Efficacy of a Less-Sensitive Enzyme Immunoassay (3A11-LS) for Early Diagnosis of Human Immunodeficiency Virus Type 1 Infection in Infants

Abstract

We evaluated a less-sensitive enzyme immunoassay (3A11-LS) for its possible use for early diagnosis of human immunodeficiency virus type 1 (HIV-1) infection in infants. The results were compared with those from the immunoglobulin G-capture enzyme immunoassay. A total of 239 sera from 77 infants were tested. All 25 sera from the 10 infants born to seronegative mothers were found to be negative by both assays. Forty-one seroreverting infants showed a complete decay of maternal antibodies by 4 months by the 3A11-LS assay. However, the assay detected HIV antibodies in only 9 (36%) of 25 sera collected from infected infants between 4 and 6 months and in 27 (63%) of 43 sera collected after 6 months of age. Further analysis with alternative cutoff values indicated that the 3A11-LS had a sensitivity of 12 to 44% and a specificity of 90 to 100% for infants between 4-6 months of age. This data suggest that a diagnosis of HIV infection in some of the infants could be made after 4 months of age by the 3A11-LS assay, although a negative 3A11-LS test result may not rule out infection and may require a further followup.Considerable efforts have been devoted to developing and assessing new approaches for the early diagnosis of human immunodeficiency virus (HIV) infection in infants (1,6,7,12,14,17). Although it is generally agreed that molecular methods, such as the detection of viral RNA or proviral DNA, are the most sensitive methods for HIV type 1 (HIV-1) diagnosis in infants (7,14), these methods involve complex and expensive technologies and thus have remained largely unavailable in resource-poor settings in the developing world, where the majority of pediatric HIV infections continue to occur (3, 5). While affordable intervention strategies are now available to prevent vertical transmission (4,5,8,13,16), early diagnosis of HIV infection in exposed infants remains a major obstacle and challenge both to assessing the efficacy of these strategies and to providing early appropriate care to infected infants. Identification of a simple and inexpensive laboratory tool for early diagnosis in infants would have great implications, especially in developing countries (11).In 1998 Janssen et al. (9) described a modified, less-sensitive enzyme immunoassay (3A11-LS) which, when used in conjunction with the sensitive enzyme immunoassay (EIA), identifies recent HIV-1 infection and is useful for estimating incidence in a population. This method detects increasing antibody levels during the early phase of infection and thus is quite sensitive to various levels of HIV-1 antibodies. We postulated that this method may also be useful in diagnosing HIV infection in perinatally exposed infants who are making their own antibodies in the background of decaying maternal antibodies. Our previous work (15), using an immunoglobulin G-capture EIA (IgG-CEIA), had shown that the decay of maternal antibodies was observed over a period of 6 months and that most infected infants (Ͼ90%) developed their own HIV-specific antibodies which were detectable after...