Characteristics of immune and inflammatory responses among different age groups of pediatric patients with COVID-19 in China

Comparison of clinical characteristics and disease burden of febrile seizures in children with and without COVID-19

BACKGROUND

Febrile seizures (FS) are the most common seizure disorder in children and a common neurologic complication in children with coronavirus disease 2019 (COVID-19). This study aimed to identify differences in clinical characteristics and disease burden between FS with and without COVID-19.

MATERIALS AND METHODS

We conducted a retrospective analysis of medical data at our hospital from December 2019 to July 2023, focusing on hospitalized patients under the age of 14 diagnosed with FS who underwent COVID-19 polymerase chain reaction (PCR) testing. Descriptive statistics and analysis of variance were employed to compare the COVID-19 and non-COVID-19 groups in terms of clinical characteristics and disease burden.

RESULTS

A total of 514 patients were included, with 106 testing positive for COVID-19 and 408 testing negative. Patients with COVID-19 were older (34.87 ± 6.16 vs. 28.61 ± 11.35 months, P < 0.001) and had a higher proportion of males (79.2% vs. 62.3%, P = 0.001). The COVID-19 group had longer seizure durations (4.57 ± 4.38 vs. 3.22 ± 2.91 min, P = 0.006) and more complex FS (25.5% vs. 15.9%, P = 0.022). Laboratory tests showed lower lymphocyte counts in the COVID-19 group (1.87 ± 1.48 vs. 2.75 ± 1.51 × 103/µL, P < 0.001) and higher creatine kinase levels (158.49 ± 82.89 vs. 110.89 ± 56.11 U/L, P < 0.001). No significant differences were found in hospital costs, length of hospitalization, and intensive care unit admissions.

CONCLUSION

Clinicians should be knowledgeable about the distinct clinical characteristics of FS in children with COVID-19. Despite distinct features, the prognosis remains favorable and does not require excessive intervention. Ongoing monitoring and research are needed to fully understand the impact of COVID-19 on FS and optimize management strategies.

Epidemiology and clinical features of SARS-CoV-2 infection in children and adolescents in the pre-Omicron era: A global systematic review and meta-analysis

Methods

We searched MEDLINE, Embase, Global Health, CINAHL, China National Knowledge Infrastructure, Wanfang, CQvip, and the World Health Organization (WHO) COVID-19 global literature databases for primary studies recruiting children aged ≤18 years with a diagnosis of SARS-CoV-2 infection confirmed either by molecular or antigen tests. We used the Joanna Briggs Institute critical appraisal tools to appraise the study quality and conducted meta-analyses using the random effects model for all outcomes except for race/ethnicity as risk factors of SARS-CoV-2 infection.

Results

We included 237 studies, each reporting at least one of the study outcomes. Based on data from 117 studies, the pooled SARS-CoV-2 positivity rate was 9.30% (95% confidence interval (CI) = 7.15-11.73). Having a comorbidity was identified as a risk factor for SARS-CoV-2 infection (risk ratio (RR) = 1.33; 95% CI = 1.04-1.71) based on data from 49 studies. Most cases in this review presented with mild disease (n = 50; 52.47% (95% CI = 44.03-60.84)). However, 20.70% of paediatric SARS-CoV-2 infections were hospitalised (67 studies), 7.19% required oxygen support (57 studies), 4.26% required intensive care (93 studies), and 2.92% required assisted ventilation (63 studies). The case fatality ratio (n = 119) was 0.87% (95% CI = 0.54-1.28), which included in-hospital and out-of-hospital deaths.

Conclusions

Our data showed that children were at risk for SARS-CoV-2 infections and severe outcomes in the pre-Omicron era. These findings underscore the need for effective vaccination strategies for the paediatric population to protect against the acute and long-term sequelae of COVID-19.

Registration

PROSPERO: CRD42022327680.

SARS-CoV-2 immunity in animal models

The COVID-19 pandemic, which was caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a worldwide health crisis due to its transmissibility. SARS-CoV-2 infection results in severe respiratory illness and can lead to significant complications in affected individuals. These complications encompass symptoms such as coughing, respiratory distress, fever, infectious shock, acute respiratory distress syndrome (ARDS), and even multiple-organ failure. Animal models serve as crucial tools for investigating pathogenic mechanisms, immune responses, immune escape mechanisms, antiviral drug development, and vaccines against SARS-CoV-2. Currently, various animal models for SARS-CoV-2 infection, such as nonhuman primates (NHPs), ferrets, hamsters, and many different mouse models, have been developed. Each model possesses distinctive features and applications. In this review, we elucidate the immune response elicited by SARS-CoV-2 infection in patients and provide an overview of the characteristics of various animal models mainly used for SARS-CoV-2 infection, as well as the corresponding immune responses and applications of these models. A comparative analysis of transcriptomic alterations in the lungs from different animal models revealed that the K18-hACE2 and mouse-adapted virus mouse models exhibited the highest similarity with the deceased COVID-19 patients. Finally, we highlighted the current gaps in related research between animal model studies and clinical investigations, underscoring lingering scientific questions that demand further clarification.

Exploring the Immune Response against RSV and SARS-CoV-2 Infection in Children

Viral respiratory tract infections are a significant public health concern, particularly in children. RSV is a prominent cause of lower respiratory tract infections among infants, whereas SARS-CoV-2 has caused a global pandemic with lower overall severity in children than in adults. In this review, we aimed to compare the innate and adaptive immune responses induced by RSV and SARS-CoV-2 to better understand differences in the pathogenesis of infection. Some studies have demonstrated that children present a more robust immune response against SARS-CoV-2 than adults; however, this response is dissimilar to that of RSV. Each virus has a distinctive mechanism to escape the immune response. Understanding the mechanisms underlying these differences is crucial for developing effective treatments and improving the management of pediatric respiratory infections.

Complement and COVID-19: Three years on, what we know, what we don't know, and what we ought to know

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus was identified in China in 2019 as the causative agent of COVID-19, and quickly spread throughout the world, causing over 7 million deaths, of which 2 million occurred prior to the introduction of the first vaccine. In the following discussion, while recognising that complement is just one of many players in COVID-19, we focus on the relationship between complement and COVID-19 disease, with limited digression into directly-related areas such as the relationship between complement, kinin release, and coagulation. Prior to the 2019 COVID-19 outbreak, an important role for complement in coronavirus diseases had been established. Subsequently, multiple investigations of patients with COVID-19 confirmed that complement dysregulation is likely to be a major driver of disease pathology, in some, if not all, patients. These data fuelled evaluation of many complement-directed therapeutic agents in small patient cohorts, with claims of significant beneficial effect. As yet, these early results have not been reflected in larger clinical trials, posing questions such as who to treat, appropriate time to treat, duration of treatment, and optimal target for treatment. While significant control of the pandemic has been achieved through a global scientific and medical effort to comprehend the etiology of the disease, through extensive SARS-CoV-2 testing and quarantine measures, through vaccine development, and through improved therapy, possibly aided by attenuation of the dominant strains, it is not yet over. In this review, we summarise complement-relevant literature, emphasise its main conclusions, and formulate a hypothesis for complement involvement in COVID-19. Based on this we make suggestions as to how any future outbreak might be better managed in order to minimise impact on patients.

T Lymphocyte Subset Counts and Interferon-Gamma Production in Adults and Children with COVID-19: A Narrative Review

Adults and children exhibit a broad range of clinical outcomes from SARS-CoV-2 infection, with minimal to mild symptoms, especially in the pediatric age. However, some children present with a severe hyperinflammatory post-infectious complication named multisystem inflammatory syndrome in children (MIS-C), mainly affecting previously healthy subjects. Understanding these differences is still an ongoing challenge, that can lead to new therapeutic strategies and avoid unfavorable outcomes. In this review, we discuss the different roles of T lymphocyte subsets and interferon-γ (IFN-γ) in the immune responses of adults and children. Lymphopenia can influence these responses and represent a good predictor for the outcome, as reported by most authors. The increased IFN-γ response exhibited by children could be the starting point for the activation of a broad response that leads to MIS-C, with a significantly higher risk than in adults, although a single IFN signature has not been identified. Multicenter studies with large cohorts in both age groups are still needed to study SARS-CoV-2 pathogenesis with new tools and to understand how is possible to better modulate immune responses.

Impact of Cesarean Delivery and Breastfeeding on Secretory Immunoglobulin A in the Infant Gut Is Mediated by Gut Microbiota and Metabolites

How gut immunity in early life is shaped by birth in relation to delivery mode, intrapartum antibiotic prophylaxis (IAP) and labor remains undetermined. We aimed to address this gap with a study of secretory Immunoglobulin A (SIgA) in the infant gut that also tested SIgA-stimulating pathways mediated by gut microbiota and metabolites. Among 1017 Canadian full-term infants, gut microbiota of fecal samples collected at 3 and 12 months were profiled using 16S rRNA sequencing; C. difficile was quantified by qPCR; fecal metabolites and SIgA levels were measured by NMR and SIgA enzyme-linked immunosorbent assay, respectively. We assessed the putative causal relationships from birth events to gut microbiota and metabolites, and ultimately to SIgA, in statistical sequential mediation models, adjusted for maternal gravida status in 551 infants. As birth mode influences the ability to breastfeed, the statistical mediating role of breastfeeding status and milk metabolites was also evaluated. Relative to vaginal birth without maternal IAP, cesarean section (CS) after labor was associated with reduced infant gut SIgA levels at 3 months (6.27 vs. 4.85 mg/g feces, p < 0.05); this association was sequentially mediated through gut microbiota and metabolites of microbial or milk origin. Mediating gut microbiota included Enterobacteriaceae, C. difficile, and Streptococcus. The milk or microbial metabolites in CS-SIgA mediating pathways were galactose, fucose, GABA, choline, lactate, pyruvate and 1,2-propanediol. This cohort study documented the impact of birth on infant gut mucosal SIgA. It is the first to characterize gut microbe-metabolite mediated pathways for early-life SIgA maturation, pathways that require experimental verification.

Clinical and Laboratory Characteristics of Pediatric COVID-19 Population—A Bibliometric Analysis

The literature on the COVID-19 landscape has rapidly expanded in the pandemic period. The current study undertakes a bibliometric analysis of research in the topic of the clinical and laboratory characteristics of pediatric COVID-19 cases. Our aim is to perform a comprehensive bibliometric review of current research trends and patterns of this research domain. Publications retrieved from the Web of Science Core Collection and VOSviewer were used for analysis and network visualization. We analyzed geographical distribution and temporal trends, collaboration and citation patterns of authors, institutions, and countries, and core research themes from co-occurrence of keywords and terms. The analysis showed that contributions in the research field were from 302 publications, 1104 institutions, 62 countries, and 172 journals. Many publications were authored by American and Chinese authors, and many were published in the Pediatric Infectious Disease Journal, Pediatric Pulmonology, and Frontiers in Pediatrics. The top cited and co-cited journals were the New England Journal of Medicine, Nature, JAMA, Lancet Infectious Diseases, and BMJ. The network visualization maps of keywords and terms offered a global overview of the clinical and laboratory characteristics of pediatric COVID-19 patients. The bibliometric profile of the researched domain, based on analyzing a large collection of publications/data, could (i) enrich the researchers and non-researchers understanding of the field existing patterns and trends, and (ii) be useful in clinical practice (diagnostic and management) and public health policy.

Animal models for COVID-19: advances, gaps and perspectives

COVID-19, caused by SARS-CoV-2, is the most consequential pandemic of this century. Since the outbreak in late 2019, animal models have been playing crucial roles in aiding the rapid development of vaccines/drugs for prevention and therapy, as well as understanding the pathogenesis of SARS-CoV-2 infection and immune responses of hosts. However, the current animal models have some deficits and there is an urgent need for novel models to evaluate the virulence of variants of concerns (VOC), antibody-dependent enhancement (ADE), and various comorbidities of COVID-19. This review summarizes the clinical features of COVID-19 in different populations, and the characteristics of the major animal models of SARS-CoV-2, including those naturally susceptible animals, such as non-human primates, Syrian hamster, ferret, minks, poultry, livestock, and mouse models sensitized by genetically modified, AAV/adenoviral transduced, mouse-adapted strain of SARS-CoV-2, and by engraftment of human tissues or cells. Since understanding the host receptors and proteases is essential for designing advanced genetically modified animal models, successful studies on receptors and proteases are also reviewed. Several improved alternatives for future mouse models are proposed, including the reselection of alternative receptor genes or multiple gene combinations, the use of transgenic or knock-in method, and different strains for establishing the next generation of genetically modified mice.

Why Does the Severity of COVID-19 Differ With Age?: Understanding the Mechanisms Underlying the Age Gradient in Outcome Following SARS-CoV-2 Infection

Although there are many hypotheses for the age-related difference in the severity of COVID-19, differences in innate, adaptive and heterologous immunity, together with differences in endothelial and clotting function, are the most likely mechanisms underlying the marked age gradient. Children have a faster and stronger innate immune response to SARS-CoV-2, especially in the nasal mucosa, which rapidly controls the virus. In contrast, adults can have an overactive, dysregulated and less effective innate response that leads to uncontrolled pro-inflammatory cytokine production and tissue injury. More recent exposure to other viruses and routine vaccines in children might be associated with protective cross-reactive antibodies and T cells against SARS-CoV-2. There is less evidence to support other mechanisms that have been proposed to explain the age-related difference in outcome following SARS-CoV-2 infection, including pre-existing immunity from exposure to common circulating coronaviruses, differences in the distribution and expression of the entry receptors ACE2 and TMPRSS2, and difference in viral load.