Optical profiling of macrophages

Macrophages are required to show plasticity in how they react to their microenvironment and orchestrate an inflammatory response. With such an integral role in human immunity, aberrant macrophage function can directly contribute to a variety of pathologies: from driving chronic inflammation to a compromised clearance of invading pathogens. Although there are pharmaceutical opportunities to restore alveolar macrophage function in disease, there still remains a challenge to truly profile their activity in situ. The use of optical endomicroscopy - a non-invasive, fibre-optic imaging platform capable of accessing the alveolar space, may be used in combination with optical probes to profile alveolar macrophage activity in their native environment. Work outlined in this thesis covers the characterisation of a human monocytederived macrophage model phenotype, performed using gold-standard in vitro systems including flow cytometric analysis of receptor expression and phagocytic activity. The work then moves on to explore alternative ways of optically profiling macrophages that may have clinical applications. An optical probe was synthesised to target the mannose receptor, a cell-surface receptor expressed on macrophages, using a camelid nanobody fragment as a targeting ligand. Initial characterisation showed cell-type specificity of the probe towards macrophages. While labelling appeared to be via active internalisation by cells, more evidence is required to determine if this probe interacts specifically with the mannose receptor target. A novel form of optical endomicroscopy was used to explore imaging macrophages, label-free, via their auto-fluorescent emission spectra. This was to distinguish macrophages following internalisation of a fluorescent target, without further labelling required to image negative cells. Initial imaging showed that in vitro monocyte-derived macrophages did not fluoresce brightly enough to be imaged label-free, though it is expected that primary lung macrophages – particularly from COPD patients who smoke – would be sufficiently bright enough to profile with this technique. Ultimately this work will be the foundation to profiling primary alveolar macrophages in health and disease. Using optical endomicroscopic imaging systems with optical probes for markers of cell phenotype, as well as other label-free methods in development, there is potential to profile the activity of alveolar macrophages directly in the alveolar space of the human lung and monitor pharmaceutical effects on their activity

Which traits do observers use to distinguish Batesian mimics from their models?

Batesian mimicry, in which a harmless mimic resembles a more aversive model, can encompass a wide range of morphological traits, but the resemblance is never perfect. Previous studies have used abstract “prey” designs to show that differences in certain traits may not be relevant to mimicry if they are not perceived or recognized by a predator. Here, we extend these results by examining how human “predators” respond to realistic variation in traits of aposematic wasps and their hoverfly mimics. We measured the ability of humans to discriminate between images of wasps and hoverflies in which only certain traits were visible, to determine the contributions of those traits to discrimination decisions. We found that shape is a particularly useful and easily learnt trait for separating the two taxa. Subjects did not successfully discriminate on the basis of abdominal patterns, despite those containing useful information. Color similarity between wasps and hoverflies is relatively high in comparison with other traits, suggesting that selection has acted more strongly on color. Our findings demonstrate the importance of consideration of natural variation in the traits of prey and their salience to predators for understanding the evolution of prey defenses

A cross-sectional study to evaluate second line virological failure and elevated bilirubin as a surrogate for adherence to atazanavir/ritonavir in two urban HIV clinics in Lilongwe, Malawi

BACKGROUND: Malawi's national antiretroviral therapy program provides atazanavir/ritonavir-based second line regimens which cause concentration-dependent rise in indirect bilirubin. We sought to determine if elevated bilirubin, as a surrogate of atazanavir/ritonavir adherence, can aid in the evaluation of second line virological failure in Malawi. METHODS: We conducted a cross-sectional study of HIV-infected patients ≥15 years who were on boosted protease inhibitor-based second line antiretroviral therapy for at least 6 months in two urban HIV clinics in Lilongwe, Malawi. Antiretroviral therapy history and adherence data were extracted from the electronic medical records and blood was drawn for viral load, complete blood count, total bilirubin, and CD4 cell count at a clinic visit. Factors associated with virological failure were assessed using multivariate logistic regression model. RESULTS: Out of 376 patients on second line antiretroviral therapy evaluated, 372 (98.9%) were on atazanavir/ritonavir-based therapy and 142 (37.8%) were male. Mean age was 40.9 years (SD ± 10.1), mean duration on second line antiretroviral therapy was 41.9 months (SD ± 27.6) and 256 patients (68.1%) had elevated bilirubin >1.3 mg/dL. Overall, 35 (9.3%) patients had viral load >1000 copies/ml (virological failure). Among the virologically failing vs. non-failing patients, bilirubin was elevated in 34.3% vs. 72.0% respectively (p < 0.001), although adherence by pill count was similar (62.9% vs. 60.7%, p = 0.804). The odds of virological failure were higher for adults aged 25-40 years (adjusted odds ratio (aOR) 2.5, p = 0.048), those with CD4 cell count <100 (aOR 17.5, p < 0.001), and those with normal bilirubin levels (aOR 5.4, p < 0.001); but were lower for the overweight/obese patients (aOR 0.3, p = 0.026). Poor pill count adherence (aOR 0.7, p = 0.4) and male gender (aOR 1.2, p = 0.698) were not associated with second line virological failure. CONCLUSIONS: Among patients receiving atazanavir/ritonavir-based second line antiretroviral therapy, bilirubin levels better predicted virological failure than pill count adherence. Therefore, strategic use of bilirubin and viral load testing to target adherence counseling and support may be cost-effective in monitoring second line antiretroviral therapy adherence and virological failure. Drug resistance testing targeted for patients with virological failure despite elevated bilirubin levels would facilitate timely switch to third line antiretroviral regimens whenever available

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

A cross-sectional study to evaluate second line virological failure and elevated bilirubin as a surrogate for adherence to atazanavir/ritonavir in two urban HIV clinics in Lilongwe, Malawi

Abstract Background Malawi’s national antiretroviral therapy program provides atazanavir/ritonavir–based second line regimens which cause concentration-dependent rise in indirect bilirubin. We sought to determine if elevated bilirubin, as a surrogate of atazanavir/ritonavir adherence, can aid in the evaluation of second line virological failure in Malawi. Methods We conducted a cross-sectional study of HIV-infected patients ≥15 years who were on boosted protease inhibitor-based second line antiretroviral therapy for at least 6 months in two urban HIV clinics in Lilongwe, Malawi. Antiretroviral therapy history and adherence data were extracted from the electronic medical records and blood was drawn for viral load, complete blood count, total bilirubin, and CD4 cell count at a clinic visit. Factors associated with virological failure were assessed using multivariate logistic regression model. Results Out of 376 patients on second line antiretroviral therapy evaluated, 372 (98.9%) were on atazanavir/ritonavir-based therapy and 142 (37.8%) were male. Mean age was 40.9 years (SD ± 10.1), mean duration on second line antiretroviral therapy was 41.9 months (SD ± 27.6) and 256 patients (68.1%) had elevated bilirubin >1.3 mg/dL. Overall, 35 (9.3%) patients had viral load >1000 copies/ml (virological failure). Among the virologically failing vs. non-failing patients, bilirubin was elevated in 34.3% vs. 72.0% respectively (p < 0.001), although adherence by pill count was similar (62.9% vs. 60.7%, p = 0.804). The odds of virological failure were higher for adults aged 25–40 years (adjusted odds ratio (aOR) 2.5, p = 0.048), those with CD4 cell count <100 (aOR 17.5, p < 0.001), and those with normal bilirubin levels (aOR 5.4, p < 0.001); but were lower for the overweight/obese patients (aOR 0.3, p = 0.026). Poor pill count adherence (aOR 0.7, p = 0.4) and male gender (aOR 1.2, p = 0.698) were not associated with second line virological failure. Conclusions Among patients receiving atazanavir/ritonavir-based second line antiretroviral therapy, bilirubin levels better predicted virological failure than pill count adherence. Therefore, strategic use of bilirubin and viral load testing to target adherence counseling and support may be cost-effective in monitoring second line antiretroviral therapy adherence and virological failure. Drug resistance testing targeted for patients with virological failure despite elevated bilirubin levels would facilitate timely switch to third line antiretroviral regimens whenever available