Pneumonia caused by Adenovirus is a significant cause of pediatric respiratory illness, characterized by its potential for severe morbidity and the challenge it presents to effective clinical management (1). This condition is particularly concerning in children, as their developing immune systems render them more susceptible to respiratory pathogens, often leading to severe sequelae (2). Adenovirus, a non—enveloped double—stranded DNA virus, is well—known for its ability to persist in the environment and within host cells (3). This property contributes to the frequent outbreaks of respiratory illness among young populations globally.

Despite notable advancements in antiviral therapies and supportive care in recent years, accurately predicting the severity and prognosis of adenovirus pneumonia in children remains a formidable challenge (4). This is primarily because current diagnostic protocols for adenovirus pneumonia predominantly rely on clinical evaluations and nucleic acid—based tests, such as quantitative polymerase chain reaction (qPCR), to confirm the presence of the virus (5). However, these methods are limited in that they do not provide comprehensive information regarding disease severity or prognosis (5).

In the pursuit of more effective clinical management, the exploration of biomarkers as tools for clinical assessment has gained significant traction in recent years (6). Biomarkers have the potential to bridge the gap between viral identification and clinical outcomes, offering valuable insights into disease outcomes and patient prognosis. Among the numerous biomarkers investigated, serum heparin—binding protein (HBP), tumor necrosis factor—alpha (TNF—α), interleukin—6 (IL—6), platelet count (PLT), and C—reactive protein (CRP) have emerged as promising candidates. Their roles in the inflammatory cascade and immune response suggest they could be closely associated with the severity and prognosis of adenovirus pneumonia in children (7).

HBP is recognized for its crucial role in modulating vascular permeability and enhancing the inflammatory response. As such, it serves as a reliable marker of acute inflammation, potentially correlating with disease severity. Elevated HBP levels have been consistently associated with worse clinical outcomes in various inflammatory and infectious diseases, highlighting its potential value in the evaluation of pediatric adenovirus pneumonia (8). For instance, in a study by Xiao-Yan Liu et al., it was demonstrated that Compared with the non-severe adenovirus pneumonia group, the severe adenovirus pneumonia group had a significantly higher serum level of HBP (9). Similarly, TNF-α and IL-6 were pivotal cytokines that mediate immune responses and inflammation (10). Their upregulation was well-documented in severe respiratory infections, where they contribute to the recruitment and activation of immune cells, perpetuating the inflammatory milieu and exacerbating tissue damage (11). Research by Yue Hou et al. showed that elevated levels of TNF—α and IL—6 could be helpful to judge the severity of adenovirus pneumonia, which could be used as the objective indexes to evaluate the prognosis of children with severe adenovirus pneumonia (12).

Alongside cytokines, CRP, an acute-phase protein produced by the liver in response to inflammation, offers a practical measure of systemic inflammation (13). Its levels rise in proportion to the intensity of the inflammatory response and were often correlated with disease severity across a spectrum of infectious conditions (14). PLT, though traditionally considered a component of routine hematological evaluations, has gained recognition for its association with infectious disease outcomes (9). Thrombocytopenia in the context of infection was frequently indicative of disease severity, possibly reflecting increased platelet consumption due to inflammation or dissemination intravascular coagulation (15).

The objective of this study was to comprehensively evaluate the combined prognostic value of serum HBP, TNF—α, IL—6, PLT, and CRP in pediatric adenovirus pneumonia. By doing so, we aimed to provide a more accurate and effective means of predicting disease severity and prognosis, ultimately guiding more targeted and personalized clinical management strategies.

The distinctive elevation of serum HBP, TNF-α, IL-6, and CRP levels in children with severe adenovirus pneumonia as well as those with poor prognosis underscored the central role of inflammatory pathways in the pathogenesis and prognosis of this infection. HBP, known for its ability to increase vascular permeability and contribute to the inflammatory response, emerges as a significant marker of acute inflammation and ensuing tissue injury in viral pneumonia (12, 20). Its notable elevation in severe children likely reflected an amplified systemic inflammatory response, correlating with disease severity and supporting its use as a prognostic biomarker (21).

The roles of TNF-α and IL-6 were likewise critical. These cytokines were cornerstone mediators in the inflammatory cascade, pivotal in the recruitment of immune cells and the propagation of inflammation (22). Their marked increase in severe children indicates a heightened inflammatory milieu, echoing previous research linking these cytokines to poor outcomes in various respiratory infections (23). TNF-α's influence on the immune response may exacerbate lung tissue damage, while IL-6 could potentially drive systemic inflammatory responses and acute-phase reactions, further compounding disease severity (24). Elevated HBP may promote the infiltration of inflammatory cells by enhancing vascular permeability, while the synergistic increase of TNF-α and IL-6 amplifies the local immune response. This “inflammatory storm” is directly related to lung tissue damage in critically ill children (25).

TNF—α and IL—6 play crucial roles in the crosstalk between the immune and coagulation systems. TNF—α can upregulate the expression of tissue factor (TF) on endothelial cells and monocytes. TF initiates the extrinsic coagulation pathway, leading to an increase in thrombin generation (26). This activation of the coagulation cascade can result in micro—thrombosis within the pulmonary vasculature, which further impairs gas exchange and contributes to lung injury (27). In addition, TNF—α can downregulate the expression of thrombomodulin, a protein that normally inhibits coagulation by activating protein C. This dual effect of TNF—α on promoting coagulation and inhibiting its regulation can lead to a pro—thrombotic state in severe adenovirus pneumonia (28).

CRP, an acute-phase protein, also significantly rises in response to inflammation. Its higher levels in severe children and those with poor prognosis pointed to its utility as a marker of systemic inflammation (29). Elevated CRP levels correlate with increased lung damage and systemic involvement, reflecting a robust host immune response (30). The synergy among these biomarkers highlights the overlapping and reinforcing pathways in the inflammatory response, which collectively may drive the outcomes to severe disease (31). A study by Haiqin Zhong found that in severe adenovirus pneumonia, the levels of CRP in children with severe adenovirus pneumonia were significantly higher than those in the mild adenovirus pneumonia group (32).

In this context, PLT revealed an inverse relationship with disease severity and prognosis (33). Thrombocytopenia in severe children may reflect platelet consumption and destruction within the inflammatory environment, associated with cytokine storms and disseminated intravascular coagulation (DIC) often seen in severe infections (34). The decrease in PLT among severe and poorer prognosis groups suggests not just its role as a passive biomarker but also as an active participant in the pathophysiological landscape of adenovirus pneumonia, with thrombocytopenia potentially serving as both a marker and mediator of severity.

The decrease in PLT was not only a consequence of consumption but also due to the direct and indirect effects of cytokines. As mentioned earlier, TNF—α and IL—6 can lead to a pro—thrombotic state, causing platelets to be trapped in micro—thrombi. Additionally, these cytokines can induce apoptosis in platelets. A study by Hantrakool et al. (35) demonstrated that TNF-α and IL-6 promote thrombosis by enhancing inflammation, endothelial dysfunction, platelet activation, and coagulation pathways. Furthermore, adenovirus infection may directly inhibit bone marrow hematopoiesis, leading to reduced platelet production and exacerbating thrombocytopenia (36). This direct suppression of hematopoietic stem cells by adenovirus has been observed in several viral infections and can significantly impact blood cell counts, including platelets (37). Moreover, adenovirus infection can trigger the production of autoantibodies that target platelet surface antigens, resulting in immune-mediated thrombocytopenia (38). The complex interplay among these biomarkers highlights the intricacy of immune and coagulation pathways underlying disease outcomes (39). The mediating role of cytokines like TNF-α and IL-6 in coagulation, fibrinolysis, and platelet function exemplifies the interconnectedness of immune responses and hemostasis in critical illness (40). This interrelation likely contributes to the observed distinct biomarker profiles between severity groups, emphasizing the multi-faceted nature of adenovirus pneumonia in children (19).

Our findings further underlined the age-related susceptibility in severe and poorer prognosis cases. Younger age groups, which showed higher prevalence in these categories, could reflect developmental differences in immune response, such as immature innate and adaptive immune functions, potentially impacting cytokine production and inflammatory responses (41, 42). This observation dovetailed with existing literature that associates younger age with poorer outcomes in respiratory infections.

Interestingly, while some traditional markers like WBC counts and other hematological parameters did not differentiate significantly between severity groups, the combination of HBP, TNF-α, IL-6, PLT, and CRP provided superior predictive accuracy. This supports the notion that pivotal insights lie within specific pathways rather than broad hematological shifts, pointing toward tailored biomarker panels for more refined clinical assessments (43).

Our composite prognostic model, achieving a high AUC for predictive accuracy, reinforced the clinical applicability of utilizing a multi-biomarker approach. This model had potential not only for stratifying risk but also for monitoring treatment response and guiding therapeutic interventions. Such approaches could refine patient management strategies, enabling targeted therapies for those at heightened risk and potentially improving outcomes through tailored interventions.

While our study provided valuable insights into the prognostic utility of combining serum HBP, TNF-α, IL-6, PLT, and CRP levels in children with adenovirus pneumonia, there were several limitations to consider. Our study sample size was relatively small and drawn from a single clinical center, which may limit the generalizability of the findings across broader populations. The study's cross—sectional nature prevented establishing causality between biomarker levels and disease outcomes. We can only observe associations at a single time point. The lack of longitudinal data may also restrict understanding of how these markers fluctuate throughout the disease course and post—recovery. Without following the patients over time, we cannot fully appreciate the dynamic nature of biomarker changes, which may be crucial for understanding the disease outcomes and recovery processes. Future research should address these limitations by incorporating larger, multi—center cohorts and longitudinal designs to validate and extend our findings. Furthermore, the combined use of multiple biomarkers may pose an economic burden on families due to the increased costs associated with additional testing and monitoring, which could limit the practical applicability of this approach in resource-limited settings. Future studies should explore ways to mitigate the economic impact on families while maintaining diagnostic accuracy.

In conclusion, this study demonstrated the relevant clinical value of combining serum HBP, TNF-α, IL-6, PLT, and CRP levels in the assessment and management of pediatric adenovirus pneumonia. To further enhance the diagnostic and evaluative value of our findings, we propose integrating multiple biomarkers into a comprehensive scoring system. The synergistic effects of HBP, TNF-α, IL-6, PLT, and CRP provide a more nuanced understanding of disease severity and outcomes compared to single markers alone. For instance, elevated levels of HBP and CRP in conjunction with increased TNF-α and IL-6 can serve as early indicators of severe disease, while thrombocytopenia may signal impending complications such as DIC. This multi-biomarker approach not only improves diagnostic accuracy but also facilitates timely intervention by identifying high-risk patients who may benefit from more aggressive treatment strategies. Moreover, the dynamic monitoring of these biomarkers over time could offer valuable insights into the disease course and response to therapy, enabling personalized and adaptive management plans for pediatric adenovirus pneumonia.