Antimicrobial prescribing after rapid influenza PCR implementation in the emergency department.

INTRO: Influenza shares common symptoms with bacterial pneumonia, which may result in unnecessary antibiotic prescriptions in the emergency department (ED) when the diagnosis is unknown. Rapid influenza polymerase chain reaction (PCR) tests have reduced turnaround times compared to standard multiplex PCR respiratory panels allowing for earlier diagnosis, which may improve antimicrobial stewardship outcomes in the ED. This study aims to compare antibiotic and antiviral use before and after deployment of the rapid influenza PCR in the ED. METHODS: This single-center, retrospective, cohort study included pediatric and adult patients discharged from the ED with a positive influenza test using a standard multiplex PCR respiratory panel (January 2017 - July 2019) or rapid PCR (July 2019 - February 2020). The primary endpoint was number of antibiotic prescriptions pre- and post-implementation of the rapid influenza PCR in the ED. Secondary endpoints included number of antiviral prescriptions, duration of antimicrobial therapy, test turnaround time, ED length of stay, 30-day readmission, and adverse events. A multivariable logistic regression evaluated patient factors associated with antimicrobial prescribing. RESULTS: A total of 620 positive influenza results were identified with 280 patients (standard multiplex PCR = 33; rapid PCR = 247) meeting inclusion criteria. Patients were less likely to be prescribed antibiotics (39.4% vs 8.9%, OR 0.15, 95% CI 0.067-0.34) and more likely to be prescribed antivirals (24.2% vs 61.1%, OR 4.92, 95% CI 2.13-11.34) with the rapid influenza PCR. Rapid influenza PCR significantly reduced ED length of stay (4.9 vs 3.4 h, p < 0.01) and test turnaround time (27 h vs 3.5 h, p < 0.01). Patients at high risk for complications associated with influenza were more likely to be prescribed antiviral therapy (22.7% vs 67.8%, OR 7.16, 95% CI 2.52-20.40). Based on the regression analysis conducted, asthma, (OR 3.5, 95% CI 1.48-8.26), immunosuppression (OR 9.6, 95% CI 1.18-78.2), and age <5 years old (OR 3.1, 95% CI 1.80-5.45) were predictors of antiviral prescribing. CONCLUSION: Implementation of a rapid influenza PCR in the ED reduced antibiotic use and optimized antiviral therapy for patients with influenza including those at higher risk of complications.

Real-Time, Multiplexed SHERLOCK for in Vitro Diagnostics.

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has highlighted the need for simple, low-cost, and scalable diagnostics that can be widely deployed for rapid testing. Clustered regularly interspaced short palindromic repeats (CRISPR)-based diagnostics have emerged as a promising technology, but its implementation in clinical laboratories has been limited by the requirement of a separate amplification step prior to CRISPR-associated (Cas) enzyme-based detection. This article reports the discovery of two novel Cas12 enzymes (SLK9 and SLK5-2) that exhibit enzymatic activity at 60°C, which, when combined with loop-mediated isothermal amplification (LAMP), enable a real-time, single-step nucleic acid detection method [real-time SHERLOCK (real-time SLK)]. Real-time SLK was demonstrated to provide accurate results comparable to those from real-time quantitative RT-PCR in clinical samples, with 100% positive and 100% negative percent agreement. The method is further demonstrated to be compatible with direct testing (real-time SLK Direct) of samples from anterior nasal swabs, without the need for standard nucleic acid extraction. Lastly, SLK9 was combined with either Alicyclobacillus acidoterrestris AacCas12b or with SLK5-2 to generate a real-time, multiplexed CRISPR-based diagnostic assay for the simultaneous detection of SARS-CoV-2 and a human-based control in a single reaction, with sensitivity down to 5 copies/µL and a time to result of under 30 minutes.

Case series of cefiderocol for salvage therapy in carbapenem-resistant Gram-negative infections.

PURPOSE: This case series describes real-world utilization of cefiderocol and associated clinical outcomes in the setting of carbapenem-resistant Gram-negative bacterial infections. METHODS: Adult hospitalized patients administered at least 5 days of cefiderocol as definitive treatment from October 1, 2020 to September 16, 2021 were included in this retrospective cohort analysis. The primary outcome was clinical success defined as a composite of 30 day survival, resolution of infection, and absence of 30 day recurrence of the same organism. RESULTS: Among 24 patients, pneumonia (19, 79%) was the most common source of infection with Acinetobacter baumannii (14, 58%) and P. aeruginosa (10, 42%) as the predominant organisms isolated. Cefiderocol monotherapy was used as definitive treatment in 16 (67%) patients. Eleven patients (46%) met clinical success. Thirty-day mortality occurred in ten (42%) patients while seven (29%) patients had recurrence of infection. Thirteen out of 21 total isolates (62%) tested for susceptibility were deemed susceptible. Of the 16 patients with available susceptibility, 9 (56%) had an infection where all isolated organisms were susceptible to cefiderocol. CONCLUSIONS: Our results provide additional insight into the in vivo activity of cefiderocol. Cefiderocol remains a salvage option for carbapenem-resistant Gram-negative organisms.

High-Throughput CRISPR-Cas13 SARS-CoV-2 Test.

BACKGROUND: The ability to control the spread of COVID-19 continues to be hampered by a lack of rapid, scalable, and easily deployable diagnostic solutions. METHODS: We developed a diagnostic method based on CRISPR (clustered regularly interspaced short palindromic repeats) that can deliver sensitive, specific, and high-throughput detection of Sudden Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2). The assay utilizes SHERLOCK (Specific High-sensitivity Enzymatic Reporter unLOCKing) for the qualitative detection of SARS-CoV-2 RNA and may be performed directly on a swab or saliva sample without nucleic acid extraction. The assay uses a 384-well format and provides results in <1 hour. RESULTS: Assay performance was evaluated with 105 (55 negative, 50 positive) remnant SARS-CoV-2 specimens previously tested using Food and Drug Administration emergency use authorized assays and retested with a modified version of the Centers for Disease Control and Prevention (CDC) quantitative PCR with reverse transcription (RT-qPCR) assay. When combined with magnetic bead-based extraction, the high-throughput SHERLOCK SARS-CoV-2 assay was 100% concordant (n = 60) with the CDC RT-qPCR. When used with direct sample addition the high-throughput assay was also 100% concordant with the CDC RT-qPCR direct method (n = 45). With direct saliva sample addition, the negative and positive percentage agreements were 100% (15/15, 95% CI: 81.8-100%) and 88% (15/17, 95% CI: 63.6-98.5%), respectively, compared with results from a collaborating clinical laboratory. CONCLUSIONS: This high-throughput assay identifies SARS-CoV-2 from patient samples with or without nucleic acid extraction with high concordance to RT-qPCR methods. This test enables high complexity laboratories to rapidly increase their testing capacities with simple equipment.

Multi-omics analysis provides insights into lignocellulosic biomass degradation by Laetiporus sulphureus ATCC 52600.

BACKGROUND: Wood-decay basidiomycetes are effective for the degradation of highly lignified and recalcitrant plant substrates. The degradation of lignocellulosic materials by brown-rot strains is carried out by carbohydrate-active enzymes and non-enzymatic Fenton mechanism. Differences in the lignocellulose catabolism among closely related brown rots are not completely understood. Here, a multi-omics approach provided a global understanding of the strategies employed by L. sulphureus ATCC 52600 for lignocellulose degradation. RESULTS: The genome of Laetiporus sulphureus ATCC 52600 was sequenced and phylogenomic analysis supported monophyletic clades for the Order Polyporales and classification of this species within the family Laetiporaceae. Additionally, the plasticity of its metabolism was revealed in growth analysis on mono- and disaccharides, and polysaccharides such as cellulose, hemicelluloses, and polygalacturonic acid. The response of this fungus to the presence of lignocellulosic substrates was analyzed by transcriptomics and proteomics and evidenced the occurrence of an integrated oxidative-hydrolytic metabolism. The transcriptomic profile in response to a short cultivation period on sugarcane bagasse revealed 125 upregulated transcripts, which included CAZymes (redox enzymes and hemicellulases) as well as non-CAZy redox enzymes and genes related to the synthesis of low-molecular-weight compounds. The exoproteome produced in response to extended cultivation time on Avicel, and steam-exploded sugarcane bagasse, sugarcane straw, and Eucalyptus revealed 112 proteins. Contrasting with the mainly oxidative profile observed in the transcriptome, the secretomes showed a diverse hydrolytic repertoire including constitutive cellulases and hemicellulases, in addition to 19 upregulated CAZymes. The secretome induced for 7 days on sugarcane bagasse, representative of the late response, was applied in the saccharification of hydrothermally pretreated grass (sugarcane straw) and softwood (pine) by supplementing a commercial cocktail. CONCLUSION: This study shows the singularity of L. sulphureus ATCC 52600 compared to other Polyporales brown rots, regarding the presence of cellobiohydrolase and peroxidase class II. The multi-omics analysis reinforces the oxidative-hydrolytic metabolism involved in lignocellulose deconstruction, providing insights into the overall mechanisms as well as specific proteins of each step.

Control of a programmed cell death pathway in Pseudomonas aeruginosa by an antiterminator.

In Pseudomonas aeruginosa the alp system encodes a programmed cell death pathway that is switched on in a subset of cells in response to DNA damage and is linked to the virulence of the organism. Here we show that the central regulator of this pathway, AlpA, exerts its effects by acting as an antiterminator rather than a transcription activator. In particular, we present evidence that AlpA positively regulates the alpBCDE cell lysis genes, as well as genes in a second newly identified target locus, by recognizing specific DNA sites within the promoter, then binding RNA polymerase directly and allowing it to bypass intrinsic terminators positioned downstream. AlpA thus functions in a mechanistically unusual manner to control the expression of virulence genes in this opportunistic pathogen.

Oral fluoroquinolones for definitive treatment of gram-negative bacteremia in cancer patients.

PURPOSE: Bloodstream infections (BSI) are significant causes of morbidity and mortality in cancer patients. These patients often receive 10 to 14 days of intravenous (IV) antibiotics. The objective of this study was to compare the outcomes of cancer patients transitioned from IV to oral (PO) therapy compared to continuation of IV treatment. METHODS: This was a single-center, retrospective cohort study of hospitalized adult cancer patients with gram-negative bacteremia. Patients transitioned to a PO fluoroquinolone (FQ) within 5 days were allocated to the IV-to-PO group, while the remaining patients comprised the IV group. The primary outcome was the composite of treatment failure, defined as infection-related readmission, infection recurrence, or inpatient mortality. A multivariable logistic regression model was constructed to account for confounding variables. Secondary outcomes assessed included infection-related length of stay (LOS), hospital LOS, and adverse events, such as Clostridioides difficile infection and catheter-related complications. RESULTS: The IV-to-PO group included 78 patients, while the remaining 133 patients were allocated to the IV group. Differences at baseline included more hematologic malignancy, neutropenia, ICU admissions, and higher Pitt bacteremia scores in the IV group. The rate of treatment failure was significantly higher in the IV group (24% vs 9%; p < 0.01), which persisted in the logistic regression (aOR 3.5, 95% CI 1.3-9.1). The IV-to-PO group had decreased infection-related and hospital length of stay, as well as fewer catheter-related complications. CONCLUSIONS: The use of PO FQ may be considered for the definitive treatment of uncomplicated Enterobacterales BSI in cancer patients.

Fluoroquinolone versus Beta-Lactam Oral Step-Down Therapy for Uncomplicated Streptococcal Bloodstream Infections.

Fluoroquinolones (FQs) are often preferred as oral step-down therapy for bloodstream infections (BSIs) due to favorable pharmacokinetic parameters; however, they are also associated with serious adverse events. The objective of this study was to compare clinical outcomes for patients who received an oral FQ versus an oral beta-lactam (BL) as step-down therapy for uncomplicated streptococcal BSIs. This multicenter, retrospective cohort study analyzed adult patients who completed therapy with an oral FQ or BL with at least one blood culture positive for a Streptococcus species from 1 January 2014 to 30 June 2019. The primary outcome was clinical success, defined as the lack of all-cause mortality, recurrent BSI with the same organism, and infection-related readmission at 90 days. A multivariable logistic regression model for predictors of clinical failure was conducted. A total of 220 patients were included, with 87 (40%) receiving an FQ and 133 (60%) receiving a BL. Step-down therapy with an oral BL was noninferior to an oral FQ (93.2% versus 92.0%; mean difference, 1.2%; 90% confidence interval [CI], -5.2 to 7.8). No differences were seen in 90-day mortality, 90-day recurrent BSI, 90-day infection-related readmission, or 90-day incidence of Clostridioides difficile-associated diarrhea. Predictors of clinical failure included oral step-down transition before day 3 (odds ratio [OR] = 5.18; 95% CI, 1.21, 22.16) and low-dose oral step-down therapy (OR = 2.74; 95% CI, 0.95, 7.90). Our results suggest that oral step-down therapy for uncomplicated streptococcal BSI with a BL is noninferior to an FQ.

Impact of Mandatory Infectious Diseases Consultation and Real-time Antimicrobial Stewardship Pharmacist Intervention on Staphylococcus aureus Bacteremia Bundle Adherence.

BACKGROUND: The purpose of this study was to evaluate the impact of infectious diseases consultation (IDC) and a real-time antimicrobial stewardship (AMS) review on the management of Staphylococcus aureus bacteremia (SAB). METHODS: This retrospective study included adult inpatients with SAB from January 2016 to December 2018 at 7 hospitals. Outcomes were compared between 3 time periods: before mandatory IDC and AMS review (period 1), after mandatory IDC and before AMS review (period 2), and after mandatory IDC and AMS review (period 3). The primary outcome was bundle adherence, defined as appropriate intravenous antimicrobial therapy, appropriate duration of therapy, appropriate surveillance cultures, echocardiography, and removal of indwelling intravenous catheters, if applicable. Secondary end points included individual bundle components, source control, length of stay (LOS), 30-day bacteremia-related readmission, and in-hospital all-cause mortality. RESULTS: A total of 579 patients met inclusion criteria for analysis. Complete bundle adherence was 65% in period 1 (n = 241/371), 54% in period 2 (n = 47/87), and 76% in period 3 (n = 92/121). Relative to period 3, bundle adherence was significantly lower in period 1 (odds ratio [OR], 0.58; 95% confidence interval [CI], 0.37-0.93; P = .02) and period 2 (OR, 0.37; 95% CI, 0.20-0.67; P = .0009). No difference in bundle adherence was noted between periods 1 and 2. Significant differences were seen in obtaining echocardiography (91% vs 83% vs 100%; P < .001), source control (34% vs 45% vs 45%; P = .04), and hospital LOS (10.5 vs 8.9 vs 12.0 days; P = .01). No differences were noted for readmission or mortality. CONCLUSIONS: The addition of AMS pharmacist review to mandatory IDC was associated with significantly improved quality care bundle adherence.

Clinical Outcomes of Patients Treated for Candida auris Infections in a Multisite Health System, Illinois, USA.

Candida auris is an emerging fungal pathogen that is typically resistant to fluconazole and is known to cause healthcare-associated outbreaks. We retrospectively reviewed 28 patients who had >1 positive culture for C. auris within a multisite health system in Illinois, USA, during May 2018-April 2019. Twelve of these patients were treated as inpatients for C. auris infections; 10 (83%) met criteria for clinical success, defined as absence of all-cause mortality, C. auris recurrence, and infection-related readmission at 30 days from the first positive culture. The other 2 patients (17%) died within 30 days. Most patients (92%) were empirically treated with micafungin. Four (14%) of 28 total isolates were resistant to fluconazole, 1 (3.6%) was resistant to amphotericin B, and 1 (3.6%) was resistant to echinocandins. Our findings describe low rates of antifungal resistance and favorable clinical outcomes for most C. auris patients.

Efficacy of combination therapy versus monotherapy in the treatment of Stenotrophomonas maltophilia pneumonia.

BACKGROUND: Stenotrophomonas maltophilia is intrinsically resistant to several antibiotics, making it potentially challenging to treat. Studies have demonstrated treatment failures and resistance development with monotherapy (MT); however, clinical data are limited with combination therapy (CT). OBJECTIVES: To compare clinical outcomes with CT versus MT for S. maltophilia pneumonia. METHODS: This was a retrospective cohort study of patients admitted between November 2011 and October 2017 with S. maltophilia pneumonia who received at least 48 h of effective therapy. The primary outcome was clinical response after 7 days of effective therapy with CT versus MT. Secondary outcomes included development of a non-susceptible isolate, 30 day microbiological cure, infection recurrence, infection-related mortality and all-cause mortality. The Wilcoxon rank sum test, the Pearson χ2 test and Fisher's exact test were utilized for univariate analyses. A multivariable logistic regression model was used to assess clinical response while adjusting for confounding variables. RESULTS: Of 252 patients with S. maltophilia pneumonia included, 38 received CT and 214 received MT. There was no difference in 7 day clinical response with CT versus MT (47.4% versus 39.7%, P = 0.38), even after controlling for immune status, APACHE II score and polymicrobial pneumonia (adjusted OR 1.51, 95% CI 0.63-3.65). Thirty day microbiological cure (P = 0.44), recurrence (P = 0.53), infection-related mortality (P = 0.19) and isolation of a non-susceptible isolate during or after therapy (P = 1.00 each) were also similar between both groups; however, 30 day all-cause mortality was greater with CT (P = 0.03). CONCLUSIONS: CT had similar rates of clinical efficacy and resistance development compared with MT for S. maltophilia pneumonia.

Genomic Profiling Reveals Medullary Thyroid Cancer Misdiagnosed as Lung Cancer.

Mutations or other alterations in the RET gene have been implicated in a variety of malignancies - most commonly thyroid, but also chronic myelomonocytic leukemia, acute myeloid leukemia, and lung, breast, pancreatic, and colon cancers. Here we present a case of a gentlemen initially diagnosed with and treated for non-small cell lung adenocarcinoma. Genomic profiling of his tumor specimen revealed a RET point mutation with a known association with medullary thyroid cancer (MTC). Further pathological and molecular diagnostic evaluation confirmed a diagnosis of MTC, leading to a change in treatment from standard chemotherapy for non-small cell lung cancer to targeted therapy against RET and potential implications regarding inherited cancer risk for his offspring. The patient experienced a clinical response to treatment and several months of improved quality of life. This case illustrates the capacity of genomic profiling to uncover molecular drivers of disease and help ensure proper diagnosis and management of cancer.

Multiple-Dose Oritavancin Evaluation in a Retrospective Cohort of Patients with Complicated Infections.

OBJECTIVE: Oritavancin is a lipoglycopeptide antibiotic approved for use in acute bacterial skin and skin structure infections as a single 1200-mg parenteral dose. Because of oritavancin's long half-life and broad gram-positive activity, interest in its use for other infections is high. METHODS: This study is a retrospective cohort evaluation of patients receiving oritavancin at a single academic medical center. All patients receiving more than one dose of oritavancin were included. Patients were excluded if therapy was interrupted by more than 14 days. Efficacy, defined a priori as clinical success, improvement, or failure, and adverse drug effect outcomes were collected. RESULTS: Seventeen patients received multiple oritavancin doses (range 2-18 doses) for the treatment of complicated infections including osteomyelitis, surgical site infection, intravascular infections, and pneumonia. All patients achieved clinical success or improvement with oritavancin. Four patients (24%) had an adverse event requiring oritavancin discontinuation that reversed rapidly. CONCLUSIONS: Off-label oritavancin use may be a safe and effective alternative to daily antibiotic infusions to treat complicated infectious disease processes. This study is limited by small sample size and retrospective design, but it provides information on using oritavancin in these complex gram-positive infections.

Top 1% of Inpatients Administered Antimicrobial Agents Comprising 50% of Expenditures: A Descriptive Study and Opportunities for Stewardship Intervention.

OBJECTIVE To characterize the top 1% of inpatients who contributed to the 6-month antimicrobial budget in a tertiary, academic medical center and identify cost-effective intervention opportunities targeting high-cost antimicrobial utilization. DESIGN Retrospective cohort study. PATIENTS Top 1% of the antimicrobial budget from July 1 through December 31, 2014. METHODS Patients were identified through a pharmacy billing database. Baseline characteristics were collected through a retrospective medical chart review. Patients were presented to the antimicrobial stewardship team to determine appropriate utilization of high-cost antimicrobials and potential intervention opportunities. Appropriate use was defined as antimicrobial therapy that was effective, safe, and most cost-effective compared with alternative agents. RESULTS A total of 10,460 patients received antimicrobials in 6 months; 106 patients accounted for $889,543 (47.2%) of the antimicrobial budget with an antimicrobial cost per day of $219±$192 and antimicrobial cost per admission of $4,733±$7,614. Most patients were immunocompromised (75%) and were followed by the infectious disease consult service (80%). The most commonly prescribed antimicrobials for treatment were daptomycin, micafungin, liposomal amphotericin B, and meropenem. Posaconazole and valganciclovir accounted for most of the prophylactic therapy. Cost-effective opportunities (n=71) were present in 57 (54%) of 106 patients, which included dose optimization, de-escalation, dosage form conversion, and improvement in transitions of care. CONCLUSION Antimicrobial stewardship oversight is important in implementing cost-effective strategies, especially in complex and immunocompromised patients who require the use of high-cost antimicrobials. Infect Control Hosp Epidemiol 2017;38:259-265.

Secuencia disrrafia-exencefalia-anencefalia asociado a brida amniótica, Síndrome de Klinefelter y polihidramnios / Dysraphia-exencephaly-anencephaly sequence associated with amniotic band, Klinefelter syndrome and polyhydramnios

Los defectos del tubo neural son un grupo heterogéneo y complejo de anomalías del sistema nervioso central que se encuentran entre las anormalidades congénitas humanas más frecuentes, sólo superados por los defectos cardiovasculares, excluyendo las alteraciones cromosómicas. Se caracteriza por ser el resultado final de una anomalía progresiva que se inicia con un disrrafismo del neuroporo rostral por un defecto mesenquimal, seguido de una segunda fase de exposición de hemisferios cerebrales bien diferenciados desarrollado fuera del cráneo embrionario concluyendo con una fase de desintegración. Puede presentarse como evento único o asociado a otras malformaciones. Reportamos tres casos de secuencia disrrafia-exencefalia-anencefalia, uno de ellos en presencia de polihidramnios, otro asociado a síndrome de brida amniótica y otro cuyo estudio cromosómico reporta síndrome de Klinefelter, todos con un resultado común, mal pronóstico perinatal.

Neural tube defects are a complex of central nervous system abnormalities that are among the most common human congenital abnormalities, second only to cardiovascular defects, excluding chromosomal abnormalities and heterogeneous group. It is characterized as the end result of a progressive anomaly that starts with a dysraphism the rostral neuropore by a mesenchymal defect, followed by a second phase exhibit distinct cerebral hemispheres developed beyond the embryonic skull concluding with a phase of disintegration. It can occur as a single event or associated with other malformations. We report three cases of anencephaly -exencephaly-dysraphism sequence, one of them in the presence of polyhydramnios, other associated amniotic band syndrome and other chromosomal study reports Klinefelter syndrome, all with a common result, poor perinatal outcome.

Variation in the susceptibility of Drosophila to different entomopathogenic nematodes.

Entomopathogenic nematodes (EPNs) in the genera Heterorhabditis and Steinernema are lethal parasites of insects that are of interest as models for understanding parasite-host interactions and as biocontrol agents for insect pests. EPNs harbor a bacterial endosymbiont in their gut that assists in insect killing. EPNs are capable of infecting and killing a wide range of insects, yet how the nematodes and their bacterial endosymbionts interact with the insect immune system is poorly understood. Here, we develop a versatile model system for understanding the insect immune response to parasitic nematode infection that consists of seven species of EPNs as model parasites and five species of Drosophila fruit flies as model hosts. We show that the EPN Steinernema carpocapsae, which is widely used for insect control, is capable of infecting and killing D. melanogaster larvae. S. carpocapsae is associated with the bacterium Xenorhabdus nematophila, and we show that X. nematophila induces expression of a subset of antimicrobial peptide genes and suppresses the melanization response to the nematode. We further show that EPNs vary in their virulence toward D. melanogaster and that Drosophila species vary in their susceptibilities to EPN infection. Differences in virulence among different EPN-host combinations result from differences in both rates of infection and rates of postinfection survival. Our results establish a powerful model system for understanding mechanisms of host-parasite interactions and the insect immune response to parasitic nematode infection.

Sequential conformational rearrangements in flavivirus membrane fusion.

The West Nile Virus (WNV) envelope protein, E, promotes membrane fusion during viral cell entry by undergoing a low-pH triggered conformational reorganization. We have examined the mechanism of WNV fusion and sought evidence for potential intermediates during the conformational transition by following hemifusion of WNV virus-like particles (VLPs) in a single particle format. We have introduced specific mutations into E, to relate their influence on fusion kinetics to structural features of the protein. At the level of individual E subunits, trimer formation and membrane engagement of the threefold clustered fusion loops are rate-limiting. Hemifusion requires at least two adjacent trimers. Simulation of the kinetics indicates that availability of competent monomers within the contact zone between virus and target membrane makes trimerization a bottleneck in hemifusion. We discuss the implications of the model we have derived for mechanisms of membrane fusion in other contexts.

A phase II multicenter rabbit anti-thymocyte globulin trial in patients with myelodysplastic syndromes identifying a novel model for response prediction.

Immune dysregulation is a mechanism contributing to ineffective hematopoiesis in a subset of myelodysplastic syndrome patients. We report the first US multicenter non-randomized, phase II trial examining the efficacy of rabbit(r)-anti-thymocyte globulin using 2.5 mg/kg/day administered daily for 4 doses. The primary end point was hematologic response; secondary end points included duration of response, time to response, time to progression, and tolerance. Nine (33%;95% confidence interval=17%-54%) of the 27 patients treated experienced durable hematologic improvement in an intent-to-treat analysis with a median time to response and median response duration of 75 and 245 days, respectively. While younger age is the most significant factor favoring equine(e)-anti-thymocyte globulin response, treatment outcome on this study was independent of age (P=0.499). A shorter duration between diagnosis and treatment showed a positive trend (P=0.18), but International Prognostic Scoring System score (P=0.150), karyotype (P=0.319), and age-adjusted bone marrow cellularity (P=0.369) were not associated with response classification. Since activated T-lymphocytes are the primary cellular target of anti-thymocyte globulin, a T-cell expression profiling was conducted in a cohort of 38 patients consisting of rabbit and equine-antithymocyte globulin-treated patients. A model containing disease duration, CD8 terminal memory T cells and T-cell proliferation-associated-antigen expression predicted response with the greatest accuracy using a leave-one-out cross validation approach. This profile categorized patients independent of other covariates, including treatment type and age using a leave-one-out-cross-validation approach (75.7%). Therefore, rabbit-anti-thymocyte globulin has hematologic remitting activity in myelodysplastic syndrome and a T-cell activation profile has potential utility classifying those who are more likely to respond (NCT00466843 clinicaltrials.gov).