Remote surveillance and detection of SARS-CoV-2 transmission among household members in King County, Washington.

BACKGROUND: Early during the COVID-19 pandemic, it was important to better understand transmission dynamics of SARS-CoV-2, the virus that causes COVID-19. Household contacts of infected individuals are particularly at risk for infection, but delays in contact tracing, delays in testing contacts, and isolation and quarantine posed challenges to accurately capturing secondary household cases. METHODS: In this study, 346 households in the Seattle region were provided with respiratory specimen collection kits and remotely monitored using web-based surveys for respiratory illness symptoms weekly between October 1, 2020, and June 20, 2021. Symptomatic participants collected respiratory specimens at symptom onset and mailed specimens to the central laboratory in Seattle. Specimens were tested for SARS-CoV-2 using RT-PCR with whole genome sequencing attempted when positive. SARS-CoV-2-infected individuals were notified, and their household contacts submitted specimens every 2 days for 14 days. RESULTS: In total, 1371 participants collected 2029 specimens that were tested; 16 individuals (1.2%) within 6 households tested positive for SARS-CoV-2 during the study period. Full genome sequences were generated from 11 individuals within 4 households. Very little genetic variation was found among SARS-CoV-2 viruses sequenced from different individuals in the same household, supporting transmission within the household. CONCLUSIONS: This study indicates web-based surveillance of respiratory symptoms, combined with rapid and longitudinal specimen collection and remote contact tracing, provides a viable strategy to monitor households and detect household transmission of SARS-CoV-2. TRIAL REGISTRATION IDENTIFIER: NCT04141930, Date of registration 28/10/2019.

Using population pharmacokinetics to optimize initial vancomycin dosing guidelines for neonates to treat sepsis caused by coagulase-negative staphylococcus.

INTRODUCTION: Vancomycin dosing tailored for newborns is challenging due to the significant influence of maturation and organ function on pharmacokinetics. Population pharmacokinetic (popPK) models can be used to improve target attainment in neonates. OBJECTIVES: The primary objective was to derive and evaluate a popPK model of intravenous vancomycin for neonates. Second, the predictive performance of this popPK model was compared with published popPK models. METHODS: This is a retrospective cohort study of neonates admitted to the neonatal intensive care unit receiving intravenous vancomycin. A popPK model was derived with 70% of the dataset using a nonlinear mixed effects modeling method. The predictive performance of the current popPK model was validated and compared with 22 published popPK models using the remaining 30% of the dataset. Monte Carlo simulations (MCS) were performed to derive optimal dosing regimens to treat neonatal sepsis caused by coagulase-negative staphylococci (CoNS). RESULTS: Among 655 vancomycin courses from 448 neonates, 78% of vancomycin trough concentrations were outside target range (10-15 mg/L) for central nervous system infections and 43% were outside target range (5-12 mg/L) for other infections using the institution's vancomycin dosing. A one-compartment model best described the observed data with a mean clearance of 0.11 ± 0.03 L/kg/h and volume of distribution (V) of 1.02 ± 0.08 L/kg. Body weight (WT), postmenstrual age (PMA), and serum creatinine (SCr) were significant covariates associated with clearance (p < 0.001) and body WT was a significant covariate associated with V (p = 0.009). Our study's popPK model has similar or better accuracy and precision than other published models. MCS-derived vancomycin doses from the validated model achieved >90% target attainment for a steady state through target range of 10-15 mg/L in the majority of PMA and SCr categories (78%) to treat CoNS sepsis. CONCLUSION: A vancomycin dosing guideline derived from a validated popPK model in neonates with CoNS sepsis is recommended to improve target attainment.

Association between vancomycin therapeutic drug monitoring and clinical outcomes in treating neonatal sepsis.

BACKGROUND: Neonatal sepsis is commonly treated with vancomycin in the neonatal intensive care unit. Therapeutic drug monitoring of vancomycin is routinely used to personalise dosing to optimise effectiveness and avoid toxicity. OBJECTIVES: This study aimed to define a target range by evaluating associations between vancomycin trough concentrations or area under the concentration time curve over 24 hours (AUC24h) and clinical outcomes in neonates. METHODS: Neonates, who were admitted to the neonatal intensive care unit and received intravenous vancomycin, were included in this retrospective cohort study. For evaluating effectiveness, patients who received vancomycin for < 5 days were excluded. The AUC24h was estimated based on a study-derived population pharmacokinetic model. Primary outcomes were persistent/recurrent infections and mortality within 30 days. Secondary outcomes, including acute kidney injury (AKI), were also assessed. Logistic regression and classification and regression tree analyses were performed. RESULTS: A total of 448 patients (123 patients for effectiveness analysis) were included. A vancomycin trough > 10 mg/L was associated with 70% lower odds of persistent/recurrent infections (adjusted OR 0.30, 95% CI 0.09-0.86; P = 0.023). Patients who took more than a day to reach target range had 1.4 times higher odds of persistent/recurrent infections or death (P = 0.04). A vancomycin trough > 15 mg/L was associated with a three times higher risk of AKI (P = 0.003). An AUC24h of 420-650 mg*h/L was also associated with the lowest risk of composite outcomes (adjusted OR 0.29, 95% CI 0.08-0.86; P = 0.025). CONCLUSION: A vancomycin trough target range of 10-15 mg/L and achievement of this target within a day of treatment initiation were associated with the most optimal clinical outcomes in treating neonatal sepsis.

Metabolic acidosis during continuous glucagon therapy for neonatal hypoglycemia.

Objectives: Refractory neonatal hypoglycemia may be treated with glucagon infusions, which have been associated with thrombocytopenia and hyponatremia. After anecdotally noting metabolic acidosis during glucagon therapy in our hospital, an outcome not previously reported in the literature, we aimed to quantify occurrence of metabolic acidosis (base excess >-6) as well as thrombocytopenia and hyponatremia during treatment with glucagon. Methods: We performed a single-centre retrospective case series. Descriptive statistics were used and subgroups compared with Chi-Square, Fisher's Exact Test, and Mann-Whitney U testing. Results: Sixty-two infants (mean birth gestational age 37.2 weeks, 64.5% male) were treated with continuous glucagon infusions for median 10 days during the study period. 41.2% were preterm, 21.0% were small for gestational age, and 30.6% were infants of diabetic mothers. Metabolic acidosis was seen in 59.6% and was more common in infants who were not born to diabetic mothers (75% versus 24% in infants of diabetic mothers, P<0.001). Infants with versus without metabolic acidosis had lower birth weights (median 2,743 g versus 3,854 g, P<0.01) and were treated with higher doses of glucagon (0.02 versus 0.01 mg/kg/h, P<0.01) for a longer duration (12.4 versus 5.9 days, P<0.01). Thrombocytopenia was diagnosed in 51.9% of patients. Conclusions: In addition to thrombocytopenia, metabolic acidosis of unclear etiology appears to be very common with glucagon infusions for neonatal hypoglycemia, especially in lower birth weight infants or those born to mothers without diabetes. Further research is needed to elucidate causation and potential mechanisms.

Utilizing therapeutic drug monitoring to optimize therapy with eculizumab and mycophenolate mofetil in a child with C3 glomerulonephritis.

BACKGROUND: C3 glomerulonephritis (C3GN) can be a devastating disease with poor response to immunosuppressive therapy. Complement inhibition with eculizumab has had equivocal results in patients with C3GN. CASE-DIAGNOSIS/TREATMENT: We report a case of a 6-year-old boy with C3GN presenting with nephrotic syndrome, severe hypertension and impaired kidney function. He did not respond to initial treatment with prednisone and mycophenolate (mofetil and sodium), and subsequent treatment with standard dosing of eculizumab. Pharmacokinetic studies identified a lack of eculizumab exposure and subsequent intensification of treatment with weekly dosing of eculizumab led to significant clinical improvement: his kidney function normalized, hypertension (weaned off 3 antihypertensive drugs), edema and proteinuria improved. Additionally, exposure to mycophenolic acid (MPA), active metabolite of mycophenolate, determined by area under the concentration-time curve of MPA was low throughout, despite significant dosing escalation. CONCLUSIONS: This case report demonstrates that individualized therapy guided by therapeutic drug monitoring might be needed in patients with nephrotic range proteinuria treated with eculizumab and mycophenolate (mofetil and sodium), an important finding that needs to be considered for further treatment trials.

Interactions among 17 respiratory pathogens: a cross-sectional study using clinical and community surveillance data.

Background: Co-circulating respiratory pathogens can interfere with or promote each other, leading to important effects on disease epidemiology. Estimating the magnitude of pathogen-pathogen interactions from clinical specimens is challenging because sampling from symptomatic individuals can create biased estimates. Methods: We conducted an observational, cross-sectional study using samples collected by the Seattle Flu Study between 11 November 2018 and 20 August 2021. Samples that tested positive via RT-qPCR for at least one of 17 potential respiratory pathogens were included in this study. Semi-quantitative cycle threshold (Ct) values were used to measure pathogen load. Differences in pathogen load between monoinfected and coinfected samples were assessed using linear regression adjusting for age, season, and recruitment channel. Results: 21,686 samples were positive for at least one potential pathogen. Most prevalent were rhinovirus (33·5%), Streptococcus pneumoniae (SPn, 29·0%), SARS-CoV-2 (13.8%) and influenza A/H1N1 (9·6%). 140 potential pathogen pairs were included for analysis, and 56 (40%) pairs yielded significant Ct differences (p < 0.01) between monoinfected and co-infected samples. We observed no virus-virus pairs showing evidence of significant facilitating interactions, and found significant viral load decrease among 37 of 108 (34%) assessed pairs. Samples positive with SPn and a virus were consistently associated with increased SPn load. Conclusions: Viral load data can be used to overcome sampling bias in studies of pathogen-pathogen interactions. When applied to respiratory pathogens, we found evidence of viral-SPn facilitation and several examples of viral-viral interference. Multipathogen surveillance is a cost-efficient data collection approach, with added clinical and epidemiological informational value over single-pathogen testing, but requires careful analysis to mitigate selection bias.

Therapeutic Drug Monitoring of Moxifloxacin to Guide Treatment of Mycoplasma hominis Meningitis in an Extremely Preterm Infant.

Mycoplasma hominis (M hominis) is a rare cause of neonatal bacterial meningitis. Treatment can be challenging because of M hominis' intrinsic antibiotic resistance and the difficulty in accessing antimicrobial susceptibility testing. In this report, we describe an extremely preterm male infant with seizures who had a subsequent diagnosis of M hominis meningitis. Because of severity of illness, doxycycline (4 mg/kg IV every 24 hours) and moxifloxacin (5 mg/kg IV every 24 hours) were started empirically. Repeat cerebrospinal fluid cultures were negative and showed decreasing pleiocytosis. Given the concentration-dependent killing of moxifloxacin and concern for endovascular infection from a concomitant cerebral venous sinus thrombosis, serum concentrations of moxifloxacin were obtained to estimate pharmacokinetic and pharmacodynamic parameters. These were compared to the targets described in other case reports of M hominis meningitis. The maximum serum concentration (Cmax) was 2.5 mg/L, volume of distribution was 2.2 L/kg, clearance was 0.18 L/kg/hr, terminal half-life was 8.6 hours, and area-under-the-concentration-time curve (AUC) was 28.1 mg•hr/L. Using the range of minimum inhibitory concentrations (MICs) reported in the literature, the estimated Cmax/MIC for this patient was 21 to 158 (target Cmax/MIC: >10) and AUC/MIC was 234 to 1757 (target AUC/MIC: ≥100). Doxycycline and moxifloxacin were continued for 6 weeks. No adverse events to moxifloxacin or doxycycline were observed in the NICU. This report describes the successful treatment of M hominis neonatal meningitis and adds to the knowledge of pharmacokinetic and pharmacodynamic parameters of moxifloxacin in neonates. Additional data will help to confirm the role for routine therapeutic drug monitoring of moxifloxacin in neonates.

Comparison of Symptoms and RNA Levels in Children and Adults With SARS-CoV-2 Infection in the Community Setting.

Importance: The association between COVID-19 symptoms and SARS-CoV-2 viral levels in children living in the community is not well understood. Objective: To characterize symptoms of pediatric COVID-19 in the community and analyze the association between symptoms and SARS-CoV-2 RNA levels, as approximated by cycle threshold (Ct) values, in children and adults. Design, Setting, and Participants: This cross-sectional study used a respiratory virus surveillance platform in persons of all ages to detect community COVID-19 cases from March 23 to November 9, 2020. A population-based convenience sample of children younger than 18 years and adults in King County, Washington, who enrolled online for home self-collection of upper respiratory samples for SARS-CoV-2 testing were included. Exposures: Detection of SARS-CoV-2 RNA by reverse transcription-polymerase chain reaction (RT-PCR) from participant-collected samples. Main Outcomes and Measures: RT-PCR-confirmed SARS-CoV-2 infection, with Ct values stratified by age and symptoms. Results: Among 555 SARS-CoV-2-positive participants (mean [SD] age, 33.7 [20.1] years; 320 were female [57.7%]), 47 of 123 children (38.2%) were asymptomatic compared with 31 of 432 adults (7.2%). When symptomatic, fewer symptoms were reported in children compared with adults (mean [SD], 1.6 [2.0] vs 4.5 [3.1]). Symptomatic individuals had lower Ct values (which corresponded to higher viral RNA levels) than asymptomatic individuals (adjusted estimate for children, -3.0; 95% CI, -5.5 to -0.6; P = .02; adjusted estimate for adults, -2.9; 95% CI, -5.2 to -0.6; P = .01). The difference in mean Ct values was neither statistically significant between symptomatic children and symptomatic adults (adjusted estimate, -0.7; 95% CI, -2.2 to 0.9; P = .41) nor between asymptomatic children and asymptomatic adults (adjusted estimate, -0.6; 95% CI, -4.0 to 2.8; P = .74). Conclusions and Relevance: In this community-based cross-sectional study, SARS-CoV-2 RNA levels, as determined by Ct values, were significantly higher in symptomatic individuals than in asymptomatic individuals and no significant age-related differences were found. Further research is needed to understand the role of SARS-CoV-2 RNA levels and viral transmission.

Population Pharmacokinetic Models of Vancomycin in Paediatric Patients: A Systematic Review.

BACKGROUND: Vancomycin is commonly used to treat gram-positive bacterial infections in the paediatric population, but dosing can be challenging. Population pharmacokinetic (popPK) modelling can improve individualization of dosing regimens. The primary objective of this study was to describe popPK models of vancomycin and factors that influence pharmacokinetic (PK) variability in paediatric patients. METHODS: Systematic searches were conducted in the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, International Pharmaceutical Abstracts and the grey literature without language or publication status restrictions from inception to 17 August 2020. Observational studies that described the development of popPK models of vancomycin in paediatric patients (< 18 years of age) were included. Risk of bias was assessed using the National Heart, Lung and Blood Institute Study Quality Assessment Tool for Case Series Studies. RESULTS: Sixty-four observational studies (1 randomized controlled trial, 13 prospective studies and 50 retrospective studies of 9019 patients with at least 25,769 serum vancomycin concentrations) were included. The mean age was 2.5 years (range 1 day-18 years), serum creatinine was 47.1 ± 33.6 µmol/L, and estimated creatinine clearance was 97.4 ± 76 mL/min/1.73m2. Most studies found that vancomycin PK was best described by a one-compartment model (71.9%). There was a wide range of clearance and volume of distribution (Vd) values (range 0.014-0.27 L/kg/h and 0.43-1.46 L/kg, respectively) with interindividual variability as high as 49.7% for clearance and 136% for Vd, proportional residual variability up to 37.5% and additive residual variability up to 17.5 mg/L. The most significant covariates for clearance were weight, age, and serum creatinine or creatinine clearance, and weight for Vd. Variable dosing recommendations were suggested. CONCLUSION: Numerous popPK models of vancomycin were derived, however external validation of suggested dosing regimens and analyses in subgroup paediatric populations such as dialysis patients are still needed before a popPK model with best predictive performance can be applied for dosing recommendations. Significant intraindividual and interindividual PK variability was present, which demonstrated the need for ongoing therapeutic drug monitoring and derivation of PK models for vancomycin for certain subgroup populations, such as dialysis patients.

Pharmacokinetics of Vancomycin in Pediatric Patients Receiving Intermittent Hemodialysis or Hemodiafiltration.

INTRODUCTION: Vancomycin is a common antibiotic used to treat hemodialysis (HD) or hemodiafiltration (HDF)-related infections in pediatric patients, but optimal dosing remains unknown. This is the first observational study to characterize the pharmacokinetics and evaluate dosing of vancomycin in this population. METHODS: Eligible patients received IV vancomycin 10 mg/kg per dose postdialysis followed by a series of serum vancomycin concentrations collected before, immediately after, 1 hour after, and 4 hours after dialysis. The pharmacokinetic parameters were estimated using 1- and 2-compartment models and a nonlinear least-squares algorithm. RESULTS: Among 42 vancomycin courses in 16 patients, 1 compartment model had the best fit for observed data. The net drug removal was 43 ± 13% (39% for HD and 50% for HDF) from an average 3-hour HD/HDF session. The mean elimination constant was 0.28 h-1 (standard deviation [SD], 0.11 h-1) during the intradialytic period compared with 0.0049 h-1 (SD, 0.004 h-1) when off dialysis. The mean volume of distribution was 0.65 (SD, 0.19) L/kg. Duration of dialysis session and mode of dialysis (HD vs. HDF) were significant predictors of vancomycin pharmacokinetic parameters. Half-life was shorter for HDF compared with HD (2.1 vs. 3.5 hours). CONCLUSIONS: Based on the simulations, an initial vancomycin dose of 10 mg/kg per dose and redosing postdialysis was optimal to achieve a vancomycin concentration range of 5 to 12 mg/L at 4 hours postdialysis and 24-hour area under the curve over minimum inhibitory concentration of ≥400 hours. Therapeutic drug monitoring is necessary to account for residual variability in vancomycin elimination in pediatric patients receiving HD/HDF.

Antihypertensive therapies in moderate or severe aortic stenosis: a systematic review and meta-analysis.

BACKGROUND: Hypertension confers a poor prognosis in moderate or severe aortic stenosis (AS), however, antihypertensive therapy (AHT) is often not prescribed due to the perceived deleterious effects of vasodilation and negative inotropes. OBJECTIVE: To assess the efficacy and safety outcomes of AHT in adults with moderate or severe AS. DESIGN: Systematic review and meta-analysis. DATA SOURCES: The Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE and grey literature were searched without language restrictions up to 9 September 2019. STUDY ELIGIBILITY CRITERIA, APPRAISAL AND SYNTHESIS METHODS: Two independent reviewers performed screening, data extraction and risk of bias assessments from a systematic search of observational studies and randomised controlled trials comparing AHT with a placebo or no AHT in adults with moderate or severe AS for any parameter of efficacy and safety outcomes. Conflicts were resolved by the third reviewer. Meta-analysis with pooled effect sizes using random-effects model, were estimated in R. MAIN OUTCOME MEASURES: Mortality, Left Ventricular (LV) Mass Index, systolic blood pressure, diastolic blood pressure and LV ejection fraction RESULTS: From 3025 publications, 31 studies (26 500 patients) were included in the qualitative synthesis and 24 studies in the meta-analysis. AHT was not associated with mortality when all studies were pooled, but heterogeneity was substantial across studies. The effect size of AHT differed according to drug class. Renin-angiotensin-aldosterone system inhibitors (RAASi) were associated with reduced risk of mortality (Pooled HR 0.58, 95% CI 0.43 to 0.80, p=0.006), The differences in changes of haemodynamic or echocardiographic parameters from baseline with and without AHT did not reach statistical significance. CONCLUSION: AHT appears safe, is well tolerated. RAASi were associated with clinical benefit in patients with moderate or severe AS.

Tolvaptan for Heart Failure in Chronic Kidney Disease Patients: A Systematic Review and Meta-Analysis.

BACKGROUND: Heart failure (HF) is frequently associated with renal impairment. Tolvaptan is reported to be effective in treating congestion in HF without significant electrolyte loss compared to conventional diuretics. However, the safety and efficacy of its use in patients with chronic kidney disease (CKD) is uncertain. This systematic review and meta-analysis evaluated the efficacy and safety outcomes of tolvaptan for HF management in patients with CKD, with a focus at a physiologic basis related to safety. METHODS: We searched for observational studies and randomised clinical trials (RCTs) that assessed the effects of tolvaptan against placebo or standard care in adult patients with HF and CKD. Our protocol was registered with PROSPERO (number CRD42017052775). RESULTS: Seventeen studies were included in the qualitative review and six in the meta-analysis involving 1597 patients. Tolvaptan was associated with an increase in sodium concentration. No significant differences in change of eGFR and serum creatinine were found between tolvaptan and control groups. Urine flow rate appears to increase significantly with tolvaptan compared to baseline (p<0.0001). The meta-analysis demonstrated no heterogeneity between studies but the possibility of publication bias due to incomplete reporting in excluded studies and lack of RCTs. CONCLUSIONS: The safety profile of tolvaptan appears acceptable for patients with HF and CKD. There is evidence for an improvement in serum sodium and reduction in body water without deterioration in renal function. Further research is needed to elucidate the long-term benefits of tolvaptan as an adjunct or alternative to diuretics in such patients.

Xenodiagnosis to detect Borrelia burgdorferi infection: a first-in-human study.

BACKGROUND: Animal studies suggest that Borrelia burgdorferi, the agent of Lyme disease, may persist after antibiotic therapy and can be detected by various means including xenodiagnosis using the natural tick vector (Ixodes scapularis). No convincing evidence exists for the persistence of viable spirochetes after recommended courses of antibiotic therapy in humans. We determined the safety of using I. scapularis larvae for the xenodiagnosis of B. burgdorferi infection in humans. METHODS: Laboratory-reared larval I. scapularis ticks were placed on 36 subjects and allowed to feed to repletion. Ticks were tested for B. burgdorferi by polymerase chain reaction (PCR), culture, and/or isothermal amplification followed by PCR and electrospray ionization mass spectroscopy. In addition, attempts were made to infect immunodeficient mice by tick bite or inoculation of tick contents. Xenodiagnosis was repeated in 7 individuals. RESULTS: Xenodiagnosis was well tolerated with no severe adverse events. The most common adverse event was mild itching at the tick attachment site. Xenodiagnosis was negative in 16 patients with posttreatment Lyme disease syndrome (PTLDS) and/or high C6 antibody levels and in 5 patients after completing antibiotic therapy for erythema migrans. Xenodiagnosis was positive for B. burgdorferi DNA in a patient with erythema migrans early during therapy and in a patient with PTLDS. There is insufficient evidence, however, to conclude that viable spirochetes were present in either patient. CONCLUSIONS: Xenodiagnosis using Ixodes scapularis larvae was safe and well tolerated. Further studies are needed to determine the sensitivity of xenodiagnosis in patients with Lyme disease and the significance of a positive result. Clinical Trials Registration NCT01143558.

Modeling xenobiotic susceptibility to hepatotoxicity using an in vitro oxidative stress inflammation model.

Evidence suggests xenobiotic exposure during periods of inflammation can increase an individual's susceptibility to toxicity. The present study aimed to validate an in-vitro inflammatory model to identify compounds that increase hepatotoxicity during inflammation. Using freshly isolated hepatocytes exposed to a low nontoxic flow of H2O2 using glucose (G) and glucose oxidase (GO) and supplementing it with either peroxidase or Fe(II), the effects of inflammation on 2 classes of drugs known to cause hepatotoxicity were examined: nitroaromatics (nimesulide, nilutamide, flutamide) and aromatic amines (clozapine, thioridazine). Co-incubation with G/GO and the nitroaromatics increased toxicity that was further increased when peroxidase was present. While the aromatic amines did not increase cytotoxicity with G/GO alone, they demonstrated significant increases in cytotoxicity when incubated with peroxidase+G/GO. Liver injury is commonly observed with alcohol abusers; therefore, the effects of inflammation on ethanol, and its metabolite acetaldehyde, were observed. Both ethanol and acetaldehyde increased cytotoxicity, which was further increased when Fe(II) was present. These results implicate H2O2, a cellular mediator of inflammation, as a potential risk factor for hepatotoxicity. A H2O2-enhanced hepatocyte-system in the presence of peroxidase or Fe(II) may prove useful for a more robust screening of xenobiotics for assessing potential toxicity associated with inflammation.

TRIF mediates Toll-like receptor 2-dependent inflammatory responses to Borrelia burgdorferi.

TRIF is an adaptor molecule important in transducing signals from intracellularly signaling Toll-like receptor 3 (TLR3) and TLR4. Recently, TLR2 was found to signal from intracellular compartments. Using a synthetic ligand for TLR2/1 heterodimers, as well as Borrelia burgdorferi, which is a strong activator of TLR2/1, we found that TLR2 signaling can utilize TRIF. Unlike TRIF signaling by other TLRs, TLR2-mediated TRIF signaling is dependent on the presence of another adaptor molecule, MyD88. However, unlike MyD88 deficiency, TRIF deficiency does not result in diminished control of infection with B. burgdorferi in a murine model of disease. This appears to be due to the effects of MyD88 on phagocytosis via scavenger receptors, such as MARCO, which are not affected by the loss of TRIF. In mice, TRIF deficiency did have an effect on the production of inflammatory cytokines, suggesting that regulation of inflammatory cytokines and control of bacterial growth may be uncoupled, in part through transduction of TLR2 signaling through TRIF.

Variation in resistance to multiple pathogen species: anther smuts of Silene uniflora.

The occurrence of multiple pathogen species on a shared host species is unexpected when they exploit the same micro-niche within the host individual. One explanation for such observations is the presence of pathogen-specific resistances segregating within the host population into sites that are differentially occupied by the competing pathogens. This study used experimental inoculations to test whether specific resistances may contribute to the maintenance of two species of anther-smut fungi, Microbotryum silenes-inflatae and Microbotryum lagerheimii, in natural populations of Silene uniflora in England and Wales. Overall, resistance to the two pathogens was strongly positively correlated among host populations and to a lesser degree among host families within populations. A few instances of specific resistance were also observed and confirmed by replicated inoculations. The results suggest that selection for resistance to one pathogen may protect the host from the emergence via host shifts of related pathogen species, and conversely that co-occurrence of two species of pathogens may be dependent on the presence of host genotypes susceptible to both.

The ongoing pursuit of a prophylactic HSV vaccine.

HSV is among the most common human pathogens in the world. It is known to cause painful, persistent skin lesions, while also being the most common cause of fatal non-epidemic encephalitis as well as the leading cause of corneal blindness. The development of prophylactic vaccines could substantially reduce global health problems associated with HSV. So far, HSV vaccine strategies have shown noticeable efficacy in early development during preclinical phases but remained unsuccessful or unproven in human trials. New understanding of how the immune system mounts a defence against HSV offers practical strategies for vaccine development. A number of promising vaccine candidates are currently awaiting clinical development or already undergoing clinical testing. Therefore, this is a suitable time to assess the progress of HSV vaccine development and consider existing challenges and future improvements needed to achieve an effective prophylactic HSV vaccine.

Nod2 suppresses Borrelia burgdorferi mediated murine Lyme arthritis and carditis through the induction of tolerance.

The internalization of Borrelia burgdorferi, the causative agent of Lyme disease, by phagocytes is essential for an effective activation of the immune response to this pathogen. The intracellular, cytosolic receptor Nod2 has been shown to play varying roles in either enhancing or attenuating inflammation in response to different infectious agents. We examined the role of Nod2 in responses to B. burgdorferi. In vitro stimulation of Nod2 deficient bone marrow derived macrophages (BMDM) resulted in decreased induction of multiple cytokines, interferons and interferon regulated genes compared with wild-type cells. However, B. burgdorferi infection of Nod2 deficient mice resulted in increased rather than decreased arthritis and carditis compared to control mice. We explored multiple potential mechanisms for the paradoxical response in in vivo versus in vitro systems and found that prolonged stimulation with a Nod2 ligand, muramyl dipeptide (MDP), resulted in tolerance to stimulation by B. burgdorferi. This tolerance was lost with stimulation of Nod2 deficient cells that cannot respond to MDP. Cytokine patterns in the tolerance model closely paralleled cytokine profiles in infected Nod2 deficient mice. We propose a model where Nod2 has an enhancing role in activating inflammation in early infection, but moderates inflammation after prolonged exposure to the organism through induction of tolerance.