Longitudinal Lower Airway Microbial Signatures of Acute Cellular Rejection in Lung Transplantation.

Rationale: Acute cellular rejection (ACR) after lung transplantation is a leading risk factor for chronic lung allograft dysfunction. Prior studies have demonstrated dynamic microbial changes occurring within the allograft and gut that influence local adaptive and innate immune responses. However, the lung microbiome's overall impact on ACR risk remains poorly understood. Objective: To evaluate whether temporal changes in microbial signatures were associated with the development of ACR. Methods: We performed cross-sectional and longitudinal analyses (joint modeling of longitudinal and time-to-event data and trajectory comparisons) of 16S rRNA gene sequencing results derived from lung transplant recipient lower airway samples collected at multiple timepoints. Measurements and Main Results: Among 103 lung transplant recipients, 25 (24.3%) developed ACR. In comparing samples acquired one month after transplant, subjects who never developed ACR demonstrated lower airway enrichment with several oral commensals (e.g., Prevotella and Veillonella spp.) compared to those with current or future (beyond one month) ACR. However, a subgroup analysis of those who developed ACR beyond one month revealed delayed enrichment with oral commensals occurring at the time of ACR diagnosis compared to baseline, when enrichment with more traditionally pathogenic taxa was present. In longitudinal models, dynamic changes in alpha diversity (characterized by an initial decrease and a subsequent increase) and in the taxonomic trajectories of numerous oral commensals were more commonly observed in subjects with ACR. Conclusion: Dynamic changes in the lower airway microbiota are associated with the development of ACR, supporting its potential role as a useful biomarker or in ACR pathogenesis.

One-year immunologic outcomes of lung transplantation utilizing hepatitis C-viremic donors.

Little is known about the effects of hepatitis C viremia on immunologic outcomes in the era of direct-acting antivirals. We conducted a prospective, single-arm trial of lung transplantation from hepatitis C-infected donors into hepatitis C-naïve recipients (n = 21). Recipients were initiated on glecaprevir-pibrentasvir immediately post-transplant and were continued on therapy for a total of 8 weeks. A control group of recipients of hepatitis C-negative lungs were matched 1:1 on baseline variables (n = 21). The primary outcome was the frequency of acute cellular rejection over 1-year post-transplant. Treatment with glecaprevir-pibrentasvir was well tolerated and resulted in viremia clearance after a median of 16 days of therapy (IQR 10-24 days). At one year, there was no difference in incidence of acute cellular rejection (71.4% vs. 85.7%, P = .17) or rejection requiring treatment (33.3% vs. 57.1%, P = .12). Mean cumulative acute rejection scores were similar between groups (.46 [SD ± .53] vs. .52 [SD ± .37], P = .67). Receipt of HCV+ organs was not associated with acute rejection on unadjusted Cox regression analysis (HR .55, 95% CI .28-1.11, P = .09), or when adjusted for risk factors known to be associated with acute rejection (HR .57, 95% CI .27-1.21, P = .14). Utilization of hepatitis C infected lungs with immediate treatment leads to equivalent immunologic outcomes at 1 year.

A novel protocol to reduce bleeding associated with alteplase treatment of HVAD pump thrombosis.

Pump thrombosis remains a feared complication for patients implanted with durable left ventricular assist devices. Optimal treatment is unknown, but consists of either pharmacologic fibrinolysis or surgical pump exchange. Fibrinolysis is less invasive, but carries a significant risk of intracerebral hemorrhage. We present four cases of LVAD pump thrombosis successfully treated with a novel protocol that consists of low-dose four-factor prothrombin complex concentrate to reverse baseline INR elevation prior to alteplase administration to minimize the risk for intracerebral hemorrhage.

A Comparison of Prothrombin Complex Concentrate and Recombinant Activated Factor VII for the Management of Bleeding With Cardiac Surgery.

Bleeding following cardiac surgery that warrants transfusion of blood products is associated with significant complications, including increased mortality at 1 year following surgery. Factor concentrates, such as prothrombin complex concentrate (PCC), or recombinant activated factor VII (rFVIIa) have been used off-label for bleeding in cardiac surgery that is refractory to conventional therapy. The objective of this retrospective study is to assess the hemostatic effectiveness of 4-factor PCC or rFVIIa for bleeding after a broad range of cardiac surgeries. Patients were included if they were at least 18 years of age and had undergone cardiac surgery with bleeding requiring intervention with 4-factor PCC or rFVIIa. There were no differences observed in the number of packed red blood cells (4-factor PCC: 2 units vs. rFVIIa: 2 units), fresh frozen plasma (0 units vs. 1 unit) or platelet (2 units vs. 2 units) transfusions following the administration of 4-factor PCC or rFVIIa. The patients in the rFVIIa group, required more cryoprecipitate than those in the 4-factor PCC group (4-factor PCC: 2 units (range 0-6) vs. rFVIIa: 2 units (range 0-8), p = 0.03). There were no differences in secondary outcomes of chest tube output at 2, 6, 12 and 24 hours, nor was there a difference in reexploration rates or the median length of stay in the intensive care unit. Thromboembolic complications at 30 days were similar between the two groups (4-factor PCC: 13% vs. rFVIIa 26%, p = 0.08). The total median dose requirement for 4-factor PCC was 1000 units (15 units/kg) and 2 mg (20 mcg/kg) for rFVIIa. The results demonstrate feasibility of utilizing the minimum amount of drug in order to achieve a desired effect. Both 4-factor PCC and rFVIIa appear to be safe and effective options for the management of bleeding associated with cardiac surgery.

Multimodal opioid-sparing pain management after lung transplantation and the impact of liposomal bupivacaine intercostal nerve block.

Opioid analgesics are commonly used post-lung transplant, but have many side effects and are associated with worse outcomes. We conducted a retrospective review of all lung transplant recipients who were treated with a multimodal opioid-sparing pain protocol. The use of liposomal bupivacaine intercostal nerve block was variable due to hospital restrictions. The primary objective was to describe opioid requirements and patient-reported pain scores early post-lung transplant and to assess the impact of intraoperative liposomal bupivacaine intercostal nerve block. We treated 64 lung transplant recipients with our protocol. Opioid utilization decreased to a mean of 43 milligram oral morphine equivalents by postoperative day 4. Median pain scores peaked at 4 on postoperative day 1 and decreased thereafter. Only three patients were discharged home with opioids, all of whom were taking opioid agonist therapy pre-transplant for opioid use disorder. Patients who received liposomal bupivacaine intercostal nerve block in the operating room had a significant reduction in opioid consumption over postoperative day 1 through 4 (228 mg vs. 517 mg, P= .032). A multimodal opioid-sparing pain management protocol is feasible and resulted in weaning of opioids prior to hospital discharge.

Clinical and Financial Implications of 2 Treatment Strategies for Donor-derived Hepatitis C Infections.

Transplanting hepatitis C viremic donor organs into hepatitis C virus (HCV)-negative recipients is becoming increasingly common; however, practices for posttransplant direct-acting antiviral (DAA) treatment vary widely. Protracted insurance authorization processes for DAA therapy often lead to treatment delays. METHODS: At our institution, 2 strategies for providing DAA therapy to HCV- recipients of HCV+ transplants have been used. For thoracic organ recipients, an institution-subsidized course of initial therapy was provided to ensure an early treatment initiation date. For abdominal organ recipients, insurance approval for DAA coverage was sought once viremia developed, and treatment was initiated only once the insurance-authorized supply of drug was received. To evaluate the clinical impact of these 2 strategies, we retrospectively collected data pertaining to the timing of DAA initiation, duration of recipient viremia, and monetary costs incurred by patients and the institution for patients managed under these 2 DAA coverage strategies. RESULTS: One hundred fifty-two transplants were performed using HCV viremic donor organs. Eighty-nine patients received DAA treatment without subsidy, and 62 received DAA treatment with subsidy. One patient who never developed viremia posttransplant received no treatment. Subsidizing the initial course enabled earlier treatment initiation (median, 4 d [interquartile range (IQR), 2-7] vs 10 [IQR, 8-13]; P < 0.001) and shorter duration of viremia (median, 16 d [IQR, 12-29] vs 36 [IQR, 30-47]; P < 0.001). Institutional costs averaged $9173 per subsidized patient and $168 per nonsubsidized patient. Three needlestick exposures occurred in caregivers of viremic patients. CONCLUSIONS: Recipients and their caregivers stand to benefit from earlier DAA treatment initiation; however, institutional costs to subsidize DAA therapy before insurance authorization are substantial. Insurance authorization processes for DAAs should be revised to accommodate this unique patient group.

Impact of CytoSorb Hemoadsorption on Sedation Requirements in Patients With Severe COVID-19 on Venovenous Extracorporeal Membrane Oxygenation.

Hemoadsorption with CytoSorb has been used as an adjunct in the treatment of severe coronavirus disease 2019 (COVID-19)-related respiratory failure. It remains unknown if CytoSorb hemoadsorption will alter sedative and analgesic dosing in critically ill patients on venovenous extracorporeal membrane oxygenation (VV-ECMO). We conducted a retrospective review of patients with severe COVID-19 requiring VV-ECMO for respiratory support. Patients who were enrolled in a clinical study of CytoSorb were compared with patients on VV-ECMO alone. Data were collected for the 72-hour CytoSorb therapy and an additional 72 hours post-CytoSorb, or a corresponding control time period. Sedative and analgesic doses were totaled for each day and converted to midazolam or fentanyl equivalents, respectively. The primary endpoint, change in sedative and analgesic requirements over time, were compared using a two-way mixed analysis of variance. Of the 30 patients cannulated for VV-ECMO for COVID-19, 4 were excluded, leaving 8 patients in the CytoSorb arm and 18 in the Control. There was no effect of CytoSorb therapy on midazolam equivalents over the 72-hour therapy (p = 0.71) or the 72 hours post-CytoSorb (p = 0.11). In contrast, there was a significant effect of CytoSorb therapy on fentanyl equivalents over the first 72 hours (p = 0.01), but this was not consistent over the 72-hours post-CytoSorb (p = 0.23). CytoSorb therapy led to significant increases in analgesic requirements without impacting sedative requirements. Further research is needed to define the relevance of CytoSorb hemoadsorption on critical care pharmacotherapy.

Comparison of Outcomes of Enoxaparin Bridge Therapy in HeartMate II versus HeartWare HVAD Recipients.

BACKGROUND: There is a lack of robust data evaluating outcomes of enoxaparin "bridge" therapy in left ventricular assist device (LVAD) patients. METHODS: We performed a retrospective study of HeartMate II (HM II) and HeartWare HVAD recipients that received therapeutic enoxaparin as "bridge" therapy to describe bleeding and thrombotic events and compare outcomes between devices. The primary endpoint was the incidence of bleeding within 30 days of "bridge" episode. Major bleeding was defined by INTERMACS criteria. RESULTS: We evaluated 257 "bridge" episodes in 54 patients, 35 with a HM II device and 19 with an HVAD device that underwent 176 and 81 bridging episodes, respectively. The median INR prior to "bridge" was lower in the HM II group compared to the HVAD group (1.5 vs 1.7, P < .01), however, there was no difference in the median duration of "bridge" therapy (7 vs 7 days, P = .42). There were a total of 30 (12%) bleeding episodes, with the majority in the HM II group vs HVAD (26 [15%] vs 4 [5%], P = .02). We observed 3 (1%) thromboembolic events in 2 (4%) patients with an HVAD device. On multivariate analysis, the presence of a HM II device was associated with a 4-fold increased risk of bleeding. CONCLUSION: We found the use of enoxaparin "bridge" therapy to be associated with a higher incidence of bleeding in patients with a HM II device compared with an HVAD device. Assessment of device- and patient-specific factors should be evaluated to minimize bleeding events.

Clinical Use of Cangrelor After Percutaneous Coronary Intervention in Patients Requiring Mechanical Circulatory Support.

BACKGROUND: Patients with cardiogenic shock after percutaneous coronary intervention (PCI) may require mechanical circulatory support (MCS). The combination of dual antiplatelet therapy with cangrelor and continuous anticoagulation required for MCS may increase the risk of bleeding. OBJECTIVE: The objective of the study is to describe the complications and outcomes of patients who received cangrelor during MCS following PCI. METHODS: This is a single-center, retrospective, observational case series of 17 patients who received cangrelor while on MCS from June 2017 to September 2019. RESULTS: In a case series of 17 patients, 8 patients (47%) were supported with an Impella device and 4 patients (24%) with venoarterial (VA) extracorporeal membrane oxygenation (ECMO); 5 required (29%) concomitant VA ECMO and Impella support in the setting of cardiogenic shock. All patients received triple antithrombotic therapy with aspirin, heparin, and cangrelor. Cangrelor was commonly initiated at a median dose of 0.75 (range 0.5-4) µg/kg/min. Cangrelor dose adjustments included changes in increments up to 0.25 µg/kg/min with review of P2Y12 levels. A total of 10 patients (59%) experienced a bleeding event, most commonly located at the peripheral cannulation site (40%) and in the gastrointestinal tract (30%). Seven (70%) and 3 (30%) of the bleeding complications were classified as major and minor, respectively. No patient developed in-stent thrombosis during the hospitalization; 14 (82%) patients survived their MCS course. CONCLUSION AND RELEVANCE: This case series suggests that cangrelor doses less than 0.75 µg/kg/min may be beneficial. Larger studies should evaluate alternative dosing regimens.

A Propensity-Matched Cohort Study of Tocilizumab in Patients With Coronavirus Disease 2019.

To determine the impact of tocilizumab, a monoclonal antibody against the interleukin 6 receptor, on survival in patients with coronavirus disease 2019. DESIGN: Observational cohort study of patients hospitalized with coronavirus disease 2019 between March 1, 2020, and April 24, 2020. A propensity-matched (1:1) analysis was used to compare patients who received tocilizumab to controls who did not. Competing risk survival analysis was used to determine the primary outcome of time to mortality, and adjusted log-linear and logistic regression for secondary outcomes. SETTING: Three hospitals within the NYU Langone Health system in New York. PATIENTS: Consecutive adult patients hospitalized with coronavirus disease 2019. INTERVENTION: Tocilizumab 400-mg IV once in addition to standard of care or standard of care alone. MEASUREMENTS AND MAIN RESULTS: Data from 3,580 severe acute respiratory syndrome coronavirus 2 positive qualifying hospitalized patients were included, of whom 497 (13.9%) were treated with tocilizumab. In the analysis of tocilizumab-treated patients and matched controls, fewer tocilizumab-treated patients died (145/497, 29.2%) than did controls (211/497, 42.4%). In the adjusted competing risk regression model, tocilizumab therapy was associated with improved survival relative to controls (hazard ratio = 0.24, 95% CI = 0.18-0.33, p < 0.001). Tocilizumab-treated patients and controls had similar adjusted time to discharge from hospital (hazard ratio = 0.96, 95% CI = 0.78-1.17, p = 0.67). However, they had longer adjusted ICU length of stay (rate ratio = 3.1, 95% CI = 2.5-3.7, p < 0.001) and a higher adjusted infection rate (odds ratio = 4.18, 95% CI = 2.72-6.52, p < 0.001) than controls. CONCLUSIONS: Tocilizumab therapy was associated with significantly improved survival in coronavirus disease 2019 patients. This survival benefit was associated with increased ICU length of stay and increased infection rate, even as more patients in the tocilizumab group were rescued from rapid death. A prospective, randomized, placebo-controlled trial is needed to confirm these findings.

Management and tolerability of glecaprevir-pibrentasvir pharmacotherapy in hepatitis C viremic heart and lung transplant recipients.

We conducted a retrospective review of thoracic transplant recipients (22 heart and 16 lung transplant recipients) prospectively enrolled in a single-center observational study of HCV NAT+ organ transplantation in HCV NAT- recipients. All recipients were treated with 8 weeks of glecaprevir-pibrentasvir (GP) for HCV viremia in addition to standard triple immunosuppression post-transplant. Thoracic transplant recipients of HCV NAT- organs were used as a control (24 heart and 22 lung transplant recipients). Our primary outcome was to assess the effect of GP on tacrolimus dose requirements. Secondary objectives included assessing drug interactions with common post-transplant medications, adverse effects, and the need to hold or discontinue GP therapy. The median tacrolimus concentration-to-dose ratio (CDR) in the cohort was 184 (99-260) during GP therapy and 154 (78-304) over the first month after GP (P = .79). Trends in median tacrolimus CDR were similar on a per-week basis and per-patient basis. In three instances, concomitant posaconazole and GP led to hyperbilirubinemia and interruption of posaconazole. GP therapy was held in one heart transplant recipient and discontinued in another due to unresolving hyperbilirubinemia. Utilization of GP to treat HCV viremia post-thoracic transplant is feasible and safe, but requires modifications to post-transplant pharmacotherapy and careful monitoring for adverse effects.

Sedation Requirements in Patients on Venovenous or Venoarterial Extracorporeal Membrane Oxygenation.

Background:There is a paucity of data evaluating optimal dosing strategies of commonly utilized opioids and sedatives for patients on extracorporeal membrane oxygenation (ECMO) support where pharmacokinetic and pharmacodynamic variables of these administered agents are altered. Objective: To assess the daily dosing requirement of sedatives and analgesics for patients on venovenous (VV) and venoarterial (VA) ECMO after the initial ECMO cannulation period. Methods: We performed a retrospective, observational study of adult patients receiving sedation and analgesia while receiving ECMO support for at least 24 hours. Patients cannulated at an outside hospital more than 24 hours before transfer, those with a history of intravenous drug use or acute alcohol withdrawal, or those who died within 48 hours of ECMO initiation were excluded. Results: We evaluated 26 patients on ECMO, including 13 on VV and 13 on VA ECMO. The median dose of fentanyl was 140 µg/h, with the VV group requiring a higher dose compared with the VA group (167 vs 106 µg/h, P < 0.001). The median doses of dexmedetomidine and propofol were 0.7 µg/kg/h and 26 µg/kg/min, respectively, with no significant differences between groups (P = 0.38 and P = 0.24, respectively). The median daily doses of fentanyl, dexmedetomidine, and propofol did not significantly increase throughout the time on ECMO support. Conclusions and Relevance: We found that the overall opioid daily dosing requirements were lower than previously reported in the literature. Additionally, light sedation strategies with a target RASS of -1 to 0 are feasible in this patient population.

Evaluation of Anti-Xa and Activated Partial Thromboplastin Time Monitoring of Heparin in Adult Patients Receiving Extracorporeal Membrane Oxygenation Support.

The approach to monitoring anticoagulation in adult patients receiving heparin on extracorporeal membrane oxygenation (ECMO) support is controversial. The objective of this study was to compare the correlation between anti-Xa and activated partial thromboplastin time (aPTT) with heparin dose and to describe their association with clinical events in adult ECMO patients. We conducted a retrospective single-center study of 34 adult ECMO patients whose heparin was monitored by anti-Xa and/or aPTT. The heparin dose-to-assay correlation coefficient was 0.106 for aPTT and 0.414 for anti-Xa (p < 0.001). Major thrombotic and hemorrhagic events occurred in 14.7% and 26.5% of patients, respectively. The median anti-Xa in patients who experienced a major thrombotic event was 0.09 (0.06-0.25) IU/mL compared with 0.36 (0.26-0.44) IU/mL in patients who did not (p = 0.031), whereas the median aPTT did not differ between these groups. The maximum aPTT in patients who experienced a major bleed was 96.9 (76.0-200) seconds compared with 63.5 (44.4-98.6) seconds in patients who did not (p = 0.049), whereas the maximum anti-Xa did not differ between these groups. Monitoring both anti-Xa and aPTT may be warranted to safely provide understanding of pure heparin activity as well as underlying bleeding diatheses in adult ECMO patients.

Venous Thromboembolism Prophylaxis: A Narrative Review With a Focus on the High-Risk Critically Ill Patient.

Venous thromboembolism (VTE) is a major health concern associated with significant morbidity and mortality. Critically ill patients are at an increased risk of VTE compared to general medical patients due to unique risk factors: prolonged immobilization, invasive lines and devices, certain medications, and acquired thrombophilia. Furthermore, VTE in the critically ill is associated with increased duration of mechanical ventilation, increased length of intensive care unit and hospital stay, and a trend toward increased mortality. Clinical practice guidelines therefore recommend VTE prophylaxis with either subcutaneous heparin or low-molecular-weight heparin for all critically ill patients without contraindication. Yet, many patients will develop VTE despite appropriate pharmacologic prophylaxis, which has led to interest in risk-stratifying critically ill patients for more aggressive prophylaxis strategies. Recent research identified patients at highest risk of failure of thromboprophylaxis and provided insight into the pathophysiologic mechanisms. Obesity and the receipt of vasopressors are 2 risk factors consistently identified in observational studies; further clinical data support decreased absorption of anticoagulant administered via the subcutaneous route as the likely mechanism behind thromboprophylaxis failure in these patient populations. Several studies have investigated novel thromboprophylaxis strategies to circumvent pharmacokinetic limitations in patients who are obese or on vasopressors: increased fixed-dose, weight-based subcutaneous, or continuous intravenous infusion of a prophylactic dose of anticoagulant has shown promise in limited studies; however, the results have yet to demonstrate superiority compared to current standard-of-care. This review discusses observational studies identifying patients at risk of thromboprophylaxis failure and critiques clinical studies evaluating novel thromboprophylaxis strategies in high-risk, critically ill patients with a focus on their limitations. Future studies are currently being conducted that will provide further guidance into the appropriate use of individualized thromboprophylaxis.

Comparative Effectiveness and Safety Between Milrinone or Dobutamine as Initial Inotrope Therapy in Cardiogenic Shock.

Inotropes are an integral component of the early stabilization of the patient presenting with cardiogenic shock. Despite years of clinical experience with the 2 most commonly used inotropes, dobutamine and milrinone, there remains limited data comparing outcomes between the two. We conducted a retrospective review to compare the effectiveness and safety of milrinone or dobutamine for the initial management of cardiogenic shock. Adult patients with cardiogenic shock regardless of etiology who received initial inotrope therapy with either milrinone (n = 50) or dobutamine (n = 50) and did not receive mechanical circulatory support were included. The primary end point was the time to resolution of cardiogenic shock. Changes in hemodynamic parameters from baseline and adverse events were also assessed. Resolution of shock was achieved in similar numbers in both the groups (milrinone 76% vs dobutamine 70%, P = .50). The median time to resolution of shock was 24 hours in both groups (P = .75). There were no differences in hemodynamic changes during inotrope therapy, although dobutamine trended toward a greater increase in cardiac index. Arrhythmias were more common in patients treated with dobutamine than milrinone, respectively (62.9% vs 32.8%, P < .01), whereas hypotension occurred to a similar extent in both groups (milrinone 49.2% vs dobutamine 40.3%, P = .32). The use of concomitant vasoactive medications, dosage required, and duration of therapy did not differ between groups. There was no difference in the overall rate of discontinuation due to adverse event; however, milrinone was more commonly discontinued due to hypotension (13.1% vs 0%, P < .01) and dobutamine was more commonly discontinued due to arrhythmia (0% vs 11.3%, P < .01). Milrinone and dobutamine demonstrated similar effectiveness and safety profiles but with differences in adverse events. The choice of milrinone or dobutamine as initial inotrope therapy for cardiogenic shock may depend more on tolerability of adverse events.

Potent adjuvantic activity of a CCR1-agonistic bis-quinoline.

A bis-quinoline compound, (7-chloro-N-(4-(7-chloroquinolin-4-ylamino)butyl)quinolin-4-amine; RE-660) was found to have C-C chemokine receptor type 1 (CCR1)-agonistic properties. RE-660 displayed strong adjuvantic activity in mice when co-administered with bovine α-lactalbumin used as a model subunit protein antigen. RE-660 evoked a balanced Th1 (IgG2)/Th2 (IgG1) antibody profile, and the quality of antibodies elicited by the bis-quinoline was found to be superior to that evoked by glucopyranosyl lipid A by surface plasmon resonance experiments. No evidence of proinflammatory activity was observed in human blood ex vivo models. In preliminary acute toxicity studies, the compound was found to be of lower toxicity than chloroquine in mice, and was non-mutagenic in an Ames screen.

Structure-activity relationships in toll-like receptor 2-agonists leading to simplified monoacyl lipopeptides.

Toll-like receptor 2-agonistic lipopeptides typified by S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-R-cysteinyl-S-serine (PAM(2)CS) compounds are potential vaccine adjuvants. In continuation of previously reported structure-activity relationships on this chemotype, we have determined that at least one acyl group of optimal length (C(16)) and an appropriately oriented ester carbonyl group is essential for TLR2-agonistic activity. The spacing between one of the palmitoyl ester carbonyl and the thioether is crucial to allow for an important H-bond, which observed in the crystal structure of the lipopeptide:TLR2 complex; consequently, activity is lost in homologated compounds. Penicillamine-derived analogues are also inactive, likely due to unfavorable steric interactions with the carbonyl of Ser 12 in TLR2. The thioether in this chemotype can be replaced with a selenoether. Importantly, the thioglycerol motif can be dispensed with altogether and can be replaced with a thioethanol bridge. These results have led to a structurally simpler, synthetically more accessible, and water-soluble analogue possessing strong TLR2-agonistic activities in human blood.

Toward self-adjuvanting subunit vaccines: model peptide and protein antigens incorporating covalently bound toll-like receptor-7 agonistic imidazoquinolines.

Toll-like receptor (TLR)-7 agonists show prominent Th1-biased immunostimulatory activities. A TLR7-active N(1)-(4-aminomethyl)benzyl substituted imidazoquinoline 1 served as a convenient precursor for the syntheses of isothiocyanate and maleimide derivatives for covalent attachment to free amine and thiol groups of peptides and proteins. 1 was also amenable to direct reductive amination with maltoheptaose without significant loss of activity. Covalent conjugation of the isothiocyanate derivative 2 to α-lactalbumin could be achieved under mild, non-denaturing conditions, in a controlled manner and with full preservation of antigenicity. The self-adjuvanting α-lactalbumin construct induced robust, high-affinity immunoglobulin titers in murine models. The premise of covalently decorating protein antigens with adjuvants offers the possibility of drastically reducing systemic exposure of the adjuvant, and yet eliciting strong, Th1-biased immune responses.