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Forty-four Caucasian American myasthenia gravis (MG) patients from Southeast Texas underwent high resolution HLA DQ analysis. For the majority of patients who were late onset or male, no significant associations with DQ were observed. However, associations with DQ increased in female patients and early onset patients. At the allele level, DQB1 *0503, *0604, *0502 and *0402 collectively contributed to a positive association of the DQ locus with early onset MG (EOMG), while individually failing to show significant association. At DQ level, the novel haplotype DQA1*0401:DQB1*0201 was the primary factor in the association of combined DQ loci with early onset. In addition, *0104:*0503, *0102:*0604, *0102:*0502 and *0303:*0402 collectively contributed to the positive association of the haplotype loci. DR3-DQ2.5cis, a well known risk factor for MG in Western Eurasia, was not found associated with disease in any group. For typical EOMG [early onset, no thymoma, anti-acetylcholine receptor (AChR) antibody (Ab) positive] no association with DQA1 locus was found, however DQB1*0604 demonstrated an 'uncorrected' positive association. A few DQ haplotype (DQA1:DQB1) were positively associated with typical EOMG; a positive individual association for *0401:*0201 was complimented by the contributions of *0102:*0604 and *0303:*0402 haplotypes. A small minority of patients that were atypical and EOMG had a strong genetic association with DQA1*0104:DQB1*0503, the group included an anti-MuSK Ab positive and an anti-AChR negative patient. This report finds common ground with European studies regarding MuSK association; however similarities in association for typical early onset disease resembled HLA risk factors in East Asia and Southern Europe.

Intensive research in this laboratory over the last 19 years has aimed at understanding the molecular bases for immune recognition of botulinum neurotoxin, types A and B and the role of anti-toxin immune responses in defense against the toxin. Using 92 synthetic 19-residue peptides that overlapped by 5 residues and comprised an entire toxin (A or B) we determined the peptides' ability to bind anti-toxin Abs of human, mouse, horse and chicken. We also localized the epitopes recognized by Abs of cervical dystonia patients who developed immunoresistance to correlate toxin during treatment with BoNT/A or BoNT/B. For BoNT/A, patients' blocking Abs bound to 13 regions (5 on L and 8 on H subunit) on the surface and the response to each region was under separate MHC control. The responses were defined by the structure of the antigen and by the MHC of the host. The antigenic regions coincided or overlapped with synaptosomes (SNPS) binding regions. Antibody binding blocked the toxin's ability to bind to neuronal cells. In fact selected synthetic peptides were able to inhibit the toxin's action in vivo. A combination of three synthetic strong antigenic peptides detected blocking Abs in 88% of immunoresistant patients' sera. Administration of selected epitopes, pre-linked at their N(α) group to monomethoxyployethylene glycol, into mice with ongoing blocking anti-toxin Abs, reduced blocking Ab levels in the recipients. This may be suitable for clinical applications. Defined epitopes should also be valuable in synthetic vaccines design.

The capacity of antibodies to various synthetic peptides of α-bungarotoxin for binding peptides of the neurotoxin and recognizing the corresponding regions of the α-bungarotoxin molecule has been investigated. It has been established that individual conformational sections of the α-bungarotoxin molecule are specifically recognized by antibodies to synthetic epitopes of the neurotoxin.

This paper discusses literature reports over the last 12 years and the results of our own experimental investigations of the structures of the immune recognition regions of protein antigens — in particular presynaptic and postsynaptic neurotoxins from spider and snake venoms.

In this multicenter study of 100 patients with cervical dystonia, we examined the immunogenicity of botulinum toxin type B (BTX-B) and correlated the clinical response with the presence of blocking antibodies (Abs) using a novel mouse protection assay. One-third of the patients who were negative for BTX-B Abs at baseline became positive for BTX-B Abs at last visit. Thus, the high antigenicity of BTX-B limits its long-term efficacy.

We have mapped the regions recognized by T and/or B cells (Abs) on the C-terminal domain (Hc) of the heavy chain of botulinum neurotoxin serotype A (BoNT/A) after immunization of two inbred mouse strains with pentavalent toxoid (BoNTs A, B, C, D and E). Using a set of synthetic overlapping peptides, encompassing the entire Hc domain (residues 855-1296), we demonstrated that T cells of Balb/c (H-2d) mice, primed with one injection of toxoid, recognized two major regions within residues 897-915 and 939-957. After multiple inoculations with toxoid, T cells of Balb/c expanded their recognition ability and responded very well to challenge with peptide 1261-1279 and moderately to stimulation with peptide 1149-1167. Unlike Balb/c T cells, those of toxoid-primed SJL (H-2s) mice exhibited a more complex profile and responded to challenge with a large number of overlapping peptides. After one toxoid injection, however, three peptides, 897-915, 939-957/953-971 overlap and 1051-1069, were the most potent T cells stimulators. After three toxoid injections, peptides 897-915 and 1051-1069 remained immunodominant while the third region was shifted upstream to 925-943/939-957 overlap. The immunodominant epitope within peptide 897-915 was recognized exclusively by T cells, since no Abs were detected against this region. The Ab binding profiles of the two mouse strains were quite similar, showing only small quantitative differences. Both, Balb/c and SJL anti-toxoid Abs displayed strong binding mainly to peptide 1177-1195, followed by peptides 869-887/883-901 overlap and 1275-1296. In addition, a significant amount of Balb/c anti-toxoid Abs was bound to peptide 1135-1153. Unlike Balb/c Abs, that interacted weakly with peptides 995-1013 and 1051-1069, the anti-toxoid Abs of SJL mice exhibited strong binding toward both peptides. The results showed that, in a given strain, the regions recognized by anti-toxoid Abs and T cells may coincide or may be uniquely B or T cell determinants.

Botulism due to food poisoning is caused mainly by protein toxins, botulinum neurotoxins (BoNTs), produced by Clostridium botluinum in seven known immunological serotypes. These are the most potent toxins and poisons known. BoNT effects blockade of neuromuscular transmission by preventing neurotransmitter release. Human botulism is most frequently caused by types A, B, and E. Recent studies have shown that immunization with a 43-kDa C-terminal fragment (Hc, residues 860-1296) of BoNT/A affords excellent protection against BoNT/A poisoning. We raised antibodies (Abs) against BoNT/A in horse, and against pentavalent toxoid (BoNTs A, B, C, D, E) in human volunteers and outbred mice. Thirty-one 19-residue peptides that started at residue 855, overlapped consecutively by 5 residues, and encompassed the entire length of the Hc of BoNT/A were synthesized and used for mapping the Ab-binding regions recognized by the anti-BoNT/A antisera. Horse Abs against BoBT/A were bound by peptides 855-873, 939-957, 1079-1097/1093-1111 overlap, 1191-1209/1205-1223 overlap, 1261-1279 and 1275-1296. In addition, peptides 883-901, 911-929, 995-1013, 1023-1041/1037-1055 overlap, 1121-1139, and 1149-1167 gave low, but significant and reproducible, binding. With human antisera, high amounts of Abs were bound by peptides 869-887, 925-943, 981-999, 995-1013, 1051-1069, and 1177-1195. In addition, lower amounts of Abs were bound by peptides 911-929, 939-957, 967-985, and the overlaps 1121-1139/1135-1153 and 1247-1265/1261-1279/1275-1296. With outbred mouse antisera, high amounts of Abs were bound by peptides 869-887, 1051-1069, and 1177-1195, while peptides 939-957, 995-1013, 1093-1111, and 1275-1296 bound lower amounts of Abs. The results indicate that horse antiserum against BoNT/A or human and mouse (outbred) antisera against the toxoid recognized similar regions on BoNT/A, but exhibited some boundary frame shifts and differences in immunodominance of these regions among the antisera. Selected synthetic epitopes will be used as immunogens to stimulate active or passive (by Ab transfer) immunity against toxin poisoning.

We have previously mapped the T and B cell epitopes on the alpha-subunit of acetylcholine receptor (AChR) in human myasthenia gravis (MG) and in experimental autoimmune MG-susceptible (C57BL/6 (B6)) and nonsusceptible mouse strains. In addition to regions recognized by both T and B cells, the AChR alpha-subunit has regions that are recognized solely by T cells. An exclusive T cell epitope within residues alpha 146-162 of Torpedo californica (t), tAChR, plays an important role in experimental autoimmune MG pathogenesis in B6 mice. To study its function, we established, from tAChR-primed B6 mice, two t alpha 146-162-specific T cell lines (P14Th) which comprised Th2-type cells because they secreted IL-4 but not IL-2. P14Th did not recognize the corresponding region on mouse (m) AChR (m alpha 146-162). They caused in vitro differentiation of tAChR-primed B cells into plasma cells that secreted anti-AChR Abs directed, in decreasing order, against the following tAChR alpha regions: t alpha 122-138 > t alpha 134-150 > t alpha 45-60 > t alpha 170-186 > t alpha 56-71. Little or no Ab response could be detected against peptides t alpha 182-198 or t alpha 146-162 itself. The major enhancement was in the Abs against region t alpha 122-150 (spanning the t alpha 122-138/t alpha 134-150 overlap) that is involved in ACh binding. These Abs cross-reacted completely with m alpha 122-150, the corresponding region on mAChR. Therefore, t alpha 146-162-specific T cells, although unable to recognize m alpha 146-162, are nevertheless pathogenic because they help B cells responding to a tAChR region that is conserved in mAChR and involved in ACh binding. These Abs cross-react with the corresponding effector-binding region of mAChR, thereby disrupting the normal physiologic function of the mouse receptor.

The purpose of the present work was to determine the ability of BgTX peptides, corresponding to the various loops and exposed regions of α-bungarotoxin (BgTX) and representing regions that are recognized by B and/or T cells, to stimulate protective immunity in mice against in vivo challenge with BgTX. The BgTX LD50 values in non-immune mice or mice that had been immunized with proteins and peptides unrelated to BgTX were: Balb c , 0.128 μg/g; SJL, 0.156 μg/g. Immunization of Balb c and SJL mice with each of the synthetic peptides in its free form afforded considerable protection against BgTX poisoning. Peptides L1 (residues 3–16), L2 (residues 26–41) and C-tail (residues 66–74) of BgTX were the most protective and mice immunized with these peptides survived LD50 values that were three times higher than control mice. Immunization with an equimolar mixture of the three peptides was even more protective and these mice survived even higher challenge doses of BgTX (4.6-fold higher than LD50 of controls; i.e. protection index, PI = 4.6). An OVA conjugate carrying all three peptides, when used as an immunogen, conferred extremely high protection (PI ≥ 18.1) which was almost double the protection obtained by BgTX immunization (PI = 9.7). Thus, the conjugate of the three peptides should serve as an effective vaccine against BgTX poisoning. Furthermore, these results with BgTX peptides should serve as a prototype for the design and synthesis of peptide vaccines against other members of this large family of toxins which include both long and short neurotoxins as well as cytotoxins.

Previous study has shown that reduced T cell response to peptide alpha 146-162 of Torpedo californica acetylcholine receptor (tAChR) in B6.C-H-2bm12 (bm12) mice, a mutant of C57BL/6 (B6) mice, correlated with its nonsusceptiblity to experimental autoimmune myasthenia gravis. There are three amino acid differences between the I-A beta b of the two strains (positions 67, 70, and 71). We synthesized peptides I-A beta b62-76 (peptide b6), I-A beta bm1262-76 (peptide bm), and three additional peptides, b6(67F), b6(70Q), and b6(71K), and determined their ability to bind peptide alpha 146-162 and the dissociation constants (Kd) of the binding. Peptide alpha 146-162 bound with a significantly higher affinity to peptide b6 than to peptides bm or b6(71K), suggesting that the lower affinity of peptide alpha 146-162 to I-Abm12 is a factor in the reduced response to this peptide by bm12 T cells. This was confirmed by measurement of the Kd values of the binding of peptide alpha 146-162 to the I-A molecules of B6 and bm12. Furthermore, APC of bm12 presented the peptide, or tAChR, poorly to peptide-specific or to tAChR-specific B6 T cells. The major effect is caused by the change of Thr-71 in I-A beta b to lysine in I-A beta bm12. However, APC of B6 also presented peptide alpha 146-162 much less efficiently to peptide-specific T cells of bm12. This demonstrated that these three amino acid changes also influence the T cell receptor recognition of peptide-MHC complex and that both B6 and bm12 T cells recognizing peptide alpha 146-162 or tAChR are under a high H-2 restriction.

THE provision of model compounds containing amino-acids or their analogues attached to sugars is of importance in evaluating the stability of the numerous types of carbohydrate-peptide linkages theoretically possible in mucoproteins. The ability of 2,3-dihydropyran to condense with —OH, —SH, and —NH2 groupings suggested a route to the glycosidically linked model compounds. The tetrahydropyran-2-yl derivatives so formed had the added advantage that the lability of the glycosidic linkage could be investigated without attendant complications such as acyl migration under alkaline conditions or Amadori re-arrangement catalysed by acid which might ensue in the presence of a hydroxyl substituent at C–2 of the pyran ring.

Absorption of ketoconazole is impaired in subjects with an increased gastric pH due to administration of antacids, H2-receptor antagonists, proton pump inhibitors, or the presence of hypochlorhydria. Sucralfate could provide an attractive alternative in patients receiving ketoconazole who require therapy for acid-peptic disorders. Twelve healthy human volunteers were administered a single 400-mg oral dose of ketoconazole in each of three randomized treatment phases. In phase A, ketoconazole was administered orally with 240 ml of water. In phase B, ketoconazole and sucralfate (1.0 g) were administered simultaneously with 240 ml of water. In phase C, ketoconazole was administered with 240 ml of water 2 h after administration of sucralfate (1.0 g) orally with 240 ml of water. A 680-mg oral dose of glutamic acid hydrochloride was administered 10 min prior to and with each dose of ketoconazole, sucralfate, or ketoconazole plus sucralfate. Simultaneous administration of ketoconazole and sucralfate led to a significant reduction in the area under the concentration-time curve and maximal concentration of ketoconazole in serum (78.12 +/- 12.20 versus 59.32 +/- 13.61 micrograms.h/ml and 12.34 +/- 3.07 versus 8.92 +/- 2.57 micrograms/ml, respectively; P < 0.05). When ketoconazole was administered 2 h after sucralfate, the observed ketoconazole area under the concentration-time curve was not significantly decreased compared with that of ketoconazole alone. The time to maximal concentrations in serum and the ketoconazole elimination rate constant were not significantly different in any of the three treatment phases. In patients receiving concurrent administration of ketoconazole and sucralfate, doses should be separated by at least 2 h.

The extracellular surface of the alpha-chain of Torpedo california acetylcholine receptor (AChR) was mapped for regions that are accessible to binding with antibodies against a panel of synthetic overlapping peptides which encompassed the entire extracellular parts of the chain. The binding of the antipeptide antibodies to membrane-bound AChR (mbAChR) and to isolated, soluble AChR was determined. The specificity of each antiserum was narrowed down by determining the extent of its cross-reaction with the two adjacent peptides that overlap the immunizing peptide. With mbAChR, high antibody reactivity was obtained with antisera against peptides alpha 1-16, alpha 89-104, alpha 158-174, alpha 262-276, and alpha 388-408. Lower, but significant, levels of reactivity were obtained with antibodies against peptides alpha 67-82, alpha 78-93, alpha 100-115, and alpha 111-126. On the other hand, free AChR bound high levels of antibodies against peptides alpha 34-49, alpha 78-93, alpha 134-150, alpha 170-186, and alpha 194-210. It also bound moderate levels of antibodies against peptides alpha 262-276 and alpha 388-408. Low, yet significant, levels of binding were exhibited by antibodies against peptides alpha 45-60, alpha 111-126, and alpha 122-138. These binding studies, which enabled a comparison of the accessible regions in mbAChR and free AChR, revealed that the receptor undergoes considerable changes in conformation upon removal from the cell membrane. The exposed regions found here are discussed in relation to the functional sites of AChR (i.e., the acetylcholine binding site, the regions that are recognized by anti-AChR antibodies, T-cells and autoimmune responses and the regions that bind short and long neurotoxins).

Forty-four Caucasian American myasthenia gravis (MG) patients from Southeast Texas underwent high resolution HLA DQ analysis. For the majority of patients who were late onset or male, no significant associations with DQ were observed. However, associations with DQ increased in female patients and early onset patients. At the allele level, DQB1 *0503, *0604, *0502 and *0402 collectively contributed to a positive association of the DQ locus with early onset MG (EOMG), while individually failing to show significant association. At DQ level, the novel haplotype DQA1*0401:DQB1*0201 was the primary factor in the association of combined DQ loci with early onset. In addition, *0104:*0503, *0102:*0604, *0102:*0502 and *0303:*0402 collectively contributed to the positive association of the haplotype loci. DR3-DQ2.5cis, a well known risk factor for MG in Western Eurasia, was not found associated with disease in any group. For typical EOMG [early onset, no thymoma, anti-acetylcholine receptor (AChR) antibody (Ab) positive] no association with DQA1 locus was found, however DQB1*0604 demonstrated an 'uncorrected' positive association. A few DQ haplotype (DQA1:DQB1) were positively associated with typical EOMG; a positive individual association for *0401:*0201 was complimented by the contributions of *0102:*0604 and *0303:*0402 haplotypes. A small minority of patients that were atypical and EOMG had a strong genetic association with DQA1*0104:DQB1*0503, the group included an anti-MuSK Ab positive and an anti-AChR negative patient. This report finds common ground with European studies regarding MuSK association; however similarities in association for typical early onset disease resembled HLA risk factors in East Asia and Southern Europe.

Monoclonal antibodies of predetermined specificity were prepared by immunization with a free (i.e., without coupling to any protein carrier) synthetic peptide representing region 145-151 of sperm whale myoglobin (SpMb) and their cross-reactions with eight Mb variants were determined. Five Mbs--bottle-nose dolphin myoglobin (BdMb), pacific common dolphin myoglobin (PdMb), horse myoglobin (HsMb), dog myoglobin (DgMb), and badger myoglobin (BgMb)--have an identical sequence in that region. Nevertheless, these Mbs exhibited very different cross-reactivities. BdMb and PdMb exhibited cross-activities which were comparable to that of the reference antigen, SpMb; while the reactivity of HsMb was remarkedly decreased, DgMb and BgMb showed almost no cross-reactions with these mAbs. Since the region 145-151 has an identical sequence in all the five Mbs, it is concluded that the differences in their antigenic reactivities with anti-region 145-151 mAbs are due to the effects of amino acid substitutions outside the region 145-151. Another pair of myoglobins, echidna myoglobin (EdMb) and chicken myoglobin (ChMb), have the same sequence in that region, but reacted very differently with anti-region 145-151 mAbs. The reactivity and affinity of EdMb were substantially decreased while those of ChMb were almost completely absent, relative to SpMb. It is concluded, contrary to popular assumptions, that when an amino acid substitution influences the binding of a protein variant to a mAb, it is not necessary for that substitution to be an actual contact residue (i.e., a residue within the antigenic site where the mAb binds). Such effects, which are often very drastic, could be due to indirect influences of the substitution on the chemical and binding properties of the site residues. Furthermore, residues which had been postulated, on the basis of these assumptions, to constitute discontinuous antigenic sites in SpMb, were found [from the present studies and those recently reported with mAbs against the other four antigenic site of Mb (regions 15-22, 56-62, 94-100, and 113-120 of SpMb)] to merely be exerting indirect effects on the known five antigenic sites of Mb. The effects of substitutions, which can happen even in the absence of conformational changes, are determined by many factors, such as the chemical nature of the substitution, its environment, its distance from the site, and the nature of the site residue(s) being affected.

This work was carried out in order to study the effects of substitutions outside antigenic site 2 of sperm whale myoglobin (SpMb) on the reactivity of protein variants with antisite 2 monoclonal antibodies (mAbs). A synthetic peptide corresponding to region 56-62 (site 2) of SpMb was used as an immunogen in mice in its free form (i.e., without coupling to any carrier) to prepare a panel of mAbs whose predetermined specificity is directed, by design, against this region. The binding of three of these mAbs to eight Mbs from different species was studied. Myoglobins of Pacific common dolphin, finback whale, and horse, which have no substitutions within region 56-62 relative to SpMb, showed remarkable differences in their cross-reactivities and relative affinities with each of the mAbs. Myoglobins of badger, chicken, and dog, although they have an identical substitution within the site (Ala-57 to Gly), exhibited cross-reactivities with a given mAb that were affected differently. Echidna Mb, which has one replacement (Glu-59 to Ala) within region 56-62, displayed greatly reduced cross-reactivities and relative binding affinities. The results, especially those from Mbs that have no substitutions within the boundaries of site 2, clearly indicate that substitutions outside site 2 of Mb can exert drastic effects on the binding of the Mb variants with mAbs whose specificity was predesigned to be against the site. These indirect effects and their impact on site reactivity will completely explain previous findings on cross-reactivities of Mb variants with mAbs of unknown specificity and will rule out the postulations of discontinuous sites in Mb, which were based on the assumption that every substitution affecting reactivity is directly involved in binding to antibody.

Monoclonal antibodies (mAbs) of predetermined specificity were prepared by immunizing with a free (i.e., not conjugated to any carrier) synthetic peptide representing region 15-22 (site 1) of sperm whale myoglobin (SpMb). The cross-reactions of Mb variants with three mAbs were studied in order to determine whether such interactions are influenced by substitutions outside the site. Finback whale Mb, which has no substitutions within region 15-22, showed lower cross-reactivity and relative binding affinity than the reference antigen, SpMb. Bottle-nose Atlantic dolphin myoglobin (BdMb) and badger myoglobin (BgMb), although they have identical substitutions within region 15-22 (Ala-15 to Gly and Val-21 to Leu), showed very different binding properties. The cross-reaction of BdMb was quite comparable to that of SpMb, while that of BgMb was much lower. Since the two proteins have identical structures in regions 15-22, the differences in their cross-reactivities are readily attributed to the effects of substitutions outside this region. Another pair of myoglobins, horse myoglobins (HsMb) and chicken myoglobin (ChMb), also have two identical substitutions (Ala-15 to Gly and Val-21 to Ile) within region 15-22, but possessed different cross-reactivity. The results indicate that the reaction of mAbs, whose specificity is precisely known and predetermined by the immunizing free peptide, can be markedly affected by substitutions outside the indicated binding region on the protein.

Two regions of human thyrotropin (thyroid-stimulating hormone, TSH) receptor (TSHR) (residues 12-44 and 308-364) were selected on the basis that they exhibit no sequence resemblance to luteinizing hormone/chorionic gonadotropin receptor. Five synthetic overlapping peptides (12-30, 24-44, 308-328, 324-344, and 339-364) were studied for their ability to bind 125I-labeled human TSH (hTSH), its isolated alpha and beta subunits, bovine TSH, ovine TSH, human luteinizing hormone, and human follicle-stimulating hormone. The human TSHR peptides 12-30 and 324-344 exhibited remarkable binding activity to human, bovine, and ovine TSH and to the beta chain of hTSH. Lower binding activity resided in the adjacent overlapping peptides, probably due to the contribution of the shared overlap to the binding. The specificity of TSH binding to these peptides was confirmed by their inability to bind human luteinizing hormone, human follicle-stimulating hormone, and the alpha chain of hTSH. Thyrotropins did not bind to bovine serum albumin or to peptide controls unrelated to the TSHR system. Furthermore, the binding of hTSH to TSHR peptides 12-30 and 324-344 was almost completely (approximately 90%) inhibited by rabbit antibodies against hTSH but not by antisera against unrelated proteins. It is concluded that the binding of TSH to its receptor involves extensive contacts and that the TSHR peptides 12-30 and 324-344 contain specific binding regions for TSH that might be either independent sites or two faces (subsites) within a large binding site.

The continuous regions for short-neurotoxin binding on the alpha-chains of Torpedo californica (electric ray) and human acetylcholine receptors (AChR) were localized by reaction of 125I-labelled cobrotoxin (Cot) and erabutoxin b (Eb) with synthetic overlapping peptides spanning the entire extracellular part of the respective alpha-chains. On Torpedo AChR, five Cot-binding regions were found to reside within peptides alpha 1-16, alpha 23-38/alpha 34-49 overlap, alpha 100-115, alpha 122-138 and alpha 194-210. The Eb-binding regions were localized within peptides alpha 23-38/alpha 34-49/alpha 45-60 overlap, alpha 100-115 and alpha 122-138. The main binding activity for both toxins resided within region alpha 122-138. In previous studies we had shown that the binding of long alpha-neurotoxins [alpha-bungarotoxin (Bgt) and cobratoxin (Cbt)] involved the same regions on Torpedo AChR as well as an additional region within residues alpha 182-198. Thus region alpha 182-198, which is the strongest binding region for long neurotoxins on Torpedo AChR, was not a binding region for short neurotoxins. On human AChR, peptide alpha 122-138 possessed the highest activity with both toxins, and lower activity was found in the overlap alpha 23-38/alpha 34-49/alpha 45-60 and in peptide alpha 194-210. In addition, peptides alpha 100-115 and alpha 56-71 showed strong and medium binding activities to Eb, but low activity to Cot, whereas peptide alpha 1-16 exhibited low binding to Cot and no binding to Eb. Comparison with previous studies indicated that, for human AChR, the binding regions of short and long neurotoxins were essentially the same. The finding that the region within residues alpha 122-138 of both human and Torpedo AChR possessed the highest binding activity with short neurotoxins indicated that this region constitutes a universal binding site for long and short neurotoxins on AChR from various species.

Radiolabeled thyroid hormones were allowed to bind to erythrocyte cytosol and the complex was fractionated by Sephadex G-100 or by high-performance liquid chromatography (HPLC). On Sephadex G-100, four radioactive peaks (P1-P4) were obtained, whereas HPLC gave only three radioactive peaks (P1-P3). Chromatographic studies with human adult Hb and non-Hb cytosol protein fractions, which had been reacted with radiolabeled thyroid hormones, and immune precipitation with specific antisera for the hormones, confirmed that the first peak of Sephadex G-100 radioactivity was a mixture of Hb and non-Hb proteins, while the second peak was Hb. The third peak was free 125I and the fourth peak was unbound 125I-T3 or 125I-T4. The third peak of HPLC was confirmed to be a mixture of free 125I and unbound radiolabeled thyroid hormones. Scatchard analysis of the interaction between T4 and apo-Hb, and the alpha- and beta-chains of human Hb suggested the presence of the specific binding site(s) for the hormone. Interaction between T4 and synthesized peptides, which constitute the heme pocket of the beta-chain of Hb (beta 61-75, beta 71-85, beta 81-95), indicated that the T4 binding site of Hb resides within the heme-binding cavity. It is concluded that human erythrocyte cytosol does not contain "receptor" for thyroid hormones and cannot be a model for studying functions of cytosol "receptor" for the hormones; rather, it contains binding protein with large binding capacity, including Hb and non-Hb proteins, which possibly constitute a large reservoir for the hormone in blood.

Autoimmune T cell lines were prepared from peripheral blood lymphocytes of five myasthenia gravis patients by passage in vitro with an equimolar mixture of 18 overlapping synthetic peptides corresponding to the entire extracellular region (residues alpha 1-210) of the alpha subunit of human acetylcholine receptor (AChR). The proliferative responses of the human AChR-specific T cell lines to each of the individual peptides were determined. It was found that the profiles of the peptides recognized by the T cells were different among the five T cell lines, consistent with genetic control operating at the recognition site level. However, other regulatory influences may play important roles in the triggering of the autoimmune responses. These results suggest that the pathogenesis of this autoimmune disease is variable at the cellular-molecular level.

The T cell recognition of globular protein antigens requires the cell surface presentation of the protein by Ia-expressing antigen-presenting cells (APC). The mechanisms by which APC function remain to be elucidated. To gain a better understanding of association of antigen with APC surfaces, a large panel of peptides of diverse physicochemical properties was assayed for the ability to compete with presented antigen for binding sites on the APC surface. Competition was measured by the ability of a peptide to block the I-Ek-restricted T cell response to pigeon cytochrome c (Pc) as presented by APC. The panel assayed included overlapping peptides representing the entire length of sperm whale myoglobin and the alpha and beta chains of human adult hemoglobin as well as synthetic conformational peptides of lactate dehydrogenase C4 exhibiting stable secondary, alpha-helical structures. The results presented here show that several peptides of this group compete with the presented form of Pc for binding sites on the APC. However, there is no single biochemical property or amino acid sequence algorithm which predicts the blocking ability. The peptides which compete with presented Pc are not predicted to assume the amphipathic alpha-helical conformation hypothesized by De Lisi and Berzofsky (Proc. Natl. Acad. Sci. USA 1986. 82: 7048) for T cell antigenic peptides. However, peptides designed and synthesized to adopt a stable alpha-helical secondary structure show more potent blocking activity than the corresponding linear peptides, suggesting that the secondary structure may indeed be a contributing factor in the ability of presented antigenic peptides to be bound by the APC. The results with the myoglobin and hemoglobin peptides show no connection between any particular secondary structure of the peptide in the native proteins and the ability of the peptides to block presentation. Further, there is no correlation between the major histocompatibility complex restriction of the competing peptides and their ability to block the I-Ek-restricted Pc-specific T cell response. This suggests that antigen presented by the APC may be bound to APC structures other than Ia prior to association with Ia. Such additional binding sites for presented antigen may be necessary to facilitate association with Ia.

Using the method of solid-phase peptide synthesis, two peptides have been synthesized, one of which corresponds to the central ring structure of α-bungarotoxin (α-BTX), while the second has in position 28 a Gly residue in place of the Trp in the first peptide, and their interrelationship with antitoxin antibodies has been investigated. It has been shown that the amino acid residue Trp-28 of α-BTX, which is the contact residue in binding with the acetylcholine receptor, also participates directly in binding with the active centers of antibodies to α-BTX.

Development of effective resuscitation agents for blood-loss replacement in trauma or surgery is extremely important. We synthesized 15 peptides (test peptides) that were designed on the basis that the heme group in myoglobin (Mb) and hemoglobin (Hb) is sandwiched between helices E and F. The abilities of the test peptides and 6 control peptides to form stable complexes with heme were investigated. None of the controls bound heme. However each of the test peptides was able to form 1:1 coordinate complexes with heme, which were stable to manipulation and behaved as a single molecular species. The reduced peptide-heme complexes bound oxygen and gave visible spectra that were typical of oxygenated heme-proteins The heme-peptides gave hyperbolic oxygen- saturation curves, but showed slightly different P5O values. They were administered into mice, either as emulsions in adjuvant or intravenously in PBS. Injection with adjuvant stimulated antipeptide antibody responses, which bound to the correlate protein (Mb or Hb). But the peptides were non-immunogenic when administered intravenously in PBS.

Myasthenia gravis (MG) is a disabling autoimmune disease caused by autoantibodies (auto-Abs) against the self-acetylcholine receptor (AChR). Although a great deal of information is known about the molecular and cellular parameters of the disease, its initial trigger, however, is not known. To study the possibility of the involvement of microbial antigens that mimic AChR in triggering MG, we have searched the microbial proteins in the data bank for regions that are similar in structure to the regions of human (h) AChR alpha chain recognized by auto-Abs in MG patients. Hundreds of candidate structures on a large number of bacterial and viral proteins were identified. To test the feasibility of the idea, we synthesized four microbial regions similar to each of the major autodeterminants of hAChR (alpha12-27, alpha111-126, alpha122-138, alpha182-198) and investigated their ability to bind auto-Abs in MG and normal sera controls. It was found that MG sera potentially recognized a significant number of these microbial regions. The results indicate that in some MG cases, immune responses to microbial antigens may cross-react with self-antigen (in this case hAChR) and could constitute initial triggers of the disease. Although anti-AChR Abs directly contribute to the degradation of AChR at the neuromuscular junctions, autoreactive T cells provide help to B cells that synthesize anti-AChR auto-Abs. To cause MG, T cells must recognize the pathogenic epitopes in the context of MHC class II molecules related to MG. The ability to regulate AChR presentation (hence AChR-reactive T-cell activation) could form the basis of an effective strategy for the control of autoimmunity in MG by selectively inhibiting the function of the Ir gene loci linked to disease susceptibility. An animal model of MG (experimental autoimmune MG, EAMG) can be induced in C57BL/6 (B6, H-2b) mice by immunization with Torpedo californica (t) AChR. A mutant mouse of B6, B6.C-H-2bm12 (bm12), which has three amino acid changes (at residues 67, 70, and 71) in the I-A beta(b) subunit, is resistant to EAMG development. Recently, we showed that region 62-76 of I-A beta(b), which contains the above residues, is involved in the binding to a pathogenic T-cell epitope within peptide t alpha146-162. We have prepared several monoclonal antibodies (mAbs) against peptide I-A beta(b)62-76, which are highly cross-reactive with I-A(b) molecules. These mAbs inhibited in vitro the proliferation of disease-related T cells of B6 specific to tAChR peptide t alpha146-162. Passive transfer of these mAbs suppressed the occurrence of clinical EAMG, which was accompanied by lower T-cell and Ab responses to tAChR. The results indicated that blocking disease-related MHC by targeting a disease-associated region on MHC molecules could be an effective, straightforward, and feasible strategy for immunointervention in MG.

Botulism, which was first reported over a century ago, is caused by botulinum neurotoxins produced by Clostridium botulinum in seven immunological serotypes (A through G). The primary structures of a number of these BoNTs have been determined and are reviewed here, together with their gene structure and synthesis. The biological actions of BoNTs, which result in their ability to block neurotransmitter release have been the subject of intensive study, and in this review we discuss the binding of BoNTs to the cell surface as well as the mechanism of their intercellular action. The ability of BoNTs to block neurotransmitter release has been exploited in therapeutic applications to reduce muscle hyperactivity for the treatment of a variety of clinical conditions associated with involuntary muscle spasm and contractions. The advantages, limitations, and risks of these applications are discussed. Certain compounds provide some limited protection against BoNT. However, more effective protection has been obtained immunologically either by passive immunity (i.e., by administration of anti-BoNT Abs) or by immunization with inactivated toxin. More recently, excellent protection has been obtained by immunization with the receptor-binding region comprising the C-terminal (residues 860 to 1296) fragment (Hc) of the heavy chain of BoNT/A. Here we review the mapping of the epitopes on the Hc region of BoNT/A that are recognized by anti-BoNT/A Abs raised in horse, human, and mouse. The epitopes on the Hc that are recognized by anti-Hc Abs and by Hc-primed T lymphocytes were mapped in two mouse strains [BALB/c (H-2d) and SJL (H-2s)]. The peptides, which contain Ab or T cell epitopes (or both) on the Hc, were used as immunogens in BALB/c and SJL mice and we identified those peptides whose Ab and/or T-cell response cross-react with Hc. Identification of these peptides is an important first step in the intricate requirements for the design of a synthetic vaccine.

By using synthetic overlapping peptides encompassing the entire alpha-chain of adult human hemoglobin (HbA), we have mapped on the alpha-chain the regions responsible for its binding to the beta-chain in solution. These binding surfaces were, in general, in good agreement with those expected from the crystal structure (peptides alpha81-95, alpha101-115, alpha111-125, and alpha131-141). However, we observed some significant differences in the levels of binding found here in solution and those expected from the crystal structure. Peptide alpha31-45, which in the crystal had the highest number of contact residues of all the alpha-chain peptides, did not bind the beta-chain in solution. Similarly, peptide alpha91-105, with seven contact residues in the crystal, showed low binding with the beta-chain in solution. On the other hand, peptides alpha41-55 and alpha121-135 possessed much higher binding activity in solution than would be expected from their contribution to subunit association in the crystal. In fact, peptide alpha121-135 had the highest binding activity of the alpha-chain peptides. These studies and our previous findings, which localized on the beta-chain the regions that bind to the alpha-chain in solution, have shown that the regions of subunit association in solution are close to, but not identical with, those in the crystal. The approach should be quite useful for mapping subunit association in oligomeric proteins and could even be applied to proteins that are isolated only in traces or whose three-dimensional structure is not yet known.

A brain tumour-associated marker, urokinase (UK), was investigated using rabbit anti-UK polyclonal and murine anti-UK monoclonal antibodies, which were prepared by immunization with low molecular weight UK (LMW-UK) and high molecular weight urokinase (HMW-UK) synthetic peptide respectively. The polyclonal antibody cross-reacted with both LMW-UK and HMW-UK, whereas the murine MAbs were specific for HMW-UK. These immunological probes were used to study urokinase in glioma extracts, tissues, sera and cell lines that had been prepared from primary cultures of freshly dissected gliomas. Radioimmunoassays showed that glioma extracts had much higher level (5- to 44-fold) of UK than normal human brain extracts. This result was confirmed by immunoblotting of electrophoresis gels of glioma and human brain extracts. Immunohistochemical study using anti-UK MAb demonstrated much higher levels of UK in glioma tissue than normal brain tissue. Immunohistochemical study using anti-UK MAbs localized UK on the cell surface of glioma cells. Anti-UK MAbs inhibited the proliferation of AA cell lines and GB cell lines (50% to > 90%) and exerted minor effects (< or = 20%) on normal human liver, intestine and lymphocyte cell lines. Taken together, these results suggest that anti-UK MAbs may have therapeutic potential for human gliomas and cancer metastasis. Images Figure 2 Figure 3

The identification of human brain tumor-associated markers could facilitate the development of new diagnostic and therapeutic strategies for these malignancies. The type III intermediate filament proteins (IFPs): vimentin, desmin and glial fibrillary acidic protein (GFAP) were studied in human glioma tissue extracts, in sera from glioma patients and in low passage glioma cell lines prepared from primary cultures of freshly dissected tumors. Radioimmunoassay (RIA) studies, using anti-GFAP, anti-desmin and anti-vimentin mAbs, showed high levels of these proteins in glioma extracts. Binding studies with authentic IFPs indicated the absence of circulating antibodies against these proteins in the sera of glioma patients. On the other hand, these sera showed high levels of vimentin. Binding studies with these antibodies using RIAs and western immunoblotting, showed that while anti-GFAF mAbs were specific to GFAP, anti-desmin mAb cross-reacted completely with GFAP, anti-vimentin mAb cross-reacted substantially with desmin and GFAP. Immunofluorescence staining of frozen sections revealed high levels of neurofilaments in gliomas and strikingly low levels in normal brain tissue. Double immunofluorescence staining showed co-occurrence of all three IFPs in the same filaments. This suggests either co-expression or cross-reactivity of these proteins due to their high degree of homology. Thus, caution should be exercised in the use and interpretation of immunohistochemical data using antibodies to IFs.

Humoral responses to a protein require T-B cell communication for B cell activation by T cells. Previous studies from this laboratory have mapped the T and B cell recognition sites (epitopes) on sperm-whale myoglobin (Mb) and several other proteins. It was found that, five of six regions on Mb recognized by T cells are also recognized by B cells (i.e. antibodies). There is, however, one region (E6) residing within Mb residues 61-77, that is recognized only by T cells and to which no antibody (Ab) responses are detectable. To investigate the function of this exclusive T cell epitope, we established, from E6-primed BALB/c mice, an E6-specific T cell line (T(e6)) which comprised Th2-type cells. These T cells provided help in vitro to B cells from Mb-primed BALB/c mice and activated them to produce anti-Mb Abs of the IgM (58.2%) and IgG (41.8%) isotypes. The helper activity of T(e6) cells was dependent on the concentration of the challenging Ag (intact Mb or peptide E6) in culture. Action of soluble factors released from E6-activated T(e6) cells on B(mb) cells led to low production of anti-Mb Abs, suggesting that activation of the B cells was more dependent on their contact with T cells. Mapping of the epitope recognition of the anti-Mb Abs produced in vitro by B(mb) cells on activation by T(e6) revealed that this activation was not general to all antigenic regions recognized by anti-Mb Abs in BALB/c mice. E6-specific T cells caused in vitro activation and differentiation of B(mb) cells into plasma cells that secreted anti-Mb Abs directed, in decreasing order, against the following Mb regions: E4 (107-120)E3 (87 - 100)E1 (10 - 22). Little or no Ab responses could be detected against peptides E2 (50 - 62), E5 (141 - 153) and E6 (61 - 77). With B cells of peptide-primed BALB/c mice, T(e6) cells activated strongly E4-, E3- or E1, and only very slightly E2- or E6-, primed B cells to secrete Abs against the correlate peptide, but failed completely to activate E5-primed B cells. The results show that a protein T cell epitope, to which no Abs are detectable, plays an active role in B cell responses against other epitopes within the same protein.

Botulism due to food toxin is caused mainly by seven known serotypes of protein neurotoxins, botulinum neurotoxins (BoNt) produced by clostridium botulinum. BoNts are the most potent toxins and poisons known. The purpose of this work is to design a synthetic peptides vaccine for protection against BoNt. Regions of BoNt/A will be selected for synthesis, based on a number of sequence and conformational parameters and their immunological activities towards anti-BoNt/A antibodies and T cells determined. The immunodominant epitopes will be used as immunogens and those peptides which stimulate BoNt/A-cross reactive antibody and/or T cell responses will then be investigated for their capacity to provide active and passive immunity against BoNt/A challenge. The epitopes that are most protective when employed individually as immunogens will be used, in a mixture and in a multiepitope- carrier conjugate, as a vaccine for both active and passive protection of mice. The synthetic vaccine against BoNt/A will be used as a prototype to prepare synthetic vaccines containing the regions of the other serotypes that are counterparts to the regions found to be most protective on BoNt/A.

Myasthenia gravis (MG) and experimental autoimmune MG (EAMG) are induced by antibodies (Abs) against self acetylcholine receptor (AChR). We have mapped the T and B cell epitopes on AChR alpha subunit in human MG and in EAMG-susceptible (C57BL/6, B6) and nonsusceptible mouse strains. A T-cell epitope within residues alpha 146-162 (P14) of Torpedo californica (t)AChR plays an important role in EAMG pathogenesis of the auto Ab-induced disease. P14-specific T cell (P14Th) lines from tAChR-primed B6 mice activated, in vivo and in vitro, tAChR-primed B cells that secreted anti-AChR Abs directed against four other regions on the tAChR alpha-chain, but not against P14 itself. P14Th cells are pathogenic because they help B cells that make Abs against a conserved tAChR region (t alpha 122-150) involved in ACh binding. These Abs cross-react with region alpha 122-150 of mouse (m)AChR, thereby disrupting its normal physiological function. Thus, a T cell epitope not recognized by Abs plays an active role in B cell responses against other epitopes on the protein. We have found that in B6, the MHC region 62-76 of I-A beta(b) is involved in the presentation of P14 to T cells. Anti-peptide Abs, prepared in BALB/c, were found to inhibit in vitro the proliferation of P14-specific T-cells. Furthermore, this MHC peptide elicited Abs in B6 mice and we are investigating whether immunization of B6 with this peptide, before priming with tAChR, would suppress in vivo the T-cell response to the epitope in P14. Thus, these preliminary results would suggest that immunization with the MHC peptide might be employed for control of the autoimmune disease.

We have previously mapped the T and B cell epitopes on the alpha-subunit of acetylcholine receptor (AChR) in human myasthenia gravis (MG) and in experimental autoimmune MG-susceptible (C57BL/6 (B6)) and nonsusceptible mouse strains. In addition to regions recognized by both T and B cells, the AChR alpha-subunit has regions that are recognized solely by T cells. An exclusive T cell epitope within residues alpha 146-162 of Torpedo californica (t), tAChR, plays an important role in experimental autoimmune MG pathogenesis in B6 mice. To study its function, we established, from tAChR-primed B6 mice, two t alpha 146-162-specific T cell lines (P14Th) which comprised Th2-type cells because they secreted IL-4 but not IL-2. P14Th did not recognize the corresponding region on mouse (m) AChR (m alpha 146-162). They caused in vitro differentiation of tAChR-primed B cells into plasma cells that secreted anti-AChR Abs directed, in decreasing order, against the following tAChR alpha regions: t alpha 122-138t alpha 134-150t alpha 45-60t alpha 170-186t alpha 56-71. Little or no Ab response could be detected against peptides t alpha 182-198 or t alpha 146-162 itself. The major enhancement was in the Abs against region t alpha 122-150 (spanning the t alpha 122-138/t alpha 134-150 overlap) that is involved in ACh binding. These Abs cross-reacted completely with m alpha 122-150, the corresponding region on mAChR. Therefore, t alpha 146-162-specific T cells, although unable to recognize m alpha 146-162, are nevertheless pathogenic because they help B cells responding to a tAChR region that is conserved in mAChR and involved in ACh binding. These Abs cross-react with the corresponding effector-binding region of mAChR, thereby disrupting the normal physiologic function of the mouse receptor.

Previously, we reported 12 synthetic T- and B-cell recognition regions representing surface areas of the hemagglutinin (HA) of X31 influenza virus. In the present study, four of these peptides were examined in Balb/c mice for their ability to produce protective immunity against lethal infection with a dose equivalent to 10 LD50 of influenza virus. These peptides corresponded to the following sequences: 23-36 (HA1-1); 138-152 (HA1-3); 183-199 (HA1-6) and 1-11 (HA2-10). Each of the selected peptides, in their free form, evoked anti-peptide antibodies that cross-react with intact X31 virus. Two of the peptides, HA1-1 and HA1-3, also elicited virus-specific delayed type hypersensitivity (DTH) responses. These two peptides, when injected into mice, not only failed to protect the immunized mice against challenge with influenza virus, but in fact caused greater susceptibility to viral infection as compared to control animals that had been injected with saline. In contrast, peptides HA1-6 and HA2-10, which were unable to induce adequate virus-specific DTH responses, conferred 42-46% and 54-73% protection, respectively, compared to the control group that received only saline (P < 0.03 to P < 0.01).

Previous study has shown that reduced T cell response to peptide alpha 146-162 of Torpedo californica acetylcholine receptor (tAChR) in B6.C-H-2bm12 (bm12) mice, a mutant of C57BL/6 (B6) mice, correlated with its nonsusceptiblity to experimental autoimmune myasthenia gravis. There are three amino acid differences between the I-A beta b of the two strains (positions 67, 70, and 71). We synthesized peptides I-A beta b62-76 (peptide b6), I-A beta bm1262-76 (peptide bm), and three additional peptides, b6(67F), b6(70Q), and b6(71K), and determined their ability to bind peptide alpha 146-162 and the dissociation constants (Kd) of the binding. Peptide alpha 146-162 bound with a significantly higher affinity to peptide b6 than to peptides bm or b6(71K), suggesting that the lower affinity of peptide alpha 146-162 to I-Abm12 is a factor in the reduced response to this peptide by bm12 T cells. This was confirmed by measurement of the Kd values of the binding of peptide alpha 146-162 to the I-A molecules of B6 and bm12. Furthermore, APC of bm12 presented the peptide, or tAChR, poorly to peptide-specific or to tAChR-specific B6 T cells. The major effect is caused by the change of Thr-71 in I-A beta b to lysine in I-A beta bm12. However, APC of B6 also presented peptide alpha 146-162 much less efficiently to peptide-specific T cells of bm12. This demonstrated that these three amino acid changes also influence the T cell receptor recognition of peptide-MHC complex and that both B6 and bm12 T cells recognizing peptide alpha 146-162 or tAChR are under a high H-2 restriction.

C57BL/6 (B6) mice develop a neuromuscular disease, experimental autoimmune myasthenia gravis (EAMG), after two or more immunizations with Torpedo californica acetylcholine receptor (AChR). To determine whether EAMG is related to recognition of particular region(s) on the main extracellular domain of the alpha chain (residues alpha 1-210) in prolonged immunization, we have examined the differences in the antibody and T cell recognition profiles of B6 and SJL (a strain that does not develop EAMG) mice after different periods and a number of immunizations with Torpedo AChR. In a given strain, antibodies and T cells recognized immunodominant regions, which may coincide or may be uniquely B cell or T cell determinants. Both B6 and SJL exhibited similar antibody recognition profiles after the second and through the fourth immunizations with AChR. Major differences between the two strains were found in their T cell recognition of regions in the second part (residues 100-210) of the main extracellular domain of the alpha chain. T cells of SJL recognized consistently only one region (111-126) within this part of the alpha chain, whereas in B6, T cell recognition of three peptides (111-126, 146-162 and 182-198) and next neighbor regions to them persisted throughout the period. Of these three peptides, 146-162 was an immunodominant peptide unique to B6, as the other two peptides (111-126 and 182-198) were also recognized by either T cells or antibodies in SJL. To study the role of the T cells recognizing region 146-162 in EAMG, a T cell line was generated against this region and the cells transferred into B6 mice followed by one Torpedo AChR injection. Enhancement of antibody production toward alpha chain peptides was observed as an influence of T cell transfer compared to profiles at 1 week. In addition, one out of three mice examined showed signs of EAMG. These results suggest the importance of T cells recognizing residues 146-162 in EAMG. It is concluded that the presence of persistent T cell responses to the second half (residues (100-210) of the main extracellular domain of the alpha chain is associated with the development of EAMG in B6 mice, while absence of these responses in SJL mice may enable them to escape the disease. The preservation of the immunodominance of peptide 146-162 in the T cell recognition of B6 is probably most important for the pathogenesis of EAMG in this strain.

An autoimmune response to muscle nicotinic acetylcholine receptor (AChR) culminates in myasthenia gravis (MG) (1,2). MG has been associated with certain HLA antigens (3), and linked to a polymorphism in the HLA-DQs subunit (4). Immunization of C57BL6(B6) mice with Torpedo californica AChR (T-AChR) produces an autoimmune disease mimicking MG called experimental autoimmune myasthenia gravis (EAMG). EAMG susceptibility has been mapped to the I-A subregion of the mouse major histocompatibility complex (MHC) (5,6). Both the I-Aα and the I-As genes contribute to EAMG pathogenesis (5–8). Further, expression of the I-E molecule on the cell surface of C57BL10.IEαk transgenic mice could partially prevent the development of EAMG (9). Thus, the development of EAMG is primarily influenced by the Class II genes. Class II restricted AChR epitope reactive T helper (Th) cells are activated in MG patients and appear to contribute to the postsynaptic pathology (10–11). Th cells are also involved in EAMG pathogenesis (5,6, 12–17), and EAMG can either be prevented, or clinical remission of established disease induced, by in vivo administration of antibodies (Abs) to CD4 molecule (14). The in vitro lymphocyte proliferation to AChR generally correlates with EAMG susceptibility in congenic strains of mice, and is controlled by a Mendelian dominant gene at the I-A locus (12,13). Further, the lymphocyte proliferation is dependent on CD4+ Th cells and I-A molecule (18,19).

To study the organization of the polypeptide chain of the main extracellular domain of the nicotinic acetylcholine receptor (AChR) alpha-subunit, we examined the ability of the native membrane-bound AChR of Torpedo californica (T-AChR) to bind a panel of antibodies against overlapping synthetic peptides which collectively encompassed this entire domain. Antibodies against the alpha-chain peptides alpha 1-16, alpha 89-104 and alpha 158-174 were able to bind to membrane-bound T-AChR. Other anti-peptide antibodies showed little or no binding to T-AChR in the membrane. It is concluded that regions alpha 1-16, alpha 89-104 and alpha 158-174 are highly exposed on the surface of the alpha subunit of membrane-bound AChR.

Monoclonal antibodies (mAbs) of predetermined specificity were prepared by immunizing with a free (i.e., not conjugated to any carrier) synthetic peptide representing region 15–22 (site 1) of sperm whale myoglobin (SpMb). The cross-reactions of Mb variants with three mAbs were studied in order to determine whether such interactions are influenced by substitutions outsde the site. Finback whale Mb, which has no substitutions within region 15–22, showed lower cross-reactivity and relative binding affinity than the reference antigen, SpMb. Bottle-nose Atlantic dolphin myoglobin (BdMb) and badger myoglobin (BgMb), although they have identical substitutions within region 15–22 (Ala-15 to Gly and Val-21 to Leu), showed very different binding properties. The cross-reaction of BdMb was quite comparable to that of SpMb, while that of BgMb was much lower. Since the two proteins have identical structures in regions 15–22, the differences in their cross-reactivities are readily attributed to the effects of substitutions outside this region. Another pair of myoglobins, horse myoglobins (HsMb) and chicken myoglobin (ChMb), also have two identical substitutions (Ala-15 to Gly and Val-21 to Ile) within region 15–22, but possessed different cross-reactivity. The results indicate that the reaction of mAbs, whose specificity is precisely known and predetermined by the immunizing free peptide, can be markedly affected by substitutions outside the indicated binding region on the protein.

Human glioma-associated markers can be exploited for the development of new diagnostic strategies and treatment modalities for these malignancies. A goat antiserum was first raised against human anaplastic astrocytoma (AC or AA) and glioblastoma multiforme (GB or GBM) extracts. Extensive sequential absorptions with normal brain tissue, normal serum, and human serum albumin (HSA) gave an antibody fraction specific for glioma. Balb/c mice were subsequently immunized with these glioma extracts. B-cell hybridomas from these mice were then cloned and subcloned by limiting dilution, yielding six monoclonal antibodies (MAbs) that were entirely specific for tumor tissues, and did not react with normal human serum or with normal human brain, liver, kidney, spleen, or muscle. Moreover, the murine MAbs did not cross-react with certain other human tumors, including melanoma. The fully absorbed antiserum and the murine MAbs both identify a polypeptide pattern possibly related to human glial fibrillary acidic protein (GFAP) or other intermediate filament proteins on immunoblots. These immunological reagents could serve as powerful tools for the diagnosis and possibly therapy of these uniformly fatal tumors.

Xenogeneic immunization of freshly-prepared human glioma extracts into goats has yielded a polyclonal antiserum, which after multiple absorptions specifically identifies antigenic entities only in glioma extracts, and not in appropriate controls, both by radioimmunoassays (RIAs) and Western immunoblots. The results from the absorbed polyclonal antiserum have been confirmed by the successful generation of six stable murine monoclonal antibodies (MAbs) which recognize a subset of the same antigens with high specificity on immunoblots and with no apparent cross-reactivities by RIA to normal brain, serum, liver, muscle, kidney, spleen, or melanoma tissues. Moreover, the tested murine MAbs (B12C4) reveal a striking and abundant glial filament protein, possibly related to glial fibrillary acidic protein (GFAP) or other intermediate filament proteins, by frozen-section immunofluorescence. This is seen only in gliomas and is absent, or dramatically reduced, in normal human cortex. Use of potent immortalizing strain (FF41) of Epstein-Barr virus (EBV) to establish antibody-secreting human lymphoblastoid lines, and the generation of mouse-human chimeric fusions, have yielded lines possessing variable supernatant human antibody secretion. Radioimmunoassays using culture supernatants, and sera from glioma patients and an normal individual, have demonstrated surprisingly similar reactivity profiles, even after a sensitive sandwich RIA employing the B6C6 murine MAb. These results suggest that, although human glioma-associated antigens, including possibly the up-regulation of GFAP expression, clearly exist, there seems to be a muted humoral response as evidenced by a paucity of tumor-specific B-cells. This may be due to antigenic shielding by the blood-brain barrier, or due to a form of immunological compromise in patients harboring these malignancies.

Human glioma-associated markers can be exploited for the development of new diagnostic strategies and treatment modalities for these malignancies. A goat antiserum was first raised against human anaplastic astrocytoma (AC or AA) and glioblastoma multiforme (GB or GBM) extracts. Extensive sequential absorptions with normal brain tissue, normal serum, and human serum albumin (HSA) gave an antibody fraction specific for glioma. Balb/c mice were subsequently immunized with these glioma extracts. B-cell hybridomas from these mice were then cloned and subcloned by limiting dilution, yielding six monoclonal antibodies (MAbs) that were entirely specific for tumor tissues, and did not react with normal human serum or with normal human brain, liver, kidney, spleen, or muscle. Moreover, the murine MAbs did not cross-react with certain other human tumors, including melanoma. The fully absorbed antiserum and the murine MAbs both identify a polypeptide pattern possibly related to human glial fibrillary acidic protein (GFAP) or other intermediate filament proteins on immunoblots. These immunological reagents could serve as powerful tools for the diagnosis and possibly therapy of these uniformly fatal tumors.