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Subtle affinity-enhancing mutations in a myelin oligodendrocyte glycoprotein-specific TCR alter specificity and generate new self-reactivity.

ABSTRACT: We describe a simple iterative approach to augment TCR affinity, which we studied using a myelin oligodendrocyte glycoprotein-specific TCR. We hypothesized that single amino acid modifications in TCR CDR3 could enhance TCR sensitivity through focal interactions with antigenic peptide while minimizing the risk of cross-reactivity observed previously in TCR more broadly mutagenized using in vitro evolution techniques. We show that this iterative method can indeed generate TCR with Ag sensitivity 100-fold greater than the parental receptor and can endow TCR with coreceptor independence. However, we also find that single amino acid mutations in the CDR3 can alter TCR fine specificity, affecting recognition requirements for Ag residues over most of the length of the MHC binding groove. Furthermore, minimal changes in surface-exposed CDR3 amino acids, even the addition of a single hydroxyl group or conversion of a methyl or sulfhydryl moiety to a hydroxyl, can confer modified Ag-specific TCR with new self-reactivity. In vivo modeling of modified TCR through retroviral TCR gene transfer into Rag(-/-) mice confirmed the biological significance of these altered reactivities, although it also demonstrated the feasibility of producing Ag-specific, positively selecting, coreceptor-independent receptors with markedly increased Ag sensitivity. These results affirm the possibility of readily generating affinity-enhanced TCR for therapeutic purposes but demonstrate that minimal changes in TCR CDR3 structure can promote self reactivity and thereby emphasize the importance of caution in validating receptors with even subtle alterations before clinical application.

SUBMITTER: Udyavar A

PROVIDER: S-EPMC2681418 | biostudies-literature | 2009 Apr

REPOSITORIES: biostudies-literature

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Subtle affinity-enhancing mutations in a myelin oligodendrocyte glycoprotein-specific TCR alter specificity and generate new self-reactivity.

Udyavar Akshata A Alli Rajshekhar R Nguyen Phuong P Baker Lesley L Geiger Terrence L TL

Journal of immunology (Baltimore, Md. : 1950) 20090401 7

We describe a simple iterative approach to augment TCR affinity, which we studied using a myelin oligodendrocyte glycoprotein-specific TCR. We hypothesized that single amino acid modifications in TCR CDR3 could enhance TCR sensitivity through focal interactions with antigenic peptide while minimizing the risk of cross-reactivity observed previously in TCR more broadly mutagenized using in vitro evolution techniques. We show that this iterative method can indeed generate TCR with Ag sensitivity 1 ...[more]

PMID: 19299745

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Project description:ImportanceMyelin oligodendrocyte glycoprotein-IgG1-associated disorder (MOGAD) is a distinct central nervous system-demyelinating disease. Positive results on MOG-IgG1 testing by live cell-based assays can confirm a MOGAD diagnosis, but false-positive results may occur.ObjectiveTo determine the positive predictive value (PPV) of MOG-IgG1 testing in a tertiary referral center.Design, setting, and participantsThis diagnostic study was conducted over 2 years, from January 1, 2018, through December 31, 2019. Patients in the Mayo Clinic who were consecutively tested for MOG-IgG1 by live cell-based flow cytometry during their diagnostic workup were included. Patients without research authorization were excluded.Main outcomes and measuresMedical records of patients who were tested were initially reviewed by 2 investigators blinded to MOG-IgG1 serostatus, and pretest probability was classified as high or low (suggestive of MOGAD or not). Testing of MOG-IgG1 used a live-cell fluorescence-activated cell-sorting assay; an IgG binding index value of 2.5 or more with an end titer of 1:20 or more was considered positive. Cases positive for MOG-IgG1 were independently designated by 2 neurologists as true-positive or false-positive results at last follow-up, based on current international recommendations on diagnosis or identification of alternative diagnoses; consensus was reached for cases in which disagreement existed.ResultsA total of 1617 patients were tested, and 357 were excluded. Among 1260 included patients tested over 2 years, the median (range) age at testing was 46 (0-98) years, and 792 patients were female (62.9%). A total of 92 of 1260 (7.3%) were positive for MOG-IgG1. Twenty-six results (28%) were designated as false positive by the 2 raters, with an overall agreement on 91 of 92 cases (99%) for true and false positivity. Alternative diagnoses included multiple sclerosis (n = 11), infarction (n = 3), B12 deficiency (n = 2), neoplasia (n = 2), genetically confirmed adrenomyeloneuropathy (n = 1), and other conditions (n = 7). The overall PPV (number of true-positive results/total positive results) was 72% (95% CI, 62%-80%) and titer dependent (PPVs: 1:1000, 100%; 1:100, 82%; 1:20-40, 51%). The median titer was higher with true-positive results (1:100 [range, 1:20-1:10000]) than false-positive results (1:40 [range, 1:20-1:100]; P < .001). The PPV was higher for children (94% [95% CI, 72%-99%]) vs adults (67% [95% CI, 56%-77%]) and patients with high pretest probability (85% [95% CI, 76%-92%]) vs low pretest probability (12% [95% CI, 3%-34%]). The specificity of MOG-IgG1 testing was 97.8%.Conclusions and relevanceThis study confirms MOG-IgG1 as a highly specific biomarker for MOGAD, but when using a cutoff of 1:20, it has a low PPV of 72%. Caution is advised in the interpretation of low titers among patients with atypical phenotypes, because ordering MOG-IgG1 in low pretest probability situations will increase the proportion of false-positive results.

Project description:Myelin oligodendrocyte glycoprotein (MOG), a member of the immunoglobulin (Ig) superfamily, is a myelin protein solely expressed at the outermost surface of myelin sheaths and oligodendrocyte membranes. This makes MOG a potential target of cellular and humoral immune responses in inflammatory demyelinating diseases. Due to its late postnatal developmental expression, MOG is an important marker for oligodendrocyte maturation. Discovered about 30 years ago, it is one of the best-studied autoantigens for experimental autoimmune models for multiple sclerosis (MS). Human studies, however, have yielded controversial results on the role of MOG, especially MOG antibodies (Abs), as a biomarker in MS. But with improved detection methods using different expression systems to detect Abs in patients' samples, this is meanwhile no longer the case. Using cell-based assays with recombinant full-length, conformationally intact MOG, several recent studies have revealed that MOG Abs can be found in a subset of predominantly pediatric patients with acute disseminated encephalomyelitis (ADEM), aquaporin-4 (AQP4) seronegative neuromyelitis optica spectrum disorders (NMOSD), monophasic or recurrent isolated optic neuritis (ON), or transverse myelitis, in atypical MS and in N-methyl-d-aspartate receptor-encephalitis with overlapping demyelinating syndromes. Whereas MOG Abs are only transiently observed in monophasic diseases such as ADEM and their decline is associated with a favorable outcome, they are persistent in multiphasic ADEM, NMOSD, recurrent ON, or myelitis. Due to distinct clinical features within these diseases it is controversially disputed to classify MOG Ab-positive cases as a new disease entity. Neuropathologically, the presence of MOG Abs is characterized by MS-typical demyelination and oligodendrocyte pathology associated with Abs and complement. However, it remains unclear whether MOG Abs are a mere inflammatory bystander effect or truly pathogenetic. This article provides deeper insight into recent developments, the clinical relevance of MOG Abs and their role in the immunpathogenesis of inflammatory demyelinating disorders.

Dataset Information

Subtle affinity-enhancing mutations in a myelin oligodendrocyte glycoprotein-specific TCR alter specificity and generate new self-reactivity.

Publications

Subtle affinity-enhancing mutations in a myelin oligodendrocyte glycoprotein-specific TCR alter specificity and generate new self-reactivity.

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