Experimental Mycoplasma pulmonis infection of rats suppresses humoral but not cellular immune response

Humoral antibody response to sheep red blood cells and cellular immune response to bovine serum albumin were studied in Mycoplasma pulmonis infected, adult, male Sprague-Dawley rats. The hemagglutinating antibody response to sheep red blood cells was evaluated at 0, 3, 5, 7, 14, 21 and 28 days postinfection. Antibody titers during all days postinfection were depressed significantly (p less than 0.05) in infected rats as compared to noninfected controls. Cellular immune responses were evaluated by a delayed hypersensitivity response. Rats were sensitized at 0, 3, 5, 7, 14, 21 or 28 days postinfection with bovine serum albumin and challenged with heat aggregated bovine serum albumin 7 days later. Cell-mediated immune responses in infected rats were not significantly different at any point from controls. These results indicate that M. pulmonis infection in rats suppresses the humoral antibody response to sheep red blood cells, but not the cellular immune response to bovine serum albumin.     

Physiological responses of rats to primary infection with Nippostrongylus brasiliensis

The physiological responses of well-nourished rats to primary infection with the intestinal nematode Nippostrongylus brasiliensis were examined. Infected rats fed ad libitum were compared with uninfected control rats fed ad lib. and with uninfected rats which were pair-fed to the infected rats. Following infection with N. brasiliensis rat food intake was reduced from day 2 post infection (pi) and there were two periods of minimal food intake (days 2 to 3 and 8 to 9 pi). The water intake of infected rats was only reduced on days 2, 3 and 9 pi and not to the same extent as food intake. Muscle catabolism in infected rats was more severe than could be explained on the basis of their food intake reduction. The rectal temperature and rate of oxygen consumption per g body-weight of rats was not significantly altered by the infection. Host responses to N. brasiliensis are compared with those seen in microbial infections and some of them are found to be considerably different.     

Nippostrongylus brasiliensis: changes in plasma levels of gastrointestinal hormones in the infected rat

Plasma concentrations of gastrointestinal hormones were measured by radioimmunoassay in fasted rats 9 days after infection with a range of doses of Nippostrongylus brasiliensis. Values for infected rats fed ad libitum were compared with those of weight matched, pair fed, uninfected rats to control for the possible effects of dose-dependent reductions in food intake associated with infection. The plasma concentrations of some of the gastrointestinal hormones in infected rats were very different from those of their pair fed partners. The magnitude and direction of the changes varied according to the hormone being examined. Plasma concentrations of gastrin and pancreatic polypeptide were similar in pair fed and infected rats at all doses used. For the other hormones assayed, infection was associated with dose-related changes. The plasma concentrations of cholecystokinin and insulin were slightly but significantly reduced in infected rats. In contrast, secretin, enteroglucagon, and pancreatic glucagon concentrations were markedly increased. At the highest dose given (52 larvae/g body wt), the plasma levels of secretin and enteroglucagon in infected rats were elevated 9 X and 15 X, respectively. A comparison of the changes seen in N. brasiliensis-infected rats with those reported for other helminth infections revealed striking differences. The possible etiology of alterations in plasma gastrointestinal hormone concentrations and their contribution to the pathological changes seen in animals infected with helminths are discussed.     

Serodiagnosis of cilia-associated respiratory bacillus infection by the indirect immunofluorescence assay technique

Antibody to cilia-associated respiratory (CAR) bacillus was detected by the indirect immunofluorescence assay (IFA) technique using tracheal sections of infected mice as antigen in serum samples collected from rats infected naturally and experimentally. Nine of 23 cases of natural infection were positive in IFA antibody, with titres ranging from 1:10 to 1:80, and all these antibody-positive cases were also histologically positive. The remaining 14 cases were negative in both IFA antibody and histological diagnosis, even though some of them were infected with Sendai virus and Mycoplasma pulmonis. In the experimental infection, serum samples collected from 18 rats on days 4, 7, 14, 21, 28 and 56 post-inoculation (PI) (three rats for each point) and examined for IFA antibody revealed that seroconversion occurred in one rat on day 14 PI and in three rats on day 21 PI. Antibody titres of 1:80 to 1:160 remained to the termination of the experiment. The IFA technique was useful for the diagnosis of CAR bacillus infection except in the early stage of the infection.     

Effect of praziquantel treatment on pulmonary lesions of rats infected with Paragonimus iloktsuenensis

An experimental pathological study was performed to observe the effect of praziquantel treatment on the pulmonary lesions of the rat lung fluke, Paragonimus iloktsuenensis. The metacercariae were obtained from the freshwater crab, Sesarma dehaani, and 40 rats (wistar) were fed each with 10 metacercariae. On 20 rats praziquantel treatment (100mg/kg/day x 5 days) was done at 5 weeks after the infection while remaining 20 rats were kept untreated for use as controls. The drug-treated rats and the untreated ones were sacrificed 3, 7, 14, 21 or 28 days later for the observation of lung pathology. The rats infected with P. iloktsuenensis showed remarkable pulmonary changes; gross features of hemorrhagic and nodular worm capsules protruded on to the surface of the lung, and histologically local atelectasis, inflammatory cell infiltration, and egg granuloma around the worm capsules each containing one or two worms. Praziquantel treatment of the rats was shown to be highly effective in killing the worms and to lead them to degenerate, as early as in 3 days post-treatment. Almost all worms in the lung were dead and absorbed by the host cells in 21 days post-treatment, except a few living ones seen in a rat of 14-day post-treatment group. In most of the rats treated the pulmonary lesions showed the signs of resolution; regression of worm capsules with mummification of worms, decrease of inflammatory cell infiltration, improvement in the degree of atelectasis, and decreases in the frequency and size of the egg granuloma. From the results it is concluded that praziquantel is highly effective for the treatment of rat P. iloktsuenensis infection in the lung, not only by its direct killing effect of the worms but also due to the excellent resolution capacity of the pulmonary tissues.     

Spirometra mansonoides: effects of plerocercoid infection on glycogen deposition in rats

The effects of infection with plerocercoids of Spirometra mansonoides on tissue glycogen deposition of rats was determined. Hypophysectomized rats infected for two days had higher liver glycogen concentrations than controls and this effect was greatest after one week. Elevated liver glycogen associated with plerocercoid infection was observed in fed animals both at the beginning and at the end of the light period as well as after an overnight fast. Glycogen phosphorylase (1,4 alpha D glucan: orthophosphate alpha glucosyltransferase EC 2.4.1.1.) was inhibited but glucose-6-phosphatase (EC 3.1.3.9) was unaffected in the livers of infected hypophysectomized rats. While this effect is similar to actions of both growth hormone and insulin, plerocercoid infection had no influence on glycogen of cardiac or skeletal muscle at any time. Plerocercoid infection had no effect on the glycogen concentration of any tissue of intact rats.     

Strontium-85 in the fetuses of pregnant rats and mice

Pregnant SPF Wistar rats and ICR/Swiss albino mice were injected in the tail vein with 85SrCl2 with 0.05 mM inactive carrier (SrCl2) given in volumes of 0.1 ml. The activity in the injected volume was about 14 MBq per kg of rat and 13 MBq per kg of mouse. The animals were injected at 2 or 13 days of gestation. The activity retained by the fetuses was quantitatively determined at three stages of the fetal intrauterine development: in rats at 14, 16 and 21 days of gestation, in mice at 14, 16 and 20 days of gestation. The activity of fetuses and/or placentas with fetal membranes was measured using a TESLA automatic gamma counter. Results indicate that fetuses of mice retained a significantly (P less than 0.01) greater percent of strontium activity than fetuses of rats. The highest specific activities (the percentage of total activity retained per gram of fetal tissue) were found in the late pregnancy period (at 21 days of gestation in rats and 20 days of gestation in mice) in animals that were injected with the radionuclide at 13 days of gestation.     

Dual infections of Culex tritaeniorhynchus with West Nile virus and Nosema algerae

Culex tritaeniorhynchus females infected with the microsporidian Nosema algerae, and uninfected control females were compared for susceptibility to infection with West Nile (WN) virus and for the ability to transmit virus. When fed on a high titered dose fo virus, 95% of the control females became infected, whereas only 65% of the N. algerae-infected females were infected with WN virus. However, at two lower viral doses, no differences in susceptibility were observed. No significant differences in transmission ability were found between the N. algerae-infected and control females when tested at 10, 14, and 21 days after infection with WN virus. Also, in mosquitoes dually infected with N. algerae and WN virus, neither agent affected the ability of the other to replicate.     

Iron metabolism in Trypanosoma lewisi infection: serum iron and serum iron-binding capacity.

Progressive changes in iron levels, total iron binding capacity and hematocrit values in sera of rats infected with Trypanosoma lewisi are described. The host dietary group were: (1) complete or full complement; (2) iron-deficient, and (3) pair-fed or calorically restricted. The hematocrit values of T. lewisi-infected rats given the various diets were not significantly different from those of the controls. The decrease in total iron binding capacity (TIBC) of rats inoculated with T. lewisi and fed complete and pair-fed diets ranged up to 15% over uninfected controls. TIBC levels in rats fed an iron-deficient diet and inoculated with T. lewisi ranged up to 32% over uninfected controls. TIBC levels of deficient infected rats were significantly different from the controls from day 90 to infection to the end of the observation period. Serum iron (SI) values of non-infected rats regardless of dietary regimen showed significantly higher values than T. lewisi-infected animals between days 95 and 120. The average SI value, for this period, in adequately fed control rats was 204 +/- 7 microgram/100 ml as compared to 172 +/- 5 microgram/100 for trypanosome-infected rats. SI levels of rats on a pair-fed diet and infected with T. lewisi decreased to 17% over uninfected controls. SI levels of animals on an iron-deficient diet and infected with T. lewisi decreased up to 76% over uninfected controls.     

Rates of bluetongue virus transmission between Culicoides sonorensis and sheep

Abstract.  Two experiments were undertaken to estimate the transmission rates of bluetongue virus (BTV) serotype 1 between a biting midge vector, Culicoides sonorensis (Wirth & Jones) (Ceratopogonidae), and a natural host, sheep. In an experiment to measure the transmission rate from vector to host (V→H), six batches of one, five and 20 intrathoracically infected midges were fed on a total of 18 bluetongue (BT)-naïve sheep. The sheep were then monitored for 21 days for clinical signs of BT, viraemia and antibody response. All sheep fed on by five or 20 midges and five of six sheep fed on by just one midge showed signs of BT, were viraemic and developed antibody. The sixth sheep fed on by a single infected midge did not show signs of BT or have detectable viraemia; it did, however, develop a weak antibody response. A bite from a single infected midge is therefore able to transmit BTV to naïve sheep with 80–100% efficiency. Sheep fed upon by larger numbers of infected midges took less time to reach maximum viraemia and developed stronger antibody responses. Sheep exposed to greater amounts of BTV in feeding midges developed a higher level of viraemia and stronger antibody responses. In a second experiment to measure the transmission rate from host to vector (H→V), batches of up to 500 uninfected female C. sonorensis fed every 1–2 days on two experimentally infected sheep during the course of infection. Of 3929 engorged midges that were individually titrated after surviving the extrinsic incubation period, only 23 (0.6%) were infected with BTV. Viraemia in the sheep extended for up to 19 days post-inoculation. No infected midges, however, were detected from 14 days post-infection.     

Trypanosoma lewisi: effects of immunosuppression on the serological reactivities of exoantigens and cellular antigens of bloodstream parasites.

Groups of rats were immunosuppressed with antithymocyte serum (ATS) and infected with Trypanosoma lewisi. Immunodiffusion studies were performed which demonstrated that trypanosome exoantigens, present in the plasma of these animals, were precipitated by antibodies in the sera of rats undergoing a typical primary T. lewisi infection; extracts of trypanosomes which had been collected from ATS-treated rats contained antigens which also were precipitated by antibodies in these sera. These precipitating antibodies could not be detected using either the plasma of untreated infected rats or extracts of trypanosomes which had been collected from untreated rats. With the exoantigens, precipitating antibodies were detected in serum samples collected from rats 14 to 250 days after infection. With the extract, precipitating antibodies were found as early as 5 days after infection and could be detected as late as 90 days after infection. Antigens of trypanosome extracts partially blocked the precipitin reactions between antisera and exoantigens, suggesting the presence of common antigens in the two preparations. Intact trypanosomes were serologically more reactive when collected from immunosuppressed rats. Trypanosomes collected from ATS-treated rats were agglutinated by antisera at titers fourfold higher than trypanosomes collected from untreated hosts. Absorption with exoantigens from immunosuppressed infected rats blocked trypanosome agglutination, indicating that these antigens are of cell surface origin. The experiments suggest that a likely result of immunosuppressing the host is a trypanosome antigen preparation that is a more reactive serodiagnostic reagent.     

Trypanosoma cruzi: immunoglobulin isotype profiles during the acute phase of canine experimental infection with metacyclic or blood trypomastigotes

A detailed investigation has been carried out about the serological profiles of groups of dogs experimentally infected with metacyclic (MT) or blood (BT) trypomastigotes of Berenice-78 Trypanosoma cruzi strain. Peripheral blood was collected from infected dogs and uninfected controls, weekly during 35 days following the acute phase of infection, and immunoglobulin profiles were determined by ELISA. Dogs infected with BT exhibited unaltered levels of IgG2, increases in IgM, IgE, IgA, IgG and IgG1. In contrast, dogs infected with MT presented unaltered levels of IgE and IgG1 and an increase in IgM, IgA, IgG and IgG2 levels. Compared with the MT group, animals infected with BT showed significant increases in IgM on days 7, 14 and 28, in IgA on days 7, 14 and 21, in IgE on days 7 and 14, in IgG on days 14 and 28, and in IgG1 on days 7, 14 and 21. Parasitemia levels of the infected animals were measured over the same time period. No correlations were found between the immunoglobulin profiles and the parasitemia levels. The results demonstrated that the inoculum source (BT or MT) influence the immunoglobulin isotype profile that may drive distinct outcome of acute canine Chagas disease.     

Host specificity of Pisidium coreanum (Bivalvia: Sphaeriidae) to larval infection with a human intestinal fluke Echinostoma cinetorchis (Trematoda: Echinostomatidae) in Korea

The fingernail clam, Pisidium coreanum, has been traditionally consumed raw as a so-called drug therapy by patients with bone fractures in Korea. The present study was designed to determine the possible occurrence and, if present, the prevalence of Echinostoma cinetorchis in P. coreanum collected at a local site, and to determine the susceptibility of the clams in the laboratory to infection with miracidia and cercariae of E. cinetorchis. No cercariae or metacercariae of E. cinetorchis were observed in field-collected P. coreanum clams. In susceptibility experiments with laboratory-reared clams, individuals exposed to miracidia of E. cinetorchis did not release cercariae by 20 days after exposure; necropsy of exposed clams failed to show development of any sporocysts or rediae. To confirm the possibility of these clams serving as an experimental second intermediate host of E. cinetorchis, 20 of them were exposed to E. cinetorchis cercariae from experimentally infected Segmentina hemisphaerula that had been previously exposed to miracidia of E. cinetorchis; all exposed clams became infected. Metacercariae from clams at 14 days postinfection were fed to rats, and adult worms were recovered from the ileocecal regions. This is the first report of P. coreanum serving as second intermediate host of E. cinetorchis.     

Mallard ducklings (Anas platyrhynchos) experimentally infected with Echinostoma trivolvis (Digenea)

Of 8, day-old mallard ducklings, each fed 50 encysted metacercariae of Echinostoma trivolvis, 4 (50%) were infected 15-31 days postinfection (PI) with a total of 10 (2.5%) worms. The worms were attached loosely to the mucosa of the lower ileum and rectum-cloaca, and some were ovigerous by day 15 PI. Ducklings, 4-14 days old when fed encysted metacercariae, became infected with E. trivolvis adults, but ducks 150 days old were refractory to infection. Compared to our previous studies on experimental infections of echinostomes, mallard ducklings were less susceptible than golden hamsters to E. trivolvis.     

Cytomegalovirus aggravates intimal hyperplasia in rats by stimulating smooth muscle cell proliferation

Epidemiological and animal studies suggest a role for cytomegalovirus (CMV) in restenosis. Previously, we demonstrated that proliferating smooth muscle cells (SMCs) in the injured arterial wall are particularly susceptible to CMV-induced effects. Therefore, we hypothesised that, depending on the time point of infection after vascular injury, CMV infection may affect cell proliferation either in the media or in the neointima, thereby aggravating the process of restenosis. In the present study, we focused on the individual layers of the arterial wall by evaluating, besides the neointima-to-media ratio, the medial and neointimal area and cellularity in the rat femoral artery. Vascular injury was photochemically induced in rat femoral arteries. Immediately or 14 days thereafter, rats were infected with rat CMV (RCMV) or mock infected. The presence of RCMV in the vascular wall was determined at 3, 5, 14 and 35 days after infection by quantitative real-time PCR. When rats were infected immediately after injury, a significant increase was seen only in the medial but not in the neointimal cross-sectional area. On the other hand, when rats were infected 14 days after the initial injury, a significant increase was only seen in the neointimal area, thereby confirming our hypothesis that RCMV infection primary affects proliferating SMCs. As the mean number of SMCs per microm2 in both cell layers was unchanged despite an increase in cross-sectional area, this implies that RCMV stimulated SMC proliferation. Furthermore, these vascular effects were observed without the virus being abundantly present in the vascular wall, suggesting that inflammatory and immune-mediated responses to RCMV infection are more important in aggravating the response to vascular injury than the virus itself.     

Identification of the target cells and sequence of infection during experimental infection of ovine fetuses with Cache Valley virus

Cache Valley virus-induced malformations have been previously reproduced in ovine fetuses; however, no studies have established the course of infection of cells and tissues with Cache Valley virus. To address these questions, ovine fetuses at 35 days of gestation were inoculated in utero with Cache Valley virus and euthanized at 7, 10, 14, 21, and 28 days postinfection. On postmortem examination, arthrogryposis and oligohydramnios were observed in some infected fetuses. Morphological studies showed necrosis in the central nervous system and skeletal muscle of infected fetuses evaluated after 7 to 14 days postinfection, and hydrocephalus, micromyelia, and muscular loss were observed in infected fetuses after 21 to 28 days postinfection. Using immunohistochemistry and in situ hybridization, intense Cache Valley virus antigen and RNA staining was detected in the brain, spinal cord, skeletal muscle, and, to a lesser degree, in fetal membranes and other tissues of infected fetuses. Viral antigen and RNA staining decreased in targeted and infected tissues with the progression of the infection.     

Hymenolepis nana: passive transfer of mouse immunity by T-cell subset of phenotype Lyt-1

Mesenteric lymph node cells obtained from donor mice (BALB/c strain) actively immunized by oral inoculation with Hymenolepis nana eggs were syngeneically transferred by intravenous injection into athymic nude mice previously uninfected. The adoptively immunized recipients were then challenged with 1000 H. nana eggs 2 days after cell transfer. The degree of immunity transferred was assessed by examining cysticercoids developed in the intestinal villi of the recipients on Day 4 of challenge infection. The criterion for success in cell transfer of immunity was the complete rejection of cysticercoids as was generally expected in mice infected previously. The transfer of 1.5 X 10(8) immune mesenteric lymph node cells obtained from donors immunized 4 days before cell collection resulted invariably in the complete rejection of cysticercoids, though not less than this cell dosage. The immunity was passively transferable to recipients by T cells, especially by T-cell subset of phenotype Lyt-1 but not those of phenotype Lyt-2.3 and Lyt-1.2.3. However, 1.5 X 10(8) immune mesenteric lymph node cells obtained from donors immunized 21 days before cell transfer and 1.5 X 10(8) immune spleen cells obtained from donors immunized 4 days before cell transfer had little or no effect on the rejection of cysticercoids.     

Experimental transmission of murine typhus by Xenopsylla cheopis flea bites

Transmission of Rickettsia typhi to rats by the bites of Xenopsylla cheopis (Rothschild) fleas was investigated. Procedures rigorously excluded the possibility of contamination of the host skin by flea faeces. Fleas with R. typhi infection (21-25 days post-infection) which fed through bolting cloth (45 min exposure to ten fleas) transmitted rickettsiae with a success rate of 20%. Infective fleas allowed free access to their host for 8 h (10-15 fleas/rat) gave transmission rates of 45-68%. They were also capable of inoculating R. typhi through a membrane of rat skin on a feeder. Only fleas which had been infected for 21 days or longer transmitted R. typhi orally. Oral transmission appeared to be the result of regurgitation of rickettsiae present in the foregut lumen rather than through salivary secretions.     

Corbicula fluminea (Bivalvia: Corbiculidae): a possible second molluscan intermediate host of Echinostoma cinetorchis (Trematoda: Echinostomatidae) in Korea.

More than 1,500 clams of Corbicula fluminea, the most favorable food source of freshwater bivalves in Korea, were collected from 5 localities to examine cercarial and metacercarial infection with Echinostoma cinetorchis. Although 3 clams infected with suspicious E. cinetorchis metacercariae out of 200 specimens collected at Kangjin, Chollanam-do were detected, no cercarial and metacercarial infections with E. cinetorchis were observed in field-collected Corbicula specimens. In the susceptibility experiments with laboratory-reared clams, those infected with miracidia of E. cinetorchis did not release their cercariae up to 60 days after infection. To confirm the identity of second intermediate host of E. cinetorchis experimentally, a total of 30 clams were exposed to the cercariae from Segmentina hemisphaerula that had been infected with miracidia of E. cinetorchis. The clams were susceptible to cercariae of E. cinetorchis with an infection rate of 93.3%. Metacercariae from clams taken more than 7 days after cercarial exposure were fed to rats (S/D strain), and adult worms of E. cinetorchis, characterized by 37-38 collar spines on the head crown, were recovered from the ileocecal regions. This is the first report of C. fluminea as a possible second intermediate host of E. cinetorchis.     

Susceptibility dynamics in neonatal BALB/c mice infected with Cryptosporidium parvum.

BALB/c Mice were infected as neonates and at different ages to study the susceptibility dynamics in this animal model to Cryptosporidium parvum. When 4-day-old animals were infected with 10(5) C. parvum oocysts, parasites were detected in the terminal ileum when the mice became 14-25 days old (10-21 days post-infection [PI]). The percentage of animals positive for parasites was 100% up to the age of 19 days (15 days PI) but decreased immediately thereafter until no parasites were detected in 26-day-old (22 days PI) or older mice. Parasite load also decreased in these animals from 184.7 parasites per high power field in 14-day-old animals (10 days PI) to 0.22 in 25-day-old (21 days PI) mice. In a second study, some neonatal mice became resistant to C. parvum when infection was attempted at day-10 of age (day-15 of age at sacrifice). The susceptibility to C. parvum decreased until 14 days of age (19 days of age at sacrifice) when mice could no longer be infected. Parasite load also decreased in infected mice from 235.6 parasites per high power field (9 days of age at sacrifice) to 0.25 (18 days of age at sacrifice).