Immunogenic properties of structurally modified human tissue plasminogen activators in chimpanzees and mice.

Immunogenic properties of second generation human tissue plasminogen activator (tPA) derivatives were examined in chimpanzee and mouse systems. Five species of modified tPAs (mtPAs) (designated 2660, 2663, 2810, 8000, and 9200), recombinant native tPA or bovine serum albumin (BSA) as a positive control were subcutaneously injected nine times at suitable intervals into chimpanzees, genetically the closest species to man. These animals were tested for antigen(Ag)-specific antibodies to the corresponding proteins by means of enzyme-linked immunosorbent assay and Western blot analysis. Neither 9200, one of the five mtPAs tested, nor tPA was immunogenic, although BSA and the other four mtPAs were immunogenic under these conditions. Thus, an antigenic determinant was not exposed by the modification on 9200 and this modified tPA is expected not to be immunogenic in humans. In the mouse studies, mice were immunized with mtPAs. Serum samples from these animals were tested for antibodies to the mtPAs which did not concomitantly recognize native tPA by immune adsorption of the antibodies to tPA. The amount of such antibodies after the elimination of native tPA-reactive antibodies was little or none when the serum samples from 9200 and from the other mtPAs, except 8000, were tested. Taking into consideration the results of the chimpanzee studies, it can be concluded that Ag-specific antibodies are dominantly produced to unchanged epitopes present in modified proteins in the mouse system, in which the native protein is immunogenic.(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphocyte and neutrophil dysfunction associated with hepatitis B virus and hepatitis non-A, non-B virus infection in the chimpanzee.

Chimpanzees were examined for the effect of viral hepatitis infections on specific and nonspecific immune response mechanisms. The data suggest that infection with either hepatitis B virus or hepatitis non-A, non-B virus may result in suppression of cellular immune response components. Mitogen-induced lymphocyte proliferation was lower in virus-infected chimpanzees than in naive animals. Neutrophils from virus infected animals exhibited decreased or altered chemiluminescence kinetics.

Challenge of chimpanzees (Pan troglodytes) immunized with human immunodeficiency virus envelope glycoprotein gp120.

The human immunodeficiency virus type 1 (HIV-1), the causative agent of acquired immunodeficiency syndrome, infects humans and chimpanzees. To determine the efficacy of immunization for preventing infection, chimpanzees were immunized with gp120 purified from human T-cell lymphotrophic virus type IIIB (HTLV-IIIB)-infected cell membranes and challenged with the homologous virus, HTLV-IIIB. A challenge stock of HTLV-IIIB was prepared by using unconcentrated HTLV-IIIB produced in H9 cells. The titer of the virus from this stock on human and chimpanzee peripheral blood mononuclear cells and in human lymphoid cell lines was determined; a cell culture infectivity of 10(4) was assigned. All chimpanzees inoculated intravenously with 40 cell culture infectious units or more became infected, as demonstrated by virus isolation and seroconversion. One of two chimpanzees inoculated with 4 cell culture infectious units became infected. Chimpanzees immunized with gp120 formulated in alum developed antibodies which precipitated gp120 and neutralized HTLV-IIIB. Peripheral blood mononuclear cells from gp120-vaccinated and HIV-infected animals showed a significantly greater response in proliferation assays with HIV proteins than did peripheral blood mononuclear cells from nonvaccinated and non-HIV-infected chimpanzees. Two of the gp120-alum-immunized chimpanzees were challenged with virus from the HTLV-IIIB stock. One animal received 400 cell culture infectious units, and one received 40 infectious units. Both animals became infected with HIV, indicating that the immune response elicited by immunization with gp120 formulated in alum was not effective in preventing infection with HIV-1.

Polymorphonuclear leukocyte function in HIV-1-infected chimpanzees.

The chemiluminescent characteristics of enriched populations of neutrophils from control and HIV-infected chimpanzees were assessed. Neutrophils from HIV-infected chimpanzees were suppressed in their ability to generate a normal response to particulate and soluble stimuli when compared to normal and hepatitis non-A, non B-infected controls. Particulate (latex beads) stimulation of neutrophils resulted in an aberrant response when contrasted with controls. Normal control responses were characteristically biphasic while the response from hepatitis NANB HIV-infected chimpanzees was not biphasic. Neutrophils challenged with a soluble (phorbol ester) stimulant also demonstrated a suppressed response. These data suggest that HIV infection has an additive suppressive effect on neutrophil function in chimpanzees previously infected with hepatitis NANB. The suppression of chimpanzee neutrophil function following HIV infection is similar to that seen in other non-primate viral and retroviral infections.

Purified envelope glycoproteins from human immunodeficiency virus type 1 variants induce individual, type-specific neutralizing antibodies.

Repeated immunizations of goats, horses, or chimpanzees with envelope glycoprotein gp120 isolated from human immunodeficiency virus type 1 (HIV-1) resulted in type-specific neutralizing-antibody responses, which began to decay approximately 20 days following the administration of antigen. This was true repeatedly for serum samples from animals hyperimmunized with gp120s from either the HTLV-IIIB (IIIB) or the envelope-divergent HTLV-IIIRF (RF) HIV-1 isolates. Animals previously immunized with the IIIB gp120 were then inoculated with purified RF gp120. The first response in these animals was an anamnestic resurgence of neutralizing antibody to IIIB without detectable neutralizing antibody for RF. However, with later RF gp120 boosts, the IIIB neutralizing-antibody titers fell and an RF type-specific neutralizing-antibody response developed. When assessed with other HIV-1 variants, no group-specific neutralizing antibody was seen in any of the vaccination protocols evaluated. These results will pose real obstacles in the development of an effective vaccine for HIV.

Serological responses in chimpanzees inoculated with human immunodeficiency virus glycoprotein (gp120) subunit vaccine.

The major envelope glycoprotein of a human immunodeficiency virus (HIV) has been purified and was utilized as a prototype vaccine in chimpanzees. The 120,000-dalton glycoprotein (gp120) was purified from membranes of human T-lymphotropic virus (HTLV)-IIIB-infected cells and the final preparation contained low levels to no detectable HTLV-IIIB core antigen (p24) and low levels of endotoxin. Chimpanzees inoculated with gp120 responded by developing antibodies that precipitated radiolabeled gp120 and neutralized in vitro infection of HTLV-IIIB. Antibodies to HTLV-IIIB p24 were not detected in the gp120-immunized chimpanzees. Peripheral blood leukocytes from the vaccinated animals were examined for T4+ and T8+ cells, and no decrease in the T4/T8 ratio was found, indicating that immunization with a ligand (gp120) that binds to T4 has no detectable adverse effect on the population of T4+ cells. The only current animal model that can be reproducibly infected with HIV is the chimpanzee. Immunization of chimpanzees with HIV proteins will provide an experimental system for testing the effectiveness of prototype vaccines for preventing HIV infection in vivo.