Anticorpos IgG total, IgG1 e IgG3 anti-VRS em crianças ≤5 anos de idade: ocorrência, nível e avidez

Abstract

Respiratory syncytial virus (RSV) is well recognized as the most important pathogen accounting for acute respiratory disease (ARD) in infants and young children, mainly bronchiolitis and pneumonia. Since the 1960s, aspects of the immune response to RSV have been intensively studied, however, some characteristics that may lead a protection against the infection or severity of the illness are still unknown. This study aimed to investigate the occurrence, levels and avidity of total IgG, IgG1 and IgG3 specific to RSV by indirect enzyme linked immuno sorbent assay (ELISA) and avidity ELISA in serum samples from children ≤ 5 years old with RSV-ARD (cases) and without ARD (controls). Also a possible association between the antibody avidity and severity of the disease was examined. The occurrence and levels of RSV-IgG were age dependent, corroborating to previous observation that infants <3 months old show high prevalence and levels of maternal antibodies and the responsiveness capacity of children ≥2 years old to reinfections. The results of RSV-specific total IgG and IgG1 avidity demonstrated that cases <3 months old show low avidity antibodies when compared with age-matched controls. While children ≥2 years old with lower tract respiratory illness (LTRI) showed lower RSV-specific total IgG avidity than those with upper tract respiratory illness (UTRI). These results suggest that the high avidity of RSVspecific IgG may be related to protection against RSV disease in children <3 months old and thus, children with high avidity maternal RSV-specific IgG may have a lower probability of developing disease. They also suggest that children ≥2 years old with low avidity RSVspecific IgG showed tendency to develop severe RSV-illness.