Clinical significance of circulating immune complexes and components of the blood complement system in viral meningitis in children

Background. Neuroinfections are one of the global medical and social problems of pediatrics, due to the high incidence of neurological complications that affect the further development of the child.

Objective. To establish the clinical significance of the concentration of circulating immune complexes (CIC) and C3a, C4, C1inh components of the blood complement system in viral meningitis (VM) in children.

Materials and methods. The study was conducted in 115 patients with CM of various etiologies (enteroviral – 40, arbovirus – 39, mumps – 36) children aged 2 to 14 years. Of these, in 78 (68%) CM proceeded in a moderate form. The etiology of meningitis was determined by PCR-reaction and/or ELISA of cerebrospinal fluid (CSF) and/or blood. As the main target laboratory parameters, the concentration of complement components: C1inh, C4, C3a in blood plasma was determined by ELISA using the kits of reagents «ELISA-Clinh», «ELISA-C4», «ELISA-C3a». The determination of CEC in blood serum was carried out in the immunoprecipitation reaction using 3% and 4% concentrations of polyethylene glycol (PEG) – 6000.

Results. The acute period of severe forms of CM is characterized by an increase in the total amount of CIC up to 14.7 ± 1.2 U/ml, C3a up to 348.7 ± 65.4, C4 up to 319.9 ± 56.4, C1inh up to 405.2 ± 52 .9 μg/ml. With moderate CM, the total CEC pool was 7.3 ± 0.45 IU/ml (p < 0.05), and there were no statistically significant differences in terms of complement fractions. In the period of convalescence of severe forms of CM, the total amount of CIC decreased to 8.1 ± 0.8 U/ml, C3a to 319.3, C4 up to 289.6, C1inh up to 354.6 μg/ml. In moderate CM, CIC decreased to 5.1 ± 0.56 U/ml, C3a increased to 302.5 ± 96.8, C1inh to 434.4 ± 76.5 μg/ml, and C4 decreased to 272.3 ± 42.1 μg/ml compared with the acute period (p > 0.5), remaining higher than the control group, regardless of the severity of the disease. In patients with a protracted course of CM, the C1inh index was 478.2 ± 84.9 μg/ml, C3a was 229.7 ± 44.6 ng/ml, which is 5 and 1.1 times higher, and C4 was 231.5 ± 28.9 μg/ml, 1.1 times lower than in the control group. The concentration of the C1inh fraction of the complement system – 478.2 ± 84.9 μg/ml and CIC – 2.7 ± 0.5 U/ml had a direct correlation with the protracted course of CM (r = 0.685; p = 0.0456)

Conclusion. According to the results of the study, an increase in the concentration of CEC and fractions of the complement system C3a, C4, C1inh in the blood was established, depending on the severity, period, course of the disease, indicating their participation in the development and maintenance of the inflammatory process in patients with CM. There was no normalization of the CIC and complement system parameters during the period of convalescence, and their imbalance during this period may indicate ongoing changes in the tissues of the focus of the inflammatory process and the effectiveness of the therapy.

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