Role of Intravenous immunoglobulin in Non-Immunocompromised children With Severe Adenovirus Pneumonia: A Retrospective Observational Study


 Background: Adenovirus pneumonia is a pulmonary infectious disease commonly occurring in children, and severe cases can lead to death and sequelae. Here, we aimed to observe the therapeutic timing and dosage of intravenous immunoglobulin(IVIg) in non-immunocompromised children with severe adenovirus pneumonia.Methods: This retrospective observational study investigated severe adenovirus pneumonia treated with IVIg in non-immunocompromised pediatric patients at a tertiary hospital in 2019. Participants were classified as early presenters (5-10 days of illness course) and later presenters (11-15 days) according to the timing of IVIg treatment. Patients’ clinical data were then analyzed in terms of different dosages of IVIg administration. Results: Among 202 patients enrolled, 128 were early presenters and 74 were later presenters during the study period. The later presenters had longer fever duration, more incidences of fungal coinfections, more demands for mechanical ventilation, and higher incidence of bronchiectasis than early presenters (P<0.05). For early presenters, no statistically significant differences in demands for advanced life support, outcomes and sequelae were observed between the two different dosage groups (P>0.05). For later presenters, shorter fever duration and lower usage of extracorporeal membrane oxygenation (ECMO) were observed in the high-dosage group than that in the low-dosage group (P<0.05). The incidence of post-infectious bronchiolitis obliterans (PIBO) and bronchiectasis was not significantly different between the two groups (P>0.05). The incidence of adverse events was 6.62% during IVIg infusion, showing no significant difference between the two groups (P>0.05).Conclusions: Early medical care and treatment with IVIg are very important to improve the prognosis of non-immunocompromised children with severe adenovirus pneumonia. For later presenters, children with severe conditions may benefit from a high IVIg dosage.

Adenovirus respiratory tract infections have been known to be usually mild and self-limiting in a nonimmunocompromised host; however, previous studies have described fatal cases of severe adenovirus pneumonia caused by particular serotypes, even in non-immunocompromised patients [3,4]. About 70 adenovirus serotypes are divided into seven subgroups or species (A through G), and pneumonia is usually caused by HAdV-3, 7, and 21, with HAdV-7 being associated with serious respiratory illness in infants and young children [5,6]. A 14-60% risk of developing long-term respiratory aftereffects such as post-infectious bronchiolitis obliterans (PIBO) and bronchiectasis was observed in severe adenovirus pneumonia [7].
Currently, no speci c therapy has demonstrated e cacy in the treatment of adenovirus pneumonia [1]. Several studies have shown that cidofovir (CDV) has the greatest in vitro activity against adenovirus among currently available antiviral agents and is the preferred therapeutic agent [8]. However, adverse effects of CDV include nephrotoxicity, myelosuppression, and uveitis, which limit its application in healthy children [1]. Currently, CDV is only used intravenously in many pediatric transplant clinics for the treatment of adenovirus infections [9]. Data on the response to CDV are limited in non-immunocompromised children. Therefore, intravenous immunoglobulin (IVIg) as an adjuvant therapy for severe adenovirus pneumonia has received increasing attention from clinicians. Several reports have recently re-emphasized the potential use of antibodies in the form of IVIg as an anti-infectious agent in severe adenovirus infections [10,11]. Exposure of such donors to their unique environment increased the IVIg dosage, consisting a diverse repertoire of immunoglobulin molecules that possess a wide spectrum of antibacterial and antiviral speci cities [12][13][14]. However, consensus on indications, timing, and dosage of IVIg among clinicians is limited in children with severe adenovirus pneumonia.
Accordingly, we primarily evaluated the timing of IVIg for the treatment of severe adenovirus pneumonia. Our data were analyzed in terms of the e cacy and safety of different IVIg dosages to prevent disease progression and mortality.

Study population and ethics
One thousand four hundred and ve pediatric patients with adenovirus pneumonia on admission who attended Guangzhou Women and Children's Medical Center from January 1, 2019, to January 1, 2020 were eligible for this study. The World Health Organization has published evidence-based guidelines in diagnosing pneumonia in children [15]. The evidence of adenovirus infection was identi ed by positive multiplex polymerase chain reaction (PCR) for HAdVs from nasopharyngeal swabs, sputum, and bronchial alveolar lavage uid. This study protocol was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of Guangzhou Women and Children's Medical Center of Guangzhou Medical University. All patients provided written informed consent for the use of their clinical and laboratory data from their medical reports.

Data Collection and De nitions
Inclusion criteria for the IVIg trial in the treatment of severe adenovirus pneumonia were as follows: 1) 28 days < age ≤ 18 years 2) De nition of severe cases [15]: cough or di culty in breathing, combined with at least one of the following: a) central cyanosis or oxygen saturation of < 90% on pulse oximetry; b) severe respiratory distress (e.g., grunting, very severe chest indrawing); c) signs of pneumonia with a general danger sign (inability to breastfeed or drink, lethargy or reduced level of consciousness, convulsions); and d) auscultatory ndings of decreased or bronchial breath sounds or signs of pleural effusion or empyema.
3) Treatment with IVIg administration 4) Informed consent was signed by the guardians of study participants.
Exclusion criteria for the IVIg trial in the treatment of adenovirus pneumonia were as follows: 1) Admission to pediatric intensive care unit (PICU) before IVIg administration; 2) Known or suspected active tuberculosis, severe concomitant disease (chronic pulmonary disease such as asthma, severe cardiovascular disease, neoplasia, and kidney or liver disease), and immunocompromised state (primary immunode ciency, acquired immunode ciency syndrome, and immunosuppressive medications before admission).
Clinical information of children with severe adenovirus pneumonia was collected during the study period.

Study Design
This retrospective, observational study was conducted in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. To reduce time-dependent bias, strati cation analysis was applied to patients with severe adenovirus pneumonia according to the charged time with the timing of IVIg administration. The time, measured in days since the onset of fever (temperature, ≥ 37.5 °C) was the initial symptom of adenovirus pneumonia. According to fever onset, patients were classi ed into two groups: 1) early presenters: IVIg administration in 5-10 days of illness course; and 2) later presenters: IVIg administration in 11-15 days of illness course. Clinical manifestations and outcomes were then compared between the two layers.
Next, patients from both layers were divided into two groups according to different IVIg dosages: 1) high-dosage group (1 g/kg/day for 2 days); and 2) low-dosage group (0.4-0.5 g/kg/day for 3-5 days). Demographic characteristics, laboratory ndings, image characteristics, and treatment before IVIg administration were compared between the two groups in each layer.

Statistical Analysis
Statistical analyses were performed using GraphPad Prism 8.0 (GraphPad Software Inc., San Diego, CA, USA). As data of continuous variables were skewed distribution, medians with ranges were used to express the summarized data. The nonparametric Mann-Whitney test was used for two-group analysis of continuous variables. Categorical variables were assessed using Fisher's exact test. A P-value of < 0.05 was considered statistically signi cant.

Strati ed analysis according to timing of IVIg administration
A total of 202 patients were strati ed for analysis according to the timing of IVIg administration. No signi cant difference in demographic characteristics, clinical signs and symptoms, HAdVs type distribution, immunologic assays, and treatment before IVIg administration was observed between the two layers. Remarkably, among those laboratory ndings on admission, lower hemoglobin, higher lactate dehydrogenase (LDH), and lower albumin levels were observed in later presenters. Furthermore, later presenters had higher fungal coinfection rate, more demands for mechanical ventilation, higher incidence of bronchiectasis, and longer fever duration in this study (P < 0.05) ( Table 1).

Clinical responses to different dosages of IVIg administration in each layer
With further analysis of each layer of patients, no statistically signi cant difference was observed in demographic characteristics, laboratory ndings, pulmonary complications, and treatments before IVIg administration between the two groups according to different IVIg dosages (Table 2). When we analyzed primary end-points according to different dosages of IVIg administration, no statistically signi cant differences were found in the demand for advanced life support and outcomes for early presenters; therefore, it was considered as secondary end-points (P > 0.05). For later presenters, results revealed shorter duration of fever and lower use of ECMO in high-dosage group than that in the low-dosage group (P < 0.05). However, among secondary end-points of later presenters, incidences of PIBO and bronchiectasis were not signi cantly different between the two groups (P > 0.05) ( Table 3).

Infusions and adverse events
A total of 589 infusions were administered to 202 patients: 236 for the high-dosage group and 353 for the low-dosage group. Adverse events de nitely, probably, or possibly related to the IVIg occurred during 39 of 589 infusions (6.62%).

Discussion
Adenovirus pneumonia is a pulmonary infectious disease commonly occurring in children [4,23]. Most patients have mild disease and recover from adenovirus pneumonia, but severe adenovirus pneumonia can result in considerable morbidity and mortality in immunocompetent pediatric patients [3]. HAdV-7 is known to be associated with serious pneumonia in children and is more prone to be followed by the PIBO development [24]. However, the standard therapy for the management of severe adenovirus pneumonia is not yet established to date, and e cacy data evaluating possible treatment options were not systematically studied in non-immunocompromised pediatric patients. In this retrospective study of 202 patients treated with intravenous immunoglobulin (IVIg) for severe adenovirus pneumonia at our hospital, we preliminarily assessed the potential e cacy and safety of the treatment in pediatric patients.
IVIg was used for non-immunocompromised children with severe adenovirus pneumonia when they combined serious complications [23]. The principal components of IVIg are natural antibodies (NAbs) of the IgG isotype. NAbs can enhance the recruitment of virus into lymphoid organs where they are present to T and B cells, thereby eliciting an active immune response [25]. The protective effect of IVIg against infections has been attributed to the ability of speci c antibodies to neutralize pathogens [26]. Indeed, research has found that commercial IVIg preparations possess anti-adenovirus activity in vitro, suggesting a potential role for adjuvant IVIg in adenovirus infectious diseases [14]. In this retrospective study, IVIg was administered as supplementary therapy to suppress viral replication through neutralization by viral antibodies. The strati cation analysis by illness duration according to IVIg administration showed that later presenters were more associated with lower hemoglobin and albumin levels and higher LDH levels, and more importantly, fungal coinfections were more prevalent in these patients. These results indicate that later presenters have been more complicated and serious. Based on the analysis results, early administration of IVIg was important to decrease the use of mechanical ventilation and shorten the fever duration. For the long-term outcome, early treatment was also crucial to lowering the incidence rate of bronchiectasis. In particular, early presenters had lower mortality than later presenters had, although the difference was not statistically signi cant. Therefore, the study con rmed the importance of early IVIg administration in non-immunocompromised children with severe adenovirus pneumonia.
The following step toward the therapeutic utilization of IVIg for pediatric severe adenovirus pneumonia would be the ne-tuning the dose regimen in a clinical study. In this study, patients were categorized into two groups based on their IVIg treatment regimens during each hospitalization: high-dosage group underwent IVIg treatment with 1 g/kg for 2 days, whereas low-dosage group were treated with 0.4-0.5 g/kg for 3-5 days. At high doses, IVIg inhibits the function of different arms of the immune system, including inhibition of the maturation and function of dendritic cells, attenuation of T-cell proliferation, and production of proin ammatory cytokines [26]. A previous study demonstrated that a high-dose regimen might not be appropriate for the treatment of infectious diseases. However, recent research has found that activation of the immune system and generation of numerous chemokines and cytokines could play a major role in the pathogenesis of adenovirus tissue damage [27]. In our study, no signi cant differences were observed between low-and high-dose groups in clinical end-points of early presenters. Nevertheless, for later presenters, the high-dosage group can reduce the fever duration and ECMO usage, although different dosages of IVIg administration had little impact on the prognosis of later presenters. In other words, later presenters with severe adenovirus pneumonia could bene t from a high-dose of regimen IVIg during hospitalization.
The intravenous immunoglobulin level in this study was well tolerated, and no serious adverse events were found to be attributed to IVIg. Currently, most viewpoints are that majority of adverse effects are associated with high IVIg dosage [16]. Moreover, the incidence was 6.62% during infusion with IVIg in this study. Furthermore, the IVIg dosage was not related with the incidence of adverse events in the two study groups. Thus, different dosages to guarantee the e cacy of therapy and minimize adverse effects were observed in our study.
Limitations of our study were mainly due to its retrospective le review design, with all associated disadvantages of this study type (e.g., missing information, poor documentation, etc.). However, this study is the rst to explore the timing and dosage of IVIg administration in non-immunocompromised pediatric patients with severe adenovirus pneumonia and to evaluate the correlation between different dosages and the incidence of adverse events.

Conclusions
IVIg is an adjunctive therapy for the treatment of severe adenovirus pneumonia in children. Our data a rm that early IVIg administration for severe adenovirus pneumonia in non-immunocompromised patients could be a treatment strategy worth considering. For later presenters, a high dosage of IVIg is effective in reducing the ECMO use and fever duration, which is probably bene cial in these patients.