Increased Metabolic Activity on 18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography in Human Immunodeficiency Virus-Associated Immune Reconstitution Inflammatory Syndrome

Activation of the JNK/COX-2/HIF-1α axis promotes M1 macrophage via glycolytic shift in HIV-1 infection

Chronic inflammation is recognized as a major risk factor for the severity of HIV infection. Whether metabolism reprogramming of macrophages caused by HIV-1 is related to chronic inflammatory activation, especially M1 polarization of macrophages, is inconclusive. Here, we show that HIV-1 infection induces M1 polarization and enhanced glycolysis in macrophages. Blockade of glycolysis inhibits M1 polarization of macrophages, indicating that HIV-1-induced M1 polarization is supported by enhanced glycolysis. Moreover, we find that this immunometabolic adaptation is dependent on hypoxia-inducible factor 1α (HIF-1α), a strong inducer of glycolysis. HIF-1α-target genes, including HK2, PDK1, and LDHA, are also involved in this process. Further research discovers that COX-2 regulates HIF-1α-dependent glycolysis. However, the elevated expression of COX-2, enhanced glycolysis, and M1 polarization of macrophages could be reversed by inactivation of JNK in the context of HIV-1 infection. Our study mechanistically elucidates that the JNK/COX-2/HIF-1α axis is activated to strengthen glycolysis, thereby promoting M1 polarization in macrophages in HIV-1 infection, providing a new idea for resolving chronic inflammation in clinical AIDS patients.

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.

Molecular Imaging of Tuberculosis

Despite the introduction of many novel diagnostic techniques and newer treatment agents, tuberculosis (TB) remains a major cause of death from an infectious disease worldwide. With about a quarter of humanity harboring Mycobacterium tuberculosis, the causative agent of TB, the current efforts geared towards reducing the scourge due to TB must be sustained. At the same time, newer alternative modalities for diagnosis and treatment response assessment are considered. Molecular imaging entails the use of radioactive probes that exploit molecular targets expressed by microbes or human cells for imaging using hybrid scanners that provide both anatomic and functional features of the disease being imaged. Fluorine-18 fluorodeoxyglucose (FDG) is the most investigated radioactive probe for TB imaging in research and clinical practice. When imaged with positron emission tomography interphase with computed tomography (PET/CT), FDG PET/CT performs better than sputum conversion for predicting treatment outcome. At the end of treatment, FDG PET/CT has demonstrated the unique ability to identify a subset of patients declared cured based on the current standard of care but who still harbor live bacilli capable of causing disease relapse after therapy discontinuation. Our understanding of the pathogenesis and evolution of TB has improved significantly in the last decade, owing to the introduction of FDG PET/CT in TB research. FDG is a non-specific probe as it targets the host inflammatory response to Mycobacterium tuberculosis, which is not specifically different in TB compared with other infectious conditions. Ongoing efforts are geared towards evaluating the utility of newer probes targeting different components of the TB granuloma, the hallmark of TB lesions, including hypoxia, neovascularization, and fibrosis, in TB management. The most exciting category of non-FDG PET probes developed for molecular imaging of TB appears to be radiolabeled anti-tuberculous drugs for use in studying the pharmacokinetic characteristics of the drugs. This allows for the non-invasive study of drug kinetics in different body compartments concurrently, providing an insight into the spatial heterogeneity of drug exposure in different TB lesions. The ability to repeat molecular imaging using radiolabeled anti-tuberculous agents also offers an opportunity to study the temporal changes in drug kinetics within the different lesions during treatment.

Does 18F-FDG PET/CT add value to conventional imaging in clinical assessment of chronic disseminated candidiasis?

Background

Chronic disseminated candidiasis (CDC) classically occurs after profound and prolonged neutropenia. The aim of the CANHPARI study was to assess the clinical value of adding ¹⁸F-fluorodeoxyglucose PET/CT to conventional radiology for initial and subsequent evaluations of CDC.

Materials and methods

A pilot prospective study was conducted in 23 French onco-hematological centers from 2013 to 2017 (NCT01916057). Patients ≥ 18 y.o. suspected for CDC on abdominal conventional imaging (CT or MRI) were included. PET/CT and conventional imaging were performed at baseline and month 3 (M3). Follow-up was assessed until M12. The primary outcome measure was the global response at M3, i.e., apyrexia and complete response to PET/CT. The secondary outcome measure consists in comparison between responses to PET/CT and conventional imaging at diagnosis and M3.

Results

Among 52 included patients, 44 were evaluable (20 probable and 24 possible CDC); 86% had acute leukemia, 55% were male (median age 47 years). At diagnosis, 34% had fever and conventional imaging was always abnormal with microabscesses on liver and spleen in 66%, liver in 25%, spleen in 9%. Baseline PET/CT showed metabolic uptake on liver and/or spleen in 84% but did not match with lesion localizations on conventional imaging in 32%. M3 PET/CT showed no metabolic uptake in 13 (34%) patients, 11 still having pathological conventional imaging. Global response at M3 was observed in eight patients.

Conclusion

Baseline PET/CT does not replace conventional imaging for initial staging of CDC lesions but should be performed after 3 months of antifungal therapy.

Clinical trial registration

[www.clinicaltrials.gov], identifier [NCT01916057].

Improvement of liver metabolic activity in people with advanced HIV after antiretroviral therapy initiation

OBJECTIVE

Evaluating hepatic metabolic changes in people with HIV (PWH) with advanced disease, before and after antiretroviral therapy (ART) initiation, using [ 18 F]-fluorodeoxyglucose (FDG) PET-computed tomography (PET/CT). FDG PET/CT noninvasively quantifies glucose metabolism in organs.

DESIGN/METHODS

Forty-eight viremic PWH (CD4 + cell counts <100 cells/μl) underwent FDG PET/CT at baseline and approximately 6 weeks after ART initiation (short-term). Twenty-seven PWH participants underwent follow-up scans 2 years after treatment (long-term). FDG PET/CT scans from 20 healthy controls were used for comparison. Liver FDG uptake was quantified from the PET/CT scans. Imaging findings as well as clinical, laboratory, and immune markers were compared longitudinally and cross-sectionally to healthy controls.

RESULTS

Liver FDG uptake was lower at baseline and short-term in PWH compared with controls ( P  < 0.0001). At the long-term scan, liver FDG uptake of PWH increased relative to baseline and short-term ( P  = 0.0083 and 0.0052) but remained lower than controls' values ( P  = 0.004). Changes in FDG uptake correlated negatively with levels of glucagon, myeloperoxidase, sCD14, and MCP-1 and positively with markers of recovery (BMI, albumin, and CD4 + cell counts) ( P  < 0.01). In multivariable analyses of PWH values across timepoints, BMI and glucagon were the best set of predictors for liver FDG uptake ( P  < 0.0001).

CONCLUSION

Using FDG PET/CT, we found decreased liver glucose metabolism in PWH that could reflect hepatocytes/lymphocytes/myeloid cell loss and metabolic dysfunction because of inflammation. Although long-term ART seems to reverse many hepatic abnormalities, residual liver injury may still exist within 2 years of treatment initiation, especially in PWH who present with low nadir CD4 + cell counts.

Imaging and biopsy of HIV-infected individuals undergoing analytic treatment interruption

Background

HIV persistence during antiretroviral therapy (ART) is the principal obstacle to cure. Lymphoid tissue is a compartment for HIV, but mechanisms of persistence during ART and viral rebound when ART is interrupted are inadequately understood. Metabolic activity in lymphoid tissue of patients on long-term ART is relatively low, and increases when ART is stopped. Increases in metabolic activity can be detected by ¹⁸F-fluorodeoxyglucose Positron Emission Tomography (FDG-PET) and may represent sites of HIV replication or immune activation in response to HIV replication.

Methods

FDG-PET imaging will be used to identify areas of high and low metabolic uptake in lymphoid tissue of individuals undergoing long-term ART. Baseline tissue samples will be collected. Participants will then be randomized 1:1 to continue or interrupt ART via analytic treatment interruption (ATI). Image-guided biopsy will be repeated 10 days after ATI initiation. After ART restart criteria are met, image-guided biopsy will be repeated once viral suppression is re-achieved. Participants who continued ART will have a second FDG-PET and biopsies 12–16 weeks after the first. Genetic characteristics of HIV populations in areas of high and low FDG uptake will be assesed. Optional assessments of non-lymphoid anatomic compartments may be performed to evaluate HIV populations in distinct anatomic compartments.

Anticipated results

We anticipate that PET standardized uptake values (SUV) will correlate with HIV viral RNA in biopsies of those regions and that lymph nodes with high SUV will have more viral RNA than those with low SUV within a patient. Individuals who undergo ATI are expected to have diverse viral populations upon viral rebound in lymphoid tissue. HIV populations in tissues may initially be phylogenetically diverse after ATI, with emergence of dominant viral species (clone) over time in plasma. Dominant viral species may represent the same HIV population seen before ATI.

Discussion

This study will allow us to explore utility of PET for identification of HIV infected cells and determine whether high FDG uptake respresents areas of HIV replication, immune activation or both. We will also characterize HIV infected cell populations in different anatomic locations. The protocol will represent a platform to investigate persistence and agents that may target HIV populations.

Study protocol registration

Identifier: NCT05419024.

Image-guided/improved diseases management: From immune-strategies and beyond

Timely and accurate assessment and diagnosis are extremely important and beneficial for all diseases, especially for some of the major human disease, such as cancers, cardiovascular diseases, infectious diseases, and neurodegenerative diseases. Limited by the variable disease microenvironment, early imperceptible symptoms, complex immune system interactions, and delayed clinical phenotypes, disease diagnosis and treatment are difficult in most cases. Molecular imaging (MI) techniques can track therapeutic drugs and disease sites in vivo and in vitro in a non-invasive, real-time and visible strategies. Comprehensive visual imaging and quantitative analysis based on different levels can help to clarify the disease process, pathogenesis, drug pharmacokinetics, and further evaluate the therapeutic effects. This review summarizes the application of different MI techniques in the diagnosis and treatment of these major human diseases. It is hoped to shed a light on the development of related technologies and fields.

Biotypes of HIV-associated neurocognitive disorders based on viral and immune pathogenesis

PURPOSE OF REVIEW

HIV-associated neurocognitive disorders (HAND) continues to be prevalent in people living with HIV despite antiretroviral therapy. However, understanding disease mechanisms and identifying therapeutic avenues has been challenging. One of the challenges is that HAND is a heterogeneous disease and that patients identified with similar impairments phenotypically may have very different underlying disease processes. As the NeuroAIDS field is re-evaluating the approaches used to identify patients with HIV-associated neurological impairments, we propose the subtyping of patients into biotypes based on viral and immune pathogenesis.

RECENT FINDINGS

Here we review the evidence supporting subtyping patients with HIV-associated neurological complications into four biotypes: macrophage-mediated HIV encephalitis, CNS viral escape, T-cell-mediated HIV encephalitis, and HIV protein-associated encephalopathy.

SUMMARY

Subtyping patients into subgroups based on biotypes has emerged as a useful approach for studying heterogeneous diseases. Understanding biotypes of HIV-associated neurocognitive impairments may therefore enable better understanding of disease mechanisms, allow for the development of prognostic and diagnostic markers, and could ultimately guide therapeutic decisions.

Updates in the Impact of Chronic Systemic Inflammation on Vascular Inflammation by Positron Emission Tomography (PET)

PURPOSE OF REVIEW

In this review, we focus on the clinical and epidemiological studies pertaining to systemic and vascular inflammation by positron emission tomography (PET) in patients with chronic inflammatory conditions such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), human immunodeficiency virus (HIV), and psoriasis to highlight the importance of chronic systemic inflammation on vascular inflammation by PET in these disease states.

RECENT FINDINGS

Recent clinical and translation advancements have demonstrated the durable relationship between chronic systemic inflammation and cardiovascular disease (CVD). In chronic inflammatory states, this relationship is robustly evident in the form of increased vascular inflammation, yet traditional risk estimates often underestimate the subclinical cardiovascular risk conferred by chronic inflammation. PET has emerged as a novel, non-invasive imaging modality capable of both quantifying the degree of systemic and vascular inflammation and detecting residual inflammation prior to cardiovascular events. We begin by demonstrating the role of inflammation in the pathogenesis of atherosclerosis, discussing how PET has been utilized to measure systemic and vascular inflammation and their effect on subclinical atherosclerosis, and finally reviewing recent applications of PET in constructing improved risk stratification for patients at high risk for stroke and CVD.

Persistent Oxidative Stress and Inflammasome Activation in CD14highCD16- Monocytes From COVID-19 Patients

The poor outcome of the coronavirus disease-2019 (COVID-19), caused by SARS-CoV-2, is associated with systemic hyperinflammatory response and immunopathology. Although inflammasome and oxidative stress have independently been implicated in COVID-19, it is poorly understood whether these two pathways cooperatively contribute to disease severity. Herein, we found an enrichment of CD14highCD16- monocytes displaying inflammasome activation evidenced by caspase-1/ASC-speck formation in severe COVID-19 patients when compared to mild ones and healthy controls, respectively. Those cells also showed aberrant levels of mitochondrial superoxide and lipid peroxidation, both hallmarks of the oxidative stress response, which strongly correlated with caspase-1 activity. In addition, we found that NLRP3 inflammasome-derived IL-1β secretion by SARS-CoV-2-exposed monocytes in vitro was partially dependent on lipid peroxidation. Importantly, altered inflammasome and stress responses persisted after short-term patient recovery. Collectively, our findings suggest oxidative stress/NLRP3 signaling pathway as a potential target for host-directed therapy to mitigate early COVID-19 hyperinflammation and also its long-term outcomes.

Redistribution of brain glucose metabolism in people with HIV after antiretroviral therapy initiation

OBJECTIVE

We evaluated brain glucose metabolism in people living with HIV (PWH) with [18F]-Fluoro-Deoxyglucose (FDG) PET/computed tomography (CT) before and after antiretroviral therapy (ART) initiation.

DESIGN

We conducted a longitudinal study wherein ART-naive late-presenting untreated PWH with CD4+ cell counts less than 100 cells/μl were prospectively assessed for FDG uptake at baseline and at 4-8 weeks (n = 22) and 19-26 months (n = 11) following ART initiation.

METHODS

Relative uptake in the subcortical regions (caudate, putamen and thalamus) and cortical regions (frontal, parietal, temporal and occipital cortices) were compared across time and correlated with biomarkers of disease activity and inflammation, in addition to being compared with a group of uninfected individuals (n = 10).

RESULTS

Before treatment initiation, putaminal and caudate relative FDG uptake values in PWH were significantly higher than in uninfected controls. Relative putaminal and thalamic uptake significantly decreased shortly following ART initiation, while frontal cortex values significantly increased. FDG uptake changes correlated with changes in CD4+ cell counts and viral load, and, in the thalamus, with IL-6R and sCD14. Approximately 2 years following ART initiation, there was further decrease in subcortical relative uptake values, reaching levels below those of uninfected controls.

CONCLUSION

Our findings support pretreatment basal ganglia and thalamic neuroinflammatory changes in PWH, which decrease after treatment with eventual unmasking of long-term irreversible neuronal damage. Meanwhile, increased frontal cortex metabolism following ART initiation suggests reversible cortical dysfunction which improves with virologic control and increased CD4+ cell counts. Early initiation of treatment after HIV diagnosis and secondary control of inflammation are thus necessary to halt neurological damage in PWH.

Plasma Metabolomics Reveals Dysregulated Metabolic Signatures in HIV-Associated Immune Reconstitution Inflammatory Syndrome

Immune reconstitution inflammatory syndrome (IRIS) is an inflammatory complication associated with an underlying opportunistic infection that can be observed in HIV-infected individuals shortly after the initiation of antiretroviral therapy, despite successful suppression of HIV viral load and CD4⁺ T cell recovery. Better understanding of IRIS pathogenesis would allow for targeted prevention and therapeutic approaches. In this study, we sought to evaluate the metabolic perturbations in IRIS across longitudinal time points using an unbiased plasma metabolomics approach as well as integrated analyses to include plasma inflammatory biomarker profile and whole blood transcriptome. We found that many lipid and amino acid metabolites differentiated IRIS from non-IRIS conditions prior to antiretroviral therapy and during the IRIS event, implicating the association between oxidative stress, tryptophan pathway, and lipid mediated signaling and the development of IRIS. Lipid and amino acid metabolic pathways also significantly correlated with inflammatory biomarkers such as IL-12p70 and IL-8 at the IRIS event, indicating the role of cellular metabolism on cell type specific immune activation during the IRIS episode and in turn the impact of immune activation on cellular metabolism. In conclusion, we defined the metabolic profile of IRIS and revealed that perturbations in metabolism may predispose HIV-infected individuals to IRIS development and contribute to the inflammatory manifestations during the IRIS event. Furthermore, our findings expanded our current understanding IRIS pathogenesis and highlighted the significance of lipid and amino acid metabolism in inflammatory complications.

Lung Injury on Antiretroviral Therapy in Adults With Human Immunodeficiency Virus/Tuberculosis

BACKGROUND

Immune restoration on antiretroviral therapy (ART) can drive inflammation in people living with human immunodeficiency virus (HIV) who have pulmonary tuberculosis (TB), but its effects on the lungs have not been assessed. We evaluated associations between pulmonary inflammation, recovery of pathogen-specific CD4 T-cell function, and lung injury prior to and after ART initiation in adults with HIV and pulmonary TB.

METHODS

This was a prospective cohort study in South Africa, following adults with HIV and pulmonary TB prior to and up to 48 weeks after ART initiation. Pulmonary-specific inflammation was defined as total glycolytic activity (TGA) on [18]F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) at baseline and 4 weeks after ART initiation. Spirometry, respiratory symptom tests, and flow cytometry were performed at the same times to assess lung involvement and the frequency of mycobacteria-specific CD4 T-cells. In addition, we evaluated lung function longitudinally up to 48 weeks after ART initiation.

RESULTS

Greater lung TGA on FDG PET-CT was associated with worse lung function and respiratory symptoms prior to ART initiation, and nearly half of subjects experienced worsening lung inflammation and lung function at Week 4 of ART. Worsening Week 4 lung inflammation and pulmonary function were both associated with greater increases in pathogen-specific functional CD4 T-cell responses on ART, and early decreases in lung function were independently associated with persistently lower lung function months after TB treatment completion.

CONCLUSIONS

Increases in pulmonary inflammation and decreases in lung function are common on ART, relate to greater ART-mediated CD4 T-cell restoration, and are associated with the persistent impairment of lung function in individuals with HIV/TB.

State of the art of 18F-FDG PET/CT application in inflammation and infection: a guide for image acquisition and interpretation

AIM

The diagnosis, severity and extent of a sterile inflammation or a septic infection could be challenging since there is not one single test able to achieve an accurate diagnosis. The clinical use of 18F-fluorodeoxyglucose ([¹⁸F]FDG) positron emission tomography/computed tomography (PET/CT) imaging in the assessment of inflammation and infection is increasing worldwide. The purpose of this paper is to achieve an Italian consensus document on [¹⁸F]FDG PET/CT or PET/MRI in inflammatory and infectious diseases, such as osteomyelitis (OM), prosthetic joint infections (PJI), infective endocarditis (IE), prosthetic valve endocarditis (PVE), cardiac implantable electronic device infections (CIEDI), systemic and cardiac sarcoidosis (SS/CS), diabetic foot (DF), fungal infections (FI), tuberculosis (TBC), fever and inflammation of unknown origin (FUO/IUO), pediatric infections (PI), inflammatory bowel diseases (IBD), spine infections (SI), vascular graft infections (VGI), large vessel vasculitis (LVV), retroperitoneal fibrosis (RF) and COVID-19 infections.

METHODS

In September 2020, the inflammatory and infectious diseases focus group (IIFG) of the Italian Association of Nuclear Medicine (AIMN) proposed to realize a procedural paper about the clinical applications of [¹⁸F]FDG PET/CT or PET/MRI in inflammatory and infectious diseases. The project was carried out thanks to the collaboration of 13 Italian nuclear medicine centers, with a consolidate experience in this field. With the endorsement of AIMN, IIFG contacted each center, and the pediatric diseases focus group (PDFC). IIFG provided for each team involved, a draft with essential information regarding the execution of [¹⁸F]FDG PET/CT or PET/MRI scan (i.e., indications, patient preparation, standard or specific acquisition modalities, interpretation criteria, reporting methods, pitfalls and artifacts), by limiting the literature research to the last 20 years. Moreover, some clinical cases were required from each center, to underline the teaching points. Time for the collection of each report was from October to December 2020.

RESULTS

Overall, we summarized 291 scientific papers and guidelines published between 1998 and 2021. Papers were divided in several sub-topics and summarized in the following paragraphs: clinical indications, image interpretation criteria, future perspectivess and new trends (for each single disease), while patient preparation, image acquisition, possible pitfalls and reporting modalities were described afterwards. Moreover, a specific section was dedicated to pediatric and PET/MRI indications. A collection of images was described for each indication.

CONCLUSIONS

Currently, [¹⁸F]FDG PET/CT in oncology is globally accepted and standardized in main diagnostic algorithms for neoplasms. In recent years, the ever-closer collaboration among different European associations has tried to overcome the absence of a standardization also in the field of inflammation and infections. The collaboration of several nuclear medicine centers with a long experience in this field, as well as among different AIMN focus groups represents a further attempt in this direction. We hope that this document will be the basis for a "common nuclear physicians' language" throughout all the country.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40336-021-00445-w.

Disseminated Mycobacterium marinum in Human Immunodeficiency Virus Unmasked by Immune Reconstitution Inflammatory Syndrome

Distinguishing disseminated Mycobacterium marinum from multifocal cutaneous disease in persons with human immunodeficiency virus/AIDS can present a diagnostic challenge, especially in the context of immune reconstitution inflammatory syndrome (IRIS). In this work, we demonstrate the utility of flow cytometry and whole genome sequencing (WGS) to diagnose disseminated M. marinum unmasked by IRIS following initiation of antiretroviral therapy. Flow cytometry demonstrated robust cytokine production by CD4 T cells in response to stimulation with M. marinum lysate. WGS of isolates from distinct lesions was consistent with clonal dissemination, supporting that preexisting disseminated M. marinum disease was uncovered by inflammatory manifestations, consistent with unmasking mycobacterial IRIS.

Immunometabolism and HIV-1 pathogenesis: food for thought

Antiretroviral therapies efficiently block HIV-1 replication but need to be maintained for life. Moreover, chronic inflammation is a hallmark of HIV-1 infection that persists despite treatment. There is, therefore, an urgent need to better understand the mechanisms driving HIV-1 pathogenesis and to identify new targets for therapeutic intervention. In the past few years, the decisive role of cellular metabolism in the fate and activity of immune cells has been uncovered, as well as its impact on the outcome of infectious diseases. Emerging evidence suggests that immunometabolism has a key role in HIV-1 pathogenesis. The metabolic pathways of CD4⁺ T cells and macrophages determine their susceptibility to infection, the persistence of infected cells and the establishment of latency. Immunometabolism also shapes immune responses against HIV-1, and cell metabolic products are key drivers of inflammation during infection. In this Review, we summarize current knowledge of the links between HIV-1 infection and immunometabolism, and we discuss the potential opportunities and challenges for therapeutic interventions.

PET/CT and PET/MRI in ophthalmic oncology (Review)

Orbital and ocular anatomy is quite complex, consisting of several tissues, which can give rise to both benign and malignant tumors, while several primary neoplasms can metastasize to the orbital and ocular space. Early detection, accurate staging and re-staging, efficient monitoring of treatment response, non-invasive differentiation between benign and malignant lesions, and accurate planning of external radiation treatment, are of utmost importance for the optimal and individualized management of ophthalmic oncology patients. Addressing these challenges requires the employment of several diagnostic imaging techniques, such as high-definition digital fundus photography, ultrasound imaging, optical coherence tomography, optical coherence tomography (OCT)-angiography, computed tomography (CT) and magnetic resonance imaging (MRI). In recent years, technological advances have enabled the development of hybrid positron emission tomography (PET)/CT and PET/MRI systems, setting new standards in cancer diagnosis and treatment. The capability of simultaneously targeting several cancer-related biochemical procedures using positron emitting-radiopharmaceuticals, while morphologically characterizing lesions by CT or MRI, together with the intrinsic quantitative capabilities of PET-imaging, provide incremental diagnostic information, enabling accurate, highly efficient and personalized treatment strategies. Aim of the current review is to discuss the current applications of hybrid PET/CT and PET/MRI imaging in the management of patients presenting with the most commonly encountered orbital and ocular tumors.

Immune reconstruction inflammatory syndrome in HIV infection: beyond what meets the eye

A high proportion of individuals with HIV infection currently are diagnosed at an advanced stage of disease (late presenters), increasing their risk for immune reconstitution inflammatory syndrome (IRIS). IRIS typically occurs within 6 months of initiation of antiretroviral therapy (ART) in patients with low CD4+ cell counts and can occur before any marked elevation in CD4+ count is achieved on ART. In addition to low CD4+ count at ART initiation, 2 other major clinical predictors of IRIS are preexisting opportunistic infection (including subclinical infection) and shorter treatment period for opportunistic infection prior to starting ART. Mycobacterial infection-associated IRIS, including tuberculosis (TB)-associated IRIS, and cryptococcal infection-associated IRIS are the most common forms of the syndrome. Corticosteroid prophylaxis and early treatment can be effective in reducing incidence of TB-IRIS and severity of symptoms in select patients. Sterilization of the cerebrospinal fluid should be achieved prior to starting ART in patients with TB meningitis and cryptococcal meningitis. This article summarizes a presentation by Irini Sereti, MD, MHS, at the International Antiviral Society-USA (IAS-USA) continuing education program held in Washington, DC, in April 2019.

Molecular Imaging: a Novel Tool To Visualize Pathogenesis of Infections In Situ

Molecular imaging is an emerging technology that enables the noninvasive visualization, characterization, and quantification of molecular events within living subjects. Positron emission tomography (PET) is a clinically available molecular imaging tool with significant potential to study pathogenesis of infections in humans.

Molecular imaging is an emerging technology that enables the noninvasive visualization, characterization, and quantification of molecular events within living subjects. Positron emission tomography (PET) is a clinically available molecular imaging tool with significant potential to study pathogenesis of infections in humans. PET enables dynamic assessment of infectious processes within the same subject with high temporal and spatial resolution and obviates the need for invasive tissue sampling, which is difficult in patients and generally limited to a single time point, even in animal models. This review presents current state-of-the-art concepts on the application of molecular imaging for infectious diseases and details how PET imaging can facilitate novel insights into infectious processes, ongoing development of pathogen-specific imaging, and simultaneous in situ measurements of intralesional antimicrobial pharmacokinetics in multiple compartments, including privileged sites. Finally, the potential clinical applications of this promising technology are also discussed.

Subclinical Atherosclerosis Imaging in People Living with HIV

In many, but not all studies, people living with HIV (PLWH) have an increased risk of coronary artery disease (CAD) events compared to the general population. This has generated considerable interest in the early, non-invasive detection of asymptomatic (subclinical) atherosclerosis in PLWH. Ultrasound studies assessing carotid artery intima-media thickness (CIMT) have tended to show a somewhat greater thickness in HIV+ compared to HIV-, likely due to an increased prevalence of cardiovascular (CV) risk factors in PLWH. Coronary artery calcification (CAC) determination by non-contrast computed tomography (CT) seems promising to predict CV events but is limited to the detection of calcified plaque. Coronary CT angiography (CCTA) detects calcified and non-calcified plaque and predicts CAD better than either CAC or CIMT. A normal CCTA predicts survival free of CV events over a very long time-span. Research imaging techniques, including black-blood magnetic resonance imaging of the vessel wall and 18F-fluorodeoxyglucose positron emission tomography for the assessment of arterial inflammation have provided insights into the prevalence of HIV-vasculopathy and associated risk factors, but their clinical applicability remains limited. Therefore, CCTA currently appears as the most promising cardiac imaging modality in PLWH for the evaluation of suspected CAD, particularly in patients <50 years, in whom most atherosclerotic coronary lesions are non-calcified.

Management of Advanced HIV Disease

Great progress has been made in caring for persons with human immunodeficiency virus. However, a significant proportion of individuals still present to care with advanced disease and a low CD4 count. Careful considerations for selection of antiretroviral therapy as well as close monitoring for opportunistic infections and immune reconstitution inflammatory syndrome are vitally important in providing care for such individuals.

Splenic infarction complicated with immune reconstitution inflammatory syndrome due to disseminated Mycobacterium genavense infection in a patient infected with human immunodeficiency virus

Mycobacterium genavense (M. genavense) is one of the most fastidious, difficult to culture Mycobacterium species. Patients infected with human immunodeficiency virus (HIV) may develop immune reconstitution inflammatory syndrome (IRIS) due to disseminated M. genavense infection as well as disseminated M. avium and intracellulare complex infection. Consensus regarding treatment of IRIS due to disseminated mycobacterium infection has not yet been obtained, although systemic steroid therapy has been recommended in recent guidelines. Here we report the case of a 48-year-old Japanese man diagnosed with HIV and disseminated M. genavense infection. His initial CD4-positive T cell count was 3/μL, and his HIV1-RNA viral load was 13,000 copies/mL. He developed IRIS due to disseminated M. genavense infection after two weeks of receiving antiretroviral agents. The patient's serum alkaline phosphatase level, as a barometer of disseminated M. genavense infection in this case, was difficult to control with several anti-mycobacterial agents, although his fever was improved by non-steroidal anti-inflammatory drugs. About five weeks after the onset of IRIS, the patient developed acute left upper quadrant pain and was diagnosed with splenic infarction by contrast-enhanced computed tomography. After the splenic infarction, the patient's serum alkaline phosphatase level decreased without systemic steroid therapy or anticoagulant agents, and his left upper quadrant pain improved naturally within a few days. This case suggests that IRIS due to disseminated M. genavense infection can complicate splenic infarction in patients with HIV, and splenic infarction could improve the IRIS due to disseminated M. genavense infection.