FLT3L governs the development of partially overlapping hematopoietic lineages in humans and mice.

FMS-related tyrosine kinase 3 ligand (FLT3L), encoded by FLT3LG, is a hematopoietic factor essential for the development of natural killer (NK) cells, B cells, and dendritic cells (DCs) in mice. We describe three humans homozygous for a loss-of-function FLT3LG variant with a history of various recurrent infections, including severe cutaneous warts. The patients' bone marrow (BM) was hypoplastic, with low levels of hematopoietic progenitors, particularly myeloid and B cell precursors. Counts of B cells, monocytes, and DCs were low in the patients' blood, whereas the other blood subsets, including NK cells, were affected only moderately, if at all. The patients had normal counts of Langerhans cells (LCs) and dermal macrophages in the skin but lacked dermal DCs. Thus, FLT3L is required for B cell and DC development in mice and humans. However, unlike its murine counterpart, human FLT3L is required for the development of monocytes but not NK cells.

Protective role of antibodies in enteric virus infections: Lessons from primary and secondary immune deficiencies.

Enteric viruses are the main cause of acute gastroenteritis worldwide with a significant morbidity and mortality, especially among children and aged adults. Some enteric viruses also cause disseminated infections and severe neurological manifestations such as poliomyelitis. Protective immunity against these viruses is not well understood in humans, with most knowledge coming from animal models, although the development of poliovirus and rotavirus vaccines has extended our knowledge. In a classical view, innate immunity involves the recognition of foreign DNA or RNA by pathogen recognition receptors leading to the production of interferons and other inflammatory cytokines. Antigen uptake and presentation to T cells and B cells then activate adaptive immunity and, in the case of the mucosal immunity, induce the secretion of dimeric IgA, the more potent immunoglobulins in viral neutralization. The study of Inborn errors of immunity (IEIs) offers a natural opportunity to study nonredundant immunity toward pathogens. In the case of enteric viruses, patients with a defective production of antibodies are at risk of developing neurological complications. Moreover, a recent description of patients with low or absent antibody production with protracted enteric viral infections associated with hepatitis reinforces the prominent role of B cells and immunoglobulins in the control of enteric virus.

In utero treatment of congenital cytomegalovirus infection with valganciclovir: an observational study on safety and effectiveness.

BACKGROUND: The treatment of congenital cytomegalovirus (CMV) infection is usually administered to neonates after birth; however, it can be anticipated during the prenatal period by treating pregnant women in order to reduce the severity of the congenital disease. The most commonly used treatment for CMV during pregnancy is valaciclovir; however, valganciclovir has a higher potency against CMV and is the first choice for neonates with congenital CMV disease. OBJECTIVES: We investigated neonatal and maternal safety of tertiary prevention in infected fetuses showing ultrasound features of infection using valganciclovir. METHODS: Retrospective cohort study of pregnant women and their symptomatic infected fetuses taking valganciclovir, 3 × 450 mg per day. All fetuses presented at least one prenatal feature on ultrasound. We assessed fetal/neonatal and maternal safety, as well as neonatal efficacy of treatment. The main outcome was neutropenia. Secondary outcomes included other haematological side effects, symptoms at birth and neonatal CMV-PCR was positive. RESULTS: Seventeen women with singleton pregnancies received valganciclovir from a median (IQR) of 27.1 (26.0-30.3) to 11.6 (6.5-12.9) weeks of gestation. No neonatal neutropenia was reported. One pregnancy was terminated for severe features. Three newborns (18%) were asymptomatic at birth, including one with negative CMV-PCR from blood and saliva. CMV-PCR was positive for 12/13 symptomatic newborns, with a median (IQR) log10 viral load of 3.36 (3.30-4.20), 4.03 (1.75-4.27) and 3.04 (0.00-3.40) log10 copies/mL in blood, urine and saliva, respectively. CONCLUSIONS: Tertiary prevention by valganciclovir appears to be well tolerated for both fetus and mother. However, more extensive trials accompanied by long-term follow-up are needed.

Late-onset enteric virus infection associated with hepatitis (EVAH) in transplanted SCID patients.

BACKGROUND: Allogenic hematopoietic stem cell transplantation (HSCT) and gene therapy (GT) are potentially curative treatments for severe combined immunodeficiency (SCID). Late-onset posttreatment manifestations (such as persistent hepatitis) are not uncommon. OBJECTIVE: We sought to characterize the prevalence and pathophysiology of persistent hepatitis in transplanted SCID patients (SCIDH+) and to evaluate risk factors and treatments. METHODS: We used various techniques (including pathology assessments, metagenomics, single-cell transcriptomics, and cytometry by time of flight) to perform an in-depth study of different tissues from patients in the SCIDH+ group and corresponding asymptomatic similarly transplanted SCID patients without hepatitis (SCIDH-). RESULTS: Eleven patients developed persistent hepatitis (median of 6 years after HSCT or GT). This condition was associated with the chronic detection of enteric viruses (human Aichi virus, norovirus, and sapovirus) in liver and/or stools, which were not found in stools from the SCIDH- group (n = 12). Multiomics analysis identified an expansion of effector memory CD8+ T cells with high type I and II interferon signatures. Hepatitis was associated with absence of myeloablation during conditioning, split chimerism, and defective B-cell function, representing 25% of the 44 patients with SCID having these characteristics. Partially myeloablative retransplantation or GT of patients with this condition (which we have named as "enteric virus infection associated with hepatitis") led to the reconstitution of T- and B-cell immunity and remission of hepatitis in 5 patients, concomitantly with viral clearance. CONCLUSIONS: Enteric virus infection associated with hepatitis is related to chronic enteric viral infection and immune dysregulation and is an important risk for transplanted SCID patients with defective B-cell function.

Chronic Aichi Virus Infection As a Cause of Long-Lasting Multiorgan Involvement in Patients With Primary Immune Deficiencies.

BACKGROUND: Metagenomic next-generation sequencing (mNGS) was used to assess patients with primary or secondary immune deficiencies (PIDs and SIDs) who presented with immunopathological conditions related to immunodysregulation. METHODS: Thirty patients with PIDs or SIDs who presented with symptoms related to immunodysregulation and 59 asymptomatic patients with similar PIDs or SIDs were enrolled. mNGS was performed on organ biopsy. Specific Aichi virus (AiV) reverse-transcription polymerase chain reaction (RT-PCR) was used to confirm AiV infection and screen the other patients. In situ hybridization (ISH) assay was done on AiV-infected organs to identify infected cells. Virus genotype was determined by phylogenetic analysis. RESULTS: AiV sequences were detected using mNGS in tissue samples of 5 patients and by RT-PCR in peripheral samples of another patient, all of whom presented with PID and long-lasting multiorgan involvement, including hepatitis, splenomegaly, and nephritis in 4 patients. CD8+ T-cell infiltration was a hallmark of the disease. RT-PCR detected intermittent low viral loads in urine and plasma from infected patients but not from uninfected patients. Viral detection stopped after immune reconstitution obtained by hematopoietic stem cell transplantation. ISH demonstrated the presence of AiV RNA in hepatocytes (n = 1) and spleen tissue (n = 2). AiV belonged to genotype A (n = 2) or B (n = 3). CONCLUSIONS: The similarity of the clinical presentation, the detection of AiV in a subgroup of patients suffering from immunodysregulation, the absence of AiV in asymptomatic patients, the detection of viral genome in infected organs by ISH, and the reversibility of symptoms after treatment argue for AiV causality.

Circovirus Hepatitis Infection in Heart-Lung Transplant Patient, France.

In March 2022, a 61-year-old woman in France who had received a heart-lung transplant sought treatment with chronic hepatitis mainly characterized by increased liver enzymes. After ruling out common etiologies, we used metagenomic next-generation sequencing to analyze a liver biopsy sample and identified an unknown species of circovirus, tentatively named human circovirus 1 (HCirV-1). We found no other viral or bacterial sequences. HCirV-1 shared 70% amino acid identity with the closest known viral sequences. The viral genome was undetectable in blood samples from 2017-2019, then became detectable at low levels in September 2020 and peaked at very high titers (1010 genome copies/mL) in January 2022. In March 2022, we found >108 genome copies/g or mL in the liver and blood, concomitant with hepatic cytolysis. We detected HCirV-1 transcripts in 2% of hepatocytes, demonstrating viral replication and supporting the role of HCirV-1 in liver damage.

Clinical Value of Serial Quantitative Analysis of Cytomegalovirus DNA in Blood and Saliva Over the First 24 Months of Life in Congenital Infection: The French Cymepedia Cohort.

OBJECTIVE: To evaluate cytomegalovirus (CMV) viral load dynamics in blood and saliva during the first 2 years of life in symptomatic and asymptomatic infected infants and to identify whether these kinetics could have practical clinical implications. STUDY DESIGN: The Cymepedia cohort prospectively included 256 congenitally infected neonates followed for 2 years. Whole blood and saliva were collected at inclusion and months 4 and 12, and saliva at months 18 and 24. Real-time CMV polymerase chain reaction (PCR) was performed, results expressed as log10 IU/mL in blood and in copies per milliliter in saliva. RESULTS: Viral load in saliva progressively decreased from 7.5 log10 at birth to 3.3 log10 at month 24. CMV PCR in saliva was positive in 100% and 96% of infants at 6 and 12 months, respectively. In the first month of life, neonatal saliva viral load of less than 5 log10 was related to a late CMV transplacental passage. Detection in blood was positive in 92% of neonates (147/159) in the first month of life. No viral load threshold values in blood or saliva could be associated with a high risk of sequelae. Neonatal blood viral load of less than 3 log10 IU/mL had a 100% negative predictive value for long-term sequelae. CONCLUSIONS: Viral loads in blood and saliva by CMV PCR testing in congenital infection fall over the first 24 months. In this study of infants affected mainly after primary maternal infection during pregnancy, all salivary samples were positive in the first 6 months of life and sequelae were not seen in infants with neonatal blood viral load of less than 3 log10 IU/mL.

Severe relapse of SARS-CoV-2 infection in a kidney transplant recipient with negative nasopharyngeal SARS-CoV-2 RT-PCR after rituximab.

Immunocompromised patients may experience prolonged viral shedding after their initial SARS-CoV-2 infection, however, symptomatic relapses after remission currently remain rare. We herein describe a severe COVID-19 relapse case of a kidney transplant recipient (KTR) following rituximab therapy, 3 months after a moderate COVID-19 infection, despite viral clearance after recovery of the first episode. During the clinical relapse, the diagnosis was established on a broncho-alveolar lavage specimen (BAL) by RT-PCR. The infectivity of the BAL sample was confirmed on a cell culture assay. Whole genome sequencing confirmed the presence of an identical stain (Clade 20A). However, it had an acquired G142D mutation and a larger deletion of 3-amino-acids at position 143-145. These mutations located within the N-terminal domain are suggested to play a role in viral entry. The diagnosis of a COVID-19 relapse should be considered in the setting of unexplained persistent fever and/or respiratory symptoms in KTRs (especially for those after rituximab therapy), even in patients with previous negative naso-pharyngeal SARS-CoV-2 PCR.

Comparing Dynamics and Determinants of Severe Acute Respiratory Syndrome Coronavirus 2 Transmissions Among Healthcare Workers of Adult and Pediatric Settings in Central Paris.

BACKGROUND: Healthcare workers (HCWs) have paid a heavy toll during the coronavirus disease 2019 (COVID-19) outbreak. Routes of transmission remain to be fully understood. METHODS: This prospective study compared a 1500-bed adult and 600-bed pediatric setting of a tertiary-care university hospital located in central Paris. From 24 February until 10 April 2020, all symptomatic HCWs were screened for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on a nasopharyngeal swab. HCWs screened positive were questioned on their profession, symptoms, and occupational and nonoccupational exposures to SARS-CoV-2. RESULTS: Among 1344 HCWs tested, 373 were positive (28%) and 336 (90%) corresponding questionnaires were completed. Three hospitalizations and no deaths were reported. Most HCWs (70%) had patient-facing occupational activities (22% in COVID-19 dedicated units). The total number of HCW cases peaked on 23 March, then decreased slowly, concomitantly with a continuous increase of compliance to preventive measures (including universal medical masking and personal protective equipment [PPE] for direct care to COVID-19 patients). Attack rates were of 3.2% and 2.3% in the adult and pediatric settings, respectively (P = .0022). In the adult setting, HCWs more frequently reported exposure to COVID-19 patients without PPE (25% vs 15%, P = .046). Report of contacts with children attending out-of-home care facilities dramatically decreased over the study period. CONCLUSIONS: Universal masking, reinforcement of hand hygiene, and PPE with medical masks for patients' care allowed protection of HCWs and containment of the outbreak. Residual transmissions were related to persistent exposures with undiagnosed patients or colleagues and not to contacts with children attending out-of-home care facilities.

Impact of public health measures on the post-COVID-19 respiratory syncytial virus epidemics in France.

Since the beginning of the COVID-19 pandemic, other respiratory illnesses decreased worldwide. This study described the consequences of public health measures on respiratory syncytial virus (RSV) severe infections in France, where an interseasonal resurgence of RSV occurred recently. All patients admitted to Necker Hospital (Paris) between August 2018 and April 2021 with a diagnosis of RSV-associated acute lung respiratory infection (ALRI) were enrolled. Characteristics of subjects with RSV-associated ALRI in 2020/2021 were compared to those infected during the two previous outbreaks. Overall, 664 inpatients were diagnosed with RSV-associated ALRI: 229, 183, and 252 during the 2018/2019, 2019/2020, and 2020/2021 outbreaks, respectively. During autumn 2020, a national lockdown began in France but schools remained open. A 3-month delayed RSV epidemic occurred at the end of this lockdown. Compared to previous outbreaks, the 2020/2021 epidemics involved more children aged 6 to 11 months (25.8% versus 13.1%, p < 0.0001), but less infants aged < 6 months (41.3% versus 56.6%, p < 0.0001) and less adults (0.0 versus 2.7%, p < 0.0001). Shorter length of stay at hospital, less frequent requirement of admission to intensive care unit, use of non-invasive ventilation, and/or high-flow nasal oxygen were observed in 2020/2021 than during previous epidemics (p < 0.0001). Delayed RSV outbreak was associated with more hospitalizations for ALRI, higher age of pediatric inpatients, but milder median clinical phenotype. Reinforced public health measures (even while keeping nurseries and schools open with mandatory face masks since six years of age) could impact, at least transiently, the burden of RSV-related hospitalizations.

Accuracy of saliva and nasopharyngeal sampling for detection of SARS-CoV-2 in community screening: a multicentric cohort study.

Nasopharyngeal sampling for nucleic acid amplification testing (NAAT) is the standard diagnostic test of coronavirus disease 2019. Our objectives were to assess, in real-life conditions, the diagnostic accuracy of a nasopharyngeal point-of-care antigen (Ag) test and of saliva NAAT for detection of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in ambulatory care. This was a prospective cohort study from 19 October through 18 December 2020 in two community COVID-19 screening centers in Paris, France. Two nasopharyngeal swabs and one saliva sample were simultaneously collected. Diagnostic accuracies of nasopharyngeal Ag testing and of three saliva NAAT methods were assessed as compared to nasopharyngeal NAAT. A total of 1452 ambulatory children and adults were included. Overall, 129/1443 (9%) participants tested positive on nasopharyngeal NAAT (102/564 [18%] in symptomatic and 27/879 [3%] in asymptomatic participants). Sensitivity was 94%, 23%, 96%, and 94% for the three different protocols of saliva NAAT and for the nasopharyngeal Ag test, respectively. Estimates of specificity were above 95% for all methods. Diagnostic accuracy was similar in symptomatic and asymptomatic individuals. Diagnostic accuracy of nasopharyngeal Ag testing and of saliva NAAT is similar to that of nasopharyngeal NAAT, subject to compliance with specific protocols for saliva. Registration number: NCT04578509.

Performance of 30 commercial SARS-CoV-2 serology assays in testing symptomatic COVID-19 patients.

We report evaluation of 30 assays' (17 rapid tests (RDTs) and 13 automated/manual ELISA/CLIA assay (IAs)) clinical performances with 2594 sera collected from symptomatic patients with positive SARS-CoV-2 rRT-PCR on a respiratory sample, and 1996 pre-epidemic serum samples expected to be negative. Only 4 RDT and 3 IAs fitted both specificity (> 98%) and sensitivity (> 90%) criteria according to French recommendations. Serology may offer valuable information during COVID-19 pandemic, but inconsistent performances observed among the 30 commercial assays evaluated, which underlines the importance of independent evaluation before clinical implementation.

Consensus recommendation for prenatal, neonatal and postnatal management of congenital cytomegalovirus infection from the European congenital infection initiative (ECCI).

Congenital cytomegalovirus (cCMV) infection carries a significant burden with a 0.64% global prevalence and a 17-20% chance of serious long-term effects in children. Since the last guidelines, our understanding, particularly regarding primary maternal infections, has improved. A cCMV guidelines group was convened under the patronage of the European Society of Clinical Virology in April 2023 to refine these insights. The quality and validity of selected studies were assessed for potential biases and the GRADE framework was employed to evaluate quality of evidence across key domains. The resulting recommendations address managing cCMV, spanning prevention to postnatal care. Emphasizing early and accurate maternal diagnosis through serological tests enhances risk management and prevention strategies, including using valaciclovir to prevent vertical transmission. The guidelines also strive to refine personalized postnatal care based on risk assessments, ensuring targeted interventions for affected families.

Corrigendum to "Consensus recommendation for prenatal, neonatal and postnatal management of congenital cytomegalovirus infection from the European congenital infection initiative (ECCI)" [The Lancet Regional Health - Europe 40 (2024) 100892].

[This corrects the article DOI: 10.1016/j.lanepe.2024.100892.].

Predictors of the Outcome at 2 Years in Neonates With Congenital Cytomegalovirus Infection.

BACKGROUND: Approximately 20% of neonates with congenital cytomegalovirus (cCMV) develop long-term sequelae. The ability to accurately predict long-term outcomes as early as the neonatal period would help to provide for appropriate parental counseling and treatment indications. With this study, we aimed to identify neonatal predictive markers of cCMV long-term outcomes. METHODS: As this study's subjects, we chose neonates diagnosed with cCMV in 13 hospitals throughout France recruited from 2013 to 2017 and evaluated for at least 2 years with thorough clinical, audiology, and imaging evaluations and psychomotor development tests. RESULTS: A total of 253 neonates were included, and 3 were later excluded because of the identification of a genetic disorder. A total of 227 were followed up for 2 years: 187/227 (82%) and 34/227 (15%) were infected after a maternal primary or nonprimary infection, respectively, 91/227 (40%) were symptomatic at birth, and 44/227 (19%) had cCMV sequelae. Maternal primary infection in the first trimester was the strongest prognosis factor (odds ratio = 38.34 [95% confidence interval, 5.02-293], P < .001). A predictive model of no risk of sequelae at 2 years of age according to normal hearing loss at birth, normal cerebral ultrasound, and normal platelet count had 98% specificity, 69% sensitivity, and 0.89 area under the curve (95% confidence interval, 0.83-0.96). CONCLUSIONS: In the studied population, children with normal hearing at birth, normal platelet count at birth, and a normal cranial ultrasound had no risk of neurologic sequelae and a low risk of delayed unilateral sensorineural hearing loss. The use of this model based on readily available neonatal markers should help clinicians establish a personalized care pathway for each cCMV neonate.

Performance of clinical metagenomics in France: a prospective observational study.

BACKGROUND: Metagenomic next-generation sequencing (mNGS) allows untargeted identification of a broad range of pathogens, including rare or novel microorganisms. Despite the recognition of mNGS as a valuable diagnostic tool for infections, the most relevant indications for this innovative strategy remain poorly defined. We aimed to assess the determinants of positivity and clinical utility of mNGS. METHODS: In this observational study, we prospectively performed short-read shotgun metagenomics analysis as a second-line test (in cases of negative first-line test or when the symptoms were not fully explained by initial positive results) or as a first-line test in life-threatening situations requiring urgent non-targeted pathogen identification at the Necker-Enfants Malades Hospital (Paris, France). All sample types, clinical indications, and patient populations were included. Samples were accompanied by a mandatory form completed by the senior clinician or pathologist, on which the clinical level of suspected infection (defined as high or low) was indicated. We assessed the variables (gender, age, immune status, initial suspicion of infection, indication, and sample type) associated with mNGS pathogen detection using odds ratios (ORs) from multivariate logistic regression. Additional investigations were carried out using specific PCR or culture techniques, to confirm positive mNGS results, or when infectious suspicion was particularly high despite a negative mNGS result. FINDINGS: Between Oct 29, 2019, and Nov 7, 2022, we analysed 742 samples collected from 523 patients. The initial suspicion of infection was either high (n=470, 63%) or low (n=272, 37%). Causative or possibly causative pathogens were detected in 117 (25%) samples from patients with high initial suspicion of infection, versus nine (3%) samples analysed to rule out infection (OR 9·1, 95% CI 4·6-20·4; p<0·0001). We showed that mNGS had higher odds of detecting a causative or possibly causative pathogenic virus on CNS biopsies than CSF samples (4·1, 1·7-10·7; p=0·0025) and in samples from immunodeficient compared with immunocompetent individuals (2·4, 1·4-4·1; p=0·0013). Concordance with conventional confirmatory tests results was 103 (97%) of 106, when mNGS detected causative or possibly causative pathogens. Altogether, among 231 samples investigated by both mNGS and subsequent specific tests, discordant results were found in 69 (30%) samples, of which 58 (84%) were mNGS positive and specific tests negative, and 11 (16%) mNGS negative and specific tests positive. INTERPRETATION: Major determinants of pathogen detection by mNGS are immune status and initial level of suspicion of infection. These findings will contribute, along with future studies, to refining the positioning of mNGS in diagnostic and treatment decision-making algorithms. FUNDING: Necker-Enfants Malades Hospital and Institut Pasteur. TRANSLATION: For the French translation of the abstract see Supplementary Materials section.