Brain pharmacokinetics of anti-transferrin receptor antibody affinity variants in rats determined using microdialysis

Receptor-mediated transcytosis (RMT) is used to enhance the delivery of monoclonal antibodies (mAb) into the central nervous system (CNS). While the binding to endogenous receptors on the brain capillary endothelial cells (BCECs) may facilitate the uptake of mAbs in the brain, a strong affinity for the receptor may hinder the efficiency of transcytosis. To quantitatively investigate the effect of binding affinity on the pharmacokinetics (PK) of anti-transferrin receptor (TfR) mAbs in different regions of the rat brain, we conducted a microdialysis study to directly measure the concentration of free mAbs at different sites of interest. Our results confirmed that bivalent anti-TfR mAb with an optimal dissociation constant (KD) value (76 nM) among four affinity variants can have up to 10-fold higher transcytosed free mAb exposure in the brain interstitial fluid (bISF) compared to lower and higher affinity mAbs (5 and 174 nM). This bell-shaped relationship between KD values and the increased brain exposure of mAbs was also visible when using whole-brain PK data. However, we found that mAb concentrations in postvascular brain supernatant (obtained after capillary depletion) were almost always higher than the concentrations measured in bISF using microdialysis. We also observed that the increase in mAb area under the concentration curve in CSF compartments was less significant, which highlights the challenge in using CSF measurement as a surrogate for estimating the efficiency of RMT delivery. Our results also suggest that the determination of mAb concentrations in the brain using microdialysis may be necessary to accurately measure the PK of CNS-targeted antibodies at the site-of-actions in the brain.

A translational platform PBPK model for antibody disposition in the brain

In this manuscript, we have presented the development of a novel platform physiologically-based pharmacokinetic (PBPK) model to characterize brain disposition of mAbs in the mouse, rat, monkey and human. The model accounts for known anatomy and physiology of the brain, including the presence of distinct blood-brain barrier and blood-cerebrospinal fluid (CSF) barrier. CSF and interstitial fluid turnover, and FcRn mediated transport of mAbs are accounted for. The model was first used to characterize published and in-house pharmacokinetic (PK) data on the disposition of mAbs in rat brain, including the data on PK of mAb in different regions of brain determined using microdialysis. Majority of model parameters were fixed based on literature reported values, and only 3 parameters were estimated using rat data. The rat PBPK model was translated to mouse, monkey, and human, simply by changing the values of physiological parameters corresponding to each species. The translated PBPK models were validated by a priori predicting brain PK of mAbs in all three species, and comparing predicted exposures with observed data. The platform PBPK model was able to a priori predict all the validation PK profiles reasonably well (within threefold), without estimating any parameters. As such, the platform PBPK model presented here provides an unprecedented quantitative tool for prediction of mAb PK at the site-of-action in the brain, and preclinical-to-clinical translation of mAbs being developed against central nervous system (CNS) disorders. The proposed model can be further expanded to account for target engagement, disease pathophysiology, and novel mechanisms, to support discovery and development of novel CNS targeting mAbs.

Defining limits of treatment with humanized neutralizing monoclonal antibody for West Nile virus neurological infection in a hamster model

A potent anti-West Nile virus (anti-WNV)-neutralizing humanized monoclonal antibody, hE16, was previously shown to improve the survival of WNV-infected hamsters when it was administered intraperitoneally (i.p.), even after the virus had infected neurons in the brain. In this study, we evaluated the therapeutic limit of hE16 for the treatment of WNV infection in hamsters by comparing single-dose peripheral (i.p.) therapy with direct administration into the pons through a convection-enhanced delivery (CED) system. At day 5 after infection, treatments with hE16 by the peripheral and the CED routes were equally effective at reducing morbidity and mortality. In contrast, at day 6 only the treatment by the CED route protected the hamsters from lethal infection. These experiments suggest that hE16 can directly control WNV infection in the central nervous system. In support of this, hE16 administered i.p. was detected in a time-dependent manner in the serum, cerebrospinal fluid (CSF), cerebral cortex, brain stem, and spinal cord in CSF. A linear relationship between the hE16 dose and the concentration in serum was observed, and maximal therapeutic activity occurred at doses of 0.32 mg/kg of body weight or higher, which produced serum hE16 concentrations of 1.3 microg/ml or higher. Overall, these data suggest that in hamsters hE16 can ameliorate neurological disease after significant viral replication has occurred, although there is a time window that limits therapeutic efficacy.

Ratio of trastuzumab levels in serum and cerebrospinal fluid is altered in HER2-positive breast cancer patients with brain metastases and impairment of blood-brain barrier

Patients receiving trastuzumab for HER2-overexpressing metastatic breast cancer seem to suffer from an increased risk of brain metastases, even in cases with responsive disease. To evaluate whether trastuzumab is able to penetrate the blood-brain barrier, we measured trastuzumab levels in the serum and in cerebrospinal fluid of metastatic breast cancer patients with brain metastases receiving trastuzumab for HER2-overexpressing metastatic breast cancer. In a pilot study, metastatic breast cancer patients with brain metastases and HER2-overexpressing tumors (HercepTest; Dako, Copenhagen, Denmark) were included. At different time points, trastuzumab levels in the serum and cerebrospinal fluid were measured using a newly developed immunoenzymatic test for trastuzumab. Six out of eight patients were evaluable for determination of trastuzumab level in the serum and cerebrospinal fluid. Before radiotherapy, median trastuzumab level in the serum was 52 054 ng/ml compared with 124 ng/ml in cerebrospinal fluid (ratio 420 : 1). After completion of radiotherapy, median trastuzumab level was 20 185 ng/ml in the serum and 226 ng/ml in cerebrospinal fluid, respectively (ratio 76 : 1). With concomitant meningeal carcinomatosis, trastuzumab level in the serum after radiotherapy was 17 431 and 356 ng/ml in cerebrospinal fluid (ratio 49 : 1). For the first time, we present clinical evidence that trastuzumab levels in cerebrospinal fluid are increased under conditions of an impaired blood-brain barrier such as meningeal carcinomatosis or radiotherapy. This evidence supports the concept of continuing trastuzumab therapy in patients with brain metastases treated by radiotherapy. Monitoring of trastuzumab levels in the serum and cerebrospinal fluid may enable individualized therapy strategies in metastatic breast cancer patients with brain metastases, and lead to a better understanding of trastuzumab pharmacokinetics in the cerebrospinal fluid and serum.

Continuous delivery of a monoclonal antibody against Reissner's fiber into CSF reveals CSF-soluble material immunorelated to the subcommissural organ in early chick embryos

The subcommissural organ (SCO) is an ependymal differentiation located in the dorsal midline of the caudal diencephalon under the posterior commissure. SCO cells synthesize and release glycoproteins into the cerebrospinal fluid (CSF) forming a threadlike structure known as Reissner's fiber (RF), which runs caudally along the ventricular cavities and the central canal of the spinal cord. Numerous monoclonal antibodies have been raised against bovine RF and the secretory material of the SCO. For this study, we selected the 4F7 monoclonal antibody based on its cross-reactivity with chick embryo SCO glycoproteins in vivo. E4 chick embryos were injected with 4F7 hybridoma cells or with the purified monoclonal antibody into the ventricular cavity of the optic tectum. The hybridoma cells survived, synthesized and released antibody into the CSF for at least 13 days after the injection. E5 embryos injected with 4F7 antibody displayed precipitates in the CSF comprising both the monoclonal antibody and anti-RF-positive material. Such aggregates were never observed in control embryos injected with other monoclonal antibodies used as controls. Western blot analysis of CSF from E4-E6 embryos revealed several immunoreactive bands to anti-RF (AFRU) antibody. We also found AFRU-positive material bound to the apical surface of the choroid plexus primordia in E5 embryos. These and other ultrastructural evidence suggest the existence of soluble SCO-related molecules in the CSF of early chick embryos.

[Measurement of rituximab concentration in the cerebrospinal fluid in CNS lymphoma]

We measured rituximab concentrations in the cerebrospinal fluid (CSF) in 2 patients with diffuse large B-cell lymphoma in whom central nervous system (CNS) invasion had developed. They received rituximab intravenously following irradiation therapy (patient no.1) or along with chemotherapy (patient no.2). The rituximab concentrations in the CSF were considered to be very low (0.2-0.6 microg/ml), and could not be increased significantly by serial intravenous administrations of rituximab. The lymphoma relapsed in patient no.1, and the combined therapy was not effective in patient no.2. An alternative approach such as intrathecal administration of rituximab could be anticipated as a new therapeutic strategy for CNS lymphoma.

Unusual association of multiple sclerosis with monoclonal gammopathy of undetermined significance (MGUS): two case reports

We present two patients with demyelinating disease meeting the diagnostic criteria for multiple sclerosis. Both patients had IgG lambda monoclonal gammopathy in serum and cerebrospinal fluid associated with intrathecal antibody synthesis. This association is very unusual and it is not certain whether the co-occurrence of these disorders might be the result of a causal link between multiple sclerosis and monoclonal gammopathy or a fortuitous phenomenon.

The clinical significance of an intrathecal monoclonal immunoglobulin band: a follow-up study

BACKGROUND

Intrathecal oligoclonal band synthesis occurs in 95% of patients with clinically definite MS but may also occur in the context of CNS infection and other inflammatory conditions. By contrast, the significance of an intrathecal synthesis of a monoclonal band remains uncertain. Previously, an association between a single intrathecal band and CNS lymphoma has been reported but a relationship has also been shown with diagnoses more usually associated with an oligoclonal pattern. At present, it is not known whether a single band will convert to an oligoclonal response with time.

METHODS

Data were obtained from patients who had CSF and serum analyzed by isoelectric focusing (IEF) at the authors' institutions over a 6-year period. Clinical details were acquired for those who underwent repeat lumbar puncture after an initial CSF examination revealed an intrathecal monoclonal immunoglobulin G band.

RESULTS

Of the 31 patients identified as having an initial intrathecal monoclonal band, clinical details were available for 27. Of those, 9 were found on subsequent lumbar puncture to have developed an intrathecal oligoclonal response.

CONCLUSIONS

Among those subjects who developed oligoclonal bands, there was a propensity for either a diagnosis of MS or clinically isolated syndromes due to demyelination. In the 18 subjects who either reverted to having normal CSF IEF or continued to exhibit only the monoclonal band, no cases of MS were encountered. Importantly, one of these had cerebral lymphoma.

Primary orthostatic tremor associated with a persistent cerebrospinal fluid monoclonal IgG band

Primary orthostatic tremor is of unknown aetiology and is believed to be a distinct entity rather than a subtype of essential tremor. We describe the first patient with a typical phenotype of primary orthostatic tremor who has a persistent isolated monoclonal immunoglobulin G band in the cerebrospinal fluid.

Restricted transport of anti-transferrin receptor antibody (OX26) through the blood-brain barrier in the rat

Anti-transferrin receptor IgG2a (OX26) transport into the brain was studied in rats. Uptake of OX26 in brain capillary endothelial cells (BCECs) was > 10-fold higher than isotypic, non-immune IgG2a (Ni-IgG2a) when expressed as % ID/g. Accumulation of OX26 in the brain was higher in 15 postnatal (P)-day-old rats than in P0 and adult (P70) rats. Iron-deficiency did not increase OX26 uptake in P15 rats. Three attempts were made to investigate transport from BCECs further into the brain. (i) Using a brain capillary depletion technique, 6-9% of OX26 was identified in the post-capillary compartment consisting of brain parenchyma minus BCECs. (ii) In cisternal CSF, the volume of distribution of OX26 was higher than for Ni-IgG2a when corrected for plasma concentration. (iii) Immunohistochemical mapping revealed the presence of OX26 almost exclusively in BCECs; extravascular staining was observed only in neurons situated periventricularly. The data support the hypothesis of facilitated uptake of OX26 due to the presence of transferrin receptors at the blood-brain barrier (BBB). However, OX26 accumulation in the post-capillary compartment was too small to justify a conclusion of receptor-mediated transcytosis of OX26 occurring in BCECs. Accumulation of OX26 in the post-capillary component may result from a diphasic transport that involves high-affinity accumulation of OX26 by the BCECs, clearly exceeding that of Ni-IgG2a, followed by a second transport mechanism that releases OX26 non-specifically further into the brain. The periventricular localization suggests that OX26 probably also derives from transport across the blood-CSF barrier.

Treatment of meningeal breast cancer xenografts in the rat using an anti-p185/HER2 antibody

The metastatic spread of breast cancer to the leptomeninges (LM) is a painful, debilitating, and usually lethal condition. Current therapies are generally ineffective or extremely toxic. The current study evaluated monoclonal antibody therapy in an animal model of LM human breast cancer. Monoclonal antibody 4D5, which recognizes the extracellular domain of the HER2/neu receptor, was administered into the cerebrospinal fluid of athymic rats implanted with human breast cancer cell lines. Continuous intraventricular administration of 4D5 inhibited growth of SKBR3 cells that overexpress HER2/neu but not of MCF7 cells, which do not. Inhibition was dose-dependent, with higher doses of 4D5 producing an improved response. i.p. administration of cisplatin in addition to 4D5 did not improve results. Continuous administration of 4D5 into the lumbar, as opposed to the ventricular intrathecal space, was not therapeutically effective. Treatment with 4D5 did not result in outgrowth of cells lacking expression of the HER2/neu receptor. These results suggest that 4D5, administered regionally, may palliate LM metastases from HER2/neu-overexpressing breast carcinoma.

Treatment of neoplastic meningeal xenografts by intraventricular administration of an antiganglioside monoclonal antibody, 3F8

Leptomeningeal (LM) neoplastic metastases are painful, debilitating and inevitably lethal. Intrathecal (IT) anti-tumor antibodies may have therapeutic potential. We evaluated 3F8, an anti-G(D2) murine IgG(3) monoclonal antibody (MAb) in the treatment of human melanoma (SKMEL-1) and neuroblastoma (NMB7) xenografts in athymic rats. Both tumors were lysed efficiently in vitro by 3F8 in the presence of rat neutrophils or rat complement. Antibody-dependent cellular cytotoxicity (ADCC) was not augmented by recombinant human GM-CSF (rhGM-CSF), rhG-CSF, recombinant rat MIP-2 (rrMIP-2) or lipopolysaccharide (LPS). In vivo, continuous intraventricular administration of 3F8 and LPS prevented tumor engraftment, retarded tumor growth and eradicated 3-day-old established xenografts whereas 3F8 alone, LPS alone or F(ab)'(2) plus LPS had no or only marginal effects. Tumor establishment in brain was completely prevented in 36% of animals implanted with SKMEL-1 and 65% of animals implanted with NMB7. Twenty percent of established xenografts around the brain were eradicated but all animals had persistent tumor in the lumbosacral meninges despite treatment. Continuous intraventricular infusion of LPS produced a variable polymorphonuclear (PMN) pleocytosis that was dose-dependent. Continuous intraventricular infusion of 3F8 produced immunohistochemically detectable attachment to 86% of persistent brain deposits of tumor but <1% of spinal lumbosacral deposits. We conclude that regional therapy with anti-G(D2) MAb could target neutrophils to inhibit LM tumor growth. However, optimal activation and mobilization of neutrophils into the cerebrospinal fluid (CSF) and improved penetration of MAb to tumor sites remain critical variables.

Pharmacokinetics and dose estimates following intrathecal administration of 131I-monoclonal antibodies for the treatment of central nervous system malignancies

PURPOSE

Treatment of malignant disease in the central nervous system (CNS) with systemic radiolabeled monoclonal antibodies (MoAbs) is compromised by poor penetration into the cerebrospinal fluid (CSF), limited diffusion into solid tumors, and the generation of anti-mouse antibodies. To attempt to avoid these problems we have treated patients with diffuse neoplastic meningitis with radioimmunoconjugates injected directly into the intrathecal space.

METHODS AND MATERIALS

Tumor-specific MoAbs were conjugated to Iodine-131 (131I) (629-3331 MBq) by the Iodogen technique, and administered via an intraventricular reservoir. A clinical response rate of approximately 33% was achieved, with better results in more radiosensitive tumors. Here, we present detailed pharmacodynamic data on patients receiving this intracompartmental targeted therapy.

RESULTS

Elimination from the ventricular CSF appeared biphasic, with more rapid clearance occurring in the first 24 h. Radioimmunoconjugate entered the subarachnoid space and subsequently the vascular compartment. From this information, the areas under the effective activity curves for ventricular CSF, blood, and subarachnoid CSF were calculated to permit dosimetry. Critical organ doses were calculated using conventional medical internal radiation dose (MIRD) formalism. Where available, S-values were taken from standard tables. To calculate the doses to CSF, brain, and spinal cord, S-values were evaluated using the models described in the text.

CONCLUSION

A marked advantage could be demonstrated for the dose delivered to tumor cells within the CSF as compared to other neural elements.

[Determination of IgG subclass antibodies to the basic myelin protein in patients with multiple sclerosis]

The aim of the study was to determine IgG subclasses of MBP antibodies in patients with multiple sclerosis. The enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies against human IgG subclasses was applied. Anti-MBP antibodies were found in the CSF of 16% and in the sera of 20% patients with MS. MBP antibodies belonged to IgG1, IgG2 and IgG3 subclasses (in the CSF) and to IgG1 and IgG3 subclasses (in the sera). The role of MBP antibodies in context of their IgG subclasses distribution is discussed.

Pharmacokinetics and toxicology of immunotoxins administered into the subarachnoid space in nonhuman primates and rodents

Immunotoxins have been suggested as possible therapeutic agents in patients with leptomeningeal carcinomatosis. The pharmacokinetics, stability, and toxicity of immunotoxins injected into the i.t. space were examined in rats and rhesus monkeys. Monoclonal antibodies specific for the human (454A12 and J1) and rat (OX26) transferrin receptors were coupled to recombinant ricin A chain. In monkeys, the maximally tolerated dose of the anti-human transferrin receptor immunotoxin (454A12-rRA) was a dose that yielded a nominal cerebrospinal fluid (CSF) concentration of approximately 1.2 x 10(-7) M. In rats, the 10% lethal dose (LD10) of the anti-human transferrin receptor immunotoxin was a dose yielding a nominal CSF concentration of 8.8 x 10(-7) M whereas the LD10 of the anti-rat transferrin receptor immunotoxin (OX26-rRA) was a dose yielding a nominal CSF concentration of 1.2 x 10(-7) M. Thus, the species-relevant antibody resulted in toxicity at a concentration one-seventh that of the immunotoxin with the irrelevant antibody. A comparison of the area under the concentration curve at the LD10 for rats with the area under the concentration curve at the maximally tolerated dose in monkeys and humans shows that the species-relevant immunotoxin was a better predictor of the toxic dose of the anti-transferrin receptor immunotoxin in humans than the irrelevant immunotoxin. The pharmacokinetics of the 454A12-rRA immunotoxin within the CSF of monkeys showed a biphasic clearance with an early-phase half-life of 1.4 h and a late phase half-life of 10.9 h. The clearance was 4.4 ml/h or approximately twice the estimated clearance due to bulk flow of CSF. Loss by degradation was ruled out because immunoblot analysis showed that the immunotoxin was stable for up to 24 h after administration. Possible losses in addition to sampling include diffusion into brain tissue and transcapillary permeation. The apparent volume of distribution was 10.1 ml or approximately three-fourths the total CSF volume of the monkey. Dose limiting toxicity corresponded with the selective elimination of Purkinje cells in both rats and monkeys and was manifested clinically as ataxia and lack of coordination. The onset of ataxia in monkeys occurred within 5 days and, in the more mild form, was reversible with time. There was evidence of only minimal inflammation within the CSF, and there were no signs of systemic toxicity. Immunotoxins injected into the subarachnoid space may have potential for treatment of leptomeningeal carcinomatosis.

Meningeal malignant melanoma in a child: immunocytological diagnosis

A 10 year old boy, who was thought to have had a traumatic intracranial hemorrhage, was transferred to our Children's Medical Center. In spite of conservative treatment, he developed dysarthria, systemic convulsions, unconsciousness, quadriplegia, and consecutive paralysis of the cranial nerves. Magnetic resonance imaging scans demonstrated areas of increased signal intensity around the brain stem. The cerebrospinal fluid (CSF) contained a few large cells with abundant melanin-like granules, and numerous bizarre cells. The latter were considered to be malignant melanoma cells on immunocytological examination. Chemotherapy with dimethyltriazenoimidazole carboxamide (DTIC) and interferon beta (IFN-beta) was ineffective and he expired. Autopsy revealed diffuse infiltration of malignant melanoma cells into the meninges. We think that immunocytological examination of CSF is advisable for correct and rapid diagnosis.

Monoclonal immunoglobulin bands in the cerebrospinal fluid

Isoelectric focusing and immunofixation allow the detection of abnormal immunoglobulin bands in the cerebrospinal fluid (CSF). In normal subjects, the immunoglobulins in the CSF are derived from serum. In inflammatory disorders of the nervous system, there may be intrathecal immunoglobulin synthesis usually seen as oligoclonal bands confined to the CSF. Monoclonal immunoglobulin bands in the CSF are not common. We surveyed 1490 CSF samples, and found that a total of nine had a monoclonal immunoglobulin band and that in three this was not present in the serum. Of these three, one patient had chronic inflammatory demyelinating polyneuropathy and the antibody may have been secreted by lymphocytes which had infiltrated the nervous system. The other patients had either lymphoma or lymphomatoid granulomatosis within or adjacent to the nervous system and the monoclonal immunoglobulin was probably secreted by B lymphocytes within those lesions.

[Cerebrospinal fluid cytology--a valuable diagnostic method in various neurologic problems]

Cytological examination of cerebrospinal fluid can provide vital diagnostic information, particularly in inflammatory and neoplastic disorders of the nervous system. Not only can the cause of a pleocytosis be established but cytological abnormalities can also be detected in cases where the cell count is normal. Monoclonal antibodies can be used for the characterisation of leukaemic cells.

Quantitative distribution of 131I-labelled monoclonal antibodies administered by the intra-ventricular route

In a preliminary study in one patient [111In]DTPA was injected into the lateral ventricle and at the same time [99mT]DTPA into the lumbar sac. The 111In distributed freely throughout the CSF but the concentration of 99mTc in the ventricles remained consistently low. In the second phase of the study three patients with tumours confined to the neuraxis were treated with 20-50 mCi 131I-labelled monoclonal antibodies administered into the lateral ventricle via Ommaya reservoirs. Quantitative distribution of radio-labelled antibody was assessed at intervals up to 8 days post injection. In each case there was rapid distribution to all parts of the neuraxis with 38-68% of total CNS counts remaining in the head and 13-39% in each of the upper and lower half spine areas. The t1/2 for total CNS counts were 31.5, 19.8 and 15.5 h. There was no clear evidence of tumour localization and no neurological toxicity. These patients demonstrate that radiolabelled monoclonal antibodies can be given safely via Ommaya reservoirs and that in order to obtain optimal distribution throughout the CSF this should be the preferred method of administration. Further trials in patients with minimal disease are warranted.

Detection of antigens in Alzheimer cerebrospinal fluid by monoclonal antibodies

Monoclonal antibodies raised against cerebrospinal fluid (CSF) and human ventral forebrain from patients with Alzheimer's disease were tested against CSF pools derived from patients with Alzheimer's disease and normal controls. Antibodies that appeared to distinguish the two pools were subsequently tested against 58 CSF samples from individual Alzheimer patients, normal controls, and individuals with other neurologic diseases. The mean CSF content of two antigens was decreased in patients with Alzheimer's disease compared with controls; the mean CSF content of one of these antigens was also decreased in patients with other neurologic diseases. Although group differences could be detected, the degree of overlap did not follow for the separation of individual patients within these three groups.

In vivo labeling of blood T cells: rapid traffic into cerebrospinal fluid in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS). In MS patients being treated with anti-T11, a murine monoclonal antibody which recognizes the sheep red blood cell receptor, it was found that peripheral blood T cells were labeled in vivo by the antibody. Furthermore, anti-T11 did not lyse cells or enter the cerebrospinal fluid (CSF). In CSF specimens obtained by serial lumbar punctures from patients with progressive MS who received five daily infusions of anti-T11, 70 +/- 12% of the T cells had mouse antibody bound to their surface by 72 to 96 hours. No in vivo staining of CSF T cells was observed in patients infused with anti-T4, a murine monoclonal antibody that was not found to label T cells in vivo. These results demonstrate that there is rapid movement of lymphocytes from the peripheral blood to the CNS in patients with progressive MS. This rapid trafficking of T cells suggests that the ongoing pathological process within the CNS may be closely linked to the peripheral immune system and may have implications for the monitoring and treatment of MS.

Immunologic responses of progressive multiple sclerosis patients treated with an anti-T-cell monoclonal antibody, anti-T12

Twelve patients with progressive MS were treated with a murine IgM pan-T-cell monoclonal antibody reactive against T12, a determinant present on most post-thymic T-cells. Circulating T12+ cells could not be detected from days 1 to 7, although T3+T11+T12- cells appeared by day 3. Human anti-mouse antibodies were detected in 78% of patients by day 7 and correlated with a decrease in anti-T12 MAb blood levels and the reappearance of T12+ cells in the blood. Although there were high levels of anti-T12 MAb in the serum, there were only barely detectable levels in the CSF and no decrease in the proportion of T12+ cells in the CSF with treatment. Immunologic studies demonstrated a decrease of in vitro pokeweed mitogen-driven Ig synthesis on day 3 with an increase on day 10 that consisted in part of human anti-mouse antibodies. Eleven of 12 patients completed therapy. Prednisone was administered with the treatment after mild allergic reactions occurred in the first two patients. Because this was an open phase one study and patients were treated with prednisone, the effect of treatment on the progression of disease is difficult to assess, and no definitive conclusions concerning clinical effects can be made.

Osmotic blood-brain barrier modification: monoclonal antibody, albumin, and methotrexate delivery to cerebrospinal fluid and brain

In the dog, osmotic opening of the blood-brain barrier (BBB) in the posterior circulation via the vertebral artery and in the anterior circulation via the internal carotid artery was utilized to increase the delivery of three substances of varying molecular weight to the central nervous system. The cerebrospinal fluid (CSF) concentration of all three agents dramatically increased after BBB opening. In contrast to methotrexate, Evans blue-albumin and monoclonal antibody (MAb) concentrations in CSF were 6-fold greater when given after posterior rather than anterior circulation BBB opening. Conversely, MAb delivery to brain parenchyma was optimized after osmotic BBB modification via the carotid artery. This suggests that, with higher molecular weight substances, osmotic barrier opening has a differential effect on the blood-brain vs. blood-CSF barriers.

Paraproteins in the spinal fluid of patients with paraproteinemic polyneuropathies

High-resolution agarose gel electrophoresis, combined with immunofixation electrophoresis, was used to detect and identify immunoglobulins in the cerebrospinal fluid of six patients with paraproteinemic polyneuropathy. In four patients with serum IgM kappa monoclonal protein, we found a discrete band in the cerebrospinal fluid identified also as IgM kappa; one patient with serum IgG kappa had an IgG kappa cerebrospinal fluid band, and one patient with serum IgA kappa had an IgA kappa monoclonal band in the cerebrospinal fluid. The permeability of the blood-cerebrospinal fluid barrier was increased 3 to 10 times in all these patients. The findings indicate that in patients with paraproteinemic polyneuropathy, the increased permeability of the blood-cerebrospinal fluid barrier results in influx of serum proteins into the cerebrospinal fluid, including high-molecular-weight IgM. Because monoclonal IgM, unlike monoclonal IgG and IgA, is not found in the cerebrospinal fluid of neurologically intact patients, its presence in the cerebrospinal fluid of patients with paraproteinemias should lead the physician to suspect neurological involvement and can be of diagnostic value.

Cerebrospinal fluid monoclonal gammopathy in multiple myeloma and Waldenström's macroglobulinemia

Serum ratios of monoclonal immunoglobulin (Ig) to total protein, monoclonal immunoglobulin to albumin, CSF/serum Ig-albumin index, and CSF to serum monoclonal immunoglobulin were obtained in 21 patients with multiple myeloma and 2 with Waldenström's macroglobulinemia. Twelve patients (3 with CNS complications) showed CSF monoclonal proteins similar to their serum. CSF IgA levels above 10 mg/dl, IgG levels above 25 mg/dl, CSF-serum IgG ratios above 0.0034 and CSF-serum IgA ratios above 0.0051 were seen in patients with neurologic complications. Our preliminary data may signal early CNS involvement in multiple myeloma.

Impairment of blood-cerebrospinal fluid barrier in multiple sclerosis

The blood-CSF barrier (BCB) function in active multiple sclerosis (MS) was studied by means of CSF proteins analysis using disc electrophoresis and immunofixation. Forty-five CSF samples were obtained by repeat lumbar punctures at various intervals, from four autopsy-proven cases and three male and nine female patients with clinically definite MS. When total protein content was increased, the percentages of prealbumin and tau fraction were decreased significantly in association with the presence of haptoglobin (Hp) polymers in nearly all the samples, as a result of increased permeability of the BCB. Even when the total protein content was normal, Hp polymers were detected in 56% of the samples, and the tau fraction tended to be decreased. Monoclonal immunoglobulin and Hp polymers were both recognized in some cases. The results suggested a more frequent occurrence of BCB impairment in MS than had formerly been revealed by CSF albumin analysis, and accorded with the recent reports of contrast-enhancing lesions of MS brain in computerized tomography.

Breakdown of the blood--cerebrospinal fluid barrier to immunoglobulin in mice injected intracerebrally with a neurotropic influenza A virus. Post-exposure treatment with monoclonal antibody promotes recovery

Mice may be protected from the invariably fatal consequences of intracerebral (i.c.) inoculation of A/WSN influnza virus by intravenous injection with 0.5 mg of virus-specific monoclonal anti-hemagglutinin antibody given 2 days after i.c. challenge. The integrity of the blood-cerebrospinal fluid (CSF) barrier in such mice has been examined by comparing specific immunoglobulin (Ig) titers in serum and CSF. It seems that the process of virus growth results directly in substantial breakdown of the blood-CSF barrier at some time between 63 and 96 h after i.c. exposure to virus. The exogenously administered, virus-specific monoclonal antibody is not obviously involved either in abrogating the integrity of this physiological barrier system or in promoting inflammation. In fact, higher Ig titers are found in CSF for an antibody that does not bind to the virus. This presumably reflects the fact tht virus-infected cells in the central nervous system are adsorbing specific Ig from the CSF.