Phase II screening trial of lithium carbonate in amyotrophic lateral sclerosis: examining a more efficient trial design.

OBJECTIVE: To use a historical placebo control design to determine whether lithium carbonate slows progression of amyotrophic lateral sclerosis (ALS). METHODS: A phase II trial was conducted at 10 sites in the Western ALS Study Group using similar dosages (300-450 mg/day), target blood levels (0.3-0.8 mEq/L), outcome measures, and trial duration (13 months) as the positive trial. However, taking riluzole was not a requirement for study entry. Placebo outcomes in patients matched for baseline features from a large database of recent clinical trials, showing stable rates of decline over the past 9 years, were used as historical controls. RESULTS: The mean rate of decline of the ALS Functional Rating Scale-Revised was greater in 107 patients taking lithium carbonate (-1.20/month, 95% confidence interval [CI] -1.41 to -0.98) than that in 249 control patients (-1.01/month, 95% CI -1.11 to -0.92, p = 0.04). There were no differences in secondary outcome measures (forced vital capacity, time to failure, and quality of life), but there were more adverse events in the treated group. CONCLUSIONS: The lack of therapeutic benefit and safety concerns, taken together with similar results from 2 other recent trials, weighs against the use of lithium carbonate in patients with ALS. The absence of drift over time and the availability of a large database of patients for selecting a matched historical control group suggest that use of historical controls may result in more efficient phase II trials for screening putative ALS therapeutic agents. CLASSIFICATION OF EVIDENCE: This study provided Class IV evidence that lithium carbonate does not slow the rate of decline of function in patients with ALS over 13 months.

Cyclooxygenase-2-positive macrophages infiltrate the Alzheimer's disease brain and damage the blood-brain barrier.

BACKGROUND: Monocyte/macrophages are known to infiltrate the brain of patients with HIV-1 encephalitis (HIVE). In Alzheimer's disease brain, the origin of activated microglia has not been determined. MATERIALS AND METHODS: We employed the antigen retrieval technique, immunocytochemistry, immunofluorescense, and confocal microscopy to identify macrophages and microglia in relation to amyloid-beta plaques and the blood-brain barrier in autopsy brain tissues from patients with Alzheimer's disease (AD) and HIVE. RESULTS: In both conditions, cyclooxygenase-2 positive macrophages and, to a lesser degree, T and B cells infiltrate brain perivascular spaces and neuropil. The macrophages are distinguishable from ramified microglia, and decorate the vessels at the sites of apparent of endothelial tight junction protein ZO-1 disruption. The macrophages also infiltrate amyloid-beta plaques, display intracellular amyloid-beta and are surrounded by amyloid-beta-free lacunae. Furthermore, the macrophages partially encircle the walls of amyloid-beta-containing vessels in amyloid angiopathy, and exhibit intracellular amyloid-beta but not paracellular lacunae. Significantly larger zones of fibrinogen leakage surround the microvessels in HIVE brain tissues compared with AD tissues (P = 0.034), and AD tissues have significantly greater leakage than control tissues (P = 0.0339). The AD group differs from a normal control age-matched group with respect to both the area occupied by CD68 (P = 0.03) and cyclooxygenase-2 immunoreactive cells (P = 0.004). CONCLUSION: In both HIVE and AD, blood-borne activated monocyte/macrophages and lymphocytes appear to migrate through a disrupted blood-brain barrier. The lacunae around macrophages in amyloid-beta plaques but not in vessel walls are consistent with the ability of macrophages to phagocytize and clear amyloid-beta deposits in vitro.

Essential role of HIV type 1-infected and cyclooxygenase 2-activated macrophages and T cells in HIV type 1 myocarditis.

HIV-1 cardiomyopathy has become a major cause of death in AIDS patients, but its pathogenesis is unclear. We used an antigen retrieval technique and immunostaining to investigate the hearts of 15 AIDS patients, of whom 3 had dilated cardiomyopathy. Immunocytochemistry shows infiltration of the left ventricular myocardium with mononuclear cells, ranging from minimal to diagnostic of myocarditis. The infiltrates include macrophages and CD3(+) and CD8(+) T cells. The tight junction protein ZO-1 is disrupted at the site of monocyte-macrophage vascular penetration and the coronary vessels show fibrinogen leakage in the hearts of AIDS patients, but not in the normal heart. A subset of infiltrating macrophages is doubly positive for cyclooxygenase 2 (COX-2) and inducible nitric oxide synthase. HIV-1 peptides gp120 and Nef are expressed in macrophages and T cells, but not in cardiomyocytes. COX-2 is expressed by both gp120-positive and gp120-negative macrophages. The hearts of AIDS patients separate into those showing minimal infiltrates with low COX-2 expression and those with dense infiltrates and high COX-2; all failing hearts are in the latter group. These data suggest that COX-2-activated and HIV-1-infected monocyte-macrophages and T cells play a crucial role in the progression of HIV-1 myocarditis to HIV-1 cardiomyopathy.

HIV-1 penetrates coronary artery endothelial cells by transcytosis.

BACKGROUND: The pathogenesis of HIV-1-related cardiomyopathy is poorly understood, but HIV-1 has been detected in cardiomyocytes. Whether HIV-1 penetrates into the myocardium by infection of coronary artery endothelial cells (CAEC) or using transcellular or paracellular routes across CAEC has not been resolved. MATERIALS AND METHODS: A model of the CAEC barrier was constructed with primary CAEC (derived from human coronary vessels). Polymerase chain reaction (PCR) assay, infectious assay, and immunofluorescence were employed to show abortive nature of HIV-1 infection of CAEC. Tight junction (TJ) and cell adhesion proteins were visualized by immunofluorescence. The time course of HIV-1 invasion was measured by HIV-1 RNA assay. Inulin permeability assay determined paracellular leakage. Transmission electron microscopy demonstrated virus-induced endothelial vacuolization. RESULTS: Despite a strong display on CAEC of CXCR4 and a lesser expression of CCR3 and CCR5, HIV-1 did not productively replicate in CAEC, as shown by infectious assay, immunofluorescence, and electron microscopy. HIV-1 infection of CAEC was abortive with minimal reverse transcription of strong stop DNA and pol but not full-length or two LTR DNA circles. Upon infection of the model with 1 million RNA copies of HIV-1JR-FL, virus penetration 2 hr postinfection (PI) was negligible but increased by 1,750% 24 hr PI. The paracellular permeability increased during this period by only 25%. Neither AOP-RANTES nor v-MIPII significantly reduced HIV-1JR-FL invasion. Virus infection did not alter the integral TJ protein occludin and the TJ-associated protein ZO-1. HIV-1 exposed CAEC and brain microvascular endothelial cells (BMVEC) developed extensive cytoplasmic vacuolization with retroviral-like particles in the vacuoles. CONCLUSIONS: The endothelium is not an impenetrable barrier to HIV-1. The virus opens a transcellular route across coronary and brain endothelia in cytoplasmic vacuoles.

Cocaine enhances brain endothelial adhesion molecules and leukocyte migration.

Leukocyte infiltration of cerebral vessels in cocaine-associated vasculopathy suggests that cocaine may enhance leukocyte migration. We have investigated cocaine's effects on leukocyte adhesion in human brain microvascular endothelial cell (BMVEC) cultures and monocyte migration in an in vitro blood-brain barrier (BBB) model constructed with BMVEC and astrocytes. Cocaine (10(-5) to 10(-9) M) enhanced adhesion of monocytes and neutrophils to BMVEC. In the BBB model, cocaine (10(-4) to 10(-8) M) enhanced monocyte transmigration. Cocaine increased expression of endothelial adhesion molecules, intercellular adhesion molecule-1 (ICAM-1, CD54), vascular cell adhesion molecule-1 (VCAM-1), and endothelial leukocyte adhesion molecule-1 (ELAM-1) on BMVEC. The peak effect on ICAM-1 expression was between 6 and 18 h after treatment. ICAM-1 was increased by cocaine in BMVEC, but not in human umbilical vein endothelial cells, and the enhancement was greater in a coculture of BMVEC with monocytes. ICAM-1 expression was enhanced by a transcriptional mechanism. Polymyxin B inhibited up-regulation of adhesion molecules by LPS but not by cocaine. In LPS-activated BMVEC/monocyte coculture, cocaine increased secretion of tumor necrosis factor-alpha and interleukin-6. Taken together, these findings indicate that cocaine enhances leukocyte migration across the cerebral vessel wall, in particular under inflammatory conditions, but the effects are variable in different individuals. Cocaine's effects are exerted through a cascade of augmented expression of inflammatory cytokines and endothelial adhesion molecules. These could underlie the cerebrovascular complications of cocaine abuse.

Amyloid-beta induces chemokine secretion and monocyte migration across a human blood--brain barrier model.

BACKGROUND: Aside from numerous parenchymal and vascular deposits of amyloid beta (A beta) peptide, neurofibrillary tangles, and neuronal and synaptic loss, the neuropathology of Alzheimer's disease is accompanied by a subtle and chronic inflammatory reaction that manifests itself as microglial activation. However, in Alzheimer's disease, alterations in the permeability of the blood-brain barrier and chemotaxis, in part mediated by chemokines and cytokines, may permit the recruitment and transendothelial passage of peripheral cells into the brain parenchyma. MATERIALS AND METHODS: Human monocytes from different donors were tested for their capacity to differentiate into macrophages and their ability to secrete cytokines and chemokines in the presence of A beta 1-42. A paradigm of the blood-brain barrier was constructed utilizing human brain endothelial and astroglial cells with the anatomical and physiological characteristics observed in vivo. This model was used to test the ability of monocytes/macrophages to transmigrate when challenged by A beta 1-42 on the brain side of the blood-brain barrier model. RESULTS: In cultures of peripheral monocytes, A beta 1-42 induced the secretion of proinflammatory cytokines TNF-alpha, IL-6, IL-1 beta, and IL-12, as well as CC chemokines MCP-1, MIP-1 alpha, and MIP-1 beta, and CXC chemokine IL-8 in a dose-related fashion. In the blood-brain barrier model, A beta 1-42 and monocytes on the brain side potentiated monocyte transmigration from the blood side to the brain side. A beta 1-42 stimulated differentiation of monocytes into adherent macrophages in a dose-related fashion. The magnitude of these proinflammatory effects of A beta 1-42 varied dramatically with monocytes from different donors. CONCLUSION: In some individuals, circulating monocytes/macrophages, when recruited by chemokines produced by activated microglia and macrophages, could add to the inflammatory destruction of the brain in Alzheimer's disease.

Cocaine enhances monocyte migration across the blood-brain barrier. Cocaine's connection to AIDS dementia and vasculitis?

Cocaine has wide-ranging effects on the immune and neuroendocrine systems (Fiala et al., 1996) resembling an inflammatory "stress" response with upregulation of pro-inflammatory cytokines and stimulation of the HPA axis (Gan et al., 1997). Cocaine abuse has also been associated with vascular pathology, including vasculitis, vasospasm and hemorrhage. These effects suggest that cocaine could perturb the function of endothelial cells, including the blood-brain barrier, and influence the progression to AIDS in HIV-infected individuals (Shapshak et al., 1997; Goodkin et al., 1997). In order to understand clinical consequences of cocaine abuse, it is important to gain insight into molecular and cellular basis of cocaine's effects on immune and endothelial cells. Cocaine's in vitro effects on (a) permeability, (b) immune cell migration, (c) adhesion molecules, and (d) cytokine expression were investigated in a blood-brain barrier model constructed with brain microvascular endothelial cells and fetal astrocytes with the following results: (a) cocaine and tumor necrosis factor-alpha (TNF-alpha) increased the model's permeability to inulin similarly in a dose-responsive fashion; (b) cocaine (10(-4) to 10(-8_ M) enhanced monocyte migration across the barrier with the maximum increase, approximately 100%, by 10(-5) M cocaine; (c) cocaine treatment also increased the expression of endothelial adhesion molecules, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecules-1 (VCAM-1) and platelet/endothelial cell adhesion molecule-1 (PECAM-1); (d) although the cocaine in vitro effects on cytokine production by mononuclear cells have been difficult to assess due to a heterogeneity in the degree of responsiveness between individuals, the data suggest that mononuclear cells from cocaine addicts are sensitized to in vitro cocaine challenge with hypersecretion of inflammatory cytokines. Cocaine's in vivo manifestations are compatible with these in vitro effects: (A) chronic cocaine treatment of rats significantly increased rolling white blood cell flux, leukocyte-endothelium adhesion, and ICAM-1 expression in the mesentery (House et al., 1996); (B) cocaine injection to cocaine-dependent subjects tipped the balance of cytokine secretion by mononuclear cells to Th1-type (Gan et al., 1997), and (C) cocaine injection stimulated the hypothalamic-pituitary axis (HPA) to increase both anti- and pro-inflammatory hormonal secretion. Collectively, these results suggest that the immune effects of cocaine on endothelial, immune and neuroendocrine cells impair the function of the blood-brain, barrier, increase cell emigration from the blood vessels, in particular into the brain, and may cause vasculitis. These effects could also increase importation of HIV-1 into the brain.

Cocaine opens the blood-brain barrier to HIV-1 invasion.

Cocaine abuse has been associated with vasculitis and stroke, and is suspected to influence the progression of AIDS dementia. Cocaine may enhance HIV-1 neuroinvasion by actions directed at the blood-brain barrier. HIV-1 appears to penetrate the human brain microvascular endothelial cell barrier by a paracellular route breached by tumor necrosis factor-alpha (TNF-alpha). Cocaine's effects on the blood-brain barrier were investigated using human brain microvascular endothelial cells and peripheral blood monocytes. Cocaine (10(-5) M and 10(-6) M) increased molecular permeability of the barrier and viral invasion by the macrophage-tropic HIV-1(JR-FL) into the brain chamber. Cocaine also augmented apoptosis of brain endothelial cells and monocytes, increased secretion of four chemokines (interleukin-8, interferon-inducible protein-10, macrophage inflammatory protein-1alpha, and monocyte chemoattractant protein-1) and the cytokine, TNF-alpha, by human monocytes. TNF-alpha enhanced invasion of the brain compartment by macrophage-tropic, lymphotropic, and bitropic HIV-1 strains. These data indicate that HIV-1 neuroinvasion can be increased by (a) cocaine's direct effects on brain microvascular endothelial cells and (b) paracrine effects of cocaine-induced pro-inflammatory cytokines and chemokines on the blood-brain barrier.

Augmentation of natural antiganglioside IgM antibodies in lower motor neuron disease (LMND) and role of CD5+ B cells.

IgM antibodies directed against neuronal gangliosides GM1, GM2, GD1a, GD1b and GT1b occur in normal individuals and their level significantly decreases with age. Patients with lower motor neuron disease (LMND) produce high levels of these autoantibodies. AntiGM1 IgM is selectively augmented. In these patients, the CD5+ (B1) and CD5- (B2) subsets of B cells are not distinct entities but range from those without detectable CD5 marker to those with high CD5+ expression. B1 B cells were sorted to homogeneity, but B2 B cell cannot be isolated to homogeneity because of the presence of B1 cells with low CD5 expression. In short term cultures both the subsets produced IgM antibodies, but the antibodies reacted better with desialylated GM1 than with GM1. Cycloheximide (Cx) (0.35 mM) largely blocked IgM synthesis of the B1 B cells but inhibition of the B2 B cells was incomplete, possibly due to shedding of cytophilic antibodies as well as to the presence of B1 phenotype with loss of CD5 expression. CD5+ B cells may be involved in the production of antiglycolipid IgM.

TNF-alpha opens a paracellular route for HIV-1 invasion across the blood-brain barrier.

BACKGROUND: HIV-1 invades the central nervous system early after infection when macrophage infiltration of the brain is low but myelin pallor is suggestive of blood-brain-barrier damage. High-level plasma viremia is a likely source of brain infection. To understand the invasion route, we investigated virus penetration across in vitro models with contrasting paracellular permeability subjected to TNF-alpha. MATERIALS AND METHODS: Blood-brain-barrier models constructed with human brain microvascular endothelial cells, fetal astrocytes, and collagen I or fibronectin matrix responded in a dose-related fashion to cytokines and ligands modulating paracellular permeability and cell migration. Virus penetration was measured by infectious and quantitative HIV-1 RNA assays. Barrier permeability was determined using inulin or dextran. RESULTS: Cell-free HIV-1 was retained by the blood-brain barrier with close to 100% efficiency. TNF-alpha increased virus penetration by a paracellular route in a dose-dependent manner proportionately to basal permeability. Brain endothelial cells were the main barrier to HIV-1. HIV-1 with monocytes attracted monocyte migration into the brain chamber. CONCLUSIONS: Early after the infection, the blood-brain barrier protects the brain from HIV-1. Immune mediators, such as TNF-alpha, open a paracellular route for the virus into the brain. The virus and viral proteins stimulate brain microglia and macrophages to attract monocytes into the brain. Infiltrating macrophages cause progression of HIV-1 encephalitis.

Guillain-Barré syndrome after combined tetanus-diphtheria toxoid vaccination.

Guillain-Barré syndrome (GBS), an acute inflammatory polyradiculoneuropathy, is often associated with an antecedent factor, such as an infection, surgery, systemic malignancy, or vaccination. The first case of GBS following a vaccination with combined tetanus-diphtheria toxoid is reported.

Physiologic motion after laryngeal nerve reinnervation: a new method.

In this study a new method of reinnervation for unilateral recurrent laryngeal nerve paralysis was performed in canines, producing physiologic vocal fold motion in each of a small series of animals. During the procedure the left anterior division of the recurrent laryngeal nerve was reinnervated with axons from the thyroarytenoid branch of the contralateral recurrent laryngeal nerve. The posterior branch of the left recurrent laryngeal nerve was divided and sutured to the ansa cervicalis to maintain tone in the posterior cricoarytenoid muscle. In all four animals, the right distal vocalis stump was reinnervated with an ansa cervicalis nerve branch. After 3 months physiologic vocal fold motion and electromyographic activity could be demonstrated during mechanical stimulation of the supraglottis (adduction) and during tracheostomy obstruction (abduction). Acoustic data revealed improvement of jitter, shimmer, signal-to-noise ratio, and vocal efficiency in reinnervated animals compared with paralyzed canines before treatment, although the results lacked statistical significance. This approach to the rehabilitation of unilateral vocal fold paralysis is discussed.

Suramin in hormone-refractory metastatic prostate cancer: a drug with limited efficacy.

PURPOSE: To confirm the previously reported high response rates and prolonged survival in hormone-refractory prostate cancer treated with suramin. PATIENTS AND METHODS: Thirty-six eligible patients with hormone-refractory prostate cancer with either measurable disease or bone disease only and a prostate-specific antigen (PSA) level greater than 50 ng/mL were enrolled. Treatment consisted of two 8-week courses of outpatient-based therapy with an interposed rest period. A bayesian adaptive control strategy and a three-compartment pharmacokinetic model that accommodates clearance changes was used to guide individual dosing. A rapid infusion of 1,000 mg/m2 suramin was followed by five daily infusions that targeted 285 micrograms/mL peak plasma levels during the first week. All patients received concomitant hydrocortisone. For the next 7 weeks, patients received one to two doses per week that targeted levels in the 150 to 285 micrograms/mL range and integrated weekly averages of 200 ug/mL. RESULTS: Nine patients (28%) had a partial response to suramin based on a > or = 50% decrease in PSA levels coupled with either relief of bone pain or by a 50% decrease in measurable disease. The median overall survival time for all patients is 31 weeks (95% confidence interval [CI], 23 to 51). Treatment was generally well tolerated, with fatigue being the most common significant toxicity, but fatal idiosyncratic myelosuppression (grade V) was observed in one patient. CONCLUSION: Using this dosing schedule, suramin has limited activity against hormone-refractory metastatic prostate cancer. Recent data suggest that hydrocortisone administered with suramin may be partly responsible for the benefit attributed to the drug. Although a small cohort of patients appeared to benefit, we were unable to confirm the previously reported high rate of activity and durability of remission using this agent.

Function of the interarytenoid muscle in a canine laryngeal model.

The interarytenoid (IA) muscle has rarely been studied in the living larynx. In this work, the role of the IA muscle in phonation was studied in three dogs by means of an in vivo phonation model. The isolated action of the IA muscle was studied by sectioning and stimulating its nerve branch. As IA activity increased, subglottic pressure increased significantly until a plateau was reached. In the absence of superior laryngeal nerve stimulation, the fundamental frequency rose with increasing IA activity. In the presence of superior laryngeal nerve stimulation, however, no significant change in fundamental frequency was observed with increasing IA activity. Measurement of adductory force demonstrated that the IA muscle adducts primarily the posterior vocal fold. In this canine model, phonation was not possible without IA stimulation, owing to a large posterior glottic chink.

Factors affecting the fine specificity and sensitivity of serum antiganglioside antibodies in ELISA.

The major problem associated with ELISA of serum antiganglioside antibodies is the high background values (absorbancy of sera added to wells without ganglioside), which interfere with the accurate assessment of the fine specificity and sensitivity of these antibodies. This investigation identifies factors elevating the background values and/or decreasing the fine specificity, and describes strategies to minimize their influence. Using sera of neuropathy and melanoma patients, we found that highest background values were observed with the polystyrene 'tissue culture' microtiter plates; of the various 'non-tissue culture' microtiter plates tested, the lowest background values (> 0.060) were observed with Costar-3590 (H), Immunolon-3, Immunolon-1, Falcon-3915 (in increasing order). Background artifact of polystyrene microtest plates was significantly reduced by gamma irradiation (at 40 kRad) and/or use of detergent Tween-20 (0.1%) in the washing step. Even after controlling the background values, the fine specificity, namely, the ability of the antibody to distinguish between the target epitope of an antigen and epitopes of related antigens (when moles of antigen/well is constant) varied with different microtiter plates. Using sera with high affinity and specificity for GM2, GD3 or GM3, we observed that Immunolon-1, Immunolon-3 and particularly Falcon-3915 were superior for assessing the abilities of the antibodies to distinguish closely related epitopes found on other gangliosides. The reactivity of antiganglioside antibodies was more consistent after detergent treatment. The reactivity of antibodies to GD3 is significantly enhanced after treatment with Tween-20, but that of antibodies reacting to GM1 and GM2 is reduced. Fine specificity of the antiglycolipid antibodies was resolved better by coating glycolipids in mol/well rather than by weight/well. Based on these results, a protocol for a sensitive and reproducible ELISA for serum antiganglioside antibodies is recommended. The protocol takes into consideration the suitability of polystyrene plates, coating based on the number of molecules, pertinency of the solvent for coating, use of human serum albumin for blocking, dilution and washing steps and use of 0.1% Tween-20 to further minimize the background absorbancy.

Bilateral thyroarytenoid denervation: a new treatment for laryngeal hyperadduction disorders studied in the canine.

Adductor spasmodic dysphonia is a vocal disorder of uncertain etiology with no satisfactory long-term treatment. Recently, injection of botulinum toxin (Botax) into the thyroarytenoid (TA) muscle has been used as an effective temporary treatment. A surgical counterpart to bilateral TA Botox injection is described in this article. Bilateral thyroarytenoid denervation was performed through a window in the thyroid cartilage in seven canines, including four that were studied 3 months after the procedure. No serious complications occurred in the animals, each maintaining full vocal fold abduction and adduction. In all cases, anticipated physiologic changes in laryngeal function were observed, including the inability to generate high subglottic pressures during high levels of laryngeal nerve (RLN) stimulation. In two of the surviving animals, the ansa cervicalis was used to reinnervate the TA muscle, thereby preventing the possibility of reinnervation from the proximal RLN stump while limiting TA atrophy and fibrosis. Bilateral TA denervation represents a hopeful new long-term approach to spasmodic dysphonia treatment.

Autoimmune disease and the nervous system. Biochemical, molecular, and clinical update.

Autoimmunity in the central and peripheral nervous system can manifest as the result of cellular or humoral immune responses to autoantigens. There is evidence that multiple sclerosis is a cell-mediated autoimmune disease of the central nervous system in which both myelin and the cell that produces the myelin are destroyed. Diseases such as acute inflammatory demyelinating polyneuropathy (also called Guillain-Barré syndrome) and myasthenia gravis are considered antibody-mediated diseases of the peripheral nervous system and neuromuscular junctions, respectively. We review these diseases and explore mechanisms of immune-mediated destruction of these nervous system components. We specifically focus on one effective therapy aimed at countering the immune attack, that of thymectomy in patients with myasthenia gravis.

Monoclonal IgM antibodies from cytomegalovirus-infected mice recognize the GlcNAc-containing receptor determinant of murine CMV as well as neutralizing anti-CMV IgG antibodies.

This study examines monoclonal antibodies derived from mice at different time points after infection with attenuated murine cytomegalovirus (MCMV). The antibodies obtained from mice at 3 weeks p.i. were of IgG type (designated V-antibodies) and several could neutralize the virus. Those obtained at 5 weeks p.i. were of the IgM class (designated R-antibodies), bound to uninfected (MEF, mouse embryo fibroblast) cells, and thereby blocked MCMV plaque formation. In ELISA, the IgM monoclonals (R-antibodies) bound to GalB1-3GlcNAc and GalB1-4GlcNAc, the receptor determinants for MCMV. Similarly, these GlcNAc-containing residues blocked the binding of purified IgM monoclonal antibodies (MAbs) to MEF. The R- and V-series of antibodies showed mutual binding activities; for example, IgM MAb R-2D8 bound specifically to four (V-8C4, V-1C7, V-8C7, V-9C5) of six neutralizing IgG MAbs in ELISA. The same neutralizing IgG MAbs bound to antireceptor IgM antibodies in an immunoblot assay. This suggests that the IgM monoclonals directed against the known cell surface receptor determinant are anti-idiotypic antibodies against neutralizing antiviral IgG antibodies. The neutralizing antiviral IgG MAbs bound to 60- and 66-kDa MCMV polypeptides on Western blots, suggesting that these viral polypeptides may be important in MCMV binding to this receptor. The R-series might represent anti-idiotype antibodies capable of down-regulating antiviral V-antibodies and may also represent a mechanism for the induction of IgM autoantibodies directed at cell surface glycolipids present in autoimmune CMV-associated neuropathies.