A fluorogenic, peptide-based probe for the detection of Cathepsin D in macrophages

Cathepsin D is a protease that is an effector in the immune response of macrophages, yet to date, only a limited number of probes have been developed for its detection. Herein, we report a water soluble, highly sensitive, pH insensitive fluorescent probe for the detection of Cathepsin D activity that provides a strong OFF/ON signal upon activation and with bright emission at 515 nm. The probe was synthesised using a combination of solid and solution-phase chemistries, with probe optimisation to increase its water solubility and activation kinetics by addition of a long PEG chain (5 kDa) at the C-terminus. A BODIPY fluorophore allowed detection of Cathepsin D across a wide pH range, important as the protease is active both at the low pH found in lysosomes and also in higher pH phagolysosomes, and in the cytosol. The probe was successfully used to detect Cathepsin D activity in macrophages challenged by exposure to bacteria.

Severe COVID-19 versus multisystem inflammatory syndrome: comparing two critical outcomes of SARS-CoV-2 infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with diverse host response immunodynamics and variable inflammatory manifestations. Several immune-modulating risk factors can contribute to a more severe coronavirus disease 2019 (COVID-19) course with increased morbidity and mortality. The comparatively rare post-infectious multisystem inflammatory syndrome (MIS) can develop in formerly healthy individuals, with accelerated progression to life-threatening illness. A common trajectory of immune dysregulation forms a continuum of the COVID-19 spectrum and MIS; however, severity of COVID-19 or the development of MIS is dependent on distinct aetiological factors that produce variable host inflammatory responses to infection with different spatiotemporal manifestations, a comprehensive understanding of which is necessary to set better targeted therapeutic and preventative strategies for both.

Bacterial and fungal communities in tracheal aspirates of intubated COVID-19 patients: a pilot study

Co-infections with bacterial or fungal pathogens could be associated with severity and outcome of disease in COVID-19 patients. We, therefore, used a 16S and ITS-based sequencing approach to assess the biomass and composition of the bacterial and fungal communities in endotracheal aspirates of intubated COVID-19 patients. Our method combines information on bacterial and fungal biomass with community profiling, anticipating the likelihood of a co-infection is higher with (1) a high bacterial and/or fungal biomass combined with (2) predominance of potentially pathogenic microorganisms. We tested our methods on 42 samples from 30 patients. We observed a clear association between microbial outgrowth (high biomass) and predominance of individual microbial species. Outgrowth of pathogens was in line with the selective pressure of antibiotics received by the patient. We conclude that our approach may help to monitor the presence and predominance of pathogens and therefore the likelihood of co-infections in ventilated patients, which ultimately, may help to guide treatment.

POS1496-HPR HARD TIMES: ADAPTING A FATIGUE MANAGEMENT PROGRAMME IN A PANDEMIC

Background

Fatigue is a symptom of many Rheumatology Conditions (1). Hewlett et al have shown that a Fatigue Management programme (FMP) is effective in reducing fatigue in Rheumatoid Arthritis patients (2). In 2019, a 7-week group-based FMP was developed using a cognitive behavioural approach for Rheumatology patients in NHS Lothian (Scotland). In 2020, due to COVID-19, the in person FMP was adapted for virtual delivery. Referral criteria included Visual Analogue Scale-Fatigue (VAS-F) of ≥6/10 and an inflammatory rheumatic disease diagnosis. The FMP participants recorded Patient Reported Outcome Measures (PROMs) prior to and on completion of the FMP. In August 2021 demand for the FMP far outweighed the capacity of the delivery team and therefore the original 7-week FMP was further adapted to a 4-week programme. This was achieved by focusing on four core elements (i) sleep, (ii) thoughts, emotions and behaviours, (iii) energy conservation, (iv) setbacks.

Objectives

The primary objective was to evaluate whether the 4-week programme produced comparable PROMs results to the 7-week programme. In doing so, the aim was to maintain efficacy of the programme and provide increased capacity by offering more groups in the same timeframe.

Methods

Fatigue Severity Scale (FSS) and VAS-F were selected for comparison between pre and post FMP PROMs results, these being the main indicators of improvement in fatigue management. Fisher’s exact test was used to determine any difference between the PROMs results reported at the end of both programmes. Participants who reported that their PROMs result were the same, worse or who did not respond, were all placed into the category “Other”. The FMP team recorded the average waiting time for those attending each group. The length of the waiting list at any one time was calculated by removing those who were not interested, had been referred elsewhere, or who did not respond to the invitation, from the total number of referrals received by the FMP team.

Results

There was no significant difference in FSS and VAS-F results reported by the participants in both groups at the end of the FMPs as determined by Fisher’s exact test (Table 1). Waiting list times reduced from 24 weeks in August 2021 to 6 weeks in December 2021 as a result of the adaptation of the FMP from a 7-week programme to a 4-week programme (Figure 1).

Table 1.

Reported differences between pre-FMP and post-FMP PROMs.

7 Week FMP (n = 25)4 Week FMP (n = 13)Fischer ExactFSSImproved72%77%p = 1.000Other28%23%VASImproved80%69%p = 0.689Other20%31%Figure 1.

- Review of average waiting times experienced by each group. In August 2021, the decision was made to trial a 4-week FMP to counter large increases in average waiting times.

Conclusion

A 4-week FMP is as effective at improving the management of fatigue in Rheumatology patients as a 7-week FMP and reduces patient waiting times. More research is required to bolster the evidence base to support this novel approach.

References

[1]Overman, C.L., Kool, M.B., Da Silva, J.A.P. et al. The prevalence of severe fatigue in rheumatic diseases: an international study. Clin Rheumatol35, 409–415 (2016).

[2]Hewlett, S., et al., Group cognitive–behavioural programme to reduce the impact of rheumatoid arthritis fatigue: the RAFT RCT with economic and qualitative evaluations. Health Technology Assessment 23(57), 1-130 (2019).

Disclosure of Interests

Joanne Dobson: None declared, Dervil Dockrell: None declared, Kathryn Berg: None declared, Helen Harris Speakers bureau: Galapagos

Prevalence of hypoxaemia in children with pneumonia in low-income and middle-income countries: a systematic review and meta-analysis

Background

Pneumonia accounts for around 15% of all deaths of children younger than 5 years globally. Most happen in resource-constrained settings and are potentially preventable. Hypoxaemia is one of the strongest predictors of these deaths. We present an updated estimate of hypoxaemia prevalence among children with pneumonia in low-income and middle-income countries.

Methods

We conducted a systematic review using the following key concepts “children under five years of age” AND “pneumonia” AND “hypoxaemia” AND “low- and middle-income countries” by searching in 11 bibliographic databases and citation indices. We included all articles published between Nov 1, 2008, and Oct 8, 2021, based on observational studies and control arms of randomised and non-randomised controlled trials. We excluded protocol papers, articles reporting hypoxaemia prevalence based on less than 100 pneumonia cases, and articles published before 2008 from the review. Quality appraisal was done with the Joanna Briggs Institute tools. We reported pooled prevalence of hypoxaemia (SpO₂ <90%) by classification of clinical severity and by clinical settings by use of the random-effects meta-analysis models. We combined our estimate of the pooled prevalence of pneumonia with a previously published estimate of the number of children admitted to hospital due to pneumonia annually to calculate the total annual number of children admitted to hospital with hypoxaemic pneumonia.

Findings

We identified 2825 unique records from the databases, of which 57 studies met the eligibility criteria: 26 from Africa, 23 from Asia, five from South America, and four from multiple continents. The prevalence of hypoxaemia was 31% (95% CI 26–36; 101 775 children) among all children with WHO-classified pneumonia, 41% (33–49; 30 483 children) among those with very severe or severe pneumonia, and 8% (3–16; 2395 children) among those with non-severe pneumonia. The prevalence was much higher in studies conducted in emergency and inpatient settings than in studies conducted in outpatient settings. In 2019, we estimated that over 7 million children (95% CI 5–8 million) were admitted to hospital with hypoxaemic pneumonia. The studies included in this systematic review had high τ² (ie, 0·17), indicating a high level of heterogeneity between studies, and a high I² value (ie, 99·6%), indicating that the heterogeneity was not due to chance. This study is registered with PROSPERO, CRD42019126207.

Interpretation

The high prevalence of hypoxaemia among children with severe pneumonia, particularly among children who have been admitted to hospital, emphasises the importance of overall oxygen security within the health systems of low-income and middle-income countries, particularly in the context of the COVID-19 pandemic. Even among children with non-severe pneumonia that is managed in outpatient and community settings, the high prevalence emphasises the importance of rapid identification of hypoxaemia at the first point of contact and referral for appropriate oxygen therapy.

Funding

UK National Institute for Health Research (Global Health Research Unit on Respiratory Health [RESPIRE]; 16/136/109).

Randomised controlled trial of intravenous nafamostat mesylate in COVID pneumonitis: Phase 1b/2a experimental study to investigate safety, Pharmacokinetics and Pharmacodynamics

BACKGROUND

Many repurposed drugs have progressed rapidly to Phase 2 and 3 trials in COVID19 without characterisation of Pharmacokinetics /Pharmacodynamics including safety data. One such drug is nafamostat mesylate.

METHODS

We present the findings of a phase Ib/IIa open label, platform randomised controlled trial of intravenous nafamostat in hospitalised patients with confirmed COVID-19 pneumonitis. Patients were assigned randomly to standard of care (SoC), nafamostat or an alternative therapy. Nafamostat was administered as an intravenous infusion at a dose of 0.2 mg/kg/h for a maximum of seven days. The analysis population included those who received any dose of the trial drug and all patients randomised to SoC. The primary outcomes of our trial were the safety and tolerability of intravenous nafamostat as an add on therapy for patients hospitalised with COVID-19 pneumonitis.

FINDINGS

Data is reported from 42 patients, 21 of which were randomly assigned to receive intravenous nafamostat. 86% of nafamostat-treated patients experienced at least one AE compared to 57% of the SoC group. The nafamostat group were significantly more likely to experience at least one AE (posterior mean odds ratio 5.17, 95% credible interval (CI) 1.10 - 26.05) and developed significantly higher plasma creatinine levels (posterior mean difference 10.57 micromol/L, 95% CI 2.43-18.92). An average longer hospital stay was observed in nafamostat patients, alongside a lower rate of oxygen free days (rate ratio 0.55-95% CI 0.31-0.99, respectively). There were no other statistically significant differences in endpoints between nafamostat and SoC. PK data demonstrated that intravenous nafamostat was rapidly broken down to inactive metabolites. We observed no significant anticoagulant effects in thromboelastometry.

INTERPRETATION

In hospitalised patients with COVID-19, we did not observe evidence of anti-inflammatory, anticoagulant or antiviral activity with intravenous nafamostat, and there were additional adverse events.

FUNDING

DEFINE was funded by LifeArc (an independent medical research charity) under the STOPCOVID award to the University of Edinburgh. We also thank the Oxford University COVID-19 Research Response Fund (BRD00230).

Research priorities to address the global burden of chronic obstructive pulmonary disease (COPD) in the next decade

Background

The global prevalence of chronic obstructive pulmonary disease (COPD) has increased markedly in recent decades. Given the scarcity of resources available to address global health challenges and respiratory medicine being relatively under-invested in, it is important to define research priorities for COPD globally. In this paper, we aim to identify a ranked set of COPD research priorities that need to be addressed in the next 10 years to substantially reduce the global impact of COPD.

Methods

We adapted the Child Health and Nutrition Research Initiative (CHNRI) methodology to identify global COPD research priorities.

Results

62 experts contributed 230 research ideas, which were scored by 34 researchers according to six pre-defined criteria: answerability, effectiveness, feasibility, deliverability, burden reduction, and equity. The top-ranked research priority was the need for new effective strategies to support smoking cessation. Of the top 20 overall research priorities, six were focused on feasible and cost-effective pulmonary rehabilitation delivery and access, particularly in primary/community care and low-resource settings. Three of the top 10 overall priorities called for research on improved screening and accurate diagnostic methods for COPD in low-resource primary care settings. Further ideas that drew support involved a better understanding of risk factors for COPD, development of effective training programmes for health workers and physicians in low resource settings, and evaluation of novel interventions to encourage physical activity.

Conclusions

The experts agreed that the most pressing feasible research questions to address in the next decade for COPD reduction were on prevention, diagnosis and rehabilitation of COPD, especially in low resource settings. The largest gains should be expected in low- and middle-income countries (LMIC) settings, as the large majority of COPD deaths occur in those settings. Research priorities identified by this systematic international process should inform and motivate policymakers, funders, and researchers to support and conduct research to reduce the global burden of COPD.

Managing pneumonia through facility-based integrated management of childhood management (IMCI) services: an analysis of the service availability and readiness among public health facilities in Bangladesh

BACKGROUND

With an estimated 24,000 deaths per year, pneumonia is the single largest cause of death among young children in Bangladesh, accounting for 18% of all under-5 deaths. The Government of Bangladesh adopted the WHO recommended Integrated Management of Childhood Illness (IMCI)-strategy in 1998 for outpatient management of pneumonia, which was scaled-up nationally by 2014. This paper reports the service availability and readiness related to IMCI-based pneumonia management in Bangladesh. We conducted a secondary analysis of the Bangladesh Health Facility Survey-2017, which was conducted with a nationally representative sample including all administrative divisions and types of health facilities. We limited our analysis to District Hospitals (DHs), Maternal and Child Welfare Centres (MCWCs), Upazila (sub-district) Health Complexes (UHCs), and Union Health and Family Welfare Centres (UH&FWCs), which are mandated to provide IMCI services. Readiness was reported based on 10 items identified by national experts as 'essential' for pneumonia management.

RESULTS

More than 90% of DHs and UHCs, and three-fourths of UH&FWCs and MCWCs provide IMCI-based pneumonia management services. Less than two-third of the staff had ever received IMCI-based pneumonia training. Only one-third of the facilities had a functional ARI timer or a watch able to record seconds on the day of the visit. Pulse oximetry was available in 27% of the district hospitals, 18% of the UHCs and none of the UH&FWCs. Although more than 80% of the facilities had amoxicillin syrup or dispersible tablets, only 16% had injectable gentamicin. IMCI service registers were not available in nearly one-third of the facilities and monthly reporting forms were not available in around 10% of the facilities. Only 18% of facilities had a high-readiness (score 8-10), whereas 20% had a low-readiness (score 0-4). The readiness was significantly poorer among rural and lower level facilities (p < 0.001). Seventy-two percent of the UHCs had availability of one of any of the four oxygen sources (oxygen concentrators, filled oxygen cylinder with flowmeter, filled oxygen cylinder without flowmeter, and oxygen distribution system) followed by DHs (66%) and MCWCs (59%).

CONCLUSION

There are substantial gaps in the readiness related to IMCI-based pneumonia management in public health facilities in Bangladesh. Since pneumonia remains a major cause of child death nationally, Bangladesh should make a substantial effort in programme planning, implementation and monitoring to address these critical gaps to ensure better provision of essential care for children suffering from pneumonia.

A mathematical model shows macrophages delay Staphylococcus aureus replication, but limitations in microbicidal capacity restrict bacterial clearance

S. aureus is a leading cause of bacterial infection. Macrophages, the first line of defence in the human immune response, phagocytose and kill S. aureus but the pathogen can evade these responses. Therefore, the exact role of macrophages is incompletely defined. We develop a mathematical model of macrophage - S. aureus dynamics, built on recent experimental data. We demonstrate that, while macrophages may not clear infection, they significantly delay its growth and potentially buy time for recruitment of further cells. We find that macrophage killing is a major obstacle to controlling infection and ingestion capacity also limits the response. We find bistability such that the infection can be limited at low doses. Our combination of experimental data, mathematical analysis and model fitting provide important insights in to the early stages of S. aureus infections, showing macrophages play an important role limiting bacterial replication but can be overwhelmed with large inocula.

2601. Identification of Staphylococcus aureus Genetic Factors Associatiated with the Subversion of Macrophage Phagosomal Acidification

Background

S. aureus is a major medical pathogen contributing to healthcare-associated costs and mortality. Metastatic S. aureus infection is commonly associated with skin and soft-tissue infections. Macrophages as resident tissue phagocytes are essential for bacterial clearance and effectively phagocytose and kill S. aureus at low inocula. Formation of an intracellular reservoir develops when the capacity for macrophages to eradicate S. aureus is overwhelmed at increased inocula. Phagosomal maturation after bacterial ingestion involves sequential fusion with endosomes and lysosomes, reducing luminal pH, facilitating bacterial degradation. In the context of intracellular S. aureus, incomplete phagosomal maturation is demonstrable with impaired acidification and failure of lysosome fusion. Inhibition of phagosomal maturation is dependent upon bacterial factors as it is reversed in heat-killed bacteria. Intracellular survival of S. aureus is associated with reduced antimicrobial effectivity and increased complications. Within the intracellular environment, persistence of S. aureus is associated with adaptation of gene expression which confers greater resistance to antimicrobial effector mechanisms.

Methods

An ordered mutant library of S. aureus provides the opportunity to give a comprehensive evaluation of gene function. The Nebraska transposon (Tn) mutant library contains 1952 sequence-defined Tn insertion mutants derivative of USA300 LAC S. aureus, each with a single non-essential gene deletion. The mutants were labeled with a fluorescent stain activated at pH < 6 and challenged against differentiated human monocyte-derived macrophages for 4 hours. A high-content microscopy screen was developed to identify the bacterial genes associated with impairment of phagosomal acidification.

Results

The results of the high-throughput screen indicate the global regulators agr and saeR, hemolysin A and catalase are associated with the inhibition of phagosomal acidification.

Conclusion

The burden of S. aureus bacteremia and metastatic disease makes the targeting of intracellular S. aureus essential. Identification of bacterial factors associated with impaired phagosomal acidification and maturation offers targets to limit S. aureus infections.

Disclosures

All authors: No reported disclosures.

407. The Effect of Streptococcus pneumoniae Pneumonia on Atherosclerosis

Background

Clinical studies consistently find an increase in the risk of acute coronary syndrome (ACS) in the weeks following pneumonia, although the mechanisms underlying this finding are unknown. ACS most commonly occurs as a result of thrombosis at the site of ruptured atherosclerotic plaques. We hypothesized that the systemic inflammatory response to pneumococcal pneumonia leads to acute localized inflammatory changes within established atherosclerotic plaques, favoring plaque instability and rupture, thereby resulting in ACS.

Methods

Male ApoE-/- mice, a well-established model of atherosclerosis, were fed an atherogenic diet for 7–8 weeks before intranasal infection with Streptococcus pneumoniae or mock infection. Mice were sacrificed 2 or 8 weeks post-infection. Formalin-fixed, paraffin-embedded aortic sinus plaque sections were analyzed to assess markers of plaque vulnerability to rupture. To characterise post-pneumonic plaque macrophage phenotype, aortic sinus plaque cryosections 2 weeks post pneumonia/mock infection were immunostained for MAC-3 to identify macrophage-rich areas. These plaque regions were collected using laser capture microdissection and RNA extracted for microarray analysis.

Results

S. pneumoniae infection was associated with increased aortic sinus atherosclerotic plaque macrophage content (18.1 vs. 8.0%; P < 0.05) at 2 weeks post infection, but no significant difference in aortic sinus plaque burden, plaque smooth muscle or collagen content. There was no significant difference in any of these plaque vulnerability markers at 8 weeks post infection. Microarray analysis of laser capture micro-dissected plaque macrophages identified downregulation of the expression of three genes coding for specific E3 ubiquitin ligases following pneumonia. Pathway analysis identified a significant perturbation in the ubiquitin proteasome system pathway as a result.

Conclusion

In this murine model, pneumococcal pneumonia resulted in increased atherosclerotic plaque macrophage content, a marker of plaque instability, at 2 weeks post infection. Pneumonia may therefore lead to an increased propensity for atherosclerotic plaques to rupture soon after pneumonia, due to infiltration of macrophages into the plaque.

Disclosures

All authors: No reported disclosures.

Fever in returned travellers presenting in the United Kingdom: recommendations for investigation and initial management

International travel is increasing. Most physicians and general practitioners will encounter returned travellers with fever and the majority of travel-related infection is associated with travel to the tropics. In those returning from the tropics malaria must always be excluded, and HIV considered, from all settings. Common causes of non-malarial fever include from Africa rickettsial diseases, amoebic liver abscess and Katayama syndrome; from South and South East Asia, enteric fever and arboviral infection; from the Middle East, brucellosis and from the Horn of Africa visceral leishmaniasis. Other rare but important diseases from particular geographical areas include leptospirosis, trypanosomiasis and viral haemorrhagic fever. North and South America, Europe and Australia also have infections which are geographically concentrated. Empirical treatment may have to be started based on epidemiological probability of infection whilst waiting for results to return. The evidence base for much of the management of tropical infections is limited. These recommendations provide a pragmatic approach to the initial diagnosis and management of fever in returned travellers, based on evidence where it is available and on consensus of expert opinion where it is not. With early diagnosis and treatment the majority of patients with a potentially fatal infection related to travel will make a rapid and full recovery.

Macrophage-dependent apoptosis of CD4+ T lymphocytes from HIV-infected individuals is mediated by FasL and tumor necrosis factor

Apoptosis of bystander uninfected CD4+ T lymphocytes by neighboring HIV-infected cells is observed in cell culture and in lymphoid tissue of HIV-infected individuals. This study addresses whether antigen-presenting cells such as human macrophages mediate apoptosis of CD4+ T cells from HIV-infected individuals. Uninfected human macrophages, and to a larger degree, HIV-infected macrophages mediate apoptosis of T cells from HIV-infected, but not from uninfected control individuals. This macrophage-dependent killing targets CD4+, but not CD8+ T lymphocytes from HIV-infected individuals, and direct contact between macrophages and lymphocytes is required. Additional analyses indicated that the apoptosis-inducing ligands, FasL and tumor necrosis factor (TNF), mediate this macrophage-induced apoptosis of CD4+ T cells. These results support a role for macrophage-associated FasL and TNF in the selective depletion of CD4+ T cells in HIV-infected individuals.