[Free dissociated and precipitated p24 antigenemia of HIV-1 in subjects of the black race]. / Antigénémie p24 du VIH de type 1, libre, dissociée et précipitée, chez les individus de race noire.

P24/HIV-1 antigen in the sera from 41 HIV-1-infected Black individuals, living in the Central African Republic (n = 17) and in France (n = 24), and in 21 HIV-1-infected Caucasians patients, matched on the stages of the disease, has been detected and quantified by ELISA, without and with acid pretreatment of the sera by HC1 or by glycine, and after ultracentrifugation of serum. Free p24 antigenemia was detected less frequently in Black patients (9.7%), than in Caucasian controls (33%) (p < 0.05). Decomplexed p24 antigenemia was detected in 34% of patients after dissociation of circulating immune complexes (CIC) by HC1 (p < 0.01) and in 44% of patients after dissociation of CIC by glycine (p < 0.001). However, the mean concentration of decomplexed p24 antigenemia of positive sera was higher after pretreatment by HC1 (88 pg/ml) than by glycine (52 pg/ml), suggesting that a strong acid is more convenient than a weak one to disrupt the CIC in Black individuals. After ultracentrifugation of the serum, the detection of p24 antigen was not significantly increased. Acid dissociation of CIC is a usefull method to increase the sensitivity of detection of circulating p24 antigen in HIV-1-infected Black individuals.

Detection of antibodies to human immunodeficiency virus in vaginal secretions by immunoglobulin G antibody capture enzyme-linked immunosorbent assay: application to detection of seminal antibodies after sexual intercourse.

In order to evaluate a commercial immunoglobulin G (IgG) antibody capture enzyme-linked immunoassay (ELISA) (Wellcozyme HIV1 + 2 Gacelisa; Murex Diagnostics Limited, Dartford, United Kingdom) for the detection of antibodies to human immunodeficiency virus (HIV) in vaginal secretion samples (VS) from HIV-seropositive and -seronegative women, serum samples (S) and VS were obtained from 129 African women living in the Central African Republic, a country of high HIV prevalence. Sera were tested for HIV by routine second-generation ELISA with confirmatory Western blot (immunoblot) (WB). By the Gacelisa IgG immuno-capture assay, 45 VS were positive and 84 were negative, whereas by WB, 44 VS were confirmed positive and 85 were confirmed negative. Considering WB as a reference, the IgG immunocapture assay in VS was 97.7% sensitive (43 of 44 positive samples) and 97.6% specific (83 of 85 negative samples). Of 42 HIV-seropositive women, 41 (97.6%) had S and VS that both were HIV positive (S+ VS+), and of 87 HIV-seronegative women, 83 (95.4%) had S and VS that both were HIV negative (S- VS-). Five women had discordant results for S and VS. One (S+ VS-) possibly had a false-negative VS result. Two (S- VS+) had similar indeterminate patterns for S and VS in WB. Two (S- VS+) had a typical HIV-positive pattern on WB of VS, whereas S results in WB were indeterminate in one case and negative in the other case; for both women, detection of prostatic acid-phosphatase was positive in VS, strongly suggesting recent sexual intercourse with an HIV-positive man. Because all HIV-infected men have detectable IgG antibodies to HIV in the seminal fluid, an HIV-seronegative rape victim with HIV-positive VS (S- VS+) should receive short-term antiviral therapy to prevent possible HIV transmission.

Free and decomplexed human immunodeficiency virus p24 antigenaemia in black patients with AIDS and AIDS-related disorders.

OBJECTIVES: To determine the clinical signification of free and decomplexed p24 antigenaemia in HIV1-infected black individuals. PATIENTS AND METHODS: Sixty African patients with pre-AIDS (n = 12) and AIDS (n = 48), hospitalized in the Centre National Hospitalier Universitaire de Bangui, Central African Republic, were prospectively included. 15 HIV1-seronegative healthy African subjects served as controls. Serum p24 antigenaemia was detected using a polyclonal and a monoclonal sandwich enzyme immunoassay (EIA). All sera were tested again after acid pretreatment (45 mn incubation of serum with a 0.5 N solution of HCl at +37 degrees C). RESULTS: The polyclonal EIA and the monoclonal EIA detected respectively four (7%) to six (10%) free p24 antigen positive samples from the HIV1-infected individuals, with a similar frequency in pre-AIDS and AIDS patients. None of the controls were found p24 antigen positive. After acid pretreatment, the rate of detectable p24 antigenaemia increased significantly, leading with the monoclonal EIA to a 47% positivity rate (p < 0.001), and the patients with AIDS became more frequently p24 antigen positive (54%), than the patients with pre-AIDS (17%) (p = 0.02). CONCLUSION: Detectable p24 antigenaemia in HIV1-infected African subjects could be obtained in nearly half of cases by increasing the sensitivity of the assay using monoclonal EIA and acid hydrolysis of circulating immune complexes. Decomplexed p24 antigenaemia in HIV1-infected Black African patients could have predictive signification similar to free p24 antigenaemia in Caucasians.

[Alternative strategy for the diagnosis of HIV infection in sub-saharan Africa. Value of the sequential combination of the ELISA test and a 2nd generation rapid test]. / Stratégie alternative pour le diagnostic de l'infection par le VIH en Afrique subsaharienne. Intérêt de la combinaison séquentielle d'un test ELISA et d'un test rapide de 2e génération.

The "conventional" algorithm for HIV testing based on the confirmation of all positive anti-HIV screening reactions by Western blot requires sufficient laboratory facilities and is expensive, that limits its use in developing countries, such as in subsaharian Africa. The apparition of second and third generation screening ELISA which are very sensitive and specific, as well as the development of rapid tests which are simple, visually read, and sufficiently sensitive and specific, has permitted the design of "alternative" strategy for HIV testing utilizing the association of 2 ELISA and/or rapid tests, in order to limit the use of a confirmatory assay. Alternative strategies are less expensive, yield generally very high sensitivity and specificity, and have proved to be valuable for African countries. In this study, 5 alternative strategies, using different associations of two second generation screening tests, one classical ELISA (Genelavia mixt) and one rapid test (Test PACK HIV-1/HIV-2 AB) have been retrospectively evaluated in the field in Bangui, Central African Republic, with a panel of 130 sera (prevalence of HIV infection: 42.7%). The strategy using two sequential screening tests (Test Pack HIV-1/HIV-2 AB following by Genelavia mixt) with the confirmation of discordant results by Western blot permitted to diagnose HIV-1 infection in Bangui with a sensitivity, a specificity and a positive predictive value of 100%, and to reduce the cost of more than 50% in comparison with the conventional strategy. Such an alternative strategy could be useful for the individual notification of HIV serology in Bangui.