Biology subjects

Mullan, C.

Publications and source records attributed to Mullan, C..

6 recordsLinked to original sources

bioRxiv2026

Internalized Components of Membrane Attack Complexes Disrupt Proteostasis and Acquire Alarmin-Like Properties

Immune effects of membrane attack complexes (MAC) have been widely attributed to their abilities to cause cell death. Here, we show that the MAC component, C9, forms non-cytolytic aggregates with pro-inflammatory effects. Intracellular aggregates of C9 are detected within inflamed tissues of patients in association with endothelial cell (EC) activation but not increased cell death. We identify NUMBL as a Rab35 effector that directly binds surface-bound C9 to promote C9 internalization and entry into the endolysosomal pathway. Within acidified endolysosomes, C9 forms insoluble aggregates that are targeted for degradative aggrephagy in a process that activates NF-{kappa}B. For C9 aggrephagy to occur, ZFYVE21, a Rab5 effector, complexes with RNF34 to bridge C9 aggregates to LC3B+ aggresome membranes. We detect C9 aggregates in vivo, and we show that a ZFYVE21-RNF34 signaling axis is required for C9 aggrephagy and NF-{kappa}B -dependent EC activation in three separate mouse models. Mice with conditional loss of ZFYVE21 in ECs show reduced aggregraphy, resulting in attenuated systemic inflammation and reduced tissue injury following skin transplantation. Our data show that the C9 component of MACs forms intracellular aggregates with alarmin-like properties.

biochemistry↗

bioRxiv2022

Timing and magnitude of the type-I interferon response are determinants of disease tolerance in arbovirus infection

Infected hosts possess two alternative strategies to protect themselves against the negative impact of virus infections: (i) "resistance", directed to abrogate virus replication, or (ii) "disease tolerance", aimed to avoid organ and tissue damage without overly controlling viral burden. The overall principles governing pathogen resistance are well understood, while less is known about those involved in disease tolerance. Here, we studied bluetongue virus (BTV), the cause of a major disease of ruminants, bluetongue, as a model system to investigate the mechanisms of disease tolerance. BTV induces clinical disease mainly in sheep, while cattle are considered reservoirs of infection, rarely exhibiting clinical symptoms despite sustained viremia. Here, we show that BTV consistently reaches higher titres in ovine primary cells, compared to cells derived from cattle. The variable replication kinetics of BTV in sheep and cattle cells were mostly abolished by abrogating the cell type-I interferon (IFN) response. By screening a library of bovine interferon stimulated genes (ISGs), we identified restriction factors blocking BTV replication, however both sheep and cattle orthologues of these antiviral genes possess anti-BTV properties. Importantly, we demonstrate that BTV induces a faster host cell protein synthesis shutoff in primary sheep cells, compared to cattle cells, which results in an earlier downregulation of antiviral proteins. Moreover, by RNAseq we also show a more pronounced expression of ISGs in BTV infected cattle cells compared to sheep cells. Our data provide a new perspective on how the type-I IFN response in reservoir species can have overall positive effects on both virus and host evolution.

microbiology↗

bioRxiv2022

A human and rhesus macaque interferon-stimulated gene screen reveals ARHGEF3/XPLN as an antiviral gene against hepatitis C virus and other flaviviruses

Natural hepatitis C virus (HCV) infection is restricted to humans whereas in other primates such as rhesus macaques, the virus is non-permissive. To identify human and rhesus macaque genes that differ or share the ability to inhibit HCV replication, we conducted a medium-throughput screen of lentivirus-expressed host genes that disrupt replication of HCV subgenomic replicon RNA expressing secreted Gaussia luciferase. A combined total of >800 interferon-stimulated genes (ISGs) were screened. Our findings confirmed established anti-HCV ISGs, such as IRF1, PKR and DDX60. Novel species-specific inhibitors were also identified and independently validated. Using a cell-based system that recapitulates productive HCV infection, we identified the Rho Guanine Nucleotide Exchange Factor 3 gene (ARHGEF3) from both species as a restriction factor for full-length virus replication. Mechanistically, ARHGEF3-mediated inhibition was ablated by mutating a critical GEF active site residue and deleting the N-terminal portion of the protein. Additionally, replication of two mosquito-borne flaviviruses, yellow fever virus (YFV) and Zika virus (ZIKV), were reduced in ARHGEF3-expressing cell lines compared to controls. In conclusion, we ascribe novel antiviral activity to the cellular gene ARHGEF3 that inhibits replication of HCV and other important human viral pathogens belonging to the Flaviviridae, and is conserved between humans and rhesus macaques.

microbiology↗

bioRxiv2019

Primary care use of laboratory tests in Northern Ireland Western Health and Social Care Trust: a cross-sectional study

ObjectivesTo describe the laboratory test ordering patterns by general practitioners (GPs) in Northern Ireland Western Health and Social Care Trust (WHSCT) and establish demographic and socio-economic associations with test requesting.\n\nDesignCross-sectional study.\n\nSettingWestern Health and Social Care Trust, Northern Ireland\n\nParticipants55 WHSCT general practices requesting laboratory tests in the period from 1 April 2011 to 31 March 2016\n\nOutcomesTo identify the temporal patterns of laboratory test ordering behaviour for 8 commonly requested clinical biochemistry tests/test groups in WHSCT. To analyse the extent of variations in laboratory test requests by GPs and to determine whether these variations can be accounted for by clinical outcomes or geographical, demographic, and socioeconomic characteristics.\n\nResultsWe identified substantial changes in the median number of request rates over five consecutive years of the study period as well as a large variation of adjusted test request rates for individual tests (lowest for electrolyte profiles, liver profiles, and HbA1c and highest for immunoglobulins). No statistically significant relationship between ordering activity and either demographic (age and gender) and socioeconomic factors (deprivation) or Quality and Outcome Framework (QOF) scores was observed. We found that practice setting accounted for some of the between-practice variation in test requesting. Rural practices were characterized by both higher between practice variability and median number of order tests than urban practices at all time points.\n\nConclusionsA large between-practice variation in GP laboratory test requesting appears unrelated to demographic and socioeconomic indicators of the practices or crude clinical outcome indicators, most likely reflects differences in the clinical practice of individuals, potentially amenable to change through clinical interventions.\n\nStrengths and limitations of this studyO_LIThe study provides a comprehensive analysis of temporal changes in laboratory test utilization patterns and establishes the extent of variability in test requesting activity across general practices in Northern Irelands Western Health and Social Care Trust.\nC_LIO_LIThe substantial variation in test ordering, not related to demographic and socioeconomic characteristics of practices, practice location or clinical outcome indicators, may reflect inappropriate laboratory test utilization and hence, suggest a potential for more efficient demand management of laboratory services.\nC_LIO_LIGiven a cohort of general practices within one catchment area, our results provide evidence of differences in behaviour of individual GPs when managing patients with similar clinical symptoms.\nC_LIO_LIFailure to collect and cross-tabulate data on characteristics of general practitioners (GPs), such as GPs age, years of experience, medical training was a study limitation and a missed opportunity in assessing the influence of practitioner factors on the variation in test ordering behaviour.\nC_LI

biochemistry↗

bioRxiv2019

Effects of a demand optimization intervention on laboratory test utilization in primary care

There is evidence of increasing use of laboratory tests with substantial variation between clinical teams which is difficult to justify on clinical grounds. The aim of this project was to assess the effect of a demand optimisation intervention project on laboratory test requesting by general practitioners (GPs) in an area of Northern Ireland supported by the Clinical Chemistry Laboratory service of Western Health and Social Care Trust (WHSCT). The intervention package was developed in conjunction with the Western Local Commissioning Group and consisted of educational initiatives, feedback to 55 individual practices on test request rates with ranking relative to other practices, and a small financial incentive for practices to reflect on their test requesting activity. Overall test utilization rates of profile tests, HbA1c, and PSA one year before, during, and one year after the intervention were measured using laboratory databases of the Altnagelvin Area Hospital, Tyrone County Hospital, and the Erne (South West Acute Hospital. The intervention was associated with mixed effects. First, we observed a reduction of 5.1% in the median profile test request rates and a decrease in their between practice variability. The overall downward trend in variability of profile test request rates was found statistically significant (p = 0.03). Second, we found a significant increase in both the volume (p < 0.0001) and between practice variability (p = 0.0001) of HbA1c requests per patient with diabetes. The increase in HbA1c requests may reflect a more appropriate rate of diabetes monitoring and also the adoption of HbA1c as a diagnostic test. Yet, the subsequent 600% increase in between practice variability of HbA1c ordering rates may imply an inconsistent implementation of recommended guidelines by GPs. Finally, there was a 29.3% increase in the median and 35% increase in between practice variability of request rates for PSA, the reasons for which are unclear.

pathology↗

bioRxiv2018

A laboratory demand optimisation project in primary care

BackgroundThere is evidence of increasing use of laboratory tests with substantial variation between clinical teams which is difficult to justify on clinical grounds. The aim of this project was to assess the effect of a demand optimisation intervention on laboratory test requesting in primary care.\n\nMethodsThe intervention comprised educational initiatives, feedback to 55 individual practices on test request rates with ranking relative to other practices, and a small financial incentive for practices to engage and reflect on their test requesting activity. Data on test request numbers were collected from the laboratory databases for consecutive 12 month periods; pre-intervention 2011-12, intervention 2012-13, 2013-14, 2014-15, and post-intervention 2015-16.\n\nResultsThe intervention was associated with a 3.6% reduction in the mean number of profile test requests between baseline and 2015-16, although this was seen only in rural practices. In both rural and urban practices, there was a significant reduction in-between practice variability in request rates. The mean number of HbA1c requests increased from 1.9 to 3.0 per practice patient with diabetes. Variability in HbA1c request rates increased from 23.8% to 36.6%. At all considered time points, test request rates and variability were higher in rural than in urban areas.\n\nConclusionsThe intervention was associated with a reduction in both the volume and between practice variability of profile test requests, with differences noted between rural and urban practices. The increase in HbA1c requests may reflect a more appropriate rate of diabetes monitoring and also the adoption of HbA1c as a diagnostic test.\n\nStrengths & limitations of the studyO_LIWe assessed the effect of a laboratory demand optimisation intervention both on the value and between GP practice variability in laboratory test requesting.\nC_LIO_LIThe changes in laboratory test requesting were separately evaluated for rural and urban GP practices.\nC_LIO_LIOther factors (GP practice organisation, characteristics of general practitioners) potentially affecting between practice differences in laboratory test ordering were not taken into account due to data unavailability.\nC_LIO_LIThe demand management initiative was not accompanied by the cost-effectiveness analysis.\nC_LIO_LIThe demand optimisation intervention was conducted in a Northern Ireland (NI) Western Health and Social Care Trust and the findings have not been independently replicated in any other NI trusts.\nC_LI

pathology↗