Improved Specificity ofIn VitroAnti-HIV Antibody Production: Implications for Diagnosis and Timing of Transmission in Infants Born to HIV-Seropositive Mothers

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Abstract
In vitro anti-HIV antibody production (IVAP), initially introduced as a method for diagnosis of human immunodeficiency virus type 1 (HIV-1) infection in infants, has been limited in its application because of poor specificity and sensitivity early in life. The aims of this study were to improve the specificity of the IVAP assay and to evaluate its sensitivity in conjunction with assays of HIV culture, polymerase chain reaction (PCR), and p24 antigen. To prevent false-positive reactions resulting from maternal serum-derived cytophilic anti-HIV IgG, additional preculture and washing steps for peripheral blood mononuclear cells (PBMCs) were introduced that resulted in dramatic improvement in specificity of IVAP. The sensitivity of the revised IVAP at age <3 months in 20 infected infants was, however, only 25%; of 15 infected infants initially negative in IVAP, 13 became positive at a mean estimated age of 4.4 ± 1.8 months. When correlated with virological assays, a failure to respond in IVAP at age <1 month was often associated with negative virological identification, whereas a positive IVAP response at age <3 months was always associated with positive results in all virological assays. Moreover, conversion from negative IVAP to positive responses occurred subsequent to, and not concurrently with, a positive virological identification of infected infants. The revised IVAP methodology renders this assay potentially useful as an additional tool not only for the diagnosis of HIV infection, but for estimating timing of maternal-infant HIV transmission as well