Takako Hayashi

Evaluation of a New Screening Assay Kit for The Combined Detection of HIV p24 Antigen and Antibody

DUO is an automated HIV infection screening test kit based on the combined detection of p24 Ag and anti-HIV-1 and anti-HIV-2 IgG in human sera or plasma using the ELFA technique (Enzyme-Linked Fluorescent Assay). The performance of DUO was compared with that of HIV-1/HIV-2 3rd generation EIA plus and particle agglutination (PA) test. A total of 141 seropositive sera, 3 seroconversion panels, 300 seronegative sera and 387 potentially cross-reactive serum samples were tested. One hundred and forty one seropositive sera in Japan and Cameroon were all positive with DUO. Three seroconversion panels (panel Q, Z, AE) were tested to evaluate sensitivity. In Panel Q, infecution was detected seven days earlier with DUO than with the 3rd generation EIA plus and PA. In Panel AE, infection was detected four days earlier with DUO than with the single antibody assays. Three hundred seronegative sera from Kanagawa prefectural public health centers were all negative with DUO as well as PA test. Three hundred and eighty seven potentially cross-reacting samples were tested to challenge the specificity of the assay. These included samples from pregnant women and hepatitis patients. In four of the 204 samples from pregnant women, false-positive results were observed with DUO. In three of the 183 samples from hepatitis patients, false-positive results were also obtained with DUO. All samples of 7 DUO positive results were negative with western blot test. Five of them were negative with RT-PCR and 2 of them were not tested because there were not enough samples. Thirty cross-reacting (false-positive) samples by PA test from blood donors were tested by DUO, and all of these were negative by DUO.

Kinetic Analysis of Anti-HIV Titer in Early Stage of HIV Infection

We analyzed the anti-HIV antibody titer by particle agglutination (PA) on 11 HIV seroconversion panels. PA titer increased very rapidly and the titer went up to 1,000 or more within 18.2 days after seroconversion. The results suggest that one to two weeks of duration will be enough to differentiate persons at the early stage of HIV infection from individuals with HIV screening test initially reactive but false positive. In Japan, HIV prevalence is very low and the majority of the HIV screening test-positive (reactive) cases turned out to be false positive. This HIV testing strategy (one to two weeks interval bleeding) will be very practical and useful to differentiate early stage of HIV infection cases from the majority of false positive cases.

[Investigation of AZT susceptibility of sequential HIV-1 isolates from patients treated with ddI after long-term therapy with AZT].

AZT susceptibility of sequential 12 HIV-1 isolates was investigated by culture method. These isolate were obtained from three patients who had received AZT for at least 12 months and switched to ddI after they appeared to deteriorate clinically. Cultures of isolate from a patient before therapy with AZT or ddI did not show cytopathic effect (CPE) in the presence of 0.1 microM or 1.0 microM AZT. Culture of 2 isolates from two patients treated with AZT more than 6 months before switched to ddI therapy showed CPE in the presence of AZT and HIV-1 p24 antigen was detected by ELISA in the supernatants. Culture of 6 of 7 isolates from three patients treated with ddI after long-term therapy with AZT also showed CPE in the presence of 1.0 microM AZT and HIV-1 p24 antigen was detected. These results demonstrated that AZT-resistant variant was still a dominant population in the isolate from patients after 11 to 13 months of discontinuing AZT therapy.