Biology subjects

McNeilly, T. N.

Publications and source records attributed to McNeilly, T. N..

12 recordsLinked to original sources

bioRxiv2024

A secreted helminth microRNA suppresses gastrointestinal cell differentiation required for innate immunity

Pathogens have developed multiple strategies to modulate host immune defense mechanisms. Understanding how this is achieved has potential to inform novel therapeutics for diseases caused by immune dysfunction. Parasitic helminths are masters of immune evasion, via release of secreted products, resulting in chronic infection. Helminths secrete small regulatory microRNA (miRNAs), which can interact with host cells. Here we show that a single parasite miRNA (miR-5352), conserved across gastrointestinal (GI) nematodes, suppresses IL-13-induced GI epithelial cell differentiation and cytokine responses, and promotes stem cell maintenance. Mechanistically, this is achieved through targeted repression of critical host factors, including Klf-4 and the IL-22 receptor, together with modulation of Wnt and Notch signalling pathways. Nematode miR-5352 shows seed sequence conservation with mammalian miR-92a family members, indicating that through convergent evolution, GI nematodes exploit a host miRNA regulatory network to suppress host innate responses, promote tissue regeneration and establish a favourable environment for chronic infection.

microbiology↗

bioRxiv2023

Characterisation of protective vaccine antigens from the thiol-containing components of excretory/secretory material of Ostertagia ostertagi

Previous vaccination trials have demonstrated that thiol proteins affinity purified from Ostertagia ostertagi excretory-secretory products (O. ostertagi ES-thiol) are protective against homologous challenge. Here we have shown that protection induced by this vaccine was consistent across four independent vaccine-challenge experiments. Protection is associated with reduced cumulative faecal egg counts across the duration of the trials, relative to control animals. To better understand the diversity of antigens in O. ostertagi ES-thiol we used high-resolution shotgun proteomics to identify 490 unique proteins in the vaccine preparation. The most numerous ES-thiol proteins, with 91 proteins identified, belong to the sperm-coating protein/Tpx/antigen 5/pathogenesis-related protein 1 (SCP/TAPS) family. This family includes previously identified O. ostertagi vaccine antigens O. ostertagi ASP-1 and ASP-2. The ES-thiol fraction also has numerous proteinases, representing three distinct classes, including: metallo-; aspartyl- and cysteine proteinases. In terms of number of family members, the M12 astacin-like metalloproteinases, with 33 proteins, are the most abundant family in O. ostertagi ES-thiol. The O. ostertagi ES-thiol proteome provides a comprehensive database of proteins present in this vaccine preparation and will guide future vaccine antigen discovery projects.

zoology↗

bioRxiv2023

Tuft cell-derived acetylcholine is an effector of type 2 immunity and directly targets helminth parasites in the gut lumen

Upon parasitic helminth infection, activated intestinal tuft cells secrete IL-25, which initiates a type 2 immune response during which lamina propria ILC2s produce IL-13. This causes epithelial remodelling, including tuft cell hyperplasia with an unknown function. We describe a novel cholinergic effector function of tuft cells, which we show are the only epithelial cells expressing Choline Acetyltransferase (ChAT). During parasite infections, mice with epithelial-specific deletion of ChAT have increased worm burden and faecal egg counts although they are able to mount a comparable type 2 immune response. Mechanistically, IL-13-amplified tuft cells release acetylcholine (ACh) into the gut lumen. We demonstrate a direct effect of ACh on worms, reducing their viability and fecundity via helminth muscarinic ACh receptors, with effects promoted by inhibition of acetylcholinesterase, an helminth-secreted enzyme. Thus, tuft cells are sentinels in naive mice, and their amplification upon helminth infections serves an additional type 2 immune response effector function.

immunology↗

bioRxiv2022

Long-term temporal trends in gastrointestinal parasite infection in wild Soay sheep

Monitoring the prevalence and abundance of parasites over time is important for addressing their potential impact on host life-histories, immunological profiles, and their influence as a selective force. Only long-term ecological studies have the potential to shed light on both the temporal trends in infection prevalence and abundance and the drivers of such trends, because of their ability to dissect drivers that may be confounded over shorter time scales. Despite this, only a relatively small number of such studies exist. Here, we analysed changes in the prevalence and abundance of gastrointestinal parasites in the wild Soay sheep population of St Kilda across 31 years. The host population density has increased across the study, and population density is known to increase parasite transmission, but we found that density and year explained temporal variation in parasite prevalence and abundance independently. Prevalence of both strongyle nematodes and coccidian microparasites increased during the study, and this effect varied between lambs, yearlings and adults. Meanwhile, abundance of strongyles was more strongly linked to host density than to temporal (yearly) dynamics, while abundance of coccidia showed a strong temporal trend without any influence of density. Strikingly, coccidian abundance increased threefold across the course of the study in lambs, while increases in yearlings and adults were negligible. Our decades-long, intensive, individual-based study will enable the role of environmental change and selection pressures in driving these dynamics to be determined, potentially providing unparalleled insight into the drivers of temporal variation in parasite dynamics in the wild. Key findingsO_LIWe studied temporal trends in gastrointestinal parasites of wild sheep over 31 years C_LIO_LIYear and host population density explained temporal variation in parasites independently C_LIO_LIPrevalence of both strongyle nematodes and coccidia varied across the study period C_LIO_LIAbundance of strongyles was more closely linked to host density than year C_LIO_LIAbundance of coccidia increased threefold over time in lambs, but did not vary in adults C_LI

ecology↗

bioRxiv2021

The development of ovine gastric and intestinal organoids for studying ruminant host-pathogen interactions

Gastrointestinal (GI) infections in sheep have significant implications for animal health, welfare and productivity, as well as being a source of zoonotic pathogens. Interactions between pathogens and epithelial cells at the mucosal surface play a key role in determining the outcome of GI infections; however, the inaccessibility of the GI tract in vivo significantly limits the ability to study such interactions in detail. We therefore developed ovine epithelial organoids representing physiologically important gastric and intestinal sites of infection, specifically the abomasum (analogous to the stomach in monogastrics) and ileum. We show that both abomasal and ileal organoids form self-organising three-dimensional structures with a single epithelial layer and a central lumen that are stable in culture over serial passage. We performed RNA-seq analysis on abomasal and ileal tissue from multiple animals and on organoids across multiple passages and show the transcript profile of both abomasal and ileal organoids cultured under identical conditions are reflective of the tissue from which they were derived and that the transcript profile in organoids is stable over at least five serial passages. In addition, we demonstrate that the organoids can be successfully cryopreserved and resuscitated, allowing long-term storage of organoid lines, thereby reducing the number of animals required as a source of tissue. We also report the first published observations of a helminth infecting gastric and intestinal organoids by challenge with the sheep parasitic nematode Teladorsagia circumcincta, demonstrating the utility of these organoids for pathogen co-culture experiments. Finally, the polarity in the abomasal and ileal organoids can be inverted to make the apical surface directly accessible to pathogens or their products, here shown by infection of apical-out organoids with the zoonotic enteric bacterial pathogen Salmonella enterica serovar Typhimurium. In summary, we report a simple and reliable in vitro culture system for generation and maintenance of small ruminant intestinal and gastric organoids. In line with 3Rs principals, use of such organoids will reduce and replace animals in host-pathogen research.

microbiology↗

bioRxiv2021

The right time and place: time- and age-dependent vaccine-enhanced mucosal immunity to parasite infection

Individuals vary broadly in their response to vaccination and subsequent exposure to infection, causing persistence of both infection and transmission. The prevalence of poor vaccine responders hampers the development of vaccines, especially against parasitic helminths. Yet despite having substantial economic and societal impact, the immune mechanisms that underlie such variability, especially at the site of parasite infection, remain poorly understood. Previous trials using a prototype vaccine for the control of the gastric parasitic Teladorsagia circumcincta, one of the highest impact parasites affecting sheep, revealed substantial variation in protection between individuals, which we hypothesised may in part be driven by age at vaccination. Here, to characterise how immunity at the mucosal site of infection developed in vaccinated lambs, we inserted gastric cannulae into the abomasa (true stomachs) of three-month- and six-month-old lambs before vaccination, and performed a longitudinal analysis of their local immune response during subsequent challenge infection. We found that the vaccine caused systemic changes in the baseline immune profile within the abomasum before any parasite exposure had occurred and reduced parasite burden and egg output once lambs were infected, regardless of age. However, age affected how vaccinated lambs responded to subsequent infection across multiple immune pathways, with only a minority of protective immune pathways being independent of age. This resulted in younger lambs being more susceptible to infection regardless of vaccine status. The identification of age-dependent (mostly adaptive) and age-independent (mostly innate) protective immune pathways should help refine the formulation of vaccines against these and potentially other helminth parasites of ruminants, and could indicate specificities of anti-helminth immunity more generally.

immunology↗

bioRxiv2021

Functionally distinct T-helper cell phenotypes predict resistance to different types of parasites in a wild mammal

O_LIThe adaptive immune system is critical to an effective, long-lasting ability to respond to infection in vertebrates and T-helper (Th) cells play a key role in orchestrating the adaptive immune response. Laboratory studies show that functionally distinct Th responses provide protection against different kinds of parasites (i.e., Th1 responses against microparasites and Th2 against macroparasites). C_LIO_LINatural populations must deal with challenges from a wide range of infectious agents and co-infection with different types of parasite is the norm, so different Th responses are likely to play an important and dynamic role in maintaining host health and fitness. However, the relationship between T helper immune phenotypes and infection with different types of parasites remains poorly understood in wild animals. C_LIO_LIIn this study, we characterised variation in functionally distinct Th responses (Th1, Th2, Th17 and regulatory responses) in a wild population of Soay sheep using flow cytometry to detect Th-subset specific transcription factors, and ex vivo lymphocyte stimulation to quantify release of Th-associated cytokines. We specifically tested the prediction that raised Th1 and Th2 responses should predict reduced apicomplexan (coccidian) and helminth (nematode) parasite burdens, respectively. C_LIO_LICell counts of different Th subsets measured by flow cytometry did not vary with age or sex. However, all measures of Th-associated ex vivo cytokine production increased with age, and Th17- and regulatory Th-associated cytokine production increased more rapidly with age in males than females. C_LIO_LIIndependent of age and sex, Th2-associated immune measures negatively predicted gastro-intestinal strongyle nematode faecal egg count, while production of the Th1-associated cytokine IFN-{gamma} negatively predicted coccidian faecal oocyst count. C_LIO_LIOur results provide important support from outside the laboratory that Th1 and Th2 responses confer resistance to different kinds of parasites (micro- and macro-parasites, respectively). They also add to mounting evidence from wild populations that Th1/Th2 trade-offs often observed in controlled laboratory experiments may not readily translate to more complex natural systems. C_LIO_LIOur study illustrates that harnessing more specific reagents and tools from laboratory immunology has the potential to illuminate our understanding of epidemiology and host-parasite co-evolution in the wild. C_LI

ecology↗

bioRxiv2021

Seasonal dynamics and repeatability of gastrointestinal parasite burdens in wild Soay sheep

Seasonality is a ubiquitous feature of wildlife disease ecology, but is determined by a complex interplay of environmental, parasitological and host factors. Gastrointestinal parasites often exhibit strong seasonal dynamics in wild vertebrate populations due to, for example, environmental influences on free-living or vectored life stages, and variation in the physiological and immune status of hosts across their annual cycle. At the same time, wild populations are typically infected with multiple parasites. The seasonal dynamics of co-infecting parasites may differ depending on age and reproductive status, and associations among parasites may be driven by short-term within-individual changes or longer-term interactions that are consistent among hosts. Here, we used faecal samples and egg counts collected repeatedly from individually marked and monitored wild Soay sheep that were part of a long-term study to investigate seasonal dynamics of six gastrointestinal parasite groups (strongyle nematodes, coccidian protozoa, Capillaria, Strongyloides, Nematodirus, and Moniezia). Prevalence and abundance generally tended to be higher spring and summer, and burdens were higher in lambs than adults. Within the highly prevalent strongyle nematode group, we found differences in seasonality of egg counts depending on adult reproductive status. Reproductive ewes had increased counts in spring around the time of birth followed by a drop in abundance in summer, while barren ewes showed little evidence of seasonality. Males showed a sustained rise in egg counts through spring and summer, and sex differences were only strongly apparent in summer. In contrast, in similarly prevalent coccidia we found a peak in faecal oocyst counts in spring but no differences in seasonality among males, barren and pregnant ewes. Using multivariate mixed-effects models, we went on to show that both strongyle and coccidia counts are moderately repeatable across seasons among individuals. We further show that apparent positive correlation between strongyle and coccidia counts was driven by short-term within-individual changes in both parasite burdens rather than long-term among-individual covariation. Overall, our results demonstrate that seasonality varies across demographic and parasite groups and highlight the value of investigating fluctuating susceptibility and exposure over time for understanding epidemiology of a population.

ecology↗

bioRxiv2020

Prophage-dependent recombination drives genome structural variation and phenotypic heterogeneity in Escherichia coli O157:H7

The human zoonotic pathogen Escherichia coli O157 is defined by its extensive prophage repertoire including those that encode Shiga toxin, the factor responsible for inducing life-threatening pathology in humans. As well as introducing genes that can contribute to the virulence of a strain, prophage can enable the generation of large-chromosomal rearrangements (LCRs) by homologous recombination. This work examines the types and frequencies of LCRs across the major lineages of the O157 serogroup and defines the phenotypic consequences of specific structural variants. We demonstrate that LCRs are a major source of genomic variation across all lineages of E. coli O157 and by using both optical mapping and ONT long-read sequencing demonstrate that LCRs are generated in laboratory cultures started from a single colony and particular variants are selected during animal colonisation. LCRs are biased towards the terminus region of the genome and are bounded by specific prophages that share large regions of sequence homology associated with the recombinational activity. RNA transcriptional profiling and phenotyping of specific structural variants indicated that important virulence phenotypes such as Shiga toxin production, type 3 secretion and motility are affected by LCRs. In summary, E. coli O157 has acquired multiple prophage regions over time that act as genome engineers to continually produce structural variants of the genome. This structural variation is a form of epigenetic regulation that generates sub-population phenotypic heterogeneity with important implications for bacterial adaptation and survival. Author SummaryEscherichia coli has an open genome and has acquired genetic information over evolutionary time, often in the form of bacteriophages that integrate into the bacterial genome (prophages). E. coli O157 is a clonal serogroup that is found primarily in ruminants such as cattle but can cause life-threatening infections in humans. E. coli O157 isolates contain multiple prophages including those that encode Shiga-like toxins which are responsible for the more serious disease associated with human infections. We show in this study that many of these prophages exhibit large regions of sequence similarity that allow rearrangements to occur in the genome generating structural variants. These occur routinely during bacterial culture in the laboratory and the variants are detected during animal colonization. The variants generated can give the bacteria altered phenotypes, such as increased motility or toxin production which can be selected in specific environments and therefore represent a highly dynamic mechanism to generate variation in bacterial populations without a change in overall gene content.

microbiology↗

bioRxiv2020

The influence of liver fluke infection on production in sheep and cattle: a meta-analysis

Liver flukes (Fasciola spp) are important parasites of sheep and cattle across the world, causing significant damage to animal health and productivity due to both acute and chronic infection. Many comprehensive reviews have discussed the results of decades of research into the impact of fluke infection on livestock performance traits such as weight gain and milk production. While fluke are considered to be important, there have been no attempts to collate previous research in a quantitative manner, and nor has there been an attempt to determine why some studies find substantial effects of fluke while others conclude that effects of fluke on animal performance are negligible. In this study, we used meta-analysis to provide quantitative estimates of the impact of liver fluke on animal performance, and to identify elements of study design that influence the conclusions of such studies. A literature search provided 233 comparisons of performance in "fluke-infected" and "uninfected" animals. We standardized these data as log response ratios and calculated effect size variances in order to weight studies by their sample size and accuracy of their estimates. We performed multi-level meta-analysis to estimate effects of fluke infection in five traits: daily weight gain (N = 77); live weight (N = 47); carcass weight (N = 84); total weight gain (N = 18) and milk production (N = 6). There were significant negative effects of fluke infection on daily weight gain, live weight and carcass weight (9%, 6% and 0.6% reductions in performance, respectively), but not total weight gain or milk production. We then used mixed-effects meta-analysis to estimate the impact of moderator variables, including host, fluke, and study design factors, on study outcomes. We found that, in general, studies that gave experimental infections found generally larger effects of fluke than observational or drug studies; younger animals were more likely to suffer the effects of fluke infection on daily weight gain; and that effects on live weight increased across the course of an experiment. Our results provide the first quantitative estimate of the importance of liver fluke on performance across studies and highlight the elements of study design that can influence conclusions. Furthermore, our literature search revealed areas of research into liver fluke that could be the subject of greater effort, and types of study that could form the basis of future meta-analyses.

zoology↗

bioRxiv2020

Tolerance of liver fluke infection varies between breeds and producers in Scottish beef cattle

Liver fluke (Fasciola spp.) are important helminth parasites of livestock globally and cause significant reductions in health and productivity of beef cattle. Attempts to control fluke have been thwarted by the difficulty of vaccine design, the evolution of flukicide resistance, and the need to control the intermediate snail host. Mechanisms to reduce the impact of parasites on animal performance have typically focused on promoting host resistance - defined as the ability of the host to kill and remove the parasite from its system - and such strategies include improving protein nutrition or selectively breeding for resistance. Organisms, however, have another broad mechanism for mitigating the impact of parasites: they can show tolerance, defined as the ability to maintain health or performance under increasing parasite burden. Tolerance has been studied in the plant literature for over a century, but there are very few empirical studies of parasite tolerance in livestock. In this study, we used data collected from >90,000 beef cattle to estimate the impact of the severity of liver fluke infection on performance and variation in tolerance of fluke. Severity of liver fluke infection was estimated using liver "fibrosis score" on a scale of 0-3 and performance estimated as (1) age at slaughter and (2) daily dead weight gain. Animals with higher fibrosis scores were slaughtered around two weeks later than animals with no fluke, and gained around 10g less weight per day. There was also considerable variation in these effects of fibrosis score, such that animals from different producers and breeds varied in their tolerance of fluke infection. While breeds did not vary in the association between fibrosis and age at slaughter, there was considerable variation among producers: high fibrosis score delayed slaughter by up to 50 days in some producers, but not at all in others. Meanwhile, there was support for variation in the slope of daily dead weight gain on fibrosis score among both breeds and producers, with some unaffected by high fluke scores and some breeds and producers experiencing a 20g/day lower weight gain under high fluke scores. Our results point to the potential for both environmental and genetic variation in tolerance of liver fluke in cattle, paving the way for quantitative genetic and nutritional research into the feasibility of promoting tolerance as a disease mitigation strategy. ImplicationsPromoting tolerance of disease could help mitigate the impact of disease on livestock productivity, but little research has explored variation in tolerance of livestock diseases or the possibility of promoting tolerance as a mitigation strategy. We used abattoir data to demonstrate that beef cattle vary in their tolerance of fluke infection: while animals from some breeds and some producers experience no impact of fluke on production, others show a large negative effect. Thus, promoting tolerance through management and/or selective breeding could offer a means of reducing the impact of liver fluke on cattle performance.

pathology↗

bioRxiv2019

The genetic architecture of helminth-specific immune responses in a wild population of Soay sheep (Ovis aries)

Host-parasite interactions are powerful drivers of evolutionary and ecological dynamics in natural populations. Variation in immune responses to infection is likely to shape the outcome of these interactions, with important consequences for the fitness of both host and parasite. However, little is known about how genetic variation contributes to variation in immune responses under natural conditions. Here, we examine the genetic architecture of variation in immune traits in the Soay sheep of St Kilda, an unmanaged population of sheep infected with strongyle gastrointestinal nematodes. We assayed IgA, IgE and IgG antibodies against the prevalent nematode Teladorsagia circumcincta in the blood plasma of > 3,000 sheep collected over 26 years. Antibody levels were significantly heritable, ranging from 0.21 to 0.39 in lambs and from 0.23 to 0.57 in adults. IgA levels were strongly associated with a region on chromosome 24 explaining 21.1% and 24.5% of heritable variation in lambs and adults, respectively; this region was adjacent to two candidate loci, the Class II Major Histocompatibility Complex Transactivator (CIITA) and C-Type Lectin Domain Containing 16A (CLEC16A). Lamb IgA levels were also associated with the immunoglobulin heavy constant loci (IGH) complex on chromosome 18. Adult IgE levels and lamb IgG levels were associated with the major histocompatibility complex (MHC) on chromosome 20. This study provides evidence of high heritability of a complex immunological trait under natural conditions and provides the first evidence from a genome-wide study that large effect genes located outside the MHC region exist for immune traits in the wild.\n\nAuthor summaryHost-parasite interactions are powerful drivers of evolutionary and ecological dynamics in natural populations. Variation in immune responses to infection shapes the outcome of these interactions, with important consequences for the ability of the host and parasite to survive and reproduce. However, little is known about how much genes contribute to variation in immune responses under natural conditions. Our study investigates the genetic architecture of variation in three antibody types, IgA, IgE and IgG in a wild population of Soay sheep on the St Kilda archipelago in North-West Scotland. Using data collected over 26 years, we show that antibody levels have a heritable basis in lambs and adults and are stable over lifetime of individuals. We also identify several genomic regions with large effects on immune responses. Our study offers the first insights into the genetic control of immunity in a wild population, which is essential to understand how immune profiles vary in challenging natural conditions and how natural selection maintains genetic variation in complex immune traits.

genetics↗