Biology subjects

Childs, L.

Publications and source records attributed to Childs, L..

3 recordsLinked to original sources

bioRxiv2025

p1/s1, a 3'-nucleotidase/nuclease, allows Leishmania major to circumvent host innate immune response mechanisms

3-nucleotidases/nucleases, distinct class I nucleases of protozoan parasites, play a pivotal role in extracellular purine salvage. As Leishmania are purine auxotrophs and lack de novo synthesis, ectoenzymes facilitating nucleotide and nucleic acid cleavage are indispensable for subsequent uptake. Employing quantitative proteomics, we identified a class I nuclease p1/s1 cluster in L. major that comprises enzymes exhibiting dual 3-nucleotidase and endonuclease activity. Expression of these enzymes is induced upon miltefosine or staurosporine treatment and was specifically detected in stationary-phase, but not in logarithmic-phase promastigotes. After confirming secretion of p1/s1, ecto-enzymatic activity was detected on parasites and in the culture supernatant. Viable null mutants deficient for the p1/s1 cluster were only obtained when a diCre-based inducible knockout system was applied, whereas direct deletion approaches were lethal. The viable knockout strains exhibited significantly reduced 3-nucleotidase/nuclease activity. Notably, these parasites adapted by compensatory enrichment of various alternative purine salvage proteins at the proteomic level. Furthermore, both enzymatic functions implied mechanisms of host-pathogen interactions to facilitate infection establishment: Utilizing 3-nucleotidase activity, Leishmania generate extracellular adenosine to suppress inflammatory cytokine secretion from macrophages and reduce lymphocyte proliferation in a human primary cell model. The presence of ecto-nucleases also allowed these parasites to degrade and survive neutrophil extracellular traps, a potent first-line innate immune mechanism in pathogen defense. In summary, our integrative approach combining proteomics, immunological and genome editing methods expands current knowledge about Leishmania major 3-nucleotidases/nucleases. By offering new insights into the diverse involvements in host-pathogen interactions, we highlight p1/s1 as pivotal factor during infection and potential drug target.

immunology↗

bioRxiv2025

Infected host competence overshadows heterogeneity in susceptibility in shaping experimental epizootics

The accelerated rate of disease emergence in recent decades underscores the need to understand conditions that promote or dampen epidemics. Theoretical models consistently show that epidemics are smaller in populations with higher among-individual heterogeneity in susceptibility. Experimental tests of these predictions are rare but critical for understanding how heterogeneity in susceptibility shapes epidemics in natural systems. We directly link data-parameterized models from previous dose response experiments in the house finch and Mycoplasma gallisepticum system to experimental epidemics in replicated aviary mesocosm flocks. We manipulated flock-level heterogeneity in susceptibility by seeding epidemics in flocks composed of either pathogen-naive or previously exposed birds, which prior work showed have higher heterogeneity in susceptibility relative to pathogen-naive populations. We tracked epidemics for over two months, combining empirical data and stochastic compartmental models to address how heterogeneity in susceptibility changes epidemic severity. Consistent with previous work, estimates of heterogeneity in susceptibility based on coefficients of variation were higher for flocks given prior pathogen exposure relative to pathogen-naive flocks. However, in contrast with prior work on individually-housed birds which showed relatively homogeneous susceptibility for pathogen-naive birds, the pathogen-naive flocks in this study were better described by heterogeneous, rather than homogenous, models of susceptibility. This suggests that flock-level epidemics captured sources of heterogeneity absent in controlled experiments, such as transmission heterogeneity. Finally, although prior exposure conferred protection from disease at the individual level, we did not detect predicted effects of prior exposure and its associated flock-level heterogeneity on prevalence. However, our ability to detect effects of prior exposure on flock-level prevalence was obscured by unexpected variation in the competence of the initially pathogen-naive index birds that seeded each epidemic. This variation in infectiousness among index birds significantly predicted flock-level prevalence, with low index bird infectiousness contributing to the absence of detectable epidemics in two of the three naive flocks. Our stochastic simulations generated a wide range of prevalence outcomes for small epidemics over the timescales examined, further underscoring the challenges of measuring transmission dynamics in naturalistic settings, where unexpected variation in host traits such as competence can obscure other factors of interest. Open research statementData are not yet provided. Data and code will be permanently and publicly archived in the Virginia Tech Data Repository if the paper is accepted for publication

ecology↗

bioRxiv2024

Influenza A Virus NS1 Limits Recognition of Double-Stranded Transposable Elements by Cytosolic RNA Sensors

Influenza A virus (IAV) infection triggers de-repression of host transposable elements (TEs), which have the potential to form double-stranded (ds)RNAs and stimulate innate antiviral immunity. However, as wild-type IAV is generally a poor inducer of innate immunity, it remains unclear whether de-repressed TEs actually form dsRNAs recognizable by host cytosolic RNA sensors, or whether IAV might antagonize such sensing. Here, we performed strand-specific total RNA-Seq on nuclear and cytosolic fractions from cells infected with wild-type IAV or a recombinant IAV lacking NS1, a viral dsRNA-binding protein. Both infections led to global increases in host TE RNAs with bioinformatic and experimental evidence for double-strandedness. However, only NS1-deficient IAV infection led to significant amounts of TE-dsRNAs translocating to the cytosol, and co-precipitations identified that wild-type NS1 associates with TE-dsRNAs. Furthermore, a functional screen indicated that TE-dsRNAs can be engaged by various host cytosolic RNA sensors, including RIG-I, MDA5, ZBP1, and PKR. Our data reveal the double-stranded nature of infection-triggered host TEs and suggest an NS1-mediated sequestration mechanism to limit their cytosolic abundance and broad activation of diverse sensors.

immunology↗