Low dystrophin variability between muscles and stable expression over time in Becker muscular dystrophy using capillary Western immunoassay

Becker muscular dystrophy (BMD) is the milder allelic variant of Duchenne muscular dystrophy, with higher dystrophin levels. To anticipate on results of interventions targeting dystrophin expression it is important to know the natural variation of dystrophin expression between different muscles and over time. Dystrophin was quantified using capillary Western immunoassay (Wes) in the anterior tibial (TA) muscle of 37 BMD patients. Variability was studied using two samples from the same TA biopsy site in nine patients, assessing nine longitudinal TA biopsies, and eight simultaneously obtained vastus lateralis (VL) muscle biopsies. Measurements were performed in duplicate with two primary antibodies. Baseline dystrophin levels were correlated to longitudinal muscle strength and functional outcomes. Results showed low technical variability and high precision for both antibodies. Dystrophin TA levels ranged from 4.8 to 97.7%, remained stable over a 3–5 year period, and did not correlate with changes in longitudinal muscle function. Dystrophin levels were comparable between TA and VL muscles. Intra-muscle biopsy variability was low (5.2% and 11.4% of the total variability of the two antibodies). These observations are relevant for the design of clinical trials targeting dystrophin production, and may urge the need for other biomarkers or surrogate endpoints.

Use of capillary Western immunoassay (Wes) for quantification of dystrophin levels in skeletal muscle of healthy controls and individuals with Becker and Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a neuromuscular disease characterized by progressive weakness of the skeletal and cardiac muscles. This X-linked disorder is caused by open reading frame disrupting mutations in the DMD gene, resulting in strong reduction or complete absence of dystrophin protein. In order to use dystrophin as a supportive or even surrogate biomarker in clinical studies on investigational drugs aiming at correcting the primary cause of the disease, the ability to reliably quantify dystrophin expression in muscle biopsies of DMD patients pre- and post-treatment is essential. Here we demonstrate the application of the ProteinSimple capillary immunoassay (Wes) method, a gel- and blot-free method requiring less sample, antibody and time to run than conventional Western blot assay. We optimized dystrophin quantification by Wes using 2 different antibodies and found it to be highly sensitive, reproducible and quantitative over a large dynamic range. Using a healthy control muscle sample as a reference and α-actinin as a protein loading/muscle content control, a panel of skeletal muscle samples consisting of 31 healthy controls, 25 Becker Muscle dystrophy (BMD) and 17 DMD samples was subjected to Wes analysis. In healthy controls dystrophin levels varied 3 to 5-fold between the highest and lowest muscle samples, with the reference sample representing the average of all 31 samples. In BMD muscle samples dystrophin levels ranged from 10% to 90%, with an average of 33% of the healthy muscle average, while for the DMD samples the average dystrophin level was 1.3%, ranging from 0.7% to 7% of the healthy muscle average. In conclusion, Wes is a suitable, efficient and reliable method for quantification of dystrophin expression as a biomarker in DMD clinical drug development.

Dystrophin levels and clinical severity in Becker muscular dystrophy patients

OBJECTIVE

Becker muscular dystrophy (BMD) is characterised by broad clinical variability. Ongoing studies exploring dystrophin restoration in Duchenne muscular dystrophy ask for better understanding of the relation between dystrophin levels and disease severity. We studied this relation in BMD patients with varying mutations, including a large subset with an exon 45-47 deletion.

METHODS

Dystrophin was quantified by western blot analyses in a fresh muscle biopsy of the anterior tibial muscle. Disease severity was assessed using quantitative muscle strength measurements and functional disability scoring. MRI of the leg was performed in a subgroup to detect fatty infiltration.

RESULTS

33 BMD patients participated. No linear relation was found between dystrophin levels (range 3%-78%) and muscle strength or age at different disease milestones, in both the whole group and the subgroup of exon 45-47 deleted patients. However, patients with less than 10% dystrophin all showed a severe disease course. No relation was found between disease severity and age when analysing the whole group. By contrast, in the exon 45-47 deleted subgroup, muscle strength and levels of fatty infiltration were significantly correlated with patients' age.

CONCLUSIONS

Our study shows that dystrophin levels appear not to be a major determinant of disease severity in BMD, as long as it is above approximately 10%. A significant relation between age and disease course was only found in the exon 45-47 deletion subgroup. This suggests that at higher dystrophin levels, the disease course depends more on the mutation site than on the amount of the dystrophin protein produced.

Systemic administration of PRO051 in Duchenne's muscular dystrophy

BACKGROUND

Local intramuscular administration of the antisense oligonucleotide PRO051 in patients with Duchenne's muscular dystrophy with relevant mutations was previously reported to induce the skipping of exon 51 during pre-messenger RNA splicing of the dystrophin gene and to facilitate new dystrophin expression in muscle-fiber membranes. The present phase 1-2a study aimed to assess the safety, pharmacokinetics, and molecular and clinical effects of systemically administered PRO051.

METHODS

We administered weekly abdominal subcutaneous injections of PRO051 for 5 weeks in 12 patients, with each of four possible doses (0.5, 2.0, 4.0, and 6.0 mg per kilogram of body weight) given to 3 patients. Changes in RNA splicing and protein levels in the tibialis anterior muscle were assessed at two time points. All patients subsequently entered a 12-week open-label extension phase, during which they all received PRO051 at a dose of 6.0 mg per kilogram per week. Safety, pharmacokinetics, serum creatine kinase levels, and muscle strength and function were assessed.

RESULTS

The most common adverse events were irritation at the administration site and, during the extension phase, mild and variable proteinuria and increased urinary α(1)-microglobulin levels; there were no serious adverse events. The mean terminal half-life of PRO051 in the circulation was 29 days. PRO051 induced detectable, specific exon-51 skipping at doses of 2.0 mg or more per kilogram. New dystrophin expression was observed between approximately 60% and 100% of muscle fibers in 10 of the 12 patients, as measured on post-treatment biopsy, which increased in a dose-dependent manner to up to 15.6% of the expression in healthy muscle. After the 12-week extension phase, there was a mean (±SD) improvement of 35.2±28.7 m (from the baseline of 384±121 m) on the 6-minute walk test.

CONCLUSIONS

Systemically administered PRO051 showed dose-dependent molecular efficacy in patients with Duchenne's muscular dystrophy, with a modest improvement in the 6-minute walk test after 12 weeks of extended treatment. (Funded by Prosensa Therapeutics; Netherlands National Trial Register number, NTR1241.).

Local dystrophin restoration with antisense oligonucleotide PRO051

BACKGROUND

Duchenne's muscular dystrophy is associated with severe, progressive muscle weakness and typically leads to death between the ages of 20 and 35 years. By inducing specific exon skipping during messenger RNA (mRNA) splicing, antisense compounds were recently shown to correct the open reading frame of the DMD gene and thus to restore dystrophin expression in vitro and in animal models in vivo. We explored the safety, adverse-event profile, and local dystrophin-restoring effect of a single, intramuscular dose of an antisense oligonucleotide, PRO051, in patients with this disease.

METHODS

Four patients, who were selected on the basis of their mutational status, muscle condition, and positive exon-skipping response to PRO051 in vitro, received a dose of 0.8 mg of PRO051 injected into the tibialis anterior muscle. A biopsy was performed 28 days later. Safety measures, composition of mRNA, and dystrophin expression were assessed.

RESULTS

PRO051 injection was not associated with clinically apparent adverse events. Each patient showed specific skipping of exon 51 and sarcolemmal dystrophin in 64 to 97% of myofibers. The amount of dystrophin in total protein extracts ranged from 3 to 12% of that found in the control specimen and from 17 to 35% of that of the control specimen in the quantitative ratio of dystrophin to laminin alpha2.

CONCLUSIONS

Intramuscular injection of antisense oligonucleotide PRO051 induced dystrophin synthesis in four patients with Duchenne's muscular dystrophy who had suitable mutations, suggesting that further studies might be feasible.

Antisense-induced exon skipping restores dystrophin expression in DMD patient derived muscle cells

Due to frame-shifting mutations in the DMD gene that cause dystrophin deficiency, Duchenne muscular dystrophy (DMD) patients suffer from lethal muscle degeneration. In contrast, mutations in the allelic Becker muscular dystrophy (BMD) do not disrupt the translational reading frame, resulting in a less severe phenotype. In this study, we explored a genetic therapy aimed at restoring the reading frame in muscle cells from DMD patients through targeted modulation of dystrophin pre-mRNA splicing. Considering that exon 45 is the single most frequently deleted exon in DMD, whereas exon (45+46) deletions cause only a mild form of BMD, we set up an antisense-based system to induce exon 46 skipping from the transcript in cultured myotubes of both mouse and human origin. In myotube cultures from two unrelated DMD patients carrying an exon 45 deletion, the induced skipping of exon 46 in only approximately 15% of the mRNA led to normal amounts of properly localized dystrophin in at least 75% of myotubes. Our results provide first evidence of highly effective restoration of dystrophin expression from the endogenous gene in DMD patient-derived muscle cells. This strategy may be applicable to not only >65% of DMD mutations, but also many other genetic diseases.

HLA-class II-associated control of antigen recognition by T cells in leprosy: a prominent role for the 30/31-kDa antigens

The recognition of 16 mycobacterial Ags by a panel of T cell lines from leprosy patients and healthy exposed individuals from an endemic population was examined within the context of expressed HLA-DR molecules. Although overall no significant differences were found between the frequencies of Ag recognition in the different subject groups, when Ag-specific T cell responses were examined within the context of HLA-DR, a highly significant difference was found in the recognition of the 30/31-kDa Ag. HLA-DR3 appeared to be associated with high T cell responsiveness to the 30/31-kDa Ag in healthy contacts (p = 0.01), but, conversely, with low T cell responsiveness to this Ag in tuberculoid patients (p = 0.005). Within the group of HLA-DR3-positive individuals, differences in 30/31-kDa directed T cell responsiveness were highly significant not only between healthy individuals and tuberculoid patients (p < 0. 0001), but also between healthy individuals and lepromatous patients (p = 0.009), and consequently between healthy individuals compared with leprosy patients as a group (p < 0.0001). A dominant HLA-DR3-restricted epitope was recognized by healthy contacts in this population. It has been proposed that secreted Ags may dominate acquired immunity early in infection. The low T cell response to the secreted, immunodominant 30/31-kDa Ag in HLA-DR3-positive leprosy patients in this population may result in retarded macrophage activation and delayed bacillary clearance, which in turn may lead to enhanced Ag load followed by T cell-mediated immunopathology.

IL-2 and IL-12 act in synergy to overcome antigen-specific T cell unresponsiveness in mycobacterial disease

IL-12 secretion by APC is critical for the development of protective Th1-type responses in mycobacterial (Mycobacterium avium and Mycobacterium tuberculosis) infections in mice. We have studied the role of IL-12 and IL-2 in the generation of Mycobacterium leprae-specific T cell responses in humans. Leprosy patients were defined as low/nonresponders or high responders based on the level of T cell proliferation in M. leprae-stimulated PBMC. In high responders, M. leprae-induced proliferation was markedly suppressed by neutralizing anti-IL-12 mAb (inhibition 55 +/- 6%). Neutralization of IL-2 activity resulted in an inhibition of 77 +/- 4%. Given the importance of endogenous IL-2 and IL-12 in M. leprae-induced responses, we investigated the ability of rIL-2 and rIL-12 to reverse T cell unresponsiveness in low/nonresponder patients. Interestingly, rIL-12 and rIL-2 strongly synergized in restoring both M. leprae-specific T cell proliferation and IFN-gamma secretion almost completely to the level of responder patients. A similar synergy between rIL-2 and rIL-12 was also observed in high responders when suboptimal M. leprae concentrations were used for T cell stimulation. Our data demonstrate a crucial role for endogenous IL-12 and IL-2 in M. leprae-induced T cell activation. Most importantly, we show that rIL-2 and rIL-12 act in synergy to overcome Ag-specific Th1 cell unresponsiveness. These findings may be applicable to the design of antimicrobial and antitumor vaccines.

IL-2 and IL-12 act in synergy to overcome antigen-specific T cell unresponsiveness in mycobacterial disease

IL-12 secretion by APC is critical for the development of protective Th1-type responses in mycobacterial (Mycobacterium avium and Mycobacterium tuberculosis) infections in mice. We have studied the role of IL-12 and IL-2 in the generation of Mycobacterium leprae-specific T cell responses in humans. Leprosy patients were defined as low/nonresponders or high responders based on the level of T cell proliferation in M. leprae-stimulated PBMC. In high responders, M. leprae-induced proliferation was markedly suppressed by neutralizing anti-IL-12 mAb (inhibition 55 +/- 6%). Neutralization of IL-2 activity resulted in an inhibition of 77 +/- 4%. Given the importance of endogenous IL-2 and IL-12 in M. leprae-induced responses, we investigated the ability of rIL-2 and rIL-12 to reverse T cell unresponsiveness in low/nonresponder patients. Interestingly, rIL-12 and rIL-2 strongly synergized in restoring both M. leprae-specific T cell proliferation and IFN-gamma secretion almost completely to the level of responder patients. A similar synergy between rIL-2 and rIL-12 was also observed in high responders when suboptimal M. leprae concentrations were used for T cell stimulation. Our data demonstrate a crucial role for endogenous IL-12 and IL-2 in M. leprae-induced T cell activation. Most importantly, we show that rIL-2 and rIL-12 act in synergy to overcome Ag-specific Th1 cell unresponsiveness. These findings may be applicable to the design of antimicrobial and antitumor vaccines.

Analysis of T-cell and B-cell responses to recombinant M. leprae antigens in leprosy patients and in healthy contacts: significant T-cell responses to antigens in M. leprae nonresponders

The recognition of a panel of recombinant Mycobacterium leprae antigens by T cells and B cells from 29 borderline tuberculoid/tuberculoid (BT/TT) and 18 lepromatous leprosy (LL) patients and from 21 healthy controls (HC) in leprosy-endemic regions of Ethiopia was examined. All 11 antigenic molecules tested (including M. leprae hsp 10, hsp18, hsp65 and several novel M. leprae antigens) were shown to be recognized by T cells, but clear quantitative differences existed between reactivities induced by individual antigens. Similar quantitative differences were observed when antibody responses to hsp10 and hsp65 antigens were determined. No associations were found between the antigen-specific responses and the subject status of either BT/TT and LL patients or HC. Fifteen percent of the patients who were nonresponsive to sonicates of M. leprae showed significant T-cell responses to one or more individual M. leprae antigens. This indicates that M. leprae constituents other than the proteins tested are responsible for the M. leprae-specific nonresponsiveness in these patients, which may be exploited for the design of vaccines or immunotherapeutic modalities aimed at inducing M. leprae-specific immunity in nonresponders.

A Mycobacterium leprae-specific gene encoding an immunologically recognized 45 kDa protein

By screening a Mycobacterium leprae lambda gt11 expression library with a serum from an Ethiopian lepromatous leprosy (LL) patient a clone was isolated (LL4) belonging to hybridization group III of a panel of previously isolated M. leprae clones. Members of this hybridization group encode a serologically recognized 45 kDa protein. The complete DNA sequences of the partially overlapping clones LL4 and L1 (hybridization group III) are presented and these revealed the presence of an open reading frame (ORF) predicting a protein with a molecular size of 42,448 Da. Southern hybridizations on total genomic DNA of M. leprae, Mycobacterium tuberculosis and eight atypical mycobacteria showed that the LL4 DNA fragment is specific for M. leprae DNA even under low-stringency conditions. The M. leprae specificity of LL4 DNA was further confirmed by the polymerase chain reaction using four different sets of primers. Western blotting analyses showed that the M. leprae 45 kDa protein is frequently recognized by antibodies from leprosy patients and that this recognition is specific since no antibodies could be detected in sera of tuberculosis patients. T-cell proliferation assays also demonstrated T-cell recognition by leprosy patients and healthy contacts of the M. leprae 45 kDa protein. The specificity of the LL4 DNA region and the 45 kDa antigen that is encoded by hybridization group III could provide unique tools for the development of M. leprae-specific immunological and DNA reagents.

The Mycobacterium leprae antigen 85 complex gene family: identification of the genes for the 85A, 85C, and related MPT51 proteins

The genes for two novel members (designated 85A and 85C) of the Mycobacterium leprae antigen 85 complex family of proteins and the gene for the closely related M. leprae MPT51 protein were isolated. The complete DNA sequence of the M. leprae 85C gene and partial sequences of the 85A and MPT51 genes are presented. As in M. tuberculosis, the M. leprae 85A, 85C, and previously identified 85B component genes are not closely linked on the genome. However, the MPT51 genes of both species localize close to the respective 85A component genes. Like the 85B component, the M. leprae 85A-MPT51 and 85C antigens are recognized by T cells from healthy contacts and leprosy patients.

Functional analysis of DR17(DR3)-restricted mycobacterial T cell epitopes reveals DR17-binding motif and enables the design of allele-specific competitor peptides

We have previously shown that p3-13 (KTIAY-DEEARR) of the 65-kDa heat shock protein (hsp65) of Mycobacterium tuberculosis and Mycobacterium leprae is selected as an important T cell epitope in HLA-DR17+ individuals, by selectively binding to (a pocket in) DR17 molecules, the major subset of the DR3 specificity. We have now further studied the interaction between p3-13, HLA-DR17 and four different TCR (V beta 5.1, V beta 1, and V beta 4) by using T cell stimulation assays, direct peptide-DR binding assays, and a large panel (n = 240) of single amino acid substitution analogs of p3-13. We find that residues 5(I) and 8(D) of p3-13 are important DR17 binding residues, whereas the residues that interact with the TCR vary slightly for each DR17-restricted clone. By using N- and C-terminal truncated derivatives of p2-20 we defined the minimal peptide length for both HLA-DR17 binding and T cell activation: the minimal peptide that bound to DR17 was seven amino acids long whereas the minimal peptide that activated T cell proliferation was eight amino acids in length. Furthermore, two new DR17-restricted epitopes were identified on hsp70 and hsp18 of M. leprae. Alignment of the critical DR17-binding residues 5(I) and 8(D) of p3-13 with these two novel epitopes and two other DR17-binding peptides revealed the presence of highly conserved amino acids at positions n and n + 3 with I, L, and V at position n and D and E at position n + 3. D and E are particularly likely to interact with the DR17-specific, positively charged pocket that we have defined earlier. Based on these results, a set of single amino acid substituted analogs that failed to activate these T cell clones but still bound specifically to DR17 was defined and tested for their ability to inhibit T cell activation by p3-13 or other DR17-restricted epitopes. Those peptides were able to inhibit the response to p3-13 as well as other DR17-restricted mycobacterial epitopes in an allele-specific manner, and are anticipated to be of potential use for immunotherapeutic and vaccine design strategies.

Functional analysis of DR17(DR3)-restricted mycobacterial T cell epitopes reveals DR17-binding motif and enables the design of allele-specific competitor peptides

We have previously shown that p3-13 (KTIAY-DEEARR) of the 65-kDa heat shock protein (hsp65) of Mycobacterium tuberculosis and Mycobacterium leprae is selected as an important T cell epitope in HLA-DR17+ individuals, by selectively binding to (a pocket in) DR17 molecules, the major subset of the DR3 specificity. We have now further studied the interaction between p3-13, HLA-DR17 and four different TCR (V beta 5.1, V beta 1, and V beta 4) by using T cell stimulation assays, direct peptide-DR binding assays, and a large panel (n = 240) of single amino acid substitution analogs of p3-13. We find that residues 5(I) and 8(D) of p3-13 are important DR17 binding residues, whereas the residues that interact with the TCR vary slightly for each DR17-restricted clone. By using N- and C-terminal truncated derivatives of p2-20 we defined the minimal peptide length for both HLA-DR17 binding and T cell activation: the minimal peptide that bound to DR17 was seven amino acids long whereas the minimal peptide that activated T cell proliferation was eight amino acids in length. Furthermore, two new DR17-restricted epitopes were identified on hsp70 and hsp18 of M. leprae. Alignment of the critical DR17-binding residues 5(I) and 8(D) of p3-13 with these two novel epitopes and two other DR17-binding peptides revealed the presence of highly conserved amino acids at positions n and n + 3 with I, L, and V at position n and D and E at position n + 3. D and E are particularly likely to interact with the DR17-specific, positively charged pocket that we have defined earlier. Based on these results, a set of single amino acid substituted analogs that failed to activate these T cell clones but still bound specifically to DR17 was defined and tested for their ability to inhibit T cell activation by p3-13 or other DR17-restricted epitopes. Those peptides were able to inhibit the response to p3-13 as well as other DR17-restricted mycobacterial epitopes in an allele-specific manner, and are anticipated to be of potential use for immunotherapeutic and vaccine design strategies.

Mycobacteria contain two groEL genes: the second Mycobacterium leprae groEL gene is arranged in an operon with groES

In contrast to other bacterial species, mycobacteria were thus far considered to contain groEL and groES genes that are present on separate loci on their chromosomes, Here, by screening a Mycobacterium leprae lambda gt11 expression library with serum from an Ethiopian lepromatous leprosy patient, two DNA clones were isolated that contain a groEL gene arranged in an operon with a groES gene. The complete DNA sequence of this groESL operon was determined. The predicted amino acid sequences of the GroES and GroEL proteins encoded by this operon are 85-90% and 59-61% homologous to the sequences from previously characterized mycobacterial GroES and GroEL proteins. Southern blotting analyses with M. leprae groES- and groEL-specific probes demonstrate that similar groESL homologous DNA is present in the genomes of other mycobacteria, including Mycobacterium tuberculosis. This strongly suggests that mycobacteria contain a groESL operon in addition to a separately arranged second groEL gene. Using five T-cell clones from two leprosy patients as probes, expression of the M. leprae GroES protein in Escherichia coli after heat shock was demonstrated. Four of these clones recognized the same M. leprae-specific GroES-derived peptide in a DR2-restricted fashion. No expression of the groEL gene from this operon was detected in E. coli after heat shock, as tested with a panel of T-cell clones and monoclonal antibodies reactive to previously described GroEL proteins of mycobacteria.

Molecular and immunological analysis of a fibronectin-binding protein antigen secreted by Mycobacterium leprae

By screening a Mycobacterium leprae lambda gt11 genomic DNA library with leprosy-patient sera we have previously identified 50 recombinant clones that expressed novel M. leprae antigens (Sathish et al., 1990). In this study, we show by DNA sequencing and immunoblot analysis that three of these clones express a M. leprae homologue of the fibronectin-binding antigen 85 complex of mycobacteria. The complete gene was characterized and it encodes a 327-amino-acid polypeptide, consisting of a consensus signal sequence of 38 amino acids followed by a mature protein of 289 amino acids. This is the first sequence of a member of the M. leprae antigen 85 complex, and Southern blotting analysis indicated the presence of multiple genes of the 85 complex in the genome of M. leprae. The amino acid sequence displays 75-85% sequence identity with components of the antigen 85 complex from M. tuberculosis, M. bovis BCG and M. kansasii. Furthermore, antibodies to the antigen 85 complex of M. tuberculosis and M. bovis BCG reacted with two fusion proteins containing the amino acid regions 55-266 and 266-327 of the M. leprae protein. The M. leprae 30/31 kDa protein induces strong humoral and cellular responses, as judged by Western blot analysis with patient sera and proliferation of T cells derived from healthy individuals and leprosy patients. Amino acid regions 55-266 and 265-327 both were shown to bind to fibronectin, indicating the presence of at least two fibronectin-binding sites on the M. leprae protein. These data indicate that this 30/31 kDa protein is not only important in the immune response against M. leprae, but may also have a biological role in the interaction of this bacillus with the human host.

A systematic molecular analysis of the T cell-stimulating antigens from Mycobacterium leprae with T cell clones of leprosy patients. Identification of a novel M. leprae HSP 70 fragment by M. leprae-specific T cells

Both protective immunity and immunopathology induced by mycobacteria are dependent on Ag-specific, CD4+ MHC class II-restricted T lymphocytes. The identification of Ag recognized by T cells is fundamental to the understanding of protective and pathologic immunity as well as to the design of effective immunoprophylaxis and immunotherapy strategies. Although some T cell clones are known to respond to recombinant mycobacterial heat shock proteins (hsp) like hsp3 65, the specificity of most T cells has remained unknown. We therefore have undertaken a specificity analysis of 48 well defined Mycobacterium leprae- and/or Mycobacterium tuberculosis-reactive (Th-1-like) T cell clones. Most clones (n = 44) were derived from different leprosy patients, and the remainder from one healthy control. Their HLA restriction molecules were DR2, DR3, DR4, DR5, DR7, DQ, or DP. T cell clones were stimulated with large numbers (n = 20 to 40) of mycobacterial SDS-PAGE-separated fractions bound to nitrocellulose. Each clone recognized a single fraction or peak with a particular Mr range. Some of the clones (n = 7) recognized the fraction that contained the hsp 65 as confirmed with the recombinant Ag. Most clones (n = 41), however, responded to Ag other than the hsp 65. Nine clones responded to a 67- to 80-kDa fraction. Five of them responded also to an ATP-purified, 70-kDa M. leprae protein, but only one of these five (that was HLA-DR2 restricted and cross-reactive with M. tuberculosis) recognized the recombinant C-terminal half (amino acids 278-621) of the M. leprae hsp 70 molecule and also recognized the recombinant M. tuberculosis hsp 70. We therefore have used the 5' part of the M. leprae hsp 70 gene that we have cloned recently. This fragment (that encodes amino acids 6-279) was indeed recognized by the other four M. leprae-specific T cells that were all HLA-DR3 restricted and did not cross-react with the highly homologous (95%) M. tuberculosis hsp 70. These results suggest that this novel fragment is a relevant T cell-stimulating Ag for leprosy patients. A panel of other recombinant Ag, including hsp 18 was tested. The majority of T cell clones appeared to recognize antigenic fractions distinct from hsp. In conclusion, T cells of leprosy patients see a large variety of different Ag including non-hsp, and one newly recognized moiety is the N-terminal M. leprae hsp 70 fragment.(ABSTRACT TRUNCATED AT 400 WORDS)

A systematic molecular analysis of the T cell-stimulating antigens from Mycobacterium leprae with T cell clones of leprosy patients. Identification of a novel M. leprae HSP 70 fragment by M. leprae-specific T cells

Both protective immunity and immunopathology induced by mycobacteria are dependent on Ag-specific, CD4+ MHC class II-restricted T lymphocytes. The identification of Ag recognized by T cells is fundamental to the understanding of protective and pathologic immunity as well as to the design of effective immunoprophylaxis and immunotherapy strategies. Although some T cell clones are known to respond to recombinant mycobacterial heat shock proteins (hsp) like hsp3 65, the specificity of most T cells has remained unknown. We therefore have undertaken a specificity analysis of 48 well defined Mycobacterium leprae- and/or Mycobacterium tuberculosis-reactive (Th-1-like) T cell clones. Most clones (n = 44) were derived from different leprosy patients, and the remainder from one healthy control. Their HLA restriction molecules were DR2, DR3, DR4, DR5, DR7, DQ, or DP. T cell clones were stimulated with large numbers (n = 20 to 40) of mycobacterial SDS-PAGE-separated fractions bound to nitrocellulose. Each clone recognized a single fraction or peak with a particular Mr range. Some of the clones (n = 7) recognized the fraction that contained the hsp 65 as confirmed with the recombinant Ag. Most clones (n = 41), however, responded to Ag other than the hsp 65. Nine clones responded to a 67- to 80-kDa fraction. Five of them responded also to an ATP-purified, 70-kDa M. leprae protein, but only one of these five (that was HLA-DR2 restricted and cross-reactive with M. tuberculosis) recognized the recombinant C-terminal half (amino acids 278-621) of the M. leprae hsp 70 molecule and also recognized the recombinant M. tuberculosis hsp 70. We therefore have used the 5' part of the M. leprae hsp 70 gene that we have cloned recently. This fragment (that encodes amino acids 6-279) was indeed recognized by the other four M. leprae-specific T cells that were all HLA-DR3 restricted and did not cross-react with the highly homologous (95%) M. tuberculosis hsp 70. These results suggest that this novel fragment is a relevant T cell-stimulating Ag for leprosy patients. A panel of other recombinant Ag, including hsp 18 was tested. The majority of T cell clones appeared to recognize antigenic fractions distinct from hsp. In conclusion, T cells of leprosy patients see a large variety of different Ag including non-hsp, and one newly recognized moiety is the N-terminal M. leprae hsp 70 fragment.(ABSTRACT TRUNCATED AT 400 WORDS)

Diversity in antigen recognition by Mycobacterium tuberculosis-reactive T cell clones from the synovial fluid of rheumatoid arthritis patients

In a previous study we have shown that synovial fluid mononuclear cells from many rheumatoid arthritis (RA) patients exhibit an enhanced response to M. tuberculosis antigens as compared to peripheral blood mononuclear cells. The 65-kDa heat-shock protein of M. tuberculosis was shown not to play an important role in this response, therefore other mycobacterial proteins must be involved. In this study we have investigated the possibility that synovial fluid T cells from RA patients predominantly recognize a limited number of M. tuberculosis antigens, as a result of a lesion-specific activation of only those M. tuberculosis-reactive T cells that have cross-reacted with joint-related autoantigens. From the synovial fluid of four RA patients M. tuberculosis-reactive T cell clones were isolated and analyzed for their phenotype, HLA-DR restriction and proliferation to immunoblot fractions containing sodium dodecyl sulfate-polyacrylamide gel-separated M. tuberculosis proteins of known molecular weight range. The overall M. tuberculosis immunoblot recognition pattern of the clones was strikingly heterogeneous. Within a panel of 15 clones 12 different antigenic specificities could be distinguished. In other words, we did not observe a dominant recognition of a few M. tuberculosis antigens by synovial fluid T cells. This argues against the hypothesis that the elevated synovial T cell reactivity against M. tuberculosis is a reflection of an in vivo expansion of a limited number of different types of M. tuberculosis-reactive T cells as a result of a cross-reaction with putative joint autoantigens.

Use of flanking sequences to study secondary structure-activity correlations of a Mycobacterium leprae T cell epitope

The 65-kDa protein of the intracellular pathogen M. leprae is prominent in the immune response to this mycobacterium, and individual T cell epitopes from this protein sequence have been defined. We have tested the stimulatory activity of extended analogs of the minimal peptide representing one such epitope, LQAAPALDKL, with a variety of tetrapeptide extensions added to enhance or destabilize alpha helix formation. The conformational potential of the peptides was measured by circular dichroism using aqueous trifluoroethanol as a secondary structure inducer. Although analogs with high helical potential activated T cells at low concentrations, a less helical variant was similarly potent. Activity also did not correlate with predicted overall alpha helical amphipathicity. One analog was found which stimulated T cell proliferation in the 50 pM range. The effect of tetrapeptide extensions on epitope activity is not consistent with the importance in activity of only a single stable secondary structure such as an alpha helix.

A Mycobacterium leprae-specific human T cell epitope cross-reactive with an HLA-DR2 peptide

Mycobacterium leprae induces T cell reactivity and protective immunity in the majority of exposed individuals, but the minority that develop leprosy exhibit various types of immunopathology. Thus, the definition of epitopes on M. leprae antigens that are recognized by T cells from different individuals might result in the development of an effective vaccine against leprosy. A sequence from the 65-kD protein of this organism was recognized by two HLA-DR2-restricted, M. leprae-specific helper T cell clones that were derived from a tuberculoid leprosy patient. Synthetic peptides were used to define this epitope as Leu-Gln-Ala-Ala-Pro-Ala-Leu-Asp-Lys-Leu. A similar peptide that was derived from the third hypervariable region of the HLA-DR2 chain, Glu-Gln-Ala-Arg-Ala-Ala-Val-Asp-Thr-Tyr, also activated the same clones. The unexpected cross-reactivity of this M. leprae-specific DR2-restricted T cell epitope with a DR2 peptide may have to be considered in the design of subunit vaccines against leprosy.

Use of recombinant antigens expressed in Escherichia coli K-12 to map B-cell and T-cell epitopes on the immunodominant 65-kilodalton protein of Mycobacterium bovis BCG

In gene libraries of Mycobacterium bovis BCG, Mycobacterium tuberculosis, and Mycobacterium leprae, recombinants were frequently encountered that expressed an immunodominant 65-kilodalton (kDa) protein antigen that was shown to react with a high proportion of mycobacterium-reactive human and murine T cells and murine monoclonal antibodies. In this study, recombinant antigens were used to map T-cell and B-cell epitopes on the M. bovis BCG 65-kDa protein that was previously designated MbaA. Four different T-cell-epitope-containing regions (amino acid residues 1 through 16, 17 through 61, 85 through 108, and 235 through 279) were defined that were recognized by seven T-cell clones from patients with tuberculoid leprosy. These regions are distinct from two previously described T-cell epitopes recognized by T cells from a tuberculosis patient. As T-cell clones restricted by different class II determinants were shown to be specific for different regions on the 65-kDa protein, the presented data suggested that the products of different human leukocyte antigen class II loci and alleles present different parts of MbaA to the immune system. B-cell epitopes recognized by 20 monoclonal antibodies were assigned to eight different regions of MbaA. Using 15 of these antibodies, we previously showed that MbaA was antigenically related to a common antigen present in many bacterial species. The dispersed localization of the involved epitopes defined here shows that various different parts of MbaA are indeed conserved. These results show that well-defined recombinant antigens are useful tools for the localization of both B- and T-cell-epitope-containing regions of a protein. Peptides synthesized from the sequences of such regions may then exactly define the epitopes relevant for the development of specific diagnostic tests or of vaccines against mycobacteria.