Ferroelasticity, anelasticity and magnetoelastic relaxation in Co-doped iron pnictide: Ba(Fe0.957Co0.043)2As2.

The hypothesis that strain has a permeating influence on ferroelastic, magnetic and superconducting transitions in 122 iron pnictides has been tested by investigating variations of the elastic and anelastic properties of a single crystal of Ba(Fe0.957Co0.043)2As2 by resonant ultrasound spectroscopy as a function of temperature and externally applied magnetic field. Non-linear softening and stiffening of C 66 in the stability fields of both the tetragonal and orthorhombic structures has been found to conform quantitatively to the Landau expansion for a pseudoproper ferroelastic transition which is second order in character. The only exception is that the transition occurs at a temperature (T S ≈ 69 K) ~10 K above the temperature at which C 66 would extrapolate to zero ([Formula: see text] ≈ 59 K). An absence of anomalies associated with antiferromagnetic ordering below T N ≈ 60 K implies that coupling of the magnetic order parameter with shear strain is weak. It is concluded that linear-quadratic coupling between the structural/electronic and antiferromagnetic order parameters is suppressed due to the effects of local heterogeneous strain fields arising from the substitution of Fe by Co. An acoustic loss peak at ~50-55 K is attributed to the influence of mobile ferroelastic twin walls that become pinned by a thermally activated process involving polaronic defects. Softening of C 66 by up to ~6% below the normal-superconducting transition at T c ≈ 13 K demonstrates an effective coupling of the shear strain with the order parameter for the superconducting transition which arises indirectly as a consequence of unfavourable coupling of the superconducting order parameter with the ferroelastic order parameter. Ba(Fe0.957Co0.043)2As2 is representative of 122 pnictides as forming a class of multiferroic superconductors in which elastic strain relaxations underpin almost all aspects of coupling between the structural, magnetic and superconducting order parameters and of dynamic properties of the transformation microstructures they contain.

Elastic anomalies associated with structural and magnetic phase transitions in single crystal hexagonal YMnO3.

Resonant ultrasound spectroscopy has been used to measure the elastic and anelastic behaviour through known structural and magnetic phase transitions in single crystal hexagonal YMnO3. Anomalous elastic behaviour is observed at the high temperature structural transition at ∼1260 K, with a discontinuity in the elastic constants and nonlinear recovery below Tc, consistent with [Formula: see text] coupling. There is no change in dissipation associated with this high temperature transition, and no evidence in the elastic or anelastic behaviour for any secondary transition at ∼920 K, thus supporting the thesis of a single high temperature transformation. Elastic stiffening is observed on cooling through TN, in accordance with previous studies, and the excess elastic constant appears to scale with the square of the magnetic order parameter. The strains incurred at TN are a factor of ∼20 smaller than those at the structural transition, implying very weak [Formula: see text] coupling and a dominant contribution to the variation in the elastic constants from [Formula: see text]. The increased acoustic dissipation above TN is consistent with an order-disorder process.

Multiferroic (ferroelastic/ferromagnetic/ferrimagnetic) aspects of phase transitions in RCo2 Laves phases.

Magnetic phase transitions in RCo2 Laves phases with R as a rare earth element are accompanied by changes in crystallographic space group. For purely structural transitions they would be described as improper ferroelastic and therefore fulfil the condition for multiferroic phase transitions in combining two out of three properties, ferro/antiferromagnetism, ferroelectricity and ferroelasticity. Here lattice parameter data from the literature and new measurements of elastic and anelastic properties, by resonant ultrasound spectroscopy, for NdCo2 and ErCo2 have been analysed from this perspective. The temperature dependence of symmetry-breaking shear strains is consistent with the cubic ↔ tetragonal transition in NdCo2 being close to tricritical in character and the cubic ↔ rhombohedral transition in ErCo2 being first order. Elastic softening and acoustic loss within the stability ranges of the ferroelastic phases can be understood in terms of a combination of intrinsic softening due to strain/order parameter coupling and ferroelastic twin-wall motion. Softening ahead of the transitions does not fit with standard macroscopic descriptions of dynamic effects from other systems but, rather, in the case of NdCo2, might be attributed to the involvement of a second zone centre order parameter related to a separate instability driven by cooperative Jahn-Teller distortions. In ErCo2, acoustic loss in the temperature interval above the transition point is discussed in terms of a possible tweed microstructure associated with strain coupling to local magnetic ordering. The overall multiferroic behaviour can be understood in terms of a single magnetic order parameter (irrep mΓ+4 of magnetic space group Fd3m1') which couples with a structural order parameter (irrep Γ+3 or Γ+5). The coupling is linear/quadratic which, in the case of two separate instabilities, causes them to combine in a single multiferroic phase transition.

Migratory sub-populations of afferent lymphatic dendritic cells differ in their interactions with Mycobacterium bovis Bacille Calmette Guerin.

Understanding how pathogens or vaccine antigens are targeted to dendritic cell (DC) subsets is important for disease pathogenesis studies and vaccine design. We characterised the sub-populations of migrating bovine DC with functional and phenotypic diversity present in pseudoafferent lymph draining the skin. These skin draining DC exist as a series of maturation dependent subsets with differential capacities for antigen uptake and cytokine expression, and include both Langerhans' cells (LC) and dermal derived cells. Furthermore, Mycobacterium bovis Bacille Calmette Guerin, a vaccine which is administered by the intradermal route, was only taken up by a small number of the migrating DC, which were SIRPα(+) and expressed the mannose receptor and CD1b. This was evident following in vitro infection and also in vivo following inoculation of green fluorescent BCG over the lymphatic cannulation site. Only the SIRPα(+) DC were able to present antigen to T cells isolated from BCG vaccinated calves. Furthermore, presentation of BCG antigens by DC to T lymphocytes was ineffective compared to mycobacterial proteins. However, mycobacterial antigen 85 was delivered more effectively to DC via an adenoviral vector and the magnitude of the subsequent antigen-specific T cell response was significantly increased. This study further extends our understanding of the biology of migrating DC, identifies potential explanations for the modest success of BCG vaccination and demonstrates that targeted delivery of antigens via adenoviruses to DC can improve antigen presentation.

Elastic and anelastic relaxations in the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3: I. Strain analysis and a static order parameter.

The structural evolution of Pb(Mg(1/3)Nb(2/3))O(3) (PMN) has been reviewed in terms of characteristic temperatures, length scales and timescales, with a view to considering the overall relaxor behaviour from the perspectives of strain and elasticity. A conventional analysis of lattice parameter data in terms of spontaneous strain and strain/order parameter coupling shows that even though a normal phase transition does not occur the relaxor ordering process is accompanied by a significant volume strain which follows the pattern of a static order parameter evolving according to that expected for a tricritical phase transition with T(c) ≈ 350 K. This matches the evolution of the intensity of the elastic central peak in neutron scattering spectra, and reflects the development of static (or quasistatic) polar nanoregions (PNRs) as if by a mean-field phase transition. Use of a Landau free energy expansion, which includes Γ4(-) order parameter components to describe ferroelectric contributions and an R1(+) order parameter to describe cation ordering together with their formal coupling with strain, then allows the pattern of elastic softening expected for a cubic → rhombohedral phase transition to be anticipated. The extent to which observed softening differs from this static mean-field pattern serves to highlight the additional roles of local heterogeneity and relaxation dynamics in determining the relaxor properties of PMN.

Elastic anomalies associated with transformation sequences in perovskites: I. Strontium zirconate, SrZrO(3).

Elastic behaviour associated with the hierarchy of tilting transitions in SrZrO(3) has been examined using resonant ultrasound spectroscopy on a ceramic sample at temperatures between 153 and 1531 K. Changes in slope of the evolution of resonance frequencies with temperature indicate that phase transitions occur at 1038 K ([Formula: see text]), 1122 K ([Formula: see text]), and 1367 K ([Formula: see text]). Strain analysis of previously recorded neutron diffraction data shows that the [Formula: see text] and [Formula: see text] transitions are close to tricritical in character, and that [Formula: see text] is first order. Deviations from the form of the elastic behaviour predicted by Landau theory are found. In particular, elastic softening in the vicinity of the [Formula: see text] transition suggests that local dynamical fluctuations between individual tilt systems occur, rather than a discontinuous switch from one phase to another. Determinations of the mechanical quality factor, Q, show that SrZrO(3) in the [Formula: see text] phase is a classically high-Q (i.e. non-dissipating) cubic material. I4/mcm and Imma phases both have much greater dissipation (low Q), which is tentatively attributed to the mobility of twin walls. The room temperature Pnma phase is unexpectedly much stiffer than both I4/mcm and Imma phases and has high Q. It appears that when two separate tilt systems operate, as in Pnma, they can interact to reduce strain/order parameter relaxations.

Development of a simple, sensitive, rapid test which discriminates BCG-vaccinated from Mycobacterium bovis-infected cattle.

Bovine tuberculosis (bTB) is increasing in incidence in the UK. Effective control strategies could involve vaccination; BCG, either alone or in prime-boost strategies, remains the most effective vaccine against bovine tuberculosis. However, BCG vaccination of cattle would require development of diagnostic tests able to accurately discriminate Mycobacterium bovis-infected from BCG-vaccinated animals. Herein, we demonstrate that the detection of secreted IFN-gamma following short term culture (4h) of whole blood with purified protein derived from M. bovis (PPD-B) allows such discrimination. This reflects, in part, the differential kinetics of IFN-gamma secretion in infected compared to vaccinated cattle. This is the first study to demonstrate that accurate, rapid distinction of BCG-vaccinated from M. bovis-infected cattle can be achieved in a short time period without the need for production of M. bovis-specific antigens, complex antigen mixtures or extensive laboratory procedures. We were also able to detect PPD-specific IFN-gamma release during short term culture of blood from a number of humans with active TB indicating that this test may have wider application and is potentially useful for the rapid diagnosis of disease in humans.

Antigen-specific peripheral immune responses are unaltered during normal pregnancy in sheep.

A shift in the balance of T(Helper) (T(H))1/T(H)2 cytokine production by maternal peripheral blood leukocytes is regarded as a common important feature of successful mammalian pregnancy. Although the phenomenon has been studied extensively in animals with invasive hemochorial placentae, the paradigm has not been studied in detail in species with less-invasive placentae, such as sheep that have a synepitheliochorial placenta. Sixteen sheep were immunised with the nominal antigen chicken egg albumin (Ova) and antigen-specific humoral and cellular responses were established in all sheep. The 16 sheep were synchronised, 11 were mated and successfully conceived, the remaining 5 served as non-pregnant controls. Peripheral blood mononuclear cells (PBMC) were isolated approximately every 2 weeks and restimulated in vitro with either Ova or the T cell mitogen concanavalin A (ConA), and cell proliferation and cytokine production measured. There were no detectable differences in antigen-driven PBMC proliferation, interferon-gamma (IFN-gamma), interleukin (IL)-4 or IL-10 production between pregnant and non-pregnant sheep. Also, there were no appreciable differences in ConA-induced IFN-gamma, IL-4 or IL-10 between the groups. These data suggest that a shift in T(H)1/T(H)2 cytokine production does not occur in pregnant sheep and indicate that further comparative reproductive immunology studies on species with non-invasive placentation will be informative of materno-fetal interactions and immune regulation during pregnancy.

Mycobacterium bovis shedding patterns from experimentally infected calves and the effect of concurrent infection with bovine viral diarrhoea virus.

Concurrent infection of cattle with bovine viral diarrhoea virus (BVDV) and Mycobacterium bovis is considered to be a possible risk factor for onward transmission of bovine tuberculosis (BTB) in infected cattle and is known to compromise diagnostic tests. A comparison is made here of M. bovis shedding (i.e. release) characteristics from 12 calves, six experimentally co-infected with BVDV and six infected with M. bovis alone, using simple models of bacterial replication. These statistical and mathematical models account for the intermittent or episodic nature of shedding, the dynamics of within-host bacterial proliferation and the sampling distribution from a given shedding episode. We show that while there are distinct differences among the shedding patterns of calves given the same infecting dose, there is no statistically significant difference between the two groups of calves. Such differences as there are, can be explained solely in terms of the shedding frequency, but with all calves potentially excreting the same amount of bacteria in a given shedding episode post-infection. The model can be thought of as a process of the bacteria becoming established in a number of discrete foci of colonization, rather than as a more generalized infection of the respiratory tract. In this case, the variability in the shedding patterns of the infected calves can be explained solely by differences in the number of foci established and shedding being from individual foci over time. Should maximum exposure on a particular occasion be a critical consideration for cattle-to-cattle transmission of BTB, cattle that shed only intermittently may still make an important contribution to the spread and persistence of the disease.

Influence of the nature of the antigen on the boosting of responses to mycobacteria in M. bovis-BCG vaccinated cattle.

Mycobacterium bovis is the causative agent of bovine tuberculosis (TB) and of a proportion of human TB. Protection against TB requires Th1 responses and worsening of disease is associated with Th2 responses. To help clarify the nature of the response to mycobacteria, the responses from M. bovis-BCG vaccinated cattle boosted with live mycobacteria (BCG), bacterial soluble antigens (PPD) or PBS were evaluated. The results indicated that macrophages may be the major cell population ingesting and presenting mycobacteria in BCG boosted animals, while B-cells seem able to ingest and present PPD to T-cells in PPD boosted animals.

Flow cytometric detection of gamma interferon can effectively discriminate Mycobacterium bovis BCG-vaccinated cattle from M. bovis-infected cattle.

Mycobacterium bovis is the causative agent of bovine tuberculosis, a disease that is increasing in incidence in United Kingdom cattle herds. In addition to increasing economic losses, the rise in bovine tuberculosis poses a human health risk. There is an urgent requirement for effective strategies for disease eradication; this will likely involve vaccination in conjunction with current test and slaughter policies. A policy involving vaccination would require an accurate diagnosis of M. bovis-infected animals and the potential to distinguish these animals from vaccinates. Currently used diagnostic tests, the skin test and gamma interferon (IFN-gamma) blood test, have a sensitivity of up to 95%. A further complication is that M. bovis BCG-vaccinated animals are also scored positive by these tests. We tested the hypothesis that the quantification of IFN-gamma-producing lymphocytes by flow cytometric analysis of intracellular IFN-gamma expression would provide a more accurate discrimination of M. bovis-infected animals from BCG vaccinates. Significant numbers of IFN-gamma-expressing CD4+ T cells were detected following culture of heparinized blood from M. bovis-infected animals, but not from BCG vaccinates, with purified protein derived from M. bovis (PPD-B) or live mycobacteria. Only 1 of 17 BCG-vaccinated animals had a significant number of CD4+ T lymphocytes expressing IFN-gamma, compared with 21/22 M. bovis-infected animals. This assay could allow an accurate diagnosis of M. bovis and allow the discrimination of BCG-vaccinated cattle from infected cattle.

Single-cell analysis divides bovine monocyte-derived dendritic cells into subsets expressing either high or low levels of inducible nitric oxide synthase.

Dendritic cells (DC) are important cells at the interface between innate and adaptive immunity. DC have a key role in antigen processing and presentation to T cells. Effector functions of DC related to innate immunity have not been explored extensively. We show that bovine monocyte-derived DC (mDC) express inducible nitric oxide synthase (iNOS) mRNA and protein and produce NO upon triggering with interferon-gamma (IFN-gamma) and heat-killed Listeria monocytogenes (HKLM). An immunocytochemical analysis revealed that a sizeable subset (20-60%) copiously expresses iNOS (iNOShi) upon IFN-gamma/HKLM triggering, whereas the other subset expressed low levels of iNOS (iNOSlo). Monocyte-derived macrophages (mMphi) are more homogeneous with regard to iNOS expression. The number of cells within the iNOSlo mDC subset is considerably larger than the number of dead cells or cells unresponsive to IFN-gamma/HKLM. The large majority of cells translocated p65 to the nucleus upon triggering by IFN-gamma/HKLM. A contamination of mDC with iNOS-expressing mMphi was excluded as follows. (i) Cell surface marker analysis suggested that mDC were relatively homogeneous, and no evidence for a contaminating subset expressing macrophage markers (e.g. high levels of CD14) was obtained. (ii) iNOS expression was stronger in iNOShi mDC than in mMphi. The use of maturation-promoting stimuli revealed only subtle phenotypic differences between immature and mature DC in cattle. Nevertheless, these stimuli promoted development of considerably fewer iNOShi mDC upon triggering with IFN-gamma/HKLM. Immunocytochemical results showed that although a significant proportion of cells expressed iNOS only or TNF only upon triggering with IFN-gamma/HKLM, a significant number of cells expressed both iNOS and TNF, suggesting that TNF and iNOS producing (TIP) DC are present within bovine mDC populations obtained in vitro.

The effect of tuberculin testing on the development of cell-mediated immune responses during Mycobacterium bovis infection.

Protection against tuberculosis (TB) is associated with Th1-type cell-mediated immunity (CMI). Whilst the intradermal injection of partially purified derivatives of tuberculin (PPD) represents the classic test assessing the delayed type hypersensitivity (DTH) response used in both humans and cattle for diagnosing TB, it has been suggested that the test may modulate host CMI responses. To investigate the kinetics of the development of the DTH response and its subsequent effect on CMI responses, groups of 6-month old calves were inoculated intranasally with 8 x 10(4) cfu of Mycobacterium bovis, subjected to the comparative intradermal tuberculin test (TT) using bovine and avian PPD (PPD-B, PPD-A) at various time intervals post-infection, and immune responses compared. These included DTH, lymphocyte proliferation, IgG production, and synthesis of the cytokines: IFNgamma, IL-10, IL-4, IL-6, and IL-13. All animals were subjected to post-mortem examination. The kinetics of the development of the DTH response assessed in the TT was such that infected cattle could be identified as early as 3 weeks post-infection, which correlated with the detection of an antigen-specific IFNgamma response. Transient increases in plasma-derived IFNgamma as a result of TT during an established TB infection were more pronounced when blood was stimulated with PPD-A compared with PPD-B stimulation. This has the potential to mask diagnosis of infection as a result of the stronger avian-bias if the IFNgamma test is used the week following TT. Disease pathology was not affected by TT. A transient failure to a second TT was observed in 1 of 30 animals and the time (post-infection) at which the TT is administered may be of significance. In serum, IgG responses to PPD-B, which were undetectable prior to TT, were elevated after TT and were most pronounced in cattle that were TT at 6 weeks post-infection. Other cytokines were also affected by the TT; IL-4 mRNA levels increased and IL-6 mRNA levels decreased, whilst PPD-B specific IL-10 protein synthesis was enhanced. These observations may offer the potential for further diagnostic assays that could complement the TT and IFNgamma test.

Cytokine expression profiles of bovine lymph nodes: effects of Mycobacterium bovis infection and bacille Calmette-Guérin vaccination.

Cytokine expression in lymph nodes from cattle inoculated intranasally with Mycobacterium bovis was compared to that of non-infected animals using real-time polymerase chain reaction. The effect of M. bovis infection, 4 months post-challenge, was to suppress the expression of anti-inflammatory cytokines interleukin (IL)-4 and IL-10 as well as the pro-inflammatory cytokines tumour necrosis factor (TNF) and IL-6. Expression of interferon (IFN)-gamma and IL-12 was maintained. Animals vaccinated with bacille Calmette-Guérin responded differently to challenge with M. bovis. In particular, no decrease in expression of IL-4 or IL-6 was observed following challenge of vaccinated animals and decreased IFN-gamma was detected. Also, vaccinated animals had higher levels of IL-4 and IL-10 transcripts compared to unvaccinated animals following challenge. These changes in cytokine expression levels led to a significant shift in the IFN-gamma/IL-4 or IFN-gamma/IL-10 ratio within the lymph node following challenge. Challenged animals generally showed a strong Th1 bias that was not seen in animals vaccinated prior to challenge. An inverse correlation between the level of pathology and bacterial load within the lymph node and the expression of IL-4, IL-10 and TNF was also observed. These results suggest that in the lymph nodes of cattle with established tuberculosis and a persisting bacterial infection, maintenance of the pro-inflammatory response in combination with a suppressed anti-inflammatory response may control the infection but contribute to host-induced tissue damage. Vaccination, which reduces the bacterial load and consequently the IFN-gamma response, may result in less suppression of anti-inflammatory cytokines.

Humoral and cellular immune responses to Fasciola gigantica experimental infection in buffaloes.

Humoral and cellular immune responses to Fasciola gigantica experimental infection in buffaloes were studied. The results showed that 33.4+/-9.1% of the infection dose was recovered as adult flukes from infected animals at necropsy. Significant differences of weight gain between infected and non-infected buffaloes was observed at 4 MPI (months post-infection). Anti F. gigantica excretory-secretory products (FgESP)-IgG levels increased significantly from 3 WPI (weeks post-infection) and displayed a peak at 13 WPI. Western blot indicated that in FgESP six major bands of 11.5, 19.0, 23.4, 29.8, 47.5 and 53.2kDa were recognized by F. gigantica-infected buffaloes sera after 0 WPI. Eosinophil numbers increased significantly from 3 WPI in F. gigantica-infected buffaloes and displayed a peak at 8 WPI. Peripheral blood mononuclear cells (PBMC) proliferation induced by FgESP increased from 2 WPI with a peak at 5 WPI. IFNgamma secretion by FgESP-stimulated PBMC appeared early from 1 WPI with three peaks at 2, 5 and 8 WPI, respectively. IL-10 production was observed from 2 WPI with two peaks at 4 and 9 WPI, respectively. Our results suggested that buffaloes were highly susceptible to F. gigantica infection, and this susceptibility could be associated with the late and weak cellular immune response in the early phase of infection and the Th0-like response throughout the infection.

Fasciola hepatica and Fasciola gigantica: comparison of cellular response to experimental infection in sheep.

Cellular responses to Fasciola gigantica and to Fasciola hepatica infection in sheep were compared. Eosinophil numbers increased more quickly and strongly in F. gigantica-infected sheep than in F. hepatica-infected sheep. In both groups, peripheral blood mononuclear cell (PBMC) proliferation in response to the parasitic excretory-secretory products (ESP) showed similar kinetics. Interferon-gamma (IFN-gamma) production by ESP-stimulated PBMC was early and showed similar kinetics in both groups. Interleukin-10 (IL-10) production by FhESP-stimulated PBMC was very high throughout infection even at 0 weeks post-infection (WPI) in F. hepatica-infected sheep, while in F. gigantica-infected sheep, IL-10 production by FgESP-stimulated PBMC increased between 1 and 4 WPI. IL-10 production in F. gigantica-infected sheep was significantly lower than in F. hepatica-infected sheep during infection. The lower susceptibility to F. gigantica infection in sheep could be explained by the more intense cellular response induced by the parasite and the weaker capacity of F. gigantica to evade the immune response.

Exposure to Mycobacterium avium induces low-level protection from Mycobacterium bovis infection but compromises diagnosis of disease in cattle.

We assessed the effect of exposure to Mycobacterium avium on the development of immune responses and the pathogenesis of disease observed following Mycobacterium bovis challenge. A degree of protection against M. bovis was observed in calves which were pre-exposed to M. avium as assessed by the extent of lesions and bacterial load compared to the M. bovis alone group. The immune response following M. bovis challenge in cattle previously inoculated with M. avium was biased towards antigens (PPD) present in M. avium, whereas the response following M. bovis alone was biased towards antigens present in M. bovis, indicating an imprinting of memory to avian antigens on T lymphocytes. A consequence of the memory to M. avium antigens was failure to diagnose M. bovis infection by the skin test or the IFN(gamma) assay in some of the animals which had lesions of tuberculosis at necropsy. The use of M. bovis specific antigens ESAT-6 and CFP-10 increased IFN(gamma) test specificity in animals previously exposed to M. avium but the responses to these antigens were lower than those observed in animals exposed to M. bovis alone. The implication is that responses to M. avium, although providing some immunity, may mask diagnosis of M. bovis infection, even when specific antigens are employed, potentially contributing to disease transmission in the field.

Development of detection methods for ruminant interleukin (IL)-4.

Recombinant bovine IL-4 (rbo IL-4) was transiently expressed in COS-7 cells. Mice were immunised with a plasmid encoding rbo IL-4 and boosted with rbo IL-4. A number of monoclonal antibodies (mAb) were generated that reacted with rbo IL-4 in an ELISA and these cloned hybridomas were termed CC311, CC312, CC313 and CC314. A pair of mAb (CC313 and CC314) was identified that together could be used to detect both recombinant and native bovine IL-4 by ELISA and a luminometric detection method was applied to the ELISA. Using this method native bovine IL-4 was detected in supernatants of PBMC stimulated with mitogens. In addition, high level secretion of IL-4 by Fasciola hepatica specific Th2 clones, but not by a Babesia bovis specific Th1 clone, was confirmed. The ELISA was also able to detect recombinant ovine IL-4. The pair of mAb used for ELISA could also be used for the detection of IL-4 spot forming cells by ELISPOT. In addition intracytoplasmic expression of IL-4 could be detected. The ability to detect ruminant IL-4 by three methods: ELISA, ELISPOT and by flow cytometric analysis of intracytoplasmic expression will permit studies of the role of this important cytokine in the immunology and pathogenesis of animal diseases.

Identification of a cell population that produces alpha/beta interferon in vitro and in vivo in response to noncytopathic bovine viral diarrhea virus.

In vitro infection of bovine cells of many origins with the cytopathogenic bovine viral diarrhea virus (cpBVDV) results in the induction of alpha/beta interferon (IFN-alpha/beta), whereas noncytopathogenic BVDV (ncpBVDV) isolates have been shown not to induce IFN-alpha/beta in vitro. Similarly, cpBVDV induces IFN-alpha/beta in the early bovine fetus, but ncpBVDV does not. However, acute infection of naive cattle with ncpBVDV results in IFN-alpha/beta production. In this study, we identified and characterized a minor population of cells, present in lymph nodes that produce IFN-alpha in response to ncpBVDV. These cells expressed the myeloid markers CD14, CD11b, and CD172a but did not express CD4 and CD45RB. We also established that these cells produced IFN-alpha in the absence of detectable productive infection.

Vaccination of neonatal calves with Mycobacterium bovis BCG induces protection against intranasal challenge with virulent M. bovis.

Vaccination of neonates with Mycobacterium bovis bacillus Calmette-Guerin (BCG) may be a strategy that overcomes reduced vaccine efficacy associated with exposure to environmental mycobacteria in humans and cattle. Preliminary comparisons indicated that 2-week-old calves produced an immune response to vaccination at least as intense as that observed in adults. Subsequently, five gnotobiotic hysterotomy derived calves aged 1 day were inoculated with BCG and 3 months later were challenged intranasally with virulent M. bovis. The number of tissues with lesions and the pathological extent of these lesions was reduced significantly in vaccinates. Furthermore, lesions were evident in the lung or associated chest lymph nodes of four of five controls but none of five vaccinates. BCG vaccination reduced significantly the level of bacterial colonization. However, lesions in the head associated lymph nodes were observed in three of five BCG-vaccinated cattle. Levels of interferon gamma (IFN-gamma) detected by enzyme-linked immunosorbent assay (ELISA) or enzyme-linked immunospot (ELISPOT) in individual vaccinated animals at challenge did not correlate with subsequent resistance and in general immune responses post-challenge were lower in vaccinated calves. Low IL-10 responses were evident but IL-4 was not detected. Responses to ESAT-6 and/or CFP-10 were evident in four of four control calves that had lesions. Two of the BCG vaccinates with lesions did not produce a response to ESAT-6 and CFP-10, indicating that these antigens did not distinguish vaccinated immune animals from vaccinated animals with lesions. Overall, vaccination of neonatal calves with BCG induced significant protection against disease and has potential as a strategy for the reduction of the incidence of bovine tuberculosis.