PET imaging of TSPO expression in immune cells can assess organ-level pathophysiology in high-consequence viral infections.

Ebola virus (EBOV) disease is characterized by lymphopenia, breach in vascular integrity, cytokine storm, and multiorgan failure. The pathophysiology of organ involvement, however, is incompletely understood. Using [18F]-DPA-714 positron emission tomography (PET) imaging targeting the translocator protein (TSPO), an immune cell marker, we sought to characterize the progression of EBOV-associated organ-level pathophysiology in the EBOV Rhesus macaque model. Dynamic [18F]-DPA-714 PET/computed tomography imaging was performed longitudinally at baseline and at multiple time points after EBOV inoculation, and distribution volumes (Vt) were calculated as a measure of peripheral TSPO binding. Using a mixed-effect linear regression model, spleen and lung Vt decreased, while the bone marrow Vt increased over time after infection. No clear trend was found for liver Vt. Multiple plasma cytokines correlated negatively with lung/spleen Vt and positively with bone marrow Vt. Multiplex immunofluorescence staining in spleen and lung sections confirmed organ-level lymphoid and monocytic loss/apoptosis, thus validating the imaging results. Our findings are consistent with EBOV-induced progressive monocytic and lymphocytic depletion in the spleen, rather than immune activation, as well as depletion of alveolar macrophages in the lungs, with inefficient reactive neutrophilic activation. Increased bone marrow Vt, on the other hand, suggests hematopoietic activation in response to systemic immune cell depletion and leukocytosis and could have prognostic relevance. In vivo PET imaging provided better understanding of organ-level pathophysiology during EBOV infection. A similar approach can be used to delineate the pathophysiology of other systemic infections and to evaluate the effectiveness of newly developed treatment and vaccine strategies.

PET imaging of Aspergillus infection using Zirconium-89 labeled anti-ß-glucan antibody fragments.

PURPOSE: Invasive fungal diseases, such as pulmonary aspergillosis, are common life-threatening infections in immunocompromised patients and effective treatment is often hampered by delays in timely and specific diagnosis. Fungal-specific molecular imaging ligands can provide non-invasive readouts of deep-seated fungal pathologies. In this study, the utility of antibodies and antibody fragments (Fab) targeting ß-glucans in the fungal cell wall to detect Aspergillus infections was evaluated both in vitro and in preclinical mouse models. METHODS: The binding characteristics of two commercially available ß-glucan antibody clones and their respective antigen-binding Fabs were tested using biolayer interferometry (BLI) assays and immunofluorescence staining. In vivo binding of the Zirconium-89 labeled antibodies/Fabs to fungal pathogens was then evaluated using PET/CT imaging in mouse models of fungal infection, bacterial infection and sterile inflammation. RESULTS: One of the evaluated antibodies (HA-ßG-Ab) and its Fab (HA-ßG-Fab) bound to ß-glucans with high affinity (KD = 0.056 & 21.5 nM respectively). Binding to the fungal cell wall was validated by immunofluorescence staining and in vitro binding assays. ImmunoPET imaging with intact antibodies however showed slow clearance and high background signal as well as nonspecific accumulation in sites of infection/inflammation. Conversely, specific binding of [89Zr]Zr-DFO-HA-ßG-Fab to sites of fungal infection was observed when compared to the isotype control Fab and was significantly higher in fungal infection than in bacterial infection or sterile inflammation. CONCLUSIONS: [89Zr]Zr-DFO-HA-ßG-Fab can be used to detect fungal infections in vivo. Targeting distinct components of the fungal cell wall is a viable approach to developing fungal-specific PET tracers.

Advances and Challenges in Molecular Imaging of Viral Infections.

Molecular imaging of viral infection, using a variety of advanced imaging techniques such as optical and nuclear imaging, can and has been used for direct visualization of the virus as well as assessment of virus-host interactions. Unlike imaging of other pathogens such as bacteria and fungi, challenging aspects of imaging viral infections include the small size of viruses, the complexity of viral infection animal models (eg, species dependence), and the high-level containment needs for many high-consequence pathogens, among others. In this review, using representative viral infections, we discuss how molecular imaging can reveal real-time infection dynamics, improve our understanding of disease pathogenesis, and guide optimization of treatment and prevention strategies. Key findings from human and animal studies are highlighted.

The Promise of Molecular Imaging: Focus on Central Nervous System Infections.

Central nervous system (CNS) infections can lead to high mortality and severe morbidity. Diagnosis, monitoring, and assessing response to therapy of CNS infections is particularly challenging with traditional tools, such as microbiology, due to the dangers associated with invasive CNS procedures (ie, biopsy or surgical resection) to obtain tissues. Molecular imaging techniques like positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging have long been used to complement anatomic imaging such as computed tomography (CT) and magnetic resonance imaging (MRI), for in vivo evaluation of disease pathophysiology, progression, and treatment response. In this review, we detail the use of molecular imaging to delineate host-pathogen interactions, elucidate antimicrobial pharmacokinetics, and monitor treatment response. We also discuss the utility of pathogen-specific radiotracers to accurately diagnose CNS infections and strategies to develop radiotracers that would cross the blood-brain barrier.

Synthesis and Evaluation of Fluorine-18-Labeled L-Rhamnose Derivatives.

The use of radiolabeled glucose for PET imaging resulted in the most commonly used tracer in the clinic, 2-deoxy-2-[18F]fluoroglucose (FDG). More recently, other radiolabeled sugars have been reported for various applications, including imaging tumors and infections. Therefore, in this study, we developed a series of fluorine-18-labeled L-rhamnose derivatives as potential PET tracers of various fungal and bacterial strains. Acetyl-protected triflate precursors of rhamnose were prepared and radiolabeled with fluorine-18 followed by hydrolysis to produce L-deoxy [18F]fluororhamnose. The overall radiochemical yield was 7-27% in a 90 min synthesis time with a radiochemical purity of 95%. In vivo biodistribution of the ligands using PET imaging showed that 2-deoxy-2-[18F]fluoro-L-rhamnose is stable for at least up to 60 min in mice and eliminated via renal clearance. The tracer also exhibited minimal tissue or skeletal uptake in healthy mice resulting in a low background signal.

Mycobacterium tuberculosis Inhibits Autocrine Type I IFN Signaling to Increase Intracellular Survival.

The type I IFNs (IFN-α and -ß) are important for host defense against viral infections. In contrast, their role in defense against nonviral pathogens is more ambiguous. In this article, we report that IFN-ß signaling in murine bone marrow-derived macrophages has a cell-intrinsic protective capacity against Mycobacterium tuberculosis via the increased production of NO. The antimycobacterial effects of type I IFNs were mediated by direct signaling through the IFN-α/ß-receptor (IFNAR), as Ab-mediated blocking of IFNAR1 prevented the production of NO. Furthermore, M. tuberculosis is able to inhibit IFNAR-mediated cell signaling and the subsequent transcription of 309 IFN-ß-stimulated genes in a dose-dependent way. The molecular mechanism of inhibition by M. tuberculosis involves reduced phosphorylation of the IFNAR-associated protein kinases JAK1 and TYK2, leading to reduced phosphorylation of the downstream targets STAT1 and STAT2. Transwell experiments demonstrated that the M. tuberculosis-mediated inhibition of type I IFN signaling was restricted to infected cells. Overall, our study supports the novel concept that M. tuberculosis evolved to inhibit autocrine type I IFN signaling to evade host defense mechanisms.

Nitrosative Stress Is Associated with Dopaminergic Dysfunction in the HIV-1 Transgenic Rat.

Advances in antiretroviral therapy have resulted in significantly decreased HIV-related mortality. HIV-associated neurocognitive disorders, however, continue to be a major problem in infected patients. The neuropathology underlying HIV-associated neurocognitive disorders has not been well characterized, and evidence suggests different contributing mechanisms. One potential mechanism is the induction of oxidative stress. Using the HIV-1 transgenic (Tg) rat model of HIV, we found increased striatal NADPH oxidase-4 and neuronal nitric oxide synthase expression in the adult (7- to 9-month-old) Tg rat compared with control rats but not in the young (1-month-old) Tg rats. This was accompanied by increased 3-nitrotyrosine (3-NT) immunostaining in the adult Tg rats, which worsened significantly in the old Tg rats (18 to 20 months old). There was, however, no concurrent induction of the antioxidant systems because there was no change in the expression of the nuclear factor-erythroid 2-related factor 2 and its downstream targets (thioredoxin and glutathione antioxidant systems). Colocalization of 3-NT staining with neurofilament proteins and evidence of decreased tyrosine hydroxylase and dopamine transporter expression in the old rats support dopaminergic involvement. We conclude that the HIV-1 Tg rat brain shows evidence of nitrosative stress without appropriate oxidation-reduction adaptation, whereas 3-NT modification of striatal neurofilament proteins likely points to the ensuing dopaminergic neuronal loss and dysfunction in the aging HIV-1 Tg rat.

Brain 18F-FDG PET of SIV-infected macaques after treatment interruption or initiation.

BACKGROUND: Although rates of severe HIV-associated neurocognitive disorders have declined in the post-antiretroviral treatment (ART) era, subtle deficits persist, possibly exacerbated by treatment non-adherence. The actual effects of ART interruption/initiation on brain glucose metabolism as a reflection of viral replication and neuroinflammation remain unclear. Our study investigates how treatment initiation and interruption alter brain glucose metabolism in SIV-infected macaques, using 18F-FDG PET in correlation with plasma and CSF viral loads (VL) and cytokine levels. METHODS: SIV-infected macaques (n = 7) underwent ART initiation only, ART interruption only, or both. Five uninfected animals served as controls. 18F-FDG PET imaging was performed at baseline and 1, 3, and 6 months after treatment modification. Mean and maximum standardized uptake values (SUV) for the whole-brain and subregions were calculated. Plasma and CSF VL and cytokine levels were measured. Paired t tests evaluated acute changes in whole-brain SUV from baseline to 1 month, while mixed-effect linear regression models evaluated changes over multiple timepoints and correlated SUV values with disease markers. RESULTS: ART interruption was associated with increased SUVmean and SUVmax acutely, after 1 month (SUVmean 95% CI [0.044-0.786 g/ml], p = 0.037; SUVmax 95% CI [0.122-3.167 g/ml], p = 0.041). The correlation between SUV and time, however, was not significant when evaluated across all timepoints. Increased SUVmean and SUVmax correlated with decreased CD4+ and CD8+ T-cell counts and increased plasma VL. SUVmax was positively associated with increases in CSF VL, and there were borderline positive associations between SUVmax and IL-2, and between SUVmean and IL-15. The treatment initiation group showed no associations between imaging and disease biomarkers despite viral suppression, reduced cytokine levels, and increased CD4+ and CD8+ T-cell counts. CONCLUSIONS: ART interruption is associated with increased brain glucose metabolism within 1 month of treatment cessation, which, in concert with increased levels of pro-inflammatory cytokines in the CSF, may reflect neuroinflammation in the setting of viral rebound. Although we cannot assert neurologic damage in association with cerebral hypermetabolism, it is a concerning outcome of ART non-adherence. Treatment initiation, meanwhile, did not result in significant changes in brain metabolism. HIV-induced neuroinflammation may require a longer period to abate than our follow-up period allowed.

Comparing Outcomes of Robotic and Open Inguinal Lymph Node Dissection in Patients with Carcinoma of the Penis.

PURPOSE: We compared outcomes between robot-assisted video endoscopic inguinal lymphadenectomy and open inguinal lymph node dissection in patients without bulky nodal metastasis in a tandem contemporary cohort. MATERIALS AND METHODS: We retrospectively analyzed a prospectively maintained hospital registry of 51 patients who underwent robot-assisted video endoscopic inguinal lymphadenectomy and 100 treated with open inguinal lymph node dissection from 2012 to 2016 for groins without bulky nodal metastasis and who had a minimum 9-month followup. Complications were graded by the Clavien-Dindo classification, and nodal yield and disease recurrence during followup were assessed. Elastic net regression was used to select variables associated with major complications (Clavien 3a or greater) for multivariable analysis of plausible factors, including patient age, diabetes, body mass index, smoking, nodal stage, surgery type, sartorius transposition, saphenous vein transection and adjuvant radiotherapy. Penalized likelihood logistic regression methods were used for multivariate analysis to ascertain final effect sizes while accounting for sparse data bias. RESULTS: Robot-assisted video endoscopic inguinal lymphadenectomy and open inguinal lymph node dissection had comparable median lymph node yields (13 vs 12.5). No patient experienced recurrence during the median followup of 40 months. Robot-assisted video endoscopic inguinal lymphadenectomy was associated with significantly lower hospital stay, days needing a drain in situ, incidence of major complications, edge necrosis, flap necrosis and severe limb edema. On multivariable analysis pathological nodal stage (OR 2.8, 95% CI 1.1-6.8, p = 0.027) and open inguinal lymph node dissection (OR 7.5, 95% CI 1.3-43, p = 0.024) emerged as independent risk factors associated with an increased risk of major complications. CONCLUSIONS: Robot-assisted video endoscopic inguinal lymphadenectomy is a feasible technique which allows for a similar nodal yield while being associated with lower morbidity than open inguinal lymph node dissection in patients without bulky groin adenopathy.

Robotic-Assisted Video Endoscopic Inguinal Lymphadenectomy in Carcinoma Vulva: Our Experiences and Intermediate Results.

OBJECTIVES: To describe the technique of robotic-assisted video endoscopic inguinal lymphadenectomy (R-VEIL) in patients with carcinoma vulva and discuss the advantages of the technique and oncological outcome. METHODS: Twelve patients of squamous cell cancer of vulva underwent 22 R-VEIL procedures from February 2011 to February 2015. Their preoperative, intraoperative, and postoperative data were retrospectively analysed. RESULTS: The mean age of patients was 61 years (range, 32-78 years). The mean operative time was 69.3 minutes (range, 45-95 minutes). The mean blood loss was 30 mL (range, 15-50 mL). No intraoperative complication was observed. The mean drain output was 119 mL (range, 50-250 mL), and the drains were removed at a mean of 13.9 days (range, 8-38 days). The average number of superficial and deep inguinofemoral lymph nodes retrieved was 11 (range, 4-26). Two patients had positive lymph nodes on histopathology (16.67%). Postoperative complications were lymphocele (6 groins), chronic lower limb lymphedema (6 cases), prolonged lymphorrhea (1 groin), and cellulitis (2 groins). Over a follow-up period ranging from 7 to 67 months, 1 patient developed recurrence in the inguinal nodes and died 7 months after the recurrence. CONCLUSIONS: The R-VEIL allows the removal of inguinal lymph nodes within the same limits as the open procedure for inguinal lymph node dissection and has a potential to reduce the surgical morbidity associated with the open procedure. Long-term oncological results are not available though our initial results appear promising. Prospective multi-institutional studies are required to prove its efficacy over open inguinal lymph node dissection.

A Duplicated ESAT-6 Region of ESX-5 Is Involved in Protein Export and Virulence of Mycobacteria.

The ESX-5 secretion system of Mycobacterium tuberculosis is important for bacterial virulence and for the secretion of the large PE/PPE protein family, whose genes constitute 10% of the M. tuberculosis genome. A four-gene region of the ESX-5 system is duplicated three times in the M. tuberculosis genome, but the functions of these duplicates are unknown. Here we investigated one of these duplicates: the region carrying the esxI, esxJ, ppe15, and pe8 genes (ESX-5a). An ESX-5a deletion mutant in the model system M. marinum background was deficient in the secretion of some members of the PE/PPE family of proteins. Surprisingly, we also identified other proteins that are not members of this family, thus expanding the range of ESX-5 secretion substrates. In addition, we demonstrated that ESX-5a is important for the virulence of M. marinum in the zebrafish model. Furthermore, we showed the role of the M. tuberculosis ESX-5a region in inflammasome activation but not host cell death induction, which is different from the case for the M. tuberculosis ESX-5 system. In conclusion, the ESX-5a region is nonredundant with its ESX-5 paralog and is necessary for secretion of a specific subset of proteins in M. tuberculosis and M. marinum that are important for bacterial virulence of M. marinum. Our findings point to a role for the three ESX-5 duplicate regions in the selection of substrates for secretion via ESX-5, and hence, they provide the basis for a refined model of the molecular mechanism of this type VII secretion system.

Cutting edge: Mycobacterium tuberculosis but not nonvirulent mycobacteria inhibits IFN-ß and AIM2 inflammasome-dependent IL-1ß production via its ESX-1 secretion system.

Mycobacterium tuberculosis extracellular DNA gains access to the host cell cytosol via the ESX-1 secretion system. It is puzzling that this extracellular DNA of M. tuberculosis does not induce activation of the AIM2 inflammasome because AIM2 recognizes cytosolic DNA. In this study, we show that nonvirulent mycobacteria such as Mycobacterium smegmatis induce AIM2 inflammasome activation, which is dependent on their strong induction of IFN-ß production. In contrast, M. tuberculosis, but not an ESX-1-deficient mutant, inhibits the AIM2 inflammasome activation induced by either M. smegmatis or transfected dsDNA. The inhibition does not involve changes in host cell AIM2 mRNA or protein levels but led to decreased activation of caspase-1. We furthermore demonstrate that M. tuberculosis inhibits IFN-ß production and signaling, which was partially responsible for the inhibition of AIM2 activation. In conclusion, we report a novel immune evasion mechanism of M. tuberculosis that involves the ESX-1-dependent, direct or indirect, suppression of the host cell AIM2 inflammasome activation during infection.

Transoral robotic surgery in management of oropharyngeal cancers: a preliminary experience at a tertiary cancer centre in India.

BACKGROUND: The aim of this observational prospective study was to determine the technical feasibility, safety and adequacy of surgical margins for transoral robotic surgery (TORS) in oropharyngeal cancers. METHODS: From March 2013 to May 2014, 60 patients with oropharyngeal lesions underwent TORS with or without neck dissection using the 'DaVinci' robot. Patients were observed and data recorded on surgical time, blood loss, complications and functional outcome of patients. RESULTS: All 60 patients underwent TORS, with neck dissection performed in 45 of the patients. A positive margin was seen in two patients (3.3 %). Intent to treatment was radical in 42 patients and salvage in 18 patients. None of the patients required tracheostomy, and one patient (1.66 %) died postoperatively. Postoperative complications in the form of primary haemorrhage required active intervention in three patients. Average estimated blood loss was 26.5 ± 31.1 ml. Postoperatively, all patients had adequate swallowing and speech function with nasal twang reported in three patients on long-term follow up. Patients started tolerating oral feeds within a week of procedure (mean 3.96 days), with the nasogastric tube removed on the ninth postoperative day (mean 9.19 days). No long-term gastrostomy tube dependency was reported. CONCLUSION: TORS is a safe, feasible, minimally invasive procedure in patients with oropharyngeal cancers. It has the least morbidity and offers benefits in terms of avoidance of tracheostomy tube, prolonged Ryle's tube and gastrostomy dependency.

Metabolic syndrome in patients with lichen planus: A case-control study.

Background: Lichen Planus (LP) is a chronic dermatosis affecting the skin and mucous membranes. Chronic inflammation and oxidative stress in patients with LP is a trigger predisposing to Metabolic Syndrome. Objectives: To study the association of Metabolic Syndrome in patients with LP. Materials and Methods: A hospital-based prospective case-control study was conducted from April 2021 to January 2023 including 75 histopathologically confirmed patients with LP and 82 age and sex-matched controls according to the inclusion and exclusion criteria. Metabolic Syndrome was diagnosed using Modified National Cholesterol Education Programme Adult Treatment Panel III criteria. Statistical analysis of the data was performed using Statistical Package for the Social Sciences software, version 26. The chi-square test was used for data analysis. Results: The majority (30.6%) of the patients belonged to the age group 31-40 years. The mean age of patients with LP was 46.13 ± 14.9 years. Female predominance (69.3%) was observed in our study. Patients with classic LP (54.6%) were predominantly observed. Metabolic Syndrome was significantly prevalent in LP patients than in controls (32% vs. 13.4%, p = 0.005, OR 3.037) and was significantly associated with morphology (only oral mucosal involvement, 61.5%, p 0.027, OR 3.9), severity (severe LP, 58.6%, p < 0.001, OR 7.79), and duration of the disease (≥6 months, 55.5%, p 0.001, OR 5.42). 71% of Metabolic Syndrome was observed in females (p 0.847). Among patients with metabolic syndrome, the majority belonged to the age group between 31 and 40 years (37.5%, p 0.378). Systolic and Diastolic Blood Pressure values (≥130/85 mm of Hg), Serum Triglycerides (≥150 mg/dl), and Low-Density Lipoprotein (>130 mg/dl) were significantly elevated, and High-Density Lipoprotein (<40 mg/dl) was significantly low in LP than in controls (p < 0.05). Conclusion: The study showed a significant association of Metabolic Syndrome in patients with LP. Thus, patients with LP need to be screened to avoid complications associated with Metabolic Syndrome that is, Diabetes Mellitus, Cardiovascular Disease, colorectal cancer, and stroke.

Upper limb muscle strength & endurance in chronic obstructive pulmonary disease.

BACKGROUND & OBJECTIVES: There are very few studies that have investigated the muscle strength and endurance of upper limbs (UL) in chronic obstructive pulmonary disease (COPD). We undertook this study to measure and compare the skeletal muscle strength and endurance of UL in COPD patients and age matched healthy controls and to study the association between lung function parameters and UL muscle strength and endurance. METHODS: Forty one COPD patients and 45 height and weight matched healthy subjects of the same age group were studied. UL skeletal muscle strength and endurance were measured using the hand grip dynamometer test. Forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), forced expiratory flow during 25-75% FVC (FEF (25-75%)) and peak expiratory flow rate (PEFR) were measured. The handgrip muscle strength and endurance between the two groups were compared and correlations between FVC and FEV 1 with muscle strength and endurance were analyzed. RESULTS: The mean handgrip strength and mean muscle endurance in COPD patients were significantly lesser than the normal subjects in both males and females (P<0.001). There was significant positive correlation between muscle strength and FVC in males (r² =0.32, P<0.05); and between muscle strength and FEV1 in females (r² =0.20, P<0.05). INTERPRETATION & CONCLUSION: The study showed that the handgrip muscle strength decreases as the FVC and FEV1 decrease in patients with COPD. Identifying those patients who have reduced strength and endurance will allow early interventions targeted at improving the quality of life of the patient.

Five Cases of Idiopathic Sciatic Mononeuropathy: Clinical, Electrophysiological, Radiological, and Histological Features.

Background: Common etiologies of sciatic mononeuropathy are compressive, infiltrative, traumatic, or diabetic. However, in a proportion of patients, the etiology remains elusive despite extensive serological, electrophysiological, radiological, and histological investigations. Methods: Patients with unexplained sciatic mononeuropathy were studied with regard to their clinical, radiological, pathological, and treatment aspects. Results: We could identify five cases of sciatic mononeuropathy wherein the etiology remained unknown even after a comprehensive evaluation. The compressive, metabolic, hematological, and immune causes were ruled out with necessary investigations. The clinical, electrophysiological, radiological, and histological features of these patients are discussed. Conclusion: The etiology of sciatic mononeuropathy can remain obscure in certain instances in spite of the comprehensive workup. The role of investigations and the exclusion process of various diagnostic entities are discussed.

The other side of the story: Intended parents' surrogacy journeys, stigma and relational reproductive justice.

Current surrogacy research primarily focuses on commercial surrogacy with a particular emphasis on experiences of surrogate mothers, whereas intended parents' voices are dominated by western perspectives. Indigenous voices are only a whisper. This study presents another side of the surrogacy story by including the voices of intended parents residing in India, elicited through eight in-depth interviews. We assert there is need to understand Indian intended parents' socio-spatial experiences in the presence of a changing surrogacy law in India and the socio-cultural importance of childbearing and parenthood to move towards relational reproductive justice. By recognising the relational nature of surrogacy reproduction and drawing on the concepts of ethics of care in light of power and stigma discussions, this paper demonstrates how stigma is experienced by intended parents, its effect on their reproductive journey and wellbeing, as well as how stigma hinders achieving the vision of relational reproductive justice. We suggest that, in order to make surrogacy a positive experience for the people involved in surrogacy, there is a need to address stigma and view surrogacy as a relationship.

Assessing organ-level immunoreactivity in a rat model of sepsis using TSPO PET imaging.

There is current need for new approaches to assess/measure organ-level immunoreactivity and ensuing dysfunction in systemic inflammatory response syndrome (SIRS) and sepsis, in order to protect or recover organ function. Using a rat model of systemic sterile inflammatory shock (intravenous LPS administration), we performed PET imaging with a translocator protein (TSPO) tracer, [18F]DPA-714, as a biomarker for reactive immunoreactive changes in the brain and peripheral organs. In vivo dynamic PET/CT scans showed increased [18F]DPA-714 binding in the brain, lungs, liver and bone marrow, 4 hours after LPS injection. Post-LPS mean standard uptake values (SUVmean) at equilibrium were significantly higher in those organs compared to baseline. Changes in spleen [18F]DPA-714 binding were variable but generally decreased after LPS. SUVmean values in all organs, except the spleen, positively correlated with several serum cytokines/chemokines. In vitro measures of TSPO expression and immunofluorescent staining validated the imaging results. Noninvasive molecular imaging with [18F]DPA-714 PET in a rat model of systemic sterile inflammatory shock, along with in vitro measures of TSPO expression, showed brain, liver and lung inflammation, spleen monocytic efflux/lymphocytic activation and suggested increased bone marrow hematopoiesis. TSPO PET imaging can potentially be used to quantify SIRS and sepsis-associated organ-level immunoreactivity and assess the effectiveness of therapeutic and preventative approaches for associated organ failures, in vivo.

Monitoring Immune Activation with Whole-Body Fluorodeoxyglucose-Positron-Emission Tomography in Simian Immunodeficiency Virus-Infected Rhesus Macaques.

This study aimed to assess immune activation in tissues by measuring glucose metabolism with 18F-fluorodeoxyglucose (FDG) and investigate the associations of various peripheral markers of disease progression with initiation and interruption of combination antiretroviral therapy in SIV-infected rhesus macaques (Macaca mulatta). Mixed-effect linear models revealed a significant inverse association of peripheral blood CD4+ T cell counts (p < 0.01) and a direct association of plasma viral load (p < 0.01) with the FDG uptake in the spleen, bone marrow, and most clusters of lymph nodes. In contrast, no significant associations were found for the liver and the bowel FDG uptake. We also found no association of the fraction of proliferating peripheral blood T and B lymphocytes with FDG uptake in any analyzed tissues. The bowel FDG uptake of uninfected animals was heterogeneous and reached levels as high as those seen in the bowel or the clusters of lymph nodes or the spleen of high viremic SIV-infected animals, suggesting that factors beyond SIV-induced immune activation dominate the gut FDG uptake.

Evaluation of 2-[18F]-Fluorodeoxysorbitol PET Imaging in Preclinical Models of Aspergillus Infection.

Despite increasing associated mortality and morbidity, the diagnosis of fungal infections, especially with Aspergillus fumigatus (A. fumigatus), remains challenging. Based on known ability of Aspergillus species to utilize sorbitol, we evaluated 2-[18F]-fluorodeoxysorbitol (FDS), a recently described Enterobacterales imaging ligand, in animal models of A. fumigatus infection, in comparison with 2-[18F]-fluorodeoxyglucose (FDG). In vitro assays showed slightly higher 3H-sorbitol uptake by live compared with heat-killed A. fumigatus. However, this was 10.6-fold lower than E. coli uptake. FDS positron emission tomography (PET) imaging of A. fumigatus pneumonia showed low uptake in infected lungs compared with FDG (0.290 ± 0.030 vs. 8.416 ± 0.964 %ID/mL). This uptake was higher than controls (0.098 ± 0.008 %ID/mL) and minimally higher than lung inflammation (0.167 ± 0.007 %ID/mL). In the myositis models, FDS uptake was highest in live E. coli infections. Uptake was low in A. fumigatus myositis model and only slightly higher in live compared with the heat-killed side. In conclusion, we found low uptake of 3H-sorbitol and FDS by A. fumigatus cultures and infection models compared with E. coli, likely due to the need for induction of sorbitol dehydrogenase by sorbitol. Our findings do not support FDS as an Aspergillus imaging agent. At this point, FDS remains more selective for imaging Gram-negative Enterobacterales.