Candida lusitaniae, an Emerging Opportunistic Pathogen in Immunocompetent Populations: A Case Report

Candida lusitaniae is an emerging opportunistic pathogen in immunocompromised hosts and hospitalized patients. However, the incidence is low in immunocompetent hosts. Because of their characteristic similarities, C. lusitaniae may be confused with other fungal species, such as Candida tropicalis, Candida parapsilosis, and even Saccharomyces cerevisiae. Recently reported cases of serious infections caused by C. lusitaniae have proven detrimental, and some cases reported amphotericin resistance. Here, we present a case report of empyema caused by C. lusitaniae in an immunocompetent patient who was admitted to the intensive care unit and intubated for acute hypoxic respiratory failure. This case demonstrates the importance of recognizing this organism and initiating early treatment for the prevention of fatal complications.

A score for predicting invasive pulmonary aspergillosis in immunocompetent critically ill patients

BACKGROUND

Delayed treatment leads to increased mortality in critically ill patients with invasive pulmonary aspergillosis (IPA). We aimed to develop and validate a prediction score based on novel biomarkers and clinical risk factors to identify IPA in immunocompetent patients in the intensive care unit (ICU).

METHODS

A retrospective study was conducted to collect medical information and novel biomarkers upon ICU admission. Risk factors adopted for the final prediction score were identified using multivariate logistic regression analysis.

RESULTS

We retrospectively collected 1841 critical ill patients between January 2018 and August 2022. Patients with IPA had higher C-reactive protein-to-albumin ratio (CAR), neutrophil-to-lymphocyte ratio, systemic immune-inflammation index and lower prognostic nutritional index (PNI). Chronic obstructive pulmonary disease (COPD), continuous renal replacement therapy (CRRT), high dose of corticosteroids, broad-spectrum antibiotics, blood galactomannan (GM) positivity and high CAR were independent risk factors for IPA and were entered into the final prediction score. The score had good discrimination, with the area under receiver operating characteristic curve of 0.816 and 0.780 for the training and validation cohorts, respectively, and good calibration.

CONCLUSION

A score based on six clinical and novel immunological biomarkers showed promising predictive value for antifungal treatment in immunocompetent ICU patients.

Pyogenic Liver Abscess: A Case of a Fussy Bug Seeking Unlikely Host

Pyogenic liver abscesses (PLAs) represent a rare yet life-threatening condition, and Fusobacterium species are an atypical etiology typically associated with immunocompromised patients or those with recent dental procedures or oro-gingival disease. Nonetheless, it is crucial to maintain a high level of suspicion for Fusobacterium infection in all cases, including immunocompetent individuals without known risk factors. In this case report, we present the clinical scenario of a young male with a history of COVID-19 pneumonia who exhibited subacute fever, abdominal pain, and pleuritic chest pain, leading to sepsis attributed to intraabdominal pathology. Subsequent imaging confirmed the presence of possible liver abscesses, prompting interventional radiology-guided drainage. Cultures obtained from the drained abscesses yielded Fusobacterium species, and significant clinical improvement was observed following the initiation of appropriate antibiotic therapy. This case report underscores the potential for disseminated Fusobacterium infections to occur in immunocompetent individuals without a history of oropharyngeal disease, highlighting the importance of early diagnosis and management to mitigate mortality risk.

Outbreak of indeterminate acute liver failure in children with adenoviraemia - Not a new disease

BACKGROUND & AIMS

In the year 2022, an outbreak of indeterminate acute hepatitis and indeterminate paediatric acute liver failure (ID-PALF) in association with adenoviraemia in immunocompetent children was reported in the UK. We postulate that this association is not a new disease in immunocompetent children.

METHODS

Children with acute hepatitis during the outbreak who were referred to King's College Hospital, London for advice and management were included in the study. Data on the frequency of ID-PALF in 2022, as well as transplantation rates and the association with adenovirus infection, were obtained from electronic health records. The clinical presentation, histology and outcomes of children with ID-PALF and adenoviraemia in 2017-2021 were compared with those in 2022.

RESULTS

From January to June 2022, 65 patients with acute hepatitis were referred. Ten children were admitted with ID-PALF. ID-PALF constituted 26% of all PALF cases in 2017-2021, in contrast to 58.8% during the 2022 outbreak. During the outbreak, adenoviraemia was present in 52% of children with acute hepatitis without liver failure (in whom adenoviraemia test results were available) and in 100% of ID-PALF cases. Adenoviraemia was seen in immunocompetent children in 6/13 (46%) of all ID-PALF cases between 2017-2019, with a clear absence of adenoviraemia in the 6 ID-PALF cases during 2020-2021. Compared to ID-PALF with adenoviraemia in 2017-2019 (n = 6), ID-PALF with adenoviraemia during the outbreak (n = 10) was associated with more frequent hepatic encephalopathy, hypotension requiring vasoactive medications and higher plasma ammonia levels (admission and peak), with similar native liver survival.

CONCLUSIONS

The recent outbreak of ID-PALF with adenoviraemia in immunocompetent children does not appear to be a new disease, contrary to perception and other reports. The frequency of such cases over the years could be linked to background rates of adenovirus infections.

IMPACT AND IMPLICATIONS

Indeterminate paediatric acute liver failure (ID-PALF) associated with adenoviraemia in immunocompetent children is not a new disease specific to 2022. The exclusive role of human adenovirus infection in the causation of this outbreak of acute hepatitis seems unlikely. Indeed, we provide histological data from explants in transplanted patients that do not support direct viral cytotoxicity. The disease is probably mediated by immunological injury directed towards adenovirus infection and/or adeno-associated virus-2.

Morphological Diagnosis of Blastomycosis Clinically Presenting as Mycetoma in a Young Immunocompetent Indian Patient; A Diagnostic Dilemma

Primary cutaneous blastomycosis is very rare in non-endemic regions like India. Only few cases have been reported from India. Herein, we are reporting a rare case of chronic cutaneous blastomycosis in a young immunocompetent male presenting as mycetoma with multiple discharging sinuses in the anterior abdominal wall with no significant travel history.

Case Report: Chronic hepatitis E virus Infection in an individual without evidence for immune deficiency

Chronic hepatitis E virus (HEV) infection occurs mainly in immunosuppressed populations. We describe an investigation of chronic HEV infection of genotype 3a in an individual without evidence for immune deficiency who presented hepatitis with significant HEV viremia and viral shedding. We monitored HEV RNA in plasma and stools, and assessed anti-HEV specific immune responses. The patient was without apparent immunodeficiency based on quantified results of white blood cell, lymphocyte, neutrophilic granulocyte, CD3+ T cell, CD4+ T cell, and CD8+ T cell counts and CD4/CD8 ratio, as well as total serum IgG, IgM, and IgA, which were in the normal range. Despite HEV specific cellular response and strong humoral immunity being observed, viral shedding persisted up to 10⁹ IU/mL. After treatment with ribavirin combined with interferon, the indicators of liver function in the patient returned to normal, accompanied by complete suppression and clearance of HEV. These results indicate that HEV chronicity can also occur in individuals without evidence of immunodeficiency.

Multiple Bone Destruction Secondary to Mycobacterium kansasii Pulmonary Disease: A Case Report

Mycobacterium kansasii infections predominantly manifest in immunocompromised people and are primarily responsible for lung disease and systemic disseminated infection. Osteopathy is a rare consequence of M. kansasii infection. Here, we present imaging data from a 44-year-old immunocompetent Chinese woman diagnosed with multiple bone destruction, particularly of the spine, secondary to M. kansasii pulmonary disease, which is easily misdiagnosed. The patient underwent an emergency operation after experiencing unexpected incomplete paraplegia during hospitalization, indicating an aggravation of bone destruction. Preoperative sputum testing and next-generation sequencing of DNA and RNA of intraoperative samples confirmed the diagnosis of M. kansasii infection. Treatment with anti-tuberculosis therapy and the subsequent patient response supported our diagnosis. Given the rarity of osteopathy secondary to M. kansasii infection in immunocompetent individuals, our case offers some insight into this diagnosis.

Aspergilloma in an Immunocompetent Host: A Case Report

Aspergillosis is a serious pathologic condition caused by Aspergillus that commonly affects immunocompromised patients. In recent years, it has been demonstrated that Aspergillus infection can cause a wide spectrum of pulmonary diseases, including allergic bronchopulmonary aspergillosis, chronic necrotizing aspergillosis, aspergilloma, and invasive aspergillosis. The characteristic computed tomography (CT) and pathologic findings of the various pulmonary manifestations of Aspergillus infection are illustrated and reviewed in this case report. Aspergillus niger is an infrequent infection that affects the lungs in severely immunosuppressed patients. In this paper, we report the case of a 50-year-old female with well-controlled type 2 diabetes mellitus who presented to the emergency department with a history of shortness of breath, cough, and weight loss. She denied any use of immunosuppressive medications. High-resolution CT revealed a large right upper lung cavitary lesion, and the sputum examination and bronchoalveolar lavage revealed Aspergillus niger and positive Aspergillus galactomannan. In conclusion, immunocompetent hosts are rarely affected by aspergilloma with lung cavities. We recommend conducting a retrospective data registry on unreported aspergilloma cases in immunocompetent patients to understand the clinicopathological behavior and improve management.

SARS-CoV-2 intrahost evolution in immunocompromised patients in comparison with immunocompetent populations after treatment

Many evidence suggests that long-lasting infection can develop with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This occurrence has been widely described in immunocompromised individuals. In these patients, ineffective clearance of virus infection provides an opportunity for developing immune escape mutants. This study aimed to characterize SARS-CoV-2 intrahost evolution in five immunocompromised in comparison with five immunocompetent COVID-19 patients during treatment. We performed next-generation sequencing (NGS) on collected two oropharyngeal samples from immunocompromised and immunocompetent COVID-19 patients before and after treatment. In this study, we detected alpha and delta variants of SARS-CoV-2. The most common substitutions in structural proteins in patients with alpha variant were S-ΔY143-144, A570D, D614G and D1118H, and N-R203K and G204R, and in delta variant S-T19R, G142D, E156G, 157-158del, L452R, T478K, D614G, D950N and N-D63G, R203M and D377Y were dominant. The common variations in nonstructural and accessory proteins including nsp3-A488S, P1228L, nsp6-T77A, nsp12-P323L, G671S, nsp13-P77L, NS3-S26L, and NS7a-T120I were detected. Also some infrequent substitutions were seen in immunocompromised and immunocompetent patients. After treatment, nsp12-V166A was emerged as a remdesivir resistance and S-L452M in a patient with common variable immunodeficiency. S-E484Q was detected in a patient with acute lymphoma leukemia. This study showed the possibility of the genetic diversity and development of some new mutations in immunocompromised patients. Therefore, surveillance of these patients to characterize any new variants is necessary.

Culture-negative Capnocytophaga canimorsus meningitis diagnosed by 16s ribosomal RNA polymerase chain reaction in an immunocompetent veterinarian and a review of the literature

Capnocytophaga canimorsus is a fastidious, capnophilic and facultative anaerobic Gram-negative rod found commonly in the oral flora of dogs that may cause zoonotic infections such as cellulitis and eye infections. In immunocompromised patients, it may cause fulminant sepsis. Meningitis due to C. canimorsus is, however, a rare manifestation. This is the first reported case of C. canimorsus meningitis in Australia in an immunocompetent veterinarian diagnosed by 16s ribosomal RNA polymerase chain reaction.

Apophysomyces variabilis as an emerging pathogen in Mainland China

BACKGROUND

Mucormycosis is a rare form of invasive, rapidly progressive and lethal opportunistic fungal infection caused by Mucorales. Although Rhizopus arrhizus (R. arrhizus) is the most commonly isolated Mucorales worldwide, infections caused by Apophysomyces variabilis (A. variabilis) are increasing.

OBJECTIVES AND METHODS

We present a case of necrotizing fasciitis caused by A. variabilis in an immunocompetent woman. In order to further understand the characteristics of the strain isolated from the patient, we identified the strain through ITS sequencing, assessed the ability to tolerate salt concentrations and temperature conditions, in addition to performing in vitro drug susceptibility testing against common antifungal agents.

RESULTS

The strain showed 98.76% identity with A. variabilis in the NCBI database, and it was found to tolerate higher temperatures and salt concentrations than previously reported strains. The strain was sensitive to amphotericin B and posaconazole, but not to voriconazole, itraconazole, 5-fluorocytosine and echinocandins.

CONCLUSIONS

This case indicates that Mucorales caused by A. variabilis should be recognised as an emerging pathogen that can cause a high mortality rate in the absence of prompt diagnosis and proper treatment in China, aggressive surgical debridement combined with prompt and appropriate antifungal treatment may improve outcomes.

Monodelphis domestica as a Fetal Intra-Cerebral Inoculation Model for Zika Virus Pathogenesis

Monodelphis domestica (the laboratory opossum) is a marsupial native to South America. At birth, these animals are developmentally equivalent to human embryos at approximately 5 weeks of gestation, which, when coupled with other characteristics including the size of the animals, the development of a robust immune system during juvenile development, and the relative ease of experimental manipulation, have made M. domestica a valuable model in many areas of biomedical research. However, their suitability as models for infectious diseases, especially neurotropic viruses such as Zika virus (ZIKV), is currently unknown. Here, we describe the replicative effects of ZIKV using a fetal intra-cerebral model of inoculation. Using immunohistology and in situ hybridization, we found that opossum embryos and fetuses are susceptible to infection by ZIKV administered intra-cerebrally, that the infection persists, and that viral replication results in neural pathology and may occasionally result in global growth restriction. These results demonstrate the utility of M. domestica as a new animal model for investigating ZIKV infection in vivo and facilitate further inquiry into viral pathogenesis, particularly for those viruses that are neurotropic, that require a host with the ability to sustain sustained viremia, and/or that may require intra-cerebral inoculations of large numbers of embryos or fetuses.

Case Series of Rare Fungal Keratitides: Experiences from a Quaternary Eye Hospital in Sydney, Australia

The present article reports on the management of six different and rare cases of fungal keratitides, two of which have never been documented in previous literature. This is a case series of six patients with rare fungal keratitides managed at a quaternary eye referral unit, Sydney Eye Hospital, Australia over a period of 7 months (May to December, 2022). The order of occurrence of fungi isolated was Scedosporium apiospermum, Lomenstospora prolificans, Cladosporium spp., Paecilomyces, Syncephalastrum racemosum and Quambalaria spp. A combination of medical and surgical interventions was employed, including topical and systemic anti-fungal therapy, with one requiring therapeutic penetrating keratoplasty and another eventuating in evisceration. Two patients were successfully treated with corneal debridement and two others required pars plana vitrectomy with anterior chamber washout. It is important to remain vigilant with monitoring patient symptoms and correlating with clinical signs to guide antifungal therapy even in the context of confirmed culture and sensitivity results.

The Diagnosis, Pathophysiology, and Treatment of Chronic Hepatitis E Virus Infection-A Condition Affecting Immunocompromised Patients

Hepatitis E is a zoonosis caused by hepatitis E virus (HEV), which was first discovered 40 years ago. Twenty million HEV infections worldwide are estimated each year. Most hepatitis E cases are self-limiting acute hepatitis, but the virus has been recognized to cause chronic hepatitis. Following the first case report of chronic hepatitis E (CHE) in a transplant recipient, CHE has recently been identified as associated with chronic liver damage induced by HEV genotypes 3, 4, and 7-usually in immunocompromised patients such as transplant recipients. In addition, patients infected with HIV and those receiving chemotherapy for malignancy, along with patients with rheumatic disease and COVID-19, have recently been reported as having CHE. CHE can be easily misdiagnosed by usual diagnostic methods of antibody response, such as anti-HEV IgM or IgA, because of the low antibody response in the immunosuppressive condition. HEV RNA should be evaluated in these patients, and appropriate treatments-such as ribavirin-should be given to prevent progression to liver cirrhosis or liver failure. While still rare, cases of CHE in immunocompetent patients have been reported, and care must be taken not to overlook these instances. Herein, we conduct an overview of hepatitis E, including recent research developments and management of CHE, in order to improve our understanding of such cases. The early diagnosis and treatment of CHE should be performed to decrease instances of hepatitis-virus-related deaths around the world.

Coccidioides-Induced Pyopneumothorax in an Immunocompetent Patient

Coccidioidomycosis is a rare infection caused by the dimorphic fungi Coccidiodes immitus or Coccidioides posadasii. This fungal infection is very common in the American Southwest as well as northern Mexico. Though the fungus is ubiquitous, symptomatic coccidioidomycosis usually occurs in the elderly or immunocompromised. This case report discusses a unique instance of an immunocompetent 29-year-old male without any notable past medical history who was found to have a coccidioidal cavitary lung lesion with concomitant pyopneumothorax.

Chronic Granulomatous Invasive Fungal Sinusitis in Patients With Immunocompetence: A Review

OBJECTIVE

We aimed to study the literature on chronic granulomatous invasive fungal sinusitis to elucidate the changing trends in the management of the disease.

DATA SOURCES

Using specific keywords, we searched the PubMed, PubMed Central, and Scopus databases over the past 50 years, which yielded 938 articles in the English language.

REVIEW METHODS

Scrutiny of 147 relevant articles revealed 15 homogenous case series (255 cases of histologically proven chronic granulomatous fungal sinusitis alone) and 8 heterogeneous case series (patients with other types of fungal sinusitis included), which were analyzed in detail (all with >5 cases each).

CONCLUSIONS

The disease typically affected middle-aged adults with immunocompetence. Most reports were from Sudan, India, and Saudi Arabia. A slowly progressive orbital, cheek, or palatal mass with proptosis (88.2%) or sinonasal symptoms (39.2%) was typical. Ethmoid (57.2%) and maxillary (51.4%) sinuses were chiefly affected with intracranial extension in 35.1%. Aspergillus flavus (64%) was the most frequent isolate reported. Endoscopic excision (78.8%) followed by azole therapy was the preferred treatment in recent reports. Orbital exenteration and craniotomy were infrequently performed. Complete resolution or improvement was reported in 91.3% of patients. Mortality ranged from 5.9% to 22.2%. There is a trend in the literature toward less radical and disfiguring surgery and preferential use of azoles, with good outcomes even in advanced cases.

IMPLICATIONS FOR PRACTICE

Chronic granulomatous fungal sinusitis should be diagnosed on the basis of well-defined histopathologic features. A combination of endoscopic sinus surgery and azole therapy usually yields good outcomes.

Pre-existing Immunocompromised Status as a Preventer of Mortality in COVID-19 Patients: Friend or Foe?

Objective COVID-19 has been negatively impacted by a number of comorbidities. Aside from that, some conditions or treatments that cause immunosuppression can alter the course of the disease, leading to worse outcomes. The primary goal of this study is to compare the clinical presentation, laboratory analysis, radiological findings, and outcomes of patients with COVID-19 with and without immunosuppression. Materials and methods The study includes patients with pre-existing immunosuppression and COVID-19 infection who were admitted and received inpatient treatment at Marmara University Hospital, Istanbul, Pulmonary Medicine ward between April 2020 and June 2020. Data on demographics, epidemiology, clinical course, laboratory analysis, radiological findings, length of hospital stay, morbidity, and mortality were collected from all patients. Results The study group consisted of 23 patients who had pre-existing immunosuppression, and the control group consisted of 207 immunocompetent patients, making a total of 230 patients. Significant differences in lymphocyte count, ROX (respiratory-rate oxygenation) index on Day 0, and fibrinogen levels were discovered between the two groups. SARI (severe acute respiratory infection) was more common in the control group than in the study group (p<0.022), but there was no difference in mortality. Conclusion The mean number and percentage of lymphocytes were lower in immunocompromised COVID-19 patients at the time of diagnosis. Higher ROX index values and a lower risk of developing SARI could explain the hypothesis that these patients may be benefiting from a pre-existing corticosteroid regimen. Additional research with larger numbers of patients may be beneficial in drawing a more definitive conclusion.

Pulmonary Tuberculosis Presenting As Septic Shock in an Immunocompetent Patient: Revisiting an Old Disease With New Perspectives

Septic shock due to Mycobacterium tuberculosis (M. tuberculosis) in immunocompromised patients (particularly HIV) is a well-recognized clinical entity. However, tubercular sepsis in the immunocompetent is still underdiagnosed and under-discussed. Moreover, sepsis is usually associated with gram-negative and other gram-positive microorganisms that can cause similar pulmonary and disseminated disease and can further convolute the diagnosis. We herein discuss a case of an elderly female who presented with acute onset fever, cough, and altered talk from the last seven days. Her initial clinical and laboratory examination revealed features of lower respiratory tract infection with septic shock. She was started on broad-spectrum antibiotics based on severe community-acquired pneumonia management guidelines. Her blood and urine cultures were sterile. She did not respond to initial antibiotics. Furthermore, sputum production was not possible, which compelled us for gastric aspirate analysis, which came positive for cartridge-based nucleic acid amplification test (CBNAAT). In repeated blood cultures, M. tuberculosis was also isolated. She was started on antitubercular treatment; on the 12th day of antitubercular treatment, she developed acute respiratory distress and eventually succumbed to her illness on the 19th day of hospitalization. We highlighted the importance of early diagnosis and prompt antitubercular therapy in tubercular septic shock. We also discuss the possibility of tubercular-immune reconstitution inflammatory syndrome (IRIS) in such patients, which could be a contributing factor to mortality.

Molecular Alterations in Cutaneous Squamous Cell Carcinoma in Immunocompetent and Immunosuppressed Hosts-A Systematic Review

The characterization of cutaneous squamous cell carcinoma (cSCC) at the molecular level is lacking in the current literature due to the high mutational burden of this disease. Immunosuppressed patients afflicted with cSCC experience considerable morbidity and mortality. In this article, we review the molecular profile of cSCC among the immunosuppressed and immunocompetent populations at the genetic, epigenetic, transcriptomic, and proteometabolomic levels, as well as describing key differences in the tumor immune microenvironment between these two populations. We feature novel biomarkers from the recent literature which may serve as potential targets for therapy.

Acanthamoeba meningoencephalitis causing secondary hemophagocytic lymphohistiocytosis in an immunocompetent patient: A first case report

Acanthamoeba is a rare cause of granulomatous amoebic encephalitis (GAE) associated with high mortality. There have been few case reports of Acanthamoeba meningoencephalitis worldwide. Hemophagocytic lymphohistiocytosis (HLH) is a severe hyperinflammatory condition caused by abnormally active macrophages and cytotoxic T lymphocytes; its secondary form is due to infections or malignancies. However, HLH is rather an unknown complication of GAE. We describe an unusual and previously unreported case of Acanthamoeba meningoencephalitis in a young immunocompetent female culminating in secondary HLH.

Subdural empyema secondary to pansinusitis after coronavirus disease 2019 infection in an immunocompetent patient: illustrative case

BACKGROUND

Superimposed intracranial infection is an uncommon but clinically significant complication in patients with active coronavirus disease 2019 (COVID-19), particularly in those with predisposing immunocompromising conditions.

OBSERVATIONS

The authors describe a case of subdural empyema, secondary to extension from pansinusitis, in a 20-year-old otherwise healthy immunocompetent male who was recently diagnosed with COVID-19. Despite his critical condition at time of presentation, he made a full clinical recovery with aggressive multidisciplinary surgical management between neurosurgery and otolaryngology, despite negative cultures to guide directed antimicrobial therapy. Ultimately, use of molecular-based polymerase chain reaction testing diagnosed Aspergillus fumigatus as the offending pathogen after the patient had already recovered and was discharged from the hospital.

LESSONS

This case demonstrates the potential for significant superimposed intracranial infection even in young, healthy individuals, infected by COVID-19 and suggests an aggressive surgical approach to achieve source control, particularly in the absence of positive cultures to guide antimicrobial therapies, may lead to rapid clinical improvement.

Deciphering Microbiota of Acute Upper Respiratory Infections: A Comparative Analysis of PCR and mNGS Methods for Lower Respiratory Trafficking Potential

Although it is clinically important for acute respiratory tract (co)infections to have a rapid and accurate diagnosis, it is critical that respiratory medicine understands the advantages of current laboratory methods. In this study, we tested nasopharyngeal samples (n = 29) with a commercially available PCR assay and compared the results with those of a hybridization-capture-based mNGS workflow. Detection criteria for positive PCR samples was Ct < 35 and for mNGS samples it was >40% target coverage, median depth of 1X and RPKM > 10. A high degree of concordance (98.33% PPA and 100% NPA) was recorded. However, mNGS yielded positively 29 additional microorganisms (23 bacteria, 4 viruses, and 2 fungi) beyond PCR. We then characterized the microorganisms of each method into three phenotypic categories using the IDbyDNA Explify^® Platform (Illumina^® Inc, San Diego, CA, USA) for consideration of infectivity and trafficking potential to the lower respiratory region. The findings are significant for providing a comprehensive yet clinically relevant microbiology profile of acute upper respiratory infection, especially important in immunocompromised or immunocompetent with comorbidity respiratory cases or where traditional syndromic approaches fail to identify pathogenicity. Accordingly, this technology can be used to supplement current syndrome-based tests, and data can quickly and effectively be phenotypically characterized for trafficking potential, clinical (co)infection, and comorbid consideration-with promise to reduce morbidity and mortality.

Incorporating microglia-like cells in human induced pluripotent stem cell-derived retinal organoids

Microglia are the primary resident immune cells in the retina. They regulate neuronal survival and synaptic pruning making them essential for normal development. Following injury, they mediate adaptive responses and under pathological conditions they can trigger neurodegeneration exacerbating the effect of a disease. Retinal organoids derived from human induced pluripotent stem cells (hiPSCs) are increasingly being used for a range of applications, including disease modelling, development of new therapies and in the study of retinogenesis. Despite many similarities to the retinas developed in vivo, they lack some key physiological features, including immune cells. We engineered an hiPSC co-culture system containing retinal organoids and microglia-like (iMG) cells and tested their retinal invasion capacity and function. We incorporated iMG into retinal organoids at 13 weeks and tested their effect on function and development at 15 and 22 weeks of differentiation. Our key findings showed that iMG cells were able to respond to endotoxin challenge in monocultures and when co-cultured with the organoids. We show that retinal organoids developed normally and retained their ability to generate spiking activity in response to light. Thus, this new co-culture immunocompetent in vitro retinal model provides a platform with greater relevance to the in vivo human retina.