Activation of an interleukin-4 mRNA-producing population of peripheral blood mononuclear cells after infection with Mycobacterium bovis or vaccination with killed, but not live, BCG

Cell-mediated immune response against mycolic acids of Mycobacteroides salmoniphilum in rainbow trout Oncorhynchus mykiss

Mycobacteriosis caused by Mycobacterium spp. causes economic damages to the world aquaculture industry. In mammals, mycolic acids contained in the cell wall of Mycobacterium spp. are presented by CD1b molecule as lipid antigens and induce cell-mediated immunity (CMI). Here, we investigated CMI responses against the mycolic acids of Mycobacterioides salmoniphilum in a CD1-lacking teleost fish, rainbow trout. After stimulation of trout leukocytes with mycolic acids, the number and percentage of CD8α⁺ T cells increased. Fish immunized with mycolic acids showed an up-regulation of IFN-γ. Further, in vitro re-stimulation of leukocytes derived from immunized fish resulted in proliferation of CD8α⁺ cells. These data suggest that mycolic acids are recognized as lipid antigens resulting in an activation of rainbow trout CD8α⁺ cells and up-regulation of the Th1 cytokine IFN-γ. The mycolic acids are promising candidates for vaccines to activate CD8α⁺ T cells against fish mycobacteriosis.

Murine cytokine responses following multiple oral immunizations using lipid-formulated mycobacterial antigens

Oral vaccination of mice with live Mycobacterium bovis BCG in lipid-formulation induces a gamma-interferon response that can be measured systemically, and confers protection against aerosolized mycobacterial challenge. Here, we have investigated cytokine responses following the vaccination, drawing comparisons between mice that received single or multiple oral immunizations and between mice receiving formulations containing live BCG or non-replicating mycobacterial antigens. Single oral immunization with lipid-formulated live BCG invoked secreted and cellular IFN-gamma responses in mice 8 weeks post-vaccination, the magnitudes of which were significantly elevated in mice receiving multiple immunizations over the 8-week period. Single oral immunization with live BCG also invoked an interleukin-2 response (but not TNF-alpha or IL-4), although the magnitude was not elevated by multiple immunizations. Multiple immunizations with lipid-formulated soluble or particulate non-replicating mycobacterial antigens failed to invoke cytokine responses, except for a low-level IFN-gamma response in mice multiple immunized with lipid-formulated heat-killed BCG. These results are discussed in contrast to the known patterns of cytokine induction following parenteral-route immunization with live or non-replicating mycobacterial antigens and with practical reference to the development of oral-delivery vaccines against tuberculosis.

Environmental strains of Mycobacterium avium interfere with immune responses associated with Mycobacterium bovis BCG vaccination

Prior exposure of a vaccinee to certain species of environmental mycobacteria can prime the immune system against common mycobacterial antigens, which can in turn reduce the subsequent efficacy of live attenuated mycobacterial vaccines (such as Mycobacterium bovis BCG), in both human and livestock vaccination programs. In this study, two strains of Mycobacterium avium, both isolated from New Zealand livestock, were investigated to determine their growth characteristics and effects on the immune system in murine models. Markedly different effects on the immune system were observed; an IS901-negative strain (WAg 207) induced significant up-regulation of cell surface activation markers (major histocompatibility complex II, CD80, and CD86) on in vitro-derived dendritic cells and induced the release of proinflammatory monokines (interleukin-1beta [IL-1beta], IL-6, and tumor necrosis factor alpha) in dendritic cell-macrophage cocultures following direct in vitro contact of cells with bacteria. In contrast, an IS901-positive strain (WAg 206) had none of these effects. When mice were exposed to M. avium via oral infection prior to BCG parenteral immunization, both strains were shown to be capable of decreasing subsequent antigen-stimulated gamma interferon secretion by splenic lymphocytes, although this effect was more significant for strain WAg 206. Both strains also induced a mycobacterial antigen-specific serological response in M. avium-sensitized and BCG-immunized mice; this response was greater in WAg 206-sensitized mice, and there was a predominance of immunoglobulin G1 antibody. The down-regulation of IFN-gamma responses and the up-regulation of antibody responses are characteristic of a switch to a type 2 immune response. The different results may be linked to the inherent growth characteristics of the two strains, since WAg 206 was shown to grow slowly in murine macrophages in vitro and to cause a persistent systemic infection following infection in vivo, while WAg 207 grew fast and did not persist in mice. The implications of these findings for BCG vaccination protocols are discussed.

Oral vaccination of brushtail possums with BCG: Investigation into factors that may influence vaccine efficacy and determination of duration of protection

AIMS

To determine factors that may influence the efficacy of an oral pelleted vaccine containing Mycobacterium bovis bacille Calmette-Guérin (BCG) to induce protection of brushtail possums against tuberculosis. To determine the duration of protective immunity following oral administration of BCG.

METHODS

In Study 1, a group of possums (n=7) was immunised by feeding 10 pellets containing dead Pasteur BCG, followed 15 weeks later with a single pellet of live Pasteur BCG. At that time, four other groups of possums (n=7 per group) were given a single pellet of live Pasteur BCG orally, a single pellet of live Danish BCG orally, 10 pellets of live Pasteur BCG orally, or a subcutaneous injection of live Pasteur BCG. For the oral pelleted vaccines, BCG was formulated into a lipid matrix, and each pellet contained approximately 107 colony forming units (cfu) of BCG, while the vaccine injected subcutaneously contained 106 cfu of BCG. A sixth, non-vaccinated, group (n=7) served as a control. All possums were challenged by the aerosol route with a low dose of virulent M. bovis 7 weeks after vaccination, and killed 7-8 weeks after challenge. Protection against challenge with M. bovis was assessed from pathological and bacteriological findings. In Study 2, lipid-formulated live Danish BCG was administered orally to three groups of possums (10-11 per group), and these possums were challenged with virulent M. bovis 8, 29 or 54 weeks later. The possums were killed 7 weeks after challenge, to assess protection in comparison to a non-vaccinated group.

RESULTS

The results from Study 1 showed that vaccine efficacy was not adversely affected by feeding dead BCG prior to live BCG. Feeding 10 vaccine pellets induced a level of protection similar to feeding a single pellet. Protection was similar when feeding possums a single pellet containing the Pasteur or Danish strains of BCG. All vaccinated groups had significantly reduced pathological changes or bacterial counts when compared to the non-vaccinated group. In Study 2, oral administration of Danish BCG induced protection against challenge with M. bovis, which persisted for at least 54 weeks after vaccination. Some protection was observed in possums challenged 54 weeks after vaccination, but this protection was significantly less than that observed in groups vaccinated 29 or 8 weeks prior to challenge. There was a strong relationship between the proportion of animals producing positive lymphocyte proliferation responses to M. bovis antigens and protection against challenge with M. bovis.

CONCLUSIONS

Factors considered potentially capable of interfering with vaccination, including feeding dead BCG to possums prior to feeding live BCG, feeding multiple doses of BCG at one time, and changing strains of BCG, were shown not to interfere with the acquisition of protective immune responses in possums. Protection against tuberculosis was undiminished up to 29 weeks after vaccination with BCG administered orally. It is concluded that vaccination of possums by feeding pellets containing BCG is a robust and efficient approach to enhance the resistance of these animals to tuberculosis.

Immunoglobulin G1 enzyme-linked immunosorbent assay for diagnosis of Johne's Disease in red deer (Cervus elaphus)

This study was designed to develop a customized enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of Johne's disease (JD) in farmed deer. Two antigens were selected on the basis of their superior diagnostic readouts: denatured purified protein derivative (PPDj) and undenatured protoplasmic antigen (PpAg). ELISA development was based on the antigen reactivity of the immunoglobulin G1 (IgG1) isotype, which is a highly specific marker for mycobacterial disease seroreactivity in deer. Sensitivity estimates and test parameters were established using 102 Mycobacterium paratuberculosis-infected animals from more than 10 deer herds, and specificity estimates were determined using 508 uninfected animals from 5 known disease-free herds. A receiver-operated characteristic analysis determined that at a cut point of 50 ELISA units, there was a specificity of 99.5% and sensitivities of 84.0% with PPDj antigen, 88.0% with PpAg, and 91.0% when the antigens were used serially in a composite test. Estimated sensitivity was further improved using recombinant protein antigens unique for M. paratuberculosis, which identified infected animals that were unreactive to PPDj or PpAg. While 80% of animals that were seropositive in the IgG1 ELISA had detectable histopathology, the assay could also detect animals with subclinical disease. The test was significantly less sensitive (75%) for animals that were culture positive for M. paratuberculosis but with no detectable pathology than for those with pathological evidence of JD (>90%). When the IgG1 ELISA was used annually over a 4-year period in a deer herd with high levels of clinical JD, it eliminated clinical disease, increased production levels, and reduced JD-related mortality.

Factors influencing the protective efficacy of a BCG homologous prime-boost vaccination regime against tuberculosis

Tuberculosis due to Mycobacterium spp. continues to represent a major threat to human and animal health, prompting the search for effective vaccines. We have previously reported a sequential prime and boost homologous vaccination regime, using live avirulent M. bovis bacille Calmette-Guerin (BCG) strain 1173P2, that can provide significant protection to red deer (Cervus elaphus) against virulent M. bovis infection. Here, we have investigated the influence of varying the time-periods during and following the vaccination regime on the subsequent outcome of disease following post-vaccination pathogen challenge. Deer vaccinated using the standard regime of BCG-prime (week 0) and BCG-boost (week 8) followed by M. bovis challenge (week 14-16) were highly protected, showing significant reductions in the incidence of M. bovis infection and tuberculous lesions, as well as reduced pathogen burdens in sentinel lymphatic tissues. Decreasing the time-period between primary and secondary immunisations from 8 to 4 weeks had no significant impact on the protective efficacy afforded by BCG vaccination, while increasing this period to 43 weeks largely ablated protection. Increasing the time-period between secondary immunisation and M. bovis challenge from 6 to 26 or 52 weeks also had no significant impact on protection, suggesting that an appropriately timed BCG prime-boost vaccination regime can establish long-lasting protective immunological memory in deer. Finally, increasing the time-period between virulent M. bovis challenge and the subsequent post-mortem examination of disease outcome indicated that - once vaccinated by the standard prime-boost regime - deer remain refractory to disease if challenged and maintained for up to 52 weeks, suggesting that vaccinated animals harbouring low numbers of virulent M. bovis organisms do not succumb to disease activation over time. These findings are discussed in relation to concurrent measurements of in vivo and ex vivo immunological markers of disease and protection, as well as the wider implications of a standardised vaccine regimen for practical use in animal health.

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.

Manipulation of immune responses to Mycobacterium bovis by vaccination with IL-2- and IL-18-secreting recombinant bacillus Calmette Guerin

Bacillus Calmette Guerin (BCG) has been reported to show variable efficacy as a vaccine against tuberculosis. We demonstrated that the secretion of biologically active IL-2 (rBCG/IL-2),but not IL-18 (rBCG/IL-18), by BCG improves its ability to induce and maintain a strong type 1 immune response in BALB/c mice. rBCG/IL-2 induced significantly higher Ag-specific proliferative responses, high IFN-gamma production and serum titres of IgG2a 16 weeks after vaccination. This immune profile was correlated to an increased rate of clearance of non-pathogenic mycobacteria (live BCG delivered intranasally). Surprisingly, however,this strong type 1 immune profile induced no greater protective immunity against aerosol challenge with virulent Mycobacterium bovis than that induced by normal BCG (nBCG). By comparison,vaccination with rBCG/IL-18 was found to induce significantly less IFN-gamma production in splenic lymphocytes than nBCG. This impaired induction of IFN-gamma was correlated to a significantly lower protective efficacy against M. bovis challenge, as compared to nBCG. The data suggest that manipulation of the immune response to tuberculosis and tuberculosis vaccines will require a more complete understanding of the factors that are important in generating a protective immune response.

Proteasome inhibitor MG-132 enhances the expression of interleukin-6 in human umbilical vein endothelial cells: Involvement of MAP/ERK kinase

Interleukin-6 (IL-6) is a multifunctional cytokine that plays an important role in inflammatory reactions. We have addressed the possible regulation of IL-6 expression by the ubiquitin-protease system in human umbilical vein endothelial cells. Cultured endothelial cells were treated with MG-132, a protease inhibitor, and the levels of IL-6 mRNA and protein were measured by reverse transcription-PCR and ELISA. MG-132 increased the expression of IL-6 mRNA and protein;and this effect was abolished by the pretreatment of the cells with U0126, an inhibitor of MAP or ERK kinases (MEK 1/2). MG-132 treatment was also found to enhance the level of phosphorylated MEK 1/2. Treatment of the cells with actinomycin D inhibited IL-6 expression in response to MG-132, suggesting the transcriptional upregulation of IL-6 under proteasomal inhibition. We conclude that a protease inhibitor MG-132 upregulates IL-6 expression in vascular endothelial cells, at least in part, through the activation of MEK 1/2.

Th1/Th2 biasing effects of vaccination in cattle as determined by real-time PCR

Real-time polymerase chain reaction (PCR) is now becoming an accepted tool for measuring gene expression at the transcriptional level. In this study, a direct comparison between real-time PCR, enzyme-linked immunosorbent assay (ELISA) and enzyme-linked immunosorbent spot (ELISPOT) assay was performed. When interferon-gamma (IFN-gamma) gene expression was assessed, both ELISA and ELISPOT data strongly correlated to results obtained by real-time PCR. Real-time PCR was subsequently used to measure bovine IFN-gamma (bIFN-gamma) and bovine interleukin-4 (bIL-4) gene expression by antigen stimulated peripheral blood mononuclear cells (PBMC), isolated from bovine herpesvirus-1 (BHV-1) infected animals. BHV-1-infected animals were either non-vaccinated or vaccinated using one of two adjuvants prior to infection. With non-vaccinated infected animals, a Th1 bias occurred, based on IFN-gamma expression exceeding IL-4 expression. The level of cytokine expression, and the IFN-gamma/IL-4 ratio could be significantly affected, depending on the manner in which animals were vaccinated.

Control of Mycobacterium bovis infections and the risk to human populations

Conventional control methods based on test-and-slaughter policies have, in several countries, led to the successful eradication of bovine tuberculosis in cattle. However, new approaches for control of bovine tuberculosis are required in developing countries and those with a wildlife reservoir of infection. Recent developments include improved diagnostics and evaluation of new vaccination strategies.

Optimal models to evaluate the protective efficacy of tuberculosis vaccines

BCG has been used widely as a vaccine to prevent tuberculosis (TB) for 80 years, yet there is still considerable controversy about its efficacy. Many experimental variables have obscured the true efficacy of BCG. The absence of appropriate animal models for the study of protective efficacy and the lack of in vitro correlates of protective immunity have impeded progress. Laboratory animal studies, which have contributed to understanding the pathogenesis, heritability of resistance and immunology of TB, have failed to identify the immunological pathways necessary for protective immunity. In recent years, cattle and deer, which are naturally susceptible to TB, have been used to study protective immunity in vaccinated animals, challenged with virulent bacteria. A deer TB infection model has been developed that can measure protection against TB infection or the development of disease. Data from this model show that, providing live BCG is administered in a short interval prime-boost protocol, significant protection against infection and disease can be obtained. Single dose vaccine provides suboptimal protection that attenuates pathology but does not prevent infection. Low dose BCG vaccine (10(4)cfu), administered in a prime-boost protocol, sufficient to prevent infection, does not cause conversion to delayed type hypersensitivity or produce unacceptable side-effects. Immune memory for protection against infection persists at optimal levels for at least 12 months post vaccination. Used optimally, BCG produces good levels of protection against TB and improved protocols or its use should be explored, before attempts are made to replace it with new-generation vaccines. It is now possible to integrate the fundamental information obtained from laboratory animals with studies of functional immune protection in target host species. Justification for the use of TB vaccines for domestic livestock under field conditions, must be underpinned by scientific evidence that they provide acceptable levels of protection long term.

IL-4 is required for defense against mycobacterial infection

Although the involvement of T helper (Th1) cells is central to protection against intracellular bacteria, including Mycobacterium tuberculosis, the involvement of Th2 cells, characterized by potent interleukin (IL)-4 secretion in mycobacterial infection is still unclear. In order to clarify the role of IL-4 in murine tuberculosis, IL-4-deficient mutant mice, IL-4 knockout (IL-4 KO) mice, were utilized. The mice were infected with H37Rv, Kurono or BCG Pasteur via an airborne infection route by placing them in the exposure chamber of a Middlebrook airborne infection apparatus. Their capacity to control mycobacterial growth, granuloma formation, cytokine secretion, and nitric oxide (NO) production were examined. These mice developed large granulomas, but not necrotic lesions in the lungs, liver or spleen (P<0.05). This was consistent with a significant increase in lung colony-forming units (CFU). Compared with levels in wild-type mice, upon stimulation with mycobacteria, splenic IL-10 levels were low and IL-6 levels were intermediate, but interferon (IFN)-gamma and IL-12 levels were significantly higher. IL-18 levels were within the normal range. The level of NO production by alveolar macrophages of the IL-4 KO mice was similar to that of the wild-type mice. Granulomatous lesion development by IL-4 KO mice was inhibited significantly by treatment with exogenous recombinant IL-4. These findings were not specific to the IL-4 KO mice used. Our data show that IL-4 may play a protective role in defense against mycobacteria, although IFN-gamma and TNF-alpha play major roles in it. Our data do not rule out an IFN-gamma-independent function of IL-4 in controlling tuberculosis.

Tuberculosis in deer: perceptions, problems and progress

Since the emergence of deer farming as an alternative farming enterprise over the past 30 years, there has been an increasing awareness of the potential threat posed by tuberculosis (TB) to domesticated deer. TB, caused by Mycobacterium bovis, has been found in deer in every country involved with deer farming. Different types of TB control policies, which vary from whole-herd depopulation to selective testing and slaughter of reactor animals, have been implemented. Extensive research has been carried out, incorporating modern microbiological and immunological concepts and advanced molecular methodologies, to find new solutions for the eradication of TB from domesticated deer. This work has resulted in valuable new insights into the aetiology, transmission, pathogenesis, diagnosis, prevention and heritability of resistance to M. bovis infection in ruminants. This knowledge has complemented the existing literature database on bovine and human TB and will provide new strategies for improved diagnosis, vaccination and selective breeding to control TB, which should be relevant for human, domestic livestock and wildlife populations.

The characterisation of a cervine immunoregulatory cytokine, interleukin 12

The cloning, sequencing, and production of cervine interleukin-12 is described. The cervine IL-12 p35 subunit coding sequence is 666 bp long and has highest homology to bovine p35 (94%), followed by human (79%), then murine (57%). The cDNA codes for a 221 aa long protein with predicted molecular weight of 24,902 Da. The cervine p40 subunit has a coding sequence of 984 bp and shows 96% homology to bovine, 85% homology to human, and 65% homology to murine p40 respectively. Cervine p40 cDNA codes for a 327 aa long protein with a predicted molecular weight of 37,461. Both subunits were inserted into a recombinant baculovirus that was then used to produce cervine IL-12 in Trichoplusia ni cells. Interleukin-12 was secreted into the culture medium and was biologically active as measured by proliferation of mitogen sensitised peripheral blood lymphocytes and the induction of interferon-gamma transcription in peripheral blood lymphocytes.

Veterinary tuberculosis vaccine development

Tuberculosis caused by Mycobacterium bovis in domestic livestock and wildlife is a significant problem in many countries worldwide. Wildlife reservoirs of tuberculosis confound programs for tuberculosis eradication from domestic livestock. Successful vaccination against tuberculosis in domestic animals or wildlife could contribute to tuberculosis eradication. Bacille Calmette-Guérin (BCG) has been used as the prototype vaccine for domestic livestock and wildlife. The majority of studies have been carried out with BCG-vaccinated animals challenged experimentally with M. bovis. Although protection against disease has been evident in all these studies, protection against infection has rarely occurred. Results obtained with BCG vaccination of cattle, deer, ferrets, opossums, and rabbits are presented here and highlight the need for appropriate animal models for vaccination and control of the variables that influence the efficacy of BCG vaccine. Refinement of the existing animal models is essential for the advancement of tuberculosis vaccine research of relevance to animals and humans.

IFN-gamma, IL-4, IL-10 and IL-12 gene expression in BCG-Leishmania vaccination of Trypanosoma cruzi-infected mice

We have previously shown that vaccination of BALB/c mice with a combination of BCG plus killed Leishmania promastigotes, applied by the i.p. route 10 and 3 days before Trypanosoma cruzi inoculation, prolonged their survival and decreased their parasitaemia. In the present study we show that the BCG-Leishmania vaccine induced higher levels of circulating IFN-gamma in acute and chronic infection of mice [on day 25 and 40 post-infection (p.i.) respectively], in comparison to unvaccinated animals (PBS-treated). Though the IFN-gamma mRNA content of spleen cells of vaccinated and infected mice (on day 25 p.i.) was similar to that of unvaccinated animals, the BCG-Leishmania vaccine enhanced significantly the production of IFN-gamma by spleen cells stimulated with T. cruzi antigens. This effect was observed to a lower extent in BCG- and Leishmania-treated mice. The BCG-Leishmania vaccine reduced the expression of the IL-10 mRNA of splenocytes as soon as day 12 p.i., before the peak parasitaemia. Such this effect was not observed in BCG- or Leishmania-treated animals. On day 25 p.i., the BCG plus Leishmania- or BCG-treatment of mice abolished the capacity of spleen cells to produce IL-10 in response to T. cruzi antigens. The levels of mIL-4 RNA and protein production were not modified in any group of mice. T. cruzi infection in BCG-Leishmania-vaccined mice stimulated an early and high production of IL-12 transcripts in spleen cells during the acute phase of the infection, that was prolonged during the chronic phase of infection. This effect was weaker or absent in BCG- and Leishmania-treated animals, respectively. These results indicate that the BCG-Leishmania vaccine stimulates the production of IL-12 and IFN-gamma, but inhibits that of IL-10 and is without effect on IL-4 when mice are infected with T. cruzi. This highlights the key role of endogenously produced IFN-gamma, IL-10 and IL-12 in the control of T. cruzi acute and chronic infection in mice and the favorable modulation of their balance by a vaccination combining BCG and Leishmania.

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.

An in vivo comparison of bacillus Calmette-Guérin (BCG) and cytokine-secreting BCG vaccines

A recombinant bacillus Calmette-Guérin (BCG) vaccine has been developed, which constitutively secretes interleukin (IL)-2. Groups of deer were immunized with either normal BCG (Pasteur 1173 P2 strain) or recombinant BCG (rBCG/IL-2) and their immune responses were monitored over 3 months. Animals gained weight over this period and showed no signs of adverse reactions to either vaccine. Lymphocyte transformation responses did not differ significantly between the two groups. No antibody that was specific for BCG was detected in any animal. Intradermal skin-test responses to BCG antigens showed that the rBCG/IL-2 induced a smaller delayed-type hypersensitivity response than the normal BCG. Cytokine transcription was determined by reverse transcription-polymerase chain reaction (RT-PCR). While IL-2 and interferon-gamma (IFN-gamma) levels did not differ significantly between the two groups, the level of IL-4 was found to be lower in the group given rBCG/IL-2. This resulted in a strong interferon-gamma:IL-4 ratio, suggesting a skewing of the immune response towards a Type 1 response. The rate at which the vaccine was eliminated from the host was the same regardless of whether BCG or rBCG was used. At autopsy (3 months after vaccination) 99.99% of the organisms had been eliminated. The small number of organisms isolated from the draining lymph node of animals given rBCG/IL-2 were grown in antibiotic-containing media. They were shown to still contain the shuttle plasmid and to secrete biologically active IL-2, indicating that the plasmid was stably maintained despite the host's immune response and in the absence of antibiotic selection.

Farmed deer: a large animal model for stress

In the early classic period it was suggested by Heracleitus that a static unchanged state was not the natural condition, but rather that the capacity to undergo constant change was intrinsic to all living things. After that, Empedoeles, circa 500 BC, proposed that for living organisms to survive they require a harmonious mixture of elements. Hippocrates, around 400 BC, developed this concept further by suggesting that health is a state of harmonious balance of these elements, equating disease to a state of disharmony and introducing the concept that nature heals disease (Noysvn Fyseiw/atrui). Soon after, Epicurus extended these ideas to include among these healing forces, the mind, writing that imperturbability of mind is desirable. Claude Bernard introduced the concept of the milieu interieur or the internal physiologic environment, describing its constancy as essential in an external environment typified by its variability. Walter Cannon described Bernard's constancy as Homeostasis and identified the "fight or flight reflex," linking the adaptive response and catecholamine secretion, with extreme levels of activation-producing pathology. Selye outlined four stages of the stress response: 1) the "alarm reaction" characterized by an immediate activation of the sympathetic-adrenomedullary axis (SA); 2) a "resistance phase" characterized by hypothalamic pituitary-adrenal axis (HPA) activation; 3) a stage of adrenal hypertrophy, gastrointestinal ulceration, along with thymic and lymphoid atrophy; and 4) an exhaustion phase and finally death (1).