Generation and characterization of HLA-A2 transgenic mice expressing the human TCR 1G4 specific for the HLA-A2 restricted NY-ESO-1157-165 tumor-specific peptide.

BACKGROUND: NY-ESO-1 is a tumor-specific, highly immunogenic, human germ cell antigen of the MAGE-1 family that is a promising vaccine and cell therapy candidate in clinical trial development. The mouse genome does not encode an NY-ESO-1 homolog thereby not subjecting transgenic T-cells to thymic tolerance mechanisms that might impair in-vivo studies. We hypothesized that an NY-ESO-1 T cell receptor (TCR) transgenic mouse would provide the unique opportunity to study avidity of TCR response against NY-ESO-1 for tumor vaccine and cellular therapy development against this clinically relevant and physiological human antigen. METHODS: To study in vitro and in vivo the requirements for shaping an effective T cell response against the clinically relevant NY-ESO-1, we generated a C57BL/6 HLA-A*0201 background TCR transgenic mouse encoding the 1G4 TCR specific for the human HLA-A2 restricted, NY-ESO-1157-165 SLLMWITQC (9C), initially identified in an NY-ESO-1 positive melanoma patient. RESULTS: The HLA-A*0201 restricted TCR was positively selected on both CD4+ and CD8+ cells. Mouse 1G4 T cells were not activated by endogenous autoimmune targets or a large library of non-cognate viral antigens. In contrast, their activation by HLA-A2 NY-ESO-1157-165 complexes was evident by proliferation, CD69 upregulation, interferon-γ production, and interleukin-2 production, and could be tuned using a twofold higher affinity altered peptide ligand, NY-ESO-1157-165V. NY-ESO-1157-165V recombinant vaccination of syngeneic mice adoptively transferred with m1G4 CD8+ T cells controlled tumor growth in vivo. 1G4 transgenic mice suppressed growth of syngeneic methylcholanthrene (MCA) induced HHD tumor cells expressing the full-length human NY-ESO-1 protein but not MCA HHD tumor cells lacking NY-ESO-1. CONCLUSIONS: The 1G4 TCR mouse model for the physiological human TCR against the clinically relevant antigen, NY-ESO-1, is a valuable tool with the potential to accelerate clinical development of NY-ESO-1-targeted T-cell and vaccine therapies.

Hybrid Gene Origination Creates Human-Virus Chimeric Proteins during Infection.

RNA viruses are a major human health threat. The life cycles of many highly pathogenic RNA viruses like influenza A virus (IAV) and Lassa virus depends on host mRNA, because viral polymerases cleave 5'-m7G-capped host transcripts to prime viral mRNA synthesis ("cap-snatching"). We hypothesized that start codons within cap-snatched host transcripts could generate chimeric human-viral mRNAs with coding potential. We report the existence of this mechanism of gene origination, which we named "start-snatching." Depending on the reading frame, start-snatching allows the translation of host and viral "untranslated regions" (UTRs) to create N-terminally extended viral proteins or entirely novel polypeptides by genetic overprinting. We show that both types of chimeric proteins are made in IAV-infected cells, generate T cell responses, and contribute to virulence. Our results indicate that during infection with IAV, and likely a multitude of other human, animal and plant viruses, a host-dependent mechanism allows the genesis of hybrid genes.

Results of hydroxyapatite ceramic coated primary femoral stem in revision total hip replacement.

PURPOSE: The purpose of this study was to assess survival rate, functional and radiological outcomes when using a hydroxyapatite-ceramic fully coated primary femoral stem in revision total hip arthroplasty. METHODS: Patients who underwent revision total hip arthroplasty using the Furlong hydroxyapatite-ceramic (HAC)-coated (Joint Replacement Instrumentation Ltd., Sheffield, UK) primary stem were retrospectively identified between 2013 and 2017. A total of 30 hips in 27 patients were identified and the mean follow-up duration was 44 months. Post-operative radiographs were scrutinized for signs of component loosening by two independent assessors. Patient's functional outcomes were assessed using the Oxford hip score and compared pre- and post-operatively. The prevalence of thigh pain was assessed at the latest follow-up. RESULTS: The most common cause of revision was adverse reactions to metal debris (ARMD) (46.6%). The overall complication rate was 13.3%. Results at final follow-up demonstrated 100% survival rate and no reported incidence of thigh pain. Using paired t test, all patients had a statistically significant (P < 0.05) improvement in post-operative mean Oxford hip score of 35 compared to a mean pre-operative score of 14. Radiographic analysis of the latest follow-up radiographs revealed no signs of component loosening or component subsidence. CONCLUSION: With a 100% survival rate and excellent reported functional outcomes, we believe that our experience and results support the use of primary cementless stems in selected revision cases.

Effectiveness of water-saving technologies during early stages of restoration of endemic Opuntia cacti in the Galápagos Islands, Ecuador.

Restoration of keystone species is a primary strategy used to combat biodiversity loss and recover ecological services. This is particularly true for oceanic islands, which despite their small land mass, host a large fraction of the planet's imperiled species. The endemic Opuntia spp. cacti are one example and a major focus for restoration in the Galápagos archipelago, Ecuador. These cacti are keystone species that support much of the unique vertebrate animal community in arid zones, yet human activities have substantially reduced Opuntia populations. Extreme aridity poses an obstacle for quickly restoring Opuntia populations though water-saving technologies may provide a solution. The aim of this study was to evaluate current restoration efforts and the utility of two water-saving technologies as tools for the early stages of restoring Opuntia populations in the Galápagos archipelago. We planted 1,425 seedlings between 2013 and 2018, of which 66% had survived by the end of 2018. Compared with no-technology controls, seedlings planted with Groasis Waterboxx® water-saving technology (polypropylene trays with water reservoir and protective refuge for germinants) had a greater rate of survival in their first two-years of growth on one island (Plaza Sur) and greater growth rate on four islands whereas the "Cocoon" water-saving technology (similar technology but made of biodegradable fiber) did not affect growth and actually reduced seedling survival. Survival and growth rate were also influenced by vegetation zone, elevation, and precipitation in ways largely contingent on island. Overall, our findings suggest that water-saving technologies are not always universally applicable but can substantially increase the survival and growth rate of seedlings in certain conditions, providing in some circumstances a useful tool for improving restoration outcomes for rare plants of arid ecosystems.

Vaccine induction of antibodies and tissue-resident CD8+ T cells enhances protection against mucosal SHIV-infection in young macaques.

Antibodies and cytotoxic T cells represent 2 arms of host defense against pathogens. We hypothesized that vaccines that induce both high-magnitude CD8+ T cell responses and antibody responses might confer enhanced protection against HIV. To test this hypothesis, we immunized 3 groups of nonhuman primates: (a) Group 1, which includes sequential immunization regimen involving heterologous viral vectors (HVVs) comprising vesicular stomatitis virus, vaccinia virus, and adenovirus serotype 5-expressing SIVmac239 Gag; (b) Group 2, which includes immunization with a clade C HIV-1 envelope (Env) gp140 protein adjuvanted with nanoparticles containing a TLR7/8 agonist (3M-052); and (c) Group 3, which includes a combination of both regimens. Immunization with HVVs induced very high-magnitude Gag-specific CD8+ T cell responses in blood and tissue-resident CD8+ memory T cells in vaginal mucosa. Immunization with 3M-052 adjuvanted Env protein induced robust and persistent antibody responses and long-lasting innate responses. Despite similar antibody titers in Groups 2 and 3, there was enhanced protection in the younger animals in Group 3, against intravaginal infection with a heterologous SHIV strain. This protection correlated with the magnitude of the serum and vaginal Env-specific antibody titers on the day of challenge. Thus, vaccination strategies that induce both CD8+ T cell and antibody responses can confer enhanced protection against infection.

Ribosomal Proteins Regulate MHC Class I Peptide Generation for Immunosurveillance.

The MHC class I antigen presentation system enables T cell immunosurveillance of cancers and viruses. A substantial fraction of the immunopeptidome derives from rapidly degraded nascent polypeptides (DRiPs). By knocking down each of the 80 ribosomal proteins, we identified proteins that modulate peptide generation without altering source protein expression. We show that 60S ribosomal proteins L6 (RPL6) and RPL28, which are adjacent on the ribosome, play opposite roles in generating an influenza A virus-encoded peptide. Depleting RPL6 decreases ubiquitin-dependent peptide presentation, whereas depleting RPL28 increases ubiquitin-dependent and -independent peptide presentation. 40S ribosomal protein S28 (RPS28) knockdown increases total peptide supply in uninfected cells by increasing DRiP synthesis from non-canonical translation of "untranslated" regions and non-AUG start codons and sensitizes tumor cells for T cell targeting. Our findings raise the possibility of modulating immunosurveillance by pharmaceutical targeting ribosomes.

Standardised virtual fracture clinic management of Achilles tendon ruptures is safe and reproducible.

BACKGROUND: Traditional fracture clinics are some of the busiest clinics in a hospital, often with significant patient waiting times and delays. The use of virtual fracture clinic (VFC) for the management of certain injuries to reduce the workload on the traditional fracture clinic, in addition to reducing costs is growing in popularity. The tendoachilles is the most frequently ruptured tendon in the body but despite this, management remains a keenly debated topic. METHODS: All adult patients referred to the VFC with an actual or suspected Achilles tendon rupture were identified between January 2015 to October 2017. RESULTS: This study found that patient with and acute achilles tendon ruptures managed according to a standardised VFC protocol had a re-rupture rate of 3.82%. CONCLUSIONS: One of the advantages of a VFC model that is standardised, initiated in the ED, is that it has no variation in outcome seen in our patient group.

Giant tortoise genomes provide insights into longevity and age-related disease.

Giant tortoises are among the longest-lived vertebrate animals and, as such, provide an excellent model to study traits like longevity and age-related diseases. However, genomic and molecular evolutionary information on giant tortoises is scarce. Here, we describe a global analysis of the genomes of Lonesome George-the iconic last member of Chelonoidis abingdonii-and the Aldabra giant tortoise (Aldabrachelys gigantea). Comparison of these genomes with those of related species, using both unsupervised and supervised analyses, led us to detect lineage-specific variants affecting DNA repair genes, inflammatory mediators and genes related to cancer development. Our study also hints at specific evolutionary strategies linked to increased lifespan, and expands our understanding of the genomic determinants of ageing. These new genome sequences also provide important resources to help the efforts for restoration of giant tortoise populations.

Varied Role of Ubiquitylation in Generating MHC Class I Peptide Ligands.

CD8+ T cell immunosurveillance is based on recognizing oligopeptides presented by MHC class I molecules. Despite decades of study, the importance of protein ubiquitylation to peptide generation remains uncertain. In this study, we examined the ability of MLN7243, a recently described ubiquitin-activating enzyme E1 inhibitor, to block overall cytosolic peptide generation and generation of specific peptides from vaccinia- and influenza A virus-encoded proteins. We show that MLN7243 rapidly inhibits ubiquitylation in a variety of cell lines and can profoundly reduce the generation of cytosolic peptides. Kinetic analysis of specific peptide generation reveals that ubiquitylation of defective ribosomal products is rate limiting in generating class I peptide complexes. More generally, our findings demonstrate that the requirement for ubiquitylation in MHC class I-restricted Ag processing varies with class I allomorph, cell type, source protein, and peptide context. Thus, ubiquitin-dependent and -independent pathways robustly contribute to MHC class I-based immunosurveillance.

Virtual fracture clinic management of fifth metatarsal, including Jones', fractures is safe and cost-effective.

Virtual clinics have been shown to be safe and cost-effective in many specialties, yet barriers exist to their implementation in orthopaedics. The aims of this study were to look at whether the management of 5th metatarsal fractures using a virtual fracture clinic model is safe, cost effective and avoids adverse outcomes whilst being acceptable to patients using the service. All patients with a fifth metatarsal fracture between September 2013 and September 2015 had a standardised management plan initiated (blackboot, full weightbearing) in the emergency department (ED). 663 patients met inclusion criteria, 251 (37.5%) Type 1, 111 (17%) Type 2 (Jones'), 281 (42%) Type 3 or distal, 20 (3%) were misdiagnosed, and 4 (0.5%) patient's images were unavailable. 499 (75%) patients were discharged immediately, 47 (7%) had further imaging, 114 (17%) had either ESP or consultant clinic review, and 3 (<1%) transferred their care privately. The average number of clinic visits per patient was 0.17. At a conservative estimate of 1.3 visits per patient in a traditional pathway this saved 779 clinic visits with a cost saving of £60,000 on clinic visits alone. There were 8 (7%) asymptomatic non-unions in Type 2 (Jones') fractures. One patient required surgical intervention. Fifth metatarsal fractures have excellent outcomes with conservative management yet traditionally have required clinic visits to confirm the diagnosis and explain the management and prognosis. Our study supports the use of a virtual fracture clinic model that is standardised, initiated in ED, that is both safe and cost-effective.

Defining Viral Defective Ribosomal Products: Standard and Alternative Translation Initiation Events Generate a Common Peptide from Influenza A Virus M2 and M1 mRNAs.

Influenza A virus gene segment 7 encodes two proteins: the M1 protein translated from unspliced mRNA and the M2 protein produced by mRNA splicing and largely encoded by the M1 +1 reading frame. To better understand the generation of defective ribosomal products relevant to MHC class I Ag presentation, we engineered influenza A virus gene segment 7 to encode the model H-2 K(b) class I peptide ligand SIINFEKL at the M2 protein C terminus. Remarkably, after treating virus-infected cells with the RNA splicing inhibitor spliceostatin A to prevent M2 mRNA generation, K(b)-SIINFEKL complexes were still presented on the cell surface at levels ≤60% of untreated cells. Three key findings indicate that SIINFEKL is produced by cytoplasmic translation of unspliced M1 mRNA initiating at CUG codons within the +1 reading frame: 1) synonymous mutation of CUG codons in the M2-reading frame reduced K(b)-SIINFEKL generation; 2) K(b)-SIINFEKL generation was not affected by drug-mediated inhibition of AUG-initiated M1 synthesis; and 3) K(b)-SIINFEKL was generated in vitro and in vivo from mRNA synthesized in the cytoplasm by vaccinia virus, and hence cannot be spliced. These findings define a viral defective ribosomal product generated by cytoplasmic noncanonical translation and demonstrate the participation of CUG-codon-based translation initiation in pathogen immunosurveillance.

Review article: Anti-embolism stockings.

The National Institute for Health and Clinical Excellence (NICE) guidelines recommend combined mechanical and pharmacological prophylaxis to reduce the risk of venous thromboembolism (VTE) in patients undergoing orthopaedic surgery. There is increasing evidence that anti-embolic stockings (AES) have little effect on reducing such risk. Articles in the MEDLINE, EMBASE, and Cochrane Library were reviewed. Studies on the use of pharmacological prophylaxis recommended in the 2010 NICE guidelines including low-molecular-weight heparin, unfractionated heparin, rivaroxaban, and dabigatran with and without AES in patients undergoing orthopaedic surgery were included. A total of 1171 trauma and elective orthopaedic patients in 4 studies were included; 587 received pharmacological prophylaxis alone, and 584 received a combination of pharmacological prophylaxis and above- or belowknee AES. Of the respective patients, 44 (7.5%) and 31 (5.3%) developed deep vein thrombosis (p=0.1587) and 7 (1.2%) and 9 (1.5%) developed pulmonary embolism (p=0.8493). The overall VTE rates did not differ significantly (p=0.2864). No death from VTE was reported. Addition of AES did not confer significant benefit in terms of reducing the risk of VTE in orthopaedic patients.

Long-term results of a randomized controlled trial of a nonoperative strategy (watchful waiting) for men with minimally symptomatic inguinal hernias.

OBJECTIVE: To assess the long-term crossover (CO) rate in men undergoing watchful waiting (WW) as a primary treatment strategy for their asymptomatic or minimally symptomatic inguinal hernias. BACKGROUND: With an average follow-up of 3.2 years, a randomized controlled trial comparing WW with routine repair for male patients with minimally symptomatic inguinal hernias led investigators to conclude that WW was an acceptable option [JAMA. 2006;295(3):285-292]. We now analyze patients in the WW group after an additional 7 years of follow-up. METHODS: At the conclusion of the original study, 254 men who had been assigned to WW consented to longer-term follow-up. These patients were contacted yearly by mail questionnaire. Nonresponders were contacted by phone or e-mail for additional data collection. RESULTS: Eighty-one of the 254 men (31.9%) crossed over to surgical repair before the end of the original study, December 31, 2004, with a median follow-up of 3.2 (range: 2-4.5) years. The patients have now been followed for an additional 7 years with a maximum follow-up of 11.5 years. The estimated cumulative CO rates using Kaplan-Meier analysis was 68%. Men older than 65 years crossed over at a considerably higher rate than younger men (79% vs 62%). The most common reason for CO was pain (54.1%). A total of 3 patients have required an emergency operation, but there has been no mortality. CONCLUSIONS: Men who present to their physicians because of an inguinal hernia even when minimally symptomatic should be counseled that although WW is a reasonable and safe strategy, symptoms will likely progress and an operation will be needed eventually.

Endogenous viral antigen processing generates peptide-specific MHC class I cell-surface clusters.

Sensitivity is essential in CD8+ T-cell killing of virus-infected cells and tumor cells. Although the affinity of the T-cell receptor (TCR) for antigen is relatively low, the avidity of T cell-antigen-presenting cell interactions is greatly enhanced by increasing the valence of the interaction. It is known that TCRs cluster into protein islands after engaging their cognate antigen (peptides bound to MHC molecules). Here, we show that mouse K(b) class I molecules segregate into preformed, long-lasting (hours) clusters on the antigen-presenting cell surface based on their bound viral peptide. Peptide-specific K(b) clustering occurs when source antigens are expressed by vaccinia or vesicular stomatitis virus, either as proteasome-liberated precursors or free intracellular peptides. By contrast, K(b)-peptide complexes generated by incubating cells with synthetic peptides are extensively intermingled on the cell surface. Peptide-specific complex sorting is first detected in the Golgi complex, and compromised by removing the K(b) cytoplasmic tail. Peptide-specific clustering is associated with increased T-cell sensitivity: on a per-complex basis, endogenous SIINFEKL activates T cells more efficiently than synthetic SIINFEKL, and wild-type K(b) presents endogenous SIINFEKL more efficiently than tailless K(b). We propose that endogenous processing generates peptide-specific clusters of class I molecules to maximize the sensitivity and speed of T-cell immunosurveillance.

Cysteinyl-tRNA deacylation can be uncoupled from protein synthesis.

Aminoacyl-tRNA synthetases (ARSs) are critical components of protein translation, providing ribosomes with aminoacyl-tRNAs. In return, ribosomes release uncharged tRNAs as ARS substrates. Here, we show that tRNA deacylation can be uncoupled from protein synthesis in an amino acid specific manner. While tRNAs coupled to radiolabeled Met, Leu Lys, or Ser are stable in cells following translation inhibition with arsenite, radiolabeled Cys is released from tRNA at a high rate. We discuss possible translation independent functions for tRNA(Cys).

Population-based estimates of the occurrence of multiple vs first primary basal cell carcinomas in 4 European regions.

OBJECTIVE: To estimate the population-based incidence of first and multiple basal cell carcinomas (BCCs) throughout Europe. DESIGN: The registry practices of 4 population-based cancer registries that routinely register BCC incidence were evaluated for inclusion of first and subsequent histologically confirmed BCCs. Where multiple BCCs were not routinely registered, comparisons with hospital databases were made. DATA SOURCES: Cancer registry databases from Finland, Malta, the Netherlands (Eindhoven), and Scotland were inspected for registry of first and multiple BCCs in recent years. Cross-checks with hospital and pathology databases were made to check for completeness. RESULTS: Age-standardized first BCC incidence rates varied between 77 (Malta) and 158 (Eindhoven) per 100 000 person-years. Generally, rates were higher in males than in females, and incidences increased steeply with increasing age. There were approximately 30% more patients with a BCC and 40% to 100% more BCC tumors diagnosed in a given calendar year than were routinely reported for patients with a first primary BCC. The difference between the number of first primary BCCs and the total number of BCCs in a calendar year was generally slightly higher for males than for females and increased substantially with increasing age. CONCLUSION: Currently, routinely reported first BCC incidence rates of the included countries should be multiplied by a factor of 1.3 for an estimate of total number of patients diagnosed as having a BCC in a given year.

Chemokines control naive CD8+ T cell selection of optimal lymph node antigen presenting cells.

Naive antiviral CD8(+) T cells are activated in the draining LN (DLN) by dendritic cells (DCs) presenting viral antigens. However, many viruses infect LN macrophages, which participate in initiation of innate immunity and B cell activation. To better understand how and why T cells select infected DCs rather than macrophages, we performed intravital microscopy and ex vivo analyses after infecting mice with vaccinia virus (VV), a large DNA virus that infects both LN macrophages and DCs. Although CD8(+) T cells interact with both infected macrophages and DCs in the LN peripheral interfollicular region (PIR), DCs generate more frequent and stable interactions with T cells. VV infection induces rapid release of CCR5-binding chemokines in the LN, and administration of chemokine-neutralizing antibodies diminishes T cell activation by increasing T cell localization to macrophages in the macrophage-rich region (MRR) at the expense of PIR DCs. Similarly, DC ablation increases both T cell localization to the MRR and the duration of T cell-macrophage contacts, resulting in suboptimal T cell activation. Thus, virus-induced chemokines in DLNs enable antiviral CD8(+) T cells to distinguish DCs from macrophages to optimize T cell priming.

A clinician's guide to patient selection for watchful waiting management of inguinal hernia.

OBJECTIVE: The goal of this study was to assist surgeons in managing patients with minimally symptomatic inguinal hernia by identifying characteristics that predict crossover to surgery or worsening of hernia symptoms. BACKGROUND: Randomized trials have suggested that watchful waiting management of minimally symptomatic inguinal hernia is an acceptable alternative to surgical repair. However, these trials found that roughly a quarter of patients would elect for repair in the first 2 years, suggesting that not all patients are good candidates for watchful waiting. METHODS: The 336 patients randomized to watchful waiting in the American College of Surgeons Watchful Waiting Hernia Trial constituted the study population. Preoperative patient characteristics were used to predict 2 outcomes, either crossover to surgery or the development of hernia pain limiting activities and/or crossover to surgery. Patients in our study were part of a previously registered randomized trial: NCT00263250. RESULTS: At 2 years, 72 patients crossed over to surgery, with pain with strenuous activities [odds ratio (OR), 1.3 per 10-mm visual analog scale pain scale], chronic constipation (OR, 4.9), prostatism (OR, 2.9), being married (OR, 2.3), and good health [OR, 3.0 American Society of Anesthesiologists Class (ASA) 1 vs 2], predicting crossover. An additional 28 patients developed pain, limiting their activities, with pain during strenuous activities (OR, 1.3 per 10-mm visual analog scale) and chronic constipation (OR, 4.5), predicting the combined outcome of pain limiting activities and/or crossover to surgery. Higher levels of activity reduced the risk (OR, 0.95) of this combined outcome. CONCLUSIONS: Readily identifiable patient characteristics can predict those patients with minimally symptomatic inguinal hernia who are likely to "fail" watchful waiting hernia management. Consideration of these factors will allow surgeons to optimally tailor hernia management.

Compartmentalized MHC class I antigen processing enhances immunosurveillance by circumventing the law of mass action.

MHC class I molecules function to display peptides generated from cellular and pathogen gene products for immune surveillance by CD8(+) T cells. Cells typically express approximately 100,000 class I molecules, or approximately 1 per 30,000 cellular proteins. Given "one protein, one peptide" representation, immunosurveillance would be heavily biased toward the most abundant cell proteins. Cells use several mechanisms to prevent this, including the predominant use of defective ribosomal products (DRiPs) to generate peptides from nascent proteins and, as we show here, compartmentalization of DRiP peptide generation to prevent competition from abundant cytosolic peptides. This provides an explanation for the exquisite ability of T cells to recognize peptides generated from otherwise undetected gene products.

Innate immune and chemically triggered oxidative stress modifies translational fidelity.

Translational fidelity, essential for protein and cell function, requires accurate transfer RNA (tRNA) aminoacylation. Purified aminoacyl-tRNA synthetases exhibit a fidelity of one error per 10,000 to 100,000 couplings. The accuracy of tRNA aminoacylation in vivo is uncertain, however, and might be considerably lower. Here we show that in mammalian cells, approximately 1% of methionine (Met) residues used in protein synthesis are aminoacylated to non-methionyl-tRNAs. Remarkably, Met-misacylation increases up to tenfold upon exposing cells to live or non-infectious viruses, toll-like receptor ligands or chemically induced oxidative stress. Met is misacylated to specific non-methionyl-tRNA families, and these Met-misacylated tRNAs are used in translation. Met-misacylation is blocked by an inhibitor of cellular oxidases, implicating reactive oxygen species (ROS) as the misacylation trigger. Among six amino acids tested, tRNA misacylation occurs exclusively with Met. As Met residues are known to protect proteins against ROS-mediated damage, we propose that Met-misacylation functions adaptively to increase Met incorporation into proteins to protect cells against oxidative stress. In demonstrating an unexpected conditional aspect of decoding mRNA, our findings illustrate the importance of considering alternative iterations of the genetic code.