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Biomedical subjects

J N Whitaker

Publications and source records attributed to J N Whitaker.

At least 73 records · Page 4Linked to original sources
PubMed1995

Urinary myelin basic protein-like material as a correlate of the progression of multiple sclerosis.

In the multicenter, randomized, placebo-controlled trial of alternate-day injections of recombinant interferon beta-1b in relapsing-remitting multiple sclerosis (MS), urine specimens were collected periodically from all patients (n = 64) in two of the clinical test sites over the 2 years of the study. Urine specimens were also collected over two consecutive 24-hour periods from 43 patients from a third center. Urine samples were assayed for their content of myelin basic protein-like material (MBPLM), the level of which was correlated with clinical changes, cranial magnetic resonance imaging results, and the development of progressive disease. Concordant changes in creatinine values affected some of the relationships of MBPLM. The level of urinary MBPLM correlated with a chronic progressive course and with the number of lesions and the total lesion area on cranial magnetic resonance images. A rise in the level of urinary MBPLM appeared to antedate the clinical transition from a relapsing-remitting to a chronic progressive course. By chance, the randomized entry of patients led to significant differences in urinary MBPLM levels among the three treatment groups, thus precluding correlation studies of treatment effects. However, the patient group from which 24-hour specimens were collected showed that the patients with relapsing-remitting MS changing to a chronic progressive course, and more specifically, those patients with chronic progressive MS receiving placebo, had the highest values of urinary MBPLM. These findings indicate that urinary MBPLM may offer an objective test and possibly serve as a surrogate marker for detecting or predicting the failure of remission or the transition to a progressive phase of MS.

Analysis of Variance↗
PubMed1995

Urinary excretion of NG-dimethylarginines in multiple sclerosis patients: preliminary observations.

The concentrations of NG,N'G-dimethylarginine [Me2(sym)Arg] and NG,NG-dimethylarginine [Me2(asym)Arg] were determined in the urine samples from multiple sclerosis (MS) and control subjects, using a highly sensitive HPLC post-column o-phthaldialdehyde derivatization method. The presence of approximately equal amounts of both dimethylarginine isomers, of Arg concentration nearly half of Me2Arg, and of the undetectable amount of NG-monomethylarginine were the characteristic urinary excretion pattern in all human samples studied. The urinary excretion of Me2(asym)Arg and Me2(sym)Arg from MS (n = 9) and control (n = 7) were analyzed: the mean values from the samples were approximately 20% (for all MS) and 33% (for chronic-progressive MS) lower than those from the control for both dimethylarginine-derivatives when compared to the respective compounds. Although there were contrasting trends between controls and MS patients in the relationship of urinary NG-dimethylarginines and myelin basic protein like material (MBPLM), the correlations were not significant. Differences in the ratios of the concentrations of the two dimethyl derivatives, Me2(sym)Arg/Me2(asym)Arg, were not significantly different between MS and control groups. These findings warrant further investigation of possible links between urinary excretion of NG-dimethylarginine and MBPLM in MS. The possible significance of myelin metabolism in relation to urinary NG-dimethylarginines in MS is discussed.

Arginine↗
PubMed1995

The effects of citrullination or variable amino-terminus acylation on the encephalitogenicity of human myelin basic protein in the PL/J mouse.

The post-translational modifications of myelin basic protein (MBP) in the form of citrullination and varying length of amino-terminus acylation may modify the biological functions and immunological features of MBP. Both modifications influence the reaction of antibodies and specific T cells recognizing MBP. The present study was undertaken to compare the encephalitogenicity of the citrullinated isomer of MBP (MBP-C8) with the unmodified isomer of MBP (MBP-C1) and to determine if the length of amino-terminal acylation of MBP peptide 1-21 altered an encephalitogenic epitope. MBP-C8, whether from patients with or without multiple sclerosis (MS), and MBP-C1 could induce active experimental allergic encephalomyelitis (EAE) in PL/J mice. A trend of reduced severity of EAE was observed in MBP-C8-injected animals. An increase in the length of amino-terminus fatty acid decreased the encephalitogenicity of MBP peptide 1-21 for both active and adoptive EAE in PL/J mice. Only lymph node cells sensitive to MBP peptide acetyl 1-21 and butyl 1-21 could transfer clinical EAE. In adoptive EAE, MBP peptides hexyl and octyl 1-21 induced moderate histopathological but no clinical change, whereas MBP peptide decyl 1-21 caused neither. A broadening in the antibody response could be detected in the sera of mice with active EAE induced by MBP-acylated peptides 1-21. Our findings demonstrate that encephalitogenicity is retained in the presence of citrullination but that the length of amino-terminus acylation diminishes the encephalitogenicity of MBP in the PL/J mouse.(ABSTRACT TRUNCATED AT 250 WORDS)

Acylation↗
PubMed1995

Outcomes assessment in multiple sclerosis clinical trials: a critical analysis.

The feasibility and precision of clinical trials for the treatment of MS must be improved. Subsequent to the approval by the Food and Drug Administration of the United States of interferon beta-Ib as a safe and effective, though not curative, treatment for relapsing-remitting MS, the testing of other agents in this disease has been undertaken or is anticipated. This report summarises the discussions and recommendations of an international workshop held to review critically the elements of current MS therapeutic trials and to identify the most important aspects of clinical evaluation, study design and data analysis that would allow agents for MS to be tested as accurately, rapidly and economically as possible. While acknowledging the many uncertainties about the pathophysiology and natural history of MS, the workshop participants made recommendations about the preferred components to be used in the design of trials which may be different depending on the treatment goal and agent studied. It was concluded that the formulation of a useful clinical trial design must be based on specific guidelines for clinical scales and imaging for which task forces were recommended and subsequently appointed.

Clinical Trials as Topic↗
PubMed1994

A cross-reactive idiotope on T cells from PL/J mice and Lewis rats that recognizes different myelin basic protein encephalitogenic epitopes but is restricted by TCR V beta 8.2.

Encephalitogenic T cells of both PL/J mice and Lewis rats are restricted by TCR V beta 8.2, although they recognize different epitopes in the myelin basic protein (MBP) molecule. We sought the presence of a cross-reactive idiotope (Id) in encephalitogenic T cells of Lewis rats by examining the effects of mAb F30 anti-Id, which recognized a TCR Id in PL/J T cells, on the encephalitogenic LR88L1 cell line derived from Lewis rats and specific for guinea pig MBP peptide 68-88. The LR88L1 cells were I-A restricted and TCR V beta 8.2+, and their proliferation and secretion of IL-2 and TNF-alpha induced by guinea pig MBP peptide 68-88 was inhibited by mAb F30 anti-Id. As shown by FACS analysis and by immunoprecipitation of TCR from radiolabeled LR88L1 cell lysates, the F30 anti-Id bound to the TCRs of V beta 8.2+ LR88L1 cells. In addition, TCR sequences in the F30+ population of LR88L1 cells were the same as those of encephalitogenic Lewis rat T cells published previously. The F30+ LR88L1 cells showed reduced encephalitogenicity compared with F30- or unsorted LR88L1 cells. The mechanism for this reduction by anti-Id probably resulted from the induction of anergy, in that IL-2 reversed the anti-Id effect. The control LR99L1 T cell line, also encephalitogenic, but specific for MBP peptide 87-99 and I-E, and not TCR V beta 8.2 restricted, failed to react with, or have its cytokine secretion inhibited by, mAb F30 anti-Id. These results demonstrate an interspecies cross-reactive Id expressed in common by encephalitogenic T cells that share a similar TCR, although they differ in MBP epitope specificity. These findings suggest that a common Id restricted by TCR, but less restricted by the encephalitogenic epitope, and recognized by the Id-bearing autoreactive T cells may represent an immunotherapeutic approach for treating autoimmune demyelinating diseases.

Amino Acid Sequence↗
PubMed1994

A V lambda x-bearing monoclonal antibody with similar specificity and sequence to encephalitogenic T cell receptors.

The fine specificity of mAb F28C4 to myelin basic protein (MBP), acetyl residues 1-9, has been compared with the previously described specificity of an encephalitogenic T cell clone, PJR-25. F28C4 has been found to express a cross-reactive idiotope (CRI) that is shared with MBP acetyl peptide 1-9-specific TCR. The CRI seems to be located at or near the Ag-combining site of F28C4 and the TCR and, thus, might possibly result from overlapping epitope specificity. We tested the fine epitope specificity of F28C4 by using alanine-substituted peptide analogues and found that residues critical for TCR recognition, Cln3 and Pro6, are also necessary for F28C4 recognition. By using nuclear magnetic resonance, we found that the MBP acetyl peptide 1-9 binds F28C4 in an extended conformation and that the central residues are more tightly bound than the terminal residues, much like the MBP-TCR interaction. Furthermore, sequence homology (75% overall) was found between the regions that contained CDR3 of F28C4 VL and VH and the VDJ junction of the TCR V beta. This homology is not shared by other Ig CDR3 regions and arises, in part, because F28C4 uses an unusual V lambda light chain, V lambda x. Thus, F28C4 shares a CRI with the TCRs, possibly as a result of having similar fine epitope specificity and sequence homology. The anti-CRI mAb can down-modulate experimental allergic encephalomyelitis; thus, it is possible that Abs that are similar to F28C4 may play an important immunoregulatory role in experimental allergic encephalomyelitis in vivo.

Amino Acid Sequence↗
PubMed1994

Correlation of clinical features and findings on cranial magnetic resonance imaging with urinary myelin basic protein-like material in patients with multiple sclerosis.

Immunoreactive material that appears to be a peptide encompassing all or a portion of residues 80 to 89 of myelin basic protein is present in normal unconcentrated urine and is increased in certain patients with multiple sclerosis (MS). Compared with normal controls, urines collected randomly from 158 MS patients or in a clinical research unit from 8 patients with MS had higher mean values of urinary MBP-like material (MBPLM). The level of MBPLM in urine showed no direct relationship to MBPLM in cerebrospinal fluid and did not correlate with clinical relapses of disease. In the other neurological disease control group (26 patients), some patients with other inflammatory diseases, but not stroke or early phase Guillain-Barré syndrome, also showed elevations. Among the subtypes of MS, those with secondary chronic progressive disease had the highest values. Urinary MBPLM showed no definite correlation with or effect of treatment with glucocorticoids and immunosuppressants except that a lower level of urinary MBPLM showed a weak relationship with improvement following treatment with methylprednisolone/prednisone. In a serial study of 8 patients with unenhanced cranial magnetic resonance imaging and 20 patients with gadolinium-enhanced cranial magnetic resonance imaging, urinary MBPLM did not show a direct correlation with new or enhancing lesions. Urinary MBPLM does not parallel acute myelin damage but appears to reflect an ongoing process, possibly linked to attempted efforts at remyelination.

Adult↗
PubMed1994

Rationale for immunotherapy in multiple sclerosis.

The presumed but unspecified immune-mediated basis for the pathogenesis of multiple sclerosis (MS) has led to therapeutic attempts to modify the immune system in general and in selective ways in patients with MS. In general, antiviral, anti-inflammatory, immunosuppressant, and immunomodulatory therapies have been considered. More specifically, these treatments have involved the use of glucocorticoids; immunosuppressant drugs and physical agents such as irradiation; modifications of the immune environment with therapeutic plasma exchange and intravenous immunoglobulin; and more recently, alteration of events surrounding antigen presentation and stages of the immune response of cellular proliferation, recruitment, and infiltration of the central nervous system. The more selective approaches have dealt with attempts to interfere with elements of the trimolecular complex through blocking MHC class II, modifying T-cell receptor functions, interfering with co-stimulatory recognition steps, and altering cytokine effects or lymphocyte adhesion. The rationale for the current therapeutic trials of antigen-driven peripheral tolerance, MHC class II blockade, and immunomodulation, especially with interferon-beta, illustrate the progression from broad immunosuppressive treatment to targeting specific activities of the immune system. The combination of new strategies in immunotherapy and sensitive disease monitoring of their effects should allow for more rapid identification of beneficial and tolerated treatment for MS.

Adjuvants, Immunologic↗
PubMed1994

Comparison of properties of murine monoclonal anti-idiotypic antibodies generated with idiotype-bearing monoclonal antibodies to myelin basic protein peptides or their complementary peptides.

The present study was undertaken to compare the features of monoclonal antibody (mAb) anti-idiotope (Id) induced by complementary peptides, synthesized on the basis of inverted hydropathy for a myelin basic protein (MBP) peptide, or by conventional methodology using Id-bearing antibodies to the same MBP peptide as immunogen. The six reagents studied consisted of mAbs reactive with MBP peptide acetyl 1-9 and MBP peptide 80-89 and anti-Id reagents against these two mAbs prepared by either the complementary peptide or the conventional approach. ELISA, immunoblotting, immunoinhibition of hybridoma cell production of Id-bearing mAb to MBP, and FACS indicated that the anti-Ids generated by either technique were similar although existing in a range reflecting biologic phenomena. mAbs anti-Id prepared by either method continued to show an IgM isotype preference, possibly related to technical considerations, and continued to recognize a cross-reactive Id on the kappa light chain of the mAbs to MBP peptides acetyl 1-9 and 80-89. There was no indication that the anti-Ids prepared by the complementary peptide approach were restrictive or selective in a manner different from those made by the conventional approach.

Amino Acid Sequence↗
PubMed1994

Identification of interactive determinants on idiotypic-anti-idiotypic antibodies through comparison of their hydropathic profiles.

We have written a computer program to aid in the identification of interaction sites between proteins. The program compares the hydropathic profiles of the two interacting proteins and reports sites, demonstrating an exact pattern of inverted hydropathy. If these regions are surface accessible in the folded proteins, they are considered putative binding or docking sites and can be tested as such. In this report, we apply this program to the localization of residues involved in the anti-idiotope of a monoclonal antibody (mAb), F30C7. The anti-idiotope of F30C7 partially resembles the structure of the peptide antigen, human myelin basic protein (MBP) acetyl 1-9, used to elicit the idiotope bearing mAbs (Ab1). The sequences of F30C7 variable regions are compared to the variable regions of Ab1, as well as to the peptide antigen used to elicit F30C7. Sites of hydropathic complementarity in F30C7 with Ab1 that also have sequential homology with MBP 1-9 were located, and a synthetic peptide designed from these sequences was found to structurally resemble MBP 1-9 in that it: (i) inhibited Ab1 binding to MBP 1-9 and (ii) partially inhibited the binding of F30C7 to Ab1. Thus the portion of the anti-idiotope of F30C7 resembling MBP 1-9 was determined with the aid of this program. Other hits between F30C7 and Ab1 also occurred, and future studies will determine whether or not these sites might further contribute to the anti-idiotope.

Amino Acid Sequence↗
PubMed1994

Use of complementary peptides and their antibodies in T-cell-mediated autoimmune disease: experiments with myelin basic protein.

In this article we review the field of idiotype (Id) network and experimental allergic encephalomyelitis, focusing on the generation of monoclonal antibody anti-Id by using complementary peptide and the investigation of anti-Id immunoregulatory effects on immune responses of B and T cells to specific myelin basic protein peptides in vitro and in vivo.

Amino Acid Sequence↗
PubMed1994

Monoclonal and polyclonal antibody responses to the myelin basic protein epitope present in human urine.

The myelin basic protein (MBP)-like material (MBPLM) in human urine is expressed in a cryptic epitope(s) present in MBP peptide 80-89 and absent or inaccessible in intact MBP. These features of urinary MBPLM have made it difficult to produce reagents for its further characterization. Using an immunogen of keyhole limpet hemocyanin conjugated to MBP peptide cys 74-89, polyclonal antiserum to urinary MBPLM was prepared. With the same immunogen and screening with urine, the product from one of over 1600 wells from the original fusion, produced monoclonal antibody (mAb) which could detect urinary MBPLM. By radioimmunoassay two rabbit polyclonal reagents recognized a cryptic epitope in MBP peptide 84-89 while the two mAbs recognized another cryptic epitope in MBP peptide 80-85. Both could be used for quantitation of MBPLM in urine. These and previous results indicate the presence of at least three epitopes, one noncryptic and two cryptic, in the decapeptide of MBP 80-89. Of the two cryptic epitopes, the one near the carboxyl-terminal is dominant to that in the amino-terminal portion. The detection of urinary MBPLM with reagents with two different specificities suggests the presence of two or more small MBP peptides in urine.

Amino Acid Sequence↗
PubMed1994

Monoclonal antibodies to a TCR idiotope modulate the superantigen-induced responses of encephalitogenic rat T cells.

Superantigens, such as staphylococcal enterotoxins, activate T lymphocytes by linking MHC class II molecules on antigen presenting cells to the V beta element of the TCR. Through this effect on T cells, superantigens may influence the immune response and autoimmune disease. In fact, superantigens may activate or anergize cells involved in the production of experimental allergic encephalomyelitis. Lewis rats recognize an encephalitogenic epitope in myelin basic protein (MBP) residues 68-88 through an MHC class II I-A restricted process using TCR V beta 8.2. The F30 murine mAb reacts with an encephalitogenic idiotope (Id) on the TCR of V beta 8.2+ encephalitogenic Lewis rat T cells. In the present study it was demonstrated that the same mAb anti-Id inhibited the proliferation and IL-2 secretion induced by staphylococcal enterotoxins A, B and E in a V beta 8.2+ encephalitogenic Lewis rat T cell line specific for guinea pig MBP peptide 68-88. The mAb anti-Id did not inhibit the response of control T cells similarly derived but inhibited V beta 8.2- and recognizing MBP peptide 87-99. Control anti-Id failed to inhibit the response of either cell line. These findings imply that the specific antigen and superantigen react with TCR in a manner similar enough to be inhibited by the same anti-Id. The mechanism may involve the induction of anergy by the anti-Id, interference/steric hindrance by the reaction of anti-Id with TCR and possibly a little direct reaction of anti-Id with superantigens. Anti-Id directed immunotherapy may have a role in modulating the damage of inflammatory demyelination induced by both specific antigens and superantigens.

Amino Acid Sequence↗
PubMed1994

Citrulline-containing myelin basic protein is recognized by T-cell lines derived from multiple sclerosis patients and healthy individuals.

The cause of MS is uncertain, but an autoimmune disorder of the CNS is likely, and myelin basic protein (MBP) is a candidate antigen. MBP exists in different isoforms, generated by differential splicing of exons, and in charge isomers, generated by posttranslational modifications. Different isoforms and charge isomers presumably subserve different functions, and they vary in abundance in immature myelin found during myelinogenesis and remyelination compared with mature myelin. The 18.5-kd isomer is most abundant in normal human adults and consequently has been used almost exclusively for immunologic studies in MS. In the present study, we examined a different but abundant charge isomer of MBP, termed MBP-C8, to determine whether it could be recognized by MBP-specific cytotoxic and proliferative T-cell lines (TCL) and whether a T-cell response directed exclusively against citrulline-containing residues of MBP-C8 exists in MS patients and healthy controls. We showed that citrulline affects antigen recognition by some TCL that are specific for areas of MBP that contain the citrulline residues. Following stimulation with MBP-C8, MBP-C8-specific TCL could be generated from both MS patients and controls. T-cell responses against antigens that appear during myelinogenesis and during remyelination may be important in inducing and perpetuating an autoimmune response involved in the pathogenesis of MS.

Adult↗
PubMed1993

Specific modulation of T cells and murine experimental allergic encephalomyelitis by monoclonal anti-idiotypic antibodies.

Acetylated peptide 1-9 from human myelin basic protein induces experimental allergic encephalomyelitis in PL/J mice through I-Au and TCR V beta 8.2. Murine mAb anti-Id directed against murine mAb to myelin basic protein peptide acetyl 1-9 was examined for effects on in vitro and in vivo T cell activities. Certain anti-Id, generated in PL/J mice, inhibited Ag-specific proliferation and IL-2 production and precipitated surface receptors having features of the TCR. The idiotypic features of TCR recognition were demonstrated by showing that binding of anti-Id to the TCR could be blocked by anti-TCR alpha beta and anti-TCR V beta 8.1-8.2 but not by murine Ig or anti-TCR V beta 17a. In addition, the anti-Id did not react with TCR V beta 8.2 transgenically inserted into MRL+/+ mice. One anti-Id was also capable of lessening clinical disease activity in the adoptive passive transfer model of experimental allergic encephalomyelitis in PL/J mice. These results indicate that anti-Id may recognize a cross-reactive Id on T cells, presumably on the TCR, responsive to the same I-Au-restricted encephalitogenic myelin basic protein peptide in PL/J mice. The selective development of anti-Id and their effect on T cell-mediated tissue damage provide a method for applying specific anti-Id antibodies to modify experimental and, possibly, spontaneous diseases of autoimmune demyelination.

Amino Acid Sequence↗
PubMed1993

Correlation of myelin basic protein-like material in cerebrospinal fluid of multiple sclerosis patients with their response to glucocorticoid treatment.

Predictors and laboratory correlates of the response of patients with multiple sclerosis to glucocorticoids are not well defined. Our study was undertaken to determine if the levels of myelin basic protein (MBP)-like material in cerebrospinal fluid (CSF) might indicate which patients with multiple sclerosis would show a short-term (5 day) or intermediate-term (40 day) improvement of at least a full-grade Kurtzke disability score after initiating treatment with glucocorticoids. A total of 62 patients received 71 courses of treatment consisting of 5 days of intravenous methylprednisolone (500 mg per day) usually followed by a 4-week tapering dose of oral prednisone. CSF was obtained before initiation of treatment and analyzed for MBP-like material by radioimmunoassay. Results were analyzed by chi 2 tests of association and by logistic regression. Individuals having a CSF MBP-like material level of > or = 0.1 ng/ml overall showed a greater likelihood of continued improvement at day 40 (p = 0.014) or further improvement between days 5 and 40 (p = 0.003). Those in the first 15 days of worsening and with an elevated CSF MBP-like level were more likely to respond by day 5. Relapsing-remitting and relapsing-progressive forms of the disease were more likely to respond at both time points than were patients with primary or secondary chronic progressive patterns. The Kurtzke disability score at entry and the major anatomical site of the central nervous system symptomatically affected were not predictive of outcome at either time.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗