Scission-Enhanced Molecular Imaging (SEMI).

Positron emission tomography (PET) imaging methods have advanced our understanding of human biology, while targeted radiotherapeutic drug treatments are now routinely used clinically. The field is expected to grow considerably based on an expanding repertoire of available affinity ligands, radionuclides, conjugation chemistries, and their FDA approvals. With this increasing use, strategies for dose reduction have become of high interest to protect patients from unnecessary and off-target toxicity. Here, we describe a simple and powerful method, scission-enhanced molecular imaging (SEMI). The technique allows for rapid corporeal elimination of radionuclides once imaging or theranostic treatment is completed and relies on "click-to-release" bioorthogonal linkers.

Centers for Disease Control and Prevention's Public Health Infrastructure Grant: A Better Approach to Empowering More State and Local Decision Making and Strengthening the Public Health Workforce and Infrastructure.

CONTEXT: In response to the COVID-19 pandemic, Congress passed the American Rescue Plan Act of 2021 (ARPA) that included a historic investment in the public health workforce. PROGRAM: Charged with implementing this investment, the U.S. Centers for Disease Control and Prevention (CDC) launched the Public Health Infrastructure Grant (PHIG). PHIG builds on CDC's experience working with state, local, and territorial public health departments and represents a new approach to strengthening the public health workforce. IMPLEMENTATION: Specifically, PHIG incorporates features that allow these public health departments to prioritize and tailor the funding to meet their communities' needs: 1) focus on workforce as core infrastructure, 2) streamlined programmatic and administrative requirements, 3) more equitable funding approach, and 4) enhanced support from national partners and CDC. DISCUSSION: The goal is to optimize the unprecedented opportunity afforded by ARPA and lead to a stronger public health workforce and infrastructure across the United States.

Transforming Aryl-Tetrazines into Bioorthogonal Scissors for Systematic Cleavage of trans-Cyclooctenes.

Bioorthogonal bond-cleavage reactions have emerged as a powerful tool for precise spatiotemporal control of (bio)molecular function in the biological context. Among these chemistries, the tetrazine-triggered elimination of cleavable trans-cyclooctenes (click-to-release) stands out due to high reaction rates, versatility, and selectivity. Despite an increasing understanding of the underlying mechanisms, application of this reaction remains limited by the cumulative performance trade-offs (i.e., click kinetics, release kinetics, release yield) of existing tools. Efficient release has been restricted to tetrazine scaffolds with comparatively low click reactivity, while highly reactive aryl-tetrazines give only minimal release. By introducing hydroxyl groups onto phenyl- and pyridyl-tetrazine scaffolds, we have developed a new class of 'bioorthogonal scissors' with unique chemical performance. We demonstrate that hydroxyaryl-tetrazines achieve near-quantitative release upon accelerated click reaction with cleavable trans-cyclooctenes, as exemplified by click-triggered activation of a caged prodrug, intramitochondrial cleavage of a fluorogenic probe (turn-on) in live cells, and rapid intracellular bioorthogonal disassembly (turn-off) of a ligand-dye conjugate.

HLA-II-Associated HIV-1 Adaptation Decreases CD4+ T-Cell Responses in HIV-1 Vaccine Recipients.

Epitopes with evidence of HLA-II-associated adaptation induce poorly immunogenic CD4+ T-cell responses in HIV-positive (HIV+) individuals. Many such escaped CD4+ T-cell epitopes are encoded by HIV-1 vaccines being evaluated in clinical trials. Here, we assessed whether this viral adaptation adversely impacts CD4+ T-cell responses following HIV-1 vaccination, thereby representing escaped epitopes. When evaluated in separate peptide pools, vaccine-encoded adapted epitopes (AE) induced CD4+ T-cell responses less frequently than nonadapted epitopes (NAE). We also demonstrated that in a polyvalent vaccine, where both forms of the same epitope were encoded, AE were less immunogenic. NAE-specific CD4+ T cells had increased, albeit low, levels of interferon gamma (IFN-γ) cytokine production. Single-cell transcriptomic analyses showed that NAE-specific CD4+ T cells expressed interferon-related genes, while AE-specific CD4+ T cells resembled a Th2 phenotype. Importantly, the magnitude of NAE-specific CD4+ T-cell responses, but not that of AE-specific responses, was found to positively correlate with Env-specific antibodies in a vaccine efficacy trial. Together, these findings show that HLA-II-associated viral adaptation reduces CD4+ T-cell responses in HIV-1 vaccine recipients and suggest that vaccines encoding a significant number of AE may not provide optimal B-cell help for HIV-specific antibody production. IMPORTANCE Despite decades of research, an effective HIV-1 vaccine remains elusive. Vaccine strategies leading to the generation of broadly neutralizing antibodies are likely needed to provide the best opportunity of generating a protective immune response against HIV-1. Numerous studies have demonstrated that T-cell help is necessary for effective antibody generation. However, immunogen sequences from recent HIV-1 vaccine efficacy trials include CD4+ T-cell epitopes that have evidence of immune escape. Our study shows that these epitopes, termed adapted epitopes, elicit lower frequencies of CD4+ T-cell responses in recipients from multiple HIV-1 vaccine trials. Additionally, the counterparts to these epitopes, termed nonadapted epitopes, elicited CD4+ T-cell responses that correlated with Env-specific antibodies in one efficacy trial. These results suggest that vaccine-encoded adapted epitopes dampen CD4+ T-cell responses, potentially impacting both HIV-specific antibody production and efficacious vaccine efforts.

Oxidative Desymmetrization Enables the Concise Synthesis of a trans-Cyclooctene Linker for Bioorthogonal Bond Cleavage.

Modified trans-cyclooctenes (TCO) are capable of highly efficient molecular manipulations in biological environments, driven by the bioorthogonal reaction with tetrazines (Tz). The development of click-cleavable TCO has fueled the field of in vivo chemistry and enabled the design of therapeutic strategies that have already started to enter the clinic. A key element for most of these approaches is the implementation of a cleavable TCO linker. So far, only one member of this class has been developed, a compound that requires a high synthetic effort, mainly to fulfill the multilayered demands on its chemical structure. To tackle this limitation, we developed a dioxolane-fused cleavable TCO linker (dcTCO) that can be prepared in only five steps by applying an oxidative desymmetrization to achieve diastereoselective introduction of the required functionalities. Based on investigation of the structure, reaction kinetics, stability, and hydrophilicity of dcTCO, we demonstrate its bioorthogonal application in the design of a caged prodrug that can be activated by in-situ Tz-triggered cleavage to achieve a remarkable >1000-fold increase in cytotoxicity.

HLA tapasin independence: broader peptide repertoire and HIV control.

Human leukocyte antigen (HLA) class I allotypes vary in their ability to present peptides in the absence of tapasin, an essential component of the peptide loading complex. We quantified tapasin dependence of all allotypes that are common in European and African Americans (n = 97), which revealed a broad continuum of values. Ex vivo examination of cytotoxic T cell responses to the entire HIV-1 proteome from infected subjects indicates that tapasin-dependent allotypes present a more limited set of distinct peptides than do tapasin-independent allotypes, data supported by computational predictions. This suggests that variation in tapasin dependence may impact the strength of the immune responses by altering peptide repertoire size. In support of this model, we observed that individuals carrying HLA class I genotypes characterized by greater tapasin independence progress more slowly to AIDS and maintain lower viral loads, presumably due to increased breadth of peptide presentation. Thus, tapasin dependence level, like HLA zygosity, may serve as a means to restrict or expand breadth of the HLA-I peptide repertoire across humans, ultimately influencing immune responses to pathogens and vaccines.

Tetrazine-Triggered Bioorthogonal Cleavage of trans-Cyclooctene-Caged Phenols Using a Minimal Self-Immolative Linker Strategy.

Bond-cleavage reactions triggered by bioorthogonal tetrazine ligation have emerged as strategies to chemically control the function of (bio)molecules and achieve activation of prodrugs in living systems. While most of these approaches make use of caged amines, current methods for the release of phenols are limited by unfavorable reaction kinetics or insufficient stability of the Tz-responsive reactants. To address this issue, we have implemented a self-immolative linker that enables the connection of cleavable trans-cyclooctenes (TCO) and phenols via carbamate linkages. Based on detailed investigation of the reaction mechanism with several Tz, revealing up to 96 % elimination after 2 hours, we have developed a TCO-caged prodrug with 750-fold reduced cytotoxicity compared to the parent drug and achieved in situ activation upon Tz/TCO click-to-release.

Elevated HIV Infection of CD4 T Cells in MRKAd5 Vaccine Recipients Due to CD8 T Cells Targeting Adapted Epitopes.

HIV frequently escapes CD8 T cell responses, leading to the accumulation of viral adaptations. We recently demonstrated that during chronic HIV infection, adapted epitopes can promote maturation of dendritic cells (DCs) through direct CD8 T cell interactions and lead to enhanced HIV trans-infection of CD4 T cells. Here, we sought to determine the role of such adaptations following HIV MRKAd5 vaccination. We observed that vaccine-induced adapted epitope-specific CD8 T cells promoted higher levels of DC maturation than nonadapted ones and that these matured DCs significantly enhanced HIV trans-infection. These matured DCs were associated with higher levels of interleukin 5 (IL-5) and IL-13 and a lower level of CXCL5, which have been shown to impact DC maturation, as well as a lower level of CXCL16. Finally, we observed that vaccine recipients with high HLA-I-associated adaptation became HIV infected more quickly. Our results offer another possible mechanism for enhanced infection among MRKAd5 vaccinees. IMPORTANCE Despite the well-established contribution of CD8 T cells in HIV control, prior CD8 T cell-based HIV vaccines have failed to demonstrate any efficacy in preventing viral infection. One such vaccine, known as the MRKAd5 vaccine, showed a potential increased risk of viral infection among vaccine recipients. However, the underlying mechanism(s) remains unclear. In this study, we observed that vaccine recipients with high adaptation to their HLA-I alleles were associated with an increased HIV infection risk in comparison to the others. Similar to what we observed in HIV infection in the prior study, adapted epitope-specific CD8 T cells obtained from vaccine recipients exhibit a greater capacity in facilitating viral infection by promoting dendritic cell maturation. Our findings provide a possible explanation for the enhanced viral acquisition risk among MRKAd5 vaccine recipients and highlight the importance of optimizing vaccine design with consideration of HLA-I-associated HIV adaptation.

COVID-19 and coagulation: bleeding and thrombotic manifestations of SARS-CoV-2 infection.

Patients with coronavirus disease 2019 (COVID-19) have elevated D-dimer levels. Early reports describe high venous thromboembolism (VTE) and disseminated intravascular coagulation (DIC) rates, but data are limited. This multicenter retrospective study describes the rate and severity of hemostatic and thrombotic complications of 400 hospital-admitted COVID-19 patients (144 critically ill) primarily receiving standard-dose prophylactic anticoagulation. Coagulation and inflammatory parameters were compared between patients with and without coagulation-associated complications. Multivariable logistic models examined the utility of these markers in predicting coagulation-associated complications, critical illness, and death. The radiographically confirmed VTE rate was 4.8% (95% confidence interval [CI], 2.9-7.3), and the overall thrombotic complication rate was 9.5% (95% CI, 6.8-12.8). The overall and major bleeding rates were 4.8% (95% CI, 2.9-7.3) and 2.3% (95% CI, 1.0-4.2), respectively. In the critically ill, radiographically confirmed VTE and major bleeding rates were 7.6% (95% CI, 3.9-13.3) and 5.6% (95% CI, 2.4-10.7), respectively. Elevated D-dimer at initial presentation was predictive of coagulation-associated complications during hospitalization (D-dimer >2500 ng/mL, adjusted odds ratio [OR] for thrombosis, 6.79 [95% CI, 2.39-19.30]; adjusted OR for bleeding, 3.56 [95% CI, 1.01-12.66]), critical illness, and death. Additional markers at initial presentation predictive of thrombosis during hospitalization included platelet count >450 × 109/L (adjusted OR, 3.56 [95% CI, 1.27-9.97]), C-reactive protein (CRP) >100 mg/L (adjusted OR, 2.71 [95% CI, 1.26-5.86]), and erythrocyte sedimentation rate (ESR) >40 mm/h (adjusted OR, 2.64 [95% CI, 1.07-6.51]). ESR, CRP, fibrinogen, ferritin, and procalcitonin were higher in patients with thrombotic complications than in those without. DIC, clinically relevant thrombocytopenia, and reduced fibrinogen were rare and were associated with significant bleeding manifestations. Given the observed bleeding rates, randomized trials are needed to determine any potential benefit of intensified anticoagulant prophylaxis in COVID-19 patients.

Atypical Mutation in Neisseria gonorrhoeae 23S rRNA Associated with High-Level Azithromycin Resistance.

A2059G mutation in the 23S rRNA gene is the only reported mechanism conferring high-level azithromycin resistance (HL-AZMR) in Neisseria gonorrhoeae Through U.S. gonococcal antimicrobial resistance surveillance projects, we identified four HL-AZMR gonococcal isolates lacking this mutational genotype. Genetic analysis revealed an A2058G mutation of 23S rRNA alleles in all four isolates. In vitro selected gonococcal strains with homozygous A2058G recapitulated the HL-AZMR phenotype. Taken together, we postulate that the A2058G mutation confers HL-AZMR in N. gonorrhoeae.

CD8 T cells targeting adapted epitopes in chronic HIV infection promote dendritic cell maturation and CD4 T cell trans-infection.

HIV-1 frequently escapes from CD8 T cell responses via HLA-I restricted adaptation, leading to the accumulation of adapted epitopes (AE). We previously demonstrated that AE compromise CD8 T cell responses during acute infection and are associated with poor clinical outcomes. Here, we examined the impact of AE on CD8 T cell responses and their biological relevance in chronic HIV infection (CHI). In contrast to acute infection, the majority of AE are immunogenic in CHI. Longitudinal analyses from acute to CHI showed an increased frequency and magnitude of AE-specific IFNγ responses compared to NAE-specific ones. These AE-specific CD8 T cells also were more cytotoxic to CD4 T cells. In addition, AE-specific CD8 T cells expressed lower levels of PD1 and CD57, as well as higher levels of CD28, suggesting a more activated and less exhausted phenotype. During CHI, viral sequencing identified AE-encoding strains as the dominant quasispecies. Despite increased CD4 T cell cytotoxicity, CD8 T cells responding to AE promoted dendritic cell (DC) maturation and CD4 T cell trans-infection perhaps explaining why AE are predominant in CHI. Taken together, our data suggests that the emergence of AE-specific CD8 T cell responses in CHI confers a selective advantage to the virus by promoting DC-mediated CD4 T cell trans-infection.

Implementation and Evaluation of Gradient Strip Antimicrobial Susceptibility Testing in US Public Health Laboratories to Respond to Resistant Gonorrhea.

BACKGROUND: Gradient strip antimicrobial susceptibility testing using Etest is conducted by local public health jurisdictions participating in the Strengthening the US Response to Resistant Gonorrhea (SURRG) program to inform public health responses to resistant gonorrhea. Proficiency testing results across the participating laboratories were analyzed and a comparison of Etest with the agar dilution method was conducted. METHODS: Laboratories participating in SURRG performed Etest for azithromycin (AZM), cefixime (CFX), and ceftriaxone (CRO). Concurrence between minimum inhibitory concentrations (MICs) obtained with Etest versus the agar dilution method using corresponding isolates was defined as ±1 double dilution. Specific levels of reduced susceptibility were termed "alerts" and included isolates with the following MICs: ≥2.0 µg/mL (AZM), ≥0.25 µg/mL (CFX), and ≥0.125 µg/mL (CRO). Categorical (alert/nonalert) agreement was calculated for MICs determined using Etest and agar dilution methods. RESULTS: Strengthening the US Response to Resistant Gonorrhea laboratories had high proficiency testing scores (≥98%) and low levels of interlaboratory variations in MICs. The overall concurrence of MICs (essential agreement) determined using agar dilution, and Etest was 96% (CRO), 96% (CFX), and 95% (AZM). Depending on the antibiotic tested, between 27% and 66% of isolates with alert MICs determined by Etest also had alert MICs using the reference agar dilution methodology; however, most of these alert MICs were detected at threshold levels. CONCLUSIONS: This study demonstrates that MICs produced by SURRG laboratories using Etest have a high level of concurrence with agar dilution. Although confirmation of specific alert MICs varied, Etest facilities rapid detection and response to emerging resistant gonorrhea.

Twelve-Month results from multicenter, open-label, randomized controlled clinical trial comparing differential target multiplexed spinal cord stimulation and traditional spinal cord stimulation in subjects with chronic intractable back pain and leg pain.

BACKGROUND: Spinal cord stimulation (SCS) is a well-established treatment for chronic intractable pain of the trunk and/or limbs; however, low back pain (LBP) is difficult to treat using traditional SCS. Differential Target Multiplexed spinal cord stimulation (DTM SCS) is an advanced approach inspired from animal studies demonstrating improved pain-related behavior and pain-relevant biological processes. OBJECTIVE: The purpose of this study was to compare the effectiveness of DTM SCS and traditional SCS in treating chronic LBP and leg pain (LP). METHODS: This prospective, postmarket randomized controlled trial compared DTM SCS to traditional SCS in patients with chronic LBP and LP. Primary end point was LBP responder rate (percentage of subjects with ≥ 50% relief) at 3 months. Noninferiority and superiority were assessed. Other outcomes included mean change in back and leg pain, responder rates, disability, global health, satisfaction, and safety profile throughout the 12-month follow-up. RESULTS: One hundred twenty-eight subjects were randomized across 12 centers (67 DTM SCS and 61 traditional SCS). Of the 94 patients implanted, 46 subjects in each group completed the 3-month assessment. LBP responder rate of 80.1% with DTM SCS was superior to 51.2% with traditional SCS (p = 0.0010). Mean LBP reduction (5.36 cm) with DTM SCS was greater than reduction (3.37 cm) with traditional SCS (p < 0.0001). These results were sustained at 6 months and 12 months. Safety profiles were similar between treatment groups. CONCLUSION: Superiority of DTM SCS compared with traditional SCS for chronic LBP was demonstrated. Clinical improvements provided by DTM SCS were sustained over 12 months and are expected to significantly impact the management of chronic LBP.

A Cleavable C2-Symmetric trans-Cyclooctene Enables Fast and Complete Bioorthogonal Disassembly of Molecular Probes.

Bioorthogonal chemistry is bridging the divide between static chemical connectivity and the dynamic physiologic regulation of molecular state, enabling in situ transformations that drive multiple technologies. In spite of maturing mechanistic understanding and new bioorthogonal bond-cleavage reactions, the broader goal of molecular ON/OFF control has been limited by the inability of existing systems to achieve both fast (i.e., seconds to minutes, not hours) and complete (i.e., >99%) cleavage. To attain the stringent performance characteristics needed for high fidelity molecular inactivation, we have designed and synthesized a new C2-symmetric trans-cyclooctene linker (C2TCO) that exhibits excellent biological stability and can be rapidly and completely cleaved with functionalized alkyl-, aryl-, and H-tetrazines, irrespective of click orientation. By incorporation of C2TCO into fluorescent molecular probes, we demonstrate highly efficient extracellular and intracellular bioorthogonal disassembly via omnidirectional tetrazine-triggered cleavage.

Genotypic and Mechanistic Characterization of Subtype-Specific HIV Adaptation to Host Cellular Immunity.

The extent to which viral genetic context influences HIV adaptation to human leukocyte antigen (HLA) class I-restricted immune pressures remains incompletely understood. The Ugandan HIV epidemic, where major pandemic group M subtypes A1 and D cocirculate in a single host population, provides an opportunity to investigate this question. We characterized plasma HIV RNA gag, pol, and nef sequences, along with host HLA genotypes, in 464 antiretroviral-naive individuals chronically infected with HIV subtype A1 or D. Using phylogenetically informed statistical approaches, we identified HLA-associated polymorphisms and formally compared their strengths of selection between viral subtypes. A substantial number (32%) of HLA-associated polymorphisms identified in subtype A1 and/or D had previously been reported in subtype B, C, and/or circulating recombinant form 01_AE (CRF01_AE), confirming the shared nature of many HLA-driven escape pathways regardless of viral genetic context. Nevertheless, 34% of the identified HLA-associated polymorphisms were significantly differentially selected between subtypes A1 and D. Experimental investigation of select examples of subtype-specific escape revealed distinct underlying mechanisms with important implications for vaccine design: whereas some were attributable to subtype-specific sequence variation that influenced epitope-HLA binding, others were attributable to differential mutational barriers to immune escape. Overall, our results confirm that HIV genetic context is a key modulator of viral adaptation to host cellular immunity and highlight the power of combined bioinformatic and mechanistic studies, paired with knowledge of epitope immunogenicity, to identify appropriate viral regions for inclusion in subtype-specific and universal HIV vaccine strategies.IMPORTANCE The identification of HIV polymorphisms reproducibly selected under pressure by specific HLA alleles and the elucidation of their impact on viral function can help identify immunogenic viral regions where immune escape incurs a fitness cost. However, our knowledge of HLA-driven escape pathways and their functional costs is largely limited to HIV subtype B and, to a lesser extent, subtype C. Our study represents the first characterization of HLA-driven adaptation pathways in HIV subtypes A1 and D, which dominate in East Africa, and the first statistically rigorous characterization of differential HLA-driven escape across viral subtypes. The results support a considerable impact of viral genetic context on HIV adaptation to host HLA, where HIV subtype-specific sequence variation influences both epitope-HLA binding and the fitness costs of escape. Integrated bioinformatic and mechanistic characterization of these and other instances of differential escape could aid rational cytotoxic T-lymphocyte-based vaccine immunogen selection for both subtype-specific and universal HIV vaccines.

Expanding the Scope of Antibody Rebridging with New Pyridazinedione-TCO Constructs.

Disulfide rebridging methods have recently emerged as a route to hinge region-specific antibody modification, and there exist numerous examples of successful rebridging chemistry applied to clinically relevant human IgG1 antibodies. Here, dibromopyridazinedione disulfide rebridging is adapted to fast trans-cyclooctene/tetrazine (TCO/Tz) bioorthogonal ligations and extended beyond therapeutic human IgG1 antibodies for the first time to include mouse and rat monoclonal antibodies integral to multiplexed analytical diagnostics. In spite of a common architecture, only a subset of antibody host species and IgG isotype subclasses can be rebridged, highlighting the intricate relationship between hinge region sequence, structure, biological activity, and the conjugation chemistry of IgG antibodies.

A Systematic Literature Review of Dorsal Root Ganglion Neurostimulation for the Treatment of Pain.

OBJECTIVE: To conduct a systematic literature review of dorsal root ganglion (DRG) stimulation for pain. DESIGN: Grade the evidence for DRG stimulation. METHODS: An international, interdisciplinary work group conducted a literature search for DRG stimulation. Abstracts were reviewed to select studies for grading. General inclusion criteria were prospective trials (randomized controlled trials and observational studies) that were not part of a larger or previously reported group. Excluded studies were retrospective, too small, or existed only as abstracts. Studies were graded using the modified Interventional Pain Management Techniques-Quality Appraisal of Reliability and Risk of Bias Assessment, the Cochrane Collaborations Risk of Bias assessment, and the US Preventative Services Task Force level-of-evidence criteria. RESULTS: DRG stimulation has Level II evidence (moderate) based upon one high-quality pivotal randomized controlled trial and two lower-quality studies. CONCLUSIONS: Moderate-level evidence supports DRG stimulation for treating chronic focal neuropathic pain and complex regional pain syndrome.

A Systematic Literature Review of Spine Neurostimulation Therapies for the Treatment of Pain.

OBJECTIVE: To conduct a systematic literature review of spinal cord stimulation (SCS) for pain. DESIGN: Grade the evidence for SCS. METHODS: An international, interdisciplinary work group conducted literature searches, reviewed abstracts, and selected studies for grading. Inclusion/exclusion criteria included randomized controlled trials (RCTs) of patients with intractable pain of greater than one year's duration. Full studies were graded by two independent reviewers. Excluded studies were retrospective, had small numbers of subjects, or existed only as abstracts. Studies were graded using the modified Interventional Pain Management Techniques-Quality Appraisal of Reliability and Risk of Bias Assessment, the Cochrane Collaborations Risk of Bias assessment, and the US Preventative Services Task Force level-of-evidence criteria. RESULTS: SCS has Level 1 evidence (strong) for axial back/lumbar radiculopathy or neuralgia (five high-quality RCTs) and complex regional pain syndrome (one high-quality RCT). CONCLUSIONS: High-level evidence supports SCS for treating chronic pain and complex regional pain syndrome. For patients with failed back surgery syndrome, SCS was more effective than reoperation or medical management. New stimulation waveforms and frequencies may provide a greater likelihood of pain relief compared with conventional SCS for patients with axial back pain, with or without radicular pain.