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B M Buddle

Publications and source records attributed to B M Buddle.

At least 37 records · Page 2Linked to original sources
PubMed2003

A DNA prime-live vaccine boost strategy in mice can augment IFN-gamma responses to mycobacterial antigens but does not increase the protective efficacy of two attenuated strains of Mycobacterium bovis against bovine tuberculosis.

The Mycobacterium bovis bacille Calmette-Guérin (BCG) vaccine has variable efficacy for both human and bovine tuberculosis. There is a need for improved vaccines or vaccine strategies for control of these diseases. A recently developed prime-boost strategy was investigated for vaccination against M. bovis infection in mice. BALB/c and C57BL/6 mice were primed with a DNA vaccine, expressing two mycobacterial antigens, ESAT-6 and antigen 85 A and boosted with attenuated M. bovis strains, BCG or WAg520, a newly attenuated strain, prior to aerosol challenge. Before challenge, the antigen-specific production of interferon-gamma (IFN-gamma) was evaluated by ELISPOT and antibody responses were measured. The prime-boost stimulated an increase in the numbers of IFN-gamma producing cells compared with DNA or live vaccination alone, but this varied according to the attenuated vaccine strain, time of challenge and the strain of mouse used. Animals vaccinated with DNA alone generated the strongest antibody response to mycobacterial antigens, which was predominantly IgG1. BCG and WAg520 alone generally gave a 1-2 log10 reduction in bacterial load in lungs or spleen, compared to non-vaccinated or plasmid DNA only control groups. The prime-boost regimen was not more effective than BCG or WAg520 alone. These observations demonstrate the comparable efficacy of BCG and WAg520 in a mouse model of bovine tuberculosis. However, priming with the DNA vaccine and boosting with an attenuated M. bovis vaccine enhanced IFN-gamma immune responses compared to vaccinating with an attenuated M. bovis vaccine alone, but did not increase protection against a virulent M. bovis infection.

Animals↗
PubMed2003

Revaccination of neonatal calves with Mycobacterium bovis BCG reduces the level of protection against bovine tuberculosis induced by a single vaccination.

Cattle may provide a suitable model for testing ways of improving tuberculosis vaccine efficacy in human infants. A vaccination and challenge study was undertaken in calves to determine the optimal time to vaccinate neonatal animals with Mycobacterium bovis bacillus Calmette-Guérin (BCG) for protection against tuberculosis and to determine whether revaccination with BCG was beneficial. Calves (10 per group) were vaccinated with BCG within 8 h of birth or at 6 weeks of age, when immune responses to antigens of environmental mycobacteria were detectable, or vaccinated at birth and revaccinated at 6 weeks. A control group was not vaccinated. BCG vaccination at birth induced strong antigen-specific gamma interferon (IFN-gamma) and interleukin-2 (IL-2) responses and antigen-specific activation in CD4(+), CD8(+), and WC1(+) gammadelta T-cell subsets from blood. The proportions of animals per group with macroscopic tuberculous lesions after challenge were 0/10 for BCG at birth, 1/9 for BCG at 6 weeks, 4/10 for the revaccinated group, and 10/10 for the nonvaccinated group. There was no significant difference in the levels of protection between groups vaccinated at birth or at 6 weeks, while animals vaccinated both at birth and at 6 weeks had significantly less protection than those vaccinated only at birth. The revaccinated calves that subsequently developed tuberculous lesions had significantly stronger IFN-gamma and IL-2 responses to bovine purified protein derivative after the BCG booster than those in the same group that did not develop lesions. The results indicated that BCG vaccination at birth induced a high level of immunity and that the sensitization of very young animals to antigens of environmental mycobacteria by 6 weeks of age did not affect the effectiveness of BCG. However, BCG revaccination of these young animals was contraindicated.

Animals↗
PubMed2002

New generation vaccines and delivery systems for control of bovine tuberculosis in cattle and wildlife.

Advances in the understanding of protective immune responses to tuberculosis are providing opportunities for the rational development of improved vaccines for bovine tuberculosis. Protection requires activation of macrophages through stimulation of a Th 1 type immune response. Ideally, a vaccine for cattle should induce protection without causing animals to react in a tuberculin test when exposed to Mycobacterium bovis. A number of new tuberculosis vaccines including attenuated M. bovis strains, killed mycobacteria, protein and DNA vaccines have been developed and many of these are being assessed in cattle. The requirements for a tuberculosis vaccine for wildlife differ from those for cattle. The major goal of a wildlife vaccine is to prevent the transmission of M. bovis to cattle and other wildlife. Although there are a number of technical problems associated with the development of a vaccine delivery system for wildlife, attenuated M. bovis vaccines administered via oral baits or aerosol spray to possums have already been shown to reduce the severity of a subsequent M. bovis infection.

Animals↗
PubMed2002

Vaccination of the brushtail possum (Trichosurus vulpecula) against Mycobacterium bovis infection with bacille Calmette-Guérin: the response to multiple doses.

In New Zealand, the brushtail possum (Trichosurus vulpecula) is the principal wildlife vector of bovine tuberculosis. Control of infected possum populations contributes to the control of tuberculosis in domestic livestock. Vaccination is potentially a complementary strategy to population control, but to be cost-effective, administration of the vaccine to possums would need to be from an appropriately designed automatic vaccinator. Possums themselves would activate the vaccinator so that it would deliver an aerosol spray of vaccine. There would be no direct way to prevent possums receiving multiple doses of vaccine. This study examined the effect on protective immunity of repeated vaccination. Captive possums were vaccinated with BCG strain pasteur 1173P2 either 12 times at weekly intervals, twice at 6-weekly intervals, or once. Vaccination was by a combination of intranasal aerosol and conjunctival instillation. Eight weeks after the last dose of vaccine, all possums were challenged intratracheally with Mycobacterium bovis strain 83/6235. Vaccination induced a significant immune response as measured by the lymphocyte proliferation assay (LPA). A significant level of protection, as measured by the response to challenge, developed in all the vaccinated possum groups, but protection was greatest in the group vaccinated 12 times. It was concluded that protection would be enhanced if vaccinations were repeated at short intervals (weekly), but no benefit or detriment resulted from revaccination after longer intervals (1-2 months).

Administration, Intranasal↗
PubMed2002

The efficacy of bacille Calmette-Guérin vaccine in wild brushtail possums (Trichosurus vulpecula).

A population of wild brushtail possums (Trichosurus vulpecula) in which bovine tuberculosis was endemic was vaccinated with live bacille Calmette-Guérin (BCG) to determine the efficacy of vaccination. The population on the 56 hectare site was monitored bimonthly over 2 years using a capture-release regime. During the study tuberculosis was diagnosed by clinical and post mortem examination. Possums were vaccinated with BCG by both intranasal aerosol and conjunctival instillation. Possums were revaccinated on average every 5 months. Over the 2 years, 300 possums were recruited to the study with 149 being allocated to the vaccination group. There were significantly fewer cases of tuberculosis in the vaccinated (4 cases) than in the unvaccinated group (13 cases; P=0.023). The vaccine efficacy was 69%. An attempt was made to increase the incidence of disease by releasing onto the site possums that had been experimentally infected with a strain of M. bovis unknown in the area. However, this did not result in any additional cases. BCG vaccine was shown to have a level of efficacy which could be of assistance in controlling tuberculosis in wild possum populations. The future use of vaccination for the control of tuberculosis in wild possum populations is discussed.

Aging↗
PubMed2002

Effect of different adjuvants on the immune responses of cattle vaccinated with Mycobacterium tuberculosis culture filtrate proteins.

The development of improved vaccines for bovine tuberculosis is urgently required as a cost effective solution for control and eventual eradication of tuberculosis in domestic animals. Studies in small animal models of tuberculosis have shown that vaccination with culture filtrate proteins (CFP), prepared from Mycobacterium tuberculosis or M. bovis, can induce cellular immune responses and confer a level of protection against aerogenic challenge with virulent mycobacteria. As a first step in the development of a mycobacterial CFP vaccine for protection of cattle against bovine tuberculosis, the immune responses of cattle vaccinated with short-term culture filtrate proteins (ST-CFP) from M. tuberculosis and formulated with different adjuvants were compared with those vaccinated with bacille Calmette-Guerin (BCG). The adjuvants included dimethyldioctyldecyl ammonium bromide (DDA), diethylaminoethyl (DEAE)-dextran, and ST-CFP adsorbed onto polystyrene beads. Vaccination with ST-CFP/DEAE-dextran induced high levels of interleukin-2 (IL-2) but low levels of interferon-gamma (IFN-gamma) from whole-blood cultures stimulated with M. tuberculosis ST-CFP in comparison with the strong IFN-gamma and IL-2 responses induced after vaccination with BCG. ST-CFP/DEAE-dextran also induced a strong antigen-specific immunoglobulin antibody response with both immunoglobulin G1 (IgG1) and IgG2 isotypes. Vaccination with ST-CFP/beads induced a weak IgG1-biased antibody response but no IFN-gamma or IL-2 response. DDA did not induce significant immune responses in animals vaccinated with ST-CFP. In comparison to the moderate delayed-type hypersensitivity (DTH) responses induced by vaccination with subcutaneous BCG, none of the ST-CFP vaccines induced a significant DTH response to either M. tuberculosis ST-CFP or bovine purified protein derivative (PPD). While the ST-CFP vaccines used in this study have not induced strong antigen-specific cellular immune responses in cattle comparable to those induced by BCG, they are immunogenic in cattle and it may be possible to overcome this problem by using adjuvants that more effectively promote IFN-gamma responses in this species.

Adjuvants, Immunologic↗
PubMed2002

Increased protection against bovine tuberculosis in the brushtail possum (Trichosurus vulpecula) when BCG is administered with killed Mycobacterium vaccae.

SETTING: The Australian brushtail possum is the major wildlife reservoir for Mycobacterium bovis infection in New Zealand. Development of an effective tuberculosis vaccine for possums will reduce the spread of infection to cattle and farmed deer. OBJECTIVES: To determine whether killed M. vaccae can improve the efficacy of vaccination with M. bovis bacillus Calmette Guerin (BCG) against bovine tuberculosis in the possum. DESIGN: Groups of possums (n=6-8) were vaccinated via intranasal and intraconjunctival routes with BCG alone or BCG in combination with heat-killed M. vaccae. Controls were non-vaccinated or vaccinated with heat-killed M. vaccae alone. After challenge with virulent M. bovis, protection was assessed by a reduction in loss of body weight and bacterial counts in lungs and spleens. Blood lymphocyte proliferative responses to M. bovis purified protein derivative were monitored throughout. RESULTS: The earliest lymphocyte responses following vaccination were from animals inoculated with BCG plus 100 microg heat-killed M. vaccae. Loss of body weight was significantly reduced in all BCG-vaccinated groups compared control groups. Spleen bacterial counts were significantly lower in animals vaccinated with M. vaccae plus BCG compared to the non-vaccinated group. Furthermore, vaccination with 100 microg M. vaccae plus BCG significantly reduced spleen bacterial counts compared to vaccination with BCG alone. CONCLUSION: The possum infection model is one of the first to show that novel vaccine strategies may offer better protection against tuberculosis than BCG alone.

Animals↗
PubMed2002

Natural transmission of Mycobacterium bovis infection in captive brushtail possums (Trichosurus vulpecula).

AIMS: To examine natural transmission of bovine tuberculosis (Mycobacterium bovis infection) in captive brushtail possums (Trichosurus vulpecula) and to determine if this mode of transmission could be employed to challenge possums in vaccination studies. METHODS: Three experiments were conducted. In Experiment 1, 11 pairs of possums were housed together in cages, one of the pair having been experimentally infected with M. bovis. Of the in-contact possums 5/11 had been vaccinated with bacille Calmette-Guerin (BCG). In Experiment 2, three susceptible possums were placed in a colony of 19 possums that had been experimentally infected with M. bovis. In Experiment 3, the four most socially active possums in each of two colonies (24 possums in one colony and 23 in the other) were experimentally infected with M. bovis, and 10 of the remaining possums in each colony were vaccinated with BCG. RESULTS: In Experiment 1, transmission of M. bovis infection occurred in only 1/11 pairs. In Experiment 2, none of the three in-contact possums became infected. In Experiment 3, infection was transmitted to 5/20 in-contact possums in one colony and 12/19 in-contact possums in the other. The possums that became infected by natural transmission were significantly more socially interactive than those that remained free of infection (p<0.05). CONCLUSIONS: When susceptible and infected possums were randomly mixed, the rate of transmission of M. bovis was low, but when highly sociable possums were infected the rate of transmission increased markedly. The risk of transmission was dependent on the close proximity of infected and susceptible possums and the frequency and duration of their social interactions. Natural transmission from experimentally infected to incontact possums in a colony would be a useful way of studying the pathogenesis of tuberculosis in this species, and the social behaviour of the possums studied should be taken into account. The high degree of variation in the rate of natural transmission of M. bovis infection between possums makes this mode of transmission unreliable for assessing vaccine efficacy.

Journal Article↗
PubMed2002

Production of avirulent mutants of Mycobacterium bovis with vaccine properties by the use of illegitimate recombination and screening of stationary-phase cultures.

A better tuberculosis vaccine is urgently required to control the continuing epidemic. Molecular techniques are now available to produce a better live vaccine than BCG by producing avirulent strains of the Mycobacterium tuberculosis complex with known gene deletions. In this study, 1000 illegitimate recombinants of Mycobacterium bovis were produced by illegitimate recombination with fragments of mycobacterial DNA containing a kanamycin resistance gene. Eight recombinant strains were selected on the basis of their inability to grow when stationary-phase cultures were inoculated into minimal medium. Five of these recombinants were found to be avirulent when inoculated into guinea pigs. Two of the avirulent recombinants produced vaccine efficacy comparable to BCG against an aerosol challenge in guinea pigs with M. bovis. One of these recombinants had an inactivated glnA2 gene encoding a putative glutamine synthetase. Transcriptional analysis showed that inactivation of glnA2 did not affect expression of the downstream glnE gene. The other recombinant had a block of 12 genes deleted, including the sigma factor gene sigG. Two avirulent recombinants with an inactivated pckA gene, encoding phosphoenolpyruvate carboxykinase which catalyses the first step of gluconeogenesis, induced poor protection against tuberculosis. It is clear that live avirulent strains of the M. tuberculosis complex vary widely in their ability as vaccines to protect against tuberculosis. Improved models may be required to more clearly determine the difference in protective effect between BCG and potential new tuberculosis vaccines.

Animals↗
PubMed2002

Identification of novel Mycobacterium tuberculosis antigens with potential as diagnostic reagents or subunit vaccine candidates by comparative genomics.

An independent review for the British government has concluded that the development of a cattle vaccine against Mycobacterium bovis holds the best long-term prospects for tuberculosis control in British herds. The development of complementary diagnostic tests to differentiate between vaccinated and infected animals is necessary to allow the continuation of test-and-slaughter-based control policies alongside vaccination. Vaccination with M. bovis bacillus Calmette-Guérin (BCG), the only available vaccine, results in tuberculin purified protein derivative sensitivity and has shown varying vaccine efficacies in cattle. Thus, identification of more-specific reagents to distinguish between vaccination and infection, as well as the identification of subunit vaccine candidates for improved tuberculosis vaccines, is a research priority. In the present study, we applied comparative genomics to identify M. bovis-Mycobacterium tuberculosis antigens whose genes had been deleted in BCG Pasteur. In total, 13 open reading frames (ORFs) from the RD1, RD2, and RD14 regions of the M. tuberculosis genome were selected. Pools of overlapping peptides spanning these ORFs were tested in M. bovis-infected (n = 22), BCG-vaccinated (n = 6), and unvaccinated (n = 10) control cattle. All were recognized in infected cattle, with responder frequencies varying between 16 and 86%. In particular, eight highly immunogenic antigens were identified whose potentials as diagnostic reagents or as subunit vaccines warrant further study (Rv1983, Rv1986, Rv3872, Rv3873, Rv3878, Rv3879c, Rv1979c, and Rv1769).

Amino Acid Sequence↗
PubMed2001

Aerosol vaccination of the brushtail possum (Trichosurus vulpecula) with bacille Calmette-Guérin: the duration of protection.

Bovine tuberculosis is endemic in wild brushtail possums (Trichosurus vulpecula) in New Zealand. The disease is controlled by reducing or eliminating infected possum populations, but control methods do not kill all possums in the targeted area, leaving some tuberculous possums to maintain the disease. Vaccination with bacille Calmette-Guérin (BCG) has been shown to provide significant levels of protection. Vaccination is a potential alternative or complementary control strategy if protection is long lasting. Captive possums were vaccinated with a single dose of BCG by intranasal aerosol and challenged by intratracheal instillation of Mycobacterium bovis 2, 6 or 12 months after vaccination. Vaccination produced significant immunity as measured by the lymphocyte proliferative response to bovine PPD and protection in response to challenge. The protective response was seen as a decrease in the mass of pulmonary lesions and decreased dissemination to the abdominal organs and body lymph nodes. The protective effect was strongest at 2 months after vaccination but was still present at a lower level at 12 months. Delivery of an aerosol vaccine to possums in the wild using a self-delivery system could contribute substantially to wildlife tuberculosis control.

Administration, Intranasal↗
PubMed2001

Use of ESAT-6 in the interferon-gamma test for diagnosis of bovine tuberculosis following skin testing.

The whole blood interferon-gamma (IFN-gamma) test has proven to be a practical ancillary test for re-testing cattle for bovine tuberculosis 8-28 days following tuberculin skin testing. An improvement in the specificity of the IFN-gamma test could further reduce culling of false positive animals. The primary aim of this study was to evaluate a single mycobacterial antigen, ESAT-6 in the IFN-gamma test for use in skin test-positive cattle. These skin test-positive cattle comprised 51 Mycobacterium bovis-infected animals from tuberculosis-infected herds and 85 non-infected animals from tuberculosis-free herds. The test based on ESAT-6 had a higher specificity than the test based on purified protein derivative (PPD) tuberculin, but this was offset by a small decrease in sensitivity. Use of a lower cut-off in the ESAT-6-based test improved the sensitivity, while still maintaining a very high specificity. A secondary aim in the study was to assess the ESAT-6 and PPD-based tests for detecting bovine tuberculosis in skin test-negative animals from a persistently infected herd. The PPD-based test detected the majority of the lesioned or M. bovis-culture positive animals, while the ESAT-6-based test detected a smaller proportion. The false negatives in the IFN-gamma test from both the skin test-negative and positive groups were predominantly M. bovis-culture positive animals with no visible lesions. The current study has shown that a defined specific antigen such as ESAT-6 can markedly improve the specificity of the IFN-gamma test for re-testing skin test-positive animals. An ESAT-6-based IFN-gamma test could be particularly useful to reduce the false positive rate, yet still maintain an acceptable level of sensitivity.

Animals↗
PubMed2001

Vaccination of cattle against Mycobacterium bovis.

Protection of cattle against bovine tuberculosis by vaccination could be an important control strategy in countries where there is persistence of Mycobacterium bovis infection in wildlife and in developing countries where it is not economical to implement a 'test and slaughter' control programme. Early field trials with Bacille Calmette Guerin (BCG) M. bovis vaccine in cattle produced disappointing results, with induction of tuberculin skin-test reactivity following vaccination and low levels of protection. However, recent studies using a low dose of BCG vaccine in cattle have produced more encouraging results and field trials should now be carried out in developing countries to determine whether this low dose BCG vaccination strategy will reduce the spread of infection. The options for new candidate tuberculosis vaccines have increased markedly in the last decade with the advent of new attenuated strains of M. bovis, and sub-unit protein and recombinant DNA vaccines. Some of these new types of vaccines have recently been tested in cattle. New attenuated M. bovis vaccines induced greater protection than BCG vaccine in cattle which had been sensitized to environmental mycobacteria prior to vaccination. In contrast, it has proved difficult to stimulate appropriate immune responses in cattle necessary for protection with sub-unit protein and recombinant DNA vaccines and better immunological adjuvants are required for these types of vaccines. Progress in the development of new tuberculosis vaccines has been very rapid in the past decade and the prospects for vaccination to control and eradicate bovine tuberculosis are encouraging.

Animals↗
PubMed2001

Towards more accurate diagnosis of bovine tuberculosis using defined antigens.

Diagnostic accuracy is of paramount importance in test-and-slaughter programmes for the eradication of bovine tuberculosis (TB). Currently applied methods, such as in vivo skin testing and in vitro interferon-gamma (IFN- gamma) testing, utilize purified protein derivatives (PPDs), which are poorly-defined mixtures containing many individual antigenic components. It is known that false-positive responses to these reagents can occur in cattle which are not infected with TB, largely because of that antigenic complexity. This paper reviews recent approaches to the characterization of more precisely defined diagnostic tools which can be used to develop tests with greater specificity. For example, the low mass secreted protein ESAT-6 has been shown to be capable of differentiating TB-infected cattle from those which develop responsiveness to PPD through contact with environmental mycobacteria or vaccination with BCG. The information which has accumulated in recent years has shown that the increased specificity is associated with some decrease in test sensitivity, but the overall advantages of being able to make precise diagnostic decisions will have significant advantages in many situations.

Animals↗
PubMed2001

In vitro control of Mycobacterium bovis by macrophages.

Mycobacterium bovis is frequently seen inside macrophages in vivo. The outcome of M. bovis infection depends on T cell interactions with macrophages, however mycobacteria are thought to be relatively resistant to macrophage killing. Little is known about the immunological mechanisms which control intracellular growth of M. bovis, and in the absence of T cell help the organism is capable of intracellular survival and replication. We have investigated the role of macrophages in controlling growth of virulent M. bovis or M. bovis BCG in vitro. At a multiplicity of infection of 5:1, macrophages from a range of animal species including cattle, deer, possums, ferrets and mice restricted growth of BCG while M. bovis grew progressively. Inter-species variation in controlling growth of M. bovis by alveolar macrophages was observed. Pre-treatment of macrophages with interferon-gamma and lipopolysaccharide inhibited intracellular growth of M. bovis. Addition of freshly recruited macrophages further inhibited M. bovis, and intracellular growth was arrested by activated fresh macrophages. Our observations suggest that naïve macrophages can prevent BCG growth, while T cell activation in conjunction with freshly recruited macrophages is required for preventing growth of M. bovis.

Analysis of Variance↗
PubMed2001

Purification of secretory immunoglobulin A from milk of the brushtail possum (Trichosurus vulpecula).

AIM: To identify and purify secretory immunoglobulin A (sIgA), a key effecter molecule in mucosal immune responses, from milk of the brushtail possum (Trichosurus vulpecula). METHODS: Milk samples were collected from female possums with pouch young, and clarified by centrifugation and precipitation methods. The clarified fraction was purified by gel filtration and affinity chromatography to yield sIgA. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDSPAGE) and immunoblotting techniques were used to assess the purity of the final product, and to identify the heavy (H) chain, light (L) chain and secretory component (SC) of possum sIgA. RESULTS: Immunoblotting, using antibodies raised against cloned possum sIgA SC and H-chain, and a synthetic peptide fragment of the H-chain, confirmed the identity of the purified protein. The N-terminal amino acid sequence of purified possum sIgA showed strong homology to reported sequences of H-chain variable regions of marsupial immunoglobulins. CONCLUSIONS: Milk was shown to be a convenient source of mucosal secretion containing sIgA, and a process involving 2 precipitation and 2 chromatography steps produced purified sIgA. This IgA preparation will prove useful for the generation of sIgA-specific immunological reagents for measurement of immune responses in the development of mucosal-based vaccines for biological control of possums.

Journal Article↗
PubMed2001

Vaccination of animals against Mycobacterium bovis.

Vaccination could potentially be used as a practical means of controlling bovine tuberculosis in countries in which a wildlife reservoir of the disease is present, and also in those countries which cannot afford conventional control strategies. An understanding of the processes involved in the protective immune response to tuberculosis is desirable for the rational development and testing of new vaccines for tuberculosis. The authors review current knowledge regarding the processes involved in protective immune responses to tuberculosis, much of which has been derived from studies in mice. This knowledge is discussed in relation to the problem of using vaccination to induce protective immunity in cattle, deer and wildlife. Challenge models have now been developed to test candidate vaccines in many domestic animals and wildlife species and these models are being used to evaluate tuberculosis vaccines. Most studies of the efficacy of tuberculosis vaccines in target animals have focused on the use of bacillus Calmette-Guérin (BCG), an attenuated strain of Mycobacterium bovis. Recent advances in immunology and the molecular biology of mycobacteria have greatly increased the options for candidate vaccines and future studies will test new types of vaccines including new attenuated strains of M. bovis, sub-unit protein vaccines and recombinant deoxyribonucleic acid vaccines. Several of these vaccines have shown promising results when tested in small animal models. Although progress has been made in the development of vaccine delivery systems for animals, the technical problems associated with vaccination of wildlife remain a challenge.

Animals↗