Dietary lutein stimulates immune response in the canine

The possible immuno-modulatory action of dietary lutein in dogs is not known. Female Beagle dogs (17-18-month old; 11.4+/-0.4kg body weight) were supplemented daily with 0, 5, 10 or 20mg lutein for 12 weeks. Delayed-type hypersensitivity (DTH) response to saline, phytohemagglutinin (PHA) and a polyvalent vaccine was assessed on Weeks 0, 6 and 12. Blood was sampled on Weeks 0, 2, 4, 8 and 12 to assess (1) lymphocyte proliferative response to PHA, concanavalin A (Con A), and pokeweed mitogen (PWM), (2) changes in peripheral blood mononuclear cell (PBMC) populations, (3) interleukin-2 (IL-2) production and (4) IgG and IgM production. After the completion of 12-week study, we continued to collect the blood weekly up to 17 weeks to evaluate the changes in immunoglobulin production upon first and second antigenic challenges on Weeks 13 and 15. Plasma lutein+zeaxanthin was undetectable in unsupplemented dogs but concentrations increased (P<0.05) rapidly on Week 2 in lutein-supplemented dogs. Thereafter, concentrations generally continued to increase in dose-dependent manner, albeit at a much slower rate. Dogs fed lutein had heightened DTH response to PHA and vaccine by Week 6. Dietary lutein increased (P<0.05) lymphocyte proliferative response to all three mitogens and increased the percentages of cells expressing CD5, CD4, CD8 and major histocompatibility complex class II (MHC II) molecules. The production of IgG increased (P<0.05) in lutein-fed dogs after the second antigenic challenge. Lutein did not influence the expression of CD21 lymphocyte marker, plasma IgM or IL-2 production. Therefore, dietary lutein stimulated both cell-mediated and humoral immune responses in the domestic canine.     

Astaxanthin stimulates cell-mediated and humoral immune responses in cats

Astaxanthin is a potent antioxidant carotenoid and may play a role in modulating immune response in cats. Blood was taken from female domestic shorthair cats (8-9 mo old; 3.2 ± 0.04 kg body weight) fed 0, 1, 5 or 10mg astaxanthin daily for 12 wk to assess peripheral blood mononuclear cell (PBMC) proliferation response, leukocyte subpopulations, natural killer (NK) cell cytotoxic activity, and plasma IgG and IgM concentration. Cutaneous delayed-type hypersensitivity (DTH) response against concanavalin A and an attenuated polyvalent vaccine was assessed on wk 8 (prior to vaccination) and 12 (post-vaccination). There was a dose-related increase in plasma astaxanthin concentrations, with maximum concentrations observed on wk 12. Dietary astaxanthin enhanced DTH response to both the specific (vaccine) and nonspecific (concanavalin A) antigens. In addition, cats fed astaxanthin had heightened PBMC proliferation and NK cell cytotoxic activity. The population of CD3(+) total T and CD4(+) T helper cells were also higher in astaxanthin-fed cats; however, no treatment difference was found with the CD8(+) T cytotoxic and MHC II(+) activated lymphocyte cell populations. Dietary astaxanthin increased concentrations of plasma IgG and IgM. Therefore, dietary astaxanthin heightened cell-mediated and humoral immune responses in cats.     

Effect of prolonged subclinical infection with Trichostrongylus colubriformis on the performance and nitrogen metabolism of growing lambs

Ten 5-month-old lambs, reared free of parasites and prepared with abomasal and ileal cannulas, were paired and given rations of pelleted dried grass by means of continuous feeders. From 7 months of age one of each pair was dosed daily with 2500 Trichostrongylus colubriformis larvae for 34 weeks. An untreated animal served as a pair-fed control to each infected lamb. During 5 experimental periods (pre-infection, and Weeks 6-8, 12-14, 18-20 and 29-34 of dosing) measurements were made of the amounts of N leaving the small intestine, the digestibility of 35[S]-labelled microbial protein in the small intestine, and the amounts of plasma protein leaking into the digestive tract. The infection caused a growth check (P less than 0.05) from Week 6 to approximately Week 13 of dosing. This resulted from inappetence, but also from a disruption in the N digestion and metabolism of the lambs. There was a marked eosinophilia at this time. Measurements of ileal flow rates during Weeks 6 and 12 indicated that significantly more N flowed to the terminal ileum of infected lambs during this period (Week 6, 3.1 g N day-1 P less than 0.05; Week 12, 5.0 g N day-1 P less than 0.001). Plasma N leakage into the intestine during Weeks 8 and 14 was higher in infected lambs (1.2 g N day-1 P less than 0.01 and 0.9 g N day-1 P less than 0.05, respectively) but the digestibility of 35[S]-labelled microbial protein was depressed below that of the controls during the later part of this period, i.e. during Week 13. Continued larval challenge beyond this point caused a less severe nutritional penalty. Voluntary feed intake increased and the animals started to gain weight. The amount of extra N flowing to the terminal ileum of infected lambs was less at Week 18 of dosing (3.5 g N day-1 P less than 0.01) than it had been at Week 12. Similarly, extra plasma N leakage into the tract of infected lambs was less during Week 20 (0.26 g N day-1) than during Week 14. There was however, still a detectable reduction in the coefficient of digestibility of 35S microbial protein in infected lambs during Week 19. By Weeks 29-34 the only detectable difference between the infected and control lambs was in their eosinophil counts.     

Dietary astaxanthin enhances immune response in dogs

No information is available on the possible role of astaxanthin on immune response in domestic canine. Female Beagle dogs (9-10 mo old; 8.2 ± 0.2 kg body weight) were fed 0, 10, 20 or 40 mg astaxanthin daily and blood sampled on wk 0, 6, 12, and 16 for assessing the following: lymphoproliferation, leukocyte subpopulations, natural killer (NK) cell cytotoxicity, and concentrations of blood astaxanthin, IgG, IgM and acute phase proteins. Delayed-type hypersensitivity (DTH) response was assessed on wk 0, 12 and 16. Plasma astaxanthin increased dose-dependently and reached maximum concentrations on wk 6. Dietary astaxanthin enhanced DTH response to vaccine, concanavalin A-induced lymphocyte proliferation (with the 20mg dose at wk 12) and NK cell cytotoxic activity. In addition, dietary astaxanthin increased concentrations of IgG and IgM, and B cell population. Plasma concentrations of C reactive protein were lower in astaxanthin-fed dogs. Therefore, dietary astaxanthin heightened cell-mediated and humoral immune response and reduced DNA damage and inflammation in dogs.     

Altered surface antigen expression on peripheral blood mononuclear cells in cats infected with feline immunodeficiency virus.

Expression of CD4, CD8, IL-2 receptor alpha chain (IL-2R alpha), and MHC class II (MHC-II) on peripheral blood mononuclear cells were examined in cats infected with feline immunodeficiency virus (FIV). CD4/CD8 T cell ratio in FIV-infected cats was slightly decreased, as compared with that in specific-pathogen-free (SPF) cats. However, there was no statistical differences between them. The number of circulating IL-2R alpha+ cells in FIV-infected cats was higher than that in healthy cats, whereas induction of IL-2R alpha expression by concanavalin A (Con A) stimulation was depressed in FIV-infected cats. By using two-color cytofluorometry, Con A-induced enhancement of IL-2R alpha expression was found to be reduced in both CD4+ and CD8+ populations in PBMC from FIV-infected cats. The circulating MHC-II+ cells were also increased in FIV-infected cats. Furthermore, the induction of IL-2R alpha expression on PBMC after Con A-stimulation significantly depressed by FIV inoculation in vitro. These results suggest that FIV activates PBMC in vivo via direct and/or indirect mechanisms, leading to the unresponsive state of T cells to further stimuli in vitro.     

The effect of Johne's vaccination on tuberculin testing in farmed red deer (Cervus elaphus)

AIM: To assess the degree of interference with bovine tuberculin testing in farmed red deer that vaccination of young deer with an oil-adjuvanted vs aqueous formulation of live attenuated Mycobacterium paratuberculosis Strain 316F vaccines would be likely to cause, and to compare immunological responses between vaccine formulations. METHODS: Five-month-old red deer (n = 45) were randomly allocated to three treatment groups of 15 animals, which received either no vaccine, a single 2-ml dose of an oil-adjuvanted formulation or two 2-ml doses, 6 weeks apart, of an aqueous formulation of live attenuated M. paratuberculosis Strain 316F vaccine injected subcutaneously (S/C) in the neck (Control, Oil-adjuvant Ptb, and Aqueous Ptb groups, respectively). Injection- site reactions were described and measured on Weeks 3, 6 and 9. Animals were weighed and lymphocyte transformation tests (LTT) and antibody enzyme-linked immunosorbent assays (ELISA) using avian, bovine and Johnin tuberculin were conducted on blood samples collected at Weeks 0, 6, 12, 15, 24, 27, 36 and 39. A bovine mid-cervical skin test (MCT) was applied at Week 12, and comparative cervical skin tests (CCTs) at Weeks 24 and 36. At Week 42, the animals were slaughtered at a commercial deer slaughter premises and subjected to rigorous meat inspection. RESULTS: Two animals were eliminated at the start of the trial due to a positive cross-reaction with bovine tuberculin in the initial LTT. Almost all animals reacted to the MCT at Week 12, with mean skin thicknesses of 3.9, 2.9 and 1.0 mm for the Oil-adjuvant Ptb, Aqueous Ptb and Control groups, respectively. When the CCT was conducted at Week 24, 2/15 Oil-adjuvant Ptb, 2/14 Aqueous Ptb and 1/14 Control animals were classified as CCT-positive to bovine tuberculin. By Week 36, all animals were CCT-negative. The Oil-adjuvant Ptb vaccination resulted in high persistent levels of antibody that reacted with bovine tuberculin, compared with negligible levels in the Aqueous Ptb group. Overall, a single dose of the Oil-adjuvant Ptb vaccine in deer stimulated a vigorous, cross-reactive immune response, evidenced by high LTT, skin-test and antibody reactions to bovine tuberculin, with both cell-mediated and humoral characteristics. By comparison, two doses of the Aqueous Ptb vaccine produced less cross-reactivity and a bias towards a cell-mediated response. The Oil-adjuvant Ptb vaccine resulted in moderate injection site lesions that were quite persistent, whereas the Aqueous Ptb vaccine resulted in smaller nodules that regressed more quickly. CONCLUSIONS: Vaccination of farmed deer with an oil-adjuvanted Johne's vaccine has the potential to cause significant interference with routine tuberculin skin testing. The cross-reactivity should decline with time and the CCT should be able to clear MCT-positives, but there is a risk of false-positives to the blood test for tuberculosis (BTB), due to high persistent levels of antibody. The CCT could be used as a primary skin test in vaccinated deer on some farms. The Aqueous Ptb caused fewer problems with skin testing and produced significantly less bovine antibody than the Oil-adjuvant Ptb, but stimulated persistent cell-mediated immune responses that may provide some protection against Johne's disease.     

The effect of Johne's vaccination on tuberculin testing in farmed red deer (Cervus elaphus)

AIM: To assess the degree of interference with bovine tuberculin testing in farmed red deer that vaccination of young deer with an oil-adjuvanted vs aqueous formulation of live attenuated Mycobacterium paratuberculosis Strain 316F vaccines would be likely to cause, and to compare immunological responses between vaccine formulations.

METHODS: Five-month-old red deer (n=45) were randomly allocated to three treatment groups of 15 animals, which received either no vaccine, a single 2-ml dose of an oil-adjuvanted formulation or two 2-ml doses, 6 weeks apart, of an aqueous formulation of live attenuated M. paratuberculosis Strain 316F vaccine injected subcutaneously (S/C) in the neck (Control, Oil-adjuvant Ptb, and Aqueous Ptb groups, respectively). Injection-site reactions were described and measured on Weeks 3, 6 and 9. Animals were weighed and lymphocyte transformation tests (LTT) and antibody enzyme-linked immunosorbent assays (ELISA) using avian, bovine and Johnin tuberculin were conducted on blood samples collected at Weeks 0, 6, 12, 15, 24, 27, 36 and 39. A bovine mid-cervical skin test (MCT) was applied at Week 12, and comparative cervical skin tests (CCTs) at Weeks 24 and 36. At Week 42, the animals were slaughtered at a commercial deer slaughter premises and subjected to rigorous meat inspection.

RESULTS: Two animals were eliminated at the start of the trial due to a positive cross-reaction with bovine tuberculin in the initial LTT. Almost all animals reacted to the MCT at Week 12, with mean skin thicknesses of 3.9, 2.9 and 1.0 mm for the Oil- adjuvant Ptb, Aqueous Ptb and Control groups, respectively. When the CCT was conducted at Week 24, 2/15 Oil-adjuvant Ptb, 2/14 Aqueous Ptb and 1/14 Control animals were classified as CCT-positive to bovine tuberculin. By Week 36, all animals were CCT-negative. The Oil-adjuvant Ptb vaccination resulted in high persistent levels of antibody that reacted with bovine tuberculin, compared with negligible levels in the Aqueous Ptb group.

Overall, a single dose of the Oil-adjuvant Ptb vaccine in deer stimulated a vigorous, cross-reactive immune response, evidenced by high LTT, skin-test and antibody reactions to bovine tuberculin, with both cell-mediated and humoral characteristics. By comparison, two doses of the Aqueous Ptb vaccine produced less cross-reactivity and a bias towards a cell-mediated response. The Oil-adjuvant Ptb vaccine resulted in moderate injection- site lesions that were quite persistent, whereas the Aqueous Ptb vaccine resulted in smaller nodules that regressed more quickly.

CONCLUSIONS: Vaccination of farmed deer with an oil-adjuvanted Johne's vaccine has the potential to cause significant interference with routine tuberculin skin testing. The cross-reactivity should decline with time and the CCT should be able to clear MCT-positives, but there is a risk of false-positives to the blood test for tuberculosis (BTB), due to high persistent levels of antibody. The CCT could be used as a primary skin test in vaccinated deer on some farms.

The Aqueous Ptb caused fewer problems with skin testing and produced significantly less bovine antibody than the Oil-adjuvant Ptb, but stimulated persistent cell-mediated immune responses that may provide some protection against Johne's disease.     

Hyperzincaemia in a pet African giant rat (Cricetomys gambianus Waterhouse, 1840)

Presented is an African giant rat (Cricetomys gambianus) following zinc ingestion. The sick rat was lethargic, withdrawn, had soft, mucus-impregnated faeces and diahorrea, foot twitching and icterus. Comparative age, sex and body weight (b.wt.)-matched analyses were made with a healthy giant rat. Twelve-hourly Urine volume (UV), Haematocrit (Hct), urinary glucose, plasma zinc and Alkaline Phosphatase (ALP) were performed over an 8-week period. Full blood counts were performed and differential WBC counts and microscopic observations were made on blood smears obtained from both healthy and sick rats. Consecutive blood samples were drawn at the end of each week (Weeks <2-6 treatment; Weeks 7-8 post-treatment). Treatment involved oral vitamin B12 supplement at 4 microg/day and 2 ml diethylenetriaminepentaacetic acid (DTPA) intramuscular injections at 1 ml/450g b.wt./5 wks (Week 2 - 6). Day 1 showed neutropaenia, Heinz bodies on RBCs (reticulocytes and immature forms). Zinc (Day 1 - end Week 7), glucose (Day 1 - end Week 4), ALP (Day 1 -Week 4) and UV were elevated (Day 1 - end Week 6). Indications of moderate zinc toxicosis following ingestion and stress-associated glucosuria were concluded.     

Efficacy, immune responses and side-effects of vaccines against Johne's disease in young red deer (Cervus elaphus) experimentally challenged with Mycobacterium avium subsp paratuberculosis

AIMS: To test the efficacy of a commercially available and an experimental vaccine against Johne's disease in young red deer (Cervus elaphus), using experimental challenge with live virulent Mycobacterium avium subsp paratuberculosis (M. ptb), measure injection-site reactions, and assess the effects of vaccination and challenge on results of subsequent skin tests and ancillary blood tests for bovine tuberculosis (Tb). METHODS: Ninety 6-8-week-old red deer fawns were randomly allocated to three equal groups of 30, and received either a 1-ml S/C injection of either a commercially available whole-cell killed vaccine with a mineral-oil adjuvant (COM), or a live attenuated M. ptb experimental vaccine with a lipid adjuvant (EXP), or were unvaccinated controls. Ten weeks later (Week 10), all 90 fawns received an oral challenge with approximately 10(8) cfu of a bovine strain of M. ptb daily for 4 days. The fawns were regularly weighed and monitored for clinical signs of Johne's disease, and regularly blood-sampled and tested for antibodies to M. ptb, using the Paralisa test, an IgG1 ELISA, and for antibodies to Mycobacterium bovis, using a similar test. A mid-cervical tuberculin skin test (MCT) was administered at Week 23, and comparative cervical skin tests (CCTs) were administered at Weeks 37 and 57. All animals were electively killed at Week 59, injection sites inspected, gastrointestinal tracts examined for gross lesions, and samples taken for culture and histopathology. RESULTS: There were no clinical cases of Johne's disease but, at slaughter, more gross lesions in intestinal lymph nodes were observed in Control (20%) than COM animals (0%; p<0.05). This latter group also had less severe histopathological lesions in samples of intestines and lymph nodes compared with the Control group (p<0.05), but not deer in the EXP group. Over 89% of deer in all three groups were shown by culture to be infected with M. ptb, while only 21-33% of faecal samples were culture-positive. Time to positive culture was longer for COM vs EXP and Control groups (p<0.01), reflecting fewer M. ptb organisms in samples from the ileocaecal valve (ICV) in that group. Almost all (>or=90%) deer reacted to the MCT at Week 23, and there were no significant differences between groups. One or two deer in each group were classified as Tb reactors to the CCT at Week 37, and none were classified as Tb reactors to the CCT at Week 57. At the time of challenge, over 50% of deer in the COM group were classified as positive (9/28) or suspicious (7/28) for M. ptb antibodies in the Paralisa test, one animal in the EXP group was classified as suspicious, and all the Controls were negative. From Week 23 to the end of the trial, 25/28 (89%) deer in the COM group were Paralisa-positive or -suspicious. The proportion of animals in the EXP and Control groups that were Paralisa-positive peaked at Week 39 (60% and 55%, respectively). The majority of deer in the COM group had significant levels of antibody to M. bovis 10 weeks after vaccination, while the proportion of M. bovis-antibody positive Control deer rose gradually throughout the trial, reaching 23/30 (77%) at slaughter. Injection-site lesions in COM deer ranged from 10-38 mm in diameter 4 weeks after vaccination, and then resolved. Minimal injection-site lesions were observed in EXP deer. At slaughter, 14 months after vaccination, 19/28 deer in the COM group had 5-15-mm nodules that were easily trimmed from the carcass. CONCLUSIONS: The experimental challenge with M. ptb produced subclinical Johne's disease in the majority of deer, but did not cause any clinical disease. The number and severity of gross and microscopic lesions was significantly reduced in the COM compared with Control and EXP groups; vaccination of the EXP group did not appear to give significant protection. Deer vaccinated with the commercial vaccine are likely to give a false-positive reaction to the MCT but should have an avian reaction to the CCT, if it is carried out >12 months after vaccination. Most of the deer vaccinated with the commercial vaccine produced significant levels of antibodies against both M. ptb and M. bovis, which interfered with ancillary Tb tests. If this vaccine or similar oil-based vaccines are used on deer farms in the future, it may be advisable to only vaccinate animals destined for slaughter, that would not need to be Tb-tested, but would be 'works-monitored' for evidence of Tb instead.     

Modulation of sheep lymphocyte responses by Fasciola hepatica excretory-secretory products

The effect of Fasciola hepatica excretory-secretory products (FhESPs) on mitogen-induced proliferation of sheep peripheral blood mononuclear cells (PBMCs) and PBMC subsets (CD2(+), CD4(+), CD8(+), gammadeltaTCR(+) or CD21(+) cells) were studied. PBMCs were incubated with Concanavalin A (ConA) or phytohemagglutinin (PHA) at optimal (1 microg per well) or suboptimal (0.25 microg per well) doses and with FhESPs at several doses (1.25-20 microg per well). PBMC subsets were incubated with ConA at a suboptimal dose and with FhESPs at 5 microg per well. These cells were incubated with or without monocytes (CD14(+) cell). FhESPs slightly increased the proliferation of PBMCs stimulated with optimal doses of PHA. FhESPs (10 and 20 microg per well) inhibited the PBMCs stimulated with optimal doses of ConA. FhESP dose-dependent inhibition was observed on PBMCs stimulated with suboptimal doses of ConA. CD21(+) lymphocytes (B lymphocytes), CD14(+) cells (monocytes) and gammadeltaTCR(+) cells were not stimulated by ConA. T lymphocyte subsets (CD2(+), CD4(+) or CD8(+) cells) proliferation was decreased by FhESPs at 5 microg per well. FhESPs inhibits the ConA-induced stimulation of sheep PBMCs and sheep T lymphocyte subsets. Further studies should be done to investigate the mechanism of this FhESP immunomodulatory effect.     

Effects of live attenuated and killed Salmonella vaccine on T-lymphocyte mediated immunity in laying hens

The impact of live and killed Salmonella vaccines on cell-mediated immunity (CMI) was investigated in 18- and 32-week-old White Leghorn chickens, by assessing splenic lymphocyte proliferation, expression of IL-2 mRNA in concanavalin A (Con A) stimulated cells and flow cytometric analysis of cell subpopulations. Con A and Salmonella enteritidis (SE) flagella induced proliferation of splenocytes were enhanced in the 18- and 32-week-old chickens treated with live vaccine, compared to the corresponding control chickens. Among the killed vaccine treated birds, Con A-mediated response was higher in the 18-week-old chickens compared to the corresponding control birds. Increased proliferation was accompanied by increased CD4 and reduced CD8 and gammadelta T-lymphocytes in the 18-week-old live vaccine treated chickens. Relative expression of IL-2 mRNA in Con A-stimulated splenocytes from 18-week-old birds was not affected by vaccine treatment. Overall, live vaccine was more effective in increasing the lymphocyte proliferation to Con A as well as SE antigen. This enhanced CMI may prove beneficial in protecting chickens against SE infection.     

Evaluation of antiplatelet effects of ticlopidine in cats

OBJECTIVE: To determine whether ticlopidine exerts an antiplatelet effect, estimate the pharmacodynamics of ticlopidine, and evaluate any acute adverse effects associated with administration of ticlopidine in cats. ANIMALS: 8 domestic purpose-bred sexually intact male cats. PROCEDURE: Ticlopidine was administered orally (50 mg, q 24 h; 100 mg, q 24 h; 200 mg, q 24 h; and 250 mg, q 12 h). Each treatment period consisted of 10 days of drug administration. Platelet aggregation studies with adenosine diphosphate (ADP) and collagen and evaluation of oral mucosal bleeding times (OMBTs) were performed on days 3, 7, and 10 during each drug administration. Serotonin was measured to evaluate secretion at baseline and on day 10 for cats that received the 250-mg dosage. RESULTS: A significant reduction in platelet aggregation was detected in response to ADP on days 7 and 10 at 100 mg, on day 3 at 200 mg, and on days 3, 7, and 10 at 250 mg. A significant increase in the OMBT and decrease in serotonin release on day 10 at 250 mg was also detected; however, the cats had anorexia and vomiting at the 250-mg dosage. CONCLUSIONS AND CLINICAL RELEVANCE: Although there was a consistent antiplatelet effect at the 250-mg dosage, there was dose-dependent anorexia and vomiting that we conclude precludes the clinical usefulness of this drug in cats.     

Contribution of propylene glycol-induced Heinz body formation to anemia in cats

Propylene glycol (PG) is a common preservative and source of synthetic carbohydrates in soft-moist pet foods. Propylene glycol was fed to cats for 5 weeks at concentrations found in commercial diets (1.6 g/kg of body weight; 12% of diet on a dry-weight basis) and for 3 weeks at concentrations exceeding usual intake (8 g/kg; 41% of diet). There was a dose-dependent increase in Heinz body percentage to 28% in cats fed the low dose of PG and to 92% in cats fed the high dose. Erythrocyte half-life, measured using [14C]-cyanate hemoglobin (Hb), decreased significantly (P less than 0.05) by 18.8% and 60% in cats fed the low and high PG doses, respectively. The PCV in cats fed the low dose was unaffected, whereas cats fed the high dose had a mean (+/- SEM) decrease in PCV from 33.5 +/- 1.05% to 26.3 +/- 1.45%, accompanied by punctate reticulocytosis and bone marrow erythroid hyperplasia. A dose-dependent increase in iron pigment was found in the liver and spleen of all cats. In cats fed the low dose of PG, erythrocyte reduced glutathione concentration actually increased from 7.02 +/- 0.56 to 9.74 +/- 0.69 mumol/g of Hb, but decreased to 2.96 +/- 0.27 mumol/g of Hb in cats fed the high dose. There was no significant increase in methemoglobin concentration. These results indicated that PG cannot be considered innocuous even at concentrations consumed by cats eating commercial diets. Heinz body-induced acceleration of RBC destruction develops in a dose-dependent manner, so that cats with greater food intake, ie, lactating queens and nursing kittens, are at greater risk for development of PG-induced Heinz body hemolytic anemia.     

Immunization-induced decrease of the CD4+:CD8+ ratio in cats experimentally infected with feline immunodeficiency virus.

In a previous experiment a group of 15 specified pathogen free (SPF) cats were experimentally infected with a Swiss isolate of feline immunodeficiency virus (FIV). A group of 15 SPF cats served as FIV negative controls. Nine cats of each group were vaccinated with a recombinant feline leukemia virus (FeLV) vaccine, six cats in each group with a placebo vaccine. All vaccinated cats developed high antibody titers to FeLV and were protected against subsequent FeLV challenge infection. In both control groups five of six cats became persistently infected with FeLV. Unexpectedly, the primary immune response to the vaccine antigen was significantly higher in the FIV positive group than in the FIV negative. The secondary response was stronger in the FIV negative cats. The goal of the present investigation was to further study the immune response in these 30 cats. They were immunized twice with the synthetic peptide L-tyrosine-L-glutamic acid-poly(DL-alanine)-poly(L-lysine) (TGAL) 21 days apart. Blood samples were collected on four occasions during the immunization process. They were tested for antibodies to TGAL, complete blood cell counts and CD4+, CD8+ and pan-T-lymphocyte counts. The following observations were made: (1) in contrast to the FeLV vaccine experiment, the primary immune response to TGAL was not significantly stronger in the FIV positive cats when tested by enzyme-linked immunosorbent assay (2). The absolute size of the CD4+ lymphocyte population was distinctly smaller in the FIV positive than in the FIV negative cats. The lowest CD4+ values were found in the dually FIV/FeLV infected cats. (3) A population of CD8+ lymphocytes was identified that was characterized by a distinctly weaker fluorescence. The size of this population increased in FIV positive and decreased in FIV negative cats during the TGAL immunization experiment. (4) The CD4+:CD8+ ratio increased in FIV negative cats during TGAL immunization from 1.9 to 2.3. In contrast, in FIV positive animals the CD4+:CD8+ ratio decreased significantly from 1.9 to 1.3 during the same period. From these and earlier data it was concluded that in short-term FIV infection the immune response to T-cell dependent antigens may be increased over that of the controls. Immune suppression develops gradually with duration of the infection. The significant drop of the CD4+:CD8+ ratio over a 5 week immunization period suggests that antigenic stimulation may accelerate the development of immune suppression in FIV positive cats. If this is a general feature, FIV infection may provide a particularly interesting model for studying the pathogenesis of AIDS.     

Uptake of beta-carotene by ovarian and uterine tissues and effects on steroidogenesis during the estrous cycle in cats.

OBJECTIVES: To determine uptake of beta-carotene by ovarian and uterine tissues and influence of dietary beta-carotene on steroidogenesis and production of uterine protein during the estrous cycle in cats. ANIMALS: 56 female cats. PROCEDURE: Cats were fed diets containing 0, 0.4, 2, or 10 mg of beta-carotene daily for 8 weeks prior to detection of estrus. At time of observed estrus, all cats were manually induced to ovulate. Blood samples were obtained at estrus and every 2 days until day 14 after ovulation. On that day, cats underment laparotomy, and the ovaries and uterus were removed. Uterine contents were flushed, and luteal and endometrial tissues were obtained. RESULTS: Concentrations of beta-carotene in plasma and luteal and endometrial tissues increased in a dose-dependent manner. Concentrations of plasma progesterone were higher between days 6 and 10 after ovulation in cats fed diets containing beta-carotene and continued to increase through day 14 after ovulation in cats fed a diet containing 10 mg of beta-carotene. Plasma concentration of estradiol-17beta also was higher between days 0 and 4 after ovulation in cats fed diets containing beta-carotene. Cats fed a diet containing 10 mg of beta-carotene had the highest plasma estradiol concentration. Total uterine protein concentration was higher in cats fed beta-carotene, compared with values for cats fed an unsupplemented diet. CONCLUSION AND CLINICAL RELEVANCE: Cats readily absorb beta-carotene. Increased concentrations of progesterone, estradiol, and uterine protein may provide more optimal ovarian function or a better uterine environment for embryonic survival and development.     

Development of a Delayed-Type Hypersensitivity (DTH) Model in the Cynomolgus Monkey

Although a T-dependent antibody response (TDAR) assay is generally recommended as the first-line immune function assay in nonclinical immunotoxicity evaluation, second-line assays such as delayed-type hypersensitivity (DTH) to measure cell-mediated responses can provide helpful additional information. In this study, male Cynomolgus monkeys were injected intramuscularly either once or twice with 1 mg Keyhole Limpet Hemocyanin (KLH) or twice with a commercially available tetanus vaccine (40 IU tetanus toxoid + 0.06 mg aluminum hydroxide). All animals were subsequently challenged by intradermal injections of the same antigen or aluminum hydroxide after 4, 6 and 8 weeks. Clinical reactions at the injection sites were scored 24, 48 and 72 h post challenge. Skin biopsies were taken on completion of the observation period after each challenge for standard histological examination and immunolabeling using CD3 (T lymphocytes), CD19 (B lymphocytes) and CD68 (macrophages) antibodies. Tetanus toxoid induced stronger clinical reactions than KLH, whereas aluminum hydroxide induced no clinical reaction. Perivascular mononuclear cell infiltrates, a histopathological finding consistent with a DTH reaction, were seen after all challenges with tetanus toxoid or KLH, but not with aluminum hydroxide. Immunohistochemistry evidenced the presence of T lymphocytes and macrophages within these infiltrates. These results suggest that tetanus toxoid adjuvanted with aluminum hydroxide can induce a consistent DTH response for use as a model of cell-mediated response in Cynomolgus monkeys.     

Effects of dietary n-6 and n-3 fatty acids and vitamin E on the immune response of healthy geriatric dogs

OBJECTIVE: To determine the effect of dietary n-6 to n-3 fatty acid ratios and alpha-tocopheryl acetate concentration on immune functions andT cell subpopulations in healthy dogs. ANIMALS: Thirty-two 7- to 10-year old female Beagles. PROCEDURE: For 17 weeks, dogs were fed food that contained low (1.4:1) or high (40:1) ratios of n-6 to n-3 fatty acids in combination with 3 concentrations of all rac-alpha-tocopheryl acetate (low, 17 mg/kg of food; medium, 101 mg/kg; high, 447 mg/kg). Dogs were inoculated twice with a keyhole limpet hemocyanin suspension at 13 and 15 weeks. RESULTS: After 12 weeks, dogs consuming low concentrations of alpha-tocopheryl acetate had lower percentages of CD8+ T cells, compared with dogs consuming medium or high alpha-tocopheryl acetate concentrations. Also, dogs consuming low alpha-tocopheryl acetate concentrations had higher CD4+ to CD8+ T cell ratios. On day 4 of week 15, the percentage of CD8+ T cells was highest in dogs fed medium concentrations of alpha-tocopheryl acetate, compared with other dogs; however, the CD4+ to CD8+ T cell ratio was higher only in dogs fed low concentrations of alpha-tocopheryl acetate with high concentrations of n-3 fatty acids. Dogs consuming low concentrations of n-3 fatty acids with medium concentrations of alpha-tocopheryl acetate had the largest delayed-type hypersensitivity (DTH) skin test response. CONCLUSIONS AND CLINICAL RELEVANCE: An optimum amount of dietary alpha-tocopheryl acetate concentration, regardless of the dietary n-6 to n-3 fatty acid ratio, stimulates the CD8+ T cell population. Effects of an optimum amount of dietary alpha-tocopheryl acetate concentration on the DTH response are blunted by dietary n-3 fatty acids.     

Immunohistochemical characterisation of the lymph node reaction in pig post-weaning multisystemic wasting syndrome (PMWS)

The goal of this study was to identify a strain of feline immunodeficiency virus (FIV) that would be more virulent for adult cats than the prototype FIV-APetaluma and, thereby, enhance the FIV infection model for HIV-1 related research. Diehl et al. reported that one clade C strain of FIV, FIV-CPGammar, was more virulent than other known FIV isolates. Mortalities from 58 to 100% were reported for kittens 12 weeks of age and less following intravenous inoculation. A more variable and somewhat less virulent disease course was observed in neonatal to 8-10-week-old kittens infected orally, intravaginally or intrarectally with this same isolate (Obert and Hoover, 2000). However, no studies have been done with FIV-CPGammar in adult cats. Therefore, the virulence of FIV-CPGammar for young adult cats was compared to that of FIV-APetalulma, the original FIV isolate. One group of five cats were inoculated intraperitoneally with 470 TCID(50) of FIV-CPGammar in the form of pooled plasma from acutely infected cats, while a second group was infected with plasma containing the 750 TCID50 of FIV-APetaluma. The cats were observed for 20 weeks for gross signs of disease, hematologic abnormalities, time of antibody appearance, and plasma and peripheral blood mononuclear cell (PBMC) associated virus levels. Viral RNA and proviral DNA were measured by a real-time PCR, sensitive to 50 copies per milliliter. The only outward sign of disease was lymphadenopathy, which occurred at a similar time and intensity in both groups of cats. Cats infected with FIV-CPGammar were more likely to be neutropenic and lymphopenic during the first 10-12 weeks of infection than cats infected with FIV-APetaluma. Both groups of cats showed similar overall declines in absolute mean CD4 cell counts and identical concomitant increases in CD8 cells. CD4/CD8 cell ratios were also similar. Antibody, as measured by an ELISA against recombinant FIV-TM antigen, appeared in all cats by 4 weeks post-infection. The most significant differences were in plasma viral RNA and PBMC proviral DNA levels. Cats infected with FIV-CPGammar had up to 100 times higher mean levels of viral RNA during the first few weeks of infection than cats infected with FIV-APetaluma. This difference was also mirrored in levels of proviral DNA in PBMC, which were significantly higher in the FIV-CPGammar infected cats. Plasma viral RNA and PBMC proviral DNA levels were virtually identical in both groups of cats at 20 weeks post-infection. However, proviral DNA in tissues such as thymus and popliteal lymph nodes was 10-fold or so higher in FIV-CPGammar infected cats at 20 weeks and histopathologic lesions were more severe. Based on these various parameters, we concluded that FIV-CPGammar was more virulent than FIV-APetaluma in young adult cats during the 20-week study period. However, we were not able to recreate the severe and rapidly progressive disease previously reported for kittens, suggesting an age-related resistance similar to that observed previously for FIV-APetaluma (George et al., 1993).     

Protection against feline leukemia virus challenge for at least 2 years after vaccination with an inactivated feline leukemia virus vaccine

Twelve cats were vaccinated at 8 and 11 weeks of age with a commercially available inactivated FeLV vaccine (Nobivac FeLV, Intervet/Schering-Plough Animal Health). Eleven cats served as age-matched, placebo-vaccinated controls. All cats were kept in isolation for 2 years after vaccination and were then challenged with virulent FeLV to evaluate vaccine efficacy and duration of immunity. Cats were monitored for 12 weeks after challenge for development of persistent viremia using a commercial FeLV p27 ELISA. Persistent viremia developed in all 11 (100%) of the control cats, whereas 10 of 12 (83%) vaccinated cats were fully protected from persistent viremia following challenge. The results demonstrate that the vaccine used in this study protects cats from persistent FeLV viremia for at least 2 years after vaccination.