Rabbit Lung Research Articles

Protection of Rabbits Against Colonization and Morbidity Associated With Toxigenic Pasteurella multocida by Immunization With Inactivated Heat-labile Toxin.

Pasteurella multocida is a significant cause of morbidity and mortality in rabbits, as well as other species. Some isolates elaborate a heat-labile toxin (PMT) that has been shown to be an important virulence factor. Though previous studies have demonstrated protective immunity can be conferred via immunization of rabbits with heat-inactivated PMT (IPMT), we investigated the ability of immunization to impact colonization of P. multocida. Rabbits were immunized at days 0, 7 and 14 with either phosphate buffered saline (PBS), the mucosal adjuvant cholera toxin (CT), IMPT or IPMT + CT. Male New Zealand white rabbits were used and confirmed to be free of P. multocida prior to experimentation. Serum IgG and nasal lavage fluid IgA responses directed against PMT were found in rabbits immunized with IPMT, with or without CT, but not in those immunized with only PBS or CT; and the addition of CT to IPMT enhanced the response. Significantly more P. multocida CFUs (p≤0.05) were cultured from the lungs of rabbits immunized with IPMT, with or without CT, compared to those administered only PBS or CT, although no differences were observed in nasal lavage fluid samples. Further, immunization IPMT, with or without CT, conferred protection against pleuritis and pneumonia. PMT, in addition to its role as a virulence factor, may serve as a colonization factor for P. multocida in the lungs of rabbits.

Mathematical modeling suggests heterogeneous replication of Mycobacterium tuberculosis in rabbits.

How quickly Mycobacterium tuberculosis ( Mtb ) replicates and dies in lungs of infected individuals is likely to determine the outcome of the infection - either control/clearance of the bacteria by the host immune response or progression to active disease, tuberculosis ( TB ). And yet, only a few studies, primarily in mice, rigorously estimated the rates of Mtb replication and death during an in vivo infection. We infected rabbits with a novel clinical isolate of Mtb carrying an unstable, "replication clock" plasmid and followed the dynamics of bacteria over time. Interestingly, previous methods developed to estimate Mtb replication and death rates using similar data for Mtb infection of mice failed to describe our novel data on Mtb dynamics in rabbits; we showed that heterogeneous dynamics of Mtb in semi-independent subpopulations in lungs of Mtb-infected rabbits may be one explanation of this failure of the method. Our results highlight potential differences in Mtb dynamics in different mammalian hosts and suggest ways to evaluate heterogeneity of Mtb replication and death rates in vivo.

Differential requirement of formyl peptide receptor 1 in macrophages and neutrophils in the host defense against Mycobacterium tuberculosis Infection

Formyl peptide receptors (FPR), part of the G-protein coupled receptor superfamily, are pivotal in directing phagocyte migration towards chemotactic signals from bacteria and host tissues. Although their roles in acute bacterial infections are well-documented, their involvement in immunity against tuberculosis (TB) remains unexplored. Here, we investigate the functions of Fpr1 and Fpr2 in defense against Mycobacterium tuberculosis (Mtb), the causative agent of TB. Elevated levels of Fpr1 and Fpr2 were found in the lungs of mice, rabbits and peripheral blood of humans infected with Mtb, suggesting a crucial role in the immune response. The effects of Fpr1 and Fpr2 deletion on bacterial load, lung damage, and cellular inflammation were assessed in a murine TB model utilizing hypervirulent strain of Mtb from the W-Beijing lineage. While Fpr2 deletion had no impact on disease outcome, Fpr1-deficient mice demonstrated improved bacterial control, especially by macrophages. Bone marrow-derived macrophages from these Fpr1−/− mice exhibited an enhanced ability to contain bacterial growth over time. Contrarily, treating genetically susceptible mice with Fpr1-specific inhibitors caused impaired early bacterial control, corresponding with increased Mtb persistence in necrotic neutrophils. Furthermore, ex vivo assays revealed that Fpr1−/− neutrophils were unable to restrain Mtb growth, indicating a differential function of Fpr1 among myeloid cells. These findings highlight the distinct and complex roles of Fpr1 in myeloid cell-mediated immunity against Mtb infection, underscoring the need for further research into these mechanisms for a better understanding of TB immunity.

Acute-phase plasma proteomics of rabbit lung VX2 tumors treated by image-guided microwave ablation.

To explore the plasma proteomic changes of rabbit lung VX2 tumors treated by microwave ablation, and to explore the molecular pathway mechanisms that may be involved. New Zealand white rabbits were inoculated with VX2 tumor cell suspension in the right lower lung and treated with microwave ablation after 2-3 weeks of tumor formation. Blood was collected at 5 time points (TP1~TP5) before and after ablation by cardiac blood sampling and pre-treated before proteomic analysis. The plasma proteome was analyzed by Data-Independent Acquisition (DIA). Different molecular pathways were activated at different time points:(i) TP1vsTP2: more proteins were down-regulated and enrichment analysis showed that the proteasome pathway was activated. The abnormal protein folding process involved in this pathway is closely related to the process of tumor development. (ii) TP2vsTP3: more proteins were up-regulated although the number of differentially differentiated proteins was lower and enrichment analysis showed that the phagosome pathway was activated. After microwave ablation inactivates tumor cells, it activates the phagosomal pathway for immune clearance of necrotic tumor tissue. (iii) TP3vsTP4: more down-regulated proteins, enrichment analysis showed that cysteine and methionine metabolism pathway was activated. Decreased metabolism of these amino acids suggests that cancer progression may be blocked after microwave ablation therapy. (iv) TP4vsTP5: the number of differential proteins was less and more down-regulated proteins, enrichment analysis showed that glutathione metabolism and metabolism of xenobiotics by cytochrome P450 pathway were activated. The down-regulated proteins in this pathway may suggest that microwave ablation may have reduced resistance to certain chemotherapeutic agents following. In the process of lung cancer treatment by microwave ablation, the changes of proteins on the possible molecular pathways at each time point are related to lung cancer, and not only involve some simple inflammatory reactions, and some of the proteins released by destroying the tumor cells can be used as possible drug binding sites and reduce drug resistance.

Developing Hyperpolarized Butane Gas for Ventilation Lung Imaging.

NMR hyperpolarization dramatically improves the detection sensitivity of magnetic resonance through the increase in nuclear spin polarization. Because of the sensitivity increase by several orders of magnitude, additional applications have been unlocked, including imaging of gases in physiologically relevant conditions. Hyperpolarized 129Xe gas recently received FDA approval as the first inhalable gaseous MRI contrast agent for clinical functional lung imaging of a wide range of pulmonary diseases. However, production and utilization of hyperpolarized 129Xe gas faces a number of translational challenges including the high cost and complexity of contrast agent production and imaging using proton-only (i.e., conventional) clinical MRI scanners, which are typically not suited to scan 129Xe nuclei. As a solution to circumvent the translational challenges of hyperpolarized 129Xe, we have recently demonstrated the feasibility of a simple and cheap process for production of proton-hyperpolarized propane gas contrast agent using ultralow-cost disposable production equipment and demonstrated the feasibility of lung ventilation imaging using hyperpolarized propane gas in excised pig lungs. However, previous pilot studies have concluded that the hyperpolarized state of propane gas decays very fast with an exponential decay T 1 constant of ∼0.8 s at 1 bar (physiologically relevant pressure); moreover, the previously reported production rates were too slow for potential clinical utilization. Here, we investigate the feasibility of high-capacity production of hyperpolarized butane gas via heterogeneous parahydrogen-induced polarization using Rh nanoparticle-based catalyst utilizing butene gas as a precursor for parahydrogen pairwise addition. We demonstrate a remarkable result: the lifetime of the hyperpolarized state can be nearly doubled compared to that of propane (T 1 of ∼1.6 s and long-lived spin-state T S of ∼3.8 s at clinically relevant 1 bar pressure). Moreover, we demonstrate a production speed of up to 0.7 standard liters of hyperpolarized gas per second. These two synergistic developments pave the way to biomedical utilization of proton-hyperpolarized gas media for ventilation imaging. Indeed, here we demonstrate the feasibility of phantom imaging of hyperpolarized butane gas in Tedlar bags and also the feasibility of subsecond 2D ventilation gas imaging in excised rabbit lungs with 1.6 × 1.6 mm2 in-plane resolution using a clinical MRI scanner. The demonstrated results have the potential to revolutionize functional pulmonary imaging with a simple and inexpensive on-demand production of proton-hyperpolarized gas contrast media, followed by visualization on virtually any MRI scanner, including emerging bedside low-field MRI scanner technology.

Neisseria leonii sp. nov., isolated from the nose, lung, and liver of rabbits.

A taxogenomic study of three strains (3986T, 51.81, and JF 2415) isolated from rabbits between 1972 and 2000 led to the description of a new Neisseria species. The highest sequence similarity of the 16S rRNA gene was found to Neisseria animalis NCTC 10212T (96.7 %). The 16S rRNA gene similarity above 99 % and average nucleotide identity (ANI) values above 96 % among the strains, indicated that they belong to the same species. At the same time, the strains shared ANI values below 81 % and dDDH values below 24 % with all described Neisseria species. In the bac120 gene phylogenetic tree, the three strains clustered near Neisseria elongata and Neisseria bacilliformis in the Neisseria clade. However, the Neisseria clade is not monophyletic, and includes the type strains of Morococcus cerebrosus, Bergeriella denitrificans, Kingella potus, Uruburuella suis, and Uruburuella testudinis. Neisseria shayeganii clustered outside the clade with members of the genus Eikenella. Amino acid identity (AAI) values were calculated, and a threshold of 71 % was used to circumscribe the genus Neisseria. According to this proposed AAI threshold, strains 3986T, 51.81, and JF 2415 were placed within the genus Neisseria. The cells of the three strains were Gram-stain-negative diplococcobacilli and non-motile. Optimal growth on trypticase soy agar occurred at 37 °C and pH 8.5 in aerobic conditions. Notably, all strains exhibited indole production in the API-NH test, which is atypical for Neisseria and the family Neisseriaceae. The strains exhibited a common set of 68 peaks in their MALDI-TOF MS profiles, facilitating the swift and accurate identification of this species. Based on genotypic and phenotypic data, it is proposed that strains 3986T, 51.81, and JF 2415 represent a novel species within the genus Neisseria, for which the name Neisseria leonii sp. nov. is proposed (type strain 3986T=R726T=CIP 109994T=LMG 32907T).

Effects of Ranolazine and Ivabradine on Pulmonary Microhemodynamics in Experimental Model of Pulmonary Thromboembolism.

We studied changes of pulmonary microhemodynamics when modeling pulmonary artery thromboembolism on perfused isolated rabbit lungs after pretreatment with ranolazine and ivabradine. The increase in pulmonary artery pressure, pulmonary vascular resistance, and pre- and postcapillary resistance was less pronounced than in control animals, but was close to that in case of pulmonary thromboembolism after pretreatment with voltage-gated Na+ channel blockers lidocaine and ropivacaine. The increase of capillary filtration coefficient inversely correlated with values of capillary hydrostatic pressure. Thus, ranolazine and ivabradine exhibit the properties of voltage-gated Na+ channel blockers mainly in smooth muscles of pulmonary arterial vessels and promote the decrease in endothelial permeability.

Differential requirement of Formyl Peptide Receptor 1 in macrophages and neutrophils in the host defense against Mycobacterium tuberculosis Infection.

Formyl peptide receptors (FPR), part of the G-protein coupled receptor superfamily, are pivotal in directing phagocyte migration towards chemotactic signals from bacteria and host tissues. Although their roles in acute bacterial infections are well-documented, their involvement in immunity against tuberculosis (TB) remains unexplored. This study investigates the functions of Fpr1 and Fpr2 in defense against Mycobacterium tuberculosis (Mtb), the causative agent of TB. Elevated levels of Fpr1 and Fpr2 were found in the lungs of mice, rabbits and peripheral blood of humans infected with Mtb, suggesting a crucial role in the immune response. The effects of Fpr1 and Fpr2 deletion on bacterial load, lung damage, and cellular inflammation were assessed using a TB model of hypervirulent strain of Mtb from the W-Beijing lineage. While Fpr2 deletion showed no impact on disease outcome, Fpr1-deficient mice demonstrated improved bacterial control, especially by macrophages. Bone marrow-derived macrophages from these Fpr1 -/- mice exhibited an enhanced ability to contain bacterial growth over time. Contrarily, treating genetically susceptible mice with Fpr1-specific inhibitors caused impaired early bacterial control, corresponding with increased bacterial persistence in necrotic neutrophils. Furthermore, ex vivo assays revealed that Fpr1 -/- neutrophils were unable to restrain Mtb growth, indicating a differential function of Fpr1 among myeloid cells. These findings highlight the distinct and complex roles of Fpr1 in myeloid cell-mediated immunity against Mtb infection, underscoring the need for further research into these mechanisms for a better understanding of TB immunity.

Novel locally nebulized indocyanine green for simultaneous identification of tumor margin and intersegmental plane.

Segmentectomy, recommended for early-stage lung cancer or compromised lung function, demands precise tumor detection and intersegmental plane identification. While indocyanine green (ICG) commonly aids in these aspects using near-infrared imaging, its separate administrations through different routes and times can lead to complications and patient anxiety. This study aims to develop a lung-specific delivery method by nebulizing low-dose ICG to targeted lung segments, allowing simultaneous detection of lung tumors and intersegmental planes across diverse animal models. To optimizing the dose of ICG for lung tumor and interlobar fissure detection, different doses of ICG (0.25, 0.1, and 0.05mg/kg) were nebulized to rabbit lung tumor models. The distribution of locally nebulized ICG in targeted segments was studied to evaluate the feasibility of detecting lung tumor and intersegmental planes in canine lung pseudotumor models. Near-infrared fluorescence imaging demonstrated clear visualization of lung tumor margin and interlobar fissure using local nebulization of 0.1mg/kg ICG for only 4min during surgery in the rabbit models. In the canine model, the local nebulization of 0.05mg/kg of ICG into the target segment enabled clear visualization of pseudotumor and intersegmental planes for 30min. This innovative approach achieves a reduction in ICG dose and prolonged the visualization time of the intersegmental plane and effectively eliminates the need for the hurried marking of tumors and intersegmental planes. The authors anticipate that lung-specific delivery of ICG will prove valuable for image-guided limited resection of lung tumors in clinical practice.

Formyl Peptide Receptor 1 regulates early control of Mycobacterium tuberculosis infection.

Abstract Formyl peptide receptors (FPR) are playing a pivotal role in phagocyte migration in response to bacterial and host-derived chemoattractants. Despite their established roles, their involvement in immunity to tuberculosis remains unexplored. In this study, we investigated the contributions of Fpr1 and Fpr2 to host defense against Mycobacterium tuberculosis (Mtb) infection. Fpr1 and Fpr2 expression increased in the lungs of rabbits as early as 3 hours and remained elevated during the chronic phase of infection. Additionally, these receptors were increasingly expressed in neutrophils of mice highly susceptible to infection, implying a potential role in the host response to Mtb. We assessed bacterial burden, lung damage, and cellular inflammation following infection of Fpr1-/- and Fpr2-/- mice with a hypervirulent W-Beijing lineage strain of Mtb. While Fpr2 deletion exhibited no discernible impact on host resistance, Fpr1 deficiency compromised bacterial control in the lungs. This effect was particularly pronounced in genetically susceptible mice treated with Fpr1-specific inhibitors. In vitro experiments demonstrated that bone marrow–derived neutrophils and macrophages lacking Fpr1 were incapable of controlling intracellular Mtb growth. Collectively, our findings underscore the differential roles of Fpr1 and Fpr2 in the host defense against Mtb infection, highlighting Fpr1 as a potential therapeutic target for enhancing immune responses against tuberculosis.

Toward Lung Ventilation Imaging Using Hyperpolarized Diethyl Ether Gas Contrast Agent.

Hyperpolarized 129Xe gas was FDA-approved as an inhalable contrast agent for magnetic resonance imaging of a wide range of pulmonary diseases in December 2022. Despite the remarkable success in clinical research settings, the widespread clinical translation of HP 129Xe gas faces two critical challenges: the high cost of the relatively low-throughput hyperpolarization equipment and the lack of 129Xe imaging capability on clinical MRI scanners, which have narrow-bandwidth electronics designed only for proton (1H) imaging. To solve this translational grand challenge of gaseous hyperpolarized MRI contrast agents, here we demonstrate the utility of batch-mode production of proton-hyperpolarized diethyl ether gas via heterogeneous pairwise addition of parahydrogen to ethyl vinyl ether. An approximately 0.1-liter bolus of hyperpolarized diethyl ether gas was produced in 1 second and injected in excised rabbit lungs. Lung ventilation imaging was performed using sub-second 2D MRI with up to 2×2 mm2 in-plane resolution using a clinical 0.35 T MRI scanner without any modifications. This feasibility demonstration paves the way for the use of inhalable diethyl ether as a gaseous contrast agent for pulmonary MRI applications using any clinical MRI scanner.

Analysis of the experimental absorption spectrum of the rabbit lung and identification of its components.

The broadband absorption coefficient spectrum of the rabbit lung presents some particular characteristics that allow the identification of the chromophores in this tissue. By performing a weighted combination of the absorption spectra of water, hemoglobin, DNA, proteins and the pigments melanin and lipofuscin, it was possible to obtain a good match to the experimental absorption spectrum of the lung. Such reconstruction provided reasonable information about the contents of the tissue components in the lung tissue, and allowed to identify a similar accumulation of melanin and lipofuscin.

Apoptosis activation during Lagovirus europaeus/GI.2 infection in rabbits

Rabbit Haemorrhagic Disease (RHD) is a severe disease caused by Lagovirus europaeus/GI.1 and GI.2. Immunological processes such as apoptosis are important factors involved in the pathogenesis of Rabbit Haemorrhagic Disease (RHD). The process of programmed cell death has been quite well characterized in infection with GI.1 strains, but apoptosis in infection with GI.2 strains has not been widely studied. This is particularly important as several studies have shown that significant differences in the host immune response are observed during infection with different strains of Lagovirus europaeus. In this study, we analyzed the gene expression, protein levels and activity of key apoptotic cell death factors in the spleen, kidney, lung, and heart of rabbits. As a result, we showed that there is a significant increase in caspase-3, Bax, Bcl2 and Bax/Bcl2 mRNA gene expression ratio in organs of infected animals. Our results show also increased levels of cleaved caspase-3, caspase-6 and PARP. Moreover, significant activity of caspase-3 was also detected. Our results indicate that caspase-3, caspase-6 and genes coding Bcl2 family proteins play a key role in the apoptotic response in Lagovirus europaeus/GI.2 infection in organs that are not the target of virus replication.

Rapid lung ventilation MRI using parahydrogen-induced polarization of propane gas.

Proton-hyperpolarized contrast agents are attractive because they can be imaged on virtually any clinical MRI scanner, which is typically equipped to scan only protons rather than heteronuclei (i.e., anything besides protons, e.g., 13C, 15N, 129Xe, 23Na, etc.). Even though the lifetime of the proton spin hyperpolarization is only a few seconds, it is sufficient for inhalation and scanning of proton-hyperpolarized gas media. We demonstrate the utility of producing hyperpolarized propane gas via heterogeneous parahydrogen-induced polarization for the purpose of ventilation imaging in an excised rabbit lung model. The magnetization of protons in hyperpolarized propane gas is similar to that of tissue water protons, making it possible to rapidly perform lung ventilation imaging with a 0.35 T clinical MRI scanner. Here, we demonstrate the feasibility of rapid (2 s) lung ventilation MRI in excised rabbit lungs using hyperpolarized propane gas with a 1 × 1 mm2 pixel size using a 50 mm slice thickness, and a 1.7 × 1.7 mm2 pixel size using a 9 mm slice thickness.

45 Efficacy of the lysin exebacase in addition to vancomycin in a rabbit lung infection model caused by a cystic fibrosis methicillin-resistant Staphylococcus aureus clinical isolate

45 Efficacy of the lysin exebacase in addition to vancomycin in a rabbit lung infection model caused by a cystic fibrosis methicillin-resistant Staphylococcus aureus clinical isolate

Molecular detection and pathological modifications of Klebsiella pneumoniae in trachea and lung of rabbits after infected by intranasal instillation route

Klebsiella pneumoniae, one of the more critical zoonotic pathogenic bacteria, causes many diseases, including pneumonia, urinary tract infections, bloodstream ‎infections, and sepsis. This study aimed to insulate K. pneumoniae from sheep ‎urine and identify it by microbiological method on MacConkey agar and confirmed with ‎‎16S-rRNA sequencing analysis, then study the pathological changes ‎of bacteria in the trachea and lung of rabbits after infected by intranasal instillation ‎route. A total of 24 adult healthy local male rabbits were divided randomly into 2 groups: in the control group, eight animals received 50 µL phosphate buffer saline via intranasal instillation. In contrast, sixteen animals received intranasally a single dose of K. pneumonia at 106 CFU/50 µL PBS/animal in the infected group. Two animals from the infected group and one from the control group were sacrificed at ‎‎3 hours, 6 hours, 12 hours, 24 hours, 3 days, 7 days, and 16 days post-infection. A postmortem examination was performed, and any gross lesions were reported. Trachea and lung specimens were then collected and fixed in 10% formalin. The results of the bacterial ‎examination growing on the MacConkey media agreed with the results of molecular ‎confirmed by 16S rRNA sequencing analysis. Macroscopic results highlighted severe lung congestion and white spot areas in the lung tissue. Microscopic ‎changes in the trachea are characterized by acute tracheitis with infiltration of inflammatory cells ‎within a fibro-cartilaginous layer, with sticky exudate consisting of fluid collection and ‎inflammatory cells in the tracheal lumen. as well as bleeding and aggregation edematous ‎fluid recorded in alveolar lumen, with alveolar epithelial sloughing, interstitial pneumonia, ‎bronchiectasis, and bronchiolitis with emphysema. The conclusion of this study could be ‎summarized by addressing the severity of infection at several different times from the Intranasal ‎instillation route with the rapid and dangerous ascending progression of pathological lesions ‎in tracheal and lung disease post-infected rabbits via Intranasal instillation‎. Keywords: Klebsiella pneumoniae,16S-rRNA , trachea, lung, rabbit

Digital PCR (dPCR) Quantification of miR-155-5p as a Potential Candidate for a Tissue Biomarker of Inflammation in Rabbits Infected with Lagovirus europaeus/Rabbit Hemorrhagic Disease Virus (RHDV)

MicroRNAs (miRNAs, miRs) are a group of small, 17–25 nucleotide, non-coding RNA sequences that, in their mature form, regulate gene expression at the post-transcriptional level. They participate in many physiological and pathological processes in both humans and animals. One such process is viral infection, in which miR-155 participates in innate and adaptive immune responses to a broad range of inflammatory mediators. Recently, the study of microRNA has become an interesting field of research as a potential candidate for biomarkers for various processes and disease. To use miRNAs as potential biomarkers of inflammation in viral diseases of animals and humans, it is necessary to improve their detection and quantification. In a previous study, using reverse transcription real-time quantitative PCR (RT-qPCR), we showed that the expression of ocu-miR-155-5p in liver tissue was significantly higher in rabbits infected with Lagovirus europaeus/Rabbit Hemorrhagic Disease Virus (RHDV) compared to healthy rabbits. The results indicated a role for ocu-miR-155-5p in Lagovirus europaeus/RHDV infection and reflected hepatitis and the impairment/dysfunction of this organ during RHD. MiR-155-5p was, therefore, hypothesized as a potential candidate for a tissue biomarker of inflammation and examined in tissues in Lagovirus europaeus/RHDV infection by dPCR. The objective of the study is the absolute quantification of ocu-miR-155-5p in four tissues (liver, lung, kidney, and spleen) of rabbits infected with Lagovirus europaeus/RHDV by digital PCR, a robust technique for the precise and direct quantification of small amounts of nucleic acids, including miRNAs, without standard curves and external references. The average copy number/µL (copies/µL) of ocu-miRNA-155-5p in rabbits infected with Lagovirus europaeus GI.1a/Rossi in the liver tissue was 12.26 ± 0.14, that in the lung tissue was 48.90 ± 9.23, that in the kidney tissue was 16.92 ± 2.89, and that in the spleen was 25.10 ± 0.90. In contrast, in the tissues of healthy control rabbits, the average number of copies/µL of ocu-miRNA-155-5p was 5.07 ± 1.10 for the liver, 23.52 ± 2.77 for lungs, 8.10 ± 0.86 for kidneys, and 42.12 ± 3.68 for the spleen. The increased expression of ocu-miRNA-155-5p in infected rabbits was demonstrated in the liver (a fold-change of 2.4, p-value = 0.0003), lung (a fold-change of 2.1, p-value = 0.03), and kidneys (a fold-change of 2.1, p-value = 0.01), with a decrease in the spleen (a fold-change of 0.6, p-value = 0.002). In the study of Lagovirus europaeus/RHDV infection and in the context of viral infections, this is the first report that shows the potential use of dPCR for the sensitive and absolute quantification of microRNA-155-5p in tissues during viral infection. We think miR-155-5p may be a potential candidate for a tissue biomarker of inflammation with Lagovirus europaeus/RHDV infection. Our report presents a new path in discovering potential candidates for the tissue biomarkers of inflammation.

Pulmonary Microcirculation in Experimental Model of Pulmonary Thromboembolism after Pretreatment with Chloroquine.

Changes of pulmonary microcirculation in response to pulmonary artery embolization after pretreatment with chloroquine were studied on the model of isolated perfused rabbit lungs. The increase in the pulmonary vascular resistance and pre- and postcapillary resistance was less pronounced than after pulmonary thromboembolism after pretreatment with mibefradil (T-type Ca2+ channels blocker) or nifedipine (L-type Ca2+ channels blocker). The shifts of capillary filtration coefficient correlated with changes in the precapillary resistance. When modeling pulmonary thromboembolism after pretreatment with chloroquine combined with glibenclamide (KATP channels blocker), the studied hemodynamics parameters increased to the same extent as after pretreatment with nifedipine. The results indicate that chloroquine exhibits the properties of an L- and T-type Ca2+ channels blocker and an activator of KATP channels.

Mathematical modeling suggests heterogeneous replication of Mycobacterium tuberculosis in rabbits

Abstract Tuberculosis (TB), the disease caused by Mycobacterium tuberculosis (Mtb), remains the major health problem. We performed experiments with rabbits infected with a novel, virulent clinical Mtb isolate of the Beijing lineage HN878 carrying an unstable plasmid pBP10, allowing us to quantify how quickly HN878 replicates and dies in lungs of rabbits. In our in vitro experiments we found that pBP10 is more stable in HN878 strain than in a more commonly used laboratory-adapted H37Rv strain (the segregation coefficient being s=0.10 in HN878 vs. s=0.18 in H37Rv). Interestingly, the kinetics of the frequency of plasmid-bearing bacteria in lungs of Mtb-infected rabbits did not follow an expected monotonic decline; the percent of Mtb-bearing cells increased between 4 and 8 weeks post-infection and remained stable between 12 and 18 weeks post-infection despite a large increase in bacterial numbers in the lung at these time points. Mathematical modeling suggested that such a non-monotonic change in the percent of plasmid-bearing cells can be explained if the lung Mtb population consists of several (at least 2) sub-populations with different replication kinetics: one major population expanding early and being controlled, while another, a smaller population expanding at later times causing a counterintuitive increase in the percent of plasmid-bearing cells. Given that HN878 forms well circumscribed granulomas in rabbits, our results suggest independent bacterial dynamics in subsets of such granulomas. Our model predictions can be tested in experiments in which HN878-pBP10 dynamics in individual granulomas is followed over time. 1R01AI158963-01A1

Prematurity and Hyperoxia Have Different Effects on Alveolar and Microvascular Lung Development in the Rabbit.

Bronchopulmonary dysplasia (BPD) is a developmental disorder of infants born prematurely, characterized by disrupted alveolarization and microvascular maturation. However, the sequence of alveolar and vascular alterations is currently not fully understood. Therefore, we used a rabbit model to evaluate alveolar and vascular development under preterm birth and hyperoxia, respectively. Pups were born by cesarean section 3 days before term and exposed for 7 days to hyperoxia (95% O2) or normoxia (21% O2). In addition, term-born rabbits were exposed to normoxia for 4 days. Rabbit lungs were fixed by vascular perfusion and prepared for stereological analysis. Normoxic preterm rabbits had a significantly lower number of alveoli than term rabbits. The number of septal capillaries was lower in preterm rabbits but less pronounced than the alveolar reduction. In hyperoxic preterm rabbits, the number of alveoli was similar to that in normoxic preterm animals; however, hyperoxia had a severe additional negative effect on the capillary number. In conclusion, preterm birth had a strong effect on alveolar development, and hyperoxia had a more pronounced effect on capillary development. The data provide a complex picture of the vascular hypothesis of BPD which rather seems to reflect the ambient oxygen concentration than the effect of premature birth.