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Background Post-COVID-19 condition encompasses symptoms following COVID-19 infection that linger at least 4 weeks after the end of active infection. Symptoms are wide ranging, but breathlessness is common. Purpose To determine if the previously described lung abnormalities seen on hyperpolarized (HP) pulmonary xenon 129 (

This study describes the use of cynomolgus macaques of Chinese origin (CCM) to evaluate the efficacy and immunogenicity of the BCG vaccine against high dose aerosol Mycobacterium tuberculosis challenge. Progressive disease developed in three of the unvaccinated animals within 10 weeks of challenge, whereas all six vaccinated animals controlled disease for 26 weeks. Three unvaccinated animals limited disease progression, highlighting the intrinsic ability of this macaque species to control disease in comparison to macaques of other species and genotypes. Low levels of IFNγ were induced by BCG vaccination in CCM suggesting that IFNγ alone does not provide a sufficiently sensitive biomarker of vaccination in this model. An early response after challenge, together with the natural bias towards terminal effector memory T-cell populations and the contribution of monocytes appears to enhance the ability of CCM to naturally control infection. The high dose aerosol challenge model of CCM has value for examination of the host immune system to characterise control of infection which would influence future vaccine design. Although it may not be the preferred platform for the assessment of prophylactic vaccine candidates, the model could be well suited for testing post-exposure vaccination strategies and drug evaluation studies.

Until validated correlates of protection are identified, animal models remain the only way to test the efficacy of the new vaccines and drugs urgently needed to fight the global epidemic caused by infection with Mycobacterium tuberculosis. Non-human primates (NHP) offer the most relevant models of human tuberculosis (TB) and are central to the development process for new interventions. Efficacy evaluations are dependent on the capability of the test model to discriminate improved outcomes between treated groups after experimental exposure to M. tuberculosis and therefore the ability to measure TB-induced disease burden is central to the process. We have developed a score system that allows us to quantify the disease burden induced in macaques by infection with M. tuberculosis, based on the extent and features of disease visible on computed tomography (CT) images. The CT determined disease burden was then verified against that obtained using an established pathology-based approach. Trials of the system as a tool to measure disease burden have shown the approach capable of revealing differences between treatment groups in order to: (a) characterise outcome of infection and enable model refinement; (b) demonstrate the efficacy of drug treatment regimens by showing differences in outcome between test groups. Initial trials suggest that the imaging-based score system provides a valuable additional tool for the measurement of TB-induced disease burden that offers the opportunity to apply both refinement and reduction within studies.

Objectives To investigate the use of a fast dynamic hyperpolarised 129Xe ventilation magnetic resonance imaging (DXeV-MRI) method for detecting and quantifying delayed ventilation in patients with chronic obstructive pulmonary disease (COPD). Methods Three male participants (age range 31–43) with healthy lungs and 15 patients (M/F = 12:3, age range = 48–73) with COPD (stages II–IV) underwent spirometry tests, quantitative chest computed tomography (QCT), and DXeV-MRI at 1.5-Tesla. Regional delayed ventilation was captured by measuring the temporal signal change in each lung region of interest (ROI) in comparison to that in the trachea. In addition to its qualitative assessment through visual inspection by a clinical radiologist, delayed ventilation was quantitatively captured by calculating a covariance measurement of the lung ROI and trachea signals, and quantified using both the time delay, and the difference between the integrated areas covered by the signal-time curves of the two signals. Results Regional temporal ventilation, consistent with the expected physiological changes across a free breathing cycle, was demonstrated with DXeV-MRI in all patients. Delayed ventilation was observed in 13 of the 15 COPD patients and involved variable lung ROIs. This was in contrast to the control group, where no delayed ventilation was demonstrated (p = 0.0173). Conclusions DXeV-MRI offers a non-invasive way of detecting and quantifying delayed ventilation in patients with COPD, and provides physiological information on regional pulmonary function during a full breathing cycle. Key Points • Dynamic xenon MRI allows for the non-invasive detection and measurement of delayed ventilation in COPD patients. • Dynamic xenon MRI during a free breathing cycle can provide unique information about pulmonary physiology and pulmonary disease pathophysiology. • With further validation, dynamic xenon MRI could offer a non-invasive way of measuring collateral ventilation which can then be used to guide lung volume reduction therapy (LVRT) for certain COPD patients. Electronic supplementary material The online version of this article (10.1007/s00330-019-06415-1) contains supplementary material, which is available to authorized users.

Purpose To derive lobar ventilation in patients with chronic obstructive pulmonary disease (COPD) using a rapid time-series hyperpolarized xenon-129 (HPX) magnetic resonance imaging (MRI) technique and compare this to ventilation/perfusion single-photon emission computed tomography (V/Q-SPECT), correlating the results with high-resolution computed tomography (CT) and pulmonary function tests (PFTs). Materials and methods Twelve COPD subjects (GOLD stages I–IV) participated in this study and underwent HPX-MRI, V/Q-SPECT/CT, high-resolution CT, and PFTs. HPX-MRI was performed using a novel time-series spiral k-space sampling approach. Relative percentage ventilations were calculated for individual lobe for comparison to the relative SPECT lobar ventilation and perfusion. The absolute HPX-MRI percentage ventilation in each lobe was compared to the absolute CT percentage emphysema score calculated using a signal threshold method. Pearson’s correlation and linear regression tests were performed to compare each imaging modality. Results Strong correlations were found between the relative lobar percentage ventilation with HPX-MRI and percentage ventilation SPECT (r = 0.644; p

Purpose To perform magnetic resonance imaging (MRI), human lung imaging, and quantification of the gas-transfer dynamics of hyperpolarized xenon-129 (HPX) from the alveoli into the blood plasma. Materials and methods HPX MRI with iterative decomposition of water and fat with echo asymmetry and least-square estimation (IDEAL) approach were used with multi-interleaved spiral k-space sampling to obtain HPX gas and dissolved phase images. IDEAL time-series images were then obtained from ten subjects including six normal subjects and four patients with pulmonary emphysema to test the feasibility of the proposed technique for capturing xenon-129 gas-transfer dynamics (XGTD). The dynamics of xenon gas diffusion over the entire lung was also investigated by measuring the signal intensity variations between three regions of interest, including the left and right lungs and the heart using Welch’s t test. Results The technique enabled the acquisition of HPX gas and dissolved phase compartment images in a single breath-hold interval of 8 s. The y-intersect of the XGTD curves were also found to be statistically lower in the patients with lung emphysema than in the healthy group (p

Summary Well characterised animal models that can accurately predict efficacy are critical to the development of an improved TB vaccine. The use of high dose challenge for measurement of efficacy in Non-human primate models brings the risk that vaccines with the potential to be efficacious against natural challenge could appear ineffective and thus disregarded. Therefore, there is a need to develop a challenge regimen that is more relevant to natural human infection. This study has established that ultra-low dose infection of macaques via the aerosol route can be reproducibly achieved and provides the first description of the development of TB disease in both rhesus and cynomolgus macaques following exposure to estimated retained doses in the lung of less than 10 CFU of Mycobacterium tuberculosis. CT scanning in vivo and histopathology revealed differences in the progression and burden of disease between the two species. Rhesus macaques exhibited a more progressive disease and cynomolgus macaques showed a reduced disease burden. The ability to deliver reproducible ultra-low dose aerosols to macaques will enable the development of refined models of M. tuberculosis infection for evaluation of the efficacy of novel tuberculosis vaccines that offers increased clinical relevance and improved animal welfare.

Purpose To develop and optimize a rapid dynamic hyperpolarized 129Xe ventilation (DXeV) MRI protocol and investigate the feasibility of capturing pulmonary signal‐time curves in human lungs. Theory and Methods Spiral k‐space trajectories were designed with the number of interleaves N int = 1, 2, 4, and 8 corresponding to voxel sizes of 8 mm, 5 mm, 4 mm, and 2.5 mm, respectively, for field of view = 15 cm. DXeV images were acquired from a gas‐flow phantom to investigate the ability of N int = 1, 2, 4, and 8 to capture signal‐time curves. A finite element model was constructed to investigate gas‐flow dynamics corroborating the experimental signal‐time curves. DXeV images were also carried out in six subjects (three healthy and three chronic obstructive pulmonary disease subjects). Results DXeV images and numerical modelling of signal‐time curves permitted the quantification of temporal and spatial resolutions for different numbers of spiral interleaves. The two‐interleaved spiral (N int = 2) was found to be the most time‐efficient to obtain DXeV images and signal‐time curves of whole lungs with a temporal resolution of 624 ms for 13 slices. Signal‐time curves were well matched in three healthy volunteers. The Spearman's correlations of chronic obstructive pulmonary disease subjects were statistically different from three healthy subjects (P

Intradermal (ID) BCG injection provides incomplete protection against TB in humans and experimental models. Alternative BCG vaccination strategies may improve protection in model species, including rhesus macaques. This study compares the immunogenicity and efficacy of BCG administered by ID and intravenous (IV) injection, or as an intratracheal mucosal boost (ID + IT), against aerosol challenge with Mycobacterium tuberculosis Erdman strain. Disease pathology was significantly reduced, and survival improved, by each BCG vaccination strategy, relative to unvaccinated animals. However, IV induced protection surpassed that achieved by all other routes, providing an opportunity to explore protective immunological mechanisms using antigen-specific IFN-γ ELISpot and polychromatic flow cytometry assays. IFN-γ spot forming units and multifunctional CD4 T-cell frequencies increased significantly following each vaccination regimen and were greatest following IV immunisation. Vaccine-induced multifunctional CD4 T-cells producing IFN-γ and TNF-α were associated with reduced disease pathology following subsequent M.tb challenge; however, high frequencies of this population following M.tb infection correlated with increased pathology. Cytokine producing T-cells primarily occupied the CD4 transitional effector memory phenotype, implicating this population as central to the mycobacterial response, potentially contributing to the stringent control observed in IV vaccinated animals. This study demonstrates the protective efficacy of IV BCG vaccination in rhesus macaques, offering a valuable tool for the interrogation of immunological mechanisms and potential correlates of protection.

SummaryNon-human primates (NHP) provide a key component in the preclinical assessment pathway for new TB vaccines. In the established models, Mycobacterium tuberculosis challenge is typically delivered to airways of macaques either by aerosol or bronchoscopic instillation and therefore, an understanding of these delivery routes would facilitate the comparison of data generated from models using different challenge methods. This study compared the clinical effects, antigen-specific IFNγ response profiles and disease burden following delivery of comparable doses of M. tuberculosis to the lungs of rhesus macaques by either aerosol or bronchoscopic instillation. The outcome of infection in terms of clinical effects and overall disease burden was comparable between both routes of challenge. However, the pathology in the lungs differed as disease was localised to the site of inoculation following bronchoscopic instillation while aerosol exposure resulted in lesions being evenly distributed through the lung. Whilst the IFNγ response to PPD was similar, responses to CFP10 and ESAT6 peptide pools measured with an ex vivo ELISPOT differed with regards to responses to the N-terminal regions depending on the route of infection. Both challenge routes therefore provide valid and comparable models for evaluation of new TB vaccines, although subtle differences in host responses may occur.

Summary Three rhesus macaques (Macaca mulatta) were challenged with Mycobacterium tuberculosis (Mtb), Erdman strain, as part of studies to investigate lesion development at early time points in tuberculosis (TB) and to assess computed tomography (CT) as a method of monitoring disease progression in vivo. Animals were challenged with either a high, mid or low dose of aerosolized Mtb. The low-dose animal was killed humanely at 24 days post challenge (dpc) and the remaining animals at 25 dpc. Abnormalities in clinical parameters were observed in all animals, but clinical signs relating to respiratory disease were not seen. Pulmonary changes consistent with TB infection were detected by CT at 21 dpc and magnetic resonance imaging (MRI) post mortem. Pulmonary nodule counts obtained from both imaging techniques were directly proportional to the challenge dose and correlated with gross and microscopical lesion counts. On gross and microscopical examination, lesions of similar size and morphology were observed in the lungs of all three animals, with the majority containing necrotic foci. Concomitant gross and microscopical, granulomatous lesions were observed in the tracheobronchial lymph nodes of all animals together with evidence of systemic spread. These findings further contribute to our understanding and knowledge of early lesion formation in the lungs of non-human primates.