SERUM IGA-MEDIATED NEUTRALIZATION OF HIV TYPE-1

The sera of 33 HIV-1-infected individuals, previously shown to neutral ize HIV-1(MN) in vitro, were screened by ELISA for IgA reactivity agai nst rgpl20(MN) and a synthetic V3(MN) loop peptide. Six were selected for evaluation of the effect of serum IgA from infected individuals on the in vitro infection of susceptible target cells by HIV-1(MN). By u sing protein C immobilized on Sepharose, we depleted the sera of Ige t o a level undetectable by nephelometry and viral envelope-specific ELI SA. The IgA component of the IgG-depleted serum was affinity purified with immobilized jacalin, a lectin that selectively binds the IgA1 fra ction of human Ig. Igc-depleted sera and purified IgA1 serum fractions showing IgA reactivity against rgp120(MN) and V3(MN) by ELISA inhibit ed the in vitro infection of CEM-ss cells by HIV-1(MN), but sera deple ted of both IgG and IgA1 did not. These data show that, like serum IgG , serum IgA from selected HIV-1-infected individuals is capable of neu tralizing HIV-1(MN) in vitro. The biologic significance of this observ ation and the identities of serum IgA-recognized HIV-1 neutralization epitopes remain to be determined.