Toxoplasma gondii: differential protection rates by two strains against cyst formation in a rat model

A previous infection with the ME-49 strain of Toxoplasma gondii (of low pathogenicity for mice), protected 17 of 20 rats against formation of brain cysts, following challenge with 10(3) oocysts of the high pathogenicity M3 strain, as determined by bioassay of rat brains in mice. The low pathogenic KSU strain did not afford comparable protection. Protection was further tested in rats that were orally or subcutaneously immunized with cysts or oocysts of the ME-49 strain, and later challenged with 2 x 10(2) cysts or 10(2) oocysts of the highly pathogenic strains M3, M-7741 and C. Protection ranged from 43 to 100%, compared to non immunized control rats and was independent of the stage of ME-49 strain and of the routes used to immunize the rats. The results obtained encourage further investigation into prevention of toxoplasmosis in humans and food animals.     

Virulence of Venezuelan Equine Encephalomyelitis Virus Subtypes for Various Laboratory Hosts

Mice, guinea pigs, and duck embryo cell cultures were inoculated with known subtypes of Venezuelan equine encephalomyelitis (VEE) virus and the attenuated (TC-83) strain of VEE. With the exception of TC-83, all strains were highly pathogenic for suckling mice by either intracranial or intraperitoneal routes of inoculation used. Virulence for older mice and guinea pigs provided a means to distinguish strains. In addition, virulence or lack of virulence for adult mice or guinea pigs provides a rapid method for separating epizootic subtype IB from TC-83 VEE virus isolates.     

Pathogenicity of Nocardia caviae,N. asteroides and N. brasiliensis

The pathogenicity ofNocardia caviae, N. asteroides andN. brasiliensis has been tested for white mice, guinea pigs and rabbits and chorio-allantoic membrane of the developing chick embryo. Altogether, 14 strains belonging to the 3Nocardia species originating from soil, human and animal sources in India or abroad were tested. All of them proved pathogenic though the degree of virulence varied from strain to strain. Incorporation of hog gastric mucin in the inoculum enhanced the virulence of all the 3Nocardia species for white mice.N. caviae strains were uniformly more virulent than those ofN. asteroides andN. brasiliensis.In the white mice inoculated intraperitoneally, a greater dissemination of the disease was apparent withN. caviae than withN. asteroides. Of the 6 strains ofN. caviae tested, 5 disseminated to the lung, 3 to the heart and 2 to the brain. InN. asteroides dissemination of the disease to the brain was observed with 2 of its 3 strains.N. brasiliensis showed no dissemination.N. caviae was found to be equally virulent for white mice, guinea pigs and rabbits. On the other hand,N. asteroides andN. brasiliensis were more virulent for white mice than for guinea pigs and rabbits. The lesions caused byN. caviae in mice, guinea pigs and rabbits persisted up to 4 weeks. In strong contrast to this the lesions due toN. asteroides andN. brasiliensis found in the guinea pigs and rabbits showed a strong tendency towards spontaneous clearance.Histologically, the lesions caused byN. caviae, N. asteroides andN. brasiliensis in mice, guinea pigs and rabbits were in the form of abscesses which showed an acute or chronic reaction. In the case ofN. caviae these abscesses showed both granules and freely dispersed cocco-bacillary bodies or filaments. As forN. asteroides it occurred in the form of cocco-bacillary bodies or filaments whereasN. brasiliensis consistently produced granules in the lesions.The lesions caused by the 3Nocardia species on the chorio-allantoic membrane of the developing chick embryo were in the form of abscesses which contained cocco-bacillary bodies and branching filaments but no granules.This forms a part of the thesis submitted by P.V.K. for Ph. D. degree, of the University of Delhi.     

Attempts to establish experimental Cyclospora cayetanensis infection in laboratory animals

Attempts were made to develop an animal model for Cyclospora cayetanensis to identify a practical laboratory host for studying human cyclosporiasis. Oocysts collected from stool of infected humans in the United States, Haiti, Guatemala, Peru, and Nepal were held in potassium dichromate solution to allow development of sporozoites. The following animal types were inoculated: 9 strains of mice, including adult and neonatal immunocompetent and immune-deficient inbred and outbred strains, rats, sandrats, chickens, ducks, rabbits, jirds, hamsters, ferrets, pigs, dogs, owl monkeys, rhesus monkeys, and cynomolgus monkeys. Most animals were inoculated by gavage, although some of the primates were fed oocysts on food items. The animals were examined for signs of infection, particularly diarrhea, and stool samples were examined for 4-6 wk after inoculation. None of the animals developed patent infections or signs of infection. We conclude that none of the animals tested is susceptible to infection with C. cayetanensis.     

Toxoplasma gondii: protection against colonization of the brain and muscles in a rat model

The objective was to test immune protection against the formation of Toxoplasma gondii tissue cysts in rats. It has been previously shown that 50 T. gondii tissue cysts of strain Me49 are not pathogenic for CF-1 mice, whereas 1 T. gondii tissue cyst of strain M-7741, can be lethal for mice 11-13 days after subcutaneous or oral administration. In the present study, ten rats were fed T. gondii oocysts of strain Me49 and after a further 30 days they were each orally challenged with T. gondii oocysts of strain M-7741. Thirty days after this, they were euthanased and brain and muscle samples inoculated subcutaneously or orally dosed, respectively, to mice for bioassay. None of the mice died, whereas all the mice that were inoculated with brain homogenates or were fed muscle samples from four non-immunized rats that had been inoculated with T. gondii oocysts of strain M-7741, died. These results encourage further research towards achieving vaccinal protection against the formation of T. gondii tissue cysts in meat animals and people.     

Characterization of Bacillus anthracis strains used for vaccination

Three Bacillus anthracis strains, formerly used as anti-anthrax vaccine strains in Argentina, were characterized from genetic and pathogenic perspectives. Southern blotting and PCR with pXO1 and pXO2 probes and primers, as well as pathogenicity and protection tests in guinea pigs and mice, were performed. Two of the B. anthracis strains contained both pXO1 and pXO2 plasmids, as did the fully virulent strains, while the third was a Sterne-type strain (pXO1+, pXO2-). The three strains were, however, markedly less pathogenic than a wild-type virulent strain. The methodology applied here may be used to characterize other B. anthracis strains.     

Saprophytic occurrence of Trichophyton mentagrophytes and Microsporum gypseum in the coats of healthy laboratory animals

A group of 199 healthy laboratory animals, comprising 63 guinea pigs; 58 white mice. 47 rats and 31 rabbits, was sampled for the presence of pathogenic dermatophytes. T. mentagrophytes, var. granulare, was isolated in 10% (5-guinea pigs, 6 mice, 6 rats and 2 rabbits) and M. gypseum was found in 7 animals (3 guinea pigs, 3 mice and one rat). No ringworm lesions were observed in the respective animals. This is the first report on such findings in Israel.     

Experimental Toxoplasma gondii infection in grey seals (Halichoerus grypus)

Laboratory-reared animals were used to assess the susceptibility of seals (Halichoerus grypus) to Toxoplasma gondii infection. Four seals were each orally inoculated with 100 or 10,000 oocysts of T. gondii (VEG strain), and another 4 seals served as negative controls. Occasionally, mild behavioral changes were observed in all inoculated seals but not in control animals. A modified agglutination test revealed the presence of antibodies to T. gondii in sera collected from inoculated seals and mice inoculated as controls. No evidence of the parasite was found on an extensive histological examination of seal tissues, and immunohistochemical staining of tissue sections from inoculated seals revealed a single tissue cyst in only 1 seal. Control mice inoculated with 10 oocysts from the same inoculum given to seals became serologically and histologically positive for T. gondii. Cats that were fed brain or muscle tissue collected from inoculated seals passed T. gondii oocysts in feces. This study demonstrates that T. gondii oocysts can establish viable infection in seals and supports the hypothesis that toxoplasmosis in marine mammals can be acquired from oocysts in surface water runoff and sewer discharge.     

Genetic mapping of lymphocytic choriomeningitis virus pathogenicity: virulence in guinea pigs is associated with the L RNA segment.

The Armstrong CA 1371 (ARM) and WE strains of lymphocytic choriomeningitis virus (LCMV) differ in the ability to produce disease in adult guinea pigs. Infection with the ARM strain is not lethal, even at high virus doses (greater than 10,000 PFU), whereas the WE strain causes 100% mortality even at low doses (less than 10 PFU). To determine the genetic basis of this virulence, intertypic reassortants were made between the ARM and WE strains of LCMV. The two reassortants with the genotypes WE/ARM (L segment of WE and S segment of ARM) and ARM/WE (L segment of ARM and S segment of WE) were tested for their pathogenicity in guinea pigs. The ARM/WE reassortant was avirulent like the ARM/ARM parental strain. Minimal viral replication was observed in organs of guinea pigs inoculated with 10(2) or 10(5) PFU of ARM/ARM or ARM/WE, and all animals survived. In contrast, the WE/ARM reassortant was highly virulent like the WE/WE parental strain and killed all of the infected animals. High levels of viral replication were observed in guinea pigs infected with the latter two strains. In contrast to these in vivo observations, both the parental strains and the ARM/WE or WE/ARM reassortants had similar growth potential in cultured guinea pig fibroblasts. Thus, the L RNA segment of LCMV WE is important for viral replication in vivo and is associated with fatal acute disease after infection of adult guinea pigs.     

Susceptibility of experimental animals to reinfection with Clonorchis sinensis

The present study observed the resistance to reinfection with Clonorchis sinensis in various experimental animals including mice, guinea pigs, rabbits, and dogs, as well as rats and hamsters. The resistance rates to reinfection in rats, mice, hamsters, guinea pigs, rabbits, and dogs were 79.7%, 58.0%, -12.6%, 54.8%, 62.6%, and 6.0%, respectively. Worms recovered from reinfected rats and mice were immature, and significantly smaller than those from the primarily infected (P < 0.01), whereas those from other animals were fully matured to adults. These findings indicate that the protective response against reinfection with C. sinensis is prominent in rats and mice, and that they may be a good animal model to investigate the mechanism of resistance to reinfection with C. sinensis.     

Alveolar macrophages in pulmonary immune responses. I. Role in the initiation of primary immune responses and in the selective recruitment of T lymphocytes to the lung

Antigen inoculated intratracheally (IT) into animals can induce primary immune responses and selectively recruit specific T cells to the lung. In the current study, the role of alveolar macrophages (AM) in these two responses was investigated. Antigen-pulsed bronchoalveolar cells (BAC) inoculated IT into guinea pigs generated a population of immune T cells that proliferated in vitro on reexposure to antigen-pulsed macrophages (M?). The possibility that antigen-pulsed donor BAC shed antigen that was subsequently processed and presented by host M? was ruled out by genetic experiments. Thus, peritoneal exudate lymphocytes (PEL) from (2 X 13)F1 guinea pigs primed with antigen-pulsed BAC from strain 2 animals responded preferentially to antigen-pulsed strain 2 M? rather than to antigen-pulsed strain 13 M?. In a second set of studies, antigen-pulsed BAC inoculated IT into guinea pigs selectively recruited antigen-specific T cells to the lung. Genetic experiments verified that inoculated BAC were the source of the antigen-presenting cells responsible for selective recruitment. Thus, antigen-pulsed strain 2 BAC inoculated IT recruited a greater proportion of (2 X 13)F1 T cells that recognized antigen in the context of strain 2 M? than F1 T cells that recognized antigen on strain 13 M?. Taken together, these studies suggest that AM contribute to the regulation of pulmonary immunity by both inducing T lymphocyte immunity and selectively recruiting specific T cells to the lung.     

Biological properties of antibiotic-resistant mutants of the mildly pathogenic Rickettsia prowazekii E strain

The use of R. prowazekii strain E with low pathogenicity as live vaccine against exanthematous typhus is limited by its high specific reactogenicity, which is probably due to the reversion of the virulence of the strain. One of the approaches to the stabilization of the avirulent properties of strain E is obtaining its mutants with stable decreased pathogenic properties. The article presents the data on the infectious properties of R. prowazekii antibiotic-resistant strain E mutants obtained in earlier experiments, in respect of chick embryos and laboratory animals, as well as the capacity of this strain for producing immunity to challenge with R. prowazekii virulent strain in guinea pigs. The study has revealed that the erythromycin-resistant mutant of R. prowazekii strain E, induced by nitrosoguanidine (NG), has lower infective capacity for chick embryos, guinea pigs, cotton rats and white mice. The infective capacity of the NG-induced rifampicin-resistant and spontaneous erythromycin-resistant mutants of R. prowazekii strain E is similar to the infective capacity of the initial strain. The rifampicin-resistant and spontaneous erythromycin-resistant mutants of R. prowazekii strain E possess immunogenicity similar to that of the initial strain E, and the NG-induced erythromycin-resistant mutant possesses lower, but sufficiently pronounced immunogenicity despite its decreased infective capacity for guinea pigs.     

A comparative study on the biology of Cryptosporidium sp. from guinea pigs and Cryptosporidium parvum (Apicomplexa).

Cryptosporidium sp. from guinea pigs and C. parvum were compared morphologically, electrophoretically, and for the ability to infect suckling mice. Oocysts from guinea pigs measured 5.4 x 4.6 (4.8-5.6 x 4.0-5.0) microns and had a shape index (length/width) of 1.17 (1.04-1.33). Oocysts of C. parvum were similar and measured 5.2 x 4.6 (4.8-5.6 x 4.2-4.8) microns with a shape index of 1.16 (1.04-1.33). All suckling mice inoculated with oocysts of C. parvum became infected, whereas most, but not all, mice fed oocysts of the guinea pig isolate also became infected. However, mice inoculated with oocysts from guinea pigs produced on average 100-fold fewer oocysts by day 7 postinoculation than did mice infected with C. parvum, and the resulting infections were sparse and patchy along the ileum. Electrophoretic profiles were similar, but 125I surface labeling of outer oocyst wall proteins revealed striking differences between the two isolates. Cryptosporidium parvum had a wide molecular size range of 125I-labeled bands, whereas C. sp. from guinea pigs had a banding pattern clustered between 39 and 66 kDa, with a smaller number of bands greater than 100 kDa.     

Pathogenicity of alternaria alternata and its antibody production in experimental animals

To determine the potential pathogenicity ofAlternaria alternata, we exposed rabbits and guinea pigs to the organism by intradermal and intraperitoneal injection and by scarification. It caused superficial mycosis when inoculated by scarification. An antigenic extract of it that we prepared and used in ring precipitation tests demonstrated precipitating antibodies in the experimentally infected animals.     

Experimental transmission of Caryospora simplex (Apicomplexa: Eimeriidae) to Palestine vipers, Vipera xanthina palestinae (Serpentes: Viperidae)

Four littermate, laboratory-reared Palestine vipers, Vipera xanthina palestinae (#149, #150, #151, #152) (Serpentes: Viperidae) were used to determine modes by which Caryospora simplex (Apicomplexa: Eimeriidae) could be transmitted to snakes. Viper #149 was inoculated orally by stomach tube with 5.0 X 10(4) sporulated oocysts of C. simplex obtained from the feces of an Ottoman viper, V. x. xanthina and began passing unsporulated oocysts of C. simplex 121 days post-inoculation (DPI). Viper #150 was fed five mice that had been inoculated orally greater than or equal to 25 days previously with 5.0 X 10(4) sporulated oocysts of C. simplex and it began passing unsporulated oocysts of C. simplex 33 days after being fed the first two of five mice. Viper #151 was inoculated orally with sporulated oocysts of C. simplex obtained from viper #150 and began passing oocysts 52 DPI. Viper #152 served as an uninoculated control and did not pass oocysts of any species of coccidian. This study demonstrates that snake/snake and mouse/snake transmission of C. simplex readily occurs.     

Comparison of tracheal mucous transport in rats, guinea pigs, rabbits, and dogs

Tracheal mucous transport was measured using similar techniques in several species. One- to 10-microliter quantities of 99mTc-macroaggregated albumin (99mTc-MAA) were instilled via oral intubation in the distal trachea of rats, rabbits, and dogs. Tracheostomies were used for the instillation in guinea pigs. All animals were anesthetized with halothane for the instillation and allowed to recover immediately in restrainers. Clearance of the 99mTc-MAA in rats and guinea pigs was measured by a slit-collimated NaI scanner. In rabbits and dogs a series of gamma-camera scintiphotos were taken. Clearance was faster and more efficient in dogs than in the other species. No significant differences existed among the rats, rabbits, and guinea pigs in the percentages of the originally deposited material remaining at the instillation site after 1 h (P greater than 0.2). Mean values and standard deviations were 83 +/- 23%, 81 +/- 22% and 70 +/- 20% for rats, guinea pigs, and rabbits, respectively. However, in the dogs a mean of 14 +/- 12% remained at the original site of deposition after only 25 min indicating much more rapid clearance. Mean leading-edge velocities were 9.8 +/- 2.1 (SD) for dogs, 3.2 +/- 1.1 for rabbits, 2.7 +/- 1.4 for guinea pigs, and 1.9 +/- 0.7 mm/min for rats. Clearance patterns qualitatively among the species. In dogs the material moved as a few discrete boluses, whereas in the other species the activity spread toward the larynx. The relatively slow mucous transport of rats, rabbits, and guinea pigs could have important implications in inhalation toxicological studies.     

Oocyst shedding by cats fed isolated bradyzoites and comparison of infectivity of bradyzoites of the VEG strain Toxoplasma gondii to cats and mice

Infectivity of bradyzoites of the VEG strain of Toxoplasma gondii was compared in cats and mice. For this, tissue cysts were separated from brains of infected mice using a Percoll gradient, and bradyzoites were released by incubation in acidic pepsin solution. After filtration through a 3-microm filter, bradyzoites were counted and diluted 10-fold in RPMI tissue culture medium. Dilutions estimated to have 1, 10, 100, and 1,000 bradyzoites were fed to cats and inoculated into mice, orally or subcutaneously (s.c.). Three experiments were performed. In experiment 1, 2 of 2 cats fed 1,000 bradyzoites, 1 of 2 cats fed 100 bradyzoites, 1 of 4 cats fed 10 bradyzoites, and 1 of 4 cats fed 1 bradyzoite shed millions of oocysts; 1,000 bradyzoites were infective to all 4 inoculated mice s.c. but not to 4 mice inoculated orally, and 100 bradyzoites were infective to 2 of 4 mice injected s.c. but not to 4 mice inoculated orally. All 16 mice (8 oral, 8 s.c.) injected with 1 or 10 bradyzoites were negative for T. gondii. In experiment 2, 1 of 4 cats fed 10 counted bradyzoites shed oocysts; the same inocula were not infective to 4 mice injected s.c. In experiment 3, 3 of 4 cats fed 1,000 bradyzoites shed oocysts and the inocula were infective to 10 of 10 mice s.c. and 4 of 10 mice orally; 4 of 4 cats fed 100 bradyzoites shed oocysts and the inocula were infective to 6 of 10 mice s.c. and 0 of 10 mice orally; 10 bradyzoites were not infective to cats and mice. Results indicate that bradyzoites are more infective to cats than to mice, and cats can shed millions of oocysts after ingesting just a few bradyzoites.     

Comparison of the host ranges and antigenicity of Cryptosporidium parvum and Cryptosporidium wrairi from guinea pigs.

Oocysts of a Cryptosporidium isolate from guinea pigs were not infectious for adult mice, but were infectious for two of three newborn calves and for suckling mice. However, oocysts isolated from calves or mice infected with guinea pig Cryptosporidium were not infectious for guinea pigs. Four isolates of C. parvum from calves were incapable of infecting weanling guinea pigs. Microscopic examination of tissue from the colon and cecum of suckling guinea pigs inoculated with C. parvum revealed sparse infection of some pups. These host range studies and previously described differences in 125I-labeled oocyst surface protein profiles between Cryptosporidium sp. from guinea pigs and C. parvum suggest they are distinct species. We propose the name Cryptosporidium wrairi be retained. Studies with monoclonal antibodies indicate that C. wrairi and C. parvum are antigenically related.     

Effect of hyperimmune bovine colostrum raised against Cryptosporidium parvum on infection of guinea pigs by Cryptosporidium wrairi.

Oocysts shedding was markedly reduced in guinea pigs inoculated intraintestinally with Cryptosporidium wrairi sporozoites that had been incubated with hyperimmune bovine colostrum raised to C. parvum when compared with shedding in guinea pigs inoculated with sporozoites incubated in either non-immune bovine colostrum or buffered saline. However oocyst shedding was apparently not reduced in guinea pigs inoculated by gavage with oocysts of C. wrairi and subsequently treated twice daily per os with hyperimmune bovine colostrum. Similarly, oocyst shedding was apparently not reduced by oral treatment with hyperimmune bovine colostrum when treatment was begun simultaneously with inoculation of C. wrairi oocysts.     

Correlation of Propionibacterium acnes Populations with the Presence of Triglycerides on Nonhuman Skin

The skins of mice, rats, rabbits, sheep, guinea pigs, and dogs were cultured for Propionibacterium acnes. Only the sebaceous regions (perianal gland) of guinea pigs harbored a significant P. acnes population. Analysis of the lipid from this region revealed a significant percentage of triglycerides, compounds lacking in the sebum of the other animals.