Specific antibodies to soluble alpha-synuclein conformations in intravenous immunoglobulin preparations

Alpha-synuclein is the major protein in Lewy bodies, the hallmark pathological finding in Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Although normally intracellular, it also can be secreted, so extracellular alpha-synuclein may contribute to neuronal injury. Serum antibodies to alpha-synuclein could exert protective effects by increasing alpha-synuclein's movement out of the brain and, if they cross the blood-brain barrier, by inhibiting its neurotoxic effects. The objective of this study was to measure antibody concentrations to alpha-synuclein monomer and soluble oligomers in three intravenous immunoglobulin (IVIG) preparations, Gamunex (Talecris Biotherapeutics), Gammagard (Baxter Healthcare) and Flebogamma (Grifols Biologicals). Antibodies were measured in native IVIG preparations and after antibody-antigen complex dissociation. IVIG's non-specific binding was subtracted from its total binding to alpha-synuclein to calculate specific anti-alpha-synuclein antibody concentrations. Specific antibodies to alpha-synuclein monomer and/or soluble oligomers were detected in all IVIG products. In native IVIG preparations, the highest anti-monomer concentrations were in Gammagard and the highest anti-oligomer concentrations were in Gamunex; the extent to which lot-to-lot variation may have contributed to these differences was not determined. Antibody-antigen complex dissociation had variable effects on these antibody levels. The IVIG preparations did not inhibit alpha-synuclein oligomer formation, although they changed the distribution and intensity of some oligomer bands on Western blots. The presence of antibodies to soluble alpha-synuclein conformations in IVIG preparations suggests that their effects should be studied in animal models of synucleinopathies, as a first step to determine their feasibility as a possible treatment for PD and other synucleinopathies.

Ceruloplasmin immunoreactivity in neurodegenerative disorders

Ceruloplasmin (CP) is a 132 kd cuproprotein which, together with transferrin, provides the majority of anti-oxidant capacity in serum. Increased iron deposition and lipid peroxidation in the basal ganglia of subjects with hereditary CP deficiency suggest that CP may serve as an anti-oxidant in the brain as well. The present study compared CP immunoreactivity in brain specimens from normal controls and subjects with neurodegenerative disorders (Alzheimer's disease [AD], Parkinson's disease [PD], progressive supranuclear palsy [PSP], and Huntington's disease [HD]) (n = 5 per group). The relative intensity of neuronal CP staining and the numbers of CP-stained neurons per 25x microscope field were determined in hippocampus (CA1, subiculum, and parahippocampal gyrus), parietal cortex, frontal cortex, substantia nigra, and caudate. CP was detected in both neurons and astrocytes in all specimens, and in senile plaques and occasional neurofibrillary tangles in AD brain. Neuronal CP staining intensity tended to increase in most AD brain regions, but was statistically significant vs controls only in the CA1 region of hippocampus (p = .016). Neuronal CP staining in brain specimens from other neurodegenerative disorders showed a slight but nonsignificant increase vs controls. The numbers of CP-stained neurons per field did not differ between the various neurodegenerative disorders and controls. These results suggest that a modest increase in neuronal CP content is present in the AD brain, and lesser elevations in neuronal CP occur in the other neurodegenerative disorders in this study. Though CP functions as both an acute phase protein and an anti-oxidant in peripheral tissues, whether it does so in the brain remains to be determined.

Purine-induced alterations of dopamine metabolism in rat pheochromocytoma PC12 cells

Studies with cerebrospinal fluid from subjects with Parkinson's disease suggest that purine abnormalities may be present in this disorder. The effects of purines on dopamine metabolism have not been characterized, though adenosine is known to inhibit dopaminergic neurotransmission. In this study, dopamine, its precursor 3,4-dihydroxyphenylalanine (DOPA), and its degradation products 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) were measured in rat pheochromocytoma PC12 cells following 24-h incubation with 5, 50, and 500 microM adenosine, adenine, guanosine, guanine, hypoxanthine, xanthine, and uric acid. Incubation with adenosine increased DOPA, DOPAC, and HVA, while adenine treatment decreased DOPA. Guanosine (500 microM) decreased DOPA, dopamine, and DOPAC, while lower concentrations increased DOPAC and HVA. Incubation with guanine decreased dopamine, and xanthine decreased dopamine and DOPAC. Hypoxanthine and uric acid exerted minimal effects. These results indicate that purines exert a variety of effects on dopamine metabolism. The influence of purine metabolism on the dopaminergic deficit in the Parkinsonian brain merits further investigation.

L-DOPA does not enhance hydroxyl radical formation in the nigrostriatal dopamine system of rats with a unilateral 6-hydroxydopamine lesion

The debate about the toxicity of L-DOPA to dopaminergic neurons has not been resolved. Even though enzymatic and nonenzymatic metabolism of L-DOPA can produce hydrogen peroxide and oxygen free radicals, there has been controversy as to whether L-DOPA generates an oxidant stress in vivo. This study determined whether acute or repeated administration of L-DOPA caused in vivo production of hydroxyl radicals in striatum and other brain regions in rats with a unilateral 6-hydroxydopamine lesion of the dopaminergic nigrostriatal projections. Salicylate trapping combined with in vivo microdialysis provided measurements of extracellular 2,3-dihydroxybenzoic acid (2,3-DHBA) in striatum following L-DOPA administration systemically (100 mg/kg, i.p.) or by intrastriatal perfusion (1 mM, via the microdialysis probe). Tissue concentrations of 2,3-DHBA and salicylate were also measured in striatum, ventral midbrain, and cerebellum following repeated administration of L-DOPA (50 mg/kg, i.p., once daily for 16 days). In each instance, treatment with L-DOPA did not increase 2,3-DHBA concentrations, regardless of the nigrostriatal dopamine system's integrity. When added to the microdialysis perfusion medium, L-DOPA resulted in a significant decrease in the striatal extracellular concentration of 2,3-DHBA. These results suggest that administration of L-DOPA, even at high doses, does not induce hydroxyl radical formation in vivo and under some conditions may actually diminish hydroxyl radical activity. Furthermore, prior damage to the nigrostriatal dopamine system does not appear to predispose surviving dopaminergic neurons to increased hydroxyl radical formation following L-DOPA administration. Unlike L-DOPA, systemic administration of methamphetamine (10 mg/kg, s.c.) produced a significant increase in the concentration of 2,3-DHBA in striatal dialysate, suggesting that increased formation of hydroxyl radicals may contribute to methamphetamine neurotoxicity.

Measurement of acute phase proteins in the rat brain: contribution of vascular contents

A localized acute phase response occurs in the brain in Alzheimer's disease. Acute phase proteins have previously been measured in brain homogenates to quantify this response. The extent to which measurements of these proteins reflect brain parenchymal contents, as opposed to vascular contents, is unknown. In this study, the acute phase proteins ceruloplasmin (CP), complement factor 3 (C3), haptoglobin (HP), and albumin were measured in regional brain homogenates from phosphate buffered saline-perfused and sham-perfused rats (n = 7-9/group). Interleukin 1-beta (IL1-beta) and copper were also measured. Mean CP, C3, HP, and albumin concentrations in perfused specimens decreased by 94%, 88%, 90%, and 81% vs. sham-perfused specimens (all p < 0.001), while IL1-beta and copper were unchanged. These results suggest that acute phase protein measurements in brain homogenates reflect primarily vascular contents. However, IL1-beta and copper concentrations in brain homogenates are minimally influenced by vascular contents.

Time-dependent effects of levodopa on regional brain dopamine metabolism and lipid peroxidation

Levodopa treatment in Parkinson's disease has been suggested to contribute to disease progression through free radical generation. We compared the time course of levodopa-induced dopamine metabolism, and the resulting oxidative stress, between rat brain regions with varying dopaminergic innervation. At 1, 4, 8, and 12 h after levodopa administration (100 mg/kg), dopamine, dihydroxyphenylacetic acid, and homovanillic acid were measured in striatum and ventral midbrain, regions containing marked dopaminergic innervation, and in prefrontal cortex and cerebellum, which possess little dopaminergic innervation. Malondialdehyde, a marker of oxidative stress, was measured in additional animals. The return of dopamine and its metabolites to control concentrations tended to be slower (by 3-8 h) in cerebellum and prefrontal cortex than in dopaminergic regions. Malondialdehyde concentrations were decreased (p < 0.05) in ventral midbrain 8 h posttreatment, but increased in cerebellum 12 h posttreatment. We concluded that levodopa increases dopamine metabolism in nondopaminergic as well as dopaminergic regions, with delayed clearance of dopamine and its metabolites in nondopaminergic regions. The slower return of dopamine to control levels in nondopaminergic regions may be relevant to some of the side effects of levodopa. No support was found for the hypothesis that levodopa treatment induces oxidative stress.

Influence of repeated levodopa administration on rabbit striatal serotonin metabolism, and comparison between striatal and CSF alterations

Parkinson's disease (PD) is characterized by decreased striatal dopamine, but serotonin (5-HT) is also reduced. Because 5-HT decreases following a single levodopa injection, levodopa has been suggested to contribute to PD's serotonergic deficits. However, in a recent study, rat striatal serotonin levels were reported to increase following 15-day levodopa administration. To address this issue, we administered levodopa (50 mg/kg) to rabbits for 5 days, then measured serotonin, its precursors tryptophan and 5-hydroxytryptophan (5-HTP), and its major metabolite 5-hydroxyindole-acetic acid (5-HIAA) in striatum and CSF. Striatal serotonin and tryptophan were unchanged, while 5-HTP and 5-HIAA increased 4- and 7-fold, respectively. CSF 5-HTP and 5-HIAA were also significantly increased. In levodopa-treated animals, 5-HTP concentrations were moderately correlated (r = 0.679) between striatum and CSF, while weak correlations were present between striatal and CSF concentrations of both serotonin and 5-HIAA. These results suggest that repeated levodopa treatment increases striatal serotonin turnover without changing serotonin content. However, levodopa-induced alterations in striatal serotonin metabolism may not be accurately reflected by measurement of serotonin and 5-HIAA in CSF.

Altered guanosine and guanine concentrations in rabbit striatum following increased dopamine turnover

The significance of guanine nucleotides and nucleosides in neurodegenerative disorders is suggested by recent reports that these molecules enhance neurite branching and astrocyte proliferation. The objective of this study was to investigate the influence of increased dopamine metabolism, produced by 5-day treatment of rabbits with reserpine (2 mg/kg) or levodopa (LD) (50 mg/kg), on striatal concentrations of guanosine, guanine, and their metabolites. Reserpine treatment decreased striatal guanosine by 41% and increased guanine by 50%, while LD decreased guanosine by 48% (all p < 0.01 vs. vehicle-treated controls). LD also increased guanine by 22% (not statistically significant). Xanthine and uric acid concentrations were unchanged. Because of the neurotrophic properties of guanosine and guanine, changes in striatal concentrations of these purines secondary to increased dopamine (DA) turnover may have relevance for survival of remaining dopaminergic neurons in Parkinson's disease (PD).

Cerebrospinal fluid C3a increases with age, but does not increase further in Alzheimer's disease

Complement activation is present in the brain in Alzheimer's disease (AD), and C1q concentrations are decreased in AD cerebrospinal fluid (CSF). To determine whether concentrations of other complement proteins are also altered in AD CSF, we measured concentrations of C3a and SC5b-9 in CSF from patients with probable AD (n = 19), normal aged controls (n = 11), and normal younger controls (n = 15). C3a concentrations were similar between AD and aged controls, but threefold higher than in younger controls (p < 0.05 vs. both groups). A similar pattern was found with SC5b-9, though the increase was only twofold and statistically significant only for AD vs. younger controls. These results suggest that an increased generation of complement proteins in localized areas of the AD brain does not result in elevated concentrations of these proteins in CSF, compared with age-matched controls. Increased C3a (and, to a lesser extent, SC5b-9) in aged controls may be due to increased complement activation, increased central nervous system production, and/or blood-brain barrier leakage of these proteins.

Immunocytochemical detection of anti-hippocampal antibodies in Alzheimer's disease and normal cerebrospinal fluid

Immunocytochemical staining was performed to investigate the presence of anti-hippocampal antibodies in cerebrospinal fluid (CSF) from patients with probable Alzheimer's disease (AD) (n = 19), aged normal controls (n = 9), and young normal controls (n = 10). Marked staining of neurons in the granule cell layer of the dentate gyrus and in pyramidal neurons in CA1-3 of the rat hippocampus was observed in 5 AD CSF samples (26%), 1 aged control sample (11%), and 1 young control sample (10%). These differences were not statistically significant. One of the immunoreactive AD CSF specimens also contained high concentrations of C5b-9, the membrane attack complex. The infrequent occurrence of anti-hippocampal antibodies in AD CSF, and the detection of similar immunoreactivity in control CSF specimens, suggest that these antibodies are unlikely to play a role in the neurodegenerative process in most individuals with AD. However, elevated C5b-9 concentration in an AD CSF specimen with marked immunoreactivity to hippocampal neurons suggests the possibility that anti-neuronal antibodies may contribute to complement activation in some AD patients.

Increased regional brain concentrations of ceruloplasmin in neurodegenerative disorders

Ceruloplasmin (CP), the major plasma anti-oxidant and copper transport protein, is synthesized in several tissues, including the brain. We compared regional brain concentrations of CP and copper between subjects with Alzheimer's disease (AD, n = 12), Parkinson's disease (PD, n = 14), Huntington's disease (HD, n = 11), progressive supranuclear palsy (PSP, n = 11), young adult normal controls (YC, n = 6) and elderly normal controls (EC, n = 7). Mean CP concentrations were significantly increased vs. EC (P < 0.05) in AD hippocampus, entorhinal cortex, frontal cortex, and putamen. PD hippocampus, frontal, temporal, and parietal cortices, and HD hippocampus, parietal cortex, and substantia nigra. Immunocytochemical staining for CP in AD hippocampus revealed marked staining within neurons, astrocytes, and neuritic plaques. Increased CP concentrations in brain in these disorders may indicate a localized acute phase-type response and/or a compensatory increase to oxidative stress.

Transferrin and iron in normal, Alzheimer's disease, and Parkinson's disease brain regions

Oxidant-mediated damage is suspected to be involved in the pathogenesis of several neurodegenerative disorders. Iron promotes conversion of hydrogen peroxide to hydroxyl radical and, thus, may contribute to oxidant stress. We measured iron and its transport protein transferrin in caudate, putamen, globus pallidus, substantia nigra, and frontal cortex of subjects with Alzheimer's disease (n = 14) and Parkinson's disease (n = 14), and in younger adult (n = 8) and elderly (n = 8) normal controls. Although there were no differences between control groups with regard to concentrations of iron and transferrin, iron was significantly increased (p < 0.05) in Alzheimer's disease globus pallidus and frontal cortex and Parkinson's disease globus pallidus, and transferrin was significantly increased in Alzheimer's disease frontal cortex, compared with elderly controls. The transferrin/iron ratio, a measure of iron mobilization capacity, was decreased in globus pallidus and caudate in both disorders. Regional transferrin and iron concentrations were generally more highly correlated (Pearson's correlation coefficient) in elderly controls than in Alzheimer's and Parkinson's disease. The altered relationship between iron and transferrin provides further evidence that a disturbance in iron metabolism may be involved in both disorders.

A quantitative analysis of isoferritins in select regions of aged, parkinsonian, and Alzheimer's diseased brains

The brain requires a ready supply of iron for normal neurological function, but free iron is toxic. Consequently, iron bioavailability must be stringently regulated. Recent evidence has suggested that the brain iron regulatory system is dysfunctional in neurological disorders such as Alzheimer's and Parkinson's diseases (AD and PD, respectively). A key component of the iron regulatory system in the brain is ferritin. Ferritin consists of 24 subunits, which are distinguished as either a heavy-chain (H) or light-chain (L) isoform. These peptide subunits are genetically and functionally distinct. Thus, the ability to investigate separately the types of ferritin in brain should provide insight into iron management at both the cellular and the molecular level. In this study, the ratio of isoferritins was determined in select regions of adult elderly AD and PD human brains. The H-rich ferritin was more abundant in the young brain, except in the globus pallidus where the ratio of H/L ferritin was 1:1. The balance of H/L isoferritins was influenced by age, brain region, and disease state. With normal aging, both H and L ferritin increased; however, the age-associated increase in isoferritins generally failed to occur in AD and PD brain tissue. The imbalance in H/L isoferritins was disease and region specific. For example, in frontal cortex, there was a dramatic (fivefold) increase in the ratio of H/L ferritin in AD brains but not in PD brains. In PD, caudate and putamen H/L ratios were higher than in AD and the elderly control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Markers of dopamine depletion and compensatory response in striatum and cerebrospinal fluid

Though depletion of CSF homovanillic acid (HVA) concentration has often been regarded as a direct indicator of dopamine (DA) deficiency in Parkinson's Disease (PD), CSF HVA is normal in mildly affected patients. To explore why, we measured DA and its metabolites in striatum and CSF in rabbits receiving reserpine for 5 days. Reserpine, which depletes striatal DA by disrupting vesicular storage of the neurotransmitter, results in a compensatory increase of DA turnover. In response to a 96% depletion of striatal DA, its catabolic intermediates 3,4-dihydroxyphenylacetic acid (DOPAC) and 3-methoxytyramine (3-MT) decreased 64% and 92% in striatum, although the endproduct, HVA, was unchanged. In contrast, CSF concentrations of HVA and DOPAC increased significantly, though 3-MT and levodopa (LD) were unaltered. A 5-fold rise in striatal LD concentration after reserpine-induced DA depletion provided evidence for enhanced DA synthesis. As in PD, the compensatory increase of DA synthesis after reserpine administration confounds the ability of CSF HVA to reflect DA depletion.

Effects of enhanced striatal dopamine turnover in vivo on glutathione oxidation

In Parkinson's disease (PD), a compensatory increase in dopamine (DA) turnover occurs in the remaining nigrostriatal dopaminergic neurons, resulting in greater exposure of each neuron to hydrogen peroxide (H2O2) derived from oxidative deamination of DA. The formation of oxyradicals from H2O2 is regarded as a mechanism that could contribute to the progression of PD, and incubation of rat striatal synaptosomes with levodopa (LD) results in an increase in oxidized glutathione (GSSG), indicative of oxidant stress. The present study was undertaken to determine whether striatal GSSG levels increase in response to administration of LD in vivo. Acute and repeated (3-week) treatment of normal rats with LD at doses of up to 100 mg/kg did not increase striatal GSSG despite marked increase in DA turnover. These results suggest that intact striatum may possess increased defense capacity against oxidant stress generated by increased DA turnover as compared with isolated synaptosomes.

Ceruloplasmin is increased in cerebrospinal fluid in Alzheimer's disease but not Parkinson's disease

Although the pathophysiology of Alzheimer's disease (AD) and Parkinson's disease (PD) is unknown, altered brain antioxidative mechanisms have been found in both disorders. Ceruloplasmin (CP) and transferrin (TF) interact to limit concentrations of free ferrous iron (Fe2+), and thus play an important role in antioxidant defense in serum; both proteins are also produced in brain, where their significance as antioxidants is unknown. We quantified concentrations of CP and TF by immunoassay in AD (n = 17) and PD (n = 12) cerebrospinal fluid (CSF) to determine whether these proteins could serve as disease markers. CP was increased versus aged normal subjects (n = 11) in AD (p < 0.05) but not PD CSF, whereas TF concentrations did not differ between groups. CP levels have been reported to be elevated in some brain regions in AD, and increased CP in AD CSF may reflect this finding. Systemic inflammation and oxidative stress are major factors stimulating hepatic CP synthesis, and it remains to be determined whether increased CP concentrations in AD CSF and brain follow from similar mechanisms.

Influence of tumour physico-chemical conditions on interleukin-2-stimulated lymphocyte proliferation

The proliferative response of murine lymphocytes to interleukin-2 (IL-2) was examined under physico-chemical conditions present in solid tumours, namely low oxygen and glucose concentrations and acidic pH. Lymphocytes were cultured for four days in 30 U ml-1 IL-2 to simulate serum IL-2 concentrations attainable with high-dose systemic IL-2 therapy. Lymphocyte proliferation was significantly (P < 0.05) reduced by low oxygen concentrations (both anoxia [0% O2] and hypoxia [10%, low glucose (6 mg dl-1), or acidic pH (6.7 or 6.4). Moderate glucose concentration (32 mg dl-1), or neutral pH (7.0) did not impair proliferation. This study indicates that impairment of lymphocyte proliferation by tumour physico-chemical conditions may be a factor in the relatively poor success rate of IL-2/LAK cell immunotherapy.

Non-specific binding of normal human IgG, including F(ab')2 and Fc fragments, to embryonic rat brain neurons and human cortex synaptosomes

Binding of normal human IgG to embryonic rat brain neurons was quantitated by flow cytometry. IgG binding was linear between 0.05 and 1.5 mg/ml; slight binding was detectable even at normal cerebrospinal fluid concentrations. Similar binding curves were obtained for purified Fc and F(ab')2 fragments from normal human IgG. Normal human IgG also bound to synaptosomes (resealed nerve terminals) from human cerebral cortex. However, competition assays utilizing 125I-IgG showed no evidence for specific binding. This study indicates that the specificity of putative anti-neuronal antibodies should be confirmed by competition assays as for other receptor-ligand binding.

Associated effects of bromocriptine on neoplastic progression of mouse mammary preneoplastic hyperplastic alveolar nodule line C4 and on hyperplastic alveolar nodule-infiltrating and splenic lymphocyte function

Progression of the mouse mammary preneoplastic hyperplastic alveolar nodule (HAN) line C4 to carcinoma can be enhanced by stimulators and depressed by inhibitors of host lymphocyte function (W.Z. Wei et al., Cancer Res., 49: 2709-2715, 1989). The purpose of the present study was to ask whether prolactin (PRL), a regulator of both mammary epithelial and lymphoid cells, might be a factor in the association between lymphocytic function and HAN progression. Daily administration of bromocriptine, a suppressor of pituitary PRL secretion, increased the latency period and decreased the incidence of tumor development in HAN bearing mice. Bromocriptine treatment suppressed in vitro responsiveness of HAN-infiltrating lymphocytes and, to some extent, spleen cells, to T- and B-cell mitogens, without altering the relative proportion of lymphocytic subsets. Suppression could be partially reversed by PRL treatment. Natural killer cell activity of HAN-infiltrating lymphocytes was also reduced by bromocriptine. In vitro incubation with anti-PRL antisera inhibited both lymphocyte mitogen responsiveness and natural killer activity in a concentration-dependent manner. PRL reversed this inhibition also. Altogether, these results demonstrate a correlation among tumor development, PRL levels, and lymphocyte function and suggest that an immune-endocrine network involving PRL may play a role in C4 HAN progression.

Analysis of distribution of tumor- and preneoplasia-infiltrating lymphocytes using simultaneous Hoechst 33342 labeling and immunophenotyping

Hoechst 33342 in vivo staining was combined with immunofluorescent staining of cell surface antigens to quantify the distribution, relative to blood supply, of lymphocytes in a preneoplastic mammary lesion, the murine C4 hyperplastic alveolar nodule (HAN), and the C4 adenocarcinoma which develops from C4 HAN. The vascular supply to lymphocytes expressing Thy 1.2, L3T4, Ly2, and ASGM1 cell surface antigens was evaluated in both tissues. The distribution of ASGM1+ cells, which include natural killer cells, differed between the two tissues, being significantly increased in the 20% brightest Hoechst-stained lymphocyte fraction in HAN but not in C4 tumor. Distribution of T lymphocytes did not differ between the two tissues. The combination of in vivo Hoechst 33342 with in vitro immunofluorescence provides a simple method to evaluate the distribution with regard to blood supply of lymphocyte subsets in solid tumors and preneoplastic lesions.

Natural killer-cell activity under conditions reflective of tumor micro-environment

Natural-killer(NK) activity was examined in the presence of low oxygen tension, low glucose concentration and acidic pH, to determine whether physical conditions present in the tumor micro-environment could play a role in down-regulating cytolytic activity of tumor-infiltrating lymphocytes with NK phenotype. Anoxia (0% O2), but not hypoxia (1% O2), significantly reduced NK activity, as did acidic pH (6.4 or 6.7). Low glucose concentration (6 mg/dl) did not impair NK activity. Combinations of either moderate (1% O2, 26 mg/dl glucose, pH 6.7) or extreme (0% O2, 6 mg/dl glucose, pH 6.4) alteration of physical conditions significantly reduced NK activity. This study indicates that the physico-chemical conditions present within solid tumors are capable of down-regulating NK activity.

Lymphocytic infiltration and cytotoxicity under hypoxic conditions in the EMT6 mouse mammary tumor

Infiltration of lymphocytes, neutrophils and macrophages was evaluated in hypoxic and well-oxygenated areas of the EMT6 mouse mammary adenocarcinoma, by in vivo staining with the fluorescent dye Hoechst 33342 followed by cell sorting on the basis of fluorescence intensity. Tumors were grouped by days post-injection (days 11-14, 15-17 and 20-27). As lymphocytes are the only host cell population in this tumor model to possess lytic activity against EMT6 tumor cells, the ability of sensitized T lymphocytes to lyse syngeneic EMT6 cells was examined under conditions of varying oxygen concentrations. Infiltrating lymphocytes were detected to the same extent in cell fractions from both areas in all tumors. In contrast, neutrophils were found in significantly higher percentages in the hypoxic population than in the well-oxygenated cell fraction of all but the largest tumors. Macrophages were present in significantly higher percentages in the well-oxygenated fraction than in the hypoxic fraction of day-11 to -14 tumors. Extreme radiobiological hypoxia (0% O2) resulted in a significant decrease in T-cell-mediated lysis of EMT6 tumor cells, compared to lysis in room air (20% O2), but lysis was not impaired under conditions of mild radiobiological hypoxia (1% O2). Our study indicates that host-cell infiltration into areas of differing oxygenation may be quantitated via in situ Hoechst staining followed by cell sorting; in the EMT6 tumor, lymphocytes appear to infiltrate hypoxic areas to the same extent as well-oxygenated areas, and T-lymphocyte killing of syngeneic tumor cells is significantly reduced, although still present, under these hypoxic conditions.

Determination by enzyme-linked immunosorbent assay of the optimal dose of staphylococcal leukocidin for systemic immunization of dairy cows

A dose-response study was conducted to determine the optimal dose of staphylococcal leukocidin toxin to use for systemic vaccination of lactating dairy cows. Each of 5 groups of cows (8 cows/group) were given 2 injections of crude leukocidin (dose range, 9 to 2,700 mg). Antileukocidin antibody concentration in milk samples collected before vaccination and at 4 and 10 weeks after vaccination was determined by use of an ELISA. The highest antibody concentration at postvaccination sample collection dates was observed in cows of the group immunized with 900 mg of leukocidin. This appeared to be the optimal vaccination dose for production of antileukocidin antibodies in the mammary gland of lactating cows.

Enzyme-linked immunosorbent assay for detection of leukocidin toxin from Staphylococcus aureus in bovine milk samples

An enzyme-linked immunosorbent assay was developed for the detection of leukocidin toxin from Staphylococcus aureus. The minimum concentration of leukocidin detectable with the assay was 30 ng/ml. The enzyme-linked immunosorbent assay was found to be a more sensitive method, by a mean of 45-fold, for leukocidin detection than was observation of cytolytic effects of the toxin on bovine neutrophils. A mean toxin concentration of 974 ng/ml was required to produce observable cytolytic effects on neutrophils. Although the enzyme-linked immunosorbent assay was able to detect leukocidin in milk samples from toxin-infused mammary glands, the toxin was detectable in only 2 of 27 S. aureus-infected milk samples (7%) from cows with chronic staphylococcal mastitis. To determine whether leukocidin antibodies in the mastitic milk samples were preventing toxin detection, leukocidin was mixed with milk with a high antileukocidin antibody titer (from a vaccinated cow) and evaluated with the immunoassay. Leukocidin was readily detected in this sample, indicating that milk antileukocidin antibodies were not sufficient to prevent detection of any leukocidin present in the mastitic milk samples. Failure to detect leukocidin in most mastitic milk samples with this assay indicated that, if leukocidin is produced in the bovine mammary gland during chronic staphylococcal mastitis, the concentration of the toxin may be too low to produce cytolytic effects on neutrophils.

Comparison of fluorescence intensity of Hoechst 33342-stained EMT6 tumour cells and tumour-infiltrating host cells

Hoechst 33342 is a fluorescent dye used for cell selection from tumours based upon intratumour location. When the dye is administered i.v. to tumour-bearing animals, cellular fluorescence is directly related to the proximity of cells to blood vessels. The present study compared inherent Hoechst fluorescence between in vitro-stained EMT6/Ro (mouse mammary sarcoma) cells and host cells, to determine if these populations have different staining characteristics that may influence cell selection procedures. Tumour cell fluorescence exceeded host cell staining by 8-fold when pure cell populations (EMT6/Ro monolayer cells, mouse spleen and peritoneal cells) were compared, and 3-fold for tumour cell-enriched and host cell-enriched populations from solid tumours. Inherent uptake of HO 33342 appeared to be correlated with cell volume. These differences in inherent dye uptake between host and tumour cells were found to be minor in comparison to the fluorescence gradient between the 10% brightest and 10% dimmest (78-fold) cell populations from in vivo-stained tumours.

Use of enzyme-linked immunosorbent assay to measure bovine milk and serum antibodies to alpha toxin, beta toxin, and capsular antigens of Staphylococcus aureus

An enzyme-linked immunosorbent assay (ELISA) procedure was used to quantitate milk and serum antibodies (IgG) to Staphylococcus aureus alpha and beta toxins, and S. aureus 2-8 and Smith diffuse strain capsular antigens. Milk samples were collected on two occasions. A comparison was made between levels of milk antibodies specific for the two toxins and capsular antigens for 41 cows that were infected with S. aureus on both sampling dates, and 18 cows not S. aureus-infected on either date. Staphylococcus aureus-infected cows were grouped according to somatic cell counts. All groups of infected cows, regardless of somatic cell counts, had significantly higher milk antibody levels to alpha and beta toxins than did the non-infected cows (P less than .002). Serum samples taken for 13 infected and 4 non-infected cows also indicated that significant elevations in anti-alpha toxin and anti-beta toxin IgG were present in S. aureus-infected cows, compared to non-infected cows. A similar immune response was not seen to capsular antigens, however. No significant differences were present between the two groups of cows for either milk or serum antibodies to Smith diffuse strain capsular antigens. Milk antibodies to 2-8 capsule were significantly elevated only in infected cows with somatic cell counts greater than 10(6)/ml, compared to non-infected cows; no differences were present for serum antibodies to 2-8 capsule between infected and non-infected cows. These results indicate that significant increases in milk (and possibly serum) antibodies to alpha and beta toxins are present in cows with chronic staphylococcal mastitis, apparently resulting from a systemic immune response to these toxins. There does not appear to be a similar immune response to capsular antigens.

Use of 51Cr release to measure the cytotoxic effects of staphylococcal leukocidin and toxin neutralization on bovine leukocytes

Leukocidin toxin from Staphylococcus aureus produces specific cytolytic effects on neutrophils and macrophages. The most commonly used method for determination of leukocidin activity is microscopic examination for characteristic morphological changes in toxin-treated cells. The 51Cr release assay was modified to allow quantitation of the cytolytic effects of leukocidin on bovine peripheral blood neutrophils and lymphocytes. Toxin neutralization by serum and milk samples was quantitated by this method. The neutralizing abilities of the various samples were found to correlate with the levels of immunoglobulin G (IgG1) specific for leukocidin. Undiluted normal serum samples, however, were capable of partially preventing the cytotoxic effects of leukocidin. The assay was shown to be an effective means of quantitating the cytotoxic activity of leukocidin on neutrophils as well as demonstrating neutralization of cytotoxicity by milk and serum samples.

Enzyme-linked immunosorbent assay for detection of milk immunoglobulins to leukocidin toxin of Staphylococcus aureus

Leukocidin toxin from a bovine strain of Staphylococcus aureus was partially purified by ion exchange chromatography. An enzyme-linked immunosorbent assay was developed to quantitate antibodies specific for leukocidin in bovine milk. This was used to assay quarter samples from 88 cows in a S aureus-infected herd for antibody levels to the toxin. Milk samples from 65 cows with S aureus infections in at least one quarter produced a mean optical density of 1.054, whereas milk samples from 23 cows that were free of bacteria on cultural examination had a mean optical density of 0.584. There was a significant difference (P less than 0.001) in milk anti-leukocidin levels between these 2 groups. Evaluation of serum samples from 40 of these cows indicated that the milk anti-leukocidin concentrations were reflective of systemic anti-leukocidin values. The capability of 57 milk samples to neutralize the cytolytic effect of minimal amounts of leukocidin on bovine peripheral blood neutrophils was examined. Good correlation existed between the enzyme-linked immunosorbent assay antibody concentration and toxin-neutralizing capability of individual milk samples.