Immunization of mice with irradiated Trypanosoma cruzi grown in cell culture: Relation of numbers of parasites,immunizing injections,and route of immunization to resistance

Mice were given 5 or 8 weekly injectins of either 2·0 × 10⁶ or 20·0 × 10⁶ irradiated T. cruzi from cell culture (ratio of trypomastigotes to amastigotes, 1 : 1) via the intraperitoneal route or via the subcutaneous route and challenged via the subcutaneous route one week after the last injection with 5·0 × 10⁴T. cruzi in mouse blood. The irradiated parasites used were not capable of producing infections in either Vero cell cultures or C₃H mice. Mice receiving irradiated parasites were significantly protected against the challenge infection as evidenced by significantly lower mean parasitemia, lessened signs of acute disease, and reduced mortality than that observed in untreated controls. Mice receiving 5 weekly immunizing injections of irradiated parasites were more resistant to challenge than those receiving 3 in previous work. Mice receiving 8 weekly immunizing injections were not significantly more protected against challenge than those receiving 5. Mice given 5 weekly injections of 20·0 × 10⁶ irradiated parasites were significantly more resistant to challenge than those receiving 2·0 × 10⁶ irradiated parasites on the same schedule. Mice given 5 weekly intraperitoneal injections of 20·0 × 10⁶ irradiated parasites were significantly more resistant to challenge than those receiving an equivalent number of immunizing injections via the subcutaneous route.     

Trypanosoma cruzi: Lactate dehydrogenase isoenzymes and infections in mice

Total plasma LDH isoenzyme (EC 1.1.1.27) levels increased significantly over the normal level in mice infected with strains of Trypanosoma cruzi from three different geographic locations, but some strain differences were observed. The most rapid increase was exhibited by the blood-induced Tulahuen strain, but this strain, unlike the House 510 or House 11, did not elicit an increase during the early period of infection. Overall increases in LDH-1 and LDH-2, heart isoenzymes, were most marked in vector-derived House 510 infections, but, as in the Tulahuen strain, a considerable increase was also observed in blood-induced infections. The House 510 strain also elicited significant increases in LDH-4; these were particularly high during the early period of the blood-induced infection. By contrast, the vector-derived Tulahuen strain elicited a higher increase in LDH-4 during the early period than the House 510 or House 11 strains. Comparable similarites and differences were also observed in regard to LDH-3, 5, and “X.” The most marked isoenzyme increases were those of “LDH-X” exhibited by the blood-induced House 510 and vector-derived Tulahuen strains.Parallel histopathologic studies of liver, heart, and skeletal muscle disclosed significant pathology in all the infections. Animals with blood-induced Tulahuen strain infections characteristically showed extensive necrosis with marked multiplication of parasites throughout the liver, but little or no evident damage to the heart and skeleal muscle. Animals infected with House 510 and House 11 strains exhibited minimal pathology in the liver but severe damage to the heart and skeletal muscle. Increases in LDH-4 and LDH-5, isoenzymes which represent both liver and skeletal muscle, in blood-induced Tulahuen infections were attributed largely to liver damage, but in the House 510 and House 11 infections were related more to skeletal muscle.     

Blood parasites of House Finches (Carpodacus mexicanus) from Georgia and New York

This study investigated the ecology of hematozoan parasites in two eastern populations of House Finch (Carpodacus mexicanus). Blood smears were obtained from birds captured in Georgia during 2001-2003 (n = 757) and New York during 2001 (n = 282) and evaluated for the presence of hematozoans. Low-density infections of Haemoproteus fringillae and Plasmodium relictum were confirmed at each location. Infections were observed year-round in Georgia, but primarily between June and November in New York. Overall, hematozoa were more prevalent in House Finches from Georgia than New York (P 相似文献   

House Fly (Musca domestica L.) Attraction to Insect Honeydew

House flies are of major concern as vectors of food-borne pathogens to food crops. House flies are common pests on cattle feedlots and dairies, where they develop in and feed on animal waste. By contacting animal waste, house flies can acquire human pathogenic bacteria such as Escherichia coli and Salmonella spp., in addition to other bacteria, viruses, or parasites that may infect humans and animals. The subsequent dispersal of house flies from animal facilities to nearby agricultural fields containing food crops may lead to pre-harvest food contamination with these pathogens. We hypothesized that odors from honeydew, the sugary excreta produced by sucking insects feeding on crops, or molds and fungi growing on honeydew, may attract house flies, thereby increasing the risk of food crop contamination. House fly attraction to honeydew-contaminated plant material was evaluated using a laboratory bioassay. House flies were attracted to the following plant-pest-honeydew combinations: citrus mealybug on squash fruit, pea aphid on faba bean plants, whitefly on navel orange and grapefruit leaves, and combined citrus mealybug and cottony cushion scale on mandarin orange leaves. House flies were not attracted to field-collected samples of lerp psyllids on eucalyptus plants or aphids on crepe myrtle leaves. Fungi associated with field-collected honeydews were isolated and identified for further study as possible emitters of volatiles attractive to house flies. Two fungal species, Aureobasidium pullulans and Cladosporium cladosporioides, were repeatedly isolated from field-collected honeydew samples. Both fungal species were grown in potato dextrose enrichment broth and house fly attraction to volatiles from these fungal cultures was evaluated. House flies were attracted to odors from A. pullulans cultures but not to those of C. cladosporioides. Identification of specific honeydew odors that are attractive to house flies could be valuable for the development of improved house fly baits for management of this pest species.     

Schistosoma mansoni: The attrition of a challenge infection in mice immunized with highly irradiated live cercariae

Mice immunized percutaneously with 400 Schistosoma mansoni cercariae given 20 kR of ⁶⁰Co irradiation were shown to develop an immunity in which nearly 80% of the parasites that would be expected to survive in control mice were killed. The major attrition of parasites was shown to occur within the first 4 days after challenge. Marked differences in the number of parasites which were recovered from the skin of immune mice and the failure of the majority of parasites to reach the lungs of immune mice indicated that the major site of attrition was in the skin. A further trickle of parasite deaths was evident beyond Day 5, but after Day 14 no further attrition of parasites appeared to occur. Mice immunized in the abdominal skin demonstrated similar levels of immunity whether challenged in the abdominal skin or in the ear. Immunization intramuscularly with irradiated schistosomula induced a much lower level of resistance and the marked parasite attrition in the skin at Day 2 was absent. Immunization with only 50 irradiated cercariae was shown to induce a level of skin immunity equivalent to that seen with 400 irradiated cercariae. The majority of cercariae given 20 kR of ⁶⁰Co irradiation remained in the skin; approximately 2% only reached the lungs. These studies demonstrate that percutaneous immunization of mice with highly irradiated cercariae induced a strong immunity which was largely effective in the skin. This immunity differed from that developed by chronically infected mice where the major attrition of parasites occurs after the lung phase of migration. The results also suggest that the penetration or persistence in the skin of live attenuated schistosomula may play a crucial role in the induction of a high level of skin immunity.     

The effect of lampit on Trypanosoma cruzi in mice organs and in the bloodstream.

Mice infected with bloodstream forms of Trypanosoma cruzi were treated with an active Nitrofuran compound (Nifurtimox, Lampit). Determination of the number of intracellular forms of T. cruzi in the liver and the spleen of control and Lampit-treated mice showed that the drug induced a decrease in the number of parasites inside the cells. A decrease in the number of bloodstream forms was also observed. Ultrastructural observations showed that Lampit induces several alterations in T. cruzi, the most characteristic alteration being the appearance of dense masses localized in the mitochondrial matrix of the parasites.     

Trypanosoma rhodesiense: protection in mice by inoculations of homologous parasite products

Mice were immunized against Trypanosoma rhodesiense (Wellcome strain) with whole lyophilized trypanosomes, with antigens produced by disrupting lyophilized trypanosomes under pressure, and with excretions and secretions of the living parasites. The survival rate in groups of 40 mice inoculated with disrupted trypansomes and challenged with the homologous strain was 48% with a soluble fraction, and 70% with a particulate fraction of the parasites. There was 95% survival after challenge in a group immunized with lyophilized trypanosomes; none of the controls survived. Results were essentially the same whether or not an aluminum hydroxide adjuvant was used. In subsequent experiments, complete protection was obtained with either crude excretion-secretion (ES) antigens or the particulate fraction of the ES antigen, while 40% of the mice survived challenge after inoculations of ES supernatant fluid. Mice immunized with crude ES antigen failed to survive challenge with a heterologous strain, although their mean survival time was prolonged several days beyond that of the controls.     

Effects of Shiny Cowbird Molothrus bonariensis parasitism on different components of House Wren Troglodytes aedon reproductive success

Avian brood parasites, including cuckoos and cowbirds, have multiple negative effects on their hosts. We analysed the effects of Shiny Cowbird Molothrus bonariensis parasitism on different components (e.g. egg losses, hatching success, chick survival and nest abandonment) of House Wren Troglodytes aedon reproductive success. We also conducted an experiment to discriminate between two mechanisms that may reduce hatching success in parasitized clutches: lower efficiency of incubation due to the increase in clutch volume and disruption of host incubation by the early hatching of Cowbirds. Egg puncturing by Shiny Cowbirds reduced host clutch size at hatching by 10–20%, and parasitized nests had a decrease in hatching success of 40–80%. Egg losses and hatching failures were positively associated with the intensity of parasitism. Brood reduction was greater in parasitized nests, but the growth rate of the chicks that fledged was similar to that in unparasitized nests. The combined effects of egg losses, hatching failures and brood reduction decreased the number of fledged chicks by 80%. In addition, egg puncturing increased the likelihood of nest abandonment by Wrens. Experimental data showed that hatching failures occurred when there was a combination of: (1) an increase in the volume of the clutch by the addition of the Cowbird egg without removal of host eggs, and (2) the addition of the Cowbird egg before the onset of incubation. This was relatively common in House Wren nests, as Cowbirds generally parasitize before the onset of incubation. Our results indicate that Shiny Cowbird parasitism imposes a major impact on House Wrens, as it affects all components of the Wren's reproductive success.     

Disruption of the Toxoplasma gondii bradyzoite-specific gene BAG1 decreases in vivo cyst formation

The bradyzoite stage of the Apicomplexan protozoan parasite Toxoplasma gondii plays a critical role in maintenance of latent infection. We reported previously the cloning of a bradyzoite-specific gene BAG1/hsp30 (previously referred to as BAG5) encoding a cytoplasmic antigen related to small heat shock proteins. We have now disrupted BAG1 in the T. gondii PLK strain by homologous recombination. H7, a cloned null mutant, and Y8, a control positive for both cat and BAG1, were chosen for further characterization. Immunofluorescence and Western blot analysis of bradyzoites with BAG1 antisera demonstrated expression of BAG1 in the Y8 and the PLK strain but no expression in H7. All three strains expressed a 116 kDa bradyzoite cyst wall antigen, a 29 kDa matrix antigen and the 65 kDa matrix reactive antigen MAG1. Mice inoculated with H7 parasites formed significantly fewer cysts than those inoculated with the Y8 and the PLK strains. H7 parasites were complemented with BAG1 using phleomycin selection. Cyst formation in vivo for the BAG1-complemented H7 parasites was similar to wild-type parasites. We therefore conclude that BAG1 is not essential for cyst formation, but facilitates formation of cysts in vivo.     

A SURVEY OF BLOOD PARASITES OF BIRDS IN THE MASCARENE ISLANDS, INDIAN OCEAN: WITH DESCRIPTIONS OF TWO NEW SPECIES AND TAXONOMIC DISCUSSION

A survey was carried out on the prevalence of blood parasites in birds in the Mascarene Islands. Smears from 357 birds of 25 species in 12 families were examined, of which 150 (42%) were found to harbour blood parasites. The most common parasites were Leucocytozoon ; a new species, L. zosteropis , is described from the Grey White-eye Zosterops borbonica mauritiana. This parasite was observed in smears from 68 birds of three species: Z. borbonica, Z. chloronothos and Z. olivacea. Other species of Leucocytozoon identified were L. fringillinarum from fodies, sparrows and a bulbul and L. marchouxi from two doves.
Haemoproteus was found only in domestic pigeons Columba livia and identified as H. columbae. Plasmodium relictum, P. vaughani and an unidentified species with elongate gametocytes were found in Zosterops , and Plasmodium sp. of low infection observed in other hosts. Trypanosoma mayae is redescribed from the House Sparrow Passer domesticus and the Mauritius Fody Foudia rubra , and considered to be a valid species. A new species of trypanosome, Trypanosoma phedinae , is described from the Malagasy Swallow Phedina b. borbonica. Other birds were found to harbour low infections of unidentified species of trypanosomes. A small number of birds were infected with Atoxoplasma , haemogregarines and Rickettsia-like organisms. An unidentified organism with a predilection for eosinophils was observed in several Mascarene Swiftlets Collocalia francica.
The results are discussed in relation to the possible effects of the parasites on the birds of the Mascarene Islands and comparisons made with the results of similar surveys on other Indian Ocean Islands.     

Malaria renders mice susceptible to mosquito feeding when gametocytes are most infective

Mice infected with Plasmodium berghei, P. chabaudi, or P. yoelii became lethargic and ceased to display normal antimosquito behavior. Periods of reduced defensiveness corresponded with maximum mosquito engorgement and with periods of maximum gametocyte infectivity to mosquitoes. Increased feeding success of mosquitoes during periods of peak gametocyte infectivity may be important to the natural maintenance of these malaria parasites.     

Attenuated Plasmodium yoelii lacking purine nucleoside phosphorylase confer protective immunity

Malaria continues to devastate sub-Saharan Africa owing to the emergence of drug resistance to established antimalarials and to the lack of an efficacious vaccine. Plasmodium species have a unique streamlined purine pathway in which the dual specificity enzyme purine nucleoside phosphorylase (PNP) functions in both purine recycling and purine salvage. To evaluate the importance of PNP in an in vivo model of malaria, we disrupted PyPNP, the gene encoding PNP in the lethal Plasmodium yoelii YM strain. P. yoelii parasites lacking PNP were attenuated and cleared in mice. Although able to form gametocytes, PNP-deficient parasites did not form oocysts in mosquito midguts and were not transmitted from mosquitoes to mice. Mice given PNP-deficient parasites were immune to subsequent challenge to a lethal inoculum of P. yoelii YM and to challenge from P. yoelii 17XNL, another strain. These in vivo studies with PNP-deficient parasites support purine salvage as a target for antimalarials. They also suggest a strategy for the development of attenuated nontransmissible metabolic mutants as blood-stage malaria vaccine strains.     

Kinetics of the growth of Toxoplasma gondii (RH strain) in mice.

A method is described for obtaining maximum yield of Toxoplasma tachyzoites from the peritoneal cavity of infected mice. Mice injected with 10² parasites contain more Toxoplasma in this site at the time of death than mice injected with larger numbers. The host does not mount a detectable humoral response to the parasite.     

Lung-phase immunity to Schistosoma mansoni. Flow cytometric analysis of macrophage activation states in vaccinated mice

A delayed-type hypersensitivity response has been postulated as the effector mechanism of lung-phase immunity to Schistosoma mansoni. We have sought evidence for this response by examining the state of alveolar macrophage activation in C57BL/6 mice vaccinated with radiation-attenuated cercariae, and challenged with normal parasites. As an index of activation, the capacity of macrophages to produce an oxidative burst upon stimulation with PMA, was measured at the single cell level by a flow cytometric method. Fourteen to 28 days after vaccination with 20-kr parasites, highly activated macrophages were recovered from the airways by bronchoalveolar lavage. Their probable role in resistance is to recruit T lymphocytes and macrophages to "arm" the lungs against subsequent challenge. The level of macrophage activation had declined to near background by the time challenge parasites arrived, although pulmonary leucocyte numbers remained elevated. Activated alveolar macrophages were not detected after vaccination with 80-kr parasites, which fail to reach the lungs or induce resistance. Challenge parasites, arriving in the lungs of 20-kr vaccinated mice, stimulated a rapid increase in the activation state of recruited macrophages, coincident with their retention in the pulmonary vasculature. These events occurred later in challenge control mice, with peak activation at day 21, when migration of parasites to the liver is complete. Mice vaccinated with 80-kr parasites lacked the accelerated response to challenge, behaving like the control group. The absence of activated peritoneal macrophages suggests a response restricted to organs such as the lungs, through which both vaccinating and challenge parasites migrate. We suggest that the role of activated alveolar macrophages in lung-phase immunity is to initiate and maintain the focal inflammatory responses which block onward migration of parasites and lead to their demise.     

Control of invasive predators improves breeding success of an endangered alpine passerine

Birds living in alpine environments are becoming increasingly impacted by human‐induced threats. We investigated the impacts of introduced mammalian predators on an endangered alpine species, the New Zealand Rockwren Xenicus gilviventris, and assessed whether predator control improved its breeding success. Nest monitoring revealed that the primary cause of nest failure was predation by invasive mammals, primarily Stoats Mustela erminea and House Mice Mus musculus. Daily survival rates (DSR) decreased with nest age, and nests were at their most vulnerable to predators just prior to fledging. DSR, egg‐hatching and fledgling rates were all improved by predator trapping, demonstrating the significant impacts that even low numbers of invasive predators can have on sensitive alpine and upland species.     

Low and high-dose intradermal infection with Leishmania major and Leishmania amazonensis in C57BL/6 mice

A model of skin infection with Leishmania amazonensis with low doses of parasites is compared to infection with high doses of L. amazonensis and low and high doses of Leishmania major. C57BL/6 mice were infected with 103 or 10(6) parasites in the ear and the outcome of infection was assessed. The appearance of lesions in mice infected with 103 parasites was delayed compared to mice infected with 10(6) Leishmania and parasites were detectable at the infection site before lesions became apparent. Mice infected with L. amazonensis displayed persistent lesions, whereas infection with L. major spontaneously healed in all groups, although lymphocytes persisted at the site of infection after healing. Macrophages persisted only in L. amazonensis-infected mice. High-dose L. amazonensis-infected mice produced lower levels of IFN-γ and TNF than mice infected with L. major. No correlation between the persistence of parasites and IL-10 levels and the production of nitric oxide or urea by macrophages was found. We conclude that infection with low doses of L. amazonensis in the dermis changes the course of infection by delaying the appearance of lesions. However, low-dose infection does not change the outcomes of susceptibility and cytokine production described for subcutaneous infection with high numbers of parasites.     

Treatment of experimental visceral leishmaniasis with lymphokine encapsulated in liposomes

Highly susceptible mice were infected with Leishmania donovani chagasi and were treated with supernatants, free or encapsulated in liposomes, from concanavalin A-stimulated or unstimulated mouse spleen cell cultures. Treatment consisted of multiple i.v. injections beginning 2 days before to 2 days after infection. Mice treated with lymphokine-rich supernatants encapsulated in liposomes had significantly fewer liver parasites than the control groups, demonstrating in vivo activity of lymphokine against an infectious organism.     

Predation on native birds in New Zealand beech forests: the role of functional relationships between Stoats Mustela erminea and rodents

In the Holarctic, predation by mustelids on birds is often linked to population cycles of rodents (especially voles and lemmings) because birds may be buffered against mustelid predation at high rodent densities. By contrast, interguild relationships between introduced mustelids and rodents can have very different consequences for native birds in ecosystems where mustelids have been introduced. Here, we consider the interactions between Stoats Mustela erminea , feral House Mice Mus musculus and native birds in New Zealand beech Nothofagus spp. forests. We conclude that buffering to protect birds from Stoat predation normally fails in these systems, because peak populations of mice in these forests are low by Holarctic standards, and mice usually do not become sufficiently abundant to distract increased numbers of Stoats from preying on birds. However, temporary buffering is possible during rare episodes of extreme mouse abundance.     

A Review of: “Methods of Protein Separation,N. Catsirapoolas,ed. Plenum Press,New York, 1975; 281 pages; hardbound; $27.50”

Tryporaastogotes of three strains of Trypanosoma cruzi were isolated from the blood of infected mice employing lymphoprep for separation of the red blood cells and a column of DEAE cellulose for removal of white cells and platelets. An average recovery of 45 to 5 8 percent of actively motile, infective organisms, free of contaminating blood cells was obtained. Protein and carbohydrate assays of the separated organisms revealed significant differences between the Tulahuen, a reticulotropic strain, and the House 510 and House 11, two myotropic strains of this parasitic species. The present procedure should provide sufficient parasites for physiological and biochemical studies; it has also served to indicate particular strain characteristics which may aid in a taxonomic classification of these organisms.     

Trypanosoma cruzi: interaction with vertebrate cells in vitro. 3. Selection for biological characteristics following intracellular passage

Two strains of Trypanosoma cruzi, House 510 and Limbo Tree Platform, were studied to determine whether maintenance in vertebrate cell culture would alter their biological characteristics. After having been maintained for several years in alternate mouse-insect passage using NIH general purpose male white mice and Rhodnius prolixus, respectively, the parasites were transferred into primary bovine embryo skeletal muscle cell culture and their intracellular doubling time and generation number quantified.A significant change appeared in the doubling time of each strain. Initially, the doubling times of the House 510 and Limbo Tree Platform strains were not significantly different. They were 8.6 ± 0.8 hr and 7.5 ± 0.5 hr, respectively. After a varying period in cell culture, these values changed to 11.4 ± 1.6 and 11.5 ± 1.3 hr, respectively. Other observations, unrelated to length of time in cell culture, included the appearance of many broad, trypomastigote forms with a decreased ability to reach host cells and a varying generation number ranging from 7 to 9.