The occurrence of endotoxin in sows with coliform mastitis

The purpose of this study was to determine the role of endotoxins in the etiology of coliform mastitis /CM/ in sows under field conditions, by using the Limulus amebocyte lysate /LAL/ test for the detection of endotoxins in the blood of pigs. For this purpose, blood samples from 40 healthy sows and 46 sows with clinical signs of CM were drawn once between 24 and 72 h post partum and tested accordingly. Only one clinically healthy sow 2.5% showed the presence of endotoxins in the serum. In sows clinically affected with one or more symptoms of the CM, the bacterial toxins were detected in 15 cases /32.5%/. The results of these studies support the observation that in only a certain percentage of all CM cases the occurrence of endotoxin in blood can be shown. Sampling time in relation to the occurrence of clinical symptoms and sampling frequency may have had an influence on the detectability of circulating endotoxins. Consequently, not all cases with endotoxemia may have been identified. The usefulness of the LAL test for endotoxin detection in the blood of pigs was confirmed.

Effect of Pseudomonas aeruginosa exotoxin A on CD3-induced human T-cell activation

The effect of Pseudomonas aeruginosa (PA) exotoxin A (P-ExA) on CD3-induced T-cell activation was studied on the level of T-cells (proliferation, synthesis of interleukin (IL)-2, expression of IL-2R complex, ICAM-1,2 and LFA-1 molecules), and on the level of monocytes (expression of ICAM-1,2, LFA-1 molecules, as well as FcRI and CD14 receptors). We found that: (1) P-ExA blocked T-cell proliferation and this effect was totally reversed by intact monocytes, and partially by IL-2 or TPA but not by costimulatory cytokines (IL-1alpha, IL-1beta, TNF-alpha or IL-6); (2) P-ExA transiently, in short-term cultures (48 h), inhibited synthesis of IL-2; (3) prolonged stimulation (96 h) of peripheral blood mononuclear cells (PBMC) or CD4 + T-cells with P-ExA in high or low doses (100 and 10 ng/ml, respectively), enhanced the level of IL-2 in the cultures; (4) P-ExA at low dose, combined with IL-1beta, TNF-alpha or IL-6, up-regulated synthesis of IL-2; and (5) stimulation of T-cells with anti-CD3 monoclonal antibody (mAb) and P-ExA at high dose diminished the expression of the p55 chain but not of the p75 chain of IL-2R complex and slightly affected the expression of CD3 complex, ICAM-1,2 and LFA-1 molecules. Hence, P-ExA can regulate the level of IL-2 in cultures of CD3-induced T-cells either by inhibition of IL-2 consumption (when P-ExA is applied in high dose), or by induction of IL-2 production (a costimulatory effect exerted by P-ExA in low dose in combination with monokines). Action of P-ExA on monocytes resulted in: (1) inhibition of the expression of ICAM-1,2 molecules and their ligand LFA-1 molecule; (2) low expression of FcRI receptor (a ligand for Fc part of CD3 mAb); and (3) inhibition (over 90%) of the expression of CD14 molecule. In conclusion, P-ExA-induced anergy of T-cells depends on: (a) decrease in the affinity of IL-2R complex on activated T-cells; and (b) inhibition of the accessory activities of monocytes.

Biological effects of Pseudomonas aeruginosa exotoxin A: lymphoproliferation of T lymphocytes in athymic mice

Pseudomonas aeruginosa exotoxin A has been observed to exert modulatory effects on the immune response. The present study examines the ability of exotoxin A to induce proliferation of splenocytes from athymic nu/nu mice. We observed that exotoxin A induced the proliferation of athymic nude splenocytes which could be abrogated by heating the toxin at 70 degrees C or by preincubation of the toxin with rabbit anti-exotoxin A antiserum. Photoaffinity-labelled toxin significantly induced splenocyte proliferation although the relative activity was reduced. Maximum nude splenocyte proliferation was observed at a toxin dose of 100 ng. This same dose was shown previously for athymic splenocytes to induce an enhanced response to the thymus-dependent (TD) antigen, sheep red blood cells (SRBC). The increased [3H]-TdR uptake in athymic splenocytes stimulated by exotoxin A was initiated by 24 hours and continued to day 10. Nude splenocytes depleted of Ig+ and Ia+ cells were induced to proliferate by exotoxin A. Cyclosporin A addition abrogated the ability of exotoxin A to induce proliferation. These results suggest that Pseudomonas aeruginosa exotoxin A can stimulate the proliferation of splenic T lymphocytes in athymic nu/nu mice.

Induction of an immune response in athymic nude mice to thymus-dependent antigens by Pseudomonas aeruginosa exotoxin A

Exposure of spleen cells from athymic nude mice to Pseudomonas aeruginosa exotoxin A induces these cells to respond to the thymus-dependent (TD) antigen sheep erythrocytes (SRBC). The response induced by toxin is dose dependent, antigen specific, and not due to polyclonal B-cell activation. Enhancement of the anti-SRBC response can be observed when toxin addition precedes antigen stimulation by 24-48 hr, which decreases when toxin administration follows antigen stimulation. A significant response is also observed when toxin and antigen are added simultaneously. A significant anti-SRBC response can be observed out to Day 10 postantigen and toxin stimulation after attaining a peak response at Day 5. Cultures exposed to toxin in the presence or absence of antigen exhibited a higher cell number and relative number of B cells as compared to control cultures. Exposure of T-cell depleted B cells from euthymic +/nu mice to toxin plus antigen does not result in an anti-SRBC response indicating that exotoxin A alone is not sufficient to induce B-cell responsiveness to T-dependent antigens and that other cells and/or factors are involved in the toxin-induced responsiveness of nude mice to T-dependent antigens.

Effect of anticoagulants on the chromogenic Limulus lysate assay for endotoxin

We have examined the effects of anticoagulants on the chromogenic Limulus lysate assay for endotoxin. The results indicate that both heparin and CPD Adenine 1 have a striking dose related inhibitory effect on the assay. At concentrations of heparin as low as about 30 U/ml there was a 90% reduction in detectable endotoxin. The inhibitory effect of up to 100 U/ml of heparin could be neutralised by the addition of protamine sulphate. Anticoagulants appear to be an additional factor which can adversely affect the Limulus chromogenic assay for endotoxin. This further emphasises the need for alternative approaches to the measurement of endotoxin.

Turbidimetric method for quantifying serum inhibition of Limulus amoebocyte lysate

This study describes a method to quantify the inhibition of lipopolysaccharide (LPS) activity by serum with a turbidimetric Limulus amoebocyte lysate assay. Assays were performed in multiwell microplates, and turbidity was measured as the optical density at 380 nm with a microplate spectrophotometer. LPS potency was measured as the 50% maximal Limulus amoebocyte response (LR50) of LPS diluted with saline. By comparing LR50s in saline, LPSs from various species of bacteria were standardized against the U.S. Reference Standard Endotoxin, lot EC-5. The potency of Escherichia coli O113 and O18 and Serratia marcescens LPSs was found to be equal to that of the reference standard EC-5, whereas LPSs from two salmonella species were half as potent. The least potent LPSs tested, obtained from Klebsiella pneumoniae and E. coli rough mutant J5, were 5- and 10-fold less potent, respectively, than EC-5. As a measure of inhibition, the LR50 of LPS in serum was compared to the LR50 of LPS in saline. Serum inhibited the potency of LPS 103- to 6,400-fold compared with saline. A positive correlation was found between standardized potency in saline and serum inhibition of the various LPSs tested. Thus, LPSs from E. coli O113, O18, and EC-5 and S. marcescens, which exhibited the highest potency in saline, were inhibited the most by serum. Likewise, E. coli J5 and K. pneumoniae LPSs, which were the least potent tested, were the least inhibited. The degree of inhibition of all types of LPS tested increased with increasing serum concentration.

Alteration of murine immune response by Pseudomonas aeruginosa exotoxin A

Pseudomonas exotoxin A has been implicated as a possible virulence factor in Pseudomonas infections. This toxin has a direct cytotoxic effect on a number of cell types, including macrophages and their precursors, and therefore may affect other cells of the immune system. NFR/N(H-2q) (+/nu or nu/nu) mice were immunized with either T-dependent or T-independent antigens along with various doses of exotoxin A. The immune response was then assayed by a modification of the Jerne plaque assay. Exotoxin A induced a dose-dependent suppression of the in vitro and in vivo immune responses to T-dependent and T-independent antigens in immunocompetent +/nu mice. However, in NFR/N nu/nu mice, suppression of the immune response to the T-independent antigen trinitrophenylated-Ficoll was not observed. Instead, a marked enhancement of the response was observed at doses of 100 and 10 ng of exotoxin A. Removal of T-cells with anti-Thy 1.2 antiserum plus complement before antigen and exotoxin A stimulation in +/nu mice results in abrogation of the suppression. These data suggest that Pseudomonas exotoxin A exerts an effect on both B- and T-lymphocyte populations to modulate the immune response and that this activity may be one facet of the pathogenic effects of this toxin.

Anti-lipopolysaccharide immunotherapy in management of septic shock of obstetric and gynaecological origin

Freeze-dried human plasma rich in anti-lipopolysaccharide (anti-LPS) immunoglobulin G was used to treat septic shock (systolic pressure less than or equal to 80 mm Hg, central venous pressure greater than or equal to 6 cm H2O) in obstetric and gynaecological patients. Mortality in conventionally treated patients was 9/19 (47.4%) compared with 1/14 (7.1%) in anti-LPS-treated patients. Anti-LPS caused the mean arterial pressure to rise from 45.1 +/- 7.36 mm Hg to 69.1 +/- 9.07 mm Hg within 75 min of administration. The mean hospital stay of survivors was 28.1 days for controls and 14.2 days for the anti-LPS-treated patients. The development of complications of septic shock was much reduced in the treated group. Anti-LPS thus appears significantly to reduce mortality and morbidity in septicaemia.

Polymyxin B inactivation of lipopolysaccharide in vaccines of Gram-negative bacteria

Endotoxin activity in suspensions of Bordetella pertussis, Escherichia coli, Haemophilus influenzae, and Pseudomonas aeruginosa was often markedly decreased by polymyxin B. Polymyxin B treatment may be a means to reduce inflammatory reactivity of lipopolysaccharide in vaccines of gram-negative bacteria.

Biological activity of the pure thymus protein, LSHr

LSHr, a protein from thymus, was shown to be a single pure peptide of 80,000 daltons by its migration in Sephadex G-150, SEDImentation velocity ultracentrifugation, both regular and SDS gel electrophoresis, and isoelectric focusing as a single symmetrical peak. It promoted the differentiation of T-lymphocytes in in vitro and in vivo tests. Human bone marrow cells showed differentiation in response to LSHr treatment to express a surface marker unique to T-cells following incubation with 10(-14) to 10(-9) M LSHr. Control proteins showed no effect. In preliminary experiments, administration of microgram quantities of LSHr to nude mice for 2-3 weeks induced development of T-cell function as determined by antibody response to a T-dependent antigen, and a response of spleen cells to T-cell mitogen.

In vitro induction of E-rosette formation in human bone marrow cells by the thymic proteins LSHr and LSHh

Two thymic factors, LSHh and LSHr, were found to be active in the induction of E-rosette formation. In vitro incubation of human bone marrow cells, isolated by Ficoll gradient centrifugation, with subnanogram quantities of either of these LSH proteins increased the number of E-rosette-forming cells in the bone marrow cultures by a factor of two. Kidney extract and bovine serum albumin did not show significant activity when tested as controls. Commercial thymopoietin II peptide was found to be active in the assay at comparable concentrations. The data allow a comparison of LHS proteins with other preparations tested in this manner.