Assessment of pneumococcal vaccine response, memory B-cell and mannose-binding lectin levels in children with recurrent respiratory tract infetions

ABSTRACT ASSESSMENT OF PNEUMOCOCCAL VACCINE RESPONSE, MEMORY B-CELL AND MANNOSE-BINDING LECTIN LEVELS IN CHILDREN WITH RECURRENT RESPIRATORY TRACT INFETIONS Recurrent respiratory tract infections are the leading causes of morbidity and mortality in pediatric patients worldwide. In the developed countries, it affects 25% of children aged below 1 year and 18% of children aged 1 to 4 years. Specific antibody deficiency (SAD) is a transient primary B-cell immunodeficiency which should be searched in children aged ≥2 years who suffer from recurrent bacterial infections of the respiratory tract. Mannose-binding lectin (MBL) contributes to innate immunity through opsonization and complement activation. In previous reports, MBL deficiency has been associated with several infectious and autoimmune disorders. The aim of the present study was to investigate the presence of specific antibody deficiency as the cause of transient primary immunodeficiency, and MBL and memory B-cell (CD27) levels in childrens with recurrent respiratory infections. The study included a total of 50 children with recurrent respiratory infections and 50 healthy controls subjects aged 2 to 17 years. All patients in the study group and five subjects in the control group received pneumococcal vaccine. Serum pneumococcal immunoglobulin G (IgG) levels were measured before and four weeks after the vaccination. In addition, memory B-cell (CD27) levels were measured in the study group, and MBL levels were evaluated both in the study and the control groups. Pneumococcal IgG levels before the vaccination, and pneumococcal IgG, CD27, and MBL levels after the vaccination were compared with each other and between the study and control groups. A significant difference was observed in serum pneumococcal IgG levels of the study group before and after the vaccination. The difference in serum pneumococcal IgG levels of 4 of 50 patients (8%) before and after the vaccination in the study group was <1.3 mU/mL. Four patients with SAD in the study group were compared with those in the control group, and no significant difference was found in the MBL levels. The mean CD27 level was found to be %17.0±8.1, indicating a significant difference compared to the all of the patients in study group. In conclusion, further large-scale studies are required to elucidate the underlying immunodeficiency patterns in children with recurrent respiratory tract infections and contribute to our understanding of preventive and/or therapeutic interventions in this patient population. Keywords: Recurrent respiratory tract infections, specific antibody deficiency, mannose-binding lectin, memory B-cells.