Age-dependent resistance to Cryptosporidium muris (strain MCR) infection in golden hamsters and mice

An age-dependent aspect of resistance to Cryptosporidium muris (strain MCR) infection was monitored in Syrian golden hamsters, Mesocricetus auratus, at 1-, 5- and 10-week of age and in ICR mice. Mus musculus, at 3-, 12-, and 15-week of age orally inoculated with a single dose of 2 x 10(6) oocysts, respectively. The prepatent periods for both animals were similar, independent of age, but the patency was significantly longer in younger hamsters (P < 0.001) and a long tendency in younger mice. Hamsters infected at 1-week of age excreted about 10 times higher oocysts than those at 5- and 10-week of age. However, the total oocyst output was similar among mice of different ages. There was a good correlation between the length of the patency and the total oocyst output in hamsters (R = 0.9646), but not in mice (R = 0.4561). The immunogenicity of the parasite to homologous challenge infections was very strong in hamsters and relatively strong in mice. These results indicate that acquired resistance to C. muris infection is age-related and the innate resistance is independent of age of hamsters, and that both innate and acquired resistance, on the contrary, are irrespective of age of mice.     

Dietary, bacterial, and host genetic interactions in the pathogenesis of transmissible murine colonic hyperplasia

Transmissible murine colonic hyperplasia, cuased by a variant of Citrobacter freundii (4280). was shown to be modified by diet and by host strain and species. Four different diets fed to mice inoculated with C frundii 4280 were found to have a significant but varying influence on the severity of hyperplasia. Diet also influenced the colonic crypt height of uninoculated, control mice. F344 rats, Syrian hamsters, and NIH Swiss [N:(S)], C57BL/6J, C3H/HeJ, and DBA/2J mice were inoculated with C freundii 4280. Marked strain differences were noted in the mice in mortality and severity of the colonic hyperplasia. The NIH Swiss mice had the greatest and the C57BL/6J mice had the least mucosal hyperplasia. The rats and hamsters did not develop disease or maintain infection after inoculation with the organism. Twenty isolates of Citrobacter from a range of biologic sources were inoculated into susceptible mice, but only mice inoculated with C freundii 4280 developed the disease.     

Mouse polyclonal and monoclonal antibody to scrapie-associated fibril proteins.

Antibody response in mice to scrapie-associated fibril proteins (protease-resistant proteins [PrPs]) was generated to different epitopes depending on the source of antigen. Mice responded differently to PrPs isolated from scrapie-infected animals of homologous (mouse) versus heterologous (hamster) species. An enzyme-linked immunosorbent assay established to monitor this antibody response in mice immunized with PrPs was unable to detect such a response in scrapie-infected mice. A monoclonal antibody (MAb), 263K 3F4, derived from a mouse immunized with hamster 263K PrPs reacted with hamster but not mouse PrPs. MAb 263K 3F4 also recognized normal host protein of 33 to 35 kilodaltons in brain tissue from hamsters and humans but not from bovine, mouse, rat, sheep, or rabbit brains. This is the first demonstration of epitope differences on this host protein in different species. The defining of various epitopes on PrP through the use of MAbs will lead to a better understanding of the relationship of PrPs to their host precursor protein and to the infectious scrapie agent.     

Intestinal parasites of conventionally maintained BALB/c mice and Mastomys coucha and the effects of a concomitant schistosome infection

A longitudinal study was carried out to identify the spectrum of intestinal parasites present in conventionally maintained BALB/c mice and Mastomys coucha and to determine the effects of concomitant schistosome infections on their parasite status. Six parasites were observed during the course of the study, namely the nematodes Aspiculuris tetraptera and Syphacia obvelata, Entamoeba muris and the flagellates Trichomonas muris, Spironucleus muris and Chilomastix spp. Although the 2 rodents shared common facilities, the overall prevalences of S. obvelata, T. muris and S. muris were significantly higher in M. coucha than BALB/c mice. BALB/c mice with concomitant schistosome infection had increased prevalences of E. muris, T. muris and S. muris. In M. coucha, in contrast, there were no significant increases in parasite prevalences. Infection intensities of T. muris and S. muris were significantly greater in M. coucha than BALB/c mice. Concomitant schistosome infection resulted in increased intensities of T. muris infection in BALB/c mice only. The influence of immune status in determining the susceptibilities of rodents to environmentally transmitted parasites is discussed.     

Evidence that autoimmunity in NZB mice is caused by a defect in immune specificity rather than a generalized defect in tolerance of self-antigens

NZB mice which were already producing anti-erythrocyte autoantibodies were not able to respond to their own liver F antigen, thus providing evidence that their autoimmunity is not caused by a generalized breakdown in self-tolerance mechanisms. The specificity of autoantibodies produced in the spontaneous hemolytic anemia was different from that of antierythrocyte antibodies induced in normal mice and in young NZB mice by injections of rat erythrocytes. This indicates that the B-cell clones which can be triggered by heterologous antigen are different from those responsible for the NZB disease; the latter clones may not exist in normal mice.     

Immunological surveillance against DNA-virus-transformed cells: correlations between natural killer cell cytolytic competence and tumor susceptibility of athymic rodents.

Adenovirus type 2 (Ad2)-transformed hamster and rat cells are susceptible to lysis by natural killer (NK) cells from the host of origin and are nontumorigenic in immunocompetent hamsters and rats, respectively. These NK-cell-susceptible, virus-transformed cells are, however, highly tumorigenic in athymic (nude) mice--animals with intact NK-cell responses. In vitro lysis of these xenogeneic, Ad2-transformed cells by nude-mouse NK cells was found to be defective. In contrast, Ad2-transformed hamster and rat cells were highly susceptible to lysis by nude-rat NK cells. Furthermore, xenogeneic, Ad2-transformed hamster cells were nontumorigenic in nude rats unless the NK-cell responses of the challenged animals were compromised. The results of the nude-rat studies show that thymus-dependent, cytotoxic T-lymphocyte-mediated, host cellular immune responses are not essential for rejection of xenogeneic cells transformed by nononcogenic Ad2. The data suggest instead that immunologically nonspecific host cellular immune responses, such as those mediated by NK cells, are sufficient for rejection of Ad2-transformed cells. These results indicate that biologically important differences exist in the NK-cell-mediated defenses mounted by nude mice and nude rats against transformed cells that may account for the different patterns of tumor induction by various neoplastic cell types in these athymic animals.     

Separation of antigens from Sarcocystis species using chromatofocusing

Crude antigen preparations from bradyzoites of Sarcocystis species exhibit a high degree of cross-reactivity with antisera against heterologous Sarcocystis species, preventing the development of a species-specific immunological test for sarcocystiosis. In this study, we fractionated bradyzoite-derived protein extracts from Sarcocystis tenella, Sarcocystis arieticanis, Sarcocystis gigantea, and Sarcocystis muris by chromatofocusing and obtained distinct protein elution profiles for each species. We then examined the isolated protein fractions for antigenicity with homologous and heterologous reference sera in an enzyme-linked immunosorbent assay. Whereas some antigenic fractions of bradyzoite proteins had equally high reactivity with the homologous and heterologous sera, the reactivity of other fractions was 3-38 times higher with homologous serum than with heterologous sera. Mice immunized with less cross-reactive protein fractions of S. gigantea and S. muris bradyzoites produced a specific immune serum. Thus, it is possible to isolate species-specific antigens from crude mixtures of bradyzoite-derived Sarcocystis antigens for development of species-specific immunological tests for sarcocystiosis.     

Evaluation of heterologous ARS activity in S. cerevisiae using cloned DNA from S. pombe.

Cloned segments of Schizosaccharomyces pombe genomic DNA were screened for ARS activity in the native host, S. pombe, using high frequency transformation, phenotypic instability and extrachromosomal maintenance of unrearranged plasmid sequences as criteria for ARS function. This analysis revealed 12 ARS elements in a total of 230 kb of chromosomal DNA, indicating an average frequency of one ARS every 19 kb of genomic DNA. We then used these clones to assess the reliability of the S. cerevisiae assay for detecting ARS elements in heterologous DNA. The results show that not only does the S. cerevisiae assay fail to detect a large proportion of true ARS elements but it also wrongly identifies a significant proportion of clones which did not display ARS activity in the native host. We would therefore recommend restraint when extrapolating from observed ARS function of heterologous DNA in S. cerevisiae to a presumed analogous role in the original host.     

The structure of the surface apparatus in sarcocysts of Sarcosporidia in the persistence process

The structure of the sarcocyst surface apparatus (SSA) was investigated for two sarcosporidian species: Sarcocystis muris (non-pathogenic) and S. fusiformis (pathogenic). The surface membrane, being the main SSA subsystem, makes numerous vesicle-like protrusions with different ultrastructural patterns. This made it possible to distinguish between four and three types of these protrusions in S. fusiformis and S. muris, respectively. Vesicles of similar structure, pinched off from the fully formed protrusions, were classified, correspondingly, in the same four and three different types. A presumable functional role of both protrusions and membrane-coated vesicles in pathogenicity of different sarcosporidian species is proposed. The vesicles pinched off from corresponding protrusions may be involved in transporting certain substance complexes from the sarcocyst to the harbouring host cell. In addition, another way of substance transporting was observed, when the cystic substances, not surrounded with any membrane coating, are thrown from open protrusions directly into the immediate cytoplasm of the host cell.     

Effect of developing Sarcocystis muris tissue cysts on ultrastructural change of murine muscle fibers

A study was made of the influence exerted by developing sarcocysts of Sarcocystis muris on the ultrastructural organization of muscle fibres, both harbouring the sarcocysts (HSM) and sarcocyst-free (SFM), from skeletal muscles of experimentally infected mice. Muscle fibres of non-infected mice of the same age served as a control. Mice were sacrificed 6 months following feeding S. muris oocysts (or sporocysts). The developing sarcocysts seriously destroyed HSM: their myofilaments were no hold in register, cross-bridges almost entirely disappeared, M-lines and Z-disks looked as broken structures. The majority of actin myofilaments were arranged along myosin myofilaments as discrete units. The host cell sarcoplasm was packed with numerous vacuoles of different form and size. Compared to muscle fibres in the control, SFM of infected mice also displayed an obvious ultrastructural alteration. On the periphery of SFM, some destroyed sarcomeres with swollen myofilaments were noticed whose cross-bridges were totally lacking. In other extreme areas myosin and actin myofilaments were disintegrated into thin straightened filaments 2.0-2.5 nm in diameter. It is supposed that HSM and SFM of the infected mice may experience different kinds of influence on the part of the developing intracellular parasite (sarcocyst). And it dos not seem unlikely that various biologically active substances, produced by the parasite, may be vesicle transported to SFN through the endomysium space.     

The characterization of intraepithelial lymphocytes, lamina propria leukocytes, and isolated lymphoid follicles in the large intestine of mice infected with the intestinal nematode parasite Trichuris muris

Despite a growing understanding of the role of cytokines in immunity to the parasitic helminth Trichuris muris, the local effector mechanism culminating in the expulsion of worms from the large intestine is not known. We used flow cytometry and immunohistochemistry to characterize the phenotype of large intestinal intraepithelial lymphocytes (IEL) and lamina propria leukocytes (LPL) from resistant and susceptible strains of mouse infected with T. muris. Leukocytes accumulated in the epithelium and lamina propria after infection, revealing marked differences between the different strains of mouse. In resistant mice, which mount a Th2 response, the number of infiltrating CD4+, CD8+, B220+, and F4/80+ IEL and LPL was generally highest around the time of worm expulsion from the gut, at which point the inflammation was dominated by CD4+ IEL and F4/80+ LPL. In contrast, in susceptible mice, which mount a Th1 response, the number of IEL and LPL increased more gradually and was highest after a chronic infection had developed. At this point, CD8+ IEL and F4/80+ LPL were predominant. Therefore, this study reveals the local immune responses underlying the expulsion of worms or the persistence of a chronic infection in resistant and susceptible strains of mouse, respectively. In addition, for the first time, we illustrate isolated lymphoid follicles in the large intestine, consisting of B cells interspersed with CD4+ T cells and having a central zone of rapidly proliferating cells. Furthermore, we demonstrate the organogenesis of these structures in response to T. muris infection.     

Infection status of dragonflies with Plagiorchis muris metacercariae in Korea.

Plagiorchis muris has been found in both house and field rats as well as in humans. The infection status of the second intermediate hosts of P. muris is prerequisite in understanding their biological features in an ecosystem. Six species of dragonflies were caught in a wide range of areas in Korea; and they were Sympetrum darwinianum, S. eroticum, S. pedomontanum, S. infuscatum, Pantala flavoscens, Calopteryx atrata, and Orthetrum albistylum speciosum. The occurrence of P. muris metacercariae in dragonflies was nationwide with various infection rates. The metacercarial burden of P. muris in the surveyed areas was the highest in S. eroticum followed by S. darwinianum, S. pedomontanum, and C. atrata. The highest infection rate by P. muris metacercariae was found in S. darwinianum followed by S. eroticum. The metacercarial burden was particularly heavy in the dragonflies found in Hamyang-gun and Kosong-gun, Kyongsangnam-do. It is, therefore, likely that dragonflies play a significant role as the second intermediate host in the life cycle of P. muris in Korea.     

Microbiological contamination of laboratory mice and rats in Korea from 1999 to 2003.

To survey the microbiological contamination of laboratory mice and rats in Korea during a 5-year period, we monitored animals housed in mouse and rat facilities with either barrier or conventional systems. At barrier and conventional mouse facilities, the most important pathogen identified was mouse hepatitis virus (MHV), while Mycoplasma pulmonis was the most important pathogen at conventional rat facilities. Interestingly, hantavirus was recovered from both barrier and conventional mouse facilities. The most common protozoon identified was Tritrichomonas muris in mouse facilities and Entamoeba muris in rat facilities. In addition, we found that the microbiological contamination of mice and rats in conventional facilities was severe. These results suggest that conventional facilities should be renovated and monitored regularly to decrease microbiological contamination. We also propose that hantavirus should be monitored in Korea as an important mouse pathogen.     

The ferret (Putorius putorius furo), an additional final host of Sarcocystis muris (author's transl)]

Two ferrets were fed mice experimentally infected with Sarcocystis muris. After 7 days they excreted with their faeces for 9 days sporocysts which were morphologically indistinguishable from S. muris sporocysts. Five mice which each received 70 of these sporocysts orally developed macroscopically visible cysts of S. muris in their musculature after 4 months.     

The growth of the metacestodes of Taenia crassiceps in white mice.

The effect of the sex of the intermediate host on the growth and development of the metacestodes of Taenia crassiceps has been investigated. Three different strains of mice were used, the C R S, L A C A and C F L P strains and two strains of metacestode, the Toi and the E R S strains. The results show that matacestodes of T. crassiceps grow and multiply more rapidly in female than in male mice, although both sexes are equally susceptible to the infection. The origin of the parasite, i.e., from a rat or mouse host, affects the parasite growth.     

Isolation and identification of Cryptosporidium from various animals in Korea. II. Identification of Cryptosporidium muris from mice

Each of SPF mice(Scl: ICR strain, 3-week-old males) was inoculated with 5 x 10(4) oocysts of Cryptosporidium by stomach tube. The oocysts were large type one which was previously isolated from Korean mice, and passaged in 3-week-old SPF mice. The patterns of oocyst discharge were monitored daily, and in order to observe the ultrastructure of developmental stages the stomach of the mice was examined by transmission electron microscopy (TEM) at 4 weeks post-inoculation. The prepatent period for 6 mice was 5.6 days post-inoculation on the average, and the patent period was 63.2 days. The number of oocysts discharged per day from the mice reached peak on day 36.6 post-inoculation on the average. A large number of oocysts were found in fecal samples obtained from inoculated mice on days 30-50 post-inoculation. C. muris was larger than C. parvum at almost every developmental stages, the size difference being 1.4 times in oocysts, 2.4 times in sporozoites, 1.6 times in merozoites, and 1.5 times in microgametes. The ultrastructural features of the attachment site of C. muris to the mucus cells were remarkably different from those of C. parvum and its closely related species. The anterior projection of the protozoa (C. muris), the outer aspect of which was surrounded by a thick filamentous process of the host cell, has not been reported at any developmental stages of C. parvum or its closely related species. The size of the oocysts of strain RN 66 was larger than that of Korean mice origin. The above results reveal that the large type Cryptosporidium of Korean mice origin is identified as Cryptosporidium muris and this type was named as C. muris (strain MCR).     

Occurrence and treatment of the mange mite Notoedres muris in marsh rats from South America

The mange mite Notoedres muris is reported from a new host, the marsh rat (Holochilus brasiliensis) from Argentina. The infection involved alopecia and encrustations on the ears and face, and was treated successfully by a subcutaneous injection of ivermectin. The new record suggests that Notoedres muris has become self-maintaining within this marsh rat population.