Animal Models for Drug Development for MRSA

Optimizing a high-sensitivity NanoLuc-based bioluminescence system for in vivo evaluation of antimicrobial treatment

Focal and systemic infections are serious threats to human health. Preclinical models enable the development of new drugs and therapeutic regimens. In vivo, animal bioluminescence (BL) imaging has been used with bacterial reporter strains to evaluate antimicrobial treatment effects. However, high-sensitivity bioluminescent systems are required because of the limited tissue penetration and low brightness of the BL signals of existing approaches. Here, we report that NanoLuc (Nluc) showed better performance than LuxCDABE in bacteria. However, the retention rate of plasmid constructs in bacteria was low. To construct stable Staphylococcus aureus reporter strains, a partner protein enolase (Eno) was identified by screening of S. aureus strain USA300 for fusion expression of Nluc-based luciferases, including Nluc, Teluc, and Antares2. Different substrates, such as hydrofurimazine (HFZ), furimazine (FUR), and diphenylterazine (DTZ), were used to optimize a stable reporter strain/substrate pair for BL imaging. S. aureus USA300/Eno-Antares2/HFZ produced the highest number of photons of orange-red light in vitro and enabled sensitive BL tracking of S. aureus in vivo, with sensitivities of approximately 10 CFU from mouse skin and 750 CFU from mouse kidneys. USA300/Eno-Antares2/HFZ was a powerful combination based on the longitudinal evaluation of the therapeutic efficacy of antibiotics. The optimized S. aureus Eno-Antares2/HFZ pair provides a technological advancement for the in vivo evaluation of antimicrobial treatment.

Antibody production in mice requires neither vitamin D, nor the vitamin D receptor

The vitamin D receptor as well as its ligand have been localized to various immune tissues and cells. These observations have led researchers to hypothesize a role for vitamin D in the immune system. However, a specific role for vitamin D in immunity has yet to be clearly delineated. The work in this report was undertaken to determine if mounting an antibody response is altered in the face of vitamin D-deficiency or when the signaling pathway is eliminated by removal of the nuclear receptor. This investigation provides direct evidence vitamin D is not necessary for producing antibodies, a process paramount for optimal attack against many foreign organisms. The idea that vitamin D plays a significant role in immunity has been proposed repeatedly for many years. To address this important idea we have carried out studies in mice to determine if vitamin D plays a significant role in antibody production. Two animal models were utilized: mice depleted of vitamin D and mice devoid of the vitamin D receptor. Further, a possible role of hypocalcemia resulting from vitamin D deficiency in antibody production was determined. Neither the absence of vitamin D or the vitamin D receptor nor hypocalcemia affected the ability of mice to mount an antibody response to an antigen challenge. Thus, we found no evidence that vitamin D or normal serum calcium is required for this major form of immunity.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): antimicrobial-resistant Staphylococcus aureus in cattle and horses

Staphylococcus aureus (S. aureus) was identified among the most relevant antimicrobial-resistant (AMR) bacteria in the EU for cattle and horses in previous scientific opinions. Thus, it has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on its eligibility to be listed, Annex IV for its categorisation according to disease prevention and control rules as in Article 9, and Article 8 for listing animal species related to the bacterium. The assessment has been performed following a methodology previously published. The outcome is the median of the probability ranges provided by the experts, which indicates whether each criterion is fulfilled (lower bound ≥ 66%) or not (upper bound ≤ 33%), or whether there is uncertainty about fulfilment. Reasoning points are reported for criteria with uncertain outcome. According to the assessment here performed, it is uncertain whether AMR S. aureus can be considered eligible to be listed for Union intervention according to Article 5 of the AHL (60-90% probability). According to the criteria in Annex IV, for the purpose of categorisation related to the level of prevention and control as in Article 9 of the AHL, the AHAW Panel concluded that the bacterium does not meet the criteria in Sections 1, 2 and 4 (Categories A, B and D; 1-5%, 5-10% and 10-33% probability of meeting the criteria, respectively) and the AHAW Panel was uncertain whether it meets the criteria in Sections 3 and 5 (Categories C and E, 33-90% and 60-90% probability of meeting the criteria, respectively). The animal species to be listed for AMR S. aureus according to Article 8 criteria include mainly mammals, birds, reptiles and fish.

The Combination of Cell Cultured Technology and In Silico Model to Inform the Drug Development

Human-derived in vitro models can provide high-throughput efficacy and toxicity data without a species gap in drug development. Challenges are still encountered regarding the full utilisation of massive data in clinical settings. The lack of translated methods hinders the reliable prediction of clinical outcomes. Therefore, in this study, in silico models were proposed to tackle these obstacles from in vitro to in vivo translation, and the current major cell culture methods were introduced, such as human-induced pluripotent stem cells (hiPSCs), 3D cells, organoids, and microphysiological systems (MPS). Furthermore, the role and applications of several in silico models were summarised, including the physiologically based pharmacokinetic model (PBPK), pharmacokinetic/pharmacodynamic model (PK/PD), quantitative systems pharmacology model (QSP), and virtual clinical trials. These credible translation cases will provide templates for subsequent in vitro to in vivo translation. We believe that synergising high-quality in vitro data with existing models can better guide drug development and clinical use.

The effects of baicalin on piglets challenged with Glaesserella parasuis

Glaesserella parasuis (G. parasuis) causes porcine vascular inflammation and damage. Baicalin is reported to have antioxidant and anti-inflammatory functions. However, whether baicalin protects piglets against G. parasuis challenge and the potential protective mechanism have not been investigated. Therefore, in this study, we comprehensively examined the protective efficacy of baicalin in piglets challenged with G. parasuis and the possible protective mechanism. Our results show that baicalin attenuated the release of the inflammation-related cytokines interleukin (IL) 1β, IL6, IL8, IL10, and tumour necrosis factor α (TNF-α) and reduced high mobility group box 1 (HMGB1) production and cell apoptosis in piglets infected with G. parasuis. Baicalin also inhibited the activation of the mitogen-activated protein kinase (MAPK) signalling pathway and protected piglets against G. parasuis challenge. Taken together, our data suggest that baicalin could protect piglets from G. parasuis by reducing HMGB1 release, attenuating cell apoptosis, and inhibiting MAPK signalling activation, thereby alleviating the inflammatory response induced by the bacteria. Our results suggest that baicalin has utility as a novel therapeutic drug to control G. parasuis infection.