HIV Type 1-Specific IgE in Serum of Long-Term Surviving Children Inhibits HIV Type 1 Production in Vitro

Abstract

We previously identified a group of long-term pediatric survivors who had acquired HIV-1 through maternal transmission; had not received antiretroviral therapy; are now >8 years old, in good health, and with no opportunistic infections; and have not failed to thrive, although they have greatly decreased numbers of blood CD4⁺ T cells (<500/mm³). All the children have elevated total serum IgE levels (210-2475 IU/ml) and make anti-HIV-1 IgE or IgE directed against non-HIV-1 specificities (radioimmunoassay, Western blot assay); they have no detectable antigenemia. We have now studied the ability of anti-HIV-1 IgE in serum obtained from these children to regulate (1) production of HIV-1 by interleukin 2/phytohemagglutinin (IL-2/PHA)-stimulated peripheral blood mononuclear cells (PBMCs) taken from HIV-1-seronegative donors and infected with a T cell-tropic clone of HIV-1, and (2) transmission of a primary HIV-1 strain from adult AIDS patients to uninfected IL-2/PHA-stimulated PBMCs (p24 core antigen production). High levels of HIV-1 production were observed when PBMCs were cultured for 5 days in the presence of HIV-1-seronegative donor serum that was either IgE positive or IgE negative(IgE, >100 or <100 IU/ml, respectively). HIV-1 production also was observed when PBMCs were cultured with HIV-1-infected donor serum that either contained IgE directed against non-HIV-1 specificities or was IgE negative; these levels were 40% less than those seen with sera from the HIV-1-seronegative donors. Far greater inhibition of virus production was observed if the serum in culture contained anti-HIV-1 IgE (>95%). Virus neutralization did not appear to account for the inhibition obtained with anti-HIV-1 IgE-containing serum because virus production was not suppressed in cultures to which serum was added immediately preinfection (<10%), but was strongly suppressed when serum was added 1.5 hr postinfection (>95%). The inhibition of virus production obtained with serum containing anti-HIV-1 IgE was reversed when (1) serum was depleted of IgE (immunoaffinity), but not when it was depleted of IgG (protein G-Sepharose) before inclusion in culture postinfection, (2) anti-IgE, but not anti-IgG, was included in culture, or (3) serum was heat treated before culture. The results indicate that serum from certain HIV-1-infected pediatric long-term survivors contains agents that inhibit HIV-1 productionin vitro, and that these agents include anti-HIV-1 IgE. They suggest that a cytotoxic event, rather than virus neutralization, plays an important role in anti-HIV-1 IgE-mediated inhibition of virus production.