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

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.