IgE-based assay for early detection of HIV-1 infection in infants
Authors: Maria J Miguez-Burbano, Cecelia Hutto, Gail Shor-Posner, Gwendolyn Scott, Viola Lopez, Shenghan Lai, Hong Lai, MaryAnn Fletcher, Marianna K Baum
Journal: The Lancet (1997)

Most AIDS cases in children worldwide occur as a result of vertical transmission, but there is no simple, reliable, and inexpensive test to diagnose HIV-1 infection in neonates. We evaluated an IgE assay for diagnosis of HIV-1 in infants. We tested 190 serum samples from 78 children (36 HIV-1 infected, 42 uninfected) born to HIV-1 seropositive mothers. Infection was diagnosed by two positive HIV-1 viral cultures or a positive ELISA and Western blot after 18 months of age. We grouped the children according to their age at initial sample collection: birth to 6 months (group 1), 7–12 months (group 2), 13–24 months (group 3), and 25–60 months (group 4). The total (average) number of samples tested per child in each group was: 75 (2·6), 48 (3), 29 (2–9), and 38 (1–7) for groups 1, 2, 3, and 4, respectively. Sequential samples taken at different ages were tested in 41 children. We treated serum or plasma samples (200 μL) with the protein G affinity method twice (rProtein G affinity method, Isolab Inc, Akron, OH, USA). The HIV enzyme immunoassay kit (Coulter Immunology, Hialeah, FL, USA) plates were incubated at room temperature with pretreated serum for 30 min, aspirated and washed five times, after which time horseradish peroxidase-conjugated with antihuman IgE was added (Incstar Corp, Stillwater, MN, USA), and the mixture incubated at room temperature. Plates were reaspirated and rewashed five times. Fresh substrate solution (100 μL) was added to each well and incubated at room temperature and the reaction stopped by adding H2SO4. The plate was read with bichromathic absorbance at 492 nm with 620 nm as reference. Controls were a blank with conjugate and substrate, serum from one HIV-1 seronegative person and one HIV-1 seropositive person. A cutoff for positive and negative values was based on previously-tested adults (116 HIV seropositive, 54 HIV seronegative; unpublished data). Specific IgE sensitivity, specificity, and predictive value with 95% CI were calculated with the first sample from each infant. HIV-IgE enzyme immunoassay correctly diagnosed HIV status in 187 (98%) of the 190 serum samples tested; 35 of 36 HIV-1 infected children were identified as HIV-IgE seropositive; 41 of 42 seronegative children were correctly identified as HIV-IgE seronegative (table). The false-negative result was with samples collected during the first 35 months of life in a child who tested positive at 37 months with the IgE test. The false positive test occurred with a single sample from a 1 month-old child. We tested 26 samples in infants younger than 3 months; all samples but one were correctly assigned. Overall, sensitivity was 0·9722 and specificity 0·9762 with a positive predictive value of 0·9722 and negative predictive value of 0·9762. Individual group analyses (table) showed sensitivity, specificity, and predictive values of 93% in group 1 and 100% in groups 2, 3, and 4. In children who provided sequential samples results were consistent over time, with the exception of the false negative.TableDetection of HIV-1 specific IgE antibodyGroup (age in months)Group 1 (0–6)*Group 1 included 24 children <3 months of age when first tested; 12 children were 0–1 month and 12 children were 2–3 months of age;Group 2 (7–12)Group 3 (13–24)Group 4 (25–60)HIV (+)†On the basis of viral cultures or HIV ELISA and Western blot. (total n=36)143316HIV (−)†On the basis of viral cultures or HIV ELISA and Western blot. (total n=42)151377Correct HIV+ (IgE test; n=35)133316Correct HIV− (IgE test; n=41)141377Specificity (95% CI)0·93 (0·66–0·99)1·00 (0·75–1·00)1·00 (0·75–1·00)1·00 (0·75–1·00)Sensitivity (95% CI)0·93 (0·66–0·99)1·00 (0·75–1·00)1·00 (0·75–1·00)1·00 (0·75–1·00)Positive predictive value (95% CI)0·93 (0·66–0·99)1·00 (0·29–1·00)1·00 (0·29–1·00)1·00 (0·79–1·00)Negative predictive value (95% CI)0·93 (0·68–0·99)1·00 (0·75–1·00)1·00 (0·59–1·00)1·00 (0·59–1·00)* Group 1 included 24 children <3 months of age when first tested; 12 children were 0–1 month and 12 children were 2–3 months of age;† On the basis of viral cultures or HIV ELISA and Western blot. Open table in a new tab This small study shows that IgE-specific antibodies to HIV-1 may be used for diagnosis: the IgE assay is sensitive and specific in children of various ages, including neonates, and may be more sensitive than IgA assays.1Weiblen BJ Lee FK Cooper ER et al.Early diagnosis of HIV infection in infants by detection of IgA HIV antibodies.Lancet. 1990; 335: 988-990Summary PubMed Scopus (98) Google Scholar, 2Livingston A Hutton N Halsey N Kline R Joyner M Quinn T Human immunodeficiency virus-specific IgA in infants born to human immunodeficiency virus infected women.Arch Pediatr Adolesc Med. 1995; 149: 503-507Crossref PubMed Scopus (10) Google Scholar, 3Landesman S Weinblein B Mendez H et al.Clinical utility of HIV-IgA immunoblot assay in the early diagnosis of perinatal HIV infection.JAMA. 1991; 266: 3443-3446Crossref PubMed Scopus (60) Google Scholar, 4Quinn TC Kline RI Halsey N et al.Early diagnosis of perinatal HIV infection by detection of viral specific IgA antibodies.JAMA. 1991; 266: 3439-3442Crossref PubMed Scopus (70) Google Scholar IgE is produced early in the fetus,5Bierman C Pearlman D Allergic diseases from infancy and adulthood. WB Saunders, Philadelphia1988: 1-19Google Scholar leading to high IgE concentrations in those infants infected in utero. Since IgE does not cross the placenta barrier, detection of IgE specific for HIV-1 at delivery suggests fetal IgE synthesis. IgE may also be produced earlier than IgA in response to infection in infants infected at delivery. Assays that are sensitive and specific to detect HIV-1 infection in infants are generally unavailable but are important in developing countries where PCR and viral culture may not be available, and may be economically advantageous in industrialised countries. This study was supported by NIMH 1-P50-MH42555, Fogarty International Training Grant D43-TW00017-5, and NIAID grants AI2352 and AI27560.