Sustained biological effects of porcine interleukin 5 delivered to pigs as recombinant protein or via a DNA vector.

The ability of cytokines to act as natural immunotherapeutics to enhance the health and the disease resistance of animals is of particular interest to the intensive livestock industries. Antibiotics have been used for such purposes over a long period of time, however, there is growing concern that this practice will enhance the development of antibiotic resistance in a range of bacterial pathogens. In several species, interleukin 5 (IL-5) is known to enhance B cell activity and to increase the numbers of eosinophils in blood and tissues. In this report, IL-5 was delivered to pigs, either as a recombinant protein or via a DNA delivery vector and was shown to elevate eosinophils in blood over a sustained period. Interleukin 3, a potent haemopoietic factor, did not synergize with IL-5 when both cytokines were given together, but did prime the pigs for a stronger response to IL-5. These results demonstrate that IL-5 can readily be delivered to commercial pigs to elicit a significant biological effect.

Oxidation of acid-volatile sulfide in surface sediments increases the release and toxicity of copper to the benthic amphipod Melita plumulosa.

Acid-volatile sulfides (AVS) are an important metal-binding phase in sediments. For sediments that contain an excess of AVS over simultaneously extracted metal (SEM) concentrations, acute or chronic effects should not result from the metals Cd, Cu, Ni, Pb and Zn. While AVS phases may exist in surface sediments, the exposure to dissolved oxygen may oxidize the AVS and release metals to more bioavailable forms. We investigated the role of oxidation of AVS, and specifically copper sulfide phases, in surface sediments, in the toxicity to juveniles of the epibenthic amphipod, Melita plumulosa. Sediments containing known amounts of copper sulfide were prepared either in situ by reacting dissolved copper with AVS that had formed in field sediments or created in sediments within the laboratory, or by addition of synthesised CuS to sediments. Regardless of the form of the copper sulfide, considerable oxidation of AVS occurred during the 10-d tests. Sediments that had a molar excess of AVS compared to SEM at the start of the tests, did not always have an excess at the end of the tests. Consistent with the AVS-SEM model, no toxicity was observed for sediments with an excess of AVS throughout the tests. However, the study highlights the need to carefully consider the changes in AVS concentrations during tests, and that measurements of AVS and SEM concentrations should carefully target the materials to which the organisms are being exposed throughout tests, which in the case of juvenile M. plumulosa is the top few mm of the sediments.

The influence of sediment particle size and organic carbon on toxicity of copper to benthic invertebrates in oxic/suboxic surface sediments.

The use of sediment quality guidelines to predict the toxicity of metals in sediments is limited by an inadequate understanding of exposure pathways and by poor causal links between exposure and effects. For a 10-d exposure to Cu-spiked sediments, toxicity to the amphipod Melita plumulosa was demonstrated to occur through a combination of dissolved and dietary Cu exposure pathways, but for the bivalves Spisula trigonella and Tellina deltoidalis, toxicity occurred primarily by exposure to dissolved Cu. For relatively oxidized sediments that had moderate amounts of organic carbon (2.6-8.3% OC), silt (20-100% <63-µm particles) but low acid-volatile sulfide (AVS), acute toxicity thresholds for the three species were derived based on the OC-normalized Cu concentration of the less than 63-µm sediment fraction. For all three species, no effects were observed at concentrations below 10 µg/L dissolved Cu (in pore water and overlying water) or below 12 mg Cu/g OC (for <63 µm sediment). For sediments with silt/OC properties of 20/0.5, 50/1, or 70/4%, the particulate Cu-based threshold equated to 60, 120, or 480 mg Cu/kg, respectively. For oxic/suboxic sediments in which AVS is not limiting metal availability, sediment quality guidelines of this form will provide adequate protection against toxicity and improve the prediction of effects for sediments with varying properties.

Administration of porcine interleukin-3 induces increased levels of blood eosinophils.

Increasing resistance to anthelmintic drugs indicates a vital need to develop alternative strategies to control helminth infections. Interleukin-3 (IL-3) is a multilineage hematopoietic growth regulator produced by activated T lymphocytes in response to infection. In helminth infections, eosinophils play an important role in the elimination of parasites through their recruitment of inflammatory cells and the release of granules. The ability of IL-3 to stimulate the development of eosinophils makes it a particularly important candidate for therapeutic use to protect against parasites. To enable the role of IL-3 in the development, growth, and differentiation of porcine eosinophils to be elucidated, recombinant IL-3 (rPoIL-3) was expressed and purified. As the amino acid sequence identities between porcine IL-3 and other reported species were quite low ( approximately 39% between human and pig), an assessment of the in vitro activity of rPoIL-3 was made. The culture of porcine bone marrow (BM) cells with rPoIL-3 stimulated the proliferation of SWC3a(hi) myeloid cells, conA rming that rPoIL-3 acted as a hematopoietic cell growth factor. Since rPoIL-3 stimulated the development of myeloid cells in culture, the in vivo potential to produce elevated eosinophil proportions was assessed. In vivo administration of rPoIL-3 induced a signiA cant increase in the number of eosinophils in blood. These results suggest that rPoIL-3 is a potent inducer of eosinophils in swine and supports the inclusion of rPoIL-3 in therapeutic strategies.

Porcine interleukin-3 enhances DNA vaccination against classical swine fever.

DNA vectors can be used to deliver vaccine antigens that stimulate effective protective immunity in mice, but in larger, outbred animal species, the protective efficacy is lower or large doses of DNA are required. These data demonstrate that porcine interleukin-3 (IL-3) when delivered to pigs by DNA vector or in low doses as recombinant protein, can enhance antibody responses to classical swine fever virus antigen expressed from co-delivered DNA, and improve the protective efficacy of the DNA vaccine. The effect was further enhanced when IL-3 was expressed as a fusion protein with the potyvirus coat protein. The adjuvant effect of IL-3 was compared to that of granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-3 was shown to be at least as efficacious as GM-CSF. The response to IL-3 is novel and suggests, that at least in pigs, IL-3 could be used as an adjuvant for DNA vaccines.