Stimulation of Bovine Whole-Blood Samples Cultured in Media Supplemented with Recombinant Interleukin-7 (IL-7) and IL-12 Extends the Life Span of the Gamma Interferon Assay To Detect Mycobacterium bovis-Infected Cattle.

The gamma interferon (IFN-γ) assay is widely used to measure cell-mediated immune (CMI) response for the early detection of tuberculosis infection. Processing whole-blood samples for CMI-based diagnostics is time sensitive and usually must occur within 8 h of collection to ensure optimal assay performance. In this study, we developed and tested a modified protocol, in which whole-blood samples from Mycobacterium bovis-infected cattle were diluted 1:1 in RPMI medium containing 0.3% fetal bovine serum (FBS) added or not to recombinant mouse interleukin-7 (rmIL-7) or rmIL-12, alone or in combination, and stored at 4°C. At 3 and 6 days postcollection, the diluted blood samples were adjusted to 10% FBS, dispensed into culture trays, stimulated with a bovine purified protein derivative from M. bovis, and incubated at 37°C in 5% CO2 in air. Plasma was removed and assayed for an IFN-γ response using bovine IFN-γ enzyme-linked immunosorbent assay (ELISA) (Bovigam). The results were then compared with those obtained from the conventional procedure. The IFN-γ responses of the samples stored up to 6 days postcollection in the supplemented RPMI medium were similar to those observed in the samples processed within 8 h after sampling, indicating that lymphocyte vitality and response were preserved. The addition of rmIL-7 and rmIL-12, alone or in combination, to culture medium can enhance lymphocyte survival and thus extends the time limit within which the IFN-γ assay can be applied as a diagnostic tool in bovine tuberculosis surveillance and eradication.

Evaluation of the interferon-gamma (IFN-γ) assay to diagnose Mycobacterium bovis infection in pigs.

Mycobacterium bovis recognizes as hosts a wide spectrum of animal species. In particular epidemiological situations, high prevalence of infection is found also in pigs. In the present study, we evaluated the capability of the interferon-gamma (IFN-γ) assay to identify pigs infected with M. bovis. The results of the immune-diagnosis were correlated to the findings of the post mortem inspection and the bacterial culture of lymph nodes. Blood samples of 146 pigs, belonging to a local breed of Sicily reared in free or semi-free roaming conditions, were collected to assess the specificity and the sensibility of the IFN-γ assay. Thirty-one pigs, from M. bovis free herds, did not react to the IFN-γ assay, yielding a specificity of 100%. The IFN-γ assay identified 15 out of 19 animals positive to the bacterial culture and 22 out of 26 animals with tuberculous lesions, with a sensibility of 78.9-84.6%, respectively. Out of 26 reactors to the test, 15 pigs (57.7%) confirmed to be infected after the bacterial culture and 22 (84.6%) had tuberculous lesions. The IFN-γ assay was able to reveal 4 animals with no visible lesions (NVL). Together, these findings support the feasible use of the IFN-γ assay as an intra vitam tool for the surveillance and management of M. bovis infection in swine populations.

Effects of nitrogen source and water availability on stem carbohydrates and cellulosic bioethanol traits of alfalfa plants.

Symbiotic association of legumes with rhizobia frequently results in higher photosynthesis and soluble carbohydrates in comparison with nitrate-fed plants, which might improve its potential for biomass conversion into bioethanol. A greenhouse experiment was conducted to examine the effects of nitrogen source and water availability on stem characteristics and on relationships between carbohydrates, phenolic metabolism activity and cell wall composition in alfalfa (Medicago sativa L. cv. Aragón). The experiment included three treatments: (1) plants fed with ammonium nitrate (AN); (2) plants inoculated with rhizobia (R); and (3) plants inoculated with rhizobia and amended with sewage sludge (RS). Two levels of irrigation were imposed: (1) well-watered and (2) drought stress. Under well-watered conditions, nitrogen-fixing plants have increased photosynthesis and stem fermentable carbohydrate concentrations, which result in higher potential for biomass conversion to bioethanol than in AN plants. The latter had higher lignin due to enhanced activities of phenolic metabolism-related enzymes. Under drought conditions, the potential for bioethanol conversion decreased to a similar level in all treatments. Drought-stressed nitrogen-fixing plants have high concentrations of fermentable carbohydrates and cell wall cellulose, but ammonium nitrate-fed plants produced higher plant and stem biomass, which might compensate the decreasing stem carbohydrates and cellulose concentrations.

Relationship between photosynthetic capacity, nitrogen assimilation and nodule metabolism in alfalfa (Medicago sativa) grown with sewage sludge.

Sewage sludge has been used as N fertilizer because it contains some of inorganic N, principally as nitrate and ammonium ions. However, sewage sludge addition to legumes could result in impaired nodule metabolism due to the presence of inorganic N from sludge. A greenhouse experiment was conducted to examine the effects of sewage sludge on growth, photosynthesis, nitrogen assimilation and nodule metabolism in alfalfa (Medicago sativa L. cv. Aragón). Plants were grown in pots with a mixture of perlite and vermiculite (2:1, v/v). The experiment included three treatments: (1) plants inoculated with rhizobia and amended with sewage sludge at rate of 10% (w/w) (RS); (2) plants inoculated with rhizobia without any amendment (R); and (3) non-inoculated plants fed with ammonium nitrate (N). N(2)-fixing plants had lower growth and sucrose phosphate synthase activity but higher photosynthesis than nitrate-fed plants because they compensated the carbon cost of the rhizobia. However, sewage sludge-treated plants evidenced a loss of carbon sink strength due to N(2) fixation by means of decreased photosynthetic capacity, leaf chlorophylls and N concentration in comparison to untreated plants. Sewage sludge did no affect nodulation but decreased nodule enzyme activities involved in carbon and N metabolisms that may lead to accumulation of toxic N-compounds.