Clinical significance of immunoprophylaxis of respiratory syncytial viral infection in premature children at early age

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Introduction

Respiratory syncytial virus (RSV) is one of the most common pathogens in the pediatric population and is the most frequent cause of lower respiratory tract infections (LRTI) in infants [1]. Based on published epidemiological data, in 2022, 7,601 children under the age of 5 died in the Russian Federation, including 5,876 children under the age of 1. RSVI accounts for 3.5 % of deaths among children under 5 and 3.3 % of infant deaths among children under 1 [2]. Approximately 50–70 % of children at risk of RSV infection occur in the first year of life [3]. According to the literature, 30–70 % of children with respiratory disorders at birth require prolonged mechanical ventilation (MV), and approximately 20–30 % develop bronchopulmonary dysplasia (BRONCHIAL OBSTRUCTION): in children with extremely low birth weight (ELBW), the incidence of BRONCHIAL OBSTRUCTION reaches 50 % and is the leading cause of mortality [4]. Intensive resuscitation measures with strict ventilation parameters, while saving the life of a premature infant, lead to hypoxic damage to the central nervous system and cause severe damage to the respiratory system [5; 6]. Among the disorders of cellular homeostasis and angiogenesis at the extracellular matrix level in the development of respiratory disorders in children at risk, changes in the content of matrix metalloproteinases (MMP-2, MMP-9), their tissue inhibitor (TIMP-2), and vascular endothelial growth factor (VEGF-D) [3; 16].

Global experience in immunoprophylaxis of severe diseases associated with RSVI is more than 15 years old [7]. Observational studies (registries) conducted in Denmark, Germany, France, the United States, and Canada [8–12] have shown a low incidence of RSV bronchiolitis among young children from high-risk groups who received immunoprophylaxis with monoclonal antibodies targeting the F protein epitope of RSV [14]. The main mechanism of action of monoclonal antibodies is to block the fusion of the virus with respiratory tract cells and suppress viral replication. However, it is currently important to study the impact of RSVI immunoprophylaxis on bronchopulmonary morbidity and the nature of changes in pulmonary tissue remodeling markers in the long term in young children.

The aim of the study is to evaluate the clinical significance of immunoprophylaxis of RSV infection in high-risk premature infants in early childhood.

Materials and Methods

The study involved 216 children born at the regional perinatal center in Yekaterinburg (201 children in the main group and 15 in the control group). The main group (n = 201) was divided into group 1/ immunization “+” (n = 104) and group 2/immunization “–” (n = 97).

The criteria for inclusion in the main group 1 were: 1) receiving a course of immunoprophylaxis in risk groups – children born at ≤ 35 weeks of gestation, discharged from the Regional Perinatal Center during the epidemic season from October to March inclusive; children under one year of age who required treatment for BLD during the last six months before the start of the epidemic period; children under one year of age prior to surgery for hemodynamically significant congenital heart defects (CHD) and vessels – in accordance with the state program of the Sverdlovsk Region¹ (SR); 2) obtaining voluntary informed consent from legal representatives (parents).

The palivizumab treatment regimen consisted of five injections administered intramuscularly at one-month intervals at a dose of 15 mg/kg body weight (according to the instructions). The first injection was administered in the hospital 7–10 days before discharge from the second stage of neonatal care; the 2nd to 5th injections were given to the children after discharge from the hospital on an outpatient basis at the immunology center of the State Autonomous Healthcare Institution “ODKB” of Sverdlovsk Region/day hospital and/or intermunicipal centers of Sverdlovsk Region.

The main group 2 included:

1) children who have not received passive immunoprophylaxis (non-epidemic season in children from high-risk groups for severe RSV infection from April to September; unspecified thrombocytopenia); 2) refusal of legal representatives to carry out passive immunization.

The control group consisted of 15 full-term infants with health groups I and II.

At the age of 1–3 years, all children in the study were assessed for the frequency and structure of acute respiratory diseases (ARD). Biomarkers of pulmonary tissue remodeling (MMP-2, MMP-9, TIMP-2 in 77 children and VEGF-D in 92 children) were determined using solid-phase enzyme immunoassay.

An instrumental examination – echocardiography (ECG) – was performed using a PHILIPS Affiniti 50 device to determine signs of pulmonary hypertension PH. An assessment of systolic and diastolic LV function was performed, which included examination of: the size of the RV outflow tract above the PA valve (RVOT, mm), the velocity of the RV tricuspid valve trunk (PA/APULM, Vmax, m/s), and PA trunk diameter (PA/APULM, trunk, mm) to predict the outcome of cardiovascular and pulmonary diseases. The assessment was based on the reference values adopted by the American Society of Echocardiography (2020) [13].

Statistical analysis of the data was performed using Statistica Professional 10 software. Quantitative indicators were assessed using the Shapiro-Wilk test. The mean and standard deviation value – M (SD) were calculated for normally distributed data; the paired Student's t-test was used to compare two independent samples. The median – Me [Q1; Q3] – was calculated for data that deviated from normal distribution, and the Mann–Whitney test was used to compare them. Nominal data were described using absolute values and percentages, and they were compared using Pearson's chi-square 2 test. Correlation analysis was performed using Pearson's and Spearman's criteria. Statistical significance was considered for values of p < 0.05. Attributive risk (AR, %) and odds ratio (OR) with 95 % CI were calculated, as well as attributive proportion (AP %) using the formula AP = (OR-1)/OR) · 100 %, applicable for case-control studies [15].

Results and Discussion

A total of 201 young children at high risk of developing severe RSVI were monitored. During pregnancy, the mothers of the children studied were on average 25.6 (12.6) years old, with an average number of pregnancies of 2.7 (1.8) and an average number of deliveries of 1.8 (1.2). A burdened obstetric history was noted in 82.5 % (n = 166) of mothers. Complicated pregnancies were observed in 100 % of mothers (46.3 % – preeclampsia, 41.3 % – anemia, 31 % – gestational diabetes mellitus, 53 % – fetal growth restriction syndrome). More than half of the children (55.7 %, n = 112) were born by cesarean section. Gestational age ranged from 24 to 34 weeks. The mean gestational age was 27.91 (2.40) weeks; in group 1, this indicator was significantly lower than in group 2: 26.0 [24.0–30.0] and 28.0 [24.0–33.0] weeks, p < 0.001. More than half of the children had extremely low birth weight (82 %, n = 165), and 18 % (n = 36) had very low birth weight. Analysis of body weight distribution showed a significant prevalence of children weighing less than 999 g in group 1 (88.5 %) compared to group 2 (75.3%), р (2) = 0,015.

Due to the development of respiratory distress syndrome, 75 % (n = 150) of children required transfer to mechanical ventilation and admission to the NICU (neonatal intensive care unit). The average duration of mechanical ventilation was 22.5 (3.4) days. Children in group 1 were significantly more likely (83.6 %, n = 87) to be transferred to mechanical ventilation compared to group 2 (65 %, n = 63), р (2) = 0,003.

The structure of diagnoses in children was dominated by respiratory distress syndrome – 97 % (n = 195), haemodynamically significant congenital heart defect – 31% (n = 62), ischaemic-hypoxic CNS disorder – 97.4 % (n = 75), anaemia – 82 % (n = 185), retinopathy – 87.6 % (n = 176). Analysis of the structure of diagnoses in children from group 1 showed a significant predominance of severe anemia and intraventricular hemorrhages compared with the corresponding data for group 2: 98 and 85.6 %, respectively, р (2) = 0.002; 21.2 and 10.3 %, р (2) = 0.036. From the 28th day of life, bronchial obstruction was diagnosed in 67.2% (n = 135): in group 1 – 66.3 % (n = 69), in group 2 – 68 % (n = 66), р (2) = 0.799.

At the prospective stage of observation, the average age of the children observed (n = 201) was 2.4 (0.97) years. Analysis of the structure of diseases in early childhood revealed the highest incidence of residual cerebral insufficiency – 197/201/ (98) and bronchial obstruction (in children from 28 days to two years of age) – 105/201/ (52.2).

The average number of ARI cases per year in all children (n = 201) was 2.3 (0.4); in group 1, it was 1.4 (0.4) cases, which was significantly less than in group 2 (2.5 (0.5), p = 0.001). The frequency of upper respiratory tract infections among all ARI in the observation groups was 83.6 % (n = 168), lower respiratory tract infections: episodes of bronchial obstruction – 57.2 % (n = 115), pneumonia – 16 % (n = 32), and only 10.4 % (n = 21) of the children examined had no recorded cases of respiratory system diseases. In a comparative analysis, the incidence of ARI and episodes of bronchial obstruction in children in group 2 was significantly higher than in children in group 1: 90 % and 78 %, p = 0.024; 65 % and 50 %, p = 0.033. A tendency toward more frequent incidence of pneumonia was established in group 2: 21 % and 11.5 %, p = 0.079. There was a tendency toward a greater number of children without ARI in group 1: 14.4 % and 6.2 %, p = 0.057 (Table 1).

 

Table 1. Frequency of acute respiratory diseases in young children  in comparison groups, abs. (%)

Symptom (ICD-10)	Total,  n = 201	Group 1, n = 104	Group 2,  n = 97	p (c2)
ARI (J 06)	168 (83.6)	81 (78)	87 (90)	0.024
Episodes of bronchial obstruction (J 40)	115 (57.2)	52 (50)	63 (65)	0.033
Pneumonia (J 18)	32 (16)	12 (11.5)	20 (21)	0.079
Children who did not have a single case of ARD during the 1st, 2nd, and 3rd years of life	21 (10.4)	15 (14.4)	6 (6.2)	0.057

 

It has been established that the absence of RSVI immunoprophylaxis in the first year of life in premature infants increased the risk of developing episodes of bronchial obstruction at the age of 1–3 years by 1.85 times (OR = 1.85 [1.05–3.26], AP = 46 %). A trend toward an almost twofold increase in the risk of developing pneumonia at an early age (OR = 1.99 [0.91–4.30], AP = 49.7 %) was identified in children in group 2 (Table 2).

 

Table 2. The relationship between passive immunization and the incidence of acute lower respiratory tract diseases in young children

Factor	Symptom, No/total/ %		p (c2)	АР, % 95 % CI	OR 95 % CI	АP %
	Episodes of bronchial obstruction, n = 115
Passive immunization: not performed – 97 performed – 104	Group 2	Group 1	0.033	15 6.2–27.41	1.85 1.05–3.26	46
	63/97/65	52/104/50
	Pneumonia, n = 32
	20/97/20.6	12/104/11.5	0.079	9.1 1.5–29.3	1.99 0.91–4.30	49.7

 

The content of pulmonary tissue remodeling markers – MMP-2, MMP-9, TIMMP-2 – in young children (n = 77) did not differ between groups 1 (n = 44) and 2 (n = 33): MMP-2 – 276.0 and 256.0 ng/ml, respectively, p = 0.198; MMR-9 – 1090.2 (682.5) and 970.3 (550.2) ng/ml, p = 0.421; TIMMP-2 – 450.2 (57.3) and 428.5 (50.7) ng/ml, p = 0.207.

Previously, in our study [16], we assessed the relationship between MMP levels and the frequency of bronchial obstruction episodes in young children. Children with episodes of bronchial obstruction who did not receive immunoprophylaxis in their first year of life showed a significant increase in MMP-9 and a decrease in TIMMP-2 compared to the corresponding data for children in group 1 (Table 3).

 

Table 3. MMP content in blood serum in children with episodes of bronchial obstruction (J 40), abs. (%)

Symptom	M (SD)			р
	Total, n = 35	Group 1, n = 17	Group 2, n = 18
ММР 2, ng/ml	261.1 (55.9)	275.2 (56.7)	247.1 (53.3)	0.151
ММР 9, ng/ml	652.1 (461.5)	341.4 (204.0)	945.3 (421.5)	0.000
ТIММР 2, ng/ml	455.2 (52.8)	483.9 (49.5)	428.0 (40.8)	0.000

 

Correlation analysis confirmed the presence of a direct statistically significant relationship between the level of MMR-9, TIMM-2, and the frequency of bronchial obstruction episodes (rs = 0,283, р = 0,000 and r = 0,172, р = 0,000 respectively) in early childhood.

The mean VEGF-D value in the main group of children aged 1–3 years was 342.11 (127.4) pg/ml. Significantly higher VEGF-D levels were found in groups 1 and 2 compared to those in the control group: group 1 – 223.25 (107.3) and the control group – 50.2 (25.8) pg/ml, p = 0.000; group 2 – 495.94 (209.1), and control – 50.2 (25.8) pg/ml, p = 0.000. At the same time, the average VEGF-D value in children with immunization “-” was significantly higher than in children with immunization “+”: 495.94 (209.1) and 223.25 (107.3) pg/ml respectively, р = 0,000.

The VEGF-D content in children with episodes of bronchial obstruction depending on the presence of immunization revealed a significantly higher level of this marker in children without immunoprophylaxis compared to the immunization “+” group: 687.1 (425.3) и 158.5 (71.1) pg/ml respectively, р = 0,000 (Table 4).

 

Table 4. VEGF-D levels in the blood serum of children aged 1–3 years with episodes of bronchial obstruction (J 40)

Factor	M (SD)			р
	Total, n = 35, abs. (%)	Group 1, n = 17, abs. (%)	Group 2, n = 18, abs. (%)
VEGF-D, pg/ml	415.2 (327.8)	158.5 (71.1)	687.1 (425.3)	0.000

 

Correlation analysis between VEGF-D and the frequency of bronchial obstruction episodes revealed a significant positive association in young children who were at risk of developing severe RSV in their first year of life (rs = 0.408; р = 0.000).

The correlation between VEGF-D and MMP-9 levels in children in the main group was statistically significant (rs = 0.273; р = 0.000), which allows us to consider this correlation as a reflection of the intense interaction between the processes of remodeling and angiogenesis of lung tissue in prematurely born children aged 1–3 years.

Additional assessment of RV systolic function – RVOT, RV tricuspid valve annulus velocity (Vmax, m/s), and PA trunk diameter (trunk, mm) – revealed that these echocardiographic parameters were within normal limits (Table 5).

 

Table 5. Some echocardiography* parameters in children in the comparison groups

Factor ЭхоКГ	Total, n = 77, abs. (%)	Group 1,  n = 44, abs. (%)	Group 2,  n = 33, abs. (%)	p	Norm
	М (SD)
RV: RVOT, mm	15.7 (2.6)	15.8 (3.08)	15.6 (2.3)	0.798	9.0–23.0
PA (APULM), Vmax, m/s	1.13 (0.3)	1.05 (0.2)	1.26 (0.5)	0.015	0.9–3.0
PA (APULM), scapus, mm	8.6 (5.9)	12.2 (3.6)	6.3 (5.2)	0.000	12.7–23.0

Note: * – Echocardiography – echocardiographic examination; RV – right ventricle; PA – pulmonary artery; RVOT – right ventricular outflow tract; V_max – maximum blood flow velocity across the pressure gradient.

 

However, correlation analysis demonstrated a significant relationship between VEGF-D levels and PA trunk diameter (r = 0.362; р = 0.000), but this fact can be attributed, on the one hand, to the anatomical features of the circulatory organs of the children studied and, on the other hand, to the activation of angiogenesis due to hypoxic conditions in infancy.

Conclusions

1. Children at risk of severe RSV infection have a high incidence of acute respiratory infections (83.6 %) in early childhood. A significantly higher average annual number of acute respiratory infections has been observed in children who did not receive RSV immunoprophylaxis in their first year of life.
2. Immunoprophylaxis in children at risk of severe RSV disease is associated with a reduction in the incidence of bronchial obstruction (OR = 1.85 (1.05–3.26)) and pneumonia between the ages of 1 and 3 (OR = 1.99 (0.91–4.30)).
3. No differences in pulmonary tissue remodeling markers (MMR and TIMMP) were found depending on immunoprophylaxis in young children (aged 1–3 years of age), but a direct relationship was found between the frequency of episodes of bronchial obstruction and the levels of MMR-9 and TIMM-2 in blood serum.
4. The angiogenesis marker (VEGF-D) in children without immunoprophylaxis was significantly higher than in children who received immunoprophylaxis: 495.94 (209.1) and 223.25 (107.3) pg/ml, p = 0.000, and in children with episodes of bronchial obstruction without immunoprophylaxis, which may serve as a predictor of pulmonary interstitial fibrosis in this category of patient.
5. In young children born prematurely, a correlation was found between VEGF-D levels and PA trunk diameter (r = 0.362; p = 0.000) according to echocardiography data.

Thus, in the study conducted, the clinical efficacy of immunoprophylaxis against RSV in children at risk of severe RSV bronchiolitis in the first year of life consists in a significant reduction in the frequency of ARD, a decrease in the likelihood of developing episodes of bronchial obstruction and pneumonia, and a positive correlation between angiogenesis marker levels and PA parameters according to echocardiography data (at the age of 1–3 years).

 

¹ Healthcare development in the Sverdlovsk Region until 2024 (Resolution of the Government of the Sverdlovsk Region No. 1267-PP of October 21, 2013, Orders No. 1382-n of 24 December 2012, No. 514n of 10 August 2017, No. 2277-p of 9 December 2020, No. 2929-p of 18 December 2022).

About the authors

Yu. N. Ibragimova

Ural State Medical University; Regional Children's Clinical Hospital

Author for correspondence.
Email: Julia080685@gmail.com
ORCID iD: 0000-0003-4053-4405

Assistant of the Department of Hospital Pediatrics, Pediatrician

Russian Federation, Yekaterinburg; Yekaterinburg

I. V. Vakhlova

Ural State Medical University; Regional Children's Clinical Hospital

Email: Julia080685@gmail.com
ORCID iD: 0000-0002-5274-4699

DSc (Medicine), Professor, Head of the Department of Hospital Pediatrics

Russian Federation, Yekaterinburg; Yekaterinburg

Ye. V. Vlasova

Regional Children's Clinical Hospital

Email: Julia080685@gmail.com
ORCID iD: 0000-0002-6678-5360

PhD (Medicine), Head of the Department of Clinical Immunology, Allergist-Immunologist

Russian Federation, Yekaterinburg

I. M. Krivolapova

Ural State Medical University; Regional Children's Clinical Hospital

Email: Julia080685@gmail.com
ORCID iD: 0000-0001-7922-3810

PhD (Biology), Senior Laboratory Assistant of the Department of Hospital Pediatrics, Biologist of the Department of Immunology of CLD

Russian Federation, Yekaterinburg; Yekaterinburg

References

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