Invasive pneumococcal disease in children can reveal a primary immunodeficiency

Group A Streptococcal Disease in Sudden Unexpected Death in Youth in the Pre- and Post-COVID-19 Era

BACKGROUND

An upsurge in pediatric invasive group A streptococcal infection (iGAS) has been observed in the Netherlands along with a suspected increase in iGAS-related sudden death. Sudden unexplained deaths in youth (SUDY) are investigated nationally through a standardized procedure [(Postmortem Evaluation of Sudden Unexplained Death in Youth (PESUDY)]. We investigate epidemiological differences between pediatric iGAS-related sudden deaths (iGAS-PESUDY) and surviving iGAS cases.

METHODS

This observational study used data from the COPP-iGAS study on pediatric iGAS infections in Dutch hospitals and the PESUDY database. Children 0-18 years of age were included between August 2016 and December 2022.

RESULTS

Twenty-one iGAS-PESUDY cases and 156 iGAS survivors were included. iGAS-PESUDY cases tended to be older compared to survivors. iGAS-PESUDY cases significantly increased in 2022 compared to the pre-COVID period. Pre- and/or coinciding infections were present in 66% of iGAS-PESUDY cases, predominantly varicella zoster (19%) and influenza (24%). In survivors, 13% had varicella zoster virus and 3% had influenza virus ( P ≤ 0.001). C-reactive protein levels tended to be lower in iGAS-PESUDY cases (81 mg/L; interquartile range, 26.8-307.5) compared to survivors (266 mg/L; interquartile range, 218.0-302.0).

CONCLUSION

iGAS is currently a prevalent cause of SUDY. The finding of moderately elevated C-reactive protein levels compared to high levels in survivors might suggest children dying suddenly of iGAS have a rapid and fulminant disease course. Children with a pre- and/or coinciding infection of varicella zoster or influenza virus may be at greater risk of succumbing to iGAS infections.

Recurrent Invasive Pneumococcal Disease in Children: a retrospective cohort study, England, 2006/07-2017/18

BACKGROUND

Recurrent invasive pneumococcal disease (IPD) is rare in children and usually associated with underlying comorbidities. We aimed to assess the risk and describe the characteristics of children with recurrent IPD over a 12-year-period covering the introduction of the 7-valent (PCV7) followed by the 13-valent (PCV13) pneumococcal conjugate vaccine (PCV) in the national childhood immunisation programme in England.

METHODS

We used enhanced national surveillance data for England and included all laboratory-confirmed IPD cases in children (<15 years) during 2006/07-2017/18. We assessed the risk and rate of recurrent IPD, the serotypes responsible and the demographics, comorbidity status and prevalence, vaccination status, clinical presentation and outcomes in children with recurrent IPD compared to those with a single IPD episode.

FINDINGS

There were 5,158 IPD episodes reported in 5,033 children over 12 years and 2.2% (105/4,814) of those surviving their first IPD had at least one recurrence. Recurrence risk decreased with increasing age and over time. During 2015/16-2017/18, five years after PCV13 replaced PCV7, IPD recurrence rate was 229.0 (95% CI 154.8-339.0) per 100,000 person years, with all recurrent cases caused by non-PCV13 serotypes. Where serotype information was available, recurrence was due to the same serotype in 25 cases, with a shorter median (IQR) interval of 88 (57-177) days between recurrent episodes, and in 60 cases due to different serotypes, with a median (IQR) interval of 223 (125-574) days (p=0.001). Compared to healthy children (103.0 95%CI 63.1-168.1), recurrence rate per 100,000 person-years was 10 times higher in children with any comorbidity (1,061.02; 95% CI 827.2-1,360.9; 62/78 [79.5%] with available information had comorbidities), and almost 30 times higher in immunosuppressed children (2,788.5; 95%CI 2,029.0-3,832.2; 38/78 [48.7%] were immunosuppressed). The 30-day case-fatality rate after recurrent IPD was 2.9% (3/105) compared to 4.4% (219/4,928; P=0.63) after single-episode IPD.

INTERPRETATION

Recurrent IPD is rare in children and occurs mainly in children with comorbidities, especially immunosuppression. Higher-valent PCVs have the potential to further reduce the risk recurrent IPD in children.

The monogenic landscape of human infectious diseases

The spectrum of known monogenic inborn errors of immunity is growing, with certain disorders underlying a specific and narrow range of infectious diseases. These disorders reveal the core mechanisms by which these infections occur in various settings, including inherited and acquired immunodeficiencies, thereby delineating the essential mechanisms of protective immunity to the corresponding pathogens. These findings also have medical implications, facilitating diagnosis and improving the management of individuals at risk of disease.

Application of whole-exome sequencing to predict inborn errors of immunity in pediatric severe infections and sepsis

Increasing evidence supports the involvement of inborn errors of immunity in severe infections, but little is known about the prevalence of these genetic defects in children with sepsis. Due to the limited understanding of the molecular and immunological mechanisms driving sepsis, genetic testing is rarely used in routine diagnostics to identify genetic susceptibility to the condition. We performed a prospective observational study on previously healthy children hospitalized for severe infections, including sepsis. Patients underwent immunophenotyping and whole-exome sequencing, followed by in silico analysis to identify potentially causal variants. We assembled a cohort of 194 previously healthy children, including 149 (77%) patients with severe infection and 45 (23%) with sepsis. Our cohort was marked by a high frequency of respiratory tract infections (35%), bloodstream infections (20%), and central nervous system infections (16%). The genetic investigation identified 28 potentially causal variants, 18 (64%) are classified as variants with uncertain significance, and 10 (36%) are likely pathogenic variants. Of 45 patients with sepsis, 6 (13%) had potentially causal genetic variants. Similarly, 22/149 (15%) patients with severe infection presented potentially causal genetic variants. Whole-exome sequencing predicted the impairment of various immune mechanistic pathways such as immune dysregulation defects, antibody deficiencies, and combined immunodeficiencies (18% each). We found no clear association between genetic variants and the studied parameters: organ failure, microbe identification, immunoglobulin levels, and lymphocyte subset numbers. Although whole-exome sequencing is a valuable tool for detecting inborn errors of immunity underlying sepsis and unexplained severe infections, it could be selectively recommended for patients with a strong clinical suspicion of genetic abnormalities, balancing its diagnostic value with its cost and complexity.

Whole-exome sequencing to identify undiagnosed primary immunodeficiency disorders in children with community-acquired sepsis, admitted in the pediatric intensive care unit

BACKGROUND

Whole-exome sequencing (WES) provides a powerful diagnostic tool for identifying primary immunodeficiency diseases (PIDs). This study explores the utility of this approach in uncovering previously undiagnosed PIDs in children with community-acquired sepsis (CAS), with a medical history of recurrent infections or a family history of PIDs.

METHODS

We performed WES on DNA samples extracted from the blood of the 34 enrolled patients, followed by bioinformatic analysis for variant calling, annotation, and prioritization. We also performed a segregation analysis in available family members to confirm the inheritance patterns and assessed the potential impact of the identified variants on protein function.

RESULTS

From 34 patients enrolled in the study, 29 patients (85%) with previously undiagnosed genetic diseases, including 28 patients with PIDs and one patient with interstitial lung and liver disease, were identified. We identified two patients with severe combined immunodeficiency (SCID), patients with combined immunodeficiency (CID), six patients with combined immunodeficiency with syndromic features (CID-SF), four patients with defects in intrinsic and innate immunity, four patients with congenital defects of phagocyte function (CPDF), and six patients with the disease of immune dysregulation. Autoinflammatory disorders and predominantly antibody deficiency were diagnosed in one patient each.

CONCLUSION

Our findings demonstrate the potential of WES in identifying undiagnosed PIDs in children with CAS. Implementing WES in the clinical evaluation of CAS patients with a warning sign for PIDs can aid in their timely diagnosis and potentially lead to improved patient care.

Inborn Errors of Immunity in Children With Invasive Pneumococcal Disease: A Multicenter Prospective Study

BACKGROUND

In settings with universal conjugate pneumococcal vaccination, invasive pneumococcal disease (IPD) can be a marker of an underlying inborn error of immunity. The aim of this study was to determine the prevalence and characterize the types of immunodeficiencies in children presenting with IPD.

METHODS

Multicenter prospective audit following the introduction of routinely recommended immunological screening in children presenting with IPD. The minimum immunological evaluation comprised a full blood examination and film, serum immunoglobulins (IgG, IgA and IgM), complement levels and function. Included participants were children in whom Streptococcus pneumoniae was isolated from a normally sterile site (cerebrospinal fluid, pleura, peritoneum and synovium). If isolated from blood, features of sepsis needed to be present. Children with predisposing factors for IPD (nephrotic syndrome, anatomical defect or malignancy) were excluded.

RESULTS

Overall, there were 379 episodes of IPD of which 313 (83%) were eligible for inclusion and 143/313 (46%) had an immunologic evaluation. Of these, 17/143 (12%) were diagnosed with a clinically significant abnormality: hypogammaglobulinemia (n = 4), IgA deficiency (n = 3), common variable immunodeficiency (n = 2), asplenia (n = 2), specific antibody deficiency (n = 2), incontinentia pigmenti with immunologic dysfunction (n = 1), alternative complement deficiency (n = 1), complement factor H deficiency (n = 1) and congenital disorder of glycosylation (n = 1). The number needed to investigate to identify 1 child presenting with IPD with an immunologic abnormality was 7 for children under 2 years and 9 for those 2 years old and over.

CONCLUSIONS

This study supports the routine immune evaluation of children presenting with IPD of any age, with consideration of referral to a pediatric immunologist.

A case report of disseminated Streptococcus pneumoniae infection complicated by infective endocarditis, septic arthritis and epidural abscess in an immunocompetent patient

Streptococcus pneumoniae is a highly virulent, vaccine-preventable pathogen which can cause disease on a spectrum from benign to fatal. Apart from pneumonia, it commonly causes septicaemia and meningitis. This case report describes an unusual range of complications in a 53-year-old Caucasian female presenting to a regional hospital, without any risk known factors for severe disease (such as extremes of age, immunodeficiency or co-morbidities). Progressing from an episode of otitis media, her condition rapidly progressed to mastoid sinusitis, septic arthritis, infective endocarditis, epidural abscesses and multiple subcutaneous abscesses. Following quick identification of S. pneumoniae from a positive blood culture, the patient was treated with high-dose benzylpenicillin and ceftriaxone and aggressive source control by surgery, enabling a good clinical recovery.

Recurrent or unusual infections in children - when to worry about inborn errors of immunity

Recurrent infections are a common presenting feature in paediatrics and, while most times considered part of normal growing up, they are also a classical hallmark of inborn errors of immunity (IEI). We aimed to outline the value of currently used signs for IEI and the influence of the changing epidemiology of infectious diseases due to implementation of new vaccines and the effect of the COVID-19 pandemic on the assessment of children with recurrent infections. Warning signs for IEI have been developed, but the supporting evidence for their effectiveness is limited, and immune dysregulation is more commonly recognised as a feature for IEI, making reliable identification of children who should be screened for IEI on clinical grounds difficult. In addition, the epidemiology of infectious diseases is changing due to restrictions related to Covid-19 as well as immunisations, which may change the threshold to screen children for IEI. Treatments for IEI are evolving and are often more effective and less complicated when started early. Screening for IEI can be initiated by the non-immunologist and should be considered early to ensure optimal treatment outcomes.

Inborn errors of immunity underlying a susceptibility to pyogenic infections: from innate immune system deficiency to complex phenotypes

BACKGROUND

Pyogenic bacteria are associated with a wide range of clinical manifestations, ranging from common and relatively mild respiratory and cutaneous infections to life-threatening localized or systemic infections, such as sepsis and profound abscesses. Despite vaccination and the widespread use of effective antibiotic treatment, severe infection is still observed in a subset of affected patients.

OBJECTIVES

We aim to summarize the available data regarding inborn errors of immunity that result in a high risk of severe pyogenic infections.

SOURCES

Case series, as well as review and original articles on human genetic susceptibility to pyogenic infections were examined.

CONTENT

We review host-associated factors resulting in inborn errors of immunity and leading to a susceptibility to pyogenic infections, including deficiency in major components of the immune system (e.g., neutrophils, complement, immunoglobulin, and spleen function) and novel monogenic disorders resulting in specific susceptibility to pyogenic infection. Specifically, innate immune system deficiency involving toll-like receptors and associated signaling typically predispose to a narrow spectrum of bacterial diseases in otherwise healthy people, making a diagnosis more difficult to suspect and confirm. More complex syndromes, such as hyper IgE syndrome, are associated with a high risk of pyogenic infections due to an impairment of the interleukin-6 or -17 signaling, demonstrating the pivotal role of these pathways in controlling bacterial infections.

IMPLICATIONS

In clinical practice, awareness of such conditions is essential, especially in the pediatric setting, to avoid a potentially fatal diagnostic delay, set the most proper and prompt treatment, and ensure prevention of severe complications.

The yin and the yang of early classical pathway complement disorders

The classical pathway of the complement cascade has been recognized as a key activation arm, partnering with the lectin activation arm and the alternative pathway to cleave C3 and initiate the assembly of the terminal components. While deficiencies of classical pathway components have been recognized since 1966, only recently have gain-of-function variants been described for some of these proteins. Loss-of-function variants in C1, C4, and C2 are most often associated with lupus and systemic infections with encapsulated bacteria. C3 deficiency varies slightly from this phenotypic class with membranoproliferative glomerulonephritis and infection as the dominant phenotypes. The gain-of-function variants recently described for C1r and C1s lead to periodontal Ehlers Danlos syndrome, a surprisingly structural phenotype. Gain-of-function in C3 and C2 are associated with endothelial manifestations including hemolytic uremic syndrome and vasculitis with C2 gain-of-function variants thus far having been reported in patients with a C3 glomerulopathy. This review will discuss the loss-of-function and gain-of-function phenotypes and place them within the larger context of complement deficiencies.

Screening for Immunodeficiencies in Children With Invasive Pneumococcal Disease: Six-year Experience From a UK Children's Hospital

BACKGROUND

A previous study showed that investigation of children with invasive pneumococcal disease (IPD) revealed an immunodeficiency in up to 10% of cases. Following this report, we implemented a protocol to investigate children with IPD, to assess the proportion with an immunodeficiency in our setting.

METHODS

We retrospectively identified patients who presented with IPD from January 2015 to November 2020 and collected data from medical records. Immunological investigations included complement C3 and C4 levels, classical and alternative pathway complement function, IgG, IgA and IgM levels, specific IgG levels (H. influenza B, tetanus and pneumococcal serotypes), peripheral blood film, lymphocyte subsets, and CD62L-shedding upon activation with Toll-like receptor-agonists in selected cases.

RESULTS

We identified a total of 68 children with IPD, with a mortality of 6%. Immunological investigations were performed in 51 children. Four children (8%) had abnormal findings that were deemed of clinical significance. Two children had complement deficiencies (Factor I and C2 deficiency), one child had specific antibody deficiency, and another child had low IgM, low NK-cells and poor persistence of serotype-specific anti-pneumococcal IgG concentrations. Of the 17 children with IPD who were not tested for immunodeficiencies, 4 died and four had possible explanations for the infection.

CONCLUSIONS

We identified clinically relevant abnormal immunological findings in 4/51 (8%) of children with IPD. Our results support the recommendation to perform immunological investigations in children with IPD, since this might reveal underlying immunodeficiencies, allowing for necessary preventive measures and close follow-up.

Clinical Presentations and Outcomes of Children in Canada With Recurrent Invasive Pneumococcal Disease From the IMPACT Surveillance Network

BACKGROUND

Invasive pneumococcal disease due to Streptococcus pneumoniae can cause mortality and severe morbidity due to sepsis, meningitis and pneumonia, particularly in young children and the elderly. Recurrent invasive pneumococcal disease is rare yet serious sequelae of invasive pneumococcal disease that is associated with the immunocompromised and leads to a high mortality rate.

METHOD

This retrospective study reviewed recurrent invasive pneumococcal disease cases from the Canadian Immunization Monitoring Program, ACTive (IMPACT) between 1991 and 2019, an active network for surveillance of vaccine-preventable diseases and adverse events following immunization for children ages 0-16 years. Data were collected from 12 pediatric tertiary care hospitals across all 3 eras of public pneumococcal conjugate vaccine implementation in Canada.

RESULTS

The survival rate within our cohort of 180 recurrent invasive pneumococcal disease cases was 98.3%. A decrease of 26.4% in recurrent invasive pneumococcal disease due to vaccine serotypes was observed with pneumococcal vaccine introduction. There was also a 69.0% increase in the rate of vaccination in children with preexisting medical conditions compared with their healthy peers.

CONCLUSION

The decrease in recurrent invasive pneumococcal disease due to vaccine-covered serotypes has been offset by an increase of non-vaccine serotypes in this sample of Canadian children.

Prevalence of Pathogenic and Potentially Pathogenic Inborn Error of Immunity Associated Variants in Children with Severe Sepsis

PURPOSE

Our understanding of inborn errors of immunity is increasing; however, their contribution to pediatric sepsis is unknown.

METHODS

We used whole-exome sequencing (WES) to characterize variants in genes related to monogenic immunologic disorders in 330 children admitted to intensive care for severe sepsis. We defined candidate variants as rare variants classified as pathogenic or potentially pathogenic in QIAGEN's Human Gene Mutation Database or novel null variants in a disease-consistent inheritance pattern. We investigated variant correlation with infection and inflammatory phenotype.

RESULTS

More than one in two children overall and three of four African American children had immunodeficiency-associated variants. Children with variants had increased odds of isolating a blood or urinary pathogen (blood: OR 2.82, 95% CI: 1.12-7.10, p = 0.023, urine: OR: 8.23, 95% CI: 1.06-64.11, p = 0.016) and demonstrating increased inflammation with hyperferritinemia (ferritin [Formula: see text] ng/mL, OR: 2.16, 95% CI: 1.28-3.66, p = 0.004), lymphopenia (lymphocyte count < 1000/µL, OR: 1.66, 95% CI: 1.06 - 2.60, p = 0.027), thrombocytopenia (platelet count < 150,000/µL, OR: 1.76, 95% CI: 1.12-2.76, p = 0.013), and CRP greater than 10 mg/dl (OR: 1.71, 95% CI: 1.10-2.68, p = 0.017). They also had increased odds of requiring extracorporeal membrane oxygenation (ECMO, OR: 4.19, 95% CI: 1.21-14.5, p = 0.019).

CONCLUSION

Herein, we describe the genetic findings in this severe pediatric sepsis cohort and their microbiologic and immunologic significance, providing evidence for the phenotypic effect of these variants and rationale for screening children with life-threatening infections for potential inborn errors of immunity.

Combined Therapeutics for Atherosclerosis Treatment Using Polymeric Nanovectors

Atherosclerosis is an underlying risk factor in cardiovascular diseases (CVDs). The combination of drugs with microRNAs (miRNA) inside a single nanocarrier has emerged as a promising anti-atherosclerosis strategy to achieve the exploitation of their complementary mechanisms of action to achieve synergistic therapeutic effects while avoiding some of the drawbacks associated with current systemic statin therapies. We report the development of nanometer-sized polymeric PLGA nanoparticles (NPs) capable of simultaneously encapsulating and delivering miRNA-124a and the statin atorvastatin (ATOR). The polymeric NPs were functionalized with an antibody able to bind to the vascular adhesion molecule-1 (VCAM1) overexpressed in the inflamed arterial endothelium. The dual-loaded NPs were non-toxic to cells in a large range of concentrations, successfully attached overexpressed VCAM receptors and released the cargoes in a sustainable manner inside cells. The combination of both ATOR and miRNA drastically reduced the levels of proinflammatory cytokines such as IL-6 and TNF-α and of reactive oxygen species (ROS) in LPS-activated macrophages and vessel endothelial cells. In addition, dual-loaded NPs precluded the accumulation of low-density lipoproteins (LdL) inside macrophages as well as morphology changes to a greater extent than in single-loaded NPs. The reported findings validate the present NPs as suitable delivery vectors capable of simultaneously targeting inflamed cells in atherosclerosis and providing an efficient approach to combination nanomedicines.

Investigation of Concurrent Pneumococcal Meningitis in Two Children Attending the Same Day-Care Center

Only a few clusters of invasive pneumococcal disease have been described globally in children, and most of these cases occurred before pneumococcal vaccination implementation. Two unusual cases of pneumococcal meningitis, occurring in the same daycare center over a 3-day period, were reported. Both cerebrospinal fluid (CSF) were sent to the National reference center for pneumococci. In addition, we decided to perform a pneumococcal carriage study on all children and staff of the daycare center to analyze the pneumococcal serotypes circulating in this DCC and to discuss an antibiotic chemoprophylaxis. CSF culture was positive for pneumococcus, and serotype 25A was identified by latex agglutination. The second case had negative CSF culture, but CSF antigen test and gene amplification results were positive for Streptococcus pneumoniae. Serotype 12F was identified by using molecular biology. The absence of correlation between these strains was confirmed by multi-locus sequence typing. In the carriage study, we included 29 children (median age 1.9 years, interquartile range 1.4-2.5) and 10 adults. Among the children, 24 carried Streptococcus pneumoniae (83%). The main serotypes isolated were 23A for 6 children and 25A for 5 children; serotypes were non-typeable for 3 children. Only 1 of 10 adults tested carried Streptococcus pneumoniae (serotype 12F). Despite this temporo-spatial pattern, the cases were unrelated and not due to carriage of a particular serotype. No specific action has been taken for the other children attending this DCC, and no other case of bacterial meningitis occurred.

Estimating the risk of recurrent invasive pneumococcal disease in Australia, 1991-2016

BACKGROUND

Individuals who experience an initial episode of invasive pneumococcal disease (IPD) are at increased risk of recurrent episodes. However, the magnitude of risk has not been well-quantified in the pneumococcal conjugate vaccine era. Individuals with a previous episode of IPD are not commonly identified as a high-risk group in vaccination guidelines.

METHODS

Australian residents with at least one case of IPD between 1991 and 2016 were identified using routine public health surveillance data which included identified IPD risk factors. Incidence of recurrent IPD was calculated from 2001 onwards (after IPD became nationally notifiable) using time-to-event analyses with individuals contributing person-time at risk of recurrence if they survived greater than 14 days after initial episode onset.

RESULTS

From 1991 to 2016 there were 28,809 IPD episodes in 28,218 individuals. A total of 512 (1.8%) persons experienced 591 recurrent episodes. From 2001 to 2016 the incidence of recurrent IPD was 216.2 per 100,000 person-years, 27 times greater than the population rate of primary IPD during this period (8.0 per 100,000 population per year). Between 2011 and 2016, more than one-quarter of individuals experiencing recurrence had no IPD risk factors identified at first episode.

CONCLUSIONS

There is substantially increased risk of recurrent IPD after an initial episode. At least one-quarter of those with recurrent episodes have no identified risk factors at the initial episode. Given the potential preventability of future episodes, those with a previous IPD episode should be identified as a high-risk group and receive pneumococcal vaccination.

Paediatric pneumonia in high-income countries: Defining and recognising cases at increased risk of severe disease

World Health Organisation definitions of pneumonia severity are routinely used in research. In high income health care settings with high rates of pneumococcal vaccination and low rates of mortality, malnutrition and HIV infection, these definitions are less applicable. National guidelines from leading thoracic and infectious disease societies describe 'severe pneumonia' according to criteria derived from expert consensus rather than a robust evidence base. Contemporary cohort studies have used clinical outcomes such as intensive care therapy or invasive procedures for complicated pneumonia, to define severe disease. Describing severe pneumonia in such clinically relevant terms facilitates the identification of risk factors associated with worsened disease and the subsequently increased morbidity, and need for tertiary level care. The early recognition of children at higher risk of severe pneumonia informs site of care decisions, antibiotic treatment decisions as well as guiding appropriate investigations. Younger age, malnutrition, comorbidities, tachypnoea, and hypoxia have been identified as important associations with 'severe pneumonia' by WHO definition. Most studies have been performed in low-middle income countries and whilst they provide some insight into those at risk of mortality or treatment failure, their generalisability to the high-income setting is limited. There is a need to determine more precise definitions and criteria for severe disease in well-resourced settings and to validate factors associated with intensive care admission or invasive procedures to enhance the early recognition of those at risk.

Predisposing conditions for bacterial meningitis in children: what radiologists need to know

A variety of underlying diseases can predispose infants and children to bacterial meningitis (BM). For the diagnosis, treatment, and prevention of its recurrence, radiologists should be familiar with its predisposing conditions so that they can suggest the appropriate imaging approach. Predisposing conditions of BM can be broadly classified into two categories: infection spread from the adjacent tissue to the cerebrospinal fluid (CSF) space and immunodeficiency. Diseases in the former category are further divided according to regardless of whether there is a structural defect between the CSF space and the adjacent tissue. When a structural defect is suspected in a patient with BM, computed tomography (CT) of the head and magnetic resonance (MR) imaging are first-line imaging examinations. Radionuclide cisternography should be implemented as a second-line step to identify the CSF leak site. In patients with suspected parameningeal infection without any structural defect, such as sinusitis or otitis media/mastoiditis, CT or MR images can identify not only the disease itself but also the associated intracranial complications. The purpose of this article is to discuss the diagnostic approach and imaging findings associated with the variety of conditions predisposing patients to recurrent BM, focusing on the role of radiology in their management.

Characteristics of Pediatric Recurrent Bacterial Meningitis in Beijing Children's Hospital, 2006-2019

BACKGROUND

Few data on recurrent bacterial meningitis (RBM) in children are available. Here, we estimated the frequency of RBM in children and investigated the predisposing conditions, etiology, and clinical characteristics of RBM in children.

METHODS

Cases of RBM in the Beijing Children's Hospital medical record database between January 2006 and December 2019 were collected.

RESULTS

In total, 1905 children with bacterial meningitis (BM) were documented in the Beijing Children's Hospital medical record database. A total of 43 patients had RBM. The rate of RBM in children was 2.3% (43/1905). Forty (93.0%) patients had predisposing conditions, including 15 (34.9%) cases of inner ear malformations, 5 (11.6%) cases of dermal sinus tracts, 9 (20.9%) cases of head injury, 5 (11.6%) cases of congenital cranial meningocele, 3 (7.0%) cases of congenital skull base defects, 3 (7.0%) cases of immunodeficiency, and other 3 (7.0%) cases of unknown reason. Among all the 121 BM episodes, a total of 64 episodes were etiologically confirmed BM and the other 57 episodes were probable BM. Streptococcus pneumoniae (n = 52) was accounted for 81.3% of confirmed BM episodes. Thirty-four of the 37 patients with congenital or acquired anatomical defects were available to follow up after surgeries, and all of them had no BM after surgeries. Three patients with antibody deficiencies got intravenous immunoglobulin therapy and they did not suffer BM anymore.

CONCLUSIONS

RBM is rare in children. The majority of children with RBM had predisposing conditions including congenital/acquired anatomical defects and immunodeficiency. Interventions should be implemented to solve the underlying conditions to avoid RBM.

Investigation of primary immune deficiency after severe bacterial infection in children: A population-based study in western France

BACKGROUND

Infectious diseases are still an important cause of morbidity and mortality in high-income countries and may preferentially affect predisposed children, especially immunocompromised children. We aimed to evaluate the frequency of recommended immunological tests in children with community-onset severe bacterial infection (COSBI) admitted to a pediatric intensive care unit. We also assessed the frequency and described the typology of diagnosed primary immune deficiency (PID).

METHODS

We conducted a retrospective observational epidemiological study in six university hospitals in western France. All children from 1 month to 16 years of age admitted to hospital for bacterial meningitis, purpura fulminans, or meningococcal disease between August 2009 and January 2014 were included. We analyzed the frequency, type, and results of the immunological tests performed on children with meningitis, purpura fulminans, or a meningococcemia episode.

RESULTS

Among the 143 children included (144 episodes), 84 (59%) and 60 (41%) had bacterial meningitis and purpura fulminans or meningococcemia, respectively: 72 (50%) had immunological tests and 8% had a complete immunological investigation as recommended. Among the 72 children examined for PID, 11 (15%) had at least one anomaly in the immunological test results. Two children had a diagnosis of PID (one with C2 deficit and the other with C8 deficit) and seven other children had possible PID. Thus, the prevalence of a definite or possible diagnosis of PID was 12% among the children examined.

CONCLUSION

PID is rarely investigated after COSBI. We raise awareness of the need for immunological investigations after a severe infection requiring PICU admission.

Lessons Learned From the Clinical Presentation of Common Variable Immunodeficiency Disorders: A Systematic Review and Meta-Analysis

Background

Diagnostic delay in common variable immunodeficiency disorders (CVID) is considerable. There is no generally accepted symptom-recognition framework for its early detection.

Objective

To systematically review all existing data on the clinical presentation of CVID.

Methods

PubMed, EMBASE and Cochrane were searched for cohort studies, published January/1999-December/2019, detailing the clinical manifestations before, at and after the CVID-diagnosis.

Results

In 51 studies (n=8521 patients) 134 presenting and 270 total clinical manifestations were identified. Recurrent upper and/or lower respiratory infections were present at diagnosis in 75%. Many patients had suffered severe bacterial infections (osteomyelitis 4%, meningitis 6%, septicemia 8%, mastoiditis 8%). Bronchiectasis (28%), lymphadenopathy (27%), splenomegaly (13%), inflammatory bowel disease (11%), autoimmune cytopenia (10%) and idiopathic thrombocytopenia (6%) were also frequently reported. A bimodal sex distribution was found, with male predominance in children (62%) and female predominance in adults (58%). 25% of CVID-patients developed other manifestations besides infections in childhood, this percentage was much higher in adults (62%). Immune-dysregulation features, such as granulomatous-lymphocytic interstitial lung disease and inflammatory bowel disease, were more prominent in adults.

Conclusions

The shift from male predominance in childhood to female predominance in adults suggests differences in genetic and environmental etiology in CVID and has consequences for pathophysiologic studies. We confirm the high frequency of respiratory infections at presentation, but also show a high incidence of severe bacterial infections such as sepsis and meningitis, and immune dysregulation features including lymphoproliferative, gastrointestinal and autoimmune manifestations. Early detection of CVID may be improved by screening for antibody deficiency in patients with these manifestations.

Whole-exome Sequencing for the Identification of Rare Variants in Primary Immunodeficiency Genes in Children With Sepsis: A Prospective, Population-based Cohort Study

BACKGROUND

The role of primary immunodeficiencies (PID) in susceptibility to sepsis remains unknown. It is unclear whether children with sepsis benefit from genetic investigations. We hypothesized that sepsis may represent the first manifestation of underlying PID. We applied whole-exome sequencing (WES) to a national cohort of children with sepsis to identify rare, predicted pathogenic variants in PID genes.

METHODS

We conducted a multicenter, population-based, prospective study including previously healthy children aged ≥28 days and <17 years admitted with blood culture-proven sepsis. Using a stringent variant filtering procedure, analysis of WES data was restricted to rare, predicted pathogenic variants in 240 PID genes for which increased susceptibility to bacterial infection has been reported.

RESULTS

There were 176 children presenting with 185 sepsis episodes who underwent WES (median age, 52 months; interquartile range, 15.4-126.4). There were 41 unique predicted pathogenic PID variants (1 homozygous, 5 hemizygous, and 35 heterozygous) found in 35/176 (20%) patients, including 3/176 (2%) patients carrying variants that were previously reported to lead to PID. The variants occurred in PID genes across all 8 PID categories, as defined by the International Union of Immunological Societies. We did not observe a significant correlation between clinical or laboratory characteristics of patients and the presence or absence of PID variants.

CONCLUSIONS

Applying WES to a population-based cohort of previously healthy children with bacterial sepsis detected variants of uncertain significance in PID genes in 1 out of 5 children. Future studies need to investigate the functional relevance of these variants to determine whether variants in PID genes contribute to pediatric sepsis susceptibility.

Paediatric sepsis

PURPOSE OF REVIEW

Sepsis remains among the leading causes of childhood mortality worldwide. This review serves to highlight key areas of knowledge gain and ongoing controversies pertinent to sepsis in children.

RECENT FINDINGS

Several recent publications describe the epidemiology of paediatric sepsis, demonstrating the impact on child health in terms of mortality and morbidity, and the shortcomings of current paediatric sepsis definitions. Although emerging data support the importance of organ dysfunction as a hallmark of paediatric sepsis, the understanding of host susceptibility to sepsis and to sepsis severity remains very limited. Next-generation sequencing and host transcriptomics have the potential to provide new insights into the pathogenesis of sepsis and may enable personalized medicine approaches. Despite good observational data indicating benefit of sepsis recognition and treatment bundles, the evidence for the individual bundle components remains scarce, implying an urgent need for large trials.

SUMMARY

Recent studies have demonstrated distinct epidemiological patterns pertinent to age groups, healthcare settings, and comorbidities in the era post meningococcal epidemics. Although sepsis quality improvement initiatives have led to substantial outcome improvements, there is urgency for innovative trials to reduce uncertainty around the optimal approach for the recognition and treatment of sepsis in children.

Hereditary Deficiency of the Second Component of Complement: Early Diagnosis and 21-Year Follow-Up of a Family

Complement deficiencies are rare and often underdiagnosed primary immunodeficiencies that may be associated with invasive bacterial diseases. Serious infections with encapsulated organisms (mainly Streptococcus pneumoniae, but also Neisseria meningitides and Haemophilus influenzae type B) are frequent in patients with a deficiency of the second component of complement (C2), but no data are available on long-term follow-up. This study aimed to evaluate the long-term clinical outcome and the importance of an early diagnosis and subsequent infection prophylaxis in C2 deficiency. Here, we report the 21-year follow-up of a whole family which was tested for complement parameters, genetic analysis and biochemical measurements, due to recurrent pneumococcal meningitis in the elder brother. The two sons were diagnosed with homozygous type 1 C2 deficiency, while their parents were heterozygous with normal complement parameters. For the two brothers, a recommended vaccination program and antibiotic prophylaxis were prescribed. During the long-term follow-up, no severe/invasive infections were observed in either patient. At the age of 16, the younger brother developed progressive hypogammaglobulinemia of all three classes, IgA, IgM and IgG. A next generation sequencing panel excluded the presence of gene defects related to primary antibody deficiencies. Our data show that early diagnosis, use of vaccinations and antibiotic prophylaxis may allow a normal life in hereditary C2 deficiency, which can be characterized using functional and genetic methods. Moreover, a periodical check of immunoglobulin serum levels could be useful to detect a possible hypogammaglobulinemia.

Recurrent Pneumococcal Meningitis Secondary to Nasoethmoidal Meningocele

Since the widespread introduction of the conjugate pneumococcal vaccine and subsequent decline of invasive pneumococcal disease in children, a significant proportion of children with pneumococcal meningitis are identified as having an underlying immunodeficiency or predisposing anatomic abnormality. We present 3 cases of recurrent pneumococcal meningitis where detailed neuro-imaging revealed subtle anterior base of skull defects not detected on initial investigations.

Changing Epidemiology and Predisposing Factors for Invasive Pneumococcal Disease at Two Australian Tertiary Hospitals

BACKGROUND

Invasive pneumococcal disease (IPD) is associated with significant morbidity and mortality in children. Universal pneumococcal conjugate vaccination has changed the epidemiology of IPD. In vaccinated children, IPD can be a marker of an underlying immunodeficiency.

METHODS

This is a retrospective audit of children younger than 18 years with IPD admitted to 2 tertiary pediatric hospitals in Australia between 2011 and 2017. Data on predisposing conditions, immunologic evaluation, pneumococcal serotype, antibiotic susceptibility and treatment were collected.

RESULTS

During the 7-year period, there were 131 presentations with IPD in 127 children; 3 children had recurrent IPD. Patients presented with sepsis (41%), empyema (29%), meningitis (18%), mastoiditis (12%), pneumonia (10%) and septic arthritis (4%). In 19 (15%) presentations, risk factors for IPD were present, including malignancy, hematologic disorder, chronic liver disease, chronic kidney disease and cochlear implant. Pneumococcal serotypes were determined in 78/131 (60%) of presentations: the most frequent serotypes were 19A (19%), 3 (13%), 7F (10%) and 19F (8%) and non-vaccine serotypes 22F (8%), 35B (6%), 15A (4%) and 38 (4%). Overall, 11% of isolates were non-susceptible to ceftriaxone. Only 36 patients (32%) had an immunologic evaluation, and 4 patients had proven or probable immunodeficiency.

CONCLUSION

Although pneumococcal conjugate vaccine serotypes 19A, 3, 19F and 7F remain frequent causes of IPD, non-vaccine serotypes are emerging. Our data support vancomycin treatment for children with pneumococcal meningitis given 11% of our isolates were not susceptible to ceftriaxone. It is important to consider underlying conditions predisposing to IPD in a population with high rates of pneumococcal vaccination.

Prevalence of Immunodeficiency in Children With Invasive Pneumococcal Disease in the Pneumococcal Vaccine Era: A Systematic Review

IMPORTANCE

Despite increasing access to vaccination, invasive pneumococcal disease (IPD) is responsible for approximately 826 000 deaths worldwide in children younger than 5 years each year. To allow early identification and prevention, an improved understanding of risk factors for IPD is needed.

OBJECTIVES

To review the literature on the prevalence of primary immunodeficiency (PID) in children younger than 18 years presenting with IPD without another predisposing condition and to inform guidelines for immunologic evaluation after the first episode of IPD based on published evidence.

EVIDENCE REVIEW

A literature search of PubMed, Embase (inception [1974] to February 28, 2019), and MEDLINE (inception [1946] to February 28, 2019) was conducted using the terms Streptococcus pneumonia, Streptococcus pneumoniae, pneumococcal infection, Streptococcus infection, pneumococcal meningitis, immunodeficiency, immune response, immunocompromised, susceptib*, precursor, predispose*, recurren*, newborn, neonat*, infan*, toddler, child, preschooler, adolescen*, and pediatric. Publications reporting original data on immunodeficiency in children with microbiologically confirmed primary or recurrent IPD were included. Strength of clinical data was graded according to the 5-point scale of the Oxford Centre for Evidence-Based Medicine.

FINDINGS

In 6022 unique children with primary IPD, 5 of 393 (1.3%) to 17 of 162 (10.5%) of all children and 14 of 53 (26.4%) of those older than 2 years had a PID identified. Higher rates of PID, up to 10 of 15 (66.7%), were found in children with recurrent IPD. Antibody deficiency was the most common immunodeficiency, followed by complement deficiency, asplenia, and rarer defects in T-cell signaling. The site of infection was a key indicator for the risk of underlying PID, with the greatest risk of PID in children with meningitis or complicated pneumonia.

CONCLUSIONS AND RELEVANCE

Results of this study suggest that invasive pneumococcal disease, and particularly recurrent IPD, is an important marker of underlying PID in children without other risk factors. The findings also suggest that children older than 2 years with pneumococcal meningitis or complicated pneumonia and all children with recurrent IPD should be referred for an immune evaluation.

TRIAL REGISTRATION

PROSPERO identifier: CRD42017075978.

Prevalence of Hypogammaglobulinemia in Adult Invasive Pneumococcal Disease

Background

Patients with humoral immune deficiency are susceptible to invasive pneumococcal disease (IPD). This study estimates the prevalence of underlying hypogammaglobulinemia in admitted IPD cases and examines whether IPD cases had received preventative treatment.

Methods

All adult IPD cases (Streptococcus pneumoniae in blood or cerebrospinal fluid) admitted to The Ottawa Hospital (TOH) from January 2013 to December 2015 were identified through the Eastern Ontario Regional Laboratory. Documented clinical demographics, S. pneumoniae serotype, serum immunoglobulins measured previously or in convalescence, and vaccination status of the cases were collected retrospectively for descriptive analyses.

Results

There were 134 IPD in 133 patients (47.4% male; mean age 63, standard deviation [SD] = 15.6 years) during a 3-year observation period. All-cause mortality rate was 22.6% over a mean follow-up time of 362, SD = 345 days. Fifty-seven patients (42.9%) had serum immunoglobulin levels measured. Eighteen were either found to have hypogammaglobulinemia in convalescence (8/18) or previously known to have hypogammaglobulinemia (10/18). None of the known hypogammaglobulinemic patients had received antibiotic prophylaxis and/or immunoglobulin replacement therapy within 4 months prior to IPD. The high and low estimates of prevalence of hypogammaglobulinemia were 31.6% (of all measured) and 13.5% (of all cases). Among 18 patients with hematological malignancies in our cohort, 13 had hypogammaglobulinemia. Many isolates were vaccine serotypes; however, only 8 had documented previous pneumococcal vaccination.

Conclusions

IPD has high mortality, and hypogammaglobulinemia was present in at least 13.5% of IPD cases. Secondary hypogammaglobulinemia is especially common in cases with hematological malignancy and IPD.

Recurrent Pneumococcal Meningitis in Children: A Multicenter Case-control Study

BACKGROUND

Pneumococcal meningitis (PM) is a serious disease that can rarely recur at a later time after the initial episode.

METHODS

A retrospective multicenter case-control study was conducted with data for children 18 years of age or younger obtained from the National Observatory of Bacterial Meningitis in Children between January 2001 and September 2015. Cases were all patients with RPM. Each case was matched with 2 randomized controls with a single PM episode in the year of the first episode of PM in the case and born the same year. Case and control data were compared.

RESULTS

Among the 1634 PM episodes in children 18 years of age or younger, 24 (1.5%) children had RPM. RPM cases were significantly less frequent than single PM cases in winter (27% vs. 48%; P=0.03) and showed significantly less concomitant ear, nose and throat infections when considering the first episode (30% vs. 56%, P = 0.04) and all episodes (28% vs. 56%, P < 0.01). Cerebrospinal fluid leakage was frequent in RPM cases versus controls (83% vs. 10%, P < 0.01), including 25% discovered after the third PM episode. Immune deficiency was absent in cases and present in 15% of controls. Cases and controls did not differ in death rate or neurologic outcome.

CONCLUSIONS

RPM is rare in children. Cerebrospinal fluid leakage must be considered.

Invasive Pneumococcal Disease in Children's Hospitals: 2014-2017

BACKGROUND

The 13-valent pneumococcal conjugate vaccine (PCV13) was licensed in the United States in 2010. We describe invasive pneumococcal disease (IPD) in children at 8 children's hospitals in the US from 2014 to 2017.

METHODS

Children with IPD occurring from 2014 to 2017 were identified from a prospective study. Demographic and clinical data, including results of any immune evaluation along with the number and dates of previous pneumococcal conjugate vaccines administered, were recorded on case report forms. Isolate serotypes were determined in a central laboratory. Pneumococcal conjugate vaccine doses were counted if IPD occurred ≥2 weeks after a dose.

RESULTS

PCV13 serotypes accounted for 23.9% (115 out of 482) of IPD isolates from 2014 to 2017. Serotypes 3, 19A, and 19F accounted for 91% of PCV13 serotypes. The most common non-PCV13 serotypes were 35B, 23B, 33F, and 22F. An underlying condition was significantly (P < .0001) more common in children with IPD due to non-PCV13 serotypes (200 out of 367, 54.5%) than for children with PCV13 serotypes (27 out of 115, 23.5%). An immune evaluation was undertaken in 28 children who received ≥2 PCV13 doses before IPD caused by a PCV13 serotype. Only 1 was found to have an immunodeficiency.

CONCLUSIONS

PCV13 serotypes (especially serotypes 3, 19A, and 19F) continue to account for nearly a quarter of IPD in US children 4 to 7 years after PCV13 was introduced. Underlying conditions are more common in children with non-PCV13 serotype IPD. Immune evaluations in otherwise healthy children with PCV13 serotype IPD despite receiving ≥2 PCV13 doses did not identify an immunodeficiency.

Clinical and Genetic Spectrum of a Large Cohort With Total and Sub-total Complement Deficiencies

The complement system is crucial for defense against pathogens and the removal of dying cells or immune complexes. Thus, clinical indications for possible complete complement deficiencies include, among others, recurrent mild or serious bacterial infections as well as autoimmune diseases (AID). The diagnostic approach includes functional activity measurements of the classical (CH50) and alternative pathway (AP50) and the determination of the C3 and C4 levels, followed by the quantitative analysis of individual components or regulators. When biochemical analysis reveals the causal abnormality of the complement deficiency (CD), molecular mechanisms remains frequently undetermined. Here, using direct sequencing analysis of the coding region we report the pathogenic variants spectrum that underlie the total or subtotal complement deficiency in 212 patients. We identified 107 different hemizygous, homozygous, or compound heterozygous pathogenic variants in 14 complement genes [C1Qβ (n = 1), C1r (n = 3), C1s (n = 2), C2 (n = 12), C3 (n = 5), C5 (n = 12), C6 (n = 9), C7 (n = 17), C8 β (n = 7), C9 (n = 3), CFH (n = 7), CFI (n = 18), CFP (n = 10), CFD (n = 2)]. Molecular analysis identified 17 recurrent pathogenic variants in 6 genes (C2, CFH, C5, C6, C7, and C8). More than half of the pathogenic variants identified in unrelated patients were also found in healthy controls from the same geographic area. Our study confirms the strong association of meningococcal infections with terminal pathway deficiency and highlights the risk of pneumococcal and auto-immune diseases in the classical and alternative pathways. Results from this large genetic investigation provide evidence of a restricted number of molecular mechanisms leading to complement deficiency and describe the clinical potential adverse events of anti-complement therapy.

Characteristics and Serotype Distribution of Childhood Cases of Invasive Pneumococcal Disease Following Pneumococcal Conjugate Vaccination in England and Wales, 2006-2014

Background

The 7-valent and 13-valent pneumococcal conjugate vaccines (PCV7 and PCV13, respectively) are highly effective in preventing invasive pneumococcal disease (IPD) caused by vaccine serotypes. Vaccine failure (vaccine-type IPD after age-appropriate immunization) is rare. Little is known about the risk, clinical characteristics, or outcomes of PCV13 compared to PCV7 vaccine failure.

Methods

Public Health England conducts IPD surveillance and provides a national reference service for serotyping pneumococcal isolates in England and Wales. We compared the epidemiology, rates, risk factors, serotype distribution, clinical characteristics, and outcomes of IPD in children with PCV13 and PCV7 vaccine failure.

Results

A total of 163 episodes of PCV failure were confirmed in 161 children over 8 years (4 September 2006 to 3 September 2014) in 10 birth cohorts. After 3 vaccine doses, PCV7 and PCV13 failure rates were 0.19/100000 (95% confidence interval [CI], .10-.33 [57 cases]) and 0.66/100000 (95% CI, .44-.95 [104 cases]) vaccinated person-years, respectively. Children with PCV13 failure were more likely to be healthy (87/105 [82.9%] vs 37/56 [66.1%]; P = .02), present with bacteremic lower respiratory tract infection (LRTI) (61/105 [58.1%] vs 11/56 [19.6%]; P < .001), and develop empyema (41/61 [67.2%] vs 1/11 [9.1%]; P < .001) compared to PCV7 failures. Serotypes 3 (n = 38 [36.2%]) and 19A (n = 30 [28.6%]) were responsible for most PCV13 failures. Six children died (4% [95% CI, 1%-8%]), including 5 with comorbidities.

Conclusions

PCV failure is rare and, compared to PCV7 serotypes, the additional PCV13 serotypes are more likely to cause bacteremic LRTI and empyema in healthy vaccinated children.

Classical and Non-classical Presentations of Complement Factor I Deficiency: Two Contrasting Cases Diagnosed via Genetic and Genomic Methods

Deficiency of complement factor I is a rare immunodeficiency that typically presents with increased susceptibility to encapsulated bacterial infections. However, non-infectious presentations including rheumatological, dermatological and neurological disease are increasingly recognized and require a high-index of suspicion to reach a timely diagnosis. Herein, we present two contrasting cases of complement factor I deficiency: one presenting in childhood with invasive pneumococcal disease, diagnosed using conventional immunoassays and genetics and the second presenting in adolescence with recurrent sterile neuroinflammation, diagnosed via a genomic approach. Our report and review of the literature highlight the wide spectrum of clinical presentations associated with CFI deficiency and the power of genomic medicine to inform rare disease diagnoses.

Lessons learned from the study of human inborn errors of innate immunity

Innate immunity contributes to host defense through all cell types and relies on their shared germline genetic background, whereas adaptive immunity operates through only 3 main cell types, αβ T cells, γδ T cells, and B cells, and relies on their somatic genetic diversification of antigen-specific responses. Human inborn errors of innate immunity often underlie infectious diseases. The range and nature of infections depend on the mutated gene, the deleteriousness of the mutation, and other ill-defined factors. Most known inborn errors of innate immunity to infection disrupt the development or function of leukocytes other than T and B cells, but a growing number of inborn errors affect cells other than circulating and tissue leukocytes. Here we review inborn errors of innate immunity that have been recently discovered or clarified. We highlight the immunologic implications of these errors.

Complement depletion and Coombs positivity in pneumococcal hemolytic uremic syndrome (pnHUS). Case series and plea to revisit an old pathogenetic concept

Hemolytic uremic syndrome is a rare complication of invasive pneumococcal infection (pnHUS). Its pathogenesis is poorly understood, and treatment remains controversial. The emerging role of complement in various forms of HUS warrants a new look at this "old" disease. We performed a retrospective analysis of clinical and laboratory features of three sequential cases of pnHUS since 2008 associated with pneumonia/pleural empyema, two due to Streptococcus pneumoniae serotype 19 A. Profound depletion of complement C3 (and less of C4) was observed in two patients. One patient was Coombs test positive. Her red blood cells (RBCs) strongly agglutinated with blood group compatible donor serum at 0 °C, but not at 37 °C. All three patients were treated with hemodialysis, concentrated RBCs, and platelets. Patient 2 received frozen plasma for hepatic failure with coagulation factor depletion. Intravenous immunoglobulin infusion, intended to neutralize pneumococcal neuraminidase in patient 3, was associated with rapid normalization of platelets and cessation of hemolysis. Two patients recovered without sequelae or disease recurrence. Patient 2 died within 2½ days of admission due to complicating Pseudomonas aeruginosa sepsis and multiorgan failure. Our observations suggest that pnHUS can be associated with dramatic, transient complement consumption early in the course of the disease, probably via the alternative pathway. A critical review of the literature and the reported cases argue against the postulated pathological role of preformed antibodies against the neuraminidase-exposed Thomsen-Friedenreich neoantigen (T antigen) in pnHUS. The improved understanding of complement regulation and bacterial strategies of complement evasion allows to propose a testable, new pathogenetic model of pnHUS. This model shifts emphasis from the action of natural anti-T antibodies toward impaired Complement Factor H (CFH) binding and function on desialylated membranes. Removal of neuraminic acid residues converts (protected) self to non-self surfaces that supports membrane attack complex (MAC) assembly. Complement activation is potentially exacerbated by decreased CFH availability following tight CFH binding to pneumococcal evasion proteins and/or by the presence of genetic variants of complement regulator proteins. Detailed clinical and experimental investigations are warranted to better understand the role of unregulated complement activation in pnHUS. Instead of avoidance of plasma, a new, integrated model is evolving, which may include short-term therapeutic complement blockade, particularly where genetic or functional APC dysregulation is suspected, in addition to bacterial elimination and, potentially, neuraminidase neutralization.

Mortality and morbidity in community-acquired sepsis in European pediatric intensive care units: a prospective cohort study from the European Childhood Life-threatening Infectious Disease Study (EUCLIDS)

BACKGROUND

Sepsis is one of the main reasons for non-elective admission to pediatric intensive care units (PICUs), but little is known about determinants influencing outcome. We characterized children admitted with community-acquired sepsis to European PICUs and studied risk factors for mortality and disability.

METHODS

Data were collected within the collaborative Seventh Framework Programme (FP7)-funded EUCLIDS study, which is a prospective multicenter cohort study aiming to evaluate genetic determinants of susceptibility and/or severity in sepsis. This report includes 795 children admitted with community-acquired sepsis to 52 PICUs from seven European countries between July 2012 and January 2016. The primary outcome measure was in-hospital death. Secondary outcome measures were PICU-free days censured at day 28, hospital length of stay, and disability. Independent predictors were identified by multivariate regression analysis.

RESULTS

Patients most commonly presented clinically with sepsis without a source (n = 278, 35%), meningitis/encephalitis (n = 182, 23%), or pneumonia (n = 149, 19%). Of 428 (54%) patients with confirmed bacterial infection, Neisseria meningitidis (n = 131, 31%) and Streptococcus pneumoniae (n = 78, 18%) were the main pathogens. Mortality was 6% (51/795), increasing to 10% in the presence of septic shock (45/466). Of the survivors, 31% were discharged with disability, including 24% of previously healthy children who survived with disability. Mortality and disability were independently associated with S. pneumoniae infections (mortality OR 4.1, 95% CI 1.1-16.0, P = 0.04; disability OR 5.4, 95% CI 1.8-15.8, P < 0.01) and illness severity as measured by Pediatric Index of Mortality (PIM2) score (mortality OR 2.8, 95% CI 1.3-6.1, P < 0.01; disability OR 3.4, 95% CI 1.8-6.4, P < 0.001).

CONCLUSIONS

Despite widespread immunization campaigns, invasive bacterial disease remains responsible for substantial morbidity and mortality in critically ill children in high-income countries. Almost one third of sepsis survivors admitted to the PICU were discharged with some disability. More research is required to delineate the long-term outcome of pediatric sepsis and to identify interventional targets. Our findings emphasize the importance of improved early sepsis-recognition programs to address the high burden of disease.

Evaluation of the Role of stat3 in Antibody and TH17-Mediated Responses to Pneumococcal Immunization and Infection by Use of a Mouse Model of Autosomal Dominant Hyper-IgE Syndrome

Loss-of-function mutations in the signal transducer and activator of transcription 3 gene (stat3) result in autosomal dominant hyper-IgE syndrome (AD-HIES), a condition in which patients have recurrent debilitating infections, including frequent pneumococcal and staphylococcal pneumonias. stat3 mutations cause defective adaptive T_H17 cellular responses, an immune mechanism believed to be critical for clearance of pneumococcal colonization and diminished antibody responses. Here we wished to evaluate the role of stat3 in the clearance of pneumococcal carriage and immunity using mice with a stat3 mutation recapitulating AD-HIES. We show here that naive AD-HIES mice have prolonged nasal carriage of pneumococcus compared to WT mice. Mutant and wild-type mice were then immunized with a pneumococcal whole-cell vaccine (WCV) that provides T_H17-mediated protection against pneumococcal colonization and antibody-mediated protection against pneumonia and sepsis. WCV-immunized AD-HIES mice made significantly less pneumococcus-specific interleukin-17A (IL-17A) and antibody than WT mice. The WCV-elicited protection against colonization was abrogated in AD-HIES mice, but immunization with WCV still protected AD-HIES mice against aspiration pneumonia/sepsis. Taken together, our results suggest that impaired clearance of nasopharyngeal carriage due to poor adaptive IL-17A responses may contribute to the increased rates of pneumococcal respiratory infection in AD-HIES patients.

The Clinical Utility of Measuring IgG Subclass Immunoglobulins During Immunological Investigation for Suspected Primary Antibody Deficiencies

Measurement of IgG subclass concentrations is a standard laboratory test run as part of a panel to investigate the suspicion of antibody deficiency. The assessment is clinically important when total IgG is within the normal age-specific reference range. The measurement is useful for diagnosis of IgG subclass deficiency, to aid the diagnosis of specific antibody deficiency, as a supporting test for the diagnosis of common variable immunodeficiency, as well as for risk stratification of patients with low IgA. The measurement of IgG subclasses may also help determine a revaccination strategy for patients and support patient management. In certain circumstances, the measurement of IgG subclasses may be used to monitor a patient’s humoral immune system. In this review, we discuss the utility of measuring IgG subclass concentrations.

The clinical and laboratory spectrum of dedicator of cytokinesis 8 immunodeficiency syndrome in patients with a unique mutation

Mutations in the dedicator of cytokinesis 8 (DOCK8) gene cause a combined immunodeficiency usually diagnosed as autosomal recessive hyper IgE syndrome. We sought to reveal the varying manifestations in patients with a unique mutation in DOCK8 gene by a retrospective medical record review. Ten patients from five consanguineous families and three tribes were included. Seven patients were homozygous for the c.C5134A, p.S1711X mutation, and the remaining three patients were their siblings manifesting hyper IgE syndrome features without a genetic diagnosis. Prior to the genetic diagnosis, the clinical diagnosis was "hyper IgE syndrome" in six patients and "anti-pneumococcal antibody deficiency," "recurrent pneumonia with bronchiectasis," and "asthma with hypereosinophilic syndrome" each diagnosed once. One additional patient was diagnosed due to family history. The age of presentation varied from 1 to 16 months. Eczema was diagnosed in all patients, food allergies in three, and severe herpes keratitis or malignancy or autoimmunity in two patients. Elevated IgE was recorded in nine patients; however, in six patients, the initial serum IgE concentration was equal to or less than three times the normal concentration for age, and in these patients, the median age at IgE evaluation was 7.5 months compared with 21.5 months in patients with an initial IgE concentration above three times the normal concentration for age (P = 0.067). The spectrum of disease manifestations in patients with a unique mutation in DOCK8 is variable. The genotype-phenotype correlations may be modified by genetic and/or epigenetic modifiers beyond the monogenic effect. Younger patients tend to have lower IgE concentrations at the initial measurement of IgE.

Genetic susceptibility to invasive pneumococcal disease

BACKGROUND

The pathogenesis of IPD remains unknown, especially among middle-aged individuals without risk factors (WRF).

OBJECTIVES

The aim of the present study was to investigate the role of single nucleotide polymorphisms (SNP) within key genes involved in innate immune response on IPD susceptibility.

METHODS

Forty-three SNPs within 10 immunological genes were investigated in a cohort of 144 Caucasian IPD patients and 280 ethnically matched controls.

RESULTS

The allele distribution of the NFKBIA rs1050851 and NFKBIE rs2282151 variants were associated with IPD susceptibility (χ² = 4.23, p = 0.04 and χ² = 5.13, p = 0.02, respectively). Additionally, the genotype distribution of NFKBIZ rs645781 (χ² = 8.25, p = 0.02) and IL1R1 rs3917254 (χ² = 6.70, p = 0.04) were also associated with IPD risk. When only IPD-WRF patients were considered; the allele distribution of IL1R1 rs2160227 (χ² = 5.62, p = 0.03), rs13020778 (χ² = 5.73, p = 0.02), rs3917267 (χ² = 3.72, p = 0.05) and IL4 rs2227284 (χ² = 3.76, p = 0.05) and the genotype distribution of IL10 rs3024509 (χ² = 7.70, p = 0.02), IL1R1 rs3917254 (χ² = 13.40, p = 0.001), NFKBIZ rs645781 (χ² = 13.86, p = 0.001) and rs677011 (χ² = 9.06, p = 0.01) variants were associated with IPD risk.

CONCLUSIONS

We found several associations between variants in the IL1R1, IL4, IL10, NFKBIE, NFKBIA, and NFKBIZ genes and risk of IPD. If validated, these biomarkers may help to identify people with higher risk of IPD.

The Antibody-Secreting Cell Response to Infection: Kinetics and Clinical Applications

Despite the availability of advances in molecular diagnostic testing for infectious disease, there is still a need for tools that advance clinical care and public health. Current methods focus on pathogen detection with unprecedented precision, but often lack specificity. In contrast, the host immune response is highly specific for the infecting pathogen. Serological studies are rarely helpful in clinical settings, as they require acute and convalescent antibody testing. However, the B cell response is much more rapid and short-lived, making it an optimal target for determining disease aetiology in patients with infections. The performance of tests that aim to detect circulating antigen-specific antibody-secreting cells (ASCs) has previously been unclear. Test performance is reliant on detecting the presence of ASCs in the peripheral blood. As such, the kinetics of the ASC response to infection, the antigen specificity of the ASC response, and the methods of ASC detection are all critical. In this review, we summarize previous studies that have used techniques to enumerate ASCs during infection. We describe the emergence, peak, and waning of these cells in peripheral blood during infection with a number of bacterial and viral pathogens, as well as malaria infection. We find that the timing of antigen-specific ASC appearance and disappearance is highly conserved across pathogens, with a peak response between day 7 and day 8 of illness and largely absent following day 14 since onset of symptoms. Data show a sensitivity of ~90% and specificity >80% for pathogen detection using ASC-based methods. Overall, the summarised work indicates that ASC-based methods may be very sensitive and highly specific for determining the etiology of infection and have some advantages over current methods. Important areas of research remain, including more accurate definition of the timing of the ASC response to infection, the biological mechanisms underlying variability in its magnitude and the evolution and the B cell receptor in response to immune challenge. Nonetheless, there is potential of the ASC response to infection to be exploited as the basis for novel diagnostic tests to inform clinical care and public health priorities.

Risk Factors in Children Older Than 5 Years With Pneumococcal Meningitis: Data From a National Network

BACKGROUND

The occurrence of meningitis in children >5 years old may be associated with specific predisposing factors that can be anatomic, such as cerebrospinal fluid fistula or breach, or related to genetic susceptibility or N inborn or acquired immunologic defect. This study aimed to assess the anatomical and immunologic risk factors in children >5 years old with pneumococcal meningitis and prospectively enrolled in the French national meningitis network.

METHODS

We analyzed all data for children who were 5-15 years old with a diagnosis of pneumococcal meningitis between 2001 and 2013. We describe the frequency and typology of the anatomic or immunologic risk factors, the clinical features and the pneumococcal serotypes.

RESULTS

Among the 316 patients with pneumococcal meningitis, the mortality rate was 9.5% and 23.1% of cases presented complications (abscess, coma, hemodynamic failure, thrombophlebitis cerebral or deafness). In total, 108 children (34%) showed risk factors, the most frequent being anatomic: 70 cases (22.8%) were related to a cerebrospinal fluid breach or fistula and 55 (17.9%) to immunodeficiency, primary or acquired. Serotype data were available for 207 pneumococcal isolates (65.5%). The most frequent serotypes were as follows: 3, 18C, 19A and 19F between 2001 and 2009 and 19F, 3, 19A, 12F, 22F, 17F and 24F after 2009.

CONCLUSIONS

We describe the largest cohort of children >5 years old with pneumococcal meningitis. One third of the children had risk factors justifying a complete immunologic and radiologic work-up.

Naturally Acquired Human Immunity to Pneumococcus Is Dependent on Antibody to Protein Antigens

Naturally acquired immunity against invasive pneumococcal disease (IPD) is thought to be dependent on anti-capsular antibody. However nasopharyngeal colonisation by Streptococcus pneumoniae also induces antibody to protein antigens that could be protective. We have used human intravenous immunoglobulin preparation (IVIG), representing natural IgG responses to S. pneumoniae, to identify the classes of antigens that are functionally relevant for immunity to IPD. IgG in IVIG recognised capsular antigen and multiple S. pneumoniae protein antigens, with highly conserved patterns between different geographical sources of pooled human IgG. Incubation of S. pneumoniae in IVIG resulted in IgG binding to the bacteria, formation of bacterial aggregates, and enhanced phagocytosis even for unencapsulated S. pneumoniae strains, demonstrating the capsule was unlikely to be the dominant protective antigen. IgG binding to S. pneumoniae incubated in IVIG was reduced after partial chemical or genetic removal of bacterial surface proteins, and increased against a Streptococcus mitis strain expressing the S. pneumoniae protein PspC. In contrast, depletion of type-specific capsular antibody from IVIG did not affect IgG binding, opsonophagocytosis, or protection by passive vaccination against IPD in murine models. These results demonstrate that naturally acquired protection against IPD largely depends on antibody to protein antigens rather than the capsule.

Rationale and prospects for novel pneumococcal vaccines

Streptococcus pneumoniae remains one of the most frequent bacterial causes of morbidity and mortality worldwide. National immunization programs implementing pneumococcal polysaccharide conjugate vaccines (PCVs) have successfully reduced rates of vaccine-type invasive disease and colonization both via direct effects in immunized children and, in some settings, indirect effects in unimmunized individuals. Limitations of the current PCV approach include the emergence of non-vaccine serotypes contributing to carriage and invasive disease in high-PCV coverage settings and the high cost of goods of PCVs which limits their accessibility in developing countries where the burden of disease remains highest. Furthermore, the distribution of serotypes causing disease varies geographically and includes more serotypes than are currently covered in a single PCV formulation. Researchers have long been exploring the potential of genetically conserved non-capsular pneumococcal antigens as vaccine candidates that might overcome such limitations. To better evaluate the rationale of such approaches, an understanding of the mechanisms of immunity to the various phases of pneumococcal infection is of paramount importance. Herein we will review the evolving understanding of both vaccine-induced and naturally acquired immunity to pneumococcal colonization and infection and discuss how this informs current approaches using serotype-independent pneumococcal vaccine candidates. We will then review the alternative vaccine candidates that have been or are currently under evaluation in clinical trials.

Pneumococcal conjugate vaccine failure in children: A systematic review of the literature

BACKGROUND

Pneumococcal conjugate vaccines (PCVs) are highly effective in preventing pneumococcal invasive disease (IPD) due to serotypes included in the vaccines. The risk of vaccine-type IPD in immunised children (i.e. vaccine failure) has not been systematically assessed in countries with established PCV programmes.

METHODS

We undertook a systematic review of the English literature published from January 2000 to April 2016 to evaluate the vaccine schedule, risk factors, serotype distribution, clinical presentation and outcomes of vaccine failure in children vaccinated with the 7-valent (PCV7), 10-valent (PCV10), and 13-valent (PCV13) vaccines. Data sources included MEDLINE, EMBASE, Cochrane library, and references within identified articles.

RESULTS

We identified 1742 potential studies and included 20 publications involving 7584 participants in children aged ⩽5year-olds: 5202 received 2 doses followed by a booster in 10 studies, (68.6%), 64 (0.8%) received 3 doses without a booster in 2 studies, and 2318 received a 3+1 schedule (30.6%) in 8 studies. A total of 159 vaccine failure cases were identified, representing 2.1% [95% CI: 1.8-2.4%] of the reported IPD cases. Most studies did not report clinical characteristics or outcomes. Among eight studies reporting comorbidities, 33/77 patients (42.9%) had an underlying condition. The main serotypes associated with vaccine failure were 19F (51/128 cases with known serotype; 39.8%), 6B (33/128; 25.8%), and 4 (10/128; 7.8%). Only five studies reported patient outcomes, with a crude case fatality rate of 2.4% (2/85; 95%CI: 0.3-8.5%).

CONCLUSION

Pneumococcal conjugate vaccines have been implemented in national immunisation programmes for more than a decade, yet there are only a few studies reporting vaccine failure. PCV failure is rare, irrespective of vaccine or schedule. Co-morbidity prevalence was high amongst vaccine failure cases but case fatality rate was relatively low. There is a need for more systematic reporting vaccine failure cases in countries with established pneumococcal vaccination programmes.

Exome Sequencing Reveals Primary Immunodeficiencies in Children with Community-Acquired Pseudomonas aeruginosa Sepsis

One out of three pediatric sepsis deaths in high income countries occur in previously healthy children. Primary immunodeficiencies (PIDs) have been postulated to underlie fulminant sepsis, but this concept remains to be confirmed in clinical practice. Pseudomonas aeruginosa (P. aeruginosa) is a common bacterium mostly associated with health care-related infections in immunocompromised individuals. However, in rare cases, it can cause sepsis in previously healthy children. We used exome sequencing and bioinformatic analysis to systematically search for genetic factors underpinning severe P. aeruginosa infection in the pediatric population. We collected blood samples from 11 previously healthy children, with no family history of immunodeficiency, who presented with severe sepsis due to community-acquired P. aeruginosa bacteremia. Genomic DNA was extracted from blood or tissue samples obtained intravitam or postmortem. We obtained high-coverage exome sequencing data and searched for rare loss-of-function variants. After rigorous filtrations, 12 potentially causal variants were identified. Two out of eight (25%) fatal cases were found to carry novel pathogenic variants in PID genes, including BTK and DNMT3B. This study demonstrates that exome sequencing allows to identify rare, deleterious human genetic variants responsible for fulminant sepsis in apparently healthy children. Diagnosing PIDs in such patients is of high relevance to survivors and affected families. We propose that unusually severe and fatal sepsis cases in previously healthy children should be considered for exome/genome sequencing to search for underlying PIDs.