endemic areas, was first believed by Rixsford and Gilchrist to be a member of the subclass Coccidiasina; hence its name, meaning coccidioidal-like). Some species, such as Toxoplasma gondii, occasionally cause pulmonary disease by directly infecting lung parenchyma, whereas others, such as Cryptosporidium and Microsporidium, can be occasionally visualized in respiratory secretions or lung biopsy specimens, but their role in causing respiratory disease in human beings is more questionable. In contrast, pulmonary disease associated with infections caused by Malaria and Babesia is often the result of a systemic inflammatory response.

Animals↗
PubMed1997

Discrimination of eight chicken Eimeria species using the two-step polymerase chain reaction.

A method was developed for the discrimination of 8 Eimeria species of chickens, i.e., E. acervulina, E. brunetti, E. mitis, E. maxima, E. necatrix, E. praecox, E. tenella, and E. hagani using the 2-step polymerase chain reaction (PCR). In the first PCR, the small subunit ribosomal RNA (srRNA) gene was amplified from the parasite genome using conserved sequences for the Apicomplexa srRNA gene as the primers. The srRNA gene amplified from the parasite genome was discriminated in the second step by random-amplified polymorphic DNA (RAPD) PCR using 10 arbitrary primers. Each arbitrary primer produced species-specific RAPD patterns that provided a simple method for species identification from the srRNA genes of the 8 Eimeria species. This method should be useful for discrimination of the parasite species for diagnosis or epidemiological surveys of chicken coccidiosis.

Animals↗
PubMedDate not supplied

[The prevalence of cryptosporidia among agricultural animals in Azerbaijan].

In the paper are presented the data on revealement of cryptosporidian oocysts (Apicomplexa, Sporozoa) in feces of cattle, swine and sheep of different ages and results of the experimental infection of laboratory animals (rats, mice, rabbits, coypus) with the oocysts detected as well. The latters were attributed to Cryptosporidium parvum species. The analysis of the size characteristic in the isolates of naturally and artificially infected hosts has shown that the oocysts dimensions might vary both in different host species and in different individuals of one host species.

Animals↗
PubMed1976

Ultrastructure of Babesia major in the tick Haemaphysalis punctata.

Haemaphysalis punctata ticks were infected with Babesia major by allowing them to feed on an infected splenectomised calf. Heavily infected ticks were dissected and the guts and the ovaries were processed to study the ultrastructure of B major in these organs. The morphology of the parasites in the gut and the ovary was identical. It was shown that the parasite contained a reduced form of an apical complex consisting of characteristic organelles such as the polar ring, rhoptries, micronemes and microtubules. A primitive conoid was situated at the anterior end of the parasite and consisted of delicate helical rings. The occurrence of these organelles confirmed the inclusion of this parasite in the subphylum Apicomplexa.

Animals↗
PubMed1998

Light and electron microscope studies of Hepatozoon mehlhorni, Bashtar et al., 1991 (Adeleina, Eucoccidiida) naturally infecting the viper Echis carinatus.

Light and electron microscopy have been used to study blood stages of H. mehlhorni as well as different developmental stages of the parasite within lung tissues of the naturally infected vipers Echis carinats captured from Siwah Oases, Egypt. A natural infection rate of 60% was recorded among vipers. Two types of meronts were observed within the endothelial cells of the viper's lung. The first type is the small one, produced 6-15 merozoites. The second type is the large one, produced 20-40 merozoites. In both types of meronts, merozoites were developed through an ectomerogenous manner. The erythrocytic parasites and the merozoites within the endothelial cells of the viper's lung sharing all general architecture of the apicomplexa. Moreover, evident peculiarities of haemogregarines were recorded, such as the presence of micronemes and rhoptries on both sides of the parasite nucleus, and the presence of large number (up to 100) of subpellicular microtubules and micronemes (up to 150).

Animals↗
PubMed1981

Nosematosis of the cornea. Case report, including electron microscopic studies.

A 26-year-old woman underwent enucleation of a blind, painful eye because of a perforated corneal ulcer. Histopathologic examination of the eye disclosed an acute, necrotizing keratitis surrounding myriad small (2.5 to 3 x 4.5 to 5 micrometer), oval, faintly visible structures. Under polarized light, they were partially birefringent and stained intensely positive with the acid-fast technique. The organisms were located mainly within the cytoplasm of histiocytes in the deep corneal lamellae. They were interpreted as a protozoa of the genus Nosema. The diagnosis was confirmed by electron microscopic studies. The distinguishing features between Nosema species and Encephalitozoon are discussed. To our knowledge, this is the second documented case of corneal nosematosis.

Adult↗
PubMed1997

Plastids in parasites of humans.

It has recently emerged that malarial, toxoplasmodial and related parasites contain a vestigial plastid (the organelle in which photosynthesis occurs in plants and algae). The function of the plastid in these obligate intracellular parasites has not been established. It seems likely that modern apicomplexans derive from photosynthetic predecessors, which perhaps formed associations with protists and invertebrates and abandoned autotrophy in favour of parasitism. Recognition of a third genetic compartment in these parasites proffers alternative strategies for combating a host of important human and animal diseases. It also poses some fascinating questions about the evolutionary biology of this important group of pathogens.

Animals↗
PubMed2002

Myosins of Babesia bovis: molecular characterisation, erythrocyte invasion, and phylogeny.

Using degenerate primers, three putative myosin sequences were amplified from Australian isolates of Babesa bovis and confirmed as myosins (termed Bbmyo-A, Bbmyo-B, and Bbmyo-C) from in vitro cultures of the W strain of B. bovis. Comprehensive analysis of 15 apicomplexan myosins suggests that members of Class XIV be defined as those with greater than 35% myosin head sequence identity and that these be further subclassed into groups bearing above 50-60% identity. Bbmyo-A protein bears a strong similarity with other apicomplexan myosin-A type proteins (subclass XIVa), the Bbmyo-B myosin head protein sequence exhibits low identity (35-39%) with all members of Class XIV, and 5'-sequence of Bbmyo-C shows strong identity (60%) with P. falciparum myosin-C protein. Domain analysis revealed five divergent IQ domains within the neck of Pfmyo-C, and a myosin-N terminal domain as well as a classical IQ sequence unusually located within the head converter domain of Bbmyo-B. A cross-reacting antibody directed against P. falciparum myosin-A (Pfmyo-A) revealed a zone of approximately 85 kDa in immunoblots prepared with B. bovis total protein, and immunofluorescence inferred stage-specific myosin-A expression since only 25% of infected erythrocytes with mostly paired B. bovis were immuno-positive. Multiplication of B. bovis in in vitro culture was inhibited by myosin- and actin-binding drugs at concentrations lower than those that inhibit P. falciparum. This study identifies and classifies three myosin genes and an actin gene in B. bovis, and provides the first evidence for the participation of an actomyosin-based motor in erythrocyte invasion in this species of apicomplexan parasite.

Actins↗
PubMed1987

Bovine cytotoxic T cell clones which recognize lymphoblasts infected with two antigenically different stocks of the protozoan parasite Theileria parva.

The Muguga and Marikebuni stocks of Theileria parva differ on the basis of cross-protection and in their schizont antigen profile determined with a panel of parasite-specific monoclonal antibodies. The phenotype and specificity of six cytotoxic T cell clones generated from an animal immunized against T. parva (Marikebuni) were investigated. All six clones had the BoT2+ BoT4- BoT8+ phenotype, were dependent on both specific antigen and T cell growth factor for proliferation and were restricted by determinants on class I major histocompatibility complex molecules. The clones killed target cells infected with either the Muguga or Marikebuni stocks of the parasite; the target cell lines tested included T cell clones which were infected in vitro with the two parasite stocks and subsequently recloned. The specificity of these cytotoxic T cell clones contrasts with that of T cell clones generated previously from animals immunized against T. parva (Muguga), in that the latter were specific for target cells infected with the Muguga stock of the parasite. Moreover, one of the clones generated against T. parva (Marikebuni) was restricted by the same major histocompatibility complex molecule as the Muguga-specific T cell clones. The difference in parasite strain-specificity between the two sets of clones appears to reflect the capacities of the two parasite stocks to cross-protect, since animals immunized against T. parva (Marikebuni) are protected against challenge with T. parva (Muguga) whereas a proportion of animals immunized with T. parva (Muguga) are susceptible to challenge with T. parva (Marikebuni). Another difference between the two sets of T cell clones was that those generated against T. parva (Marikebuni) only killed a proportion of cells of a given cell line in a 4-h cytotoxicity assay, whereas Muguga-specific T cells invariably kill the majority of cells. However, despite this partial killing, the clones markedly inhibited growth of parasitized cell lines when cultured with them for a period of 5 days.

Animals↗
PubMed1991

Lymphocytes infected with Theileria parva require both cell-cell contact and growth factor to proliferate.

Lymphocytes infected with the intracellular parasite Theileria parva proliferate continuously as lymphoblastoid cell lines. We have previously shown that the continuous proliferation of the T. parva-infected (Tpi) cell line TpM(803) is mediated in part by an autocrine mechanism (Dobbelaere, D. A. E. et al., Proc. Natl. Acad. Sci. USA 1988. 85:4730). We now report that continuous proliferation also requires surface stimulation through cell-cell contact. Under standard culture conditions this surface stimulus is provided by the infected cells themselves, but it can also be provided by uninfected lymphocytes or macrophages. The ability to respond to surface stimulation is critically dependent on the presence of the parasite in the host cell and is lost within 48 h after the elimination of the parasite from the host cell cytoplasm by treatment with the theilericidal drug BW720c. Tpi cells also secrete a growth factor which is able to support the proliferation of diluted Tpi cells. Growth factor secretion is rapidly lost upon elimination of the parasite. Moreover, inhibition experiments using anti-interleukin 2 (IL 2) antibodies show that IL 2 is involved in the proliferation of the Tpi cell lines TpM(803) and IN10. T cell proliferation is dependent on a number of costimulatory signals which are normally provided by accessory cells. The finding that Tpi cells can mutually stimulate each other to grow in the absence of conventional accessory cells helps to explain how they can escape the normal constraints on T cell growth, allowing them to invade and multiply in non-lymphoid as well as lymphoid tissues.

Animals↗
PubMed2002

Effects of plasma from bivalve mollusk species on the in vitro proliferation of the protistan parasite Perkinsus marinus.

The in vitro culture of the Eastern oyster parasite Perkinsus marinus has provided a unique opportunity to examine its susceptibility to putative recognition and effector defense mechanisms operative in refractory bivalve species. In this study, we report the effect of supplementing the culture medium with plasma from: (1) uninfected to heavily infected Eastern oysters; (2) oyster species considered to be disease-resistant; and (3) bivalve mollusk species that are naturally exposed to the parasite but show no signs of disease. We also examined in vitro the interaction between hemocytes from Crassostrea virginica and C. gigas and P. marinus trophozoites. Our results revealed a significant decrease (32%) in proliferation of P. marinus in the presence of plasma from heavily infected C. virginica oysters. The inhibitory effects were less pronounced with plasma from moderately infected and uninfected oysters. In contrast, plasma from C. rivularis and C. gigas enhanced P. marinus proliferation. Proliferation was significantly reduced in media supplemented with plasma from Mytilus edulis, Mercenaria mercenaria, and Anadara ovalis. The highest inhibitory activity was apparent in M. edulis, for which 5% plasma-supplemented medium reduced growth by 35% relative to the controls. M. edulis active component(s) was heat-stable, yet pronase-sensitive. The significantly higher uptake of live P. marinus trophozoites by hemocytes from C. virginica, relative to those from C. gigas, suggests a certain level of specificity in the recognition/endocytosis of the parasite by its natural bivalve host species.

Adaptation, Physiological↗
PubMed2000

Direct immunization of malaria DNA vaccine into the liver by gene gun protects against lethal challenge of Plasmodium berghei sporozoite.

The liver is the first target organ for malaria parasites immediately after the bite of an infected mosquito. We studied local immunization of malaria DNA vaccines at the site of the liver using a gene gun as a useful tool for in vivo transfection of foreign genes. A malaria DNA vaccine consisting of the Plasmodium berghei circumsporozoite protein (PbCSP) gene plus the mouse IL-12 gene was bombarded directly by a gene gun into mouse liver once or into the skin twice. A marked protective effect was induced by gene bombardment into the liver (more than 71%) compared with that into the skin (less than 33%). A Th1-type immune response and high production of iNOS were observed in the hepatic lymphocytes from mice bombarded into the liver, resulting in more effective protection compared with those bombarded into the skin. These results provide an important implication on the development of efficient malaria vaccine strategies.

Amino Acid Sequence↗