The immunoperoxidase antibody (IPA) technique was used to develop two new tests for serodiagnosis of
respiratory syncytial virus infections: a microneutralization test based on the reduction of the number of infected cells and an IPA test for determination of virus-specific
immunoglobulin G (
IgG).
Neutralizing antibody was determined both in the presence and absence of
complement. In a group of 24 infants and young childres, ages less than 1 to 36 months, with acute
respiratory syncytial virus infection, serodiagnosis was made by the IPA-
IgG test in 20 cases, by neutralization test with addition of
complement in 19 cases, and by neutralization test without addition of
complement in 17 cases.
Complement fixation detected only 12 cases of
infection. All four cases not serologically diagnosed were infants less than 1 month old. Neutralization test antibody titers in the presence of
complement were usually 4- to 16-fold higher than titers obtained without addition of
complement. Both IPA-
IgG and neutralization test (in the presence of
complement) appear very efficient in serologically detecting
respiratory syncytial virus infections in infants older than 1 month and give rapid results (IPA-
IgG takes 2 h to complete, and the neutralization test takes 24 h). However, IPA-
IgG is simpler to perform.