Evaluation of Immunoglobulin A Enzyme Immunoassays to Detect Primary Respiratory Syncytial Virus Infection in Infants and Young Children

Abstract

Background Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory infections in children <2 years of age. Prior infection in a child is usually determined by RSV antibodies; however, in young children, persisting maternal immunoglobulin G antibodies can incorrectly indicate past RSV infection. We developed and evaluated 4 immunoglobulin A (IgA) antibody enzyme immunoassays (EIAs) with the RSV F, subgroup G (Ga or Gb proteins) or RSV lysate antigens to distinguish infection induced from persisting maternal RSV antibodies. Methods We tested the EIAs against 62 cord blood specimens (group A), 39 plasma specimens from infants not exposed to an RSV season (group B), 102 plasma specimens from infants with a documented RSV infection (group C), and 124 plasma specimens from infants exposed to their first RSV season but without a documented RSV infection (group D). Results Among the 2 negative control groups, no group A specimens and 1 of the group B specimens were positive in all 4 IgA EIAs, giving a specificity of 100% and 97%, respectively. The sensitivity of the F, Ga, Gb, and Lysate IgA EIAs were 88%, 31%, 26%, and 61%, respectively, for group C specimens. Forty-four percent of the 124 specimens in group D were positive in the RSV-F IgA EIA. Conclusions The RSV-F protein IgA EIA exhibited a high level of sensitivity and specificity for detecting previous RSV infections in the presence of maternal antibodies and can help in RSV clinical trials and epidemiologic studies in young children.