title: Performance of a modified HIV-1 p24 antigen assay for early diagnosis of HIV-1 infection in infants and prediction of mother-to-infant transmission of HIV-1 in Dar es Salaam, Tanzania.
abstract: The aim of this study was to determine the utility of an amplified human immunodeficiency virus type 1 (HIV-1) p24 antigen (ag) assay using heated plasma or serum samples for the early diagnosis of HIV-1 infection in infants and for the prediction of the risk of mother-to-infant (MTI) transmission of HIV-1 in Dar es Salaam, Tanzania. The study included 125 samples from 76 infants positive for HIV-1 DNA by the polymerase chain reaction (PCR), 106 samples from 101 PCR-negative infants and 116 and 160 samples from seropositive and seronegative mothers, respectively. Samples were boiled to dissociate immune complexes and tested for HIV-1 p24 ag using a p24 ag amplification assay. Reactive samples were confirmed by a neutralization assay. Altogether, 123 of 125 samples from 76 PCR-positive infants were positive for p24 ag (sensitivity = 98.7%). HIV-1 p24 ag was found in all 18 samples collected at 1-8 weeks, in 35 of 36 samples collected at 9-26 weeks, in all 40 samples collected at 27-52 weeks, and in 30 of 31 samples collected > 52 weeks after birth. Detection of HIV-1 p24 ag was significantly more common in transmitting mothers (12 of 29, 41.4%) than in nontransmitting mothers (nine of 87, 10.3%) (p < 0.001). Among mothers with p24 antigenemia, the vertical transmission rate was significantly higher (12 of 21, 57%) than in mothers without p24 antigenemia (17 of 95, 18%) (p < 0.001). All samples from 101 PCR-negative children and 160 seronegative mothers were negative for p24 ag (specificity = 100%). We conclude that using heated plasma or serum increases the sensitivity of the p24 ag assay significantly. This modified simple test may be sufficient for the early diagnosis of HIV-1 infection in infants in settings with limited laboratory facilities. It is also useful for prediction of the risk of MTI transmission of HIV-1.
authors.affiliation: Department of Microbiology/Immunology, Muhimbili University College of Health Sciences, Dar es Salaam, Tanzania.
authors.forename: E
authors.initials: E
authors.lastname: Lyamuya
authors.forename: U
authors.initials: U
authors.lastname: Bredberg-Rådén
authors.forename: A
authors.initials: A
authors.lastname: Massawe
authors.forename: E
authors.initials: E
authors.lastname: Urassa
authors.forename: G
authors.initials: G
authors.lastname: Kawo
authors.forename: G
authors.initials: G
authors.lastname: Msemo
authors.forename: T
authors.initials: T
authors.lastname: Kazimoto
authors.forename: A
authors.initials: A
authors.lastname: Ostborn
authors.forename: K
authors.initials: K
authors.lastname: Karlsson
authors.forename: F
authors.initials: F
authors.lastname: Mhalu
authors.forename: G
authors.initials: G
authors.lastname: Biberfeld
mesh_terms: D015415:Biomarkers / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005500:Follow-Up Studies; D015483:HIV Antibodies / Q000097:blood; D016655:HIV Core Protein p24 / Q000097:blood*; D015658:HIV Infections / Q000097:blood / Q000175:diagnosis* / Q000635:transmission; D015497:HIV-1 / Q000276:immunology*; D006358:Hot Temperature; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D018445:Infectious Disease Transmission, Vertical; D012680:Sensitivity and Specificity; D013636:Tanzania
chemical_list: D015415:Biomarkers; D015483:HIV Antibodies; D016655:HIV Core Protein p24