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Biomedical subjects

C G Mackintosh

Publications and source records attributed to C G Mackintosh.

At least 37 records · Page 2Linked to original sources
PubMed2000

Mycobacterium bovis-infected cervine alveolar macrophages secrete lymphoreactive lipid antigens.

Tuberculosis is caused by intracellular bacteria belonging to the genus Mycobacterium, including M. tuberculosis and M. bovis. Alveolar macrophages (AMs) are the primary host cell for inhaled mycobacteria. However, little is known about the mechanisms by which infected AMs can process and present mycobacterial antigens to primed lymphocytes and how these responses may affect ensuing protection in the host. In the present study, we sought to determine whether AMs from a naturally susceptible host for Mycobacterium bovis (red deer) could produce and secrete soluble immunoreactive antigens following mycobacterial infection in vitro. Confluent monolayers of deer AMs were infected with either heat-killed or live virulent M. bovis or M. bovis BCG at a multiplicity of infection of 5:1 and cultured for 48 h. Culture supernatants were collected, concentrated, and tested for the presence of mycobacterial antigens in a lymphocyte proliferation assay by using peripheral blood mononuclear cells from M. bovis-sensitized or naive deer. Supernatants derived from macrophages which had been infected with live bacilli stimulated the proliferation of antigen-sensitized, but not naive, lymphocytes. Supernatants derived from uninoculated AMs or AMs inoculated with heat-killed bacilli failed to stimulate lymphocyte proliferation. The lymphoproliferative activity was retained following lipid extraction of the supernatants, which were free of amino groups as determined by thin-layer chromatography. These results demonstrate that mycobacteria which are actively growing within AMs produce lipids which are secreted into the extracellular milieu and that these lipids are recognized by lymphocytes from mycobacterium-primed hosts. We suggest that mycobacterial lipids are released from AMs following aerosol infection in vivo and that they play an important role in the early immune response to tuberculosis.

Animals↗
PubMed2000

Genetic resistance to experimental infection with Mycobacterium bovis in red deer (Cervus elaphus).

Tuberculosis (Tb) caused by Mycobacterium bovis is a worldwide threat to livestock and humans. One control strategy is to breed livestock that are more resistant to Mycobacterium bovis. In a 3-year heritability study 6 farmed red deer stags were selected from 39 on the basis of their differing responses to experimental challenge via the tonsillar sac with approximately 500 CFU of M. bovis. Two stags remained uninfected, two were moderately affected, and two developed serious spreading Tb. Seventy offspring, bred from these six stags by artificial insemination using stored semen, were similarly challenged with M. bovis. The offspring showed patterns of response to M. bovis challenge similar to those of their sires, providing evidence for a strong genetic basis to resistance to Tb, with an estimated heritability of 0.48 (standard error, 0.096; P < 0. 01). This is the first time the heritability of Tb resistance in domestic livestock has been measured. The breeding of selection lines of resistant and susceptible deer will provide an ideal model to study the mechanisms of Tb resistance in a ruminant and could provide an additional strategy for reducing the number and severity of outbreaks of Tb in farmed deer herds. Laboratory studies to identify genetic and immunological markers for resistance to Tb are under way. Preliminary studies showed no associations between NRAMP or DRB genes and resistance to Tb in deer. Patterns of immune responses seen in resistant animals suggest that both innate and acquired pathways of immunity are necessary to produce the resistant phenotype.

Animals↗
PubMed2000

Systemic but not intra-intestinal vaccination with BCG reduces the severity of tuberculosis infection in ferrets (Mustela furo).

SETTING: Ferrets are important wildlife vectors of bovine tuberculosis (Mycobacterium bovis) in New Zealand. By reducing the severity and/or incidence of tuberculosis (TB) in wild ferret populations, vaccination may limit disease transmission to livestock. OBJECTIVE: To investigate whether vaccination of ferrets with attenuated M. bovis BCG via systemic or intraintestinal routes can reduce the severity of TB resulting from oral M. bovis challenge. DESIGN: Groups of captive ferrets were vaccinated with live BCG via sub-cutaneous injection or intra-duodenal inoculation, twice, 4 weeks apart. Vaccinated and non-vaccinated (control) ferrets were subsequently challenged orally with virulent M. bovis to simulate the natural route of infection. Peripheral blood lymphocyte reactivity was longitudinally monitored, and the outcome of challenge was determined 20 weeks later by autopsy, histology and bacteriological culture. RESULT: Both vaccination routes induced tuberculin-specific lymphocyte reactivity; however, only the subcutaneous route was effective in reducing disease. Subcutaneous vaccinated ferrets had a lower severity of infection than non-vaccinated control animals, as indicated by significant reductions in viable bacterial burdens and prevention of gross lesions in mesenteric lymph nodes (the primary site of infection), and a lower incidence of bacterial translocation to thoracic lymph nodes. However, sub-cutaneous vaccination did not reduce the incidence of mesenteric lymph node infection. CONCLUSIONS: Systemic vaccination with BCG can reduce the severity of TB resulting from oral challenge with virulent M. bovis; however, delivery of viable BCG to the upper intestinal tract may not protect ferrets against TB.

Animals↗
PubMed1999

Intracellular survival of virulent Mycobacterium bovis and M. bovis BCG in ferret macrophages.

The intracellular survival of virulent Mycobacterium bovis and avirulent M. bovis BCG in ferret alveolar macrophages was investigated. In addition, the effects of endogenous and exogenous modulators of macrophage oxidative function on bacterial survival and growth in vitro were determined. Ferret macrophages limited the initial growth of BCG, while virulent M. bovis replicated within macrophages. Intracellular bacterial survival was unaffected by the addition of specific inhibitors of macrophage oxidative function. A T-cell supernatant (TCS), derived from mitogen-stimulated lymphocyte cultures, activated ferret macrophages for heightened oxidative burst performance. However, macrophages activated by TCS, bacterial LPS or a combination of both, failed to control infection, and actually enhanced the intracellular survival of M. bovis. These results are discussed in relation to the role of macrophages in mediating tuberculosis-related pathogenesis, with respect to the fact that ferrets are important wildlife vectors of bovine tuberculosis in New Zealand.

Animals↗
PubMed1999

Oxidative responses in ferret macrophages.

Although the basic function of T and B lymphocytes in ferrets has been known for some time, the function of mononuclear phagocytes has not been described in this species. The present study has characterised basic oxidative responses in ferret macrophages, and has investigated the effects of endogenous and exogenous modulators of macrophage function on oxidative capacity in vitro. Macrophages derived from the blood or lungs of ferrets were shown capable of generating the reactive oxygen intermediate (ROI) molecules superoxide and hydrogen peroxide, and secreting a lysosomal enzyme (acid phosphatase), in response to appropriate stimuli. A T cell supernatant (derived from mitogen-stimulated peripheral blood lymphocytes) was able to activate both blood- and lung-derived macrophages for enhanced ROI production, while specific ROI inhibitors (superoxide dismutase and catalase) were able to partially ablate ROI activity. The accumulation of nitrite in culture supernatants, as an indicator for the production of reactive nitrogen intermediates, could not be demonstrated by ferret macrophages derived from either tissue source. In contrast to the enhancing effects of TCS on the oxidative function of blood-derived macrophages, exposure to bacterial LPS caused marked suppression of ROI and lysosomal enzyme production by these cells. Finally, the generation of superoxide anion, following phagocytosis of live or heat-killed Mycobacterium bovis or zymosan, indicated that ROI production in response to phagocytic stimulation was relatively weak in ferret blood-derived macrophages. These results are discussed in relation to the study of immune function in a novel species, and with particular reference to research into tuberculosis (Tb), since ferrets are important wildlife vectors of bovine Tb in New Zealand.

Animals↗
PubMed1999

Vaccine protocols to optimise the protective efficacy of BCG.

SETTING: A deer model has been developed to study protection produced with BCG vaccination, against infection and the development of pathology, following experimental intratonsilar infection with virulent Mycobacterium bovis. OBJECTIVE: To determine how the dose of vaccine, the route of vaccination, the viability of the vaccine and exposure to glucocorticoids at the time of vaccination, may affect the protective efficacy of BCG vaccines. DESIGN: Deer were vaccinated with BCG and later challenged with virulent M. bovis via the tonsilar route. Protection against infection and development of disease was evaluated at necropsy six months after challenge with M. bovis, by histological examination and microbial culture. RESULTS: Significant protection against infection and disease were obtained following boosting with two low doses (5 x 10(4) cfu) or moderate doses (5 x 10(7) cfu) of live (freshly cultured and lyophilized) BCG. Inferior levels of protection were obtained with high dose (5 x 10(8) cfu) of live BCG. Similar levels of protection were found with vaccines given subcutaneously or via the tonsilar route. Killed vaccine in a mineral-oil adjuvant did not evoke protective immunity and treatment with dexamethasone prior to vaccination with live BCG ablated its efficacy. Protection against infection did not correlate with skin test delayed type hypersensitivity (DTH) or lymphocyte transformation to tuberculin. CONCLUSIONS: Two doses of live BCG gave significant protection against experimental infection and disease caused by virulent M. bovis. Single dose vaccine protected against disease but not infection. Vaccines administered at a dosage which did not evoke DTH, provided protection against tuberculosis infection and disease.

Adjuvants, Immunologic↗
PubMed1999

Partial protection against oral challenge with Mycobacterium bovis in ferrets (Mustela furo) following oral vaccination with BCG.

SETTING: Ferrets (Mustela furo) are important wildlife vectors of bovine tuberculosis (TB) in New Zealand. Protective vaccination of ferrets may limit the potential of transmission to livestock. OBJECTIVE: To determine whether orally-delivered Mycobacterium bovis BCG can confer protection against oral challenge with virulent M. bovis. DESIGN: Ten ferrets were vaccinated by feeding measured doses of live BCG, and subsequently challenged with virulent M. bovis via the oral route. Ten non-vaccinated (control) ferrets were similarly challenged. Live body weights and lymphocyte reactivity were monitored longitudinally, and ferrets were killed 20 weeks following challenge. Necropsy, histological examination and bacterial culture of alimentary tract lymphatic tissues were undertaken. RESULTS: There was a significant reduction in the incidence of gross tuberculous lesions among vaccinated ferrets compared to control animals, and fewer vaccinated ferrets had histologically-detectable acid-fast organisms in mesenteric lymph node (LN) tissues. There were significantly fewer vaccinated ferrets with culture-positive retropharyngeal LNs, and the mean bacterial burden was significantly lower for retropharyngeal LNs isolated from vaccinated animals than from controls. CONCLUSION: These results demonstrate that oral BCG vaccination of ferrets can confer partial protection against M. bovis, and suggest that systemic immune responses may be less important in mediating this degree of protection than local immunity.

Animals↗
PubMed1998

Interpreting comparative experiments on parasite burdens in animals using randomization and canonical variates.

Comparative experiments on parasite burdens present difficulties for modelling and interpretation: data tend to have highly skewed distributions, some standard methods of testing for effects have low power, and there is a need to make allowance for dependencies among the various measurements. Randomization testing and canonical variates analysis are advocated as a means of minimising these problems.

Abomasum↗
PubMed1998

Neuroleptic treatment of red deer calves at weaning.

AIMS: To determine whether neuroleptic drugs could be useful in reducing weaning stress in red deer, two groups of 30 calves were studied following separation from their dams for weaning at 3-4 months of age. METHODS: Within each group, on the day of separation (Day 0), 15 calves were given 0.2 mg/kg haloperidol (a short-acting neuroleptic) and 1 mg/kg perphenazine enanthate (a long-acting neuroleptic) by intramuscular injection (the treated calves) and 15 calves were given a 3 ml intramuscular injection of saline (the control calves). The calves were weighed on Days 0, 14 and 28 and the behaviour of eight individuals (four treated and four control calves) within each group was observed for 2 hours on Days 0, 1, 2, 3, 7, 8, 14 and 15. RESULTS: No significant effect of the treatment on weight gain to Days 14 or 28 was observed (mean increases for treated and control calves to Day 14 were 3.4 kg and 3.5 kg, respectively (s.e.d. 0.26 kg), and 6.0 kg for both treatments to Day 28 (s.e.d. 0.36)). Behavioural variables (standing, grazing, moving, fenceline pacing, proximity to other deer and proximity to the fenceline) did not differ significantly between treatments, but in one group sitting in sternal recumbency was lower in treated calves compared with control calves (p < 0.05). Disturbed behaviour declined over the observation days with fenceline pacing, being within 2 m of a fence, and being within 1 m of another deer decreasing, and sitting and grazing both increasing (p < 0.01). CONCLUSIONS AND CLINICAL RELEVANCE: It was concluded that we could not provide evidence from the present study that treatment with haloperidol and perphenazine enanthate at these dose rates was beneficial in reducing weaning stress in red deer calves.

Journal Article↗
PubMed1998

The efficacy of a pour-on formulation of moxidectin in young red and wapiti-hybrid deer.

AIMS: To measure the efficacy of a pour-on formulation of moxidectin against lungworm and abomasal parasites in weaner wapiti x red deer and to compare this with its efficacy in weaner red deer. METHODS: Six red and six wapiti hybrid deer, naturally infected with lungworm and gastro-intestinal parasites, were treated with pour-on moxidectin at 500 microg/kg body weight and slaughtered 14 or 16 days later, along with six red and six wapiti hybrid untreated control deer. Total worm counts were performed on the lungs, abomasum and abomasal digest of each deer. RESULTS: The efficacy of moxidectin pour-on was 100% against adult and immature lungworms (Dictyocaulus viviparus) in red deer, and 100% and 99.7% effective against adult and immature lungworm in wapiti hybrid deer. The efficacy of moxidectin pour-on was 100, 100, 99.9 and 99.9% respectively against adult, fifth stage, late fourth stage and early fourth stage larvae of Ostertagia-type nematodes (assumed to be Ostertagia, Spiculopteragia, Skrjabinagia and Apteragia spp.) in both red and wapiti hybrid deer. CONCLUSIONS: The pour-on formulation of moxidectin, at 500 microg/kg body weight, is highly effective against mature and immature lungworms and abomasal nematodes in wapiti hybrid deer and equally effective in red deer.

Journal Article↗
PubMed1998

Deer health and disease.

This paper describes the most significant diseases of farmed deer which have emerged over the last 30 or so years. It describes their characteristic signs, how control measures have evolved, their current status and gives an indication of future diagnostic and control measures. Overall, it shows that wild deer brought into a farming environment have developed some of the production limiting diseases which affect sheep and cattle, such as parasitism and trace element deficiencies. In addition, farmed deer are susceptible to potentially fatal diseases such as tuberculosis, malignant catarrhal fever and yersiniosis. A disease which has recently emerged and has the potential to be more serious than any of the above is Johne's disease. In North America, Chronic Wasting Disease occurs in captive and wild deer in only two states but has the potential to be a serious threat to wild and farmed deer elsewhere if it spreads. The zoonotic risks of diseases affecting deer are discussed, as well as stress, welfare and deer restraint. The productivity of farmed deer can be maximised by using a well-designed deer health programme integrated with good management and feeding.

Animal Diseases↗
PubMed1995

Animal models of protective immunity in tuberculosis to evaluate candidate vaccines.

While the etiology of tuberculosis is well understood, the nature of the protective immune response to the causative mycobacteria has remained a mystery. There is an urgent need to define protective immunity critically, and to develop alternative animal models to evaluate the efficacy of new-generation vaccines against tuberculosis in a cost-effective way.

Animals↗
PubMed1994

Development of a diagnostic blood test for tuberculosis in alpacas (Lama pacos).

Vaccination of alpacas (Lama pacos) with heat-killed Mycobacterium bovis (BCG) in oil adjuvant produces an immune response that is able to be measured in vitro. Lymphocyte transformation was present 2 weeks after boosting while antibody as measured by the enzyme-linked immunosorbent assay was present 4-6 weeks after primary vaccination. Two vaccinated animals were positive to the intradermal skin test at the conclusion of the experiment and showed signs of systemic inflammation 72 hours after the skin test, while the controls remained negative for all tests. The BCG vaccine studies showed that these laboratory tests can also identify M. bovis-specific reactivity, so the technique has potential for the diagnosis of tuberculosis in alpacas. Apart from diagnosing M. bovis-specific reactivity, the blood test for tuberculosis may also be used to diagnose non-specific mycobacterial sensitisation in farmed New Zealand alpacas.

Journal Article↗
PubMed1994

A comparison of lungworm faecal larval counts and trichostrongyloid faecal egg counts between red deer (Cervus elaphus) and red deer x wapiti F1 hybrids.

To determine if breed differences in susceptibility to trichostrongyloid and lungworm infection exist, two groups of weaner deer containing seven red deer and red deer x wapiti F1 hybrids were compared using faecal egg counts and faecal larval counts. All animals were run on the same pasture at the same time and treated with the same anthelmintics at the same time. Results indicated that there were significant differences between red deer and red deer x wapiti hybrids, with red deer having higher faecal lungworm counts and red deer x wapiti hybrids having significantly higher faecal egg counts. It is likely that these differences were due to breed. Differences in the efficacy of anthelmintic treatments were also noted between the two groups, with oral oxfendazole being less effective at reducing faecal lungworm counts in red deer X wapiti hybrids than red deer.

Journal Article↗
PubMed1993

BCG vaccination in deer: distinctions between delayed type hypersensitivity and laboratory parameters of immunity.

Groups of deer were vaccinated with live or killed Bacillus Calmette-Guerin (BCG), with and without oil adjuvant, to compare their immune responses with those found in naturally infected animals. Killed BCG in oil induced strong lymphocyte transformation (LT) and antibody (ELISA) responses specific for Mycobacterium bovis antigens. Serum inflammatory proteins (SIP) were also induced after these animals were skin tested. This pattern of reactivity mirrored that found in naturally infected deer with active tuberculosis. Animals vaccinated with live BCG without oil adjuvant also produced strong LT reactivity but this was directed at common mycobacterial antigens found on both M. bovis and M. avium, although no antibody or SIP were detected at any stage of the experiment. The pattern of immune responsiveness to live BCG was similar to that found in naturally infected, but non-diseased deer, and may represent the immunoprotective response to tuberculosis. Significant differences in specificity of lymphocyte transformation and intradermal skin test reactivity to mycobacterial antigens were also identified. Vaccination with BCG in various formulations provides an experimental probe to evaluate the immunological basis of immunity to tuberculosis.

Animals↗
PubMed1992

Occurrence of fumonisin in forage grass in new zealand.

Fumonisin B(1) (FB(1)) was isolated from samples of forage grass originating in paddocks associated with an idiopathic disease of Canadian wapiti and wapiti-red deer hybrids characterized by "ill thrift" and liver dysfunction. Four of 40 samples contained 1, 3, 6, and 9 ppm (micrograms per gram) of FB(1) and 4, 0.5, 2, and 0.5 ppm, respectively, of the methyl ester of FB(1). Analyses were done by ion spray mass spectrometry and confirmed by both fast atom bombardment (solids probe) and mass spectral analysis by electron impact ionization of the trifluoroacetate derivative of the base hydrolyzed product (pentolamine) of FB(1). This article contains the first report of the presence of fumonisin B(1) in grass.

Journal Article↗