Active Immunization of HIV-1 Infected, Pregnant Women With CD4 Lymphocyte Counts >= 400/mm3: A Phase I Study of Safety and Immunogenicity of MN rgp120/HIV-1 Vaccine (NOTE: Some Patients Receive Placebo)

To evaluate the safety of rgp120/HIV-1MN vaccine in HIV-1 infected pregnant women with CD4 counts \>= 400 cells/mm3. To evaluate the immunogenicity of this vaccine in pregnant women and the passive acquisition of vaccine-specific antibody in their infants. To evaluate the induction or augmentation by rgp120/HIV-1MN vaccine of mucosal immune response in the gastrointestinal and reproductive tracts during pregnancy. To isolate and genetically characterize the HIV-1 present in cervicovaginal fluid specimens of pregnant women and compare it to that present in their peripheral blood mononuclear cells and to that of their infected infants. Evidence suggests that an advanced stage of disease with high plasma viremia is associated with increased transmission of HIV-1 to the fetus. Slowing the progression of disease, reducing the titer of virus in plasma, and increasing the titer of epitope-specific antibody are potentially attainable goals through active immunization of the mother during pregnancy.