Reactivity to gag- and env-related proteins in immunoblot assay is not necessarily indicative of HIV infection

Is a positive western blot proof of HIV infection?

It is currently accepted that a positive Western blot (WB) HIV antibody test is synonymous with HIV infection and the attendant risk of developing AIDS. In this communication we present a critical evaluation of the presently available data on HIV isolation and antibody testing. This evidence indicates that: (1) the antibody tests are not standardized; (2) the antibody tests are not reproducible; (3) the WB proteins (bands) which are considered to be encoded by the HIV genome and to be specific to HIV may not be encoded by the HIV genome and may in fact represent normal cellular proteins; (4) even if the proteins are specific to HIV, because no gold standard has been used to determine specificity, a positive WB may represent nothing more than cross-reactivity with non-HIV antibodies present in AIDS patients and those at risk. We conclude that the use of antibody tests as a diagnostic and epidemiological tool for HIV infection needs to be reappraised.

Characterization of serum antibody responses to recombinant HIV-1 gp160 vaccine by enzyme immunoassay. NIAID AIDS Vaccine Clinical Trials Network

An enzyme immunoassay (EIA) was developed to measure serum antibody responses of healthy adult volunteers vaccinated with 40 or 80 micrograms of human immunodeficiency virus type 1 (HIV-1) recombinant gp160 (rgp160) vaccine at 0, 1, 6, and 18 months. This assay, which used purified rgp160 as antigen, was compared with the Biotech/Du Pont HIV-1 Western blot and the Abbott HIV-1 EIA. Of 33 volunteers who received three doses of rgp160 vaccine, seroresponses were detected in 91% by rgp160 EIA, 97% by Western blot, and 30% by HIV-1 EIA. The level of IgG rgp160 EIA antibody (mainly IgG1) peaked after the third immunization; 64% of 33 vaccinees still had detectable antibody by 12 months. The fourth immunization induced anamnestic IgG EIA antibody in 23 of 24 vaccinees, with titers ranging from 1:200 to 1:25,600. Neutralizing antibody was not detected in postvaccination sera by microtiter syncytium formation inhibition assay. Additional testing of sera by EIA indicated that the immune response to the vaccine was directed toward epitopes on both gp120 and gp41. Seroresponses to the immunodominant epitopes on gp41 were infrequent and none were detected to the neutralization epitope in the V3 region of gp120. This highly sensitive EIA is useful for characterizing HIV-1-specific antibody responses induced by an HIV-1 gp160 subunit vaccine.