Anti-human immunodeficiency virus type 1 (Anti-HIV-1) antibody response was compared in four groups of mice following inoculation with HIV-1 gp160, with live recombinant vaccinia virus expressing HIV-1 envelope glycoproteins, or with both immunogens in alternate orders for primary or secondary immunizations. Both subunit and recombinant virus immunogens induced similar levels of antibody response following primary immunization. However, after secondary immunization, mice primed with live recombinant virus and then boosted with subunit gp160 immunogen showed significantly higher antibody response than those in the other three groups. Neutralizing antibodies were generated only in this group of mice and were shown to neutralize both the homologous virus (BRU) and a divergent isolate (SF2) of HIV-1. On the other hand, their reactivities to peptide sequences from the principal neutralizing determinant (PND) of gp120 were limited to the BRU isolate, not SF2 or MN, indicating that the cross-neutralizing activities were directed against determinants other than the linear epitope(s) within the PND. These results also indicate that combined immunization by priming with liver recombinant virus and boosting with subunit immunogen may be more effective than immunization by either immunogen alone.

A rapid procedure for the inactivation of HIV-1-infected cells using psoralen and ultraviolet (UV) light is described. Exposure of HIV-1-infected cells to 5 micrograms/ml psoralen followed by UV irradiation (320-380 nm) for 5 minutes yields cells that are noninfectious as assessed by extended infectivity assays. The psoralen/UV inactivation procedure described is effective with cells chronically or acutely infected with HIV-1 and is unaffected by cell densities up to 12 x 10(6)/ml. At 5 micrograms/ml psoralen does little damage to cellular permeability as shown by the ability of treated cells to exclude trypan blue and propidium iodide. Psoralen/UV treatment of HIV-1-infected cells does not cause a significant decrease in the reactivity of HIV-1 core and envelope antigens or cellular antigens to monoclonal antibodies. Experiments are presented demonstrating the use of these cells for flow cytometry studies and for cell surface labeling using the lactoperoxidase 125I iodination procedure.