More Like this

1. An Infection-Tolerant Mammalian Reservoir for Several Zoonotic Agents Broadly Counters the Inflammatory Effects of Endotoxin

   https://doi.org/10.1128/mBio.00588-21  

   Balderrama-Gutierrez, Gabriela ; Milovic, Ana ; Cook, Vanessa J. ; Islam, M. Nurul ; Zhang, Youwen ; Kiaris, Hippokratis ; Belisle, John T. ; Mortazavi, Ali ; Barbour, Alan G. ( April 2021 , mBio)

   Miller, Samuel I. (Ed.)

   ABSTRACT Animals that are competent reservoirs of zoonotic pathogens commonly suffer little morbidity from the infections. To investigate mechanisms of this tolerance of infection, we used single-dose lipopolysaccharide (LPS) as an experimental model of inflammation and compared the responses of two rodents: Peromyscus leucopus , the white-footed deermouse and reservoir for the agents of Lyme disease and other zoonoses, and the house mouse Mus musculus . Four hours after injection with LPS or saline, blood, spleen, and liver samples were collected and subjected to transcriptome sequencing (RNA-seq), metabolomics, and specific reverse transcriptase quantitative PCR (RT-qPCR). Differential expression analysis was at the gene, pathway, and network levels. LPS-treated deermice showed signs of sickness similar to those of exposed mice and had similar increases in corticosterone levels and expression of interleukin 6 (IL-6), tumor necrosis factor, IL-1β, and C-reactive protein. By network analysis, the M. musculus response to LPS was characterized as cytokine associated, while the P. leucopus response was dominated by neutrophil activity terms. In addition, dichotomies in the expression levels of arginase 1 and nitric oxide synthase 2 and of IL-10 and IL-12 were consistent with type M1 macrophage responses in mice and type M2 responses in deermice. Analysis of metabolites in plasma and RNA in organs revealed species differences in tryptophan metabolism. Two genes in particular signified the different phenotypes of deermice and mice: the Slpi and Ibsp genes. Key RNA-seq findings for P. leucopus were replicated in older animals, in a systemic bacterial infection, and with cultivated fibroblasts. The findings indicate that P. leucopus possesses several adaptive traits to moderate inflammation in its balancing of infection resistance and tolerance. IMPORTANCE Animals that are natural carriers of pathogens that cause human diseases commonly manifest little or no sickness as a consequence of infection. Examples include the deermouse, Peromyscus leucopus , which is a reservoir for Lyme disease and several other disease agents in North America, and some types of bats, which are carriers of viruses with pathogenicity for humans. Mechanisms of this phenomenon of infection tolerance and entailed trade-off costs are poorly understood. Using a single injection of lipopolysaccharide (LPS) endotoxin as a proxy for infection, we found that deermice differed from the mouse ( Mus musculus ) in responses to LPS in several diverse pathways, including innate immunity, oxidative stress, and metabolism. Features distinguishing the deermice cumulatively would moderate downstream ill effects of LPS. Insights gained from the P. leucopus model in the laboratory have implications for studying infection tolerance in other important reservoir species, including bats and other types of wildlife. 

   more » « less
2. Classification models using circulating neutrophil transcripts can detect unruptured intracranial aneurysm

   https://doi.org/10.1186/s12967-020-02550-2  

   Poppenberg, Kerry E. ; Tutino, Vincent M. ; Li, Lu ; Waqas, Muhammad ; June, Armond ; Chaves, Lee ; Jiang, Kaiyu ; Jarvis, James N. ; Sun, Yijun ; Snyder, Kenneth V. ; et al ( October 2020 , Journal of Translational Medicine)

   Intracranial aneurysms (IAs) are dangerous because of their potential to rupture. We previously found significant RNA expression differences in circulating neutrophils between patients with and without unruptured IAs and trained machine learning models to predict presence of IA using 40 neutrophil transcriptomes. Here, we aim to develop a predictive model for unruptured IA using neutrophil transcriptomes from a larger population and more robust machine learning methods.

   Neutrophil RNA extracted from the blood of 134 patients (55 with IA, 79 IA-free controls) was subjected to next-generation RNA sequencing. In a randomly-selected training cohort (n = 94), the Least Absolute Shrinkage and Selection Operator (LASSO) selected transcripts, from which we constructed prediction models via 4 well-established supervised machine-learning algorithms (K-Nearest Neighbors, Random Forest, and Support Vector Machines with Gaussian and cubic kernels). We tested the models in the remaining samples (n = 40) and assessed model performance by receiver-operating-characteristic (ROC) curves. Real-time quantitative polymerase chain reaction (RT-qPCR) of 9 IA-associated genes was used to verify gene expression in a subset of 49 neutrophil RNA samples. We also examined the potential influence of demographics and comorbidities on model prediction.

   Feature selection using LASSO in the training cohort identified 37 IA-associated transcripts. Models trained using these transcripts had a maximum accuracy of 90% in the testing cohort. The testing performance across all methods had an average area under ROC curve (AUC) = 0.97, an improvement over our previous models. The Random Forest model performed best across both training and testing cohorts. RT-qPCR confirmed expression differences in 7 of 9 genes tested. Gene ontology and IPA network analyses performed on the 37 model genes reflected dysregulated inflammation, cell signaling, and apoptosis processes. In our data, demographics and comorbidities did not affect model performance.

   We improved upon our previous IA prediction models based on circulating neutrophil transcriptomes by increasing sample size and by implementing LASSO and more robust machine learning methods. Future studies are needed to validate these models in larger cohorts and further investigate effect of covariates.

    

   more » « less
3. Structure‐preserving fixation allows scanning electron microscopy to reveal biofilm microstructure and interactions with immune cells

   https://doi.org/10.1111/jmi.13252  

   Wells, Marilyn ; Mikesh, Michelle ; Gordon, Vernita ( December 2023 , Journal of Microscopy)

   Pseudomonas aeruginosais a pathogen that forms robust biofilms which are commonly associated with chronic infections and cannot be successfully cleared by the immune system. Neutrophils, the most common white blood cells, target infections with pathogen‐killing mechanisms that are rendered largely ineffective by the protective physicochemical structure of a biofilm. Visualisation of the complex interactions between immune cells and biofilms will advance understanding of how biofilms evade the immune system and could aid in developing treatment methods that promote immune clearance with minimal harm to the host. Scanning electron microscopy (SEM) distinguishes itself as a powerful, high‐resolution tool for obtaining strikingly clear and detailed topographical images. However, taking full advantage of SEM's potential for high‐resolution imaging requires that the fixation process simultaneously preserve both intricate biofilm architecture and the morphologies and structural signatures characterising neutrophils responses at an infection site. Standard aldehyde‐based fixation techniques result in significant loss of biofilm matrix material and morphologies of responding immune cells, thereby obscuring the details of immune interactions with the biofilm matrix. Here we show an improved fixation technique using the cationic dye alcian blue to preserve and visualise neutrophil interactions with the three‐dimensional architecture ofP. aeruginosabiofilms. We also demonstrate that this technique better preserves structures of biofilms grown from two other bacterial species,Klebsiella pneumoniaeandBurkholderia thailandensis.

    

   more » « less
4. Variability of C‐reactive protein in first‐generation Ecuadorian immigrants living in the United States

   https://doi.org/10.1002/ajhb.23547  

   Shattuck‐Heidorn, Heather ; Eick, Geeta N. ; Kramer, Karen L. ; Sugiyama, Lawrence S. ; Snodgrass, James Josh ; Ellison, Peter T. ( December 2020 , American Journal of Human Biology)

   Establish the variability of C‐reactive protein (CRP) within a population of first‐generation immigrants living in the United States. Prior work has theorized that individuals with high levels of childhood pathogen exposure may have lower CRP levels in adulthood, and therefore that for these individuals, CRP may not be as accurate an index of chronic disease risk related to low‐level inflammation as is presumed based on data from wealthy populations. This potentially has major implications for the interpretation of CRP as a biomarker of chronic inflammation.

   This longitudinal study collected a total of 125 dried blood spot (DBS) samples from 31 participants (median 4 samples each) and CRP levels in these DBS were assayed by enzyme‐linked immunosorbant assay. Surveys were administered to characterize childhood pathogen exposure, and current illness. Variance was estimated using mixed effects regression models.

   On average, participants were adults (mean = 41.9 years old) who had immigrated to the United States nearly 20 years prior to the study and had nearly universally experienced childhood helminth infection and other major pathogen exposures. Median serum‐equivalent CRP was 0.77 mg/L. Individuals reliably differed in subacute CRP levels, and, depending on whether untransformed or log‐transformed CRP was the outcome variable, 45% or 62% of variance in CRP was attributable to between‐individual differences.

   The variability of CRP levels in individuals with relatively high childhood pathogen exposure is comparable to previously reported studies in North America and Europe. However, CRP values are relatively low. CRP is an appropriate measure of subacute inflammation in this sample.

    

   more » « less
5. Disentangling interactions among mercury, immunity and infection in a Neotropical bat community

   https://doi.org/10.1111/1365-2664.13809  

   Becker, Daniel J. ; Speer, Kelly A. ; Korstian, Jennifer M. ; Volokhov, Dmitriy V. ; Droke, Hannah F. ; Brown, Alexis M. ; Baijnauth, Catherene L. ; Padgett‐Stewart, Ticha ; Broders, Hugh G. ; Plowright, Raina K. ; et al ( December 2020 , Journal of Applied Ecology)

   Contaminants such as mercury are pervasive and can have immunosuppressive effects on wildlife. Impaired immunity could be important for forecasting pathogen spillover, as many land‐use changes that generate mercury contamination also bring wildlife into close contact with humans and domestic animals. However, the interactions among contaminants, immunity and infection are difficult to study in natural systems, and empirical tests of possible directional relationships remain rare.

   We capitalized on extreme mercury variation in a diverse bat community in Belize to test association among contaminants, immunity and infection. By comparing a previous dataset of bats sampled in 2014 with new data from 2017, representing a period of rapid agricultural land conversion, we first confirmed bat species more reliant on aquatic prey had higher fur mercury. Bats in the agricultural habitat also had higher mercury in recent years. We then tested covariation between mercury and cellular immunity and determined if such relationships mediated associations between mercury and bacterial pathogens. As bat ecology can dictate exposure to mercury and pathogens, we also assessed species‐specific patterns in mercury–infection relationships.

   Across the bat community, individuals with higher mercury had fewer neutrophils but not lymphocytes, suggesting stronger associations with innate immunity. However, the odds of infection for haemoplasmas andBartonellaspp. were generally lowest in bats with high mercury, and relationships between mercury and immunity did not mediate infection patterns. Mercury also showed species‐ and clade‐specific relationships with infection, being associated with especially low odds for haemoplasmas inPteronotus mesoamericanusandDermanura phaeotis. ForBartonellaspp., mercury was associated with particularly low odds of infection in the genusPteronotusbut high odds in the subfamily Stenodermatinae.

   Synthesis and application. Lower general infection risk in bats with high mercury despite weaker innate defense suggests contaminant‐driven loss of pathogen habitat (i.e. anemia) or vector mortality as possible causes. Greater attention to these potential pathways could help disentangle relationships among contaminants, immunity and infection in anthropogenic habitats and help forecast disease risks. Our results also suggest that contaminants may increase infection risk in some taxa but not others, emphasizing the importance of considering surveillance and management at different phylogenetic scales.

    

   more » « less