The power of bioluminescence imaging in understanding host-pathogen interactions

Glow-type conversion and characterization of a minimal luciferase via mutational analyses

Luciferases are widely used as reporter proteins in various fields. Recently, we developed a minimal bright luciferase, picALuc, via partial deletion of the artificial luciferase (ALuc) derived from copepods luciferases. However, the structures of copepod luciferases in the substrate-bound state remain unknown. Moreover, as suggested by structural modeling, picALuc has a larger active site cavity, unlike that in other copepod luciferases. Here, to explore the bioluminescence mechanism of picALuc and its luminescence properties, we conducted multiple mutational analyses, and identified residues and regions important for catalysis and bioluminescence. Mutations of residues likely involved in catalysis (S33, H34, and D55) markedly reduced bioluminescence, whereas that of residue (E50) (near the substrate in the structural model) enhanced luminescence intensity. Furthermore, deletion mutants (Δ70-Δ78) in the loop region (around I73) exhibited longer luminescence lifetimes (~ 30 min) and were reactivated multiple times upon re-addition of the substrate. Due to the high thermostability of picALuc, one of its representative mutant (Δ74), was able to be reused, that is, luminescence recycling, for day-scale time at room temperature. These findings provide important insights into picALuc bioluminescence mechanism and copepod luciferases and may help with sustained observations in a variety of applications.

Activity-based bioluminescence probes for in vivo sensing applications

Bioluminescence imaging is a highly sensitive technique commonly used for various in vivo applications. Recent efforts to expand the utility of this modality have led to the development of a suite of activity-based sensing (ABS) probes for bioluminescence imaging by 'caging' of luciferin and its structural analogs. The ability to selectively detect a given biomarker has presented researchers with many exciting opportunities to study both health and disease states in animal models. Here, we highlight recent (2021-2023) bioluminescence-based ABS probes with an emphasis on probe design and in vivo validation experiments.

Miniaturization of Bright Light-Emitting Luciferase ALuc: picALuc

Luciferases are widely used as sensitive reporters in various fields ranging from basic biology to medical diagnosis, public health, and food inspection. Scientists have isolated novel luciferases from bioluminescent organisms and concentrated on improving their brightness and thermostability. Recently, small bright luciferases such as artificial luciferase (ALuc) (21 kDa), NanoLuc (19 kDa), GLuc (18 kDa), and TurboLuc (16 kDa) have been reported. However, smaller, brighter, and more stable luciferases are desired for further applications. Here, we constructed the smallest and bright mutant of ALuc, named "picALuc" (13 kDa). picALuc retained the luminescence activity of the full-length ALuc; moreover, its brightness and thermostability were at the same levels as NanoLuc. Furthermore, we showed the advantage of picALuc for the bioluminescence resonance energy transfer-based assay due to its smallness. Our development has opened the door for wider and more practical applications of luciferases.

Sensitive sensing of alkaline phosphatase and γ-glutamyltranspeptidase activity for tumor imaging

Mechanism of bioluminescence phenomenon of the probe P-Bz-Luc in the presence of ALP or GGT.

In vivo cell tracking with viral vector mediated genetic labeling

Cell tracking is a useful technique to monitor specific cell populations for their morphology, development, proliferation, migration, interaction, function, and other properties, both in vitro and in vivo. Using different materials and methodologies to label the target cells directly or indirectly, the dynamic biological processes in living organisms can be visualized with appropriate detection techniques. Viruses, with the unique ability to deliver exogenous genes into host cells, have been used as vectors to mediate gene transfer. Genetic labeling of target cells by viral vectors endows the cells to express reporter genes with high efficiency and specificity. In conjunction with corresponding imaging techniques, cells labeled with different genetic reporters mediated by different viral vectors can be monitored across spatial and temporal scales to fulfill various purposes and address different questions. In the present review, we introduce the basic principle of viral vectors in cell tracking and highlight the examples of cell tracking in various research areas.

Why breed disease-resilient livestock, and how?

BACKGROUND

Fighting and controlling epidemic and endemic diseases represents a considerable cost to livestock production. Much research is dedicated to breeding disease resilient livestock, but this is not yet a common objective in practical breeding programs. In this paper, we investigate how future breeding programs may benefit from recent research on disease resilience.

MAIN BODY

We define disease resilience in terms of its component traits resistance (R: the ability of a host animal to limit within-host pathogen load (PL)) and tolerance (T: the ability of an infected host to limit the damage caused by a given PL), and model the host's production performance as a reaction norm on PL, depending on R and T. Based on this, we derive equations for the economic values of resilience and its component traits. A case study on porcine respiratory and reproductive syndrome (PRRS) in pigs illustrates that the economic value of increasing production in infectious conditions through selection for R and T can be more than three times higher than by selection for production in disease-free conditions. Although this reaction norm model of resilience is helpful for quantifying its relationship to its component traits, its parameters are difficult and expensive to quantify. We consider the consequences of ignoring R and T in breeding programs that measure resilience as production in infectious conditions with unknown PL-particularly, the risk that the genetic correlation between R and T is unfavourable (antagonistic) and that a trade-off between them neutralizes the resilience improvement. We describe four approaches to avoid such antagonisms: (1) by producing sufficient PL records to estimate this correlation and check for antagonisms-if found, continue routine PL recording, and if not found, shift to cheaper proxies for PL; (2) by selection on quantitative trait loci (QTL) known to influence both R and T in favourable ways; (3) by rapidly modifying towards near-complete resistance or tolerance, (4) by re-defining resilience as the animal's capacity to resist (or recover from) the perturbation caused by an infection, measured as temporal deviations of production traits in within-host longitudinal data series.

CONCLUSIONS

All four alternatives offer promising options for genetic improvement of disease resilience, and most rely on technological and methodological developments and innovation in automated data generation.

Animal models of Chagas disease and their translational value to drug development

INTRODUCTION

American trypanosomiasis, better known as Chagas disease, is a global public health issue. Current treatments targeting the causative parasite, Trypanosoma cruzi, are limited to two old nitroheterocyclic compounds; new, safer drugs are needed. New tools to identify compounds suitable for parasitological cure in humans have emerged through efforts in drug discovery.

AREAS COVERED

Animal disease models are an integral part of the drug discovery process. There are numerous experimental models of Chagas disease described and in use; rather than going through each of these and their specific features, the authors focus on developments in recent years, in particular the imaging technologies that have dramatically changed the Chagas R&D landscape, and provide a critical view on their value and limitations for moving compounds forward into further development.

EXPERT OPINION

The application of new technological advances to the field of drug development for Chagas disease has led to the implementation of new and robust/standardized in vivo models that contributed to a better understanding of host/parasite interactions. These new models should also build confidence in their translational value for moving compounds forward into clinical development.

Clinical and Preclinical Imaging of Hepatosplenic Schistosomiasis

Schistosomiasis, a neglected tropical disease, is a major cause of chronic morbidity and disability, and premature death. The hepatosplenic form of schistosomiasis is characterized by hepatosplenomegaly, liver fibrosis, portal hypertension, and esophageal varices, whose rupture may cause bleeding and death. We review currently available abdominal imaging modalities and describe their basic principles, strengths, weaknesses, and usefulness in the assessment of hepatosplenic schistosomiasis (HSS). Advanced imaging methods are presented that could be of interest for hepatosplenic schistosomiasis evaluation by yielding morphological, functional, and molecular parameters of disease progression. We also provide a comprehensive view of preclinical imaging studies and current research objectives such as parasite visualization in hosts, follow-up of the host's immune response, and development of noninvasive quantitative methods for liver fibrosis assessment.

Chemiluminescence and Bioluminescence Imaging for Biosensing and Therapy: In Vitro and In Vivo Perspectives

Chemiluminescence (CL) and bioluminescence (BL) imaging technologies, which require no external light source so as to avoid the photobleaching, background interference and autoluminescence, have become powerful tools in biochemical analysis and biomedical science with the development of advanced imaging equipment. CL imaging technology has been widely applied to high-throughput detection of a variety of analytes because of its high sensitivity, high efficiency and high signal-to-noise ratio (SNR). Using luciferase and fluorescent proteins as reporters, various BL imaging systems have been developed innovatively for real-time monitoring of diverse molecules in vivo based on the reaction between luciferin and the substrate. Meanwhile, the kinetics of protein interactions even in deep tissues has been studied by BL imaging. In this review, we summarize in vitro and in vivo applications of CL and BL imaging for biosensing and therapy. We first focus on in vitro CL imaging from the view of improving the sensitivity. Then, in vivo CL applications in cells and tissues based on different CL systems are demonstrated. Subsequently, the recent in vitro and in vivo applications of BL imaging are summarized. Finally, we provide the insight into the development trends and future perspectives of CL and BL imaging technologies.